No functional benefit of larger femoral heads and alternative bearings at 6 months following primary hip replacement

MethodsWe examined the influence of these variables on patient-reported outcome measures (PROMs) for a consecutive series of primary hip replacements using National Joint Registry (NJR) and PROMs-linked data. To minimize the confounding influence of implant design factors, the single most commonly used brand in England and Wales (DePuy Corail Pinnacle) was examined. Improvement in patient hip-specific outcomes (Oxford hip score, OHS), general health outcomes (Euroqol, EQ-5D), and rates of self-reported complications (bleeding, wound problems, re-admission, and reoperation) were compared for different head sizes (28-mm, 32-mm, and 36-mm) and bearings (metal-on-polyethylene (MoP), ceramic-on-polyethylene (CoP), and ceramic-on-ceramic (CoC)), adjusting for differences in case mix.ResultsAt a mean follow-up of 7 months, improvements in OHS and EQ5D index were similar for 28-mm and 36-mm heads. A 32-mm head was associated with poorer function (OHS: 20, 99% CI: 19–21, p = 0.002; EQ5D index: 0.39, 99% CI: 0.36–0.42, p = 0.004), although these small differences may not be of clinical importance. There were no statistically significant benefits of either CoP or CoC bearings compared to a MoP bearing. Complication rates were similar within comparisons of head sizes or bearings.InterpretationIn this short-term study, we did not find any functional benefits of larger head sizes or alternative bearings, after adjusting for other influences. We question their use in routine primary hip replacement given the lack of evidence of improved long-term survival in the literature.Greater femoral head size may improve function and enhance stability after primary total hip replacement (THR) (Bartz et al. 2000, Cuckler et al. 2004, Hummel et al. 2009). Previous studies have shown a greater range of movement with increasing head size (Amstutz et al. 1975, Matsushita et al. 2009). Use of a larger head size is an attractive option in younger patients who require stability at higher levels of function, and in older patients in order to reduce dislocation risk. However, greater surface area may also increase wear rates, irrespective of bearing materials (Charnley et al. 1969, Dowling et al. 1978, Livermore et al. 1990, Bragdon et al. 2013, Jack et al. 2013), and there have been reports of excessive taper load with large-diameter bearings (Langton et al. 2012, Meyer et al. 2012). Larger heads have been associated with the use of alternative bearings, in order to reduce wear and improve implant longevity. The National Joint Registry (NJR) in England and Wales has described an increase in the use of larger femoral head sizes (over 28 mm)—from 5% to 50% between 2005 and 2010 (England and Wales National Joint Registry 2012). Over the same period, the use of ceramic-on-polyethylene (CoP) and ceramic-on-ceramic (CoC) bearings has increased.Medium-term revision rates are higher with CoC bearings than with metal-on-polyethylene (MoP) bearings generally, across registry data, and specifically, when the most commonly used implant in England and Wales (Corail stem/Pinnacle cup; DePuy Ltd., Leeds, UK) was analyzed (Sexton et al. 2009, Jameson et al. 2013). Larger femoral sizes using hard-bearing technology did not give any functional improvement over 28-mm MoP (Hanna et al. 2012) in a small randomized trial, and larger head sizes have not been found to offer any gait-related benefits (Zagra et al. 2013). The functional benefits of increasing head size and alternative bearings have yet to fully assessed.Patient-reported outcome measures (PROMs) supplement revision risk in the assessment of success after joint replacement (Devlin et al. 2010). PROMs are routinely collected on National Health Service (NHS) patients undergoing THR in England. Data on hip replacement patients, their surgeons, and the implants used are collected by the NJR. These datasets can be linked in order to compare early outcomes for specific patient and implant groups at the national level. The present analysis explored the effect of bearing surface and femoral head size on PROMs and complications following THR. We hypothesized that larger heads and alternative bearings would have no functional benefit over standard (28-mm MoP) bearings.     

Changes in blood ion levels after removal of metal-on-metal hip replacements: 16 patients followed for 0–12 months

Background and purpose

In patients with metal-on-metal (MoM) hip prostheses, pain and joint effusions may be associated with elevated blood levels of cobalt and chromium ions. Since little is known about the kinetics of metal ion clearance from the body and the rate of resolution of elevated blood ion levels, we examined the time course of cobalt and chromium ion levels after revision of MoM hip replacements.

Patients and methods

We included 16 patients (13 female) who underwent revision of a painful MoM hip (large diameter, modern bearing) without fracture or infection, and who had a minimum of 4 blood metal ion measurements over an average period of 6.1 (0–12) months after revision.

Results

Average blood ion concentrations at the time of revision were 22 ppb for chromium and 43 ppb for cobalt. The change in ion levels after revision surgery varied extensively between patients. In many cases, over the second and third months after revision surgery ion levels decreased to 50% of the values measured at revision. Decay of chromium levels occurred more slowly than decay of cobalt levels, with a 9% lag in return to normal levels. The rate of decay of both metals followed second-order (exponential) kinetics more closely than first-order (linear) kinetics.

Interpretation

The elimination of cobalt and chromium from the blood of patients who have undergone revision of painful MoM hip arthroplasties follows an exponential decay curve with a half-life of approximately 50 days. Elevated blood levels of cobalt and chromium ions can persist for at least 1 year after revision, especially in patients with high levels of exposure.After a dramatic rise in initial popularity, the use of metal-on-metal (MoM) hip arthroplasties has declined precipitously, both in hip resurfacings and conventional hip replacement, due to an alarming incidence of adverse inflammatory reactions (van der Weegen et al. 2011, NJR 2012).There are now serious concerns about potential adverse biological effects, both local and systemic, arising from wear debris generated by MoM articulations (Matthies et al. 2011). The nano-scale particles generated through wear of MoM bearings can enter the reticulo-endothelial system and cross over into the circulation as early as 5 days after implantation (Daniel et al. 2007). The specific surface area (surface area to mass ratio) of these particles makes them susceptible to corrosion in vivo (Hart et al. 2010), leading to elevated levels of cobalt and chromium ions in the blood, usually ranging from 5 to 10 times normal values (Jacobs et al. 1996, Brodner et al. 1997, Skipor et al. 2002, Dunstan et al. 2005, Daniel et al. 2009, Hart et al. 2009, van der Weegen et al. 2011). Possible complications from long-term elevated metal ion levels include immune reactions (Pandit et al. 2008), necrosis (Campbell et al. 2010), toxicity (Keegan et al. 2007, Tower et al. 2010, Corradi et al. 2011), chromosomal aberrations (Ladon et al. 2004), and carcinogenicity (Case et al. 1994). However, the most common short-term complication is joint pain associated with inflammatory reactions (Milosev et al. 2005). In many cases where there is pain with soft-tissue masses, often in association with elevated levels of cobalt and chromium ions, removal of the implanted components is necessary. This form of failure is more common in female patients than in male patients, and it has been reported in 1–20% of cases at 5 years (Schmidt et al. 1996) depending on the design of the prosthesis.Although revision is performed in the hope that the elevation of ion levels and symptoms will resolve, little is known about the kinetics of storage and turnover of these ions in the body. We examined the kinetics of cobalt and chromium ion decay after revision of MoM hip replacements. Our principal goals were to characterize the decay curves of cobalt and chromium ions after revision procedures and to determine when blood concentrations return to levels below the MHRA action level of 7 ppb, in order to determine exposure risk (MHRA 2010). We hypothesized that: (1) removal of MoM components results in a rapid drop in the level of metal ions in the blood followed by a slow steady-state decline; (2) chromium concentrations will decrease more slowly than cobalt concentrations; (3) the total body exposure to ions is orders of magnitude higher with poorly functioning or loose implants than with well-functioning components.     

Risk factors for revision due to infection after primary total hip arthroplasty: A population-based study of 80,756 primary procedures in the Danish Hip Arthroplasty Registry

Background and purpose

There has been a limited amount of research on risk factors for revision due to infection following total hip arthroplasty (THA), probably due to low absolute numbers of revisions. We therefore studied patient- and surgery-related risk factors for revision due to infection after primary THA in a population-based setting.

Materials and methods

Using the Danish Hip Arthroplasty Registry, we identified 80,756 primary THAs performed in Denmark between Jan 1, 1995 and Dec 31, 2008. We used Cox regression analysis to compute crude and adjusted relative risk (RR) of revision due to infection. Revision was defined as extraction or exchange of any component due to infection. The median follow-up time was 5 (0–14) years.

