Long-term follow-up of metal-on-metal total hip replacement.

Metal-on-metal articulations were reintroduced to reduce polyethylene particle-induced osteolysis. Elevated serum metal levels have been detected at short- and intermediate-term follow-up. There is little knowledge about long-term effects of increased ionic metal generation. Our study was undertaken to provide information about long-term survival, clinical outcome, radiographic appearance, and serum metal concentrations after a minimum 10 years follow-up with a metal-on-metal hip prosthesis: 105 cementless primary total hip prostheses with metal-on-metal articulating surfaces were implanted in 98 patients with a mean age of 56 years. Clinical data, radiographs, and blood samples were obtained at a follow-up visit 10 years after implantation. Serum cobalt and chromium levels were determined with use of atomic absorption spectrometry. General laboratory analyses included a full blood count and kidney function parameters. The Harris score was 92 points and the UCLA score 6 points after 10 years. Small osteolytic lesions and radiolucent lines were found in Gruen's zones 1, 7, 8, and 14. The probability of survival was 98.6%. The median serum cobalt concentration of the 22 patients with their hip replacement as the only source of cobalt was 0.75 microg/L (range, 0.3-50.1 microg/L). No patient was diagnosed with renal insufficiency during the study period. Five patients were diagnosed with a malignancy between surgery and the follow-up. We do not have evidence of an increased rate of primary malignancies nor could we detect renal failure in our study group. Serum metal levels did not differ from short- and intermediate term follow-up values.     

Serum ion levels after ceramic‐on‐ceramic and metal‐on‐metal total hip arthroplasty: 8‐year minimum follow‐up

Alternative bearing surfaces for total hip arthroplasty, such as metal‐on‐metal and ceramic‐on‐ceramic, offer the potential to reduce mechanical wear and osteolysis. In the short and medium term, the second generation of metal‐on‐metal bearings demonstrated high systemic metal ion levels, whereas ceramic‐on‐ceramic bearings showed the lowest ones. We aimed to verify whether the long‐term ion release in metal‐on‐metal subjects was still relevant at a median 10‐year follow‐up, and whether a fretting process at the modular junctions occurred in ceramic‐on‐ceramic patients and induced an ion dissemination. Serum levels were measured in 32 patients with alumina‐on‐alumina implants (group A), in 16 subjects with metal‐on‐metal implants (group B), and in 47 healthy subjects (group C). Group B results were compared with medium‐term findings. Cobalt and chromium levels were significantly higher in metal‐on‐metal implants than in ceramic‐on‐ceramic ones and controls. Nevertheless, ion levels showed a tendency to decrease in comparison with medium‐term content. In ceramic‐on‐ceramic implants, ion values were not significantly different from controls. Both in groups A and B, aluminum and titanium release were not significantly different from controls. In conclusion, negligible serum metal ion content was revealed in ceramic‐on‐ceramic patients. On the contrary, due to the higher ion release, metal‐on‐metal coupling must be prudently considered, especially in young patients, in order to obtain definitive conclusions. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res     

Metal ion concentrations and semen quality in patients undergoing hip arthroplasty: A prospective comparison between metal‐on‐metal and metal‐on‐polyethylene implants

Purpose: The widespread usage of metal‐on‐metal (MoM) articulations in total hip arthroplasty (THA) has been tempered by concerns of increased metal ion production. The purpose of the study is to evaluate the influence of metal ion exposure on semen quality in young male patients undergoing THA. Methods: Male patients who were scheduled for unilateral THA and aged between 20 and 45 years were prospectively enrolled. Patients were sorted into MoM and metal‐on‐polyethylene (MoP) groups with equal case number. Semen and blood metal ion levels were measured and sperm analysis was performed before, 6 months after, and 1 year after surgery. Results: Compared to preoperative baseline, patients (n = 50) in both groups had increased cobalt (Co) and chromium (Cr) concentrations in blood and seminal fluid after surgery. Between‐group comparisons at 6 months and 1 year after surgery showed that patients in the MoM group both had a greater Co concentration in blood and semen and a greater Cr concentration in blood and semen. Patients receiving MoM prosthesis had a reduced percentage of morphologically normal sperm, and decreases from the preoperative level (44.7%) were significant at 6 months (36.8%, p = 0.03) and 1 year (33.8%, p = 0.004). Conclusions: Our data shows a significantly greater concentration of metal ion in blood and semen in patients with MoM prosthesis with a reduced percentage of morphologically normal sperm. Despite small effects on sperm quality, some concerns remain. Further studies are necessary to determine sources of metal ion and to investigate effects on male fertility. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:544–551, 2016.     

