High long-term loosening rate of conical screw cups

Background Acetabular screw cups seem to give high primary stability. We analyzed the migration and loosening behavior of a first-generation screw cup in a longterm follow-up.

Patients and methods We examined 92 uncemented titanium alloy conical screw cups prospectively. Implant migration was assessed with a digital high-precision method (EBRA) with an accuracy of 1.0 mm.

Results After mean 11 (0.5-18) years, 87 patients were available for examination and 5 patients had died. 32 implants had been revised and 7 cases showed radiographic evidence of loosening. The 10-year survival rate was 71%. Migration of more than 1 mm occurred in 53 hips. Implant survival was strongly associated with an annual migration of greater than 0.2 mm.

Interpretation The long-term behavior of this cup is not satisfactory. In spite of extraordinarily high primary implant stability, secondary osseointegration of this cup often fails. The annual migration rate represents a valid parameter for prediction of implant survival.     

Effect of hydroxyapatite coating on risk of revision after primary total hip arthroplasty in younger patients: findings from the Danish Hip Arthroplasty Registry

Background The effect of hydroxyapatite (HA) on implant survival in the medium and long term is uncertain. We studied the effect of HA coating of uncemented implants on the risk of cup and stem revision in primary total hip arthroplasty (THA).

Patients and methods Using the Danish Hip Arthroplasty Registry (DHR), we identified patients less than 70 years old who had undergone uncemented primary THA during 1997-2005. 4,125 HA-coated and 7,737 non-HA-coated cups and 3,158 HA-coated and 4,749 non-HA-coated stems were available for analysis. The mean follow-up time was 3.4 years for cups and 3.2 years for stems. We estimated the relative risk (RR) of revision due to aseptic loosening or any cause, and adjusted for possible confounders (age, sex, fixation of opposite implant part, and diagnosis for primary THA) using multivariate Cox regression analysis.

Results The adjusted RRs for revision of HA-coated cups and stems due to aseptic loosening were 0.89 (95%CI: 0.37-2.2) and 0.71 (95%CI: 0.27-1.9) with up to 9 years of follow-up, compared to non-HA-coated implants. When taking all causes of revision into consideration, the risk estimates were 0.85 (95%CI: 0.68-1.1) and 0.81 (95%CI: 0.61-1.1) for HA-coated cups and stems, respectively.

Interpretation In this medium-term follow-up study, the use of HA-coated implants was not associated with any clearly reduced overall risk of revision compared to non-HA-coated implants.     

High osteolysis and revision rate with the hydroxyapatite-coated ABG hip prostheses

Background There are few reports on the outcome of uncemented HA-coated cups in young patients.

Patients I evaluated the 7-year (5-9) results of HA-coated hip prosthesis (ABG, Stryker) in a consecutive series of 65 primary arthroplasties on 56 patients (mean age 44 years). 2 patients were lost to follow-up and 3 died.

Results The cumulative survival rate with revision for any reason as endpoint at 9 years was 98% (95% CI, 96-100) for the stem, 69% (61-77) for the acetabular metal backing, and 59% (50-67) for the polyethylene liner. 15 of 65 cups were revised on average 6 years after the primary operation and 3 more are planned. Revisions were done in 3 hips because of loosening and migration of the cup, and in 12 hips because of wear and progressive osteolysis around stable components. Only hips with migration had clinical symptoms. Visual inspection of polyethylene liners revealed wear of the articulation in all cases, loosening of the locking mechanism in 10 cases and nonarticular surface deformity in 7 hips. All original stems are in situ although femoral osteolysis was seen in 12 cases and 1 hip was reoperated because of periprosthetic traumatic fracture. Despite the high revision rate, the clinical improvement was good: the average pre- and postoperative Harris Hip Scores at the most recent follow-up were 41 and 90, respectively.

Interpretation While the results on the femoral side were good, the survival rates of the acetabular cups were poor and we stopped using ABG I hip prostheses.     

Charnley low-frictional torque arthroplasty in young rheumatoid and juvenile rheumatoid arthritis: 292 hips followed for an average of 15 years

Introduction In the early 1960s, Charnley was cautious with his patient selection for total hip replacement. As follow-up increased and confidence in the operation grew, younger patients were selected. We present our results of the Charnley LFA in young patients with rheumatoid and juvenile rheumatoid arthritis with a followup of up to 36 years.

