An exploratory study of relationships among morphological and mechanical properties of the patellar tendon and patient‐reported outcomes after ACLR using BPTB autograft

Abstract Purpose Patellar tendon structural and mechanical properties undergo significant remodelling after anterior cruciate ligament (ACL) reconstruction (ACLR) using a bone–patellar tendon–bone (BPTB) autograft. Tendon properties have been described at different time points after surgery, but their relationship to patient‐reported outcome measures (PROMs) is unclear. The purpose of this investigation was to assess how patellar tendon structure relates to PROMs after ACLR using BPTB autograft. Methods Thirty‐four individuals with unilateral ACLR using a BPTB autograft participated in this secondary exploratory analysis. At time points 1, 3–4, and 6–9 months after surgery, PROMs were completed and tendon properties (cross‐sectional area CSA, thickness, shear modulus, and viscosity) were assessed using B‐mode ultrasound imaging and continuous shear wave elastography. Simple linear regressions evaluated the relationship between Limb Symmetry Index of tendon properties (LSI, involved ÷ uninvolved × 100) at each time point and PROM scores at the 6–9‐month time point. Multiple regressions assessed associations between involved limb tendon properties at all three time points and PROMs at 6–9 months, adjusting for age, sex, body mass index (BMI), and time from surgery. R 2 values for simple linear regressions and R 2 change values for multiple regressions were interpreted with an alpha level of 0.05. Results Shear modulus LSI at 1 month was negatively correlated with Anterior Cruciate Ligament–Return to Sport after Injury (ACL‐RSI) scores at 6–9 months ( p = 0.022, R 2 = 0.225, = −0.20). Viscosity LSI at the 3–4 month time point was positively correlated with Tampa Scale of Kinesiophobia (11‐item) (TSK‐11) scores at 6–9 months ( p = 0.016, R 2 = 0.197, = 0.06). Thickness LSI at 6–9 months was positively correlated with Knee Outcome Survey–Activities of Daily Living Scale (KOS‐ADLS) scores at 6–9 months ( p = 0.031, R 2 = 0.156, = 0.03). When involved limb patellar tendon properties and covariates were considered, no significant relationships with PROM scores were observed ( p = 0.120–0.960). Conclusion Limb symmetry in tendon properties, but not involved limb properties alone, was associated with PROMs 6–9 months after ACLR using BPTB autograft. This suggests that limb symmetry of tendon properties may relate to self‐reported recovery. Level of Evidence Level II.