Prospective and comparative study of minimally invasive posterior approach versus standard posterior approach in total hip replacement.

Introduction: Minimally posterior approach in total hip replacement(THR) is topical. We studied its interest with regard to standardpostero-lateral approach.Material and Method: It was a prospective, comparative and continuousstudy. Major architectural disorders and revision arthroplastywere excluded. One hundred and sixteen total hip replacements(110 patients) were included, divided into two groups ofequal size. We performed the two approaches with standard instruments.The same implants were used. Duration of operative procedure,haemoglobin level, and haematocrit at day 1 and 5, transfusionvolume, postoperative pain and implant positioning werenoted. Average operative blood loss was calculated by mean ofhaematocrit rate and transfusion. Clinical status was evaluated byHarris hip score (HHS) and WOMAC Osteoarthritis Indexpreoperatively and postoperatively (6 weeks, 3 and 6 months).A p<0.05 was considered significant.Results: Preoperative data were comparable with respect to age,sex, body mass index, diagnosis and preoperative functional scores.ASA score was lower in the mini-incision group (p=0.04). Averageincision length was 8,5 cm versus 15,1 cm. Average calculated totalblood loss was lower in mini-posterior approach (p=0.027) as waspostoperative pain, confirmed by less morphine use (p = 0.006).WOMAC Osteoarthritis Index was significantly better in miniposteriorapproach at 6 weeks, 3 and 6 months (respectivelyp=0.005, p=0.02 and p=0.01) and HHS at 6 weeks (p<0.05). Later,functional results and pain became comparable. Other postoperativedata (transfusion rate, duration of hospitalisation and implant positioning)were comparable. We observed no major complication inthe mini-posterior approach group but one peroneal palsy, 2 dislocationsand 2 periprosthetic fractures, secondary to falls, in theother group.Discussion and Conclusion: Blood loss and postoperative pain areless in mini-posterior approach. It allows an earlier and a fasterrecovery. This approach needs no specific instrumentation, no orthopaedictable and no fluoroscopy. It allows a satisfying and reproducibleimplant positioning. The complication rate is similar. Earlyclinical results are better but become comparable after 6 weeks. Themini-posterior approach is a reliable and reproducible approach. Itrequires a learning period. Conversion into standard postero-lateralapproach is possible if necessary.