Background

Hip arthroscopy is a rapidly growing, evolving area within arthroscopic Orthopaedic Surgery, with annual rates increasing as much as 25-fold each year. Despite improvements in equipment and training, it remains a challenging procedure. Rates of revision surgery have been reported as 6.3% to 16.9%.

Introduction and Aims: Aim of the study is to show whether the accuracy of alignment of a total knee pros-thesis is more dependent on the instrumentation or the skills of the surgeon.

Method: Forty patients that had total knee arthroplasties performed between September 1997 and September 1999 have been analysed. The results of prospective randomised trial using the LCS (Depuy) and IBII (Zimmer) prostheses have been analysed, as well as results using the Scorpio (Stryker) and Profix (Smith + Nephew) total knee replacement systems. Patients were evaluated according to a radiographic protocol, a modification of the Knee Society total knee arthroplasty x-ray evaluation and scoring system. All patients had long leg standing x-rays in full extension and neutral rotation. Lateral x-rays were taken in neutral rotation with a maximum of 10 degrees of flexion. The femoral varus/valgus alignment is recorded on the AP x-ray as the Alpha angle, and the tibial alignment as the Beta angle. On the lateral x-ray the Gamma angle records the femoral flexion and the Theta angle the tibial prosthesis alignment along the tibial shaft.

Results: The results were statistically analysed by the Department of Statistics at the University. Results were stratified according to both the instrumentation used and the surgeon. These showed that there was no statistical difference between the alignment of the different prostheses, irrespective of the surgeon performing the procedure.

Conclusion: From this study we concluded that no one set of instrumentation used while performing a total knee replacement was superior to another. As long the surgeon is familiar with the instrumentation the final alignment of the prosthesis will be satisfactory.

The cause of unremitting hip joint pain often remains undiagnosed. In the knee, MRI often accurately detects soft tissue pathology, but there is a less than 5% chance that MRI will show an abnormality such as a labral tear. Because conventional surgery can lead to such complications as avascular necrosis, muscle weakness, trochanteric nonunion, heterotopic bone formation, neurovascular injuries and DVT, diagnostic open arthrotomy is seldom performed. Further, prolonged hospitalisation is costly and commits the patient to an extended rehabilitation program.

Arthroscopic hip surgery, a relatively new but well-established procedure, permits the identification of previously unrecognised disorders and in some pathologies offers definitive treatment. In young selected patients with OA it serves as a temporary palliative procedure.

This presentation is based on the first 50 hip arthroscopies performed by the author. Indications for operation were chronic hip pain without radiologically-discernible cause, the presence of loose bodies following trauma, chondrocalcinosis, labral lesions, chondral injuries, ruptured ligamentum teres, avascular necrosis, early OA, biopsy for suspected RA, and non-specific synovial disease. All patients were in hospital for only a day. Mobilisation was encouraged from day one. Dramatic improvement in previous symptoms was noted postoperatively. In three patients with degenerative changes, pain returned after a mean of 6 months and THR was subsequently performed.

Hip arthroscopy is a minimally invasive diagnostic and treatment technique, especially in young patients presenting with hip pain.

Introduction and Aims: Wear of ultra-high molecular weight polyethylene (UHMWPE) acetabular cups is a well-known cause of osteolysis and loosening of the components. Improvement of the wear resistance of UHMWPE could extend the clinical life of total hip arthroplasty (THA). Chemical cross-linking in acetylene with gamma radiation is a cheap and effective way of increasing wear resistance of UHMWPE.

Method: This study is a report on 132 patients operated between 1977 and 1984, using the Pretoria monobloc stainless steel hip with 30mm metal head. Acetabular cups were machined from RAM extruded rectangular bars (RCH 1000). Final cups were gamma irradiated in stainless steel containers filled with acetylene gas. Three hundred microns surface cross-linking was achieved at 100kG. At that time, 1059 hip replacements were performed by the two first authors. The retrospective study consisted of measurement of the radiological wear. The criteria was to compare and measure the wear from early post-op radiograph and longest follow-up radiograph. Linear wear was measured according to the Livermore methods. Exclusion criteria included follow-up less than 10 years, sepsis, dislocation and other non wear-related causes of failure. The rarely retrieved cross-linked ace-tabular cups were analysed individually using spectrum electron microsope (SEM).

Conclusion: The South African contribution to the method of cross-linking is important. This is a cheap and effective way to improve the quality of the polyethylene. Results of this long-term group of patients with cross-linked UHMWPE show a significant decrease in the wear rate, significantly increasing the longevity of the THR.

In high-demand situations, modern thinking and experience in total hip arthroplasty (THA) favours the uncemented press-fit cup over its cemented counterpart. Before its regular use in 1996, a high-demand cemented stem was designed for use as a short revision stem with a press-fit cup, with or without impaction bone grafting, in active people, especially those over 55 years.

Conceptually, a collarless double-tapered highly polished design was preferred. The clip-on hollow centraliser was designed for 5-mm subsidence. The valgus stem, with cement superior to the shoulder, limited upward pistoning in the cement sleeve, creating less debris. The stiff upper and flexible distal part resulted in a decreased contribution from shear and an increased contribution from compression in load transfer from prosthesis to cement. Three sizes are available: G1, G2 and G3. A straight type is presently being developed for smaller patients with congenital dysplasia of the hip.

The stem, made by (Thornton Heavy Engineering Sheffield, United Kingdom), from Rex 734 stainless steel to ISO-2002 standards, tapers 10 mm to 12 mm (6°). All tolerances are adequate to handle Inox or Ceramic heads.

From April 1996 to December 2002, 278 stems were implanted in Dr Weber’s practice. The first 172 hip operations (168 patients) were studied. The mean age was 58.6 years. There were 137 primary hips and 25 revisions.

The mean follow-up period was 4.5 years (3 to 7). Three patients died with the prosthesis in situ. Two reoperations were done: one cup was revised for recurrent dislocation and one fracture below the step was successfully plated. Only three cases of subsidence were documented, all of them less than 3 mm. To date there have been no stem revisions.

The prosthesis, together with the stainless steel head and cross-linked cup, can be regarded as cost-effective and can be used routinely, as a high-demand prosthesis with press-fit cup, or as a short-revision prosthesis.

Wear of ultra-high molecular weight polyethylene (UHMWP) acetabular cups is a well-known cause of osteolysis and loosening of the components. Improvement of the wear resistance of UHMWP could extend the clinical life of total hip arthroplasty (THA). Chemical cross-linking in acetylene with gamma radiation is a cheap and effective way of increasing wear resistance of UHMWP.

This study is a report on 263 patients (123 males and 140 females) on whom Dr Weber performed THA between 1977 and 1984, using the Pretoria (Grobbelaar) monobloc stainless steel hip with 30-mm metal head. There were 96 patients (107 prostheses) available for follow-up at a mean of 18.3 years, with 89 surviving prosthesis in 79 patients (83.2%).

We collected complete sets of radiographs of 54 patients (mean age 71.4 years) for a radiological survey in 1999. In 41 patients (76%) we found no wear. The mean age of these patients was 72 years. Wear was noted in the other 13 patients (24%), whose mean age was 75 years. The mean follow-up time was 16 years (8 to 23). The mean magnification in the radiological study was 18%. Mean wear for the total group was 1.29 mm and mean annual wear 0.17 mm.

A similar analysis performed on a group of 64 of Dr Grobbelaar’s patients at 15.5 year mean follow-up shows remarkable similarity, with mean wear of 0.172 mm for a group of 64 patients and annual wear 0.11 mm. Dr Oonishi of Japan, who has conducted the only other long-term follow-up, found similarly promising results.