Long-term results of revision total hip arthroplasty with a cemented femoral component.

INTRODUCTION: In revision total hip arthroplasty (THA), the cancellous bone is normally completely removed out of the femoral canal during stem extraction. This situation is comparable to primary THA following the shape-closed concept, with some authors advocating to remove the metaphyseal cancellous bone to enhance press-fit stability ("French paradox"). The aim of this study was to investigate the long-term outcome, regarding survival and radiological results, of a cemented straight stem when used for revision THA and to compare these results to the results of the same stem in primary THA. MATERIALS AND METHODS: 178 stem revisions performed between 01/1994 and 08/2008 using the Virtec straight stem were included. The cumulative incidence for re-revision was calculated using a competing risk model. Risk factors for re-revision of the stem were analyzed using an absolute risk regression model. Radiographs analyzed for osteolysis, debonding and subsidence had a minimum follow-up of 10 years. RESULTS: The cumulative incidence for re-revision due to aseptic loosening of the stem was 5.5% (95% CI, 2.9-10.2%) at 10 years. Aseptic loosening was associated with younger age, larger defect size and larger stem size. After a minimum 10-year follow-up, osteolysis was seen in 39 of 80 revision THA. Compared to the results in primary THA, the survival in revision THA with the same implant was inferior. CONCLUSIONS: Cemented straight stems used for revision THA showed excellent long-term results regarding survivorship and radiological outcome. This stem therefore offers a valuable and cost-effective option in revision THA.

Long-term survival of the cemented Müller CDH stem: a minimum follow-up of 10 years.

INTRODUCTION: Total hip arthroplasty in patients with altered anatomy of the hip and femur, such as in congenital dysplasia of the hip, is challenging and often requires specially designed stems. Müller straight stems have shown excellent long-term results; however, long-term data on the analogous cemented Müller CDH stem are still missing. The aim of this study was to analyze long-term survival, identify potential risk factors for aseptic loosening, and analyze radiological outcome of the cemented Müller CDH stems. MATERIALS AND METHODS: Between 01/1985 and 06/2005, 95 Müller CDH stems (Zimmer, Winterthur, Switzerland) made up of 3 different materials were cemented using 2 different bone cements: 38 of stainless steel/high-viscosity cement, 31 of a cobalt-chrome-based alloy (CoCr)/low-viscosity cement, and 26 of a titanium-based alloy (Ti)/low-viscosity cement. All patients had a prospective clinical and radiological follow-up according to the standards of our institution. The cumulative incidence for revision of the stem was calculated using a competing risk model. To identify demographic and implant-related risk factors for aseptic loosening of the stem, a multivariate regression model for competing risks was performed. RESULTS: The cumulative risk of revision at 15 years was 12.5% (95% CI 6.6-20.5%) for aseptic loosening of the stem as endpoint, with marked differences for the various stem materials used: stainless steel 2.7% (0.2-12.3%), CoCr 12.9% (4.0-27.3%), and Ti 24.5% (9.6-43.1%). Regression modeling revealed that Ti stems in combination with low-viscosity cement (HR 10.2) and implantation with an axis deviation greater than 3° (HR 3.8) are risk factors for aseptic loosening. CONCLUSIONS: Long-term survival of the cemented Müller CDH stem is comparable to other Müller-type straight stems and uncemented implants. Similar to the original Ti Müller straight stem, the Ti Müller CDH stem also showed an increased risk for aseptic loosening and should, therefore, no longer be used.

Excellent long-term results of the Müller acetabular reinforcement ring in primary cup revision.

