Meyer S A, Brown T D, Pedersen D R, Albright J P
Department of Orthopaedic Surgery, University of Iowa, Iowa City 52242, USA.
Am J Knee Surg. 1997 Summer;10(3):129-38.
Six fresh-frozen cadaver knee joints were used to study changes in retropatellar contact mechanics accompanying patella infera. The knees were tested on a servohydraulic testing machine under conditions simulating stair descent at 10 degrees, 30 degrees, 60 degrees, and 90 degrees of knee flexion. A slotted metallic block mechanism embedded in the region of the tibial tubercle allowed selective distal offset of the patellar tendon insertion so as to model conditions of 0, 6, 13, 19, and 25 mm of patella infera. Patellofemoral and quadriceps tendofemoral contact areas and contact stresses were recorded using Pressensor contact film and quantitated using digital image analysis. Patella infera significantly altered retropatellar contact mechanics. Contact areas migrated proximally on the patella and decreased in size with progressive severity of patella infera. However, the peak and spatial mean retropatellar contact stresses were not elevated correspondingly. Apparently, quadriceps tendofemoral contact was initiated at progressively lower angles of knee flexion as the patella infera progressed. Under conditions of extreme infera at high flexion angles, the magnitude of tendofemoral contact force approached that of retropatellar contact force. These data indicate that in patella infera, patellofemoral contact stresses are not elevated appreciably. Therefore, the disabling symptoms associated with patella infera may be due to factors other than local mechanical overload.
使用六个新鲜冷冻的尸体膝关节来研究低位髌骨时髌后接触力学的变化。在伺服液压试验机上对膝关节进行测试，模拟膝关节屈曲10度、30度、60度和90度时下楼梯的情况。嵌入胫骨结节区域的带槽金属块机构允许髌腱插入点进行选择性远端偏移，以模拟低位髌骨0、6、13、19和25毫米的情况。使用压力传感器接触膜记录髌股和股四头肌肌腱与股骨的接触面积和接触应力，并使用数字图像分析进行量化。低位髌骨显著改变了髌后接触力学。随着低位髌骨严重程度的增加，接触面积在髌骨上向近端迁移且尺寸减小。然而，髌后接触应力的峰值和空间平均值并未相应升高。显然，随着低位髌骨进展，股四头肌肌腱与股骨的接触在膝关节屈曲角度逐渐降低时开始。在高屈曲角度下极端低位髌骨的情况下，肌腱与股骨接触力的大小接近髌后接触力的大小。这些数据表明，在低位髌骨时，髌股接触应力没有明显升高。因此，与低位髌骨相关的致残症状可能是由局部机械过载以外的因素引起的。
