Aims

Pelvic reconstruction after the resection of a tumour around the acetabulum is a challenging procedure due to the complex anatomy and biomechanics. Several pelvic endoprostheses have been introduced, but the rates of complication remain high. Our aim was to review the use of a stemmed acetabular pedestal cup in the management of these patients.

Aims

Few studies dealing with chondrosarcoma of the pelvis are currently available. Different data about the overall survival and prognostic factors have been published but without a detailed analysis of surgery-related complications. We aimed to analyse the outcome of a series of pelvic chondrosarcomas treated at a single institution, with particular attention to the prognostic factors. Based on a competing risk model, our objective was to identify risk factors for the development of complications.

We present our results of cementless total hip arthroplasty with a tapered, rectangular stem made of titanium-aluminum-niobium alloy. This implant is used since 1979 with only minor modifications. The design of the femoral component achieves primary stability through precision rasping and press-fit implantation.

Between October 1986 and November 1987, two hundred consecutive patients (208 hips) underwent total hip arthroplasty with this tapered, rectangular stem. In all cases the acetabular component was a threaded cup made of titanium.

At a minimum follow-up of twenty years eighty-seven patients were still alive. Sixty-seven patients (69 hips) were available for clinical and radiographic follow-up. The probability of survival of the stem was 0.96 (95% confidence interval, 0.91 to 0.98) and that of the cup was 0.72 (0.62 to 0.80). The probability of survival of both the stem and the acetabular component with revision for any reason as the end point was 0.71 (0.61 to 0.78).

Two stems have been revised due to aseptic loosening. We found various degrees of osteolysis around the acetabular and femoral component (61,7%). At the time of the 20-year follow-up no stem was deemed at risk for loosening.

The key findings of our twenty-year follow-up are the very low rate of revisions of the femoral component and the low rate of distal femoral osteolysis associated with this stem. Our data show that femoral fixation of the stem continues to be secure at a follow-up of twenty years.

Scoliosis seen in the chicken after pinealectomy resembles adolescent idiopathic scoliosis in man. It has been suggested that in both species, deficiency of the pineal hormone, melatonin, is responsible for this phenomenon.

In nine patients with adolescent idiopathic scoliosis and in ten age- and gender-matched controls, the circadian levels of serum melatonin and the excretion of urinary 6-hydroxy-melatonin-sulphate, the principal metabolite of melatonin, were determined. There were no statistically significant differences in the secretion of serum melatonin or the excretion of urinary 6-hydroxy-melatonin-sulphate between the patients and the control group. The hypothesis of melatonin deficiency as a causative factor in the aetiology of adolescent idiopathic scoliosis cannot be supported by our data.

We compared two methods of reconstruction of the abductor mechanism in 15 patients after prosthetic replacement of the upper femur, to assess abductor strength and function.

Six patients in group I had direct fixation of the gluteus medius tendon and a segment of the original bone to the prosthesis. Nine patients in group 2 had the abductor tendon fixed to the iliotibial band. We assessed clinical function, isometric muscle strength and muscle cross-sectional area for each patient.

The patients in group 1 had better clinical and functional results (p = 0.059), with average peak torques for hip abduction of 92% of that in the non-operated leg in group 1, and of 57% in group 2. Group 1 had a mean muscle cross-sectional area of 69% and a mean value of strength per cross-sectional area of 134% when compared with the control side. The respective values for group 2 were 52% and 91%.

Direct fixation of the abductor muscles to the prostheses gave improved function and higher isometric abductor muscle force.

We determined serum cobalt levels in 55 patients by atomic absorption spectrophotometry before and after implantation of uncemented total hip arthroplasties. In a randomised, prospective trial 27 wrought Co-28Cr-6Mo-0.2C metal-on-metal articulations were compared with 28 ceramic-on-polyethylene hips which did not contain cobalt. Other sources of iatrogenic cobalt loading were excluded.

The metal-on-metal group produced detectable serum cobalt levels (median 1.1 μg/l after one year) which were significantly different (p < 0.0001) from those of the ceramic-on-polyethylene control group (median below detection limit of 0.3 μg/l after one year). Our findings indicate that metal-on-metal bearings generate some systemic release of cobalt.

From 1986 to 1991 we fitted 20 children with endoprostheses after resection of malignant bone tumours of the leg; six have reached skeletal maturity and are the subject of this study. Reconstruction of defects in growing limbs in which the eventual shortening can be predicted requires the use of extendable prostheses. The mean age at operation was 11 years (9.2 to 13.7) and the average follow-up period was 6.3 years (4.3 to 7.6). The diagnosis was osteosarcoma in five patients and Ewing's sarcoma in one. All tumours were Enneking stage-IIB. When seen for follow-up all patients were free from disease. The extendable implants used included the Pafford-Lewis prosthesis and the Kotz Modular Femur Tibia Reconstruction system with a compatible, newly-designed growth module. Telescope-like elongation of the prostheses was performed by insertion of a screwdriver through a small skin incision. Active epiphyseal growth in the adjacent growth plate was preserved by using prosthetic stems with a smooth surface. The mean length gained was 13.15 cm (4.5 to 19.5) requiring 53 planned procedures. Seven revision operations were necessary for complications. Functional evaluation showed excellent and good results in all cases. Stress-shielding at the site of anchorage of the prosthesis was more pronounced than in adults. Implantation of extendable endoprostheses in children provides a reasonable alternative to rotationplasty, but limb salvage requires more operations.