Background and purpose - The original Müller acetabular reinforcement ring (ARR) was developed to be used for acetabular revisions with small cavitary and/or segmental defects or poor acetabular bone quality. Long-term data for this device are scarce. We therefore investigated long-term survival and radiographic outcome for revision total hip arthroplasty using the ARR. Patients and methods - Between October 1984 and December 2005, 259 primary acetabular revisions using an ARR were performed in 245 patients (259 hips). The mean follow-up time was 10 (0-27) years; 8 hips were lost to follow-up. The cumulative incidence for revision was calculated using a competing risk model. Radiographic assessment was performed for 90 hips with minimum 10 years' follow-up. It included evaluation of osteolysis, migration and loosening. Results - 16 ARRs were re-revised: 8 for aseptic loosening, 6 for infection, 1 for suspected infection, and 1 due to malpositioning of the cup. The cumulative re-revision rate for aseptic loosening of the ARR at 20 years was 3.7% (95% CI 1.7-6.8%). Assuming all patients lost to follow-up were revised for aseptic loosening, the re-revision rate at 20 years was 6.9% (95% CI 4.1-11%). The overall re-revision rate of the ARR for any reason at 20 years was 7.0% (95% CI 4.1-11%). 21 (23%) of the 90 radiographically examined ARR had radiographic changes: 12 showed isolated signs of osteolysis but were not loose; 9 were determined loose on follow-up, of which 5 were revised. Interpretation - Our data suggest that the long-term survival and radiographic results of the ARR in primary acetabular revision are excellent.

Eradication of infection, survival, and radiological results of uncemented revision stems in infected total hip arthroplasties.

Background and purpose - The use of uncemented revision stems is an established option in 2-stage procedures in patients with periprosthetic joint infection (PJI) after total hip arthroplasty (THA). However, in 1-stage procedures, they are still rarely used. There are still no detailed data on radiological outcome after uncemented 1-stage revisions. We assessed (1) the clinical outcome, including reoperation due to persistent infection and any other reoperation, and (2) the radiological outcome after 1- and 2-stage revision, using an uncemented stem. Patients and methods - Between January 1993 and December 2012, an uncemented revision stem was used in 81 THAs revised for PJI. Patients were treated with 1- or 2-stage procedures according to a well-defined algorithm (1-stage: n = 28; 2-stage: n = 53). All hips had a clinical and radiological follow-up. Outcome parameters were eradication of infection, re-revision of the stem, and radiological changes. Survival was calculated using Kaplan-Meier analysis. Radiographs were analyzed for bone restoration and signs of loosening. The mean clinical follow-up time was 7 (2-15) years. Results - The 7-year infection-free survival was 96% (95% CI: 92-100), 100% for 1-stage revision and 94% for 2-stage revision (95% CI: 87-100) (p = 0.2). The 7-year survival for aseptic loosening of the stem was 97% (95% CI: 93-100), 97% for 1-stage revision (95% CI: 90-100) and 97% for 2-stage revision (95% CI: 92-100) (p = 0.3). No further infection or aseptic loosening occurred later than 7 years postoperatively. The radiographic results were similar for 1- and 2-stage procedures. Interpretation - Surgical management of PJI with stratification to 1- or 2-stage exchange according to a well-defined algorithm combined with antibiotic treatment allows the safe use of uncemented revision stems. Eradication of infection can be achieved in most cases, and medium- and long-term results appear to be comparable to those for revisions for aseptic loosening.

Similar effect of stem geometry on radiological changes with 2 types of cemented straight stem: The Müller stem and the Virtec stem compared in 711 hips.

BACKGROUND AND PURPOSE: There are 2 basic principles in cemented stem fixation: shape-closed and force-closed. We investigated 2 shape-closed straight stems, the Müller (MSS) and the Virtec (VSS), which differ only in geometrical cross section, to determine whether the difference in stem shape would affect the radiological results or long-term survival. PATIENTS AND METHODS: We included 711 hips (in 646 patients) that were operated on between July 1996 and July 2003. Patients randomly received either an MSS (n = 356) or a VSS (n = 355) and were followed prospectively. Radiographs taken at a follow-up of > 10 years were analyzed for osteolysis. Kaplan-Meier (KM) survival analysis was performed using various endpoints. We also performed Cox regression analysis to identify risk factors for aseptic loosening and osteolysis of the stem. RESULTS: After 10 years, KM survival with "revision of any component for any reason" was 92% (95% CI: 88-95) for the MSS and 95% (CI: 92-97) for the VSS (p = 0.1). With "revision for aseptic loosening of the stem" as the endpoint, KM survival was 96% (CI: 9-98) for the MSS and 98% (CI: 97-100) for the VSS (p = 0.2). Cox regression showed that none of the risk factors analyzed were independent regarding aseptic loosening of the stem or regarding osteolysis. INTERPRETATION: The MSS and the VSS showed excellent survival for aseptic loosening after 10 years. For the 2 different stem designs, we did not find any independent risk factors for aseptic loosening or development of osteolysis.

