Salzmann Mikhail, Kropp Ellen, Prill Robert, Ramadanov Nikolai, Adriani Marco, Becker Roland
Center or Orthopaedics and Traumatology, University Hospital Brandenburg/Havel, Brandenburg Medical School Theodor Fontane, Brandenburg, Germany.
Faculty of Health Sciences Brandenburg, Brandenburg Medical School Theodor Fontane, Brandenburg, Germany.
Bone Jt Open. 2024 Dec 2;5(12):1067-1071. doi: 10.1302/2633-1462.512.BJO-2024-0140.R1.
The transepicondylar axis is a well-established reference for the determination of femoral component rotation in total knee arthroplasty (TKA). However, when severe bone loss is present in the femoral condyles, rotational alignment can be more complicated. There is a lack of validated landmarks in the supracondylar region of the distal femur. Therefore, the aim of this study was to analyze the correlation between the surgical transepicondylar axis (sTEA) and the suggested dorsal cortex line (DCL) in the coronal plane and the inter- and intraobserver reliability of its CT scan measurement.
A total of 75 randomly selected CT scans were measured by three experienced surgeons independently. The DCL was defined in the coronal plane as a tangent to the dorsal femoral cortex located 75 mm above the joint line in the frontal plane. The difference between sTEA and DCL was calculated. Descriptive statistics and angulation correlations were generated for the sTEA and DCL, as well as for the distribution of measurement error for intra- and inter-rater reliability.
The external rotation of the DCL to the sTEA was a mean of 9.47° (SD 3.06°), and a median of 9.2° (IQR 7.45° to 11.60°), with a minimum value of 1.7° and maximum of 16.3°. The measurements of the DCL demonstrated very good to excellent test-retest and inter-rater reliability coefficients (intraclass correlation coefficient 0.80 to 0.99).
This study reveals a correlation between the sTEA and the DCL. Overall, 10° of external rotation of the dorsal femoral cortical bone to the sTEA may serve as a reliable landmark for initial position of the femoral component. Surgeons should be aware that there are outliers in this study in up to 17% of the measurements, which potentially could result in deviations of femoral component rotation.
髁上轴是全膝关节置换术（TKA）中确定股骨假体旋转的公认参考标准。然而，当股骨髁存在严重骨丢失时，旋转对线可能会更加复杂。股骨远端髁上区域缺乏经过验证的标志点。因此，本研究的目的是分析手术髁上轴（sTEA）与冠状面建议的背侧皮质线（DCL）之间的相关性及其CT扫描测量的观察者间和观察者内可靠性。
由三位经验丰富的外科医生独立测量75例随机选择的CT扫描图像。DCL在冠状面被定义为与额状面关节线上方75 mm处股骨背侧皮质相切的线。计算sTEA与DCL之间的差异。对sTEA和DCL以及测量误差分布进行描述性统计和角度相关性分析，以评估观察者内和观察者间的可靠性。
DCL相对于sTEA的外旋平均为9.47°（标准差3.06°），中位数为9.2°（四分位间距7.45°至11.60°），最小值为1.7°，最大值为16.3°。DCL测量显示出非常好至极好的重测和观察者间可靠性系数（组内相关系数0.80至0.99）。
本研究揭示了sTEA与DCL之间的相关性。总体而言，股骨背侧皮质骨相对于sTEA外旋10°可作为股骨假体初始位置的可靠标志点。外科医生应意识到本研究中高达17%的测量存在异常值，这可能导致股骨假体旋转偏差。
