Background: Minimally invasive total hip arthroplasty has stirred substantial controversy with regard to whether it provides superior outcomes compared with total hip arthroplasty performed through longer incisions. The orthopaedic literature is deficient in well-designed scientific studies to support the clinical superiority of this approach. The objective of this study was to compare the results of a single mini-incision approach with those of a standard-incision total hip arthroplasty in the early postoperative period.

Methods: Two hundred and nineteen patients (219 hips) admitted for unilateral total hip arthroplasty between December 2003 and June 2004 were randomized to undergo surgery through a short incision of =10 cm or a standard incision of 16 cm. All patients were blinded to the size of the incision for the duration of the hospital stay. The anesthetic, analgesic, and postoperative physiotherapy protocols were standardized, with the staff also blinded to the technique used. A single surgeon, who had performed more than 300 short-incision hip replacements prior to the start of this study and who performs an average of 415 primary total hip replacements a year, performed all procedures through a single-incision posterior approach using a cementless cup and cemented stem.

Results: The two groups were matched for age, grade according to the system of the American Society of Anesthesiologists, and body mass index. No significant difference was detected with respect to postoperative hematocrit, blood transfusion requirements, pain scores, or analgesic use. We found no difference in early walking ability or length of hospital stay and no difference in component placement, cement-mantle quality, or functional outcome scores at six weeks. The patient variables significantly associated with a probability of early discharge independent of incision length were patient age and preoperative hemoglobin levels (p < 0.05). The surgical scars contracted significantly over six weeks (p < 0.05) but by a similar proportion of 11% to 12% in both groups.

Conclusions: Minimally invasive total hip arthroplasty performed through a single-incision posterior approach by a high-volume hip surgeon with extensive experience in less invasive approaches to the hip is safe and reproducible. However, it offers no significant benefit in the early postoperative period compared with a standard incision of 16 cm. As it is not known whether lower-volume and less-experienced surgeons can achieve similar results, the mini-incision technique merits further study before wide dissemination and implementation of this family of surgical approaches can be recommended.

Level of Evidence: Therapeutic Level I. See Instructions to Authors for a complete description of levels of evidence.