Influence of leg length discrepancy on clinical results after total hip arthroplasty--a prospective clinical trial.

The effect of leg length differences on early clinical outcome after total hip arthroplasty remains uncertain. We performed a prospective study on 94 patients who were evaluated preoperatively and one year after surgery for clinical leg length differences, which were then compared with radiological measurements. The effect of leg length differences on walking ability, limp, pain and patient satisfaction was studied. The mean clinical leg length difference after operation was 0.05 cm (-1.5 to 1.5, SD 0.5). Clinical and radiological measurements correlated poorly (ω =0.36 pre- and ω =0.186 postoperatively). Patients with a shorter operated leg on clinical assessment were more prone to limping (p<0.05), and patients with a longer leg had more pain compared to patients with equal leg lengths (p<0.05). Walking ability, Harris Hip Score and patient satisfaction were only marginally affected by leg length differences. Virtually equal leg length was achieved for most patients but small differences had a negative influence in relation to limping and pain. Patients should be counselled pre-operatively about possible leg length differences and associated symptoms.

Infectiological, functional, and radiographic outcome after revision for prosthetic hip infection according to a strict algorithm.

BACKGROUND AND PURPOSE: Successful treatment of prosthetic hip joint infection (PI) means elimination of infection and restored hip function. However, functional outcome is rarely studied. We analyzed the outcome of the strict use of a treatment algorithm for PI. PATIENTS AND METHODS: The study groups included 22 hips with 1-stage exchange for PI (group 1), 22 matched hips revised for aseptic loosening (controls), and 50 hips with 2-stage exchange (group 2). Relapse of infection, Harris hip score (HHS), limping, use of crutches, reoperations, complications, and radiographic changes were compared between the groups. RESULTS: There was 1 relapse of infection, which occurred in group 2. In group 1, the mean HHS was 84; 4 of 19 patients were limping and 2 required 2 crutches, which was similar to the control results. In group 2, scores were lower and complication rates higher. The use of a Burch-Schneider ring and the presence of a deficient trochanter impaired function. There were no differences in radiographic outcome between the groups. INTERPRETATION: With the algorithm used, infection can be cured with high reliability. With a 1-stage procedure, mobility is maintained. After 2-stage procedures, function was impaired due to there being more previous surgery and more serious infection.

Classification of acetabular changes in osteoarthritis: a histological and radiological analysis of 122 consecutive drill biopsies routinely taken during THA.

BACKGROUND: Aseptic acetabular loosening cannot be explained with a single theory and lots of studies deal with the influence of implant design and surgical technique on implant survival. Implant registers show the effect of demographic and patient-related parameters on acetabular loosening. There is little information about the influence of the acetabular bone quality on cup loosening. METHODS: In a prospective study, we investigated the first 122 consecutive routinely taken biopsies out of acetabular bone stock taken during primary total hip arthroplasty (THA) before reaming of the cup. Undecalcified bone samples should be classified in respect to architecture and vitality in different histological types. Four types were defined and the primary diagnosis and the severity of the preoperative radiological changes were correlated to this classification. RESULTS: A total number of 110 (90%) out of 122 biopsies could be classified to one specific type of biopsy, nine were not classifiable and three showed special entities [rheumatoid arthritis (RA) and coxitis]. Double examination showed a high intraobserver agreement (kappa 0.972). There was a correlation between the four defined types of bone biopsies and the radiological severity of osteoarthritis (P<0.0001) but not with the diagnosis (P=0.104). CONCLUSION: Histological changes during the development of osteoarthritis of the hip occur regularly, can be classified in four groups and are predictable from radiological changes on preoperative radiographs.