Results

597 primary THAs (0.7%) were revised due to infection. Males, patients with any co-morbidity, patients operated due to non-traumatic avascular femoral head necrosis, and patients with long duration of surgery had an increased RR of revision due to infection within the total follow-up time. A tendency of increased RR of revision was found for patients who had received cemented THA without antibiotic and hybrid THA relative to patients with cementless implants. Hip diagnosis and fixation technique were not associated with risk of revision due to infection within 1 year of surgery (short-term risk).

Interpretation

We identified several categories of THA patients who had a higher risk of revision due to infection. Further research is required to explain the mechanism underlying this increased risk. More attention should be paid by clinicians to infection prevention strategies in patients with THA, particularly those with increased risk.As with any other surgical operation, serious complications in patients undergoing total hip arthroplasty (THA) include infections. Most infections stem either from contamination in the operating room or from later hematogenous spread. Deep infection is the third most common cause of revision of THAs in Denmark (DHR Annual repport 2008). In the last 2 decades, advances in theater design and the prophylactic use of antibiotics, either systemically or incorporated in cement, have substantially reduced the incidence of infection after hip replacement (Zimmerli and Ochsner 2003, Ridgeway et al. 2005, Phillips et al. 2006). However, recent studies in the United States and Norway have found increasing infection rates (Dale et al. 2009, Kurtz et al. 2010).Research on risk factors for revision due to infection following THA has been limited, probably due to low absolute numbers of revisions. However, in the last few years several reports have suggested that some patient- and surgery-related factors may play a role (Furnes et al. 2001, Saleh et al. 2002, Ridgeway et al. 2005, Engesaeter et al. 2006, Bongartz et al. 2008, Pulido et al. 2008, Dale et al. 2009, Hooper et al. 2009, Ong et al. 2009). Comparison of these studies is difficult due to different inclusion criteria for the study population and different definitions of infection, sometimes including both joint infections and superficial infections, or infections in general. We studied only the infections that were followed by revision of the implant.For this reason, we conducted a nationwide follow-up study using the Danish Hip Arthroplasty Registry to examine potential patient- and surgery-related risk factors for revision due to infection.     

Effects of metal-on-metal wear on the host immune system and infection in hip arthroplasty

Background and purpose

Joint replacement with metal-on-metal (MOM) bearings have gained popularity in the last decades in young and active patients. However, the possible effects of MOM wear debris and its corrosion products are still the subject of debate. Alongside the potential disadvantages such as toxicity, the influences of metal particles and metal ions on infection risk are unclear.

Methods

We reviewed the available literature on the influence of degradation products of MOM bearings in total hip arthroplasties on infection risk.

Results

Wear products were found to influence the risk of infection by hampering the immune system, by inhibiting or accelerating bacterial growth, and by a possible antibiotic resistance and heavy metal co-selection mechanism.

Interpretation

Whether or not the combined effects of MOM wear products make MOM bearings less or more prone to infection requires investigation in the near future.Many young patients with painful coxarthrosis want to return to a high level of activity and require an implant that provides durability. The low wear rates of metal-on-metal (MOM) bearings have led to a resurgence in the use of MOM bearings (Wagner and Wagner 2000, Silva et al. 2005, Pollard et al. 2006, Vendittoli et al. 2007, Delaunay et al. 2008). 35% of all prostheses in the United States in 2006 (Bozic et al. 2009) and 16% of all prostheses implanted in Australia from 1999 through 2007 had MOM bearings (Graves et al. 2008).Metal alloys used in MOM bearings degrade through wear, from corrosion, or by a combination of the two (Yan et al. 2006, Jacobs et al. 2008). Consequently, MOM bearings produce nanometer- to submicrometer-sized metal particles (Campbell et al. 1996, Doorn et al. 1998). The high number of these very small particles presents a large cumulative surface area for corrosion. The biological effects of these particles and their corrosion products in the human body are for the most part unclear. Since the renewed interest in MOM bearings, extensive research has been done to determine the consequences of local and systemic exposure to wear particles and accompanying biologically active corrosion products (Amstutz and Grigoris 1996). It is well known that metal debris can induce pathological changes such as the release of inflammatory cytokines from macrophages, histiocytosis, fibrosis, and necrosis (Basle et al. 1996, Granchi et al. 1998, Caicedo et al. 2008, 2009). Metal debris is also thought to be associated with hypersensitivity and osteolysis (Hallab et al. 2000, 2010, Goodman 2007b, Carr and DeSteiger 2008, Huber et al. 2009). However, there is very little literature on the bacteriological effects of these degradation products (Anwar et al. 2007, Hosman et al. 2009). It is therefore unclear whether they can influence the risk of infection.The Australian and New Zealand joint registries have shown that between 9% and 15% of all total hip arthroplasty (THA) revisions are carried out because of infections related to the primary prosthesis (Rothwell et al. 2007, Graves et al. 2008). In cases of infection, bacteria adopt a biofilm mode of growth on the surface of the prosthesis, thus increasing the antibiotic resistance and resulting in major difficulties in treatment (Trampuz and Widmer 2006). Removal and replacement of an infected implant is usually required to eliminate the infection (Bozic and Ries 2005, Vincent et al. 2006). Recent research has suggested that particulate debris of any composition promotes bacterial growth by providing a scaffold for bacterial adhesion and biofilm growth (Anwar et al. 2007). On the other hand, high concentrations of metal ions have been shown to have bacteriostatic properties (Hosman et al. 2009).Considering the paucity of publications on the effects of MOM particles on infection, we performed a review of the literature on the influence of MOM wear particles and their corrosion products on the risk of infection.     

Infection after primary hip arthroplasty: a comparison of 3 Norwegian health registers

Background and purpose

The aim of the present study was to assess incidence of and risk factors for infection after hip arthroplasty in data from 3 national health registries. We investigated differences in risk patterns between surgical site infection (SSI) and revision due to infection after primary total hip arthroplasty (THA) and hemiarthroplasty (HA).

Materials and methods

This observational study was based on prospective data from 2005–2009 on primary THAs and HAs from the Norwegian Arthroplasty Register (NAR), the Norwegian Hip Fracture Register (NHFR), and the Norwegian Surveillance System for Healthcare–Associated Infections (NOIS). The Norwegian Patient Register (NPR) was used for evaluation of case reporting. Cox regression analyses were performed with revision due to infection as endpoint for data from the NAR and the NHFR, and with SSI as the endpoint for data from the NOIS.

Results

The 1–year incidence of SSI in the NOIS was 3.0% after THA (167/5,540) and 7.3% after HA (103/1,416). The 1–year incidence of revision due to infection was 0.7% for THAs in the NAR (182/24,512) and 1.5% for HAs in the NHFR (128/8,262). Risk factors for SSI after THA were advanced age, ASA class higher than 2, and short duration of surgery. For THA, the risk factors for revision due to infection were male sex, advanced age, ASA class higher than 1, emergency surgery, uncemented fixation, and a National Nosocomial Infection Surveillance (NNIS) risk index of 2 or more. For HAs inserted after fracture, age less than 60 and short duration of surgery were risk factors of revision due to infection.

Interpretation

The incidences of SSI and revision due to infection after primary hip replacements in Norway are similar to those in other countries. There may be differences in risk pattern between SSI and revision due to infection after arthroplasty. The risk patterns for revision due to infection appear to be different for HA and THA.Increasing incidence of revision due to infection after primary total hip arthroplasty (THA) has been observed in different countries during the last decade (Kurtz et al. 2008, Dale et al. 2009, Pedersen et al. 2010). There have been several studies on incidence of and risk factors for infection based on data from surveillance systems (Ridgeway et al. 2005, Mannien et al. 2008), arthroplasty (quality) registers (Berbari et al. 1998, Dale et al. 2009, Pedersen et al. 2010), and administrative databases (Mahomed et al. 2003, Kurtz et al. 2008, Ong et al. 2009). There have been reviews on incidence of and risk factors for infection after hip arthroplasty, based on publications from databases with different definitions of infection (Urquhart et al. 2009, Jämsen et al. 2010a). Superficial surgical site infections (SSIs) may have risk factors that are different from those of full surgical revisions due to infection. Furthermore, THA and hip hemiarthroplasty (HA) may have different patterns of risk of infection (Ridgeway et al. 2005, Cordero–Ampuero and de Dios 2010).In the present study, we used data from 3 national health registries in Norway to assess incidence and some risk factors for infection after primary hip arthroplasty. Differences in risk patterns between SSI and revision due to infection were investigated for HA and THA.     

Hip resurfacing arthroplasty: short-term survivorship of 4,401 hips from the Finnish Arthroplasty Register

Background and purpose

Population-based registry data from the Nordic Arthroplasty Register Association (NARA) and from the National Joint Register of England and Wales have revealed that the outcome after hip resurfacing arthroplasty (HRA) is inferior to that of conventional total hip arthroplasty (THA). We analyzed the short-term survival of 4,401 HRAs in the Finnish Arthroplasty Register.

