Catastrophic failure of an uncemented acetabular component due to high wear and osteolysis: An analysis of 154 Omnifit prostheses with mean 6-year follow-up

Background The purposes of this study were (1) to evaluate the wear pattern of the hydroxyapatite-coated "Dual Radius" Omnifit cup, (2) to investigate whether wear is correlated to any demographic or prosthesis-related factors, and (3) to describe micromotion of both the cup and the stem. Patients and methods 154 hips were implanted between 1990 and 1996 and followed for an average of 6 years. Wear was measured according to the "Charnley-duo" method and, in 79 hips, with radiostereometry (RSA). RSA was also used to evaluate micromotion. We analyzed the femoral heads using scanning electron microscopy, energy dispersive X-ray spectroscopy and an atomic force microscope. Result 66 cups were revised and had a mean annual wear of 0.32 mm compared to 0.12 mm in hips not revised. Osteolytic processes were observed in 35 hips but at revision osteolysis was present in 51 cases. 43/66 sockets were loose. Micromotion evaluated by RSA, weight, age, side, size of cup, screws, polyethylene thickness or shelf-life of the polyethylene did not correlate to wear, whereas male gender did. Interpretation It is still unclear why about half of our cases had an abnormal wear rate. Annual wear exceeding 0.2 mm is prognostic of late failure and should be considered a warning sign

Accuracy of radiographic and radiostereometric wear measurement of different hip prostheses: an experimental study.

Background In vivo measurement of wear in the ball and socket articulation of total hip arthroplasties is of interest in the evaluation of both existing and new implants. Controversy reigns regarding the accuracy of different radiological measurement techniques and in particular how accuracy has been assessed. Material and methods We assessed the accuracy of 2 radiostereometric (RSA) techniques for wear measurement and 3 standard radiographic techniques, namely Imagika (image analyzing software), Imagika corrected for head center displacement, and the Charnley Duo method. 5 custom-made adjustable phantoms with different prosthetic components were used. Results In 20 measurements of all 5 phantoms at 3 levels of simulated wear (0.2 mm, 1.0 mm and 1.5 mm), the mean measurement error of the digital RSA examinations was 0.010 mm (accuracy 0.42). The corresponding error values for the three radiographic techniques were 0.19 (accuracy 1.3) for Charnley Duo, 0.13 (accuracy 1.3) for Imagika corrected, and 1.021 (accuracy 2.99) for Imagika. Measurement error decreased from 0.011 mm with ordinary RSA to 0.004 with RSA digital measurement. Head size, direction of wear in relation to the cup or type of prosthetic component did not influence the measurement error. The results of Charnley Duo and Imagika corrected were similar but the latter had an inexplicable systematic error in measuring one of the phantoms. Imagika had the worst results due to its inability to compensate for the out-of-head center effect. Alumina heads were difficult to analyze with all methods. Interpretation By using the ISO standard for assessing accuracy, RSA can be expected to measure wear with an accuracy of about 0.4 mm irrespective of prosthetic component studied or direction of wear, whereas the best technique, in our study, based on standard radiographs can be accurate to about 1.3 mm

The Elite-Plus stem migrates more than the flanged Charnley stem: A clinical, radiographic, and radiostereometric analysis of 114 patients with an average of 7 years follow-up

Background and purpose The Charnley Elite-Plus stem was introduced in 1993 as a presumed improvement of the flanged Charnley stem. We started this study in 1996 to investigate the migratory pattern of the Elite-Plus stem. Patients and methods We followed 114 patients with osteoarthritis and a primary total hip replacement with the Elite-Plus stem. Mean age at the time of operation was 64 (50-76) years. The mean follow-up time was 6.5 (2-7) years. Radiographs were evaluated with respect to cementing technique, migration, and wear measured by radiostereometry (RSA). Results The stem survival was 98% (CI: 96-100) at 7 years and 92% (CI: 86-97) at 10 years. Mean migration of the femoral head was 0.35 mm (SD 0.3) medially, 0.51 mm (SD 0.6) distally, and 1.1 mm (SD 1.8) in the dorsal direction. Mean total point motion was 1.7 mm (SD 1.7). The migration of the stems stabilized after 5 years in the medial and dorsal directions, but continued to subside slightly. Migration along any of the axes was higher if the cementing technique was inferior. Interpretation Patients with a Charnley Elite-Plus stem and defects in the cement mantle or other signs of inferior implantation technique should be carefully monitored

