Abstract
Introduction
The direct anterior approach (DAA) and the posterior approach (PA) are 2 common total hip arthroplasty (THA) exposures. This prospective study quantitatively compared changes in periarticular muscle volume after DAA and PA THA.
Materials
Nineteen patients undergoing THA were recruited from the practices of 3 fellowship-trained hip surgeons. Each surgeon performed a single approach, DAA or PA. Enrolled patients underwent a preoperative MRI of the affected hip and two subsequent postoperative MRIs, averaging 9.6 and 24.3 weeks after surgery. Clinical evaluations were done by Harris Hip Score at each follow-up interval.
Results
MRIs for 10 DAA and 9 PA patients were analyzed. Groups did not differ significantly with regard to BMI, age, or pre-operative muscle volume. 1 DAA patient suffered a periprosthetic fracture and was excluded from the study. DAA hips showed significant atrophy in the obturator internus (−37.3%) muscle at early follow-up, with persistent atrophy of this muscle at the final follow-up. PA hips showed significant atrophy in the obturator internus (−46.8%) and externus (−16.0%), piriformis (−8.12%), and quadratus femoris muscles (−13.1%) at early follow-up, with persistent atrophy of these muscles at final follow-up. Loss of anterior capsular integrity was present at final follow-up in 2/10 DAA hips while loss of posterior capsular integrity was present in 5/9 PA hips. There was no difference in clinical outcomes.
Discussion
This study provides objective evidence that, regardless of surgical approach, a muscle whose tendon is detached from its insertion is likely to demonstrate persistent atrophy 6 months following THA. Although the study was not powered to compare clinical outcomes, it should be noted that no significant difference in patient outcomes were observed.
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