Minimally invasive surgery (MIS) for THR may accelerate rehabilitation. The objectives of this study were to determine the effect of 3 surgical approaches (standard, mini (< 10cm), 2 incision Stryker approach (MIS), on length of stay, rehabilitation rates, clinical outcome, quality of life, patient safety, complications and implant position.

This study was conducted in accordance with Good Clinical Practice. Each surgeon completed 6–8 documented cases using the MIS technique before commencing enrolment to eliminate any learning curve effect. Prior to enrolment patients were assessed for eligibility and provided signed informed consent. Patient demographics, medical histories and surgical details were collected. Post-operative rehabilitation was independently documented by a physiotherapist. Clinical evaluations (HHS) were collected pre-operatively, 10 days, 6 weeks, 3 months and 1 year. Patient outcomes (SF 12/WOMAC) were collected pre-operatively and 1 year. Radiological evaluations were completed at 6 weeks. CTs/x-rays were subject to an independent review.

A sample size of 48 patients was determined based on the primary objective – length of stay. Enrolment commenced at the end of 2002 and these results are based on the first cohort of patients; based on current recruitment rates, the authors anticipate that the majority of patients will be enrolled by presentation time.

Preliminary results show mean incision lengths (cm) of 3.5/5.8 for the 2 incision MIS compared to 8.8 and 13.5 for the mini and standard respectively. Mean duration of surgery (mins) was 79 (MIS), 62 (mini) and 42 (standard). The median time (hours:minutes) from end of surgery until the first episode of knee flexion > 45°, straight leg raise, active abduction, standing, out of/in to bed, stair climbing and walking > 20 metres was shortest for MIS compared to mini and standard surgical approaches. The maximum distance walked was greatest for the MIS group. The mean length of stay (days) was shortest for the MIS group. 2.5 compared to 4.7 (mini) and 3.7 (standard).

Mean blood loss (cc) was greatest for the MIS group, 667 compared to 525 (mini) and 467 (standard). There were no intra/post-operative complications or blood transfusions.

Results suggest accelerated rehabilitation, decreased hospital stay and increased surgery duration for the MIS group. There are no safety concerns, however the procedure is felt to be quite technically demanding requiring an appropriate level of training/experience. The authors believe this is the only controlled study of this nature currently being conducted internationally.