Introduction: Many types of prosthesis are currently used for total knee arthroplasty. Controversy exists as to whether mobile-bearing or fixed-bearing implants make any difference in achieving earlier or better movement, resulting in earlier patient discharge.

Aim: The purpose of our study was to compare the post-operative recovery and early results of 4 different mobile- and fixed-bearing knee implants.

Method: Between 19/7/05 and 15/6/07 202 knees were implanted into 190 patients. Patients were randomly selected for 1 of 4 implants (2 mobile-bearing, 2 fixed-bearing). Outcomes were assessed using the American Knee Society Score (AKSS) and range-of-movement, both pre-operatively and at 1 year post-operatively. Range-of-movement was also recorded on discharge.

Results: No significant difference was shown between the individual implant groups and the actual mean pre-operative and 1 year post-operative AKSS knee or functional scores or the change in knee score. A difference was noted however in the change in functional score between the 2 mobile-bearing knees (p=0.03). No significant difference was found between the 4 individual implants or the type of bearing used (mobile- or fixed-bearing) with regards to gender, age, length of stay or range-of-movement.

Conclusion: The type of implant used does not affect the early or 12 month outcomes in relation to range-of-movement, length of stay or AKSS knee scores.

Introduction: Modular prostheses were first developed for use in total hip arthroplasty (THA) in the 1980s as a potential solution to the problem of leg length inequality. There is much literature discussing the advantages and disadvantages of modularity in THA but there are few studies directly comparing modular and non-modular prostheses and their accuracy in restoring normal anatomy. Our aim was to assess whether modularity in THA improves the restoration of femoral offset and leg length.

Methods: An analysis of post-operative radiographs of 76 patients who underwent THA - 38 using modular and 38 using non-modular prostheses was undertaken. The femoral offset and leg length of the operated and un-operated hip were measured for each patient. Inter-and intra-observer errors were reduced to a minimum. A two-tailed T test was then applied to the data.

Results: Restoration of leg length (to within +/− 10mm of the un-operated hip) was achieved in 81.6% of patients in the non-modular group, compared to 78.9% in the modular group (p=0.60). On average, the modular system increases leg length of the operated hip by 0.64mm compared to the non-modular system, which reduces leg length by 3.76mm (p=0.016). The femoral offset is restored to within 5mm of the un-operated hip in 60.5% of modular THA and in 55.3% using a non-modular prosthesis (P=0.48). On average, modular prostheses increased offset by 0.85mm and non-modular prostheses by 0.15mm (P=0.64).

Discussion: The modular and non-modular hip prostheses are equally successful in achieving restoration of leg length and femoral offset to the pre-pathological state.