Purpose: Kinematic studies have shown that patients with a total hip arthroplasty (THA) walk with different gait characteristics compared to normal subjects. This abnormal gait might result from difficulties restoring the normal hip anatomy and biomechanics with THA. Surface replacement arthroplasty (SRA) facilitates leg length management and reconstruction of the normal anatomy of the proximal femur, allowing potential improvements in muscle power, proprioception and hip stability compared to THA.

Method: Patients suffering from advanced hip joint disease were randomised to receive an uncemented metal-metal THA or metal-metal SRA. A group of patients from this study were evaluated pre operatively, at 6 months and one year post operatively at a gait laboratory. A VICON system with 8 cameras, platform (AMTI) and surface electromyograph (Motion Lab) were used. Articular and muscle power and work characteristics of the hip, knee and ankle were analysed with different tasks. Postural stability (e.g. distance between the mass centre and pressure centre) in the standing position will serve to differentiate the 2 groups. Other specific tests, such as the hop test, the step test and the TUG test, were performed.

Summary of Results: Thirty randomised patients were evaluated. The results will be presented and discussed.

Discussion: Considering the strong interest of patients and surgeons for the potential functional benefits of surface replacement arthroplasty, it is necessary to determine scientifically how it compares with the standard of care (THA). Patient age, weight, sex and pre operative function have a strong influence on the post operative function. Thus, a prospective randomised study is mandatory to obtain valid results.

Significance: We strongly believe that this subject warrants special attention considering the possible benefits associated with this technique in the young adult with hip osteoarthitis.