M. Meier, J. Beckmann, Sportklinik Stuttgart, Stuttgart, Germany S. Zingde, Conformis Inc, Billerica, MA, USA A. Steinert, Krankenhaus Agatharied, Hausham, Germany W. Kurtz, Tennessee Orthopaedic Alliance, Nashville, TN, USA F. Koeck, MedArtes, Neutraubling, Germany.
Clin Orthop Relat Res. 2019 Mar;477(3):561-570. doi: 10.1097/CORR.0000000000000611.
Previous studies analyzing femoral components of TKAs have demonstrated the limited ability of these components to accommodate size variations seen in the patient population, particularly width and femoral offset.
QUESTIONS/PURPOSES: The purpose of this study was to use a large data set of knee CT scans (1) to determine the variations in the distal and posterior femoral geometries and to determine whether there is a correlation between distal condylar offset and posterior femoral offset as a potential parameter for symmetry/asymmetry; and (2) to evaluate what proportion of knees would have a substantial mismatch between the implant's size or shape and the patient's anatomy if a femoral component of a modern standard TKA of symmetric (sTKA) or asymmetric (asTKA) designs were to be used.
A retrospective study was performed on 24,042 data sets that were generated during the design phase for a customized TKA implant. This data set was drawn from European and US-American patients. Measurements recorded for the femur included the overall AP and mediolateral (ML) widths, widths of the lateral condyle and the medial condyle, the distal condylar offset (DCO) between the lateral and medial condyles in the superoinferior direction, and the posterior femoral offset (PFO) as the difference between the medial and lateral posterior condylar offset (PCO) measured in the AP direction. A consecutively collected subset of 2367 data sets was further evaluated to determine the difference between the individual AP and ML dimensions of the femur with that of modern TKA designs using two commercially available implants from different vendors.
We observed a high degree of variability in AP and ML widths as well as in DCO and PFO. Also, we found no correlation between DCO and PCO of the knees studied. Instances of a patient having a small DCO and higher PCO were commonly seen. Analysis of the DFOs revealed that overall, 62% (14,906 of 24,042) of knees exhibited DCO > 1 mm and 83% (19,955 of 24,042) of femurs exhibited a > 2-mm difference between the lateral and medial PCO. Concerning AP and ML measurements, 23% (544 of 2367) and 25% (592 of 2367) would have a mismatch between the patient's bony anatomy and the dimensions of the femoral component of ± 3 mm if they would have undergone a modern standard sTKA or asTKA design, respectively.
Analysis of a large number of CT scans of the knee showed that a high degree of variability exists in AP and ML widths as well as in DCO and PFO.
These findings suggest that it is possible that a greater degree of customization could result in surgeons performing fewer soft tissue releases and medial resections than now are being done to fit a fixed-geometry implant into a highly variable patient population. However, as an imaging study, it cannot support one approach to TKA over another; comparative studies that assess patient-reported outcomes and survivorship will be needed to help surgeons decide among sTKA, asTKA, and customized TKA.
先前分析 TKA 股骨部件的研究表明，这些部件对患者人群中所见的尺寸变化（尤其是宽度和股骨偏心距）的适应能力有限。
问题/目的：本研究的目的是使用大量膝关节 CT 扫描（1）确定股骨远端和后表面的几何形状变化，并确定远端髁间偏移与后股骨偏心距之间是否存在相关性，作为一种对称/不对称的潜在参数；（2）评估如果使用现代标准对称（sTKA）或不对称（asTKA）设计的股骨部件，植入物的尺寸或形状与患者解剖结构之间存在多大比例的严重不匹配。
对 24042 个在定制 TKA 植入物设计阶段生成的数据进行回顾性研究。该数据集来自欧洲和美国患者。测量股骨的参数包括整体 AP 和内外径（ML）宽度、外侧髁和内侧髁的宽度、外侧和内侧髁之间的远端髁间偏移（DCO）在上下方向上，以及后股骨偏心距（PFO）作为在 AP 方向上测量的内侧和外侧后髁间偏移（PCO）之间的差异。进一步评估了一个连续收集的 2367 个数据集，以确定使用来自不同供应商的两种市售植入物的现代 TKA 设计与股骨的个体 AP 和 ML 尺寸之间的差异。
我们观察到 AP 和 ML 宽度以及 DCO 和 PFO 具有高度的可变性。此外，我们发现研究中的膝关节 DCO 和 PCO 之间没有相关性。常见的情况是患者的 DCO 较小而 PCO 较高。DFO 的分析表明，总体而言，62%（24042 个中的 14906 个）的膝关节 DCO > 1mm，83%（24042 个中的 19955 个）的股骨在外侧和内侧 PCO 之间存在 > 2mm 的差异。关于 AP 和 ML 测量，23%（2367 个中的 544 个）和 25%（2367 个中的 592 个）如果接受现代标准 sTKA 或 asTKA 设计，患者的骨骼解剖结构与股骨部件的尺寸之间会存在 ± 3mm 的不匹配。
对大量膝关节 CT 扫描的分析表明，AP 和 ML 宽度以及 DCO 和 PFO 存在高度的可变性。
这些发现表明，更大程度的定制可能会导致外科医生进行更少的软组织松解和内侧切除，以适应固定几何形状的植入物到高度可变的患者人群。然而，作为一项影像学研究，它不能支持一种 TKA 方法优于另一种方法；需要比较性研究来评估患者报告的结果和生存率，以帮助外科医生在 sTKA、asTKA 和定制 TKA 之间做出选择。