Methods

We compared the revision risk of the 4,401 HRAs from the Register to that of 48,409 THAs performed during the same time period. The median follow-up time was 3.5 (0–9) years for HRAs and 3.9 (0–9) years for THAs.

Results

There was no statistically significant difference in revision risk between HRAs and THAs (RR = 0.93, 95% CI: 0.78–1.10). Female patients had about double the revision risk of male patients (RR = 2.0, CI: 1.4–2.7). Hospitals that had performed 100 or more HRA procedures had a lower revision risk than those with less than 100 HRAs (RR = 0.6, CI: 0.4–0.9). Articular Surface Replacement (ASR, DePuy) had inferior outcome with higher revision risk than the Birmingham Hip Resurfacing implant (BHR, Smith & Nephew), the reference implant (RR = 1.8, CI: 1.2–2.7).

Interpretation

We found that HRA had comparable short-term survivorship to THA at a nationwide level. Implant design had an influence on revision rates. ASR had higher revision risk. Low hospital procedure volume worsened the outcome of HRA. Female patients had twice the revision risk of male patients.Good short-term results of using modern hip resurfacing devices have been reported from pioneering centers (Amstutz et al. 2004, Daniel et al. 2004). Recently, these results have been confirmed by independent studies (Hing et al. 2007a, Heilpern et al. 2008, Steffen et al. 2008, Khan et al. 2009). However, there have been a variety of early complications of HRA, such as femoral neck fracture, aseptic loosening of the femoral component, and metallosis of the hip joint with soft-tissue necrosis (Shimmin et al. 2005, Keegan et al. 2007, Grammatopolous et al. 2009, Ollivere et al. 2009). Registry data have revealed that the early revision rate of HRA is higher than that of THA (Australian Orthopaedic Association, Johanson et al. 2010). Furthermore, conventional stems can nowadays be used with a large metal-on-metal (MoM) articulation similar to that in HRA. We examined the early outcome of HRA and compared it to that of THA using data in the Finnish Arthroplasty Register.     

Role of preoperative pain,muscle function,and activity level in discharge readiness after fast-track hip and knee arthroplasty

Methods Before surgery, hip pain (THA) or knee pain (TKA), lower-extremity muscle power, functional performance, and physical activity were assessed in a sample of 150 patients and used as independent variables to predict the outcome (dependent variable)—readiness for hospital discharge —for each type of surgery. Discharge readiness was assessed twice daily by blinded assessors.Results Median discharge readiness and actual length of stay until discharge were both 2 days. Univariate linear regression followed by multiple linear regression revealed that age was the only independent predictor of discharge readiness in THA and TKA, but the standardized coefficients were small (≤ 0.03).Interpretation These results support the idea that fast-track THA and TKA with a length of stay of about 2–4 days can be achieved for most patients independently of preoperative functional characteristics.Over the last decade, length of stay (LOS) with discharge to home after primary THA and TKA has declined from about 5–10 days to about 2–4 days in selected series and larger nationwide series (Malviya et al. 2011, Raphael et al. 2011, Husted et al. 2012, Kehlet 2013, Hartog et al. 2013, Jørgensen and Kehlet 2013). However, there is a continuing debate about whether selected patients only or all patients should be scheduled for “fast-track” THA and TKA in relation to psychosocial factors and preoperative pain and functional status (Schneider et al. 2009, Hollowell et al. 2010, Macdonald et al. 2010, Antrobus and Bryson 2011, Jørgensen and Kehlet 2013), or whether organizational or pathophysiological factors in relation to the surgical trauma may determine the length of stay (Husted et al. 2011, Husted 2012).We studied the role of THA and TKA patients’ preoperative pain and functional characteristics in discharge from 2 orthopedic departments with well-established fast-track recovery regimens (Husted et al. 2010).     

Removal of restrictions following primary THA with posterolateral approach does not increase the risk of early dislocation

Background and purpose

Patient education and mobilization restrictions are often used in an attempt to reduce the risk of dislocation following primary THA. To date, there have been no studies investigating the safety of removal of mobilization restrictions following THA performed using a posterolateral approach. In this retrospective non-inferiority study, we investigated the rate of early dislocation following primary THA in an unselected patient cohort before and after removal of postoperative mobilization restrictions.

Patients and methods

From the Danish National Health Registry, we identified patients with early dislocation in 2 consecutive and unselected cohorts of patients who received primary THA at our institution from 2004 through 2008 (n = 946) and from 2010 through 2014 (n = 1,329). Patients in the first cohort were mobilized with functional restrictions following primary THA whereas patients in the second cohort were allowed unrestricted mobilization. Risk of early dislocation (within 90 days) was compared in the 2 groups and odds ratio (OR)—adjusted for possible confounders—was calculated. Reasons for early dislocation in the 2 groups were identified.

Results

When we adjusted for potential confounders, we found no increased risk of early dislocation within 90 days in patients who were mobilized without restrictions. Risk of dislocation within 90 days was lower (3.4% vs 2.8%), risk of dislocation within 30 days was lower (2.1% vs 2.0%), and risk of multiple dislocations (1.8% vs 1.1%) was lower in patients who were mobilized without restrictions, but not statistically significantly so. Increasing age was an independent risk factor for dislocation.

Interpretation

Removal of mobilization restrictions from the mobilization protocol following primary THA performed with a posterolateral approach did not lead to an increased risk of dislocation within 90 days.Dislocation of the hip is one of the most common complications following total hip arthroplasty (THA), with reported incidence rates ranging from less than 1% to over 15%, and higher risk of dislocation after revision arthroplasty than after primary THA (Woo and Morrey 1982, Phillips et al. 2003, Khatod et al. 2006, Patel et al. 2007). Several patient-related and surgery-related parameters, such as age (Ali Khan et al. 1981), cognitive function (Fackler and Poss 1980, Jolles et al. 2002), component malposition (Lewinnek et al. 1978, Jolles et al. 2002, Nishii et al. 2004), surgical approach (Masonis and Bourne 2002) and soft-tissue related factors (White et al. 2001) contribute to the risk of dislocation. In the past, many surgeons have used patient education and postoperative mobilization restrictions in an attempt to reduce this risk (Woo and Morrey 1982, Morrey 1992, 1997). However, in recent years some authors have questioned the benefit of such restrictions (Peak et al. 2005, Restrepo et al. 2011) and no published studies have ever confirmed a reduction in dislocation using restrictions, making some authors question the value of postoperative restrictions (Husted et al. 2014).A possible limitation of these studies was that they all investigated primary THA performed using the anterolateral approach, which is probably associated with a lower rate of dislocation than primary THA using the posterior approach (Masonis and Bourne 2002). One recent study investigated a reduction in movement restrictions following primary THA with the posterolateral approach and found that fewer movement restrictions did not affect the patient-reported outcomes after 6 weeks, and led to earlier return to work. However, no recommendations on safety issues could be made due to the low number of patients (Mikkelsen et al. 2014).The main aim of this retrospective, non-inferiority study was to investigate the rate of early dislocation (within 90 days) following primary THA in an unselected patient cohort before and after removal of postoperative mobilization restrictions. We also investigated the reasons for dislocation in patients who were mobilized with and without restrictions.     

Retrieval analysis of alumina ceramic-on-ceramic bearing couples

Background and purpose

Ceramic-on-ceramic (CoC) bearings have been in use in total hip replacement (THR) for more than 40 years, with excellent long-term survivorship. Although there have been several simulator studies describing the performance of these joints, there have only been a few retrieval analyses. The aim of this study was to investigate the wear patterns, the surface properties, and friction and lubrication regimes of explanted first-generation alumina bearings.

Materials and methods

We studied 9 explanted CoC bearings from Autophor THRs that were revised for aseptic loosening after a mean of 16 (range 7–19) years. The 3D surface roughness profiles of the femoral heads and acetabular cups (Srms, Sa, and Ssk) were measured to determine the microscopic wear. The bearings were imaged using an atomic-force microscope in contact mode, to produce a topographical map of the surfaces of the femoral heads. Friction tests were performed on the bearing couples to determine the lubrication regime under which they were operating during the walking cycle. The diametral clearances were also measured.

Results

3 femoral heads showed stripe wear and the remaining 6 bearings showed minimal wear. The femoral heads with stripe wear had significantly higher surface roughness than the minimally worn bearings (0.645 vs. 0.289, p = 0.04). High diametral clearances, higher than expected friction, and mixed/boundary lubrication regimes prevailed in these retrieved bearings.

