The effect of pathological shoulder rhythm on muscle and joint forces after reverse shoulder arthroplasty, a numerical analysis

• Published in: Clinical biomechanics (Bristol) Vol. 107; p. 106030
• Main Authors: Menze, Johanna, Leuthard, Louis, Wirth, Barbara, Audigé, Laurent, De Pieri, Enrico, Gerber, Kate, Ferguson, Stephen J.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.07.2023
• Subjects: Arthroplasty, Replacement, Shoulder; Biomechanical Phenomena - physiology; Humans; Muscle, Skeletal - surgery; Musculoskeletal modelling; Numerical biomechanics; Patient-specific simulations; Physical Medicine and Rehabilitation; Range of Motion, Articular - physiology; Reverse shoulder arthroplasty; Scapula - physiology; Scapula - surgery; Shoulder - physiology; Shoulder Joint; Shoulder rhythm; Patient-specific simulations; Numerical biomechanics; Musculoskeletal modelling; Shoulder rhythm; Reverse shoulder arthroplasty
• ISSN: 0268-0033; 1879-1271; 1879-1271
• DOI: 10.1016/j.clinbiomech.2023.106030

Compromised abduction ability after reverse shoulder arthroplasty is primarily linked to limited glenohumeral range of motion while scapulothoracic mobility can typically be maintained. Glenohumeral joint forces strongly depend on the resulting scapulohumeral rhythm, however, an association between the acting muscle and joint forces and the subject-specific scapulohumeral rhythm after reverse shoulder arthroplasty has not been established. Eleven reverse shoulder arthroplasty patients were divided into groups of poor and excellent abduction ability. Subject-specific models were developed and scaled for each patient using existing motion capture data in AnyBody™. Shoulder muscle and joint forces were obtained using inverse dynamics calculations during shoulder abduction to 100° in the scapula plane. The scapulohumeral rhythm, the resting abduction angle and internal body forces between the outcome groups were compared using a Mann Whitney U test. The mean glenohumeral and scapulothoracic contribution to overall shoulder abduction for the excellent group was on average 9.7% higher and 21.4% lower, respectively, compared to the mean of the poor group. For shoulder abduction angles between 30° and 60°, the excellent group demonstrated on average 25% higher muscle forces in the anterior deltoid which was significantly higher compared to the poor outcome patients. Scapulothoracic muscle activity did not differ significantly between the two functional groups. Accordingly, rehabilitation strategies focusing on strengthening the anterior part of the deltoid in particular may improve clinical outcomes. •Forces modelled for reverse arthroplasty patients with distinct shoulder rhythm.•Good mobility of reverse shoulder arthroplasty with higher anterior deltoid forces.•Poor outcome patients compensate lost mobility with scapulothoracic rotation.