MIS approach to THA affects gait differences

By Elaine Fiedler

A pilot study investigating the early outcomes of three different approaches in minimally invasive (MIS) total hip arthroplasties (THA) found differences in gait, depending on the approach taken, according to the presenters of Paper 203.

Investigators compared differences in gait pattern recovery and functional outcomes among three groups of MIS THA patients to an age-matched control group. In particular, they investigated differences in external hip joint moments and the time-distance parameters of speed, stride and cadence.

The study included a total of 30 patients with unilateral osteoarthritis at the hip who underwent THA. Two orthopedic surgeons using the following three MIS approaches performed all hip replacements: (1) two-incision, no muscle cut/or overly stretched; (2) single anterolateral incision, partial incision of the gluteus medius muscle and part of the minimus; and (3) single posterior incision, partial incision of the external rotator muscles.

Gait analysis was performed at 3, 6 and 12 weeks postoperatively using standard protocols. The Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index and the Harris Hip Score (HHS) were used to study pain and function status of the hip joints.

In the two-incision MIS group (Group 1), 11 of 12 patients were able to walk without crutches 3 weeks after surgery. At that point, only three of 11 patients in the single incision anterolateral MIS group (Group 2) and one out of seven patients in the single incision posterior MIS group (Group 3) were able to walk without support.

At six weeks, stride length, cadence and speed were higher (p<0.001) in Group 1 than in Group 2 or Group 3 and similar to normal. HHS and WOMAC score increased for every patient following surgery. Group 1 reached the highest score at 6 weeks (95 5) without much further improvement thereafter. The authors noted, “by 12 weeks after surgery the Harris hip score for Group 1 was 96 ( 9) indicating that most of these subjects had excellent clinical results. Scores in the other groups also indicated good to excellent clinical outcomes at 12 weeks after surgery: 84 ( 10) for Group 2, and 93 ( 5) for Group 3. Subjects in Group 1 had a significantly higher HHS score at both 6 and 12 weeks after surgery (p < 0.015). There were no significant differences in the WOMAC scores for the three groups at either 6 or 12 weeks after surgery (p > 0.089).”

All patients, regardless of surgical approach, showed significantly decreased hip extension moments when compared to the normal control group at 6 and 12 weeks postoperative (p<0.001). The internal rotation moment was also significantly reduced compared to normal in all THR groups at 6 weeks postoperative (p < 0.003). The internal rotation moment returned to normal by 12 weeks after surgery only in Group 1.

Minimally invasive surgery has shown excellent short-term outcome and recovery in total hip arthroplasty. However, MIS remains a controversial surgical technique. Some studies question MIS outcomes compared with standard procedures. Generally, researchers agree that surgeons must be educated and experienced in MIS techniques to get better results.

The researchers concluded by saying that their pilot study demonstrated differences in early functional outcome as well as differences in gait, depending on the MIS approach used. However, there were modest differences among the three groups in joint loading. The researchers observed that, in general, all the patients recovered faster with MIS than with conventional surgery.

Investigators included Madelaine Hildebrand, MD of Halle, Germany, and Kirsten.C. Moisio, PT, PhD; Markus A. Wimmer, PhD; Craig J. DellaValle, MD; Richard A. Berger, MD; and Jorge O. Galante, MD—all of Chicago.

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