Patients We studied 292 Charnley low-friction arthroplasties in 195 young patients with an established diagnosis of rheumatoid arthritis. Their mean age at operation was 38 (12-50) years; 168 (58%) were receiving steroids and 79 (27%) were on non-steroidal antiinflammatory medication. The mean follow-up for the whole group was 15 (1-36) years. 24 patients could not be traced (33 hips), and 61 patients died (88 hips).

Results 25 patients (41 hips) had had a revision. The main indication for revision was cup loosening. In the 85 patients (130 hips) attending follow-up, their mean age at surgery was 36 (17-50) years and the mean follow-up was 20 (10-36) years. 98% were pain-free or had no more than occasional discomfort, 44% claimed to have normal or near-normal function, while 62% had full or almost full range of movement of the replaced hip. Radiographically, 29 cups (22%) were considered to be loose. 1 stem (1%) was definitely loose and 2 stems (2%) were probably loose. With revision for any indication as the endpoint, the survival was 74% at 25 years follow-up.

Interpretation The Charnley LFA continues to be an excellent hip replacement, even for very young rheumatoid arthritis patients. Wear and aseptic cup loosening are the main long-term problems.     

Uncemented Harris-Galante total hip arthroplasty in patients with osteonecrosis of the femoral head. A 10-16-year follow-up study

Background There have only been a few reports regarding the long-term results of uncemented THAs in patients with osteonecrosis.

Patients and methods We evaluated the long-term results of 65 consecutive uncemented total hip arthroplasties (Harris-Galante type I prostheses) in 54 men (59 hips) and 5 women (6 hips) with osteonecrosis of the femoral head. The mean age was 53 (33-64) years. The mean duration of follow-up was 12.5 (10-16) years.

Results 9 femoral stems and 3 acetabular metal shells were revised. 2 polyethylene liners were changed due to excessive wear. A girdlestone procedure was done in 2 patients (2 hips) due to delayed deep infection. The mean polyethylene wear was 0.14 mm per year. 3 non-revised hips had pelvic osteolysis and 18 had femoral osteolysis. The 15-year survival rates, using failure defined as the removal of any component for any reason, were 85 (95% CI; 79-91)% for the acetabular and 80 (74-86)% for the femoral component and 70 (63-77)% for any of the components.

Intepretation The first generation of the HGP design was frequently associated with pain, unstable fixation, and osteolysis. Excessive wear was frequent. The cup showed better durability than the stem.     

Different loss of BMD using uncemented press-fit and whole polyethylene cups fixed with cement: repeated DXA studies in 96 hips randomized to 3 types of fixation

Background In cemented THA, aseptic loosening of the cup is more common than loosening of the stem, while periprosthetic osteolysis of the socket resulting in difficult reconstruction problems has emerged as the most significant problem with cementless cup fixation.

Patients and methods 90 patients (96 hips) scheduled for THA were stratified in three groups according to the method of fixation of the acetabular component: acrylic bone cement with fluoride (Cemex-F), porous-coated press-fit cup with ceramic coating (Trilogy, uncemented) and acrylic cement with gentamicin (Palacos). All patients received the Spectron EF stem. Acetabular bone mineral density was measured with dual-energy X-ray absorptiometry (DXA) 1 week postoperatively, and after 12 and 24 months. The periprosthetic BMD was evaluated in 5 ROIs positioned around the acetabular component.

Results In the uncemented sockets, the BMD had decreased proximally and medially to the cup after 2 years. The difference was significant in the proximal region as compared to the control group (Palacos). No difference was noted between the 2 groups with cemented components after 2 years. Stepwise linear regression analysis showed that loss of periprosthetic BMD in the proximal high-pressure region after 2 years increased with higher postoperative BMD and when the uncemented design had been used.

Interpretation Contrary to previous studies of cemented stems, the use of fluoride cement did not influence the periprosthetic BMD 2 years after the examination. Increased loss of BMD with use of uncemented press-fit cups in the region in which osteolytic lesions are commonly found suggests that stress shielding may initiate the development of this complication. Longer follow-up will, however, be necessary to substantiate this hypothesis.     

No difference in migration or wear between cemented low-profile cups and standard cups : a randomized radiostereographic study of 53 patients over 3 years

Background Minor design changes may cause major changes in implant performance. Thus, as part of a stepwise introduction of a new low-profile cup, we performed a randomized trial comparing it to a well-docu-mented standard cup.