Interpretation

Despite the less than ideal tribological factors, these first-generation CoC bearings still showed minimal wear in the long term compared to previous retrieval analyses.Ceramic-on-ceramic (CoC) bearings for total hip replacement (THR) were developed in the early 1970s. The earliest designs, typified by the Ceraver-Osteal implant, failed because of inadequate fixation and high fracture rates of the ceramic (Boutin et al. 1988, Mittelmeier and Heisel 1992). Throughout the 1980s, the Mittelmeier Autophor ceramic prosthesis (Smith and Nephew, Memphis, TN) was widely used. The threaded external surface of the acetabular component gave primary stability, but it had no porous surface for bony ingrowth. This design did not improve the rate of aseptic loosening, but the fracture rate was notably reduced (Boutin et al. 1988, Sedel 2000, Tateiwa et al. 2008, Jeffers and Walter 2012). Since the early 1990s, the predominant design has been a rough or porous-coated titanium shell with a ceramic liner.A recent systematic review of CoC THRs confirmed excellent survivorship of the modern implants of up to 97% at 10 years (Jeffers and Walter 2012). It is likely that the improvements in acetabular fixation as well as in the manufacturing process, design, and quality control of the ceramic bearings have contributed to the excellent clinical results. Ceramic bearings are relatively inert, and they have excellent wear properties (Savarino et al. 2009). There have only been isolated case reports describing osteolysis around CoC bearings possibly making revision surgery easier with the preserved bone stock (Yoon et al. 1998, Sedel 2000, Tateiwa et al. 2008, Hannouche et al. 2011). The fracture rates of modern alumina ceramic bearings have been reported to be as low as 1 in 25,000 (Nizard et al. 2005, Tateiwa et al. 2008, Jeffers and Walter 2012).Hip simulator studies on CoC bearings have consistently shown very low wear rates (Nevelos et al. 2001, Rieker et al. 2001, Tipper et al. 2002, Stewart et al. 2003), but this has not been reflected by the long-term retrieval analyses (Nevelos et al. 1999, 2001, Prudhommeaux et al. 2000, Affatato et al. 2012). It must be understood, however, that retrieval studies are performed on joints that have failed, not well-functioning joints, so this does not give information on the larger proportion of successful CoC THRs. There have only been a few long-term retrieval analyses of explanted CoC bearings (Nevelos et al. 1999, 2001, Prudhommeaux et al. 2000) and even fewer retrieval analyses of modern CoC bearings (Affatato et al. 2012). With the excellent clinical survivorship of the modern implants (Jeffers and Walter 2012), failed first-generation CoC bearings may well have to be studied to more fully understand the in vivo tribology.The aim of this study was to investigate the wear patterns, the surface properties, and friction and lubrication regimes in 9 explanted first-generation alumina CoC bearings. The tribological data from this study are likely to represent the worst case scenario, which can be used for comparison in future retrieval studies featuring modern CoC bearings.     

Early subsidence of shape-closed hip arthroplasty stems is associated with late revision: A systematic review and meta-analysis of 24 RSA studies and 56 survival studies

Background and purpose

Few studies have addressed the association between early migration of femoral stems and late aseptic revision in total hip arthroplasty. We performed a meta-regression analysis on 2 parallel systematic reviews and meta-analyses to determine the association between early migration and late aseptic revision of femoral stems.

Patients and methods

Of the 2 reviews, one covered early migration data obtained from radiostereometric analysis (RSA) studies and the other covered long-term aseptic revision rates obtained from survival studies with endpoint revision for aseptic loosening. Stems were stratified according to the design concept: cemented shape-closed, cemented force-closed, and uncemented. A weighted regression model was used to assess the association between early migration and late aseptic revision, and to correct for confounders. Thresholds for acceptable and unacceptable migration were determined in accordance with the national joint registries (≤ 5% revision at 10 years) and the NICE criteria (≤ 10% revision at 10 years).

Results

24 studies (731 stems) were included in the RSA review and 56 studies (20,599 stems) were included in the survival analysis review. Combining both reviews for the 3 design concepts showed that for every 0.1-mm increase in 2-year subsidence, as measured with RSA, there was a 4% increase in revision rate for the shape-closed stem designs. This association remained after correction for age, sex, diagnosis, hospital type, continent, and study quality. The threshold for acceptable migration of shape-closed designs was defined at 0.15 mm; stems subsiding less than 0.15 mm in 2 years had revision rates of less than 5% at 10 years, while stems exceeding 0.15 mm subsidence had revision rates of more than 5%.

Interpretation

There was a clinically relevant association between early subsidence of shape-closed femoral stems and late revision for aseptic loosening. This association can be used to assess the safety of shape-closed stem designs. The published research is not sufficient to allow us to make any conclusions regarding such an association for the force-closed and uncemented stems.Over 1 million total hip arthroplasties (THAs) are performed every year worldwide, and this number is expected to double within the next 2 decades (Pivec et al. 2012). The design and method of fixation of a THA determines the stability of the implant, and these are therefore crucial factors for achievement of long-term survival. However, most of the new THA designs have been introduced onto the market without demonstrating good performance (Sheth et al. 2009). This has led to several THAs having high failure rates, such as the Charnley Elite Plus (Hauptfleisch et al. 2006). To prevent future disasters with orthopedic implants, several countries have developed guidelines to guarantee patient safety, e.g. the NICE guidelines (NHS). Furthermore, it has become increasingly evident that a phased evidence-based introduction, as is common with pharmaceuticals, is necessary to regulate the introduction of new THA designs to the market (Malchau 2000, McCulloch et al. 2009, Schemitsch et al. 2010). This should include systematic assessment and early detection of aseptic loosening in small groups of patients.Although it may take as long as 10 years for aseptic loosening of implants to become manifest, it is possible to detect the loosening process as early as 1–2 years postoperatively, using radiostereometric analysis (RSA). Since RSA allows in vivo, 3D measurement of the migration of THAs with an accuracy of 0.2 mm for translations and 0.5 degrees for rotations, only a small number of patients is needed to compare a new innovative design to a gold-standard design (Grewal et al. 1992, Karrholm et al. 1994, Ryd et al. 1995, Thanner et al. 1995, Hauptfleisch et al. 2006, Nieuwenhuijse et al. 2012). Thus, only a few patients will have been exposed if that design turns out to be a poor one. RSA could therefore play an important role in phased evidence-based market introduction of new THA designs (Faro and Huiskes 1992, Bulstrode et al. 1993, Malchau 1995, 2000, Nelissen et al. 2011).Following on from our 2 earlier studies on the association between early migration and late aseptic revision of tibial components and acetabular cups, this systematic review and meta-analysis focused on the femoral stem (Pijls et al. 2012a, b). We hypothesized that early migration, as measured with RSA, is associated with late revision for aseptic loosening. We systematically reviewed the association between early migration and late revision for aseptic loosening of the femoral stem in primary THA. This could eventually lead to clinical guidelines, to be used in a phased introduction of new THA designs.     

No association between serum metal ions and implant fixation in large-head metal-on-metal total hip arthroplasty: A 5-year radiostereometric study of 49 hips

Background

The mechanism of failure of metal-on-metal (MoM) total hip arthroplasty (THA) has been related to a high rate of metal wear debris, which is partly generated from the head-trunnion interface. However, it is not known whether implant fixation is affected by metal wear debris.

Patients and methods

49 cases of MoM THA in 41 patients (10 women) with a mean age of 52 (28–68) years were followed with stereoradiographs after surgery and at 1, 2, and 5 years to analyze implant migration by radiostereometric analysis (RSA). Patients also participated in a 5- to 7-year follow-up with measurement of serum metal ions, questionnaires (Oxford hip score (OHS) and Harris hip score (HHS)), and measurement of cup and stem positions and systemic bone mineral density.

Results

At 1–2 years, mean total translation (TT) was 0.04 mm (95% CI: –0.07 to 0.14; p = 0.5) for the stems; at 2–5 years, mean TT was 0.13 mm (95% CI: –0.25 to –0.01; p = 0.03), but within the precision limit of the method. For the cups, there was no statistically significant TT or total rotation (TR) at 1–2 and 2–5 years. At 2–5 years, we found 4 cups and 5 stems with TT migrations exceeding the precision limit of the method. There was an association between cup migration and total OHS < 40 (4 patients, 4 hips; p = 0.04), but there were no statistically significant associations between cup or stem migration and T-scores < –1 (n = 10), cup and stem positions, or elevated serum metal ion levels (> 7µg/L (4 patients, 6 hips)).

