Background: Few prospective randomized studies have demonstrated
benefits of minimally invasive total hip arthroplasty when compared with
conventional total hip arthroplasty. We hypothesized that patients treated
with a posterior mini-incision would have better results than those treated
with a posterior long incision with regard to the achievement of established
goals for pain relief and functional recovery permitting hospital discharge by
the second postoperative day.
Methods: Sixty of 231 eligible patients were randomized (with thirty
in each group) to have a total hip arthroplasty performed through either a
posterior mini-incision (10 ± 2 cm) or a traditional long incision (20
± 2 cm). After completion of the total hip arthroplasty, the
mini-incision group underwent extension of the skin incision to 20 cm.
Patients were evaluated on the basis of self-determined pain scores,
requirements for pain medicine, need for assistive gait devices, and time
until discharge. Gait analysis provided objective functional assessment.
Results: The average hospital stay was 63.2 ± 13.3 hours in
the mini-incision group and 73.6 ± 23.5 hours in the long-incision
group (p = 0.04). More patients with a mini-incision were discharged by the
second postoperative day (p = 0.003) and more were using just a single
assistive device at the time of discharge (p = 0.005). As scored on a verbal
analog scale of 0 to 10 points, patients with a mini-incision had less pain on
each postoperative day and the pain score remained significantly lower at the
time of discharge (mean, 2.2 ± 1.0 points compared with 3.1 ±
0.9 points in the long-incision group; p = 0.002). After hospital discharge,
there were no clinical differences in pain or function between the two groups
Conclusions: Compared with conventional total hip arthroplasty
performed through a posterior incision, posterior minimally invasive total hip
arthroplasty resulted in better early pain control, earlier discharge to home,
and less use of assistive devices. Subsequent evaluations at six weeks and
three months showed equivalency between the clinical results in the two
Level of Evidence: Therapeutic Level I. See Instructions
to Authors for a complete description of levels of evidence.