Patients and methods 60 patients, stratified according to sex, weight, and age, underwent cemented total hip arthroplasty using a Lubinus SP2 stem with ceramic head and were randomized to either the new low-profile Lubinus Flanged Anti-Luxation cup (FAL) or the Lubinus Standard Eccentric cup (Standard). 7 patients were excluded and 53 (28 FAL) were evaluated at 3, 6, 12, and 36 months postoperatively. Primary outcome variables, cup migration (MTPM), and wear (total 3-dimensional femoral head penetration) were measured with radiostereometry (RSA). Clinical outcome was evaluated with the western Ontario and McMaster osteoarthritis index (Womac) and the visual analog pain score (VAS).

Results We found no difference in migration between the FAL and Standard cups. There was no difference in wear between the two cups and there was no correlation between wear and migration. 3 cups (2 FAL and 1 Standard) showed continuous migration of a magnitude that indicated an increased risk of early loosening. Clinical outcome was excellent, without any difference between the 2 groups.     

The effect of middle-age body weight and physical activity on the risk of early revision hip arthroplasty: a cohort study of 1,535 individuals

Background Overweight and a high level of physical activity are known risk factors for loosening of a total hip arthroplasty (THA) due to primary osteoarthritis. We wanted to investigate how these factors, together with age and sex, affect the risk of revision surgery.

Patients and methods We matched data from the Norwegian Arthroplasty Register with information on risk factors collected at a cardiovascular screening. We identified 1,535 primary THAs in the screened cohort (930 cemented implants using well-documented cement). Of the participants included, 969 were female. Mean age at screening was 49 years, at primary THA 63 years, and 69 years at the end of follow-up. We used Cox regression analysis to estimate relative risks (RRs). Event was defined as implant revision due to aseptic loosening of cup, stem or both. Follow-up was time from primary THA to event or censoring.

Results Men were at greater risk than women of loosening of the femoral stem (RR 2.0, 95% CI 1.3-3.2). Both men and women with upper-quartile body weight were at increased risk of revision due to loosening of the stem (RR 2.5 and 2.7, respectively). Men with a high level of physical activity during leisure time were at increased risk of revision due to loosening of the cup (RR 4.8, 95% CI 1.3-18). In the multivariate model with adjustment for activity, there was little association between age at primary THA and risk of revision due to loosening.

Interpretation We found that body weight and physical activity recorded long before THA affected the survival of total hip arthroplasties. Controlling for these variables weakened the association between age at primary surgery and aseptic loosening. Men had an increased risk of loosening of the femoral stem, also after controlling for lifestyle factors.     

Cementless Spotorno tapered titanium stems

We evaluated the clinical and radiographic results of the first consecutive 154 implantations of a cementless, double-tapered straight femoral stem (cementless Spotorno (CLS), Sulzer Orthopedics) in 141 patients under the age of 55 (mean 47 (13-55)) years. After a mean follow-up of 12 (10-15) years, 11 patients (11 hips) had died and 7 (7 hips) could not be located. 5 patients (5 hips) underwent femoral revision—1 for infection, 1 for periprosthetic fracture and 3 for aseptic loosening of the stem. The overall survival rate of the stem was 97% at 12 years (95% confidence limits, 93%-100%), and survival with femoral revision for aseptic loosening as an end point 98 (95-100)%. The survival rate of the acetabular components was 78 (71-85) % after 12 years. The median Harris hip score at follow-up was 84 points. None of the patients had thigh pain. Radiolucent lines in Gruen regions 1 and 7 were present in 21 hips (17%). 2 hips had radiolucent lines in regions 2-6 on anteroposterior (AP) radiographs. No femoral osteolysis was detected.

The mid- to long-term survival with this type of femoral component is excellent and compares favorably with cemented stems in this age group. However, the high rate of cup loosening and the low Harris hip scores are a concern in this subgroup of young patients.     

Uncemented acetabular components with bulk femoral head autograft for acetabular reconstruction in developmental dysplasia of the hip: results at five to twelve years.