Interpretation

Most cups and stems were well-fixed at 1–5 years. However, at 2–5 years, 4 cups and 5 stems had TT migrations above the precision limits, but these patients had serum metal ion levels similar to those of patients without measurable migrations, and they were pain-free. Patients with serum metal ion levels > 7 µg/L had migrations similar to those in patients with serum metal ion levels < 7 µg/L. Metal wear debris does not appear to influence the fixation of hip components in large-head MoM articulations at medium-term follow-up.Metal-on-metal (MoM) hip articulations allow the use of larger-diameter femoral head sizes than other constrained articulation types like metal-on-polyethylene (MoP) and ceramic-on-ceramic (CoC) total hip arthroplasties (THAs), where a liner must be interpositioned between the femoral head and the metal shell. Large-diameter MoM hip articulations more closely mimic the natural human anatomy; they improve joint stability and reduce the incidence of postoperative dislocation (Krantz et al. 2012). Furthermore, they reduce the volume of wear particles, which has been considered advantageous from a quality and bearing perspective since wear particles from in MoP bearings are clearly associated with osteolysis and aseptic loosening in THA. MoM hip articulations have therefore been recommended worldwide in the past decade and used for younger patients with high activity levels. Although volumetric wear rates at the surfaces of MoM bearings are 20 times lower than those of conventional MoP bearings, and although the wear particles are typically smaller than 50 nm (Doorn et al. 1998), the number of nano-sized metal particles generated is up to 500 times higher than for MoP bearings (Sieber et al. 1999, Mabilleau et al. 2008). These nano-sized metal particles and metal ions from the MoM bearing and the trunnion of the neck junction are spread both locally and systemically. Phagocytosis of the nano-sized metal particles impairs osteoblastic activity, which may contribute to the cellular events that occur during aseptic loosening and soft tissue destruction (Lohmann et al. 2000).No previous studies have investigated the implant stability of large-head MoM THAs, and only a few studies have evaluated the stability of MoM hip resurfacing articulations (RHAs) (Glyn-Jones et al. 2004, Itayem et al. 2005, 2007, Baad-Hansen et al. 2011, Penny et al. 2012, Lorenzen et al. 2013).We hypothesized that MoM implant migration would be more extensive in patients with elevated serum metal ion levels than in patients whose serum metal ion levels were within the acceptable range (< 7 µg/L), and that MoM implants would be well-fixed in those with acceptable serum metal ion levels.     

Why still in hospital after fast-track hip and knee arthroplasty?

Background and purpose

Length of stay (LOS) following total hip and knee arthroplasty (THA and TKA) has been reduced to about 3 days in fast-track setups with functional discharge criteria. Earlier studies have identified patient characteristics predicting LOS, but little is known about specific reasons for being hospitalized following fast-track THA and TKA.

Patients and methods

To determine clinical and logistical factors that keep patients in hospital for the first postoperative 24–72 hours, we performed a cohort study of consecutive, unselected patients undergoing unilateral primary THA (n = 98) or TKA (n = 109). Median length of stay was 2 days. Patients were operated with spinal anesthesia and received multimodal analgesia with paracetamol, a COX-2 inhibitor, and gabapentin—with opioid only on request. Fulfillment of functional discharge criteria was assessed twice daily and specified reasons for not allowing discharge were registered.

Results

Pain, dizziness, and general weakness were the main clinical reasons for being hospitalized at 24 and 48 hours postoperatively while nausea, vomiting, confusion, and sedation delayed discharge to a minimal extent. Waiting for blood transfusion (when needed), for start of physiotherapy, and for postoperative radiographic examination delayed discharge in one fifth of the patients.

Interpretation

Future efforts to enhance recovery and reduce length of stay after THA and TKA should focus on analgesia, prevention of orthostatism, and rapid recovery of muscle function.Total hip and total knee arthroplasty (THA and TKA) are frequent operations with an average length of stay (LOS) of about 6–12 days in the United Kingdom, Germany, and Denmark (Husted et al. 2006, Bundesauswertung 2009, NHS 2010).During the last decade, however, there has been increased interest in optimal multimodal perioperative care to enhance recovery (the fast-track methodology). Improvement of analgesia; reduction of surgical stress responses and organ dysfunctions including nausea, vomiting, and ileus; early mobilization; and oral nutrition have been of particular interest (Kehlet 2008, Kehlet and Wilmore 2008). These principles have also been applied to THA and TKA, resulting in improvements in pain treatment with multimodal opioid-sparing regimens including a local anesthetic infiltration technique (LIA) or peripheral nerve blocks to facilitate early mobilization (Ilfeld et al. 2006a, b, 2010a, Andersen et al. 2008, Kerr and Kohan 2008), and allowing functional rehabilitation to be initiated a few hours postoperatively (Holm et al. 2010)—ultimately leading to a reduction in LOS (Husted et al. 2008, Barbieri et al. 2009, Husted et al. 2010a, b). Using these evidence-based regimens combined with an improved logistical setup, LOS is reduced to about 2–4 days (Kerr and Kohan 2008, Husted et al. 2010 a,b,c, Lunn et al. 2011).Having well-defined functional discharge criteria is imperative in order to ensure a safe discharge—and it is mandatory if meaningful comparison of LOS is done following alterations in the track (Husted et al. 2008). In the same fast-track setting, an earlier study focused on patient characteristics predicting LOS (Husted et al. 2008). However, little is known about the specific reasons for why patients are hospitalized during the first 1–3 days after THA or TKA; i.e. why can patients not be discharged?We therefore analyzed clinical and organizational factors responsible for being hospitalized in a well-defined prospective setup in a fast-track unit. This unit had previously documented LOS of about 2–3 days (Andersen et al. 2008, Holm et al. 2010, Husted et al. 2010b, c, Lunn et al. 2011).     

Uncemented femoral revision arthroplasty using a modular tapered,fluted titanium stem: 5- to 16-year results of 163 cases

Background and purpose —

Due to the relative lack of reports on the medium- to long-term clinical and radiographic results of modular femoral cementless revision, we conducted this study to evaluate the medium- to long-term results of uncemented femoral stem revisions using the modular MRP-TITAN stem with distal diaphyseal fixation in a consecutive patient series.

Patients and methods —

We retrospectively analyzed 163 femoral stem revisions performed between 1993 and 2001 with a mean follow-up of 10 (5–16) years. Clinical assessment included the Harris hip score (HHS) with reference to comorbidities and femoral defect sizes classified by Charnley and Paprosky. Intraoperative and postoperative complications were analyzed and the failure rate of the MRP stem for any reason was examined.

Results —

Mean HHS improved up to the last follow-up (37 (SD 24) vs. 79 (SD 19); p < 0.001). 99 cases (61%) had extensive bone defects (Paprosky IIB–III). Radiographic evaluation showed stable stem anchorage in 151 cases (93%) at the last follow-up. 10 implants (6%) failed for various reasons. Neither a breakage of a stem nor loosening of the morse taper junction was recorded. Kaplan-Meier survival analysis revealed a 10-year survival probability of 97% (95% CI: 95–100).

Interpretation —

This is one of the largest medium- to long-term analyses of cementless modular revision stems with distal diaphyseal anchorage. The modular MRP-TITAN was reliable, with a Kaplan-Meier survival probability of 97% at 10 years.Long-term outcome of femoral revision arthroplasty depends on proper restoration of joint mechanics by reconstructing the anatomic center of rotation in combination with fixation that provides long-term stability (Gravius et al. 2011).The published medium- to long-term survival rates of cemented revision THA are between 35% and 91% (Kavanagh and Fitzgerald 1985, Retpen et al. 1989, Stromberg and Herberts 1996, Weber et al. 1996). One stage cemented stem revision leads to increased bone loss (Rader and Eulert 2005) and is associated with a much higher rate of re-revision than cementless femoral stem revision (Dohmae et al. 1988). Cemented revision stems only appear to be advisable for less active patients with an average life expectancy of less than 10 years (Weiss et al. 2011). In comparison, uncemented revision hip arthroplasty gives medium- to long-term survival rates of 60–97% (Head et al. 2001, Engh et al. 2002, Kwong et al. 2003).Over the years, uncemented modular revision stems have become increasingly popular (Fink et al. 2009). In complex revision surgery, modular uncemented femoral implants may overcome the limitations of non-modular and mostly straight stems—for example, the difficulty in establishing femoral leg length, femoral anteversion, and soft tissue tension (Berry 2002, Mumme et al. 2004, Gutierrez et al. 2007). Modular cementless implant systems with a distal diaphyseal press-fit concept provide greater variability in difficult anatomical situations than non-modular revision stems (Berry 2002). The modular-designed components offer the opportunity to customize the prosthesis intraoperatively to the individual anatomical situation, allowing nearly physiological joint reconstruction (Gravius et al. 2011).Based on published studies, the modular cementless MRP-TITAN revision stem with its distal diaphyseal fixation concept has well-proven short-term effectiveness in femoral revision, especially for large femoral defects (types IIC and III, as described by Paprosky et al. (1990)). Previous studies have shown low mechanical failure rates of 2–5% after 4–5 years of follow-up (Wirtz et al. 2000, Mumme et al. 2004, 2007).Due to the relative lack of medium- to long-term results of femoral modular cementless revision surgery in the literature, we investigated the clinical and radiographic medium- to long-term outcome of femoral revision arthroplasty with the MRP-TITAN stem in a consecutive patient series.     

