HP33: MINIMALLY INVASIVE HIP REPLACEMENT – A PROSPECTIVE RANDOMISED CONTROLLED TRIAL

Abstract

The aim of this study was to compare a single-incision minimally invasive posterior approach with a standard posterior approach in a double-blind prospective randomised controlled trial.

A pilot study was carried out to assess the efficacy of the minimally invasive (MI) approach. The protocol described in the CONSORT statement was used as a template for the study design. 100 Primary total hip replacements meeting the inclusion criteria were randomised in theatre to either the MI approach (using a small incision with preservation of piriformis and distal aspect of quadratus femoris) or the standard posterior approach. Hips meeting the inclusion criteria were randomised in theatre using sealed identical opaque envelopes. Patients were blinded to allocation and all patients remained in the group they were allocated to. Pre and post-operative care programmes were identical. Patients were scored by a blinded research physiotherapist pre-operatively, at Day 2, 2 weeks, 6 weeks and 3 months post operation. The primary outcome measure was function, assessed using the Oxford hip score, SF-12 questionnaire, Iowa score, 6-minute walk test and the number of walking aids required after 2 and 6 weeks post operatively. Secondary outcomes were complication rates, patient satisfaction, difficulty of the procedure as perceived by the surgeon, soft tissue trauma (CRP and blood loss) and radiographic analysis.

50 patients were recruited to each group. There was no difference in demographics Mean incision length was 12.8cm and 19.1cm respectively. There was no statistically significant difference in operation time, post-op functional recovery (ILOA score) or length of stay. Pain (VAS) was similar post-operatively, and at 6 and 12 weeks. There was no significant difference in 10 metre walking speed or 6 minute walking distance at 2, 6 or 12 weeks; nor was there a difference in Oxford hip score, patient satisfaction with surgery (VAS), or SF-12 score at 6 or 12 weeks. Blood loss, fall in haematocrit, transfusion rate and CRP rise were similar. There was no significant difference in cementation of the stem (Barrack) or cup position (Dorr). There was one death from PE in the MIS group and one deep infection in the standard group. There was one dislocation in the standard group. The only statistical difference between the groups was less dependence on walking aids at 2 and 6 weeks in the MIS group; there was no difference at 12 weeks.

MIS surgery is safe, and may allow earlier independent mobility after THR. However, the claims of significantly reduced pain, less morbidity, better function and improved patient satisfaction appear to be unfounded.