BACKGROUND: Anterolateral acetabular bone deficiency is one of the technical problems associated with total hip arthroplasty in patients with developmental hip dysplasia. The purpose of this study was to evaluate the results of one method of acetabular reconstruction for hip dysplasia-placement of an uncemented socket in conjunction with a bulk femoral head autograft. METHODS: Forty-four hips in thirty-five patients (twenty-nine female and six male; average age, thirty-nine years) with developmental hip dysplasia were treated with primary total hip arthroplasty with use of an uncemented porous-coated titanium cup fixed with screws and an autogenous bulk femoral head graft. The patients were followed clinically in a prospective fashion for five to 12.3 years (mean, 7.5 years), and radiographs were analyzed retrospectively. RESULTS: Four acetabular components were revised: two, because of severe polyethylene wear and osteolysis; one, because of aseptic loosening; and one, because of fracture of the acetabular shell. The mean Harris hip score for the unrevised hips improved from 51 points preoperatively to 91 points postoperatively. No unrevised socket had definite radiographic evidence of loosening. Forty-three of the forty-four hips had no radiographic evidence of resorption of the graft or had radiographic evidence of resorption limited to the nonstressed area of the graft lateral to the edge of the cup. CONCLUSIONS: This method of reconstruction provided reliable acetabular fixation and appeared to restore acetabular bone stock in patients with developmental hip dysplasia. We use this technique for patients with moderate anterolateral acetabular bone deficiency requiring total hip arthroplasty.     

Plasma levels of platelet-derived growth factor BB and transforming growth factor in patients with failed hip prostheses

Background The role of growth factors in prosthesis loosening is unclear. We evaluated the levels of plate-let-derived growth factor BB (PDGF-BB), transforming growth factors β1 (TGF-β1) and β2 (TGF-β2), both before and after activation, in patients with aseptic loosening of their hip prosthesis.

Patients and methods 26 patients with loosened hip implants were compared with 21 patients who had stable hip prostheses, and 28 patients undergoing primary hip replacement. The plasma levels of the growth factors were analyzed by enzyme immunoassay. TGF-β1 and TGF-β2 were determined both before and after activation.

Results Patients with aseptic loosening had significantly lower PDGF-BB levels than patients undergoing primary hip replacement, and significantly lower TGF-β2 levels than patients with a stable implant. Patients with stable prostheses had significantly higher TGF-β1 and TGF-β2 levels than patients undergoing primary hip replacement.

Interpretation It is possible that the prosthetic implant itself causes a local increase in PDGF-BB, TGF-β1 and TGF-β2, released by osteoblasts and other cells in the microenvironment. The plasma PDGF-BB measured does not correspond to local release, which is probably due to local consumption or degradation. The consumption of PDGF-BB is low in stable implants, and TGF-β1 and TGF-β2 levels increase during bone formation. In loosening, PDGF-BB consumption is higher and causes a significant reduction in plasma levels as compared to presurgery. The formation of poor-quality bone may be related to the scarce increase in TGF-β1 and TGF-β2. In conclusion, compared with patients with a stable implant, a reduction in bone-forming growth factors appears to occur in individuals with aseptic loosening.     

Comparison of analog and digital preoperative planning in total hip and knee arthroplasties. A prospective study of 173 hips and 65 total knees

Introduction Digital correction of the magnification factor is expected to yield more accurate and reliable preoperative plans. We hypothesized that digital templating would be more accurate than manual templating for total hip and knee arthroplasties.

Patients and methods Firstly, we established the interobserver and intraobserver reliability of the templating procedure. The accuracy and reliability of digital and analog plans were measured in a series of 238 interventions, which were all planned using both techniques.

Results Interobserver reliability was good for the planning of knee arthroplasties (κ-values 0.63-0.75), but not more than moderate for the planning of hip arthroplasties (κ-values 0.22-0.54). Analog plans of knee arthroplasties systematically underestimated the component sizes (1.1 size on average), while the digital procedure proved to be accurate (0.1-0.4 size too small on average). The following figures show percentage of cases receiving a correct implant, allowing an error of one size. Digital templating of the hip arthroplasty was less frequently correct (cemented cup and stem: 72% and 79%; uncemented cup and stem: 52% and 66%) than analog planning (cemented cup and stem: 73% and 89%; uncemented cup and stem: 64% and 52%).

Interpretation Planning of component sizes for total knee arthroplasties is an accurate procedure when performed digitally. Our digital preoperative plans which were performed by someone other than the surgeon were less accurate than the analog plans prepared by the surgeon.     

