Computational and experimental frameworks for shoulder biomechanics: application to arthroscopic superior capsule reconstruction

Madalena João da Cruz Antunes

Key information

Authors:

Madalena João da Cruz Antunes (Madalena João da Cruz Antunes)

Supervisors:

Carlos Miguel Fernandes Quental (Carlos Quental); João Orlando Marques Gameiro Folgado (João Orlando Marques Gameiro Folgado); Clara Isabel de Campos Azevedo

Published in

June 5, 2026

Abstract

Arthroscopic superior capsule reconstruction (ASCR) was introduced for young patients with irreparable rotator cuff tears (RCTs). In ASCR, a graft is used to restore glenohumeral (GH) stability and recover physiological kinematics. However, variability in graft tear rates and inconsistent clinical outcomes have limited its adoption, highlighting the need for biomechanical evidence to guide clinical decision-making. This study developed comprehensive computational and experimental frameworks for studying shoulder biomechanics, with ASCR serving as a key application. Complementing this, the work introduced a novel rotational driving-constraint formulation and an innovative clamping interface for tensile testing, supporting the evaluation of ASCR-related factors and broader research on GH mechanics and soft-tissue behaviour. A musculoskeletal model was adapted to simulate the ASCR procedure, including the graft geometry and material properties. Using this model, the influence of three factors – shoulder position of graft fixation, the concomitant tenotomy of the long head of the biceps tendon (LHBT), and four patterns of irreparable RCTs – on shoulder stability and graft tear were evaluated. The results highlighted the role of the graft in restoring shoulder stability. The shoulder position of fixation influenced GH stability and the degree to which the intact condition was restored. The concomitant tenotomy of the LHBT significantly reduced GH stability; however, potential improvements in shoulder pain were not accounted for. For RCTs extending beyond the supraspinatus, the graft was not able to significantly improve stability in a set of multiplanar motion. In multibody modelling, the formulation of rotational driving constraints may introduce numerical instabilities and redundancy in the system, compromising the robustness of kinematic and dynamic analyses. To address this, a novel formulation was proposed, eliminating redundancy and improving numerical stability while showing good agreement with literature data. Finally, a clamping interface was designed and 3D-printed to improve the tensile testing of biological specimens, enhancing grip adherence and maximum force, and promoting failure within the gauge section.