Impacts of external rotators and the ischiofemoral ligament on preventing excessive internal hip rotation: a cadaveric study

Kazuyoshi Baba,Atsushi Kogure,Hiroaki Kurishima,Soshi Hamada,Takehiro Sugaya,Yoshiyuki Kuwahara,Kumi Kamata,Itsuki Oizumi,Daisuke Chiba,Takayuki Suzuki,Yu Mori,Eiji Itoi,Toshimi Aizawa

doi:10.1186/s13018-021-02873-w

Kazuyoshi Baba, Atsushi Kogure + Show 11 more

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https://doi.org/10.1186/s13018-021-02873-w

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Abstract

BackgroundThis study examined the biomechanics of preventing excessive internal hip joint rotation related to the hip flexion angle.MethodAn intramedullary nail with a circular plate equipped with a protractor was installed in the femur of nine normal hips. The circular plate was pulled by 3.15 Nm of force in the internal rotation direction. The external rotators were individually resected, finally cutting the ischiofemoral ligament. The cutting order of the external rotators differed on each side to individually determine the internal rotation resistance. The external rotators were resected from the piriformis to the obturator externus in the right hips and the reverse order in the left hips. Traction was performed after excising each muscle and ischiofemoral ligament. Measurements were taken at 0°, 30°, and 60° of hip flexion, and the differences from baseline were calculated.ResultsFor the right hip measurements, the piriformis and ischiofemoral ligament resection significantly differed at 0° of flexion (p = 0.02), each external rotator and the ischiofemoral ligament resections significantly differed at 30° of flexion (p < 0.01), and the ischiofemoral ligament and piriformis and inferior gemellus resections significantly differed at 60° of flexion (p = 0.04 and p = 0.02, respectively). In the left hips, the ischiofemoral ligament and obturator externus, inferior gemellus, and obturator internus resections significantly differed at 0° of flexion (p < 0.01, p < 0.01, and p = 0.01, respectively), as did each external rotator and the ischiofemoral ligament resections at 30° of flexion (p < 0.01).ConclusionThe ischiofemoral ligament primarily restricted the internal rotation of the hip joint. The piriformis and obturator internus may restrict internal rotation at 0° and 60° of flexion.

Highlights

This study examined the biomechanics of preventing excessive internal hip joint rotation related to the hip flexion angle
For the right hip measurements, the piriformis and ischiofemoral ligament resection significantly differed at 0° of flexion (p = 0.02), each external rotator and the ischiofemoral ligament resections significantly differed at 30° of flexion (p < 0.01), and the ischiofemoral ligament and piriformis and inferior gemellus resections significantly dif‐ fered at 60° of flexion (p = 0.04 and p = 0.02, respectively)
The ischiofemoral ligament and obturator externus, inferior gemellus, and obturator internus resections significantly differed at 0° of flexion (p < 0.01, p < 0.01, and p = 0.01, respectively), as did each external rotator and the ischiofemoral ligament resections at 30° of flexion (p < 0.01)

Summary

Introduction

This study examined the biomechanics of preventing excessive internal hip joint rotation related to the hip flexion angle. The optimal soft-tissue balance to prevent hip dislocation has not yet been determined. The dislocation rate for patients who underwent a posterior surgical approach with capsular ligament repair was lower than patients without capsular ligament repair [5, 6]. These studies suggested that preserved soft tissues, including the capsular ligament and external rotators, help prevent excessive internal rotation and dislocation. The ischiofemoral ligament controls the internal rotation and extension of the hip [8]

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