Extra-large uncemented hemispherical acetabular components for revision total hip arthroplasty

BACKGROUND: Extra-large uncemented components provide several advantages for acetabular revision, but limited information is available on the results of their use. The purpose of this study was to evaluate, at a minimum of five years, the results associated with the use of an extra-large uncemented porous-coated component for acetabular revision in the presence of bone loss. METHODS: Eighty-nine extra-large uncemented hemispherical acetabular components were used for revision after aseptic failure of a total hip arthroplasty in forty-six men and forty-three women (mean age at revision, fifty-nine years; range, thirty to eighty-three years). The revision implant (a Harris-Galante-I or II cup fixed with screws) had an outside diameter of > or = 66 mm in men and > or = 62 mm in women. Seventy-nine patients had a segmental or combined segmental and cavitary acetabular bone deficiency before the revision. Particulate bone graft was used in fifty-four hips and bulk bone graft, in nine. RESULTS: One patient died with the acetabular component intact and two patients were lost to follow-up within five years after the operation. At the time of the last follow--up, four acetabular components had been removed or revised again (two for aseptic loosening). All of the remaining patients were followed clinically for at least five years (mean, 7.2 years; range, 5.0 to 11.3 years). In the hips that were not revised again, only two sockets had definite radiographic evidence of loosening. All four of the sockets that loosened were in hips that had had combined cavitary and segmental bone loss preoperatively. In the hips that were not revised again, the mean modified Harris hip score increased from 56 points preoperatively to 83 points at the time of the most recent follow-up. The most frequent complication, dislocation of the hip, occurred in eleven patients. The probability of survival of the acetabular component at eight years was 93% (95% confidence interval, 85% to 100%) with removal for any reason as the end point, 98% (95% confidence interval, 92% to 100%) with revision for aseptic loosening as the end point, and 95% (95% confidence interval, 88% to 100%) with radiographic evidence of loosening or revision for aseptic loosening as the end point. CONCLUSIONS: This study demonstrates that extra-large uncemented components used for acetabular revision in the presence of bone loss perform very well and have a low rate of aseptic loosening at the time of intermediate-term follow-up.     

Socket wall addition device in the treatment of recurrent hip prosthesis dislocation: good outcome in 12 patients followed for 4.5 (1-9) years

Background Recurrent dislocation in total hip replacement is difficult to treat and causes severe morbidity.

Patients and methods 12 patients suffering dislocations were reoperated with a socket wall addition device (anti-luxation ring) for the Lubinus SPII prosthesis, and were followed up after a mean of 4.5 (1-9) years with regard to redislocation, function and radiographic loos-ening.

Results 1 of the patients suffered a redislocation after almost 7 years of use. There was no loosening during the follow-up time. A Harris hip score of 87 (60-100), a health-related quality of life (EQ-5D) index of 0.8 (0.6-1.0) and total range of motion of 145° (125-165) indicate that the patients had a level of function comparable to that of age-matched hip surgery patients with no com-plications.

Interpretation The anti-luxation ring shows promising mid-term results and seems to provide an alternative to more extensive revision surgery for selected patients. ▪     

Radiolucent lines and osteolysis along tapered straight cementless titanium hip stems: a comparison of 6-year and 10-year follow-up results in 95 patients

Background The progress of radiolucent lines (RLs) around the stems of cementless hip endoprostheses and their implications for implant survival are unclear.

Patients and methods 150 consecutive total hip replacements (THRs) were performed between January and July 1993. The presence and development of RLs and osteolyses were monitored with a standardized special radiographic technique, and the results were compared at 6 and 10 years of follow-up in 95 patients.

Results At 6 years, RLs were detectable in 43 of 95 patients. RLs with an extension of 50% of the respective zone were present in 35 patients, almost all in Gruen zones 1 and 7. 2 patients presented with osteolysis. At 10 years, the RLs were almost identical—both in number and thickness. Only 1 additional osteolytic lesion had developed; no cup osteolyses were detected, and there was no significant polyethylene wear.

Interpretation The RLs detected at 6 years were virtually unchanged at 10 years. As they did not progress, they would not jeopardize implant stability. However, the osteolyses seen in 3 patients emphasize the importance of follow-up examinations.     

High survival in young patients using a second generation uncemented total hip replacement

Purpose

Whilst excellent long-term results with contemporary uncemented stems have been reported for total hip arthroplasty in young patients, the survival rates for the whole reconstruction are often compromised by high failure rates on the acetabular site due to peri-acetabular osteolysis and accelerated wear.

Methods

In patients 60 years old or younger, we retrospectively reviewed the results at a minimum of ten years of 89 consecutive uncemented total hip replacements in 88 patients using the press-fit Fitmore acetabular component in combination with the CLS Spotorno stem and a 28-mm Metasul metal-on-metal articulation or a 28-mm alumina ceramic on conventional polyethylene bearing. The mean age at the time of surgery was 49 years (range, 25–60). The mean clinical and radiological follow-up was 12 years (range, 10–15).

