Department of Biomedical Engineering, University of California Davis, One Shields Ave, Davis, CA, 95616, USA.
THINK Surgical, 47201 Lakeview Blvd, Fremont, CA, 94538, USA.
Knee Surg Sports Traumatol Arthrosc. 2019 May;27(5):1504-1513. doi: 10.1007/s00167-018-5220-z. Epub 2018 Oct 24.
Kinematic alignment (KA) and mechanical alignment (MA) position the prosthetic trochlea that guides patellar tracking differently. The present study determined whether KA or MA more closely restores the groove location and sulcus angle of the prosthetic trochlea to the native trochlea for three femoral component designs.
Ten 3D femur-cartilage models were created by combining computer tomographic (CT) and laser scans of native human cadaveric femurs. Three femoral component designs were positioned using KA and MA. Measurements of the prosthetic and native trochlea were made along the arc length of the native trochlear groove. The alignment technique with the smaller absolute difference between prosthetic and native for the medial-lateral and radial locations of the groove and sulcus angle of the trochlea more closely restored the native trochlea.
For three femoral component designs, KA more closely restored to native the mean medial-lateral location (p = 0.0033 to < 0.0001) and mean radial location (p = 0.0150 to < 0.0001) than MA. For two femoral component designs, KA more closely restored to native the mean sulcus angle (p = 0.0326 to 0.0006) than MA. However, the differences in the mean sulcus angles between KA and MA were less than 2° for all three designs.
KA more closely restored the native trochlea, which explains why the reported risk of patellofemoral complications for KA is not higher than MA according to five randomized clinical trials. Small design modifications of the medial-lateral and radial locations and sulcus angle are strategies for restoring the native trochlea. Such modifications might further reduce the risk of patellofemoral complications.
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运动学对线（KA）和机械对线（MA）对假体滑车的定位方式不同，从而影响髌股轨迹。本研究旨在确定 KA 或 MA 更能恢复三种股骨假体组件设计的假体滑车的凹槽位置和滑车沟角。
通过对人体尸体股骨的计算机断层扫描（CT）和激光扫描，创建了 10 个 3D 股骨-软骨模型。使用 KA 和 MA 定位三种股骨假体组件。测量假体和原生滑车的轨迹，沿原生滑车槽的弧长进行测量。对于凹槽的内外侧位置和滑车沟角，对线技术中假体和原生的差值较小，更能恢复原生滑车。
对于三种股骨假体组件设计，KA 比 MA 更能恢复滑车的平均内外侧位置（p = 0.0033 至 < 0.0001）和平均半径位置（p = 0.0150 至 < 0.0001）。对于两种股骨假体组件设计，KA 比 MA 更能恢复滑车的平均沟角（p = 0.0326 至 0.0006）。然而，所有三种设计的 KA 和 MA 之间的平均沟角差异均小于 2°。
KA 更能恢复原生滑车，这可以解释为什么根据五项随机临床试验，KA 报告的髌股并发症风险并不高于 MA。对内外侧和半径位置以及沟角进行小的设计修改是恢复原生滑车的策略。这种修改可能会进一步降低髌股并发症的风险。
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