Predicting wear and blood metal ion levels in metal‐on‐metal hip resurfacing

Suboptimal component position and design are thought to lead to edge wear and raised blood metal ion levels in metal‐on‐metal hip resurfacing (MOM‐HR). These factors are thought to influence the “contact patch to rim distance” (CPRD), and calculation of this distance may improve prediction of wear and blood metal ion levels. We measured blood cobalt and chromium ion levels and the wear rates of the bearing surfaces in 165 MOM‐HR retrieval cases. We then determined the contribution and effect sizes of cup inclination and version angles, component size and design, and CPRD (calculated from case‐specific data) on blood metal ion levels and component wear rates. Acetabular orientation explained between 16.3% and 28.5% of the variation in wear rates and metal ion levels, whereas component size and design explained between 7.3% and 21.8% of the variability. In comparison, CPRD explained up to 67.7% of the variability, significantly greater than any other variable (all p < 0.0001). CPRD is a good predictor of wear and improves our understanding of wear performance and the mechanisms leading to edge loading. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:167–174, 2014.     

Asymptomatic prospective and retrospective cohorts with metal‐on‐metal hip arthroplasty indicate acquired lymphocyte reactivity varies with metal ion levels on a group basis

Some tissues from metal‐on‐metal (MoM) hip arthroplasty revisions have shown evidence of adaptive‐immune reactivity (i.e., excessive peri‐implant lymphocyte infiltration/activation). We hypothesized that, prior to symptoms, some people with MoM hip arthroplasty will develop quantifiable metal‐induced lymphocyte reactivity responses related to peripheral metal ion levels. We tested three cohorts (Group 1: n = 21 prospective longitudinal MoM hip arthroplasty; Group 2: n = 17 retrospective MoM hip arthroplasty; and Group 3: n = 20 controls without implants). We compared implant position, metal‐ion release, and immuno‐reactivity. MoM cohorts had elevated (p < 0.01) amounts of serum Co and Cr compared to controls as early as 3 months post‐op (Group 1:1.2 ppb Co, 1.5 ppb Cr; Group 2: 3.4 ppb Co, 5.4 ppb Cr; Group 3: 0.01 ppb Co, 0.1 ppb Cr). However, only after 1–4 years post‐op did 56% of Group 1 develop metal‐reactivity (vs. 5% pre‐op, metal‐LTT, SI > 2), compared with 76% of Group 2, and 15% of Group 3 controls (patch testing was a poor diagnostic indicator with only 1/21 Group 1 positive). Higher cup‐abduction angles (50° vs. 40°) in Group 1 were associated with higher serum Cr (p < 0.07). However, sub‐optimal cup‐anteversion angles (9° vs. 20°) had higher serum Co (p < 0.08). Serum Cr and Co were significantly elevated in reactive versus non‐reactive Group‐1 participants (p < 0.04). CD4+CD69+ T‐helper lymphocytes (but not CD8+) and IL‐1β, IL‐12, and IL‐6 cytokines were all significantly elevated in metal‐reactive versus non‐reactive Group 1 participants. Our results showed that lymphocyte reactivity to metals can develop within the first 1–4 years after MoM arthroplasty in asymptomatic patients and lags increases in metal ion levels. This increased metal reactivity was more prevalent in those individuals with extreme cup angles and higher amounts of circulating metal. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31: 173–182, 2013     

Lymphocyte proliferation responses in patients with pseudotumors following metal‐on‐metal hip resurfacing arthroplasty

