Moyad Thomas F, Hughes Richard E, Urquhart Andrew
Sharp Health Care, San Diego, California 91942, USA.
Am J Orthop (Belle Mead NJ). 2011 Jul;40(7):348-52.
A malpositioned femoral component is an established risk factor for patellar instability and pain after total knee arthroplasty (TKA). In the assessment of femoral rotation, several axes, including the transepicondylar axis, the posterior condylar axis, and the anteroposterior axis, are useful. However, these axes are not always easily applicable, particularly when significant deformity exists. An anecdotal method used by some surgeons involves assessing the shape of the anterior femoral surface osteotomy. Our observations from saw bone models and TKA led to our hypothesis that proper femoral component placement is indicated by a bimodal peak on the anterior femur, approximately twice as high on the lateral side than on the medial side. We use the term "grand piano sign" to describe the shape of the trochlea after the osteotomy is correctly completed. To our knowledge, this common observation has not been studied either in the laboratory or in vivo. Our cadaveric models demonstrated that the grand piano sign correlated with proper femoral rotation during TKA. Surgeons who are knowledgeable about this marker should find it helpful when orienting components during knee replacement surgery.
股骨假体位置不当是全膝关节置换术（TKA）后髌骨不稳定和疼痛的既定危险因素。在评估股骨旋转时，包括经髁轴、后髁轴和前后轴在内的多个轴是有用的。然而，这些轴并不总是易于应用，尤其是在存在明显畸形的情况下。一些外科医生使用的一种经验方法涉及评估股骨前表面截骨的形状。我们从锯骨模型和TKA中的观察结果得出我们的假设，即正确的股骨假体放置由股骨前部的双峰峰值指示，外侧的峰值约为内侧的两倍。我们使用“三角钢琴征”一词来描述截骨正确完成后滑车的形状。据我们所知，这一常见观察结果在实验室或体内均未得到研究。我们的尸体模型表明，三角钢琴征与TKA期间正确的股骨旋转相关。熟悉这一标志的外科医生在膝关节置换手术中定位假体时应会发现它很有帮助。
