Department of Orthopaedic Surgery, Canisius Wilhelmina Hospital, Postbus 9015, Nijmegen, 6500 GS, The Netherlands.
Radboud University, Nijmegen, The Netherlands.
Knee Surg Sports Traumatol Arthrosc. 2020 Mar;28(3):869-875. doi: 10.1007/s00167-019-05531-1. Epub 2019 May 14.
Patella alta is a risk factor for patellofemoral pain and instability. Several measurement methods and imaging modalities are in use to measure patellar height. The first aim of this study was to determine the intra- and interrater reliability of different patellar height measurement methods on conventional radiography (CR), CT and MRI. The second aim was to examine the applicability of patellar height measurement methods originally designed for CR on CT and MRI.
Forty-eight patients who were treated for patellar instability were included. All patients had undergone a pre-operative conventional radiograph, CT scan and MRI. Five methods for measuring patellar height were performed on radiographs, CT and MRI by four observers. For each measurement, the intra- and interrater reliability was determined by calculating the intra-class correlation coefficient (ICC). A Bland-Altman analysis was performed for measurements with an ICC ≥ 0.70.
The Insall-Salvati (IS) ratio was the only measurement that showed good intra- and inter-observer reliability on CR, CT and MRI. The intra- and inter-observer reliability of the patellotrochlear index (PTI) for MRI was good to excellent for all observers. The IS ratio showed a moderate to good reliability for comparison of all three imaging modalities with the best agreement between radiography and MRI. The other patellar height measurements showed only poor to moderate inter-method agreement.
In this study, the Insall-Salvati ratio shows better intra- and inter-observer reliability than the Blackburne-Peel ratio, the Caton-Deschamps ratio and the modified Insall-Salvati ratio on all imaging modalities. Radiography and CT seem to have better reliability than MRI. The patellotrochlear index, however, shows good inter- and intra-observer reliability on MRI. Only for the IS method was there acceptable agreement between CR and MRI. This means that the established Insall-Salvati normal values could be used for MRI as well. This study shows that the most reliable method to measure patella height is the Insall-Salvati ratio measured on conventional radiographs or the patellotrochlear index on MRI.
Level II diagnostic.
髌骨高位是髌股疼痛和不稳定的一个危险因素。有几种测量方法和影像学手段可用于测量髌骨高度。本研究的第一个目的是确定常规 X 线摄影（CR）、CT 和 MRI 上不同髌骨高度测量方法的内部和观察者间可靠性。第二个目的是检查最初为 CR 设计的髌骨高度测量方法在 CT 和 MRI 上的适用性。
纳入 48 例因髌骨不稳定而接受治疗的患者。所有患者均接受了术前常规 X 线摄影、CT 扫描和 MRI 检查。由 4 位观察者在 X 线片、CT 和 MRI 上进行 5 种髌骨高度测量方法。对于每种测量方法，均通过计算组内相关系数（ICC）来确定内部和观察者间可靠性。对于 ICC≥0.70 的测量值，进行 Bland-Altman 分析。
Insall-Salvati（IS）比率是唯一一种在 CR、CT 和 MRI 上均显示出良好的内部和观察者间可靠性的测量方法。对于所有观察者，MRI 上的髌股指数（PTI）的内部和观察者间可靠性均为良好至优秀。IS 比率在比较所有 3 种影像学方式时具有中度至良好的可靠性，与 MRI 的一致性最好。其他髌骨高度测量方法仅显示出较差至中度的方法间一致性。
在这项研究中，与 Blackburne-Peel 比率、Caton-Deschamps 比率和改良的 Insall-Salvati 比率相比，Insall-Salvati 比率在所有影像学方式上均显示出更好的内部和观察者间可靠性。X 线摄影和 CT 的可靠性似乎优于 MRI。然而，MRI 上的髌股指数具有良好的内部和观察者间可靠性。只有 CR 和 MRI 之间的 IS 方法具有可接受的一致性。这意味着可以将既定的 Insall-Salvati 正常值用于 MRI。本研究表明，测量髌骨高度最可靠的方法是在常规 X 线片上测量 Insall-Salvati 比率或在 MRI 上测量髌股指数。
诊断 II 级。
