The prevalent cause of implant failure after total joint replacement is aseptic loosening caused by wear debris. Improvement of the wear behaviour of the articulating bearing between the cup and femoral head is essential for increased survival rate of artificial hip joints. Cross-linking of the polyethylene (PE) material is one attempt to reduce wear particle release at the articulating surface. Various cross-linked polyethylenes (X-PE) are used in orthopaedics since several years. In total hip arthroplasty (THA) the use of larger femoral head sizes has specific reasons. Larger heads lead to a decreased risk of total hip dislocation and impingement as well as an improved range of motion in comparison to smaller head sizes like 28mm or less. However, the increasing diameter of femoral head can be associated with lower thickness of the PE liner and increased wear rate. Cross-linking of PE can improve the wear rate of the liner and hence supports the use of larger femoral heads. The aim of this experimental study was to evaluate the wear of standard vs. sequential X-PE (X3-PE) liner in combination with different ceramic femoral head sizes. Wear testing was performed for 5 million load cycles using standard UHMW-PE liners (N2Vac) and X3-PE liners (each Stryker GmbH & Co. KG, Duisburg, Germany) combined with 28mm ceramic ball heads and the Trident PSL acetabular cup (Stryker). Furthermore, X3-PE liners with an internal diameter of 36mm and 44mm and decreased wall thickness (5.9mm and 3.8mm) were combined with corresponding ceramic heads. An eight station hip wear simulator according to ISO 14242 (EndoLab GmbH, Rosenheim, Germany) was used to carry out the standard wear tests. The tests were realised in temperature-controlled chambers at 37°C containing calf serum (protein content 20g/l). The average gravimetrical wear rates of the standard UHMW-PE (N2Vac) liners combined with 28mm ceramic heads amounted to 12.6 ± 0.8mg/million cycles. Wear of X3-PE liners in combination with 28 mm ceramic heads was not detectable. The average gravimetrical wear rates of the X3-PE liners in combination with 36mm and 44mm ceramic heads amounted to 2.0 ± 0.5mg and 3.1 ± 0.3mg/million cycles, respectively. The purpose of this study was to evaluate the effect of femoral head size at THA on standard and sequential X-PE liner. The wear simulator tests showed that the wear rate of PE liners with small heads (28mm) decreased by cross-linking of the PE significantly. The amount of wear at X-PE increased slightly with larger head size (36mm and 44mm). However, by sequential cross-linking, the wear rate using thinner liners and larger femoral heads is reduced to a fractional amount of wear at conventional UHMW-PE. Hence, the above-mentioned advantages of larger femoral head diameters can be realised by improved wear behaviour of sequential X-PE

Introduction. Controversy exists as to whether the short external rotator tendons and capsule of the hip should be repaired after posterior approach primary total hip arthroplasty (THA). Recent studies using radiopaque markers have demonstrated that reimplantation of these muscle tendons fail early and may not prevent post operative dislocation. Methods. Using dynamic ultrasound examination we evaluated the patency of repair in 68 tendon groups (piriformis/conjoint tendon and obturator externus). We demonstrate short and medium term success in the reimplantation of these tendons using the double transosseous drill hole technique of reattaching the tendons and capsule to the greater trochanter. We followed up 21 of our total hip replacements and 13 hip resurfacings and undertook a dynamic ultrasound examination of the external rotators by an experienced musculoskeletal radiologist to assess their integrity at a minimum of 60 days and 100 days and an average of 213 days after the operation. Results. There were 34 hips assessed in 33 patients. 21 were total hip replacements and the rest were hip resurfacings. Each patient underwent a standard posterior approach by the senior surgeon. The piriformis and conjoint tendons (Group 1) and the obturator extenus (Group 2) were reattached with modified kessler sutures using a transosseous reimplantation technique. The capsule was reattached with a running suture using the same technique. The total hip replacement group had 16 out of 21 hips (76.2%) where both external rotator groups were intact at follow up, compared with 3 out of 13 hips (23.1%) for the hip resurfacing group (Chi-squared 9.188, p=0.002). Group 1 tendons were intact in 81% of the THR group while only in 53.8% in the rsurfaing group. We compared the hip replacement group with the hip resurfacing group using survival analysis techniques (log rank test), which take into account the different follow-up times. The hip replacement group showed a significantly longer time to the event of either rotator group not being intact at follow-up than the hip resurfacing group (log rank 5.568, p=0.018). Conclusions. Our results do appear to suggest that this technique may be of benefit in patients undergoing primary THA but may not be as successful after resurfacing procedures. We propose that the increased incidence of external rotator detachment seen in the resurfacing group may be due to the increased strain imparted on the tendons due to the greater distance to travel, as they wind around the large resurfaced femoral head and neck as compared to the relatively thinner THA femoral neck and smaller head component

Aims

This study aimed to compare the change in health-related quality of life of patients receiving a traditional cemented monoblock Thompson hemiarthroplasty compared with a modern cemented modular polished-taper stemmed hemiarthroplasty for displaced intracapsular hip fractures.

Endoprosthetic replacement of the proximal femur may be required to treat primary bone tumours or destructive metastases either with impending or established pathological fracture. Modular prostheses are available off the shelf and can be adapted to most reconstructive situations for this purpose. We have assessed the clinical and functional outcome of using the METS (Stanmore Implants Worldwide) modular tumour prosthesis to reconstruct the proximal femur in 100 consecutive patients between 2001 and 2006. We compared the results with the published series for patients managed with modular and custom-made endoprosthetic replacements for the same conditions.

There were 52 males and 48 females with a mean age of 56.3 years (16 to 84) and a mean follow-up of 24.6 months (0 to 60). In 65 patients the procedure was undertaken for metastases, in 25 for a primary bone tumour, and in ten for other malignant conditions. A total of 46 patients presented with a pathological fracture, and 19 presented with failed fixation of a previous pathological fracture. The overall patient survival was 63.6% at one year and 23.1% at five years, and was significantly better for patients with a primary bone tumour than for those with metastatic tumour (82.3% vs 53.3%, respectively at one year (p = 0.003)). There were six early dislocations of which five could be treated by closed reduction. No patient needed revision surgery for dislocation. Revision surgery was required by six (6%) patients, five for pain caused by acetabular wear and one for tumour progression. Amputation was needed in four patients for local recurrence or infection.

The estimated five-year implant survival with revision as the endpoint was 90.7%. The mean Toronto Extremity Salvage score was 61% (51% to 95%). The implant survival and complications resulting from the use of the modular system were comparable to the published series of both custom-made and other modular proximal femoral implants.

We conclude that at intermediate follow-up the modular tumour prosthesis for proximal femur replacement provides versatility, a low incidence of implant-related complications and acceptable function for patients with metastatic tumours, pathological fractures and failed fixation of the proximal femur. It also functions as well as a custom-made endoprosthetic replacement.