Non-uniform displacement within ruptured Achilles tendon during isometric contraction.

Ra’Ad M Khair,Neil J Cronin,Lauri Stenroth,Annamária Péter,Aleksi Reito,Juha Paloneva,Taija Finni

doi:10.1111/sms.13925

Abstract

The purpose of this study was investigate tendon displacement patterns in non-surgically treated patients 14months after acute Achilles tendon rupture (ATR) and to classify patients into groups based on their Achilles tendon (AT) displacement patterns. Twenty patients were tested. Sagittal images of AT were acquired using B-mode ultrasonography during ramp contractions at a torque level corresponding to 30% of the maximal isometric plantarflexion torque of the uninjured limb. A speckle tracking algorithm was used to track proximal-distal movement of the tendon tissue at 6 antero-posterior locations. Two-way repeated measures ANOVA for peak tendon displacement was performed. K-means clustering was used to classify patients according to AT displacement patterns. The difference in peak relative displacement across locations was larger in the uninjured (1.29±0.87mm) than the injured limb (0.69±0.68mm), with a mean difference (95% CI) of 0.60mm (0.14-1.05mm, P<.001) between limbs. For the uninjured limb, cluster analysis formed 3 groups, while 2 groups were formed for the injured limb. The three distinct patterns of AT displacement during isometric plantarflexion in the uninjured limb may arise from subject-specific anatomical variations of AT sub-tendons, while the two patterns in the injured limb may reflect differential recovery after ATR with non-surgical treatment. Subject-specific tendon characteristics are a vital determinant of stress distribution across the tendon. Changes in stress distribution may lead to variation in the location and magnitude of peak displacement within the free AT. Quantifying internal tendon displacement patterns after ATR provides new insights into AT recovery.

Highlights

Achilles tendon rupture (ATR) is a disabling condition with a growing yearly incidence of 20-3 5 per 10 000 individuals.[1,2] Regardless of the treatment option, ATR leads to long-term deficits in anatomy, function and physical activity that persist several years post-ATR.[3]
Torque at 100% Maximal voluntary isometric contractions (MVCs) was significantly lower in the injured limb compared to the uninjured limb (178.47 ± 39.92 Nm), with a mean difference of 42.2 Nm (26.09-5 8.37 Nm, P < .001)
We found three distinct patterns of AT displacement during isometric plantarflexion in the uninjured limb and two in the injured limb

Summary

Introduction

Achilles tendon rupture (ATR) is a disabling condition with a growing yearly incidence of 20-3 5 per 10 000 individuals.[1,2] Regardless of the treatment option, ATR leads to long-term deficits in anatomy, function and physical activity that persist several years post-ATR.[3] The factors leading to better. . The Achilles tendon (AT) is a composite of the three sub- tendons arising from the triceps surae (TS) muscles: medial gastrocnemius, lateral gastrocnemius, and soleus. The tendon fibers twist so that at the point of insertion, lateral gastrocnemius fibers end up on the ventral side, medial gastrocnemius fibers become dorsal, and soleus fibers become medial. The twisting of the sub-tendons varies among individuals and can be classified into three types depending on the degree of torsion.[11]

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