O steolysis is due to particulate wear debris and is responsible for the long-term failure of total hip replacements. It has stimulated the development of alternative joint surfaces such as metal-on-metal or ceramic-on-ceramic implants.Since 1988 the second-generation metal-on-metal implant Metasul has been used in over 60 000 hips. Analysis of 118 retrieved specimens of the head or cup showed rates of wear of approximately 25 µm for the whole articulation per year in the first year, decreasing to about 5 µm per year after the third. Metal surfaces have a 'self-polishing' capacity. Scratches are worn out by further joint movement. Volumetric wear was decreased some 60-fold compared with that of metal-on-polyethylene implants, suggesting that second-generation metal-on-metal prostheses may considerably reduce osteolysis. [Br] 1998;80-B:46-50. Received 20 April 1998; Accepted after revision 8 July 1998 Osteolysis is due to particulate wear debris 1,2 and is mainly responsible for the long-term failure of total hip replacement (THR). The Charnley THR has been shown to give satisfactory clinical results with a survival rate of 85% at 20 years. When radiological evidence of loosening was added to that seen at revision operations, 22% of the acetabular and 7% of the femoral components were considered to be unstable. Polyethylene wear was shown to be significantly related to acetabular loosening and resorption of the femoral neck in nearly two-thirds of cemented THRs in patients younger than 20 years at the time of operation. 4 About half a million polyethylene wear particles are produced at each step due mainly to abrasive wear. 5,6 Contact of particle-laden articular fluid with the surrounding bone could be a key factor in the development of osteolysis. Joint fluid under pressure invades soft tissues and bone and expands the effective joint pace. J Bone Joint Surg7 As a result, activated macrophages may be found in cysts around the prostheses. 8It is not only the concentration of accumulated polyethylene particles which affects the amount of osteolysis, but also their capacity for phagocytosis.9,10 Particles with a critical size of between 0.5 and 10 µm are needed to induce the secretion of interleukin-6 by macrophages in vitro. It is still unclear as to whether polyethylene or cement debris induces more osteolysis. Severe lysis around a stable uncemented press-fit titanium shell is a clear indication of polyethylene wear.11 Polymethylmethacrylate (PMMA) cement alone is less harmful if it does not contain radiopaque additives. In vitro, monocytes and macrophages responding to particles of bone cement are capable of differentiation into osteoclastic cells. Their capacity for bone resorption is activated only when radiopaque additives are introduced with the cement particles, with a doubling of the rate for Ba 2 SO 4 compared with ZrO 2 . 12Osteolysis therefore has a multifactorial pattern and the biological activity of all possible wear particles has to be considered when introducing new implants. 13There have bee...

Osteolysis is due to particulate wear debris and is responsible for the long-term failure of total hip replacements. It has stimulated the development of alternative joint surfaces such as metal-on-metal or ceramic-on-ceramic implants. Since 1988 the second-generation metal-on-metal implant Metasul has been used in over 60 000 hips. Analysis of 118 retrieved specimens of the head or cup showed rates of wear of approximately 25 microm for the whole articulation per year in the first year, decreasing to about 5 microm per year after the third. Metal surfaces have a 'self-polishing' capacity. Scratches are worn out by further joint movement. Volumetric wear was decreased some 60-fold compared with that of metal-on-polyethylene implants, suggesting that second-generation metal-on-metal prostheses may considerably reduce osteolysis.

Background The transfemoral approach is an extensile surgical approach that is performed routinely to facilitate cement and implant removal and improve exposure for revision stem implantation. Previous studies have looked at clinical results of small patient groups. The factors associated with fixation failure of cementless revision stems when using this approach have not been examined. Questions/purposes We determined (1) the clinical results and (2) complications of the transfemoral approach and (3) factors associated with fixation failure of revision stems when using the transfemoral approach. Patients and Methods We retrospectively examined all our patients in whom femoral stem revision was performed through a transfemoral approach between December 1998 and April 2004 and for whom a minimal followup of 2 years was available. One hundred patients were available for this study. The mean (± SD) postoperative followup was 5 years (± 1.64 years). Results The average Harris hip score improved from 45.2 (± 14.02) preoperatively to 83.4 (± 11.86) at final followup. Complete radiographic bony consolidation of the osteotomy site was observed in 95% of patients. Dislocations occurred in 9% of patients. Four revision stem fixation failures were observed, all occurring in patients with primary three-point fixation. Three-point fixation was associated with short osteotomy flaps and long revision stems. Conclusions The transfemoral approach is associated with a high rate of osteotomy flap bony healing and good clinical results. When using the transfemoral approach, a long osteotomy flap should be performed and the shortest possible revision stem should be implanted.

Different approaches for implantation lead to different fixation techniques of a curved revision stem. This should be considered by analysing postoperative sintering rates of cementless revision stems.

Progressive retropatellar arthrosis is often seen in dated rigid distal realignment (i.e. osteotomy of tuberositas) at long-term follow-ups. Therefore, operations for lateral dislocation of the patella are still discussed controversially. Dynamic, proximal realignments seem to have lower rates of arthrosis but higher rates of redislocation. Recently, in anatomic and biomechanic studies, the m. vastus medialis obliquus (vmo) was found to be one of the most important proximal restraints to lateral dislocation of the patella.A total of 28 patients (mean age 21.5 years) were treated between 1994 and 2003 with a plasty of the vmo for lateral patellar dislocation. The technique was performed for most etiologies of femoropatellar instability. For this proximal soft tissue technique, the muscle tendon is detached from its patellar insertion. Subsequently, the tendon is reinserted at the patella 10-15 mm more distally and fixed with Mitek anchors. Full weight bearing in extension is possible immediately after surgery. An active vastus medialis training is started after 6 weeks. Of the patients, 27 were evaluated clinically and radiologically in 2004 (a mean of 5 years postoperatively). A total of 83% of the patients estimated the result to be good or excellent, 10% were satisfied and 7% were discontent. The mean Lysholm-Knee-Score was 83.1 points. Two patients suffered a patella redislocation (7%). A statistically significant improvement of the congruence angle was noted in the radiographs, even in medium-term controls. In 89% of the cases no or only little retropatellar arthrosis was observed. These 5 year results are comparable to those of other techniques for distal or proximal realignments. The rate of redislocation was below average. Compared to the rate of retropatellar arthrosis in long-term results of rigid distal realignment, our patients demonstrated a relative low rate after 5 years. We attribute this to the minimal interference in physiological joint mechanics and to the restored anatomy. In terms of future long-term results, our findings are promising. The idea of a proximal dynamic stabilization and the causal operative approach at the origin of pathology using vmo-plasty was confirmed in recent anatomic and biomechanic studies. Over or under correction of soft tissues could be adapted. More rigid techniques of distal realignment do not allow an adaptation to this extent and can lead to prearthrotic hyperpression in the medial femoropatellar and femorotibial joints.