Fixation of the fully hydroxyapatite-coated Corail stem implanted due to femoral neck fracture: 38 patients followed for 2 years with RSA and DEXA

Background Today, dislocated femoral neck fractures are commonly treated with a cemented hip arthroplasty. However, cementing of the femoral component may lead to adverse effects and even death. Uncemented stems may lower these risks and hydroxyapatite (HA) coating may enhance integration, but prosthetic stability and clinical outcome in patients with osteoporotic bone have not been fully explored. We therefore studied fixation and clinical outcome in patients who had had a femoral neck fracture and who had received a fully HA-coated stem prosthesis. Patients and methods 50 patients with a dislocated femoral neck fracture were operated with the fully HA-coated Corail total or hemiarthroplasty. 38 patients, mean age 81 (70-96) years, were followed for 24 months with conventional radiographs, RSA, DEXA, and for clinical outcome. Results 31 of the 38 implants moved statistically significantly up to 3 months, mainly distally, mean 2.7 mm (max. 20 mm (SD 4.3)), and rotated into retroversion mean 3.3 (-1.8 to 17) (SD 4.3) and then appeared to stabilize. Distal stem migration was more pronounced if the stem was deemed to be too small. There was no correlation between BMD and stem migration. The migration did not result in any clinically adverse effects. Interpretation The fully hydroxyapatite-coated Corail stem migrates during the first 3 months, but clinical outcome appears to be good, without any adverse events

Clinical and experimental studies on wear and osteolysis in total joint replacement

Total hip arthroplasty is a very successful procedure. Despite this fact, however, a certain portion of patients has to be revised. One major reason for revision is the wear of the polyethylene leading to loosening and osteolysis. The overall aim of this thesis was to evaluate linear wear and migration of cemented, all - polyethylene sockets and polyethylene liners in total hip arthroplasty. The aim was also to identify patients for whom increased wear was a risk and who therefore were likely to require a revision, and further to evaluate different methods for measuring wear and their accuracy Material and results Study I: 154 hips had received an uncemented Omnifit total hip. 66 cups were revised and in these cases mean annual wear was 0.32 mm compared to 0.12 mm in hips not revised. Osteolytic processes were present in 51 patients at revision but these could be observed in only 35 hips on radiographs. Micromotion evaluated by RSA, weight, age, side, size of cup, screw fixation, polyethylene thickness or shelf - life of the polyethylene did not correlate to wear, whereas male gender did. Study II: Cross - linked N-telopeptide of type I Collagen (NTx), a marker of osteoclast - mediated bone resorption, has been proposed for the evaluation of the often non-symptomatic peri-prosthetic osteolysis. NTx in urine was analysed in 160 patients with and without osteolysis. The group of patients with osteolysis had significantly higher mean NTx levels (p=0.03) and an increased annual wear of the polyethylene. Study III: 120 patients were randomised to have a primary total hip replacement with one out of four possible articulations. The femoral heads were of conventional steel or of a new ceramic, zirconium oxide. The cup was either made of conventional polyethylene or of polyethylene that had been reheated under pressure, Hylamer. All combinations that included Hylamer or Zirconium oxide had increased polyethylene wear as compared to the standard steel / polyethylene combination (p<0.008). 12 patients have been revised to date- none had a stainless steel / polyethylene articulation. Study IV: Polyethylene penetration (wear) was measured by RSA in 111 patients by radiostereometric analysis (RSA) in the supine and weight-bearing position. There was a small (0.02mm) systematic difference. The degree of penetration of the head into the polyethylene or the time for the first examination did not alter this result. Study V: We analysed the accuracy of 2 radiostereometric (RSA) techniques for wear measurement and 3 standard radiographic techniques using a phantom with different prosthetic components. The mean differences between phantom and measurement were, for digital RSA examinations 0.010 mm (accuracy 0.42, n=175). The corresponding error values for the three radiographic techniques were 0.19 (accuracy 1.3, n=180) for Charnley Duo, 0.13 (accuracy 1.3, n=180) for Imagika corrected, and 1.021 (accuracy 2.99, n=180) for Imagika. Measurement error decreased from 0.011 mm with ordinary RSA to 0.004 with RSA digital measurement. Head size, direction of wear in relation to the cup or type of prosthetic component did not influence the measurement error

Cross-linked N-telopeptide of type I collagen (NTx) in urine as a predictor of periprosthetic osteolysis.

