Spoor C W, van Leeuwen J L
Biomaterials Research Group, School of Medicine, Leiden University, The Netherlands.
J Biomech. 1992 Feb;25(2):201-6. doi: 10.1016/0021-9290(92)90276-7.
We tested magnetic resonance imaging (MRI) as a means to collect geometric data for moment arm estimation. A knee specimen in five successive flexion postures was scanned by MRI, while simultaneously tendon positions of loaded muscles were measured (long head of biceps femoris, lateral and medial gastrocnemius, gracilis, rectus femoris, sartorius, semimembranosus, semitendinosus, and tensor fasciae latae). Discrete rotation centres were derived from MRI pictures. Moment arms were estimated as the distances from these centres to the tendons. The ratio of tendon travel over the increment of joint angulation was the alternative, more reliable estimate of the moment arm. An important principal shortcoming of MRI is the impossibility of accounting for force distribution in taut tissue. As a consequence, for some muscles, considerable inaccuracies in moment arm estimation are found in a relatively small range of joint angulation (up to about 30% for the rectus femoris and semimembranosus). For the tensor fasciae latae, the moment arm cannot be estimated by MRI, while the estimate by tendon travel is unreliable owing to the deformability and attachments of the fascia lata.
我们测试了磁共振成像（MRI）作为收集用于估计力臂的几何数据的一种手段。通过MRI对处于五个连续屈曲姿势的膝关节标本进行扫描，同时测量受载肌肉的肌腱位置（股二头肌长头、腓肠肌外侧头和内侧头、股薄肌、股直肌、缝匠肌、半膜肌、半腱肌和阔筋膜张肌）。离散旋转中心由MRI图像得出。力臂被估计为从这些中心到肌腱的距离。肌腱行程与关节角度增量的比值是对力臂的另一种更可靠的估计。MRI的一个重要主要缺点是无法考虑紧绷组织中的力分布。因此，对于一些肌肉，在相对较小的关节角度范围内会发现力臂估计存在相当大的误差（股直肌和半膜肌高达约30%）。对于阔筋膜张肌，无法通过MRI估计力臂，而由于阔筋膜的可变形性和附着情况，通过肌腱行程进行的估计并不可靠。
