Correlation between functional and structural variables in patients undergoing achilles tendon surgical repair

Achilles tendon (AT) rupture promotes deficits in the plantar flexors and AT's structural properties, which have been related to deficits in the ankle joint range of motion (ROM), in the plantar flexors' ability to produce force and in functionality. The objective of this study was to evaluate possible correlations between the triceps surae's structural variables with performance in functional tests, and to compare these correlations between the uninjured limb and the limb that underwent AT surgical repair. Both legs from 28 participants (37 ± 5 years) were evaluated after tendon surgical repair. Structural variables included plantar flexors' cross-sectional area (CSA), muscle thickness (MT) and echo intensity (EI) and AT's CSA. Functional variables included ankle ROM, maximal isometric plantar flexion torque (at 10° of dorsiflexion) and the single leg hop test (SLHT, single leg triple jump test). Bivariate Pearson and Spearman correlations were performed, and the partial correlation test contained the time after surgical repair as a moderating variable. There was a correlation between medial gastrocnemius CSA and SLHT (r: -0.457 and p: 0.037) in the injured limb, and between medial gastrocnemius MT and torque in the uninjured limb (r: -0.521; p: 0.011). When we added time as a moderating variable, the same correlations were significant. The results of the correlations with and without the moderating variable do not support the above-mentioned causal hypothesis between AT rupture and functional deficits.