Results

Six patients (six hips) died and two patients (two hips) were lost to follow-up. Five hips were revised: one for deep infection, one for peri-prosthetic femoral fracture, and one for aseptic stem loosening. In two hips an isolated revision of the acetabular liner was performed (one for recurrent dislocation and one for unexplained pain). No revision was performed for accelerated wear, osteolysis or aseptic loosening of the acetabular shell. We could not detect peri-acetabular osteolysis visible on plain radiographs in those hips evaluated radiographically. The Kaplan-Meier survival with revision for any reason as the endpoint was 94% (95% confidence interval, 86–97) at 12 years.

Conclusions

The survival rates and the radiological outcomes with this implant combination in this young and active patient group are encouraging when compared to the results reported for other uncemented cups in this age group.     

Stepwise introduction of a bone-conserving osseointegrated hip arthroplasty using RSA and a randomized study: II. Clinical proof of concept--40 patients followed for 2 years

Background We have developed a bone-conserving commercially pure titanium hip replacement system using osseointegration principles: a metaphyseal loading proximal femoral component affixing into the retained neck and metaphysis only, leaving the femoral canal untouched. The acetabular cup closely fits a dual-geometry cavity, avoiding stress protection at the dome.

Patients and methods After extensive laboratory and clinical pilot trial investigations, the surface-engineered implants were submitted to a prospective randomized controlled clinical trial involving 40 patients (40 hips), in which they were compared to the cemented Spectron femoral component and cementless Trilogy cup as control implant. The following clinical measures were used to monitor progress at regular intervals for the first 2 postoperative years: radiostereometric analysis (RSA), Harris Hip Score, pain score, WOMAC, and SF-36.

Results After 2 years of follow-up, no statistically significant differences were seen between the groups concerning rotation or translation along the cardinal axes. The patients receiving the Gothenburg osseointegrated titanium (GOT) system had significantly higher Harris Hip Score at 6 months, suggesting more rapid recovery. WOMAC, SF-36 and pain analysis were similar for the first 2 postoperative years.

Interpretation Our RSA data suggest that osseointegration was achieved for all patients receiving the GOT hip system. This bone-conserving prosthesis may provide a good alternative, especially for young and active patients.     

Radiographic and clinical analysis of cementless acetabular fixation in total hip arthroplasty

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Early clinical and radiographic analysis of the Fitmore cup

The Fitmore titanium mesh cementless acetabular component in 115 hip arthroplasties was reviewed at an average of 33 months of follow-up. None were revised nor had infection. One hip dislocated 4 years postoperatively. Two femoral components were revised. The average Harris Hip Score at the last follow-up was 90 points. In the 96 sets of radiographs available, there was no loosening or new radiolucency. One hip had nonprogressive osteolysis adjacent to a screw. This press-fit cup has its polar region flattened and is rim loading. Noncontact (gaps) at the acetabular floor is expected and is not critical for fixation. In all but 6 hips, these gaps filled. In 5 hips, a minimal gap (相似文献   

Inflammatory response in 85 patients with loosened hip prostheses: a prospective study comparing inflammatory markers in patients with aseptic and septic prosthetic loosening

Background The most common complications of prosthetic hip joints are aseptic mechanical failure and infection. Delayed low-grade infections are seen most often, and they are also most difficult to distinguish from aseptic mechanical failures.

Methods We conducted a prospective study to compare inflammatory markers in patients diagnosed with aseptic or septic prosthetic loosening. The diagnostic criteria were based on the decisions of experienced orthopedic surgeons and microbiological analysis of periprosthetic tissue samples taken perioperatively.

Results Coagulase-negative staphylococci were the commonest pathogens in the infected patients. Pre- or perioperative elevation of C-reactive protein and erythrocyte sedimentation rate were significantly greater in the infection group, as were white blood cell count and levels of cytokines in synovial fluid. The patterns of infiltration of inflammatory cells in periprosthetic tissue were also significantly different between the groups.

Interpretation A combination of clinical judgment and multiple tissue samples constitutes a good platform for distinguishing between septic and aseptic loosening of prostheses. Moreover, the combined use of several laboratory and histopathological markers of inflammation, especially infiltration of polymorphonuclear cells, further helps the diagnosis.