Glass ionomer cement (Ionocem) was developed for use in bone surgery and is reported to be notably biocompatible. Between 1991 and 1994 we performed revision operations for aseptic loosening of arthroplasties of the hip on 45 patients using this material in its granulate form (Ionogran) mixed with homologous bone as a bone substitute. Of these 45 patients, 42 were followed up for a mean of 42 months. Early reloosening of the acetabular component has occurred in ten after a mean of 30 months. Histological examination showed large deposits of aluminium in the adjacent connective tissue and bone. Osteoblastic function and bone mineralisation were clearly inhibited. The serum levels of aluminium were also increased. The toxic damage at the bone interface caused by high local levels of aluminium must be seen as an important factor in the high rate of early reloosening. Our findings cast doubt on the biocompatibility of this material and we do not recommend continuation of its further use in orthopaedic surgery.

We report the 12 to 74 month results of our mark I saddle prosthesis after its use as a salvage device for gross loss of pelvic bone stock in 76 patients with failed hip arthroplasties. The implant transmits load between iliac bone and bare polish chrome-cobalt. Our clinical and radiological results indicate that a useful and stable articulation can be achieved in most cases, provided that continued deep infection can be avoided. The appearance of radiological sclerosis at the bearing site in successful cases seems to indicate that significant late migration will not occur. Based on our experience with the mark I prosthesis we have designed and developed a mark II model which has freedom of axial rotation of the saddle. Our early results in 40 cases show a significant improvement over the results which could have been predicted for the mark I device.

The use of a total femoral prosthesis can offer a realistic alternative to amputation or disarticulation. The limited indications for such a prosthesis in the surgical management of primary bone tumours and pathological fractures still exist. In this specialised clinic there is an increased need to replace the entire femur where repeated procedures have failed, from loss of bone stock with infection or because of non-union in the presence of a prosthesis. Over the past eight years, four basic models have been developed. The most recent designs allow for the preservation of non-involved bone or for stable support where there is complete acetabular destruction.

Exchange operation is recommended as the treatment of choice for most deep infections involving a total hip replacement. This revision arthroplasty comprises, in one stage, excision of soft tissue, removal of implant and cement, replacement with an appropriate implant using Palacos R acrylic cement loaded with an appropriate antibiotic and, more recently, systemic antibiotics. During our first 10 years without systemic antibiotics we have achieved an overall 77 per cent success rate from a first attempt in 583 patients and a 90 per cent success rate after subsequent exchange procedures. Morbidity is significant but acceptable. Success is defined as control of infection, no loosening, and useful function. The factors associated with failures include, in particular, specific infections (Pseudomonas group, Streptococcus group D, Proteus group, and Escherichia coli), delay in operation and inadequate antibiotic dosage in the cement.

Eleven patients underwent disarticulation for infected arthroplasty of the hip. Exchange total hip arthroplasty or conversion to a Girdlestone excision arthroplasty had been undertaken previously an average of 2.9 times. The indications for disarticulation were as a life-saving measure, or as a result of severe infection of soft tissue and bone, loss of bone stock, or vascular injury. While the indications for this drastic operation were highly individual, there were instances where disarticulation could have been avoided if repeated exchange operations had been eschewed in deference to a Girdlestone procedure.