Department of Orthopaedics, Balgrist University Hospital, University of Zurich, Forchstrasse 340, 8008, Zurich, Switzerland.
Eur J Orthop Surg Traumatol. 2021 Oct;31(7):1387-1393. doi: 10.1007/s00590-021-02891-8. Epub 2021 Feb 8.
The purpose of this study was to outline an indirect sign of advanced Achilles tendinopathy on magnetic resonance imaging (MRI), based on the hypothesis that these patients would present with secondary hypertrophy of the flexor hallucis longus muscle (FHL).
MRI scans of Achilles tendon were analyzed retrospectively in two cohorts. The study group consisted of consecutive patients presenting with clinical signs of Achilles tendinopathy and no previous surgeries, while the control group were patients that had an MRI due to other reasons and no signs of tendinopathy. Two parameters from two muscle bellies were measured and compared on axial MRI scans 4-5 cm above the ankle joint line at the level of greatest thickness: area and diameter of the triceps surae (TS) and of the FHL muscle. Ratios (FHL/TS) were calculated for area (Ar) and diameter (Dm) measurements. Interobserver agreement was analyzed. A receiver operating characteristic (ROC) curve was created for both ratios to assess potential cutoff points to differentiate between the groups.
A total of 60 patients for each study group were included. Both ratios Ar(FHL/TS) and Dm(FHL/TS) showed significant higher values in the tendinopathy group (p < 0.001). There were strong to very strong intraclass correlation coefficients (ICC = 0.75-0.93). A diameter ratio Dm (FHL/TS) of 2.0 or higher had a sensitivity of 49% and specificity of 90% for concomitant Achilles tendinopathy.
In our patient cohort, FHL hypertrophy was observed in patients with Achilles tendinopathy as a possible compensatory mechanism. Measuring a diameter ratio Dm(FHL/TS) of 2.0 or higher on an axial MRI, may be indicative as an indirect sign of functional deterioration of the Achilles tendon.
本研究旨在基于患者可能存在比目鱼肌（FHL）继发性肥大的假设，概述磁共振成像（MRI）上一种跟腱病变的间接征象。
本研究回顾性分析了两批跟腱 MRI 扫描。研究组为连续出现跟腱病变临床征象且无既往手术史的患者，对照组为因其他原因行 MRI 检查且无跟腱病变征象的患者。在距踝关节线 4-5cm 处的跟腱最厚处的轴位 MRI 扫描上测量并比较两个肌腹的两个参数：三头肌（TS）和 FHL 肌的面积和直径。分别计算面积（Ar）和直径（Dm）测量的 FHL/TS 比值。分析了观察者间的一致性。为两种比值创建了受试者工作特征（ROC）曲线，以评估潜在的临界值来区分两组。
每个研究组均纳入了 60 名患者。病变组的 Ar（FHL/TS）和 Dm（FHL/TS）比值均显著更高（p<0.001）。组内相关系数（ICC）为 0.75-0.93。FHL/TS 直径比（Dm）为 2.0 或更高时，对合并跟腱病变的敏感度为 49%，特异度为 90%。
在我们的患者队列中，跟腱病变患者中观察到 FHL 肥大，这可能是一种代偿机制。在轴位 MRI 上测量 FHL/TS 直径比（Dm）为 2.0 或更高，可能是跟腱功能恶化的间接征象。