Patient and surgery related factors associated with fatigue type polyethylene wear on 49 PCA and DURACON retrievals at autopsy and revision.

BACKGROUND: Polyethylene wear is an important factor for longevity of total knee arthroplasty. Proven and suspicious factors causing wear can be grouped as material, patient and surgery related. There are more studies correlating design and/or biomaterial factors to in vivo wear than those to patient and surgery related factors. Many retrieval studies just include revision implants and therefore may not be representative. This study is aimed to correlate patient- and surgery- related factors to visual wear score by minimizing design influence and include both autopsy and revision implants. Comparison between the groups was expected to unmask patient and surgery-related factors responsible for wear. METHODS: The amount of joint side wear on polyethylene retrievals was measured using a modification of an established visual wear score. Fatigue type wear was defined as summation of the most severe wear modes of delamination, pitting and cracks. Analysis of patient and surgery related variables suspicious to cause wear included prospectively sampled patient activity which was measured by self reported walking capacity. Statistical analysis was done by univariate analysis of variance. Activity level and implantation time were merged to an index of use and correlated to the wear score. RESULTS: Wear score after comparable implantation time was significantly less in the autopsy group. Even so, fatigue type wear accounted for 84 and 93 % of total wear score on autopsy and revision implants respectively. A highly significant influence on wear score was found in time of implantation (p = 0.002), level of activity (p = 0.025) and inserts belonging to revision group (p = 0.006). No influence was found for the kind of patella replacement (p = 0.483). Body mass index and accuracy of component alignment had no significant influence on visual wear score. Fatigue-type wear in the medial compartment was closely correlated to the index of use in the autopsy (R(2) = 0.383) and the revision group (R(2) = 0.813). CONCLUSION: The present study's finding of substantial fatigue type wear in both autopsy and revision retrievals supports the theory that polyethylene fatigue strength is generally exceeded in this type of prosthesis. Furthermore, this study correlated fatigue-type polyethylene wear to an index of use as calculated by activity over time. Future retrieval studies may use activity over time as an important patient related factor correlated to the visual wear score. When evaluating total knee arthroplasty routine follow up, the surgeon must think of substantial wear present even without major clinical signs.

Cement collar and longitudinal groove: the effects on mechanical stability with aseptic loosening in Müller straight-stem implants.

INTRODUCTION: The Müller straight-stem prosthesis (GS-77), in contrast to the Müller SL prosthesis (SL-88), is equipped with a cement collar and longitudinal grooves. Comparative observation of these prostheses suggests that cement collars protect against rapid subsidence and that longitudinal grooves prevent premature formation of a varus tilting deformity. METHOD: Because loosening is often observed in the titanium-alloy models of these implants, this retrospective study focused on these models. Differences based on other parameters known to affect mechanical performance were minimized by careful selection: the use of lateralizing implants, patient population characteristics (gender distribution, age, BMI, activity level), and consistency of prosthetic size (10). The comparability of the bending stiffness of both implants in corresponding sizes was verified using finite element method calculations. RESULTS: Up to the time of revision, 17 GS-77 and 33 SL-88 implants were compared for the amounts of subsidence and prosthetic tilting. Standardized follow-up films were contrasted and radiographically measured. At the time of revision, the GS-77 implants showed subsidence of 4.8 (+/-3.7) mm and the SL-88 implants 8.2 (+/-5.1) mm (p = 0.012). Leaving apart 3 cases with an extreme situation tilting of the GS-77 implants, with 1.2 (+/-0.9) degrees , averaged only two-thirds that of the SL-88 implants, with 1.9 (+/-1.1(p = 0.032). These results support the hypothesis that the cement collar of the Müller straight-stem prosthesis protects against rapid subsidence occurring with aseptic loosening of the implant. The longitudinal grooves appear to counter the development of varus tilting.

