Our objective was to examine revision rates and patient reported outcome scores (PROMS) for cemented and uncemented primary total knee joint replacement (TKJR) at six months, one year and five years post-operatively. Patients and Methods: This matched cohort study involved secondary analyses of data collected as part of a large prospective observational study monitoring outcomes following knee replacement in Christchurch, New Zealand. Cemented and uncemented TKJR participants (n = 1526) were matched on age (± 5 years), sex and body mass index (BMI). From this larger sample, PROMS data, Oxford Knee Score and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), out to five years post-operatively were analysed for a matched subset of participants (n = 252).

The average age of participants was 67.9 years (SD 9.4, range 38-94). There were no differences between cemented and uncemented cohorts on the basis of age, sex, BMI or comorbidities, revision rates or PROMS outcomes. Cemented procedures had greater skin to skin times than uncemented procedures (p < 0.01). Unadjusted outcomes comparing risk for revision across the two participant cohorts did not significantly differ. Overall rates for revision were low (cemented 3.2% v uncemented 2.7%, p=0.70). Propensity adjusted associations between baseline characteristics (age, sex, BMI, comorbidity, baseline Oxford and baseline WOMAC scores) also revealed no differences in risk for revision at any post-operative timepoint.

In this large multi-surgeon matched cohort study there were no significant differences in functional outcomes or revision rates, when outcomes following modern cemented and uncemented TKJR were compared out to 5-year follow up. Based on our findings, uncemented TKJR is predictable irrespective of patient's age, BMI or gender

Cost is a factor in the choice of prosthetic components in joint replacement. For a given performance, the least expensive components are the most cost-effective. When evaluating a new prosthesis with an unknown outcome, the use of an economic model allows estimation of potential cost-effectiveness. We used published data for the survival of cemented total hip replacements from Sweden, and cost and demographic information from New South Wales, Australia, in such a model. In young active total hip recipients a new prosthetic design which offered a 90% improvement in survivorship over 15 years and a 15% reduction in the cost of revision surgery, could be sold at a price of 2 to 2.5 times that of conventional cemented components such as the Charnley Low Friction Arthroplasty and still be cost-effective. Using more likely estimates of the improved performance of new technology, however, the upper limit of cost-effectiveness is an increase of 1.5 to 1. Only a very small increase in the cost of a prosthesis could ever be justified for older patients of either sex. Most of the potential benefits of a better level of survivorship appear towards the end of the 15-year period. The results of modelling may be incorporated in clinical trial design. Given the known performance of some well-established and relatively inexpensive designs of prostheses, very large randomised studies would be required to prove an improvement in performance.

The effect of hypobaric spinal anaesthesia or narcotic-halothane-relaxant general anaesthesia on the incidence of postoperative deep vein thrombosis was studied in 140 elective total hip replacements in a prospective randomised manner. Deep vein thrombosis was diagnosed using impedance plethysmography and the 125I fibrinogen uptake test, combined, in selected cases, with ascending contrast venography. The overall incidence of deep vein thrombosis was 20%. Nine patients (13%) developed deep vein thrombosis in the spinal group and nineteen (27%) in the general anaesthetic group (p less than 0.05). The incidences of proximal thrombosis and of bilateral thrombi were also less with spinal anaesthesia than with general anaesthesia. It is concluded that spinal anaesthesia reduces the risks of postoperative thromboembolism in hip replacement surgery. The presence of varicose veins, being a non-smoker and having a low body mass index were associated with an increased incidence of deep vein thrombosis.

We have studied the incidence of tumours at remote sites following total hip replacement: 1,358 individuals have been followed up for 14,286 person-years after operation. In the decade following implantation the incidence of tumours of the lymphatic and haemopoietic systems was significantly greater, and that of cancer of the breast, colon, and rectum, significantly less than expected. Whilst the association might be due in part to an effect of the prosthetic implants, other mechanisms, particularly drug therapy, require consideration.

Problem drinking was found to be likely in 21% of inpatients in a general orthopaedic and fracture service, and in 42% of outpatients attending the fracture clinics. The questionnaire showed that the problem was most common among young men, particularly among outpatients. Previous hospital admissions were more frequent in this group. Many of the health problems associated with the chronic abuse of alcohol are directly relevant to orthopaedic practice. Early intervention may be highly successful, and it is recommended that screening for problem drinking be considered in orthopaedic and fracture services.

The outcome of primary management of acute osteomyelitis in 655 children treated in New Zealand between 1947 and 1976 is examined. Failure occurred in 20 per cent of children, in four-fifths of whom it was manifest by one year, and half of whom experienced one recurrence only. Lower failure rates were associated with use of bactericidal antibiotics, certain favourable sites, and age over 16 years. Surgical intervention was associated with significantly higher failure rates. The place of surgical intervention and the optimal duration of antibiotic treatment can only be determined by prospective clinical trials.