Maeyama Akira, Naito Masatoshi, Moriyama Shigeaki, Yoshimura Ichiro
Department of Orthopaedic Surgery, Fukuoka University, 7-45-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan.
J Bone Joint Surg Am. 2008 Jan;90(1):85-92. doi: 10.2106/JBJS.G.00029.
Dysfunction of the hip secondary to dysplasia is a complex problem that includes excessive stresses on the articular cartilage, dynamic hip instability, and muscular fatigue, eventually leading to degenerative arthritis if left uncorrected. Mechanical stress on the dysplastic hip has been widely described, but dynamic instability requires further evaluation. The purpose of this study was to investigate dynamic instability of the dysplastic hip with use of triaxial accelerometry.
We evaluated forty-eight hips of twenty-four patients with unilateral hip dysplasia (a center-edge angle of <25 degrees ). All contralateral hips were disease-free with normal radiographic findings. An accelerometer was used to record triaxial acceleration while the patient was walking (x-axis: superoinferior direction, y-axis: anteroposterior direction, and z-axis: mediolateral direction). Sensors were attached to the skin, with adhesive tape, over the greater trochanter and the anterior superior iliac spine bilaterally. The time of heel-strike was confirmed visually and by superoinferior acceleration. The averages of the peak values of the middle three gait cycles were used for data analysis. The overall magnitude of acceleration was calculated to evaluate hip instability. The overall magnitudes of acceleration of the dysplastic and contralateral, normal hips were compared with the radiographic data.
The three directions of acceleration were the same in all cases. The overall magnitude of acceleration of the dysplastic hips was significantly larger than that of the contralateral, normal hips (p < 0.0001). There was a negative correlation between the overall magnitude of acceleration and both the center-edge angle and the acetabular head index, and there was a positive correlation between the overall magnitude of acceleration and both the acetabular roof angle and the Sharp angle.
Hip instability is increased in proportion to the degree of dysplasia. Triaxial accelerometry is helpful in the evaluation of dynamic instability of the dysplastic hip. The center-edge angle can be used as an indicator of hip instability.
发育异常继发的髋关节功能障碍是一个复杂的问题，包括关节软骨承受过大压力、髋关节动态不稳定和肌肉疲劳，如果不加以纠正，最终会导致退行性关节炎。发育异常髋关节的机械应力已得到广泛描述，但动态不稳定需要进一步评估。本研究的目的是使用三轴加速度计研究发育异常髋关节的动态不稳定。
我们评估了24例单侧髋关节发育异常（中心边缘角<25度）患者的48个髋关节。所有对侧髋关节均无疾病，影像学检查结果正常。在患者行走时，使用加速度计记录三轴加速度（x轴：上下方向，y轴：前后方向，z轴：内外侧方向）。传感器通过胶带双侧贴于大转子和髂前上棘上方的皮肤上。通过视觉和上下加速度确认足跟撞击时间。使用中间三个步态周期的峰值平均值进行数据分析。计算加速度的总体大小以评估髋关节不稳定。将发育异常髋关节与对侧正常髋关节的加速度总体大小与影像学数据进行比较。
所有病例中三个加速度方向相同。发育异常髋关节的加速度总体大小显著大于对侧正常髋关节（p<0.0001）。加速度总体大小与中心边缘角和髋臼头指数均呈负相关，与髋臼顶角和夏普角均呈正相关。
髋关节不稳定程度与发育异常程度成正比。三轴加速度计有助于评估发育异常髋关节的动态不稳定。中心边缘角可作为髋关节不稳定的指标。