Propionibacterium spp. in prosthetic joint infections: a diagnostic challenge.

INTRODUCTION: Propionibacterium species are common inhabitants of the skin and usually non-pathogenic for humans. However, Propionibacterium spp. can occasionally cause infections, but are estimated to play a minor role in prosthetic joint infections (PJI). The relative frequency of these anaerobes and their potential to cause surgical site infection may be clinically underestimated. An unknown proportion of these infections might be missed, since little is known about their clinical presentation, and since growth of Propionibacterium spp. in diagnostic samples is often interpreted as contamination. Thus, a hypothesis is being tested, stating that Propionibacterium spp. is not as rare as often reported, and it can cause severe soft-tissue damages in PJI. MATERIALS AND METHODS: In this retrospective analysis, we reviewed all PJI that had been treated in our institution from 2000 to 2005, and assessed the relative frequency of those caused by Propionibacterium spp. In the identified cases, features that led to the diagnosis (clinical, laboratory, radiological, microbiological and histopathological characteristics) were analysed. RESULTS: Of 139 cases of prosthetic joint infections, 8(6%) were caused by Propionibacterium spp. Seven patients complained of pain as the main symptom, and four had damaged soft-tissue. Analysis of the diagnostic procedures showed a median of 39% positive samples out of all cultured biopsies (median 9.5 biopsies per case), with a median time-to-positivity of 8 days. Results of histopathological examinations of the periprosthetic tissue correlated well with the clinical courses. CONCLUSIONS: Our data suggest that Propionibacterium associated prosthetic joint infections occur at a relative frequency that is comparable to many other pathogens. Clinical signs are generally subtle, but the spectrum includes also significant soft-tissue damages. In this study, a median of 9.5 biopsies per case, an incubation time of 14 days, and the aid of histopathological examinations proved to be helpful in establishing the diagnosis.

The M.E Müller straight stem prosthesis: 15 year follow-up. Survivorship and clinical results.

The aim of the study was to document the long-term clinical and radiologic results as well as the 15 year survival of a single cemented straight stem. Our series consisted of consecutive patients with 161 straight stem prostheses implanted between 1984 and 1987 in 152 patients. Follow-up was performed prospectively at 1, 2, 5, 10 and 15 years post-operatively. Seven stems were revised due to aseptic loosening, the 15 years survival rate being 94%. There were 18 acetabular revisions. Pain and patient satisfaction declined slightly over the study period. We observed a more prominent health-related decline of functional results. This effect was mainly due to aging. Younger patients showed better clinical results, but also a higher revision rate.

Staphylococcus aureus small colony variants in prosthetic joint infection.

BACKGROUND: Small colony variants of Staphylococcus aureus tend to persist despite antimicrobial therapy, especially when involved in implant-associated infections. METHODS: We analyzed 5 cases of hip prosthesis-associated infections due to small colony variants, including their course prior to identification of the pathogen. Biopsy investigations included microbiological examination and, in 1 case, transmission electron microscopy to detect intracellular bacteria in nonprofessional phagocytes. A treatment concept was elaborated on the basis of a published algorithm and patients were managed accordingly. RESULTS: The patients' mean age was 62.2 years. All patients experienced treatment failures prior to isolation of small colony variants, despite as many as 3 surgical revisions and up to 22 months of antibiotics. Transmission electron microscopy performed on biopsy specimens from periprosthetic tissue revealed intracellular cocci in fibroblasts. All prostheses were removed without implanting a spacer, and antimicrobial agents were administered for 5.5-7 weeks. Reimplantation of the prosthesis was performed for 4 patients. Follow-ups were uneventful in all 5 cases. CONCLUSIONS: In the case of a poor response to adequate antimicrobial and surgical treatment in implant-associated staphylococcal infections, small colony variants should be considered and actively sought. In our case series, a 2-stage exchange without implantation of a spacer combined with antimicrobial therapy for an implant-free interval of 6-8 weeks was associated with successful outcome, with a mean follow-up of 24 months.