Background: 

Piriformis-sparing approaches to the hip allow surgeons to avoid releasing the piriformis tendon during total hip arthroplasty; however, the consequences of retracting an intact piriformis tendon during such an approach remain ill-defined. The present study aimed to determine the upper limit of force that can be applied during retraction of the piriformis tendon to expose the hip, and to quantify the resultant damage to the piriformis musculotendinous complex.

Methods: 

A patent-pending instrumented retractor was designed to record the applied force, duration, and angle of retraction during a piriformis-sparing posterior approach to the hip. In addition to the data collected with use of the instrumented retractor, damage to the piriformis muscle and tendon was quantified by a blinded observer.

Results: 

There was no damage to the piriformis tendon in 22 (96%) of 23 hips during piriformis retraction for visualization of the hip capsule; however, there was complete or partial damage to the piriformis muscle at the sacral origin, belly, or musculotendinous junction (i.e., outside the surgical field) noted in 21 (91%) of 23 hips. The mean peak force to failure of the piriformis muscle was exceedingly small (29.0 ± 9.4 N; range, 10.1 to 44.9 N).

Conclusions: 

The mean peak force applied to the piriformis retractor is much less than the force required for several common daily activities, such as opening a door or crushing an empty aluminum can. Soft-tissue damage that occurs outside the surgical field during the retraction of unreleased muscles, like the piriformis muscle, is common and remains an uncontrolled surgical variable. This inadvertent soft-tissue damage is not routinely accounted for when accessing the invasiveness of a procedure. Hence, it is no longer adequate to define a minimally invasive surgical procedure simply as an approach that involves the limited release of anatomical structures.

Clinical Relevance: 

The use of instrumented retractors may redefine surgical invasiveness by providing data that could alter our understanding of the soft-tissue damage caused by retraction and open the possibility of robot-assisted or damage-limiting retractor systems.

中文翻译：

---

少量的牵拉力会导致在保留梨状肌的髋关节入路过程中无意中出现梨状肌的损伤。

背景： 

保留梨状肌的方法允许外科医生在全髋关节置换术中避免释放梨状肌腱。然而，在这种方法中牵拉完整的梨状肌腱的后果仍然不确定。本研究旨在确定梨状肌腱缩回暴露髋部时可施加的力的上限，并量化对梨状肌肌腱复合体的最终损伤。

方法： 

设计了一项正在申请专利的器械牵开器，以记录在保留梨状肌的后路髋关节后路期间所施加的力，持续时间和牵开角度。除了使用仪器式牵开器收集的数据外，盲人观察者还对梨状肌和肌腱的损伤进行了量化。

结果： 

梨状肌回缩过程中对23个髋关节中的22个（96％）的梨状肌腱无损伤，可观察到髋关节囊。然而，在23个髋关节中有21个（91％）出现了the骨起源，腹部或肌腱连接处（即手术区域外）的梨状肌的全部或部分损伤。梨状肌衰竭的平均峰值力极小（29.0±9.4 N；范围为10.1至44.9 N）。

结论： 

施加在梨状肌牵开器上的平均峰值力远小于几种常见日常活动（例如打开门或压碎空的铝罐）所需的力。牵开梨状肌等未释放的肌肉时，在手术区域外发生的软组织损伤很常见，并且仍然是无法控制的手术变量。当进入手术的侵入性时，通常不会考虑这种无意的软组织损伤。因此，仅仅作为涉及有限的解剖结构释放的方法来定义微创外科手术不再是足够的。

临床相关性： 

通过使用提供数据的数据，可以改变我们对由牵开引起的软组织损伤的理解，并打开使用机器人辅助或限制牵开系统的可能性，可以使用器械式牵开器重新定义外科手术的侵入性。