Abstract
PurposeThe 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).MethodsMRI 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.ResultsA 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.ConclusionIn 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.
Highlights
Chronic Achilles tendinopathy represents a common disease that can affect professional athletes [1] and people engaging occasionally in sports or even having a sedentary lifestyle [2]
The purpose of this study was to outline this finding on magnetic resonance imaging (MRI), based on the hypothesis that patients with Achilles tendinopathy would present with secondary hypertrophy of the flexor hallucis longus muscle (FHL)
Similar results were obtained by calculating the ratio regarding the area Ar (FHL/triceps surae (TS)), which showed significantly higher values in the tendinopathy group than in the control group (1.8 [1.3] vs 1.3 [0.7]), p < 0.001
Summary
Chronic Achilles tendinopathy represents a common disease that can affect professional athletes [1] and people engaging occasionally in sports or even having a sedentary lifestyle [2]. In 2011, its incidence in a Dutch population was described as 2 per 1000 patients registered by a general practitioner (GP) [3]. 34% of the Achilles tendon specimens of spontaneously ruptured. First line of treatment is usually conservative and may take up months to demonstrate effectiveness. This includes reduction of load, stretching as well as eccentric muscle strengthening and may lead to a favorable outcome in 71% of the cases [5]. A variety of surgical options have been described without a definitive consensus on the best technique [9]
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