The Effect of Hip Position on the Length of Trochanteric Muscles: Potential Implications for Early Postoperative Management of Hip Arthroplasty

We investigated the effect several lower limb positions have on muscles that are detached to perform hip arthroplasty through posterior and lateral approaches. We used string models and computer navigation to measure the length changes in these muscles throughout hip movements in the anatomical planes and while simulating several sitting and lying postures. Piriformis and the obturators were shortened by sitting and lying postures when the femur was externally rotated and abducted; the clinical implication being that such postures have the potential to best protect their repair after a posterior approach. The anterior part of gluteus medius was lengthened with femoral external rotation. This lengthening was prevented, and therefore, theoretically, the gluteus medius repair protected after a lateral approach, by neutral or internal femoral rotation.