The rehabilitation of repaired flexor tendons faces a critical dilemma: current mobilization protocols rely on rigid timelines that fail to account for inter-patient variability in healing rates. We hypothesized that the "rate of mechanical homogenization"—the restoration of stiffness equilibrium between the repair site and native tendon—could serve as an objective imaging biomarker to guide decision-making. In this prospective cohort study, 64 patients (89 tendons) undergoing flexor tendon repair were monitored using serial shear wave elastography (SWE) and color Doppler flow imaging during the first 4 postoperative weeks and 12 weeks. The "Elasticity Ratio" was derived to quantify the mechanical gradient between the healing callus and adjacent tendon stumps. The dynamic trajectories, specifically the rate of change of these biomechanical markers were analyzed to predict 12-week total active motion (TAM). Healing followed a biphasic pattern characterized by early rapid homogenization. The dynamic velocity of remodeling, rather than static stiffness values, served as the primary determinant of functional outcome. Specifically, a rapid increase in stiffness during the proliferation-to-remodeling transition (Week 2–3, r = 0.380, P < 0.001) and early callus thickening (Week 1–2, r = 0.367, P < 0.001) were strong predictors of superior TAM. This trajectory was significantly constrained by age, with older patients (≥ 46 years) exhibiting a flatter, more dispersed recovery profile. A "Traffic-Light" risk stratification model (AUC = 0.767) identified persistent hypervascularity at Week 2 without compensatory stiffness accretion as a distinct phenotype associated with poor recovery due to "mechano-biological uncoupling". Early flexor tendon healing is defined by a measurable process of mechanical homogenization. The dynamic rate of change of this stiffness gradient provides actionable physiologic feedback, enabling a shift from one-size-fits-all time-based protocols toward a personalized, biology-guided rehabilitation paradigm that identifies high-risk patients early in the postoperative window.
Xu et al. (2026) studied this question.