Introduction:

Release of some of the short external rotator tendons may be needed in the direct anterior approach (DAA) for Total Hip Arthroplasty (THA). It is unknown if these tendons heal. The purpose of this prospective study is to examine short external rotator tendon healing after release and the associated effect on muscle volume. In addition, we examined the relation with external rotation force and patient reported outcome measures (PROMs).

Methods:

In 21 DAA THA patients, preoperative MRI was compared with postoperative MRI at 6 weeks and 12 months. PROMs and rotation force of both hips were assessed. Tendon integrity and muscle volume of the obturator internus and piriformis were assessed on MRI using dedicated software.

Results:

In 5 patients all tendons remained intact, in 4 patients only the conjoined tendon was released and in 12 patients both the conjoined and piriformis were released. Obturator externus remained intact in all patients. In patients with tendon release, mean volume of obturator internus and piriformis muscle decreased 27% (SD 11) and 23% (SD 16) 6 weeks after surgery, respectively. Released tendons and muscle volume loss did not recover 12 months after surgery. We found no relation between tendon release and hip rotation force or PROMs.

Conclusions:

We found absent tendon healing and muscle volume loss when the conjoined or piriformis tendons were released. Although we found no relation between tendon detachment and hip force or PROMs, we have adapted our operative technique to make it more preserving for the piriformis.

中文翻译：

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前路髋关节置换术中的短外旋肌：肌腱是否愈合？一项前瞻性 MRI 研究

介绍：

在直接前路入路 (DAA) 进行全髋关节置换术 (THA) 时，可能需要释放一些短外旋肌腱。目前尚不清楚这些肌腱是否愈合。这项前瞻性研究的目的是检查释放后短外旋肌腱的愈合情况以及对肌肉体积的相关影响。此外，我们还研究了与外旋力和患者报告结果测量（PROM）的关系。

方法：

在 21 名 DAA THA 患者中，将术前 MRI 与术后 6 周和 12 个月时的 MRI 进行比较。对 PROM 和双髋旋转力进行了评估。使用专用软件通过 MRI 评估闭孔内肌和梨状肌的肌腱完整性和肌肉体积。

结果：

5 名患者所有肌腱均保持完整，4 名患者仅松解连体肌腱，12 名患者连体肌腱和梨状肌均松解。所有患者的闭孔外肌均保持完整。在接受肌腱松解的患者中，术后 6 周闭孔内肌和梨状肌的平均体积分别减少了 27% (SD 11) 和 23% (SD 16)。手术后 12 个月，释放的肌腱和肌肉体积损失仍未恢复。我们发现肌腱释放与髋部旋转力或 PROM 之间没有关系。

结论：

当联合肌腱或梨状肌腱被释放时，我们发现肌腱无法愈合并且肌肉体积减少。虽然我们发现肌腱脱离与髋部受力或 PROM 之间没有关系，但我们调整了手术技术，使其更能保护梨状肌。