Hospital volume affects outcome after total knee arthroplasty: A nationwide registry analysis of 80 hospitals and 59,696 replacements

ResultsThe greater the volume of the hospital, the shorter was the average LOS and LUIC. Smaller hospital volume was not unambiguously associated with increased revision, re-admission, or MUA rates. The smaller the annual hospital volume, the more often patients were discharged home.InterpretationLOS and LUIC ought to be shortened in lower-volume hospitals. There is potential for a reduction in length of stay in extended institutional care facilities.Total knee replacement (TKR) is one of the most common orthopedic procedures, and it is expected to increase markedly in volume (Kurtz et al. 2007). Due to the potentially severe complications and the high economic impact of the procedure, efforts to minimize the risks and optimize perioperative efficiency are important.It has been suggested that increased hospital volume and reduction in length of stay (LOS) at the operating hospital after TKR are related, but there is no consensus (Yasunaga et al. 2009, Marlow et al. 2010, Paterson et al. 2010, Bozic et al. 2010, Styron et al. 2011). In addition, results on the association of hospital volume with re-admission rates (Soohoo et al. 2006b, Judge et al. 2006, Bozic et al. 2010, Cram et al. 2011) and revision risk have been inconclusive (Shervin et al. 2007, Manley et al. 2009, Bozic et al. 2010, Paterson et al. 2010). No-one has tried to study the association between length of uninterrupted institutional care (LUIC), incidence of manipulation under anesthesia (MUA) after TKR, and hospital volume.By combining 5 national-level registries, we examined possible associations between hospital volume and LOS, LUIC, discharge disposition, number of re-admissions within 14 and 42 days, MUA, and revisions after TKR for all knee arthroplasties performed in Finland between 1998 and 2010.     

Inferior outcome after hip resurfacing arthroplasty than after conventional arthroplasty. Evidence from the Nordic Arthroplasty Register Association (NARA) database, 1995 to 2007

Background and purpose

The reported outcomes of hip resurfacing arthroplasty (HRA) vary. The frequency of this procedure in Denmark, Norway, and Sweden is low. We therefore determined the outcome of HRA in the NARA database, which is common to all 3 countries, and compared it to the outcome of conventional total hip arthroplasty (THA).

Methods

The risk of non-septic revision within 2 years was analyzed in 1,638 HRAs and compared to that for 172,554 conventional total hip arthroplasties (THAs), using Cox regression models. We calculated relative risk (RR) of revision and 95% confidence interval.

Results

HRA had an almost 3-fold increased revision risk compared to THA (RR = 2.7, 95% CI: 1.9–3.7). The difference was even greater when HRA was compared to the THA subgroup of cemented THAs (RR = 3.8, CI: 2.7–5.3). For men below 50 years of age, this difference was less pronounced (HRA vs. THA: RR = 1.9, CI: 1.0–3.9; HRA vs. cemented THA: RR = 2.4, CI: 1.1–5.3), but it was even more pronounced in women of the same age group (HRA vs. THA: RR = 4.7, CI: 2.6–8.5; HRA vs. cemented THA: RR = 7.4, CI: 3.7–15). Within the HRA group, risk of non-septic revision was reduced in hospitals performing ≥ 70 HRAs annually (RR = 0.3, CI: 0.1–0.7) and with use of Birmingham hip resurfacing (BHR) rather than the other designs as a group (RR = 0.3, CI: 0.1–0.7). Risk of early revision was also reduced in males (RR = 0.5, CI: 0.2–0.9). The femoral head diameter alone had no statistically significant influence on the early revision rate, but it eliminated the significance of male sex in a combined analysis.

Interpretation

In general, our results do not support continued use of hip resurfacing arthroplasty. Men had a lower early revision rate, which was still higher than observed for all-cemented hips. Further follow-up is necessary to determine whether HRA might be useful as an alternative in males.The development of contemporary metal-on-metal (MOM) bearings has stimulated renewed interest in hip resurfacing arthroplasty (HRA) of the hip. These devices are available in different designs, most of which are hybrid concepts with cemented femoral and uncemented acetabular components. The proposed advantages of HRA compared to conventional total hip arthroplasty (THA) include improved range of motion and hip function, bone preservation, lower dislocation rates, and easier and safer revision procedures in case of failure (Shimmin et al. 2008). Because of the low wear characteristics observed in the laboratory and in clinical situations, the MOM bearing is thought to be especially suitable for patients with a long life expectancy (McMinn and Daniel 2006).Early reports from specialized centers have shown high survival rates: 97.8–99.8% after 3–5 years (Daniel et al. 2004, Treacy et al. 2005, Hing et al. 2007). Other authors have reported inferior results (Kim et al. 2008, Stulberg et al. 2008). Narrowing of patient selection criteria and refinement of surgical technique have improved the results in some case series (Mont et al. 2007, Amstutz et al. 2007). Several studies have shown that HRA is associated with a long learning curve. Early failures or inadequate implant positioning occurred at the beginning of the learner''s case series, which tended to decrease thereafter (Marker et al. 2007, Witjes et al. 2009, Nunley et al. 2010). Early failures are most commonly caused by femoral neck fracture and aseptic loosening of the femoral component. Thus, there are several indications that the outcome of HRA is influenced by patient selection, surgical technique, and experience in using this type of implant.Short- and medium-term results of HRA have previously been reported from national joint replacement registries. There has been a rapid increase in the use of HRA, with varying percentages of HRA relative to the total volume of THAs reported by different registries (Kärrholm et al. 2008, CJRR 2008-2009, AOANJRR 2008). Reports of inferior results, except in younger males with primary osteoarthritis, are most probably responsible for the recent tendency of decreasing use of HRA—especially in females (AOANJRR 2008). Further reports of comparatively rare but serious complications (Pandit et al. 2008, Hart et al. 2009, Ollivere et al. 2009) have probably also contributed to this tendency. Poor results after revision of failed HRA, equal to those obtained after revision of THA (AOANJRR 2008), may also have contributed to more restricted use.We analyzed the early outcome concerning aseptic revisions within 2 years of HRA and compared it to that of THA in the common database of the Nordic Arthroplasty Register Association (Havelin et al. 2009). We also evaluated the extent to which outcome was influenced by implant design, number of procedures per hospital, and femoral head size.     

Fast-track revision knee arthroplasty. A feasibility study

Background and purpose

Fast-track surgery has reduced the length of hospital stay (LOS), morbidity, and convalescence in primary hip and knee arthroplasty (TKA). We assessed whether patients undergoing revision TKA for non-septic indications might also benefit from fast-track surgery.

Methods

29 patients were operated with 30 revision arthroplasties. Median age was 67 (34–84) years. All patients followed a standardized fast-track set-up designed for primary TKA. We determined the outcome regarding LOS, morbidity, mortality, and satisfaction.

Results

Median LOS was 2 (1–4) days excluding 1 patient, who was transferred to another hospital for logistical reasons (10 days). None of the patients died within 3 months, and 3 patients were re-admitted (2 for suspicion of DVT, which was not found, and 1 for joint mobilization). Patient satisfaction was high.

Interpretation

Patients undergoing revision TKA for non-septic reasons may be included in fast-track protocols. Outcome appears to be similar to that of primary TKA regarding LOS, morbidity, and satisfaction. Our findings call for larger confirmatory studies and studies involving other indications (revision THA, 1-stage septic revisions).For more than a decade, favorable outcomes following fast-track protocols rather than more conventional hospital stays have been reported from numerous studies on primary THA and TKA. In the last few years, outcomes have been further improved, mainly due to improved multimodal opioid-sparing analgesia and early mobilization, allowing patients to fulfill functional discharge criteria within 2–3 days (Husted et al. 2008, 2010 a,b,c,d, Larsen et al. 2008 a,b,c, 2009, Andersen et al. 2009, Barbieri et al. 2009, Rotter et al. 2010). The addition of local infiltration analgesia (LIA) has improved early analgesia and facilitated early recovery, allowing patients to ambulate with full weight bearing within 2–3 hours of surgery (Andersen et al. 2008 a,b, 2009, Holm et al. 2010).So far, however, no one has reported the potential benefits of the fast-track methodology (including multimodal opioid-sparing analgesia, perioperative LIA, and early mobilization) for revision TKA, with its more extensive surgical trauma leading to a corresponding increase in the surgical stress responses. We therefore investigated the feasibility of our well-documented fast-track primary TKA program on a consecutive cohort of revision TKA patients.     

