Background

To elucidate the formation process and therapeutic targets of hip flexion contracture, we developed a rat model of hip flexion contracture induced by hip mono-articular immobilization.

Methods

Kirschner wires inserted into the femur and hip bone were anchored at the hip in a flexed position in the immobilization groups and unanchored in the sham groups for up to four weeks. Age-matched untreated rats were used as controls. Hip extension range of motion (RoM) was measured at three different extension moments (7.5, 15, and 22.5 N•mm) in each successive myotomy step as follows: before myotomy, after sequential myotomy of the tensor fascia lata, quadriceps muscle, iliopsoas muscle, and after myotomy of all residual muscles (the gluteus medius and adductor muscles). Histological analysis of the hip joint was also performed.

Findings

After four weeks of immobilization, the RoM before myotomy at 22.5 N•mm was significantly decreased by 29° compared with controls, and this value was unaltered in the sham group. Analyses following serial myotomy suggested that the structures responsible for myogenic contracture were the tensor fascia lata, iliopsoas, gluteus medius, and adductor muscles because the RoMs were increased by these myotomies. Unexpectedly, arthrogenic contracture was not detected at moments other than at 7.5 N•mm, even after four weeks of immobilization. Histological analysis confirmed that pathological changes were not apparent in the anterior capsule of the hip joint.

Interpretation

The present findings suggest that myogenic contracture may be an important therapeutic target for immobilization-induced hip flexion contracture.

中文翻译：

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单关节髋关节固定致大鼠髋关节挛缩模型

背景

为了阐明髋关节屈曲挛缩的形成过程和治疗目标，我们建立了髋关节单关节固定诱导的髋关节屈曲挛缩大鼠模型。

方法

插入股骨和髋骨的克氏针在固定组中以弯曲位置锚定在髋部，而在假手术组中不锚定长达 4 周。年龄匹配的未处理大鼠用作对照。髋关节伸展运动范围 (RoM) 在三个不同的伸展时刻（7.5、15 和 22.5 N•mm）在每个连续的肌切开步骤中测量如下：肌切开前、阔筋膜张肌、股四头肌、髂腰肌连续肌切开后肌肉，以及所有残余肌肉（臀中肌和内收肌）的肌切开术后。还进行了髋关节的组织学分析。

发现

固定4周后，肌切开前22.5 N•mm的RoM与对照组相比显着降低了29°，并且该值在假手术组中没有改变。连续肌切开后的分析表明，导致肌源性挛缩的结构是阔筋膜张肌、髂腰肌、臀中肌和内收肌，因为这些肌切开增加了 RoM。出乎意料的是，即使在固定 4 周后，在 7.5 N•mm 以外的时刻也没有检测到关节挛缩。组织学分析证实髋关节前囊病理变化不明显。

解释

目前的研究结果表明，肌源性挛缩可能是固定引起的髋关节屈曲挛缩的重要治疗靶点。