Wan L, de Asla R J, Rubash H E, Li G
Bioengineering Laboratory, Department of Orthopaedic Surgery, Massachusetts General Hospital/Harvard Medical School, Boston, MA 02114, USA.
Osteoarthritis Cartilage. 2006 Dec;14(12):1294-301. doi: 10.1016/j.joca.2006.05.012. Epub 2006 Jun 19.
The knowledge of in-vivo cartilage contact biomechanics is important to the understanding of the pathogenesis of joint diseases such as osteoarthritis. This study investigated the in-vivo contact areas of human talocrural joint under weightbearing conditions that simulated the stance phase of walking using a combined magnetic resonance (MR) and dual-orthogonal fluoroscopic imaging technique.
Nine healthy ankles of living subjects were recruited for this study. The in-vivo talocrural joint positions were recorded using the dual-orthogonal fluoroscopic images at three ankle positions that simulated those occurring during the stance phase of walking: heel strike, mid-stance, and toe off. Three-dimensional (3D) models of the talocrural joints were created from MR images and used to reproduce the in-vivo ankle positions recorded on the fluoroscopic images. The talocrural cartilage contact area was defined as the overlap area of the distal tibial and the proximal talar cartilage surfaces. The method was validated using an in-vitro experimental setup to evaluate its accuracy in determination of cartilage contact area.
The validation study demonstrated that the articular cartilage contact area of the talocrural joint determined using the imaging technique was approximately 4% lower than that of the experimental measurement. In the nine living ankles, the average cartilage coverage area was 964.9+/-156.1 mm(2) on the distal tibia and 1304.8+/-208.4 mm(2) on the proximal talus. The average talocrural cartilage contact areas were 272.7+/-61.1 mm(2) at heel strike, 416.8+/-51.7 mm(2) at mid-stance, and 335.7+/-64.5 mm(2) at toe off. The contact area at mid-stance was significantly larger than those at heel strike and toe off, while the contact area at toe off was significantly larger than that at heel strike.
The combined dual fluoroscopic and MR imaging technique was shown to be capable of determining in-vivo talocrural cartilage contact areas. During the simulated stance phase of walking, the contact areas were less than 44% and 31% of the cartilage coverage areas of the distal tibia and the proximal talus, respectively. These data may be useful for understanding in-vivo biomechanical function of the cartilage as well as the etiology of osteoarthritis.
了解体内软骨接触生物力学对于理解骨关节炎等关节疾病的发病机制很重要。本研究使用磁共振（MR）和双正交荧光透视成像技术相结合的方法，研究了在模拟步行站立阶段的负重条件下人体距小腿关节的体内接触面积。
招募了9名健康受试者的活体踝关节进行本研究。使用双正交荧光透视图像记录体内距小腿关节在模拟步行站立阶段出现的三个踝关节位置：足跟触地、站立中期和足趾离地时的位置。从MR图像创建距小腿关节的三维（3D）模型，并用于重现荧光透视图像上记录的体内踝关节位置。距小腿软骨接触面积定义为胫骨远端和距骨近端软骨表面的重叠区域。使用体外实验装置对该方法进行验证，以评估其在确定软骨接触面积方面的准确性。
验证研究表明，使用成像技术确定的距小腿关节的关节软骨接触面积比实验测量值低约4%。在9个活体踝关节中，胫骨远端的平均软骨覆盖面积为964.9±156.1平方毫米，距骨近端为1304.8±208.4平方毫米。距小腿软骨平均接触面积在足跟触地时为272.7±61.1平方毫米，站立中期为416.8±51.7平方毫米，足趾离地时为335.7±64.5平方毫米。站立中期的接触面积明显大于足跟触地和足趾离地时的接触面积，而足趾离地时的接触面积明显大于足跟触地时的接触面积。
双荧光透视和MR成像技术相结合被证明能够确定体内距小腿软骨接触面积。在模拟步行站立阶段，接触面积分别小于胫骨远端和距骨近端软骨覆盖面积的44%和31%。这些数据可能有助于理解软骨的体内生物力学功能以及骨关节炎的病因。