Locally destructive soft tissue pseudotumor has been reported in patients following metal‐on‐metal hip resurfacing arthroplasty (MoMHRA). A delayed hypersensitivity reaction type IV to nickel (Ni), chromium (Cr), or cobalt (Co) has been suggested to play a role in its aetiology. The aim of this study was to investigate the incidence and level of metal‐induced systemic hypersensitivity in patients with MoMHRA, both with and without pseudotumor by measuring lymphocyte proliferation responses to metals. A total of 92 patients were investigated: (1) MoMHRA patients with pseudotumors (nine female, one male); (2) MoMHRA patients without pseudotumors (30 female, 30 male); and (3) age‐matched control subjects without metal implants (9 female, 13 male). The venous blood samples were collected for serum Ni, Co, and Cr ion level measurements and lymphocyte transformation tests (LTT). A higher incidence and level of enhanced lymphocyte reactivity only to Ni was found in patients with MoMHRA compared to the patients without MoM implants, reflecting exposure and immune reactivity. However, lymphocyte reactivity to Co, Cr, and Ni did not significantly differ in patients with pseudotumors compared to those patients without pseudotumors. This suggests that systemic hypersensitivity type IV reactions, as measured by lymphocyte proliferation response to these metals, may not be the dominant biological reaction involved in the occurrence of the soft tissue pseudotumors. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:444–450, 2010     

Strong association between smoking and the risk of revision in a cohort study of patients with metal‐on‐metal total hip arthroplasty

Thus far the ability to predict who will develop early failure following the insertion of a metal‐on‐metal (MoM) bearing has been very limited. Our objective was to assess the effect of smoking on failure rates in patients with MoM bearing, compared with patients with ceramic‐on‐polyethylene (CoP) bearing. From a prospective hospital‐based registry we included all primary THAs operated upon between 1/2001 and 12/2011 with MoM or CoP bearings of the same cup design and head size (28 mm). We compared revision rates through 10/2013 classified by smoking status and type of bearing. We included 1,964 patients (median age 71, 57% women), 663 with MoM and 1,301 with CoP bearing. Mean follow‐up was 6.9 years (range 1.8–12.8). Revisions were required for 56 THAs. In patients with MoM bearing the adjusted incidence rate of revision among ever‐smokers was four times greater than among never‐smokers (95% CI 1.4–10.9). Among those with CoP bearing, the rate ratio was only 1.3 (95% CI 0.6–2.5). We found a strong association between smoking and increased failure of MoM THAs. In contrast, the association was weak for patients with CoP bearing. Smoking might be a trigger or an effect amplifier for adverse reactions to metal debris from MoM bearings. © 2014 The Authors. Journal of Orthopaedic Research Published by Wiley Periodicals, Inc. J Orthop Res 32:762–768, 2014.     

Serum metal ion concentration: comparison between small and large head metal-on-metal total hip arthroplasty

The purpose of this study was to compare serum metal ion concentrations (chromium and cobalt) in 3 groups, 2 with metal-on-metal articulations and a control metal-on-polyethylene group. Forty-six patients with good to well-functioning hips were recruited for the study. Serum ion levels of all patients were drawn, and Harris Hip Score, University of California, Los Angeles activity score, and radiographs were performed. Serum chromium concentrations were significantly lower in the large head group compared with the small head group (P = .013). There was no difference in the cobalt concentrations between the 2 groups (P = .087). There was a significant difference between both metal-on-metal groups when compared with controls for both chromium and cobalt levels (P = .0005 and P = .0004, control vs small; P = .001 and P = .0001, control vs large, respectively).     

初次全髋关节置换术后5年以上随访结果

目的对本组行初次全髋关节置换术（THA）5年以上的患者进行临床及影像学随访,探讨其疗效、并发症及其影响因素。方法对北京协和医院骨科2006年以前行THA并具有完整临床资料的248例（285髋）患者进行临床及影像学随访。截至末次随访时,174例（198髋）获得随访,随访率为70.2%,随访时间平均为7.6年（5.5~11.6年）。临床随访包括术前术后Harris评分及各种并发症。影像学评估包括双侧髋关节正位（或骨盆正位）、患髋侧位片,判断人工假体位置、假体周围骨质以及并发症情况。结果术前Harris评分平均为34.4分（0~86分）,末次随访时平均为88分（35~99分）,优良率为88.5%。术后假体总的生存率为97.1%。术后并发症包括跛行（9例）、异位骨化（8髋）、脱位（7例）、假体松动（2例）和感染（3例）等。结论本组病例整体疗效满意、假体生存期长,随访率偏低、病例数偏少,因此有待于进一步随访。     

Material loss at the taper junction of retrieved large head metal‐on‐metal total hip replacements