Perioperative mortality after hemiarthroplasty related to fixation method

Background and purpose

The appropriate fixation method for hemiarthroplasty of the hip as it relates to implant survivorship and patient mortality is a matter of ongoing debate. We examined the influence of fixation method on revision rate and mortality.

Methods

We analyzed approximately 25,000 hemiarthroplasty cases from the AOA National Joint Replacement Registry. Deaths at 1 day, 1 week, 1 month, and 1 year were compared for all patients and among subgroups based on implant type.

Results

Patients treated with cemented monoblock hemiarthroplasty had a 1.7-times higher day-1 mortality compared to uncemented monoblock components (p < 0.001). This finding was reversed by 1 week, 1 month, and 1 year after surgery (p < 0.001). Modular hemiarthroplasties did not reveal a difference in mortality between fixation methods at any time point.

Interpretation

This study shows lower (or similar) overall mortality with cemented hemiarthroplasty of the hip.The frequency of hip fractures is increasing with our ageing population, with an annual incidence of between 1.4 and 5 per 103 per year (Lonnroos et al. 2006, Icks et al. 2008, Varez-Nebreda et al. 2008). Health model projections have estimated that 6.3 million hip fractures will occur annually worldwide within the next 40 years (Cooper et al. 1992), imposing a significant economic health burden. There is a large reported perioperative mortality rate in this population, ranging from 2.4% to 8.2% at 1 month (Parvizi et al. 2001, Radcliff et al. 2008) and over 25% at 1 year (Elliott et al. 2003, Jiang et al. 2005). Furthermore, it was recently reported that the current mortality rate is higher now than 25 years ago (Vestergaard et al. 2007a). Today, it is generally accepted that displaced intracapsular fractures are best treated with arthroplasty rather than internal fixation (Keating et al. 2006, Leighton et al. 2007). In the at-risk population, however, multiple comorbidities are common and the best form of component fixation is in question.Bone cement implantation syndrome is a well-described complication of cemented hip arthroplasty. It is characterized by a systemic drop in systolic blood pressure, hypoxemia, pulmonary hypertension, cardiac dysrhythmias, and occasionally cardiac arrest and death (Rinecker 1980, Orsini et al. 1987, Parvizi et al. 1999). The prevailing theory to explain the pathophysiology of this phenomenon is embolism of fat, marrow contents, bone, and to some degree methylmethacrylate to the lung (Rinecker 1980, Elmaraghy et al. 1998, Parvizi et al. 1999, Koessler et al. 2001). An increased degree of pulmonary insult with fat microemboli has been demonstrated (mostly in randomized controlled trials) during insertion of a cemented femoral stem rather than an uncemented implant (Orsini et al. 1987, Ries et al. 1993, Christie et al. 1994, Pitto et al. 1999), presumably due to increased intramedullary femoral canal pressures in the cemented group (Kallos et al. 1974, Orsini et al. 1987). These pressures can be reduced by the use of distal venting holes in the femur during stem insertion (Engesæter et al. 1984). It has been shown previously by single-institutional review that patients undergoing cemented hip arthroplasty have a higher intraoperative mortality rate relative to uncemented arthroplasty, presumably due to a reduced incidence of fat embolism in the latter group (Parvizi et al. 1999). The increased mortality risk was also present at 30 days in the treatment of acute fractures with cemented arthroplasty, also from a single-institutional review (Parvizi et al. 2004). Although cement-related mortality is rare (Dearborn and Harris 1998, Parvizi et al. 1999, 2001, 2004, Weinrauch et al. 2006), it is a devastating complication—often reported through observational studies or literature reviews. Proponents of uncemented hip arthroplasty often cite this concern to support their reluctance to use cemented hip arthroplasty in both elective procedures and fracture management. However, many different types of studies have been unable to identify any increased mortality risk with the use of cement (Lausten and Vedel 1982 (observational), Emery et al. 1991 (RCT), Lo et al. 1994 (observational), Khan et al. 2002a,b (literature review), Parker and Gurusamy 2004 (literature review)) and others have shown a decrease in mortality at 30 days when cement is used (Foster et al. 2005).Cemented hip hemiarthroplasty appears to offer improved rate of return to baseline function, reduced postoperative pain, and superior long-term survivorship relative to uncemented arthroplasty (Khan et al. 2002a, b, Parker and Gurusamy 2004). We reasoned that failure to return to baseline function after hemiarthroplasty may be another risk factor for perioperative mortality (Hannan et al. 2001, Braithwaite et al. 2003). Lower revision rates for cemented prostheses and increased mortality at revision surgery contribute further to reducing the overall mortality risk. We evaluated the relationship between the method of fixation of hip arthroplasty and perioperative mortality using a large national joint replacement registry.     

Silent soft tissue pathology is common with a modern metal-on-metal hip arthroplasty

Background and purpose

Adverse reactions to metal debris have been reported to be a cause of pain in metal-on-metal hip arthroplasty. We assessed the incidence of both symptomatic and asymptomatic adverse reactions in a consecutive series of patients with a modern large-head metal-on-metal hip arthroplasty.

Methods

We studied the early clinical results and results of routine metal artifact-reduction MRI screening in a series of 79 large-head metal-on-metal hip arthroplasties (ASR; DePuy, Leeds, UK) in 68 patients. 75 hips were MRI scanned at mean 31 (12–52) months after surgery.

Results

27 of 75 hips had MRI-detected metal debris-related abnormalities, of which 5 were mild, 18 moderate, and 4 severe. 8 of these hips have been revised, 6 of which were revised for an adverse reaction to metal debris, diagnosed preoperatively with MRI and confirmed histologically. The mean Oxford hip score (OHS) for the whole cohort was 21. It was mean 23 for patients with no MRI-based evidence of adverse reactions and 19 for those with adverse reactions detected by MRI. 6 of 12 patients with a best possible OHS of 12 had MRI-based evidence of an adverse reaction.

Interpretation

We have found a high early revision rate with a modern, large-head metal-on-metal hip arthroplasty. MRI-detected adverse rections to metal debris was common and often clinically “silent”. We recommend that patients with this implant should be closely followed up and undergo routine metal artifact-reduction MRI screening.Metal-on-metal (MoM) total hip replacements have been used since the 1960s. Failure in early designs was attributed to mechanical loosening caused by poor bearing tolerances producing high friction (Amstutz and Grigoris 1996, Kothari et al. 1996). Improved manufacturing and engineering techniques enabled the development of a new generation of MoM hip replacements. In the 1990s, the Birmingham Hip Resurfacing (BHR) was developed, and good early to medium-term results have been published (Daniel et al. 2004, Treacy et al. 2005, Heilpern et al. 2008). Similar implants, both resurfacings and large MoM bearings, coupled with standard femoral stems were subsequently developed and marketed by other manufacturers.The development of magnetic resonance imaging (MRI) metal artifact reduction (MAR) sequences has enabled good visualization of the periprosthetic tissues (Toms et al. 2008), and been reported to be a clinically useful part of the assessment of painful MoM hip replacements (Hart et al. 2009). A number of authors have described the appearance of collections of fluid and inflammatory masses around painful MoM hip arthroplasties (Boardman et al. 2006, Pandit et al. 2008, Toms et al. 2008). These have been grouped under a variety of headings such as “aseptic lymphocyte-dominated vasculitis-associated lesions” (Willert et al. 2005), “pseudotumors” (Pandit et al. 2008), or “adverse reactions to metal debris (ARMD)” (Langton et al. 2010). Although these lesions have been previously described in patients investigated for pain, there have been no studies on the overall incidence of these lesions in an unselected series of patients, including those with no, or few, symptoms. It is not known whether these lesions may occur in the absence of symptoms.At our institution, we have a policy of offering routine MAR MRI imaging to patients who have undergone MoM total hip replacement or resurfacing. We determined the early clinical outcome, revision rate, and incidence of ARMD using MAR MRI screening in a consecutive series of patients with an ASR THR or resurfacing (ASR; DePuy, Leeds, UK).     

