Role of pre-existing pathological changes in postoperative function and tendon elasticity after Achilles tendon rupture repair : a retrospective cohort study.

Abstract

Achilles tendon rupture is usually caused by mechanical forces and internal pathological changes, but the association of these changes with postoperative outcomes has not been well established. This study aims to explore the relationship between different pathological types of Achilles tendon rupture and postoperative function, tendon elasticity, and structural thickening. This retrospective cohort study included patients who underwent Achilles tendon rupture surgery from May 2017 to May 2021. Pathological types were classified using haematoxylin and eosin staining as normal, mucoid degeneration, degeneration, fatty infiltration, or calcification. The outcomes, including functional scale, tendon elasticity, and thickening, were compared between the pathological types and normal tendons. Univariate and multivariable linear regression, along with mixed-effects models, were used to analyze the association between pathological types and postoperative outcomes. Among 165 patients, 46 (27.8%) were normal, 21 (12.7%) had mucoid degeneration, 22 (13.3%) had fatty infiltration, 36 (21.8%) had calcification, and 40 (24.2%) had degeneration. Functional outcomes showed no significant differences in trends over the follow-up time in different tendon pathology types compared to the normal group. At one year, the mucoid group showed 0.14 m/s elongated tendon elasticity in plantarflexion (95% CI -0.24 to -0.04; p = 0.006) and 0.94 m/s decreased dorsiflexion (95% CI -1.59 to -0.04; p = 0.007), with similar results at two years (95% CI -1.11 to -0.21; p = 0.006). Fatty infiltration showed 0.14 m/s elongated dorsiflexion elasticity ( 95% CI -1.09 to -0.19, p = 0.006). The calcified group had 0.68 mm decreased diameter at two years (95% CI -1.20 to -0.26; p = 0.002). Mucoid degeneration and fatty infiltration are linked to alterations in tendon elasticity. Calcification is associated with a reduction in tendon diameter over time. The pathological features may not substantially impact long-term functional recovery.