Comparison of early postoperative functional levels following total hip replacement using minimally invasive versus standard incisions. A prospective randomized blinded trial

Objective: To compare the results of single-incision minimally invasive total hip replacement (<= 10 cm) to standard-incision (16 cm) total hip replacement in the early postoperative period with respect to functional and mobilizing ability (transfers, mobilizing, walking and stair assessment). Setting: Orthopaedic wards of a regional orthopaedic centre. Subjects: Two hundred and nineteen total hip replacement patients were tested between December 2003 and June 2004. Interventions: Patients were randomized to either total hip replacement through a minimally invasive (<= 10 cm) or standard incision (16 cm). A single surgeon performed all procedures using the same type of component fixation. Postoperative physiotherapy assessment and treatment was standardized. Analgesia was also standardized. All patients, physiotherapy staff and assessors were blinded to the incision used. Main outcome measures: Patients were tested two days post operatively and were assessed for the following activities: transfer from supine to sit, transfer from sitting to standing, mobilizing, ascending and descending stairs and weight-bearing. Results: The shorter incision offered no significant improvement in patient ability in relation to transfer from lying to sitting, transfer from sitting to standing, mobilizing or weight-bearing. Ascending/descending stairs gave a total time for the minimal incision of 38.7 s against 40.8 s for a standard incision. There was no difference in walking velocity between the standard incision and minimal incision groups two days post operatively (minimal incision = 0.26 m/s versus standard incision = 0.26 m/s) or six weeks post operatively (minimal incision = 0.90 m/s versus standard incision 0.93 m/s). There was no difference between groups with respect to walking aids at six-week review. The mean length of stay for the minimally invasive approach was 3.65 days (SD 2.04) against 3.68 days (SD 2.45) for the standard approach. This was not significantly different. Conclusion: Total hip replacement performed through a minimally invasive incision of <= 10 cm compared with a standard incision of 16 cm offers no significant benefit in terms of the rate or ability of patients to mobilize and perform functional tasks necessary for safe discharge.