Hydroxyapatite coating does not improve uncemented stem survival after total hip arthroplasty!: An analysis of 116,069 THAs in the Nordic Arthroplasty Register Association (NARA) database

ResultsUnadjusted 10-year survival with the endpoint revision of any component for any reason was 92.1% (CI: 91.8–92.4). Unadjusted 10-year survival with the endpoint stem revision due to aseptic loosening varied between the stem brands investigated and ranged from 96.7% (CI: 94.4–99.0) to 99.9% (CI: 99.6–100). Of the stem brands with the best survival, stems with and without HA coating were found. The presence of HA coating was not associated with statistically significant effects on the adjusted risk of stem revision due to aseptic loosening, with an HR of 0.8 (CI: 0.5–1.3; p = 0.4). The adjusted risk of revision due to infection was similar in the groups of THAs using HA-coated and non-HA-coated stems, with an HR of 0.9 (CI: 0.8–1.1; p = 0.6) for the presence of HA coating. The commonly used Bimetric stem (n = 25,329) was available both with and without HA coating, and the adjusted risk of stem revision due to aseptic loosening was similar for the 2 variants, with an HR of 0.9 (CI: 0.5–1.4; p = 0.5) for the HA-coated Bimetric stem.InterpretationUncemented HA-coated stems had similar results to those of uncemented stems with porous coating or rough sand-blasted stems. The use of HA coating on stems available both with and without this surface treatment had no clinically relevant effect on their outcome, and we thus question whether HA coating adds any value to well-functioning stem designs.Hydroxyapatite (HA) is thought to improve early implant ingrowth and long-term stability in bone (Overgaard et al. 1997), and many stems intended for uncemented total hip arthroplasty (THA) are thus manufactured with HA coating. Several uncemented stems are only available with HA coating. Some HA-coated stems have excellent long-term outcomes in terms of the risk of revision, both for any reason and due to aseptic loosening (Capello et al. 2003, Shah et al. 2009). Registry data from Norway and Finland also indicate that certain HA-coated stems have excellent survivorship up to 10 years (Eskelinen et al. 2006, Hallan et al. 2007, Makela et al. 2008).On the other hand, a number of studies on stem survival in the setting of randomized trials or smaller observational studies have failed to show beneficial effects of HA coating on clinical outcome and implant survival when compared to alternatives such as porous coating and sand-blasted rough surfaces (McPherson et al. 1995, Tanzer et al. 2001, Kim et al. 2003, Parvizi et al. 2004, Sanchez-Sotelo et al. 2004). Meta-analyses that have pooled data from randomized or cohort studies have come to the conclusion that there is “[…] no clinically beneficial effect to the addition of HA to porous coating alone in primary uncemented hip arthroplasty” (Gandhi et al. 2009, Li et al. 2013). In addition, a Danish registry analysis found that the use of HA coating does not reduce the risk of stem revision (Paulsen et al. 2007). Furthermore, a comparison of 4,772 uncemented Bimetric stems with or without HA coating implanted between 1992 and 2009 did not reveal any difference in survival between the 2 variants (Lazarinis et al. 2011).HA was initially introduced as an implant coating to speed up and facilitate ongrowth and ingrowth of bone and thereby improve fixation, based on comprehensive preclinical and promising clinical documentation (Geesink et al. 1987, Bauer et al. 1991, Overgaard et al. 1997, Karrholm et al. 1998). Later on, concerns were raised due to findings of delamination and generation of HA particles originating from the coating with the potential to trigger osteolysis, acceleration of polyethylene wear, and subsequent implant loosening (Bloebaum and Dupont 1993, Morscher et al. 1998, Lazarinis et al. 2010). Today, there is renewed interest in HA coatings due to possible properties as a carrier for agents aimed at preventing infection (Ghani et al. 2012). Theoretical arguments for and against the use of HA coating can therefore be found. Given the renewed interest in uncemented stems—instigated by favorable outcomes after uncemented stem fixation in younger patients—the question of whether HA coating is beneficial or not is highly relevant (Eskelinen et al. 2006, Hooper et al. 2009, Swedish Hip Arthroplasty Register 2011). We therefore investigated uncemented stems with and without HA coating that are in frequent use in the Nordic countries, regarding early and long-term survival.     

The risk of revision due to dislocation after total hip arthroplasty depends on surgical approach, femoral head size, sex, and primary diagnosis: An analysis of 78,098 operations in the Swedish Hip Arthroplasty Register

Background and purpose

The effects of patient-related and technical factors on the risk of revision due to dislocation after primary total hip arthroplasty (THA) are only partly understood. We hypothesized that increasing the femoral head size can reduce this risk, that the lateral surgical approach is associated with a lower risk than the posterior and minimally invasive approaches, and that gender and diagnosis influence the risk of revision due to dislocation.

Patients and methods

Data on 78,098 THAs in 61,743 patients performed between 2005 and 2010 were extracted from the Swedish Hip Arthroplasty Register. Inclusion criteria were a head size of 22, 28, 32, or 36 mm, or the use of a dual-mobility cup. The covariates age, sex, primary diagnosis, type of surgical approach, and head size were entered into Cox proportional hazards models in order to calculate the adjusted relative risk (RR) of revision due to dislocation, with 95% confidence intervals (CI).

Results

After a mean follow-up of 2.7 (0–6) years, 399 hips (0.5%) had been revised due to dislocation. The use of 22-mm femoral heads resulted in a higher risk of revision than the use of 28-mm heads (RR = 2.0, CI: 1.2–3.3). Only 1 of 287 dual-mobility cups had been revised due to dislocation. Compared with the direct lateral approach, minimally invasive approaches were associated with a higher risk of revision due to dislocation (RR = 4.2, CI: 2.3–7.7), as were posterior approaches (RR = 1.3, CI: 1.1–1.7). An increased risk of revision due to dislocation was found for the diagnoses femoral neck fracture (RR = 3.9, CI: 3.1–5.0) and osteonecrosis of the femoral head (RR = 3.7, CI: 2.5–5.5), whereas women were at lower risk than men (RR = 0.8, CI: 0.7–1.0). Restriction of the analysis to the first 6 months after the index procedure gave similar risk estimates.

Interpretation

Patients with femoral neck fracture or osteonecrosis of the femoral head are at higher risk of dislocation. Use of the minimally invasive and posterior approaches also increases this risk, and we raise the question of whether patients belonging to risk groups should be operated using lateral approaches. The use of femoral head diameters above 28 mm or of dual-mobility cups reduced this risk in a clinically relevant manner, but this observation was not statistically significant.Dislocation remains a major problem after primary total hip arthroplasty (THA), and has a considerably negative effect on the quality of life after THA, especially if it is recurrent (Enocson et al. 2009b). Revision due to dislocation accounts for 9% of all revisions of primary THAs in the Swedish Hip Arthroplasty Register (SHAR), and it is therefore the second most common reason for revision after aseptic loosening (SHAR Annual Report 2010). An even higher proportion of revisions due to dislocation—of 26%—has been reported by the Australian National Joint Replacement Registry (2011). Most dislocations occur during the first postoperative year, and up to 50% take place within the first 3 months (Woo and Morrey 1982, Phillips et al. 2003, Meek et al. 2006). The Norwegian Joint Register reported that the number of revisions performed due to dislocation has increased over time, possibly related to changes in head sizes and surgical approaches during the study period (Fevang et al. 2010).Several factors have been proposed to influence the risk of dislocation, but many questions still remain unsolved (Meek et al. 2006). Various diagnoses such as femoral neck fracture (Conroy et al. 2008), the posterior approach to the joint, and small femoral head size of the prosthesis are parameters that have been identified as risk factors for dislocation (Furnes et al. 2001, Bystrom et al. 2003, Berry et al. 2005, Lachiewicz and Soileau 2006, Enocson et al. 2009b, Sariali et al. 2009, Ji et al. 2012).The use of dual-mobility cups, synonymously termed tripolar cups in primary THA, leads to a low risk of dislocation (Farizon et al. 1998, Philippot et al. 2009b, Bouchet et al. 2011, Boyer et al. 2012). Revision surgery of patients with recurrent dislocations by the use of dual-mobility cups has also shown promising results (Langlais et al. 2008, Philippot et al. 2009a).We studied the influence of both patient-related and surgical factors on the risk of revision due to dislocation in the Swedish Hip Arthroplasty Register. We hypothesized that age, sex, primary diagnosis underlying THA surgery, femoral head size, and surgical approach can affect the risk of revision due to dislocation. Furthermore, we specifically investigated the effects of dual-mobility cups on the risk of dislocation.