It has been speculated that material loss, either as corrosion or wear, at the head–stem taper junction is implicated in the high revision rates reported for metal‐on‐metal total hip replacements. We measured the volume of material loss from the taper and bearing surfaces of retrieved devices, and investigated the associations with blood metal ion levels and the diagnosis of a cystic or solid pseudotumor. The median volumes of material lost from the female and male taper surfaces were 2.0 and 0.29 mm³, respectively, while the median volumes of wear from the cup and head bearing surfaces were 1.94 and 3.44 mm³, respectively. Material loss from the female taper was similar to that from the acetabular bearing surface (p = 0.55), but significantly less than that from the femoral bearing surface (p < 0.001). Material loss from the male taper was less than that from both bearing surfaces (p < 0.001). Multivariable analysis demonstrated no significant correlations between the volume of material lost from the taper surfaces and either blood cobalt or chromium ions, or the presence of pseudotumor. While a substantial volume of material is lost at the taper junction, the clinical significance of this debris remains unclear. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31:1677–1685, 2013     

Edge‐loading severity as a function of cup lip radius in metal‐on‐metal total hips—A finite element analysis

While favorable tribological properties and allowance for larger femoral head sizes have made metal‐on‐metal (MoM) bearings an increasingly popular choice for total hip arthroplasty, concerns have mounted regarding adverse reactions to metal wear debris and ions. MoM cups differ from conventional polyethylene cups in terms of edge profile design and reductions from full hemisphericity, suggesting differences in loading at or near the cup edge, especially during subluxation events. Finite element analysis was used to investigate the effects of cup orientation and lip edge curvature on damage propensity for edge or near‐edge loading during subluxation. Increased cup lip radius (resulting in reduced articular arc) had a detrimental effect upon subluxation‐free hip range of motion and upon dislocation resistance. Contact stresses near the cup edge demonstrated complex relationships between edge radius and cup orientation, with peak stresses being influenced by both variables. The tendency for scraping wear at the egress site demonstrated similarly complex dependencies. These data indicate that acetabular cup design is an important determinant of edge and near‐edge loading damage propensity. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 30:169–177, 2012     

A meta‐analysis of design‐ and manufacturing‐related parameters influencing the wear behavior of metal‐on‐metal hip joint replacements

This article aims to clarify the influence of design‐ and manufacturing‐related parameters on wear of metal‐on‐metal (MoM) joint bearings. A database search for publications on wear simulator studies of MoM bearings was performed. The results of published studies were normalized; groups with individual parameters were defined and analyzed statistically. Fifty‐six investigations studying a total of 200 implants were included in the analysis. Clearance, head size, carbon content, and manufacturing method were analyzed as parameters influencing MoM wear. This meta‐analysis revealed a strong influence of clearance on running‐in wear for implants of 36‐mm diameter and an increase in steady‐state wear of heat treated components. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1473–1480, 2009     

Shorter,rough trunnion surfaces are associated with higher taper wear rates than longer,smooth trunnion surfaces in a contemporary large head metal‐on‐metal total hip arthroplasty system

Taper wear at the head‐neck junction is a possible cause of early failure in large head metal‐on‐metal (LH‐MoM) hip replacements. We hypothesized that: (i) taper wear may be more pronounced in certain product designs; and (ii) an increased abductor moment arm may be protective. The tapers of 104 explanted LH‐MoM hip replacements revised for adverse reaction to metal debris (ARMD) from a single manufacturer were analyzed for linear and volumetric wear using a co‐ordinate measuring machine. The mated stem was a shorter 12/14, threaded trunnion (n = 72) or a longer, smooth 11/13 trunnion (n = 32). The abductor moment arm was calculated from pre‐revision radiographs. Independent predictors of linear and volumetric wear included taper angle, stem type, and the horizontal moment arm. Tapers mated with the threaded 12/14 trunnion had significantly higher rates of volumetric wear (0.402 mm³/yr vs. 0.123 mm³/yr [t = ?2.145, p = 0.035]). There was a trend to larger abductor moment arms being protective (p = 0.055). Design variation appears to play an important role in taper‐trunnion junction failure. We recommend that surgeons bear these findings in mind when considering the use of a short, threaded trunnion with a cobalt‐chromium head. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1868–1874, 2015.

