Aim: To determine the incidence of periacetabular osteolysis in an uncemented, press-fit, one-piece, titanium plasma spray backed acetabular cup used in conjunction with a cemented or uncemented femoral component followed for 10 years.

Method: Patients undergoing primary total hip arthroplasty in 1989 were reviewed and new radiographs obtained. These were compared with the initial post-operative radiographs and the presence of osteolysis in the three zones of Delee and Charnley were recorded.

Results: Of 57 patients, 14 were deceased at the time of follow-up and nine were lost to follow-up. Ten patients had undergone revision for problems related to the femoral stem. There was only one possible case of periacetabular osteolysis seen in this series. In this case the lytic lesion was seen on the early post-operative radiograph and did not change in 10 years, and thus may not have been osteolysis.

Conclusions: The reported incidence of periacetabular osteolysis with two-piece cups varies between 30 and 50%. Thus, this cup has an extremely low possible osteolysis incidence. This study raises the wisdom of the continued use of two piece cups of any design.

Aim: To ascertain whether there is a relationship between time to surgery and mortality in hip fracture patients.

Method: The records of 120 patients admitted with hip fractures were examined. The approximate time of injury, the time of admission to hospital, the time of surgery, the number of medical co-morbidities, the A.S.A. grade, age, and length of hospital stay, were recorded. Death statistics were obtained from the Registrar of Births Deaths and Marriages. An analysis was then performed to assess the presence of correlation between time from injury to surgery, time from admission to surgery and three and six-month mortality in patients who were A.S.A. grades two or three.

Results: Preliminary analysis of the data showed a strong correlation between time from injury and the time from admission, to surgery and subsequent death. When these times exceeded 24 hours the mortality increased.

Conclusion: This study suggested that every effort should be made to operate on patients with hip fractures within 24 hours of admission to minimise mortality resulting from this injury.

Aim: To examine the histology of the bone-cement interface in a canine total hip model comparing two different cementing techniques.

Method: Seven adult mongrel dogs underwent staged bilateral total hip replacement. On one side the cement was packed into the femur with a finger while on the opposite side the femoral canal was washed, brushed, distally plugged and injected with cement under pressure before inserting the femoral component. Sequential fluorochrome bone labelling was performed. The dogs were sacrificed up to six months after the surgery. Undecalcified sections of the femur were examined by fluorescent microscopy.

Results: Post-operative radiographs showed complete filling of the proximal femur with cement in the pressure injected group, and a relatively thin mantle in the finger-packed group. Histology of the finger-packed group showed minimal intrusion of cement into the cancellous bed, direct apposition of cement and bone with small areas of fibrous tissue interposition. In the pressure- injected group the cement extended to the endosteal cortex, there was no bone necrosis, and the intruded bone underwent remodelling similar to that at the margins.

Conclusions: This study suggested that ‘third generation’ cementing techniques result in greater contact between bone and cement, and may explain the claim that femoral stems in humans inserted using third generation techniques are more durable than those inserted using ‘first generation’ techniques.

Aim: The direct lateral approach, as described by Hardinge et al, may have the advantage of reducing the incidence of dislocation after total hip arthroplasty. The purpose of this paper is to describe a modification of the direct lateral approach used by the author on consecutive total hip arthroplasty for all patients; including primary arthritis, fractures and revisions over a period of five years. The incidence and causes of complications, specifically dislocation, is discussed.

Method: A modification of the direct lateral approach, where gluteus minimus is split anteriorly rather than being detached from the greater trochanter, is described. This approach allowed its primary repair during wound closure, reducing surgical dead-space and theoretically reducing the incidence of dislocation. The records of all patients in whom the author performed this approach for total hip arthroplasty between 1 February 1994 and 1 February 1999 were examined. Patients were routinely seen at one year after operation and any early complications of surgery recorded. Minimum follow-up for this series was one year.

Conclusion: This modification of the direct lateral approach which preserves the integrity of gluteus minimus while still allowing adequate exposure and is extensile, gave a very acceptable incidence of dislocation in total hip arthroplasty for degenerative disease, fracture, and revision cases.

Introduction: Ultra high molecular weight polyethylene (UHMWPE) wear debris generated at the articulating interface of total hip arthroplasties continues to be the major cause of early failure of these implants.

Aim: To validate the accuracy and reproducibility of the three-dimensional technique (3D) of in vivo measurement of UHMWPE wear using PolyWare ™ when applied to digitised radiographs. The aim was to keep the cumulative errors below the accepted annual linear wear rate of 0.15 mm.

Method: Using precision phantoms with known cup and head sizes and known deviation simulating wear, series of x-rays were taken simulating a number of variables. These variables were grouped into: patient variables (centering, exposure, motion artefact, prosthesis orientation), image acquisition variables (film and cassette type, x-ray exposure, non-circularity of the projected image, magnification, image sharpness), digitisation variables (input resolution, sharpness), and errors inherent to the PolyWare™ software analytical process.

Results: Patient factors contributed the largest errors to the process – these were highly variable. Exposure and input resolution also contributed errors to a lesser extent. No significant error introduction was found with regard to any of the other above-mentioned factors, in particular the PolyWare™ analysis.

Conclusions: The three dimensional method (PolyWare™) is accurate and highly reproducible. Apart from patient factors, which directly and indirectly introduce errors, this method is a satisfactory means of estimating the in vivo wear of UHMWPE.