Periprosthetic osteolysis is often nonsymptomatic and hard to visualize by conventional radiography. Cross-linked N-telopeptide of type I collagen (NTx), a marker of osteoclast mediated bone resorption, has been suggested to evaluate local particulate-induced osteolysis in patients operated on with a total hip prosthesis. Urine specimens were sampled after hip joint replacement in 160 patients. NTx was analyzed by a commercially available ELISA kit. Osteolysis was identified in the acetabulum and confirmed at operation. Using analysis of covariance to correct for differences in age, gender, and time after operation, NTx (mean SD) was 36 +/- 12 BCE/nM creatinine in patients with osteolysis (n = 33) and 27 +/- 13 BCE/nM creatinine in patients without osteolysis (n = 127) (p = 0.003). Eighteen hips of 38 (47%), demonstrating an annual wear of more than 0.2 mm and an NTx value above 29 BCE/nM creatinine, had been revised due to osteolysis. The osteolysis prevalence in this group was increased 10 times (CI 4-23, p < 0.05). Indeed, NTx release and annual wear were both associated with increased prevalence of osteolysis, however, independently of each other. NTx seems a feasible marker of periprosthetic osteolysis. A preoperative baseline NTx level is likely needed for its use as a predictor of periprosthetic osteolysis in individual cases. (c) 2006 Orthopaedic Research Society

Continuous distal migration and internal rotation of the C-stem prosthesis without any adverse clinical effects: an RSA study of 33 primary total hip arthroplasties followed for up to ten years.

In 2005, we demonstrated that the polished triple-tapered C-stem at two years had migrated distally and rotated internally. From that series, 33 patients have now been followed radiologically, clinically and by radiostereometric analysis (RSA) for up to ten years. The distal migration within the cement mantle had continued and reached a mean of 2 mm (0.5 to 4.0) at ten years. Internal rotation, also within the cement mantle, was a mean 3.8° (external 1.6° to internal 6.6°) The cement mantle did not show any sign of migration or loosening in relation to the femoral bone. There were no clinical or radiological signs indicating that the migration or rotation within the cement mantle had had any adverse effects for the patients. Cite this article: Bone Joint J 2014;96-B:604-8

A clinical and radiostereometric study of the cemented PFC-sigma prosthesis: a 5-year study of 29 cases with a fixed bearing.

The press-fit condylar (PFC) cruciate-retaining total knee prosthesis is well documented in the literature. In 1997, a modification of the femoral component was introduced, and the prosthesis was renamed PFC-Sigma. The alteration may influence the migratory and rotational pattern of the tibial component and thus long-time survival rate. In this radiostereometric analysis, we found that the micromotion of the PFC-Sigma prosthesis differs slightly from the original PFC design, an advantage of the PFC-Sigma prosthesis. The median maximum total point motion at 5 years was 0.64 mm for the PFC-Sigma design and 0.79 mm for the previous version of PFC (P = .9). However, the PFC-Sigma rotated less around the transverse (x) axis than did the PFC (medians, 0.22 mm and 0.48 mm, respectively; P = .04). From the radiostereometric, radiographic, and clinical data, we conclude that the PFC-Sigma knee prosthesis can be used with confidence

Total hip replacement with a zirconium oxide ceramic femoral head: a randomised roentgen stereophotogrammetric study.

We investigated the wear characteristics and clinical performance of four different total hip joint articulations in 114 patients. Wear and migration was measured by roentgenstereophotogrammetric analysis at five years or at the last follow-up. The mean annual wear was 0.11 mm for a stainless steel/Enduron articulation, 0.34 mm for stainless steel/Hylamer cup, 0.17 mm for zirconium oxide ceramic/Enduron and 0.40 mm for zirconium oxide ceramic/ Hylamer. The difference between the groups was significant (p < 0.008) except for stainless steel/Hylamer vs zirconium oxide ceramic/Hylamer (p = 0.26). At present, 12 patients have undergone a revision procedure, four at five years and eight thereafter. No patient who received a stainless steel/Enduron articulation at their primary replacement required revision. Conflicting results have been reported about the performance of the zirconium oxide ceramic femoral head, but our findings suggest that it should not be used with a polymethylmethacrylate acetabular component. Hylamer has already been withdrawn from the market