     

Experimental validation of a pinless femoral reference array for computer‐assisted hip arthroplasty

The use of computer navigation systems during total hip arthroplasty requires the femoral fixation of a reflective dynamic reference base (DRB), which theoretically involves the risk of bony fracture, infection, and pin loosening. The first objective of this study was to evaluate the relative movements between a novel, noninvasive external femoral DRB system and the femur. Secondly, the maximum effects of these 3D movements on intraoperative, computer‐assisted leg length and offset measures were evaluated. An imageless navigation system was used to track the positions of the soft tissue attached, pinless DRB relative to an invasive reference marker on the femur during a less‐invasive, anterior surgical hip approach. Relative translatory movements up to 8.2 mm mediolaterally and up to 8.8° in rotation were measured. Using a measurement technique in which the calculation of leg length and offset changes is primarily based on a specific realignment of the leg, maximum differences of 1.3 mm for leg length and 1.2 mm for offset were found when comparing the pin‐based and pinless methods. Thus, invasive fixation techniques with screws or pins are still the method of choice when standard measurement algorithms for intraoperative leg length and offset measures are used. Though direct translatory and rotational variations between the pinless array and the femoral bone were detected, the pinless array can be used to assess leg length and offset when used with a specific measurement technique that compensates for such variations. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:583–588, 2010     

Differential distribution of cobalt,chromium, and nickel between whole blood,plasma and urine in patients after metal‐on‐metal (MoM) hip arthroplasty

Evidence shows that raised cobalt (Co), chromium (Cr), and nickel (Ni) whole blood concentrations correlate with poor device outcome in patients following metal‐on‐metal (MoM) hip arthroplasty. To understand the local and systemic pathological effects of these raised metal concentrations it is important to define their distribution between whole blood, plasma, and urine. The metals were measured by Inductively Coupled Plasma Mass Spectrometry (ICPMS). Two hundred and five plasma, 199 whole blood, and 24 sets of urine samples were analyzed from 202 patients with Co–Cr alloy MoM hip prostheses implanted between 8 months to 12 years (mean 6.0 years) prior to analysis. Plasma Co (median 39.1 nmol/L) showed significantly positive 1:1 correlation with whole blood Co (median 45.9 nmol/L; R² = 0.98, p < 0.001, slope = 1.0). Plasma Cr (median 53.8 nmol/L) and whole blood Cr (median 40.3 nmol/L) were also correlated; however, concentrations were significantly higher in plasma indicating relatively little blood cell uptake (R² = 0.96, p < 0.001, slope = 1.6). Urinary Co was up to threefold higher than Cr (median 334.0 vs. 97.3 nmol/L respectively). Nickel concentrations in whole blood, plasma, and urine were low relative to Co and Cr. The analysis shows fundamental differences in the physiological handling of these metals: Co is distributed approximately equally between blood cells and plasma, whereas Cr is mainly in plasma, despite which, Cr had far less renal excretion than Co. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:1640–1646, 2012     

A five‐year clinical and radiographic follow‐up of bipolar hip arthroplasty with insertion of a porous‐coated anatomic femoral component without cement

Objective: To evaluate the clinical and radiographic outcomes of bipolar hip arthroplasty with a cementless porous‐coated anatomic femoral component. Methods: Fifty‐nine patients (86 hips) with a minimum 3.5‐year follow‐up were followed up for a mean of 5.2 years (from January 2005 to January 2007). Standard clinical evaluation utilizing the Harris hip score and radiographic evaluation based on the criteria of the Hip Society were used in this prospective study. Radiographic assessment included evaluation of calcar remodeling and pedestal formation. Results: The average age of the patients (24 men and 35 women) at the time of surgery was 71.4 years (range, 69–84 years). The average preoperative Harris hip score was 48.5 ± 4.0 (range, 25–65) points, pain score 15.2 ± 3.9 (range, 0–20) points and functional score 26.7 ± 4.6 (range, 9–40) points. At the time of the latest follow‐up, the average Harris hip score was 96.1 ± 2.1 (range, 67–100) points, pain score 42.6 ± 6.3 (range, 32–54) points and functional score 45.5 ± 4.7 (range, 29–56) points. Five hips (5.81%) had pain in the anterior part of the thigh. Two hips (2.33%) required revision of the femoral component because of aseptic loosening and periprosthetic fracture. Radiographic assessment revealed consistent evidence of proximal bone ingrowth. No completely radiolucent lines were identified, except around stems that had loosened. Twenty‐seven femoral components (31.4%) had associated slight pedestal formation. No osteolytic lesions of the femur were identified. Nonprogressive pelvic osteolysis was identified in four hips, none of the lesions being ≥2 mm in diameter. Conclusion: An anatomically designed prosthesis can provide good clinical results, with low incidence of thigh pain and loosening of the component.