Scapulohumeral rhythm in patients after total shoulder arthroplasty compared to age-matched healthy individuals

Abstract

PurposeThe coordination of the glenohumeral joint and the shoulder girdle has been known as scapulohumeral rhythm. The effects of anatomical total shoulder arthroplasty (aTSA) are still subject to research. Former studies showed a higher amount of scapula lateral rotation to compensate for reduced glenohumeral elevation. The purpose of the present study was to confirm this mechanism and examine additional effects on the sternoclavicular and acromioclavicular joints’ kinematics. Methods3D motion analysis was used to examine 23 shoulders of 16 patients with a mean age of 71.2 (SD: 5.2) years with a mean follow up of 5.4 (SD: 2.1) years after aTSA and to compare kinematics and coordination to 22 shoulders of 11 healthy age-matched individuals with a mean age of 69.6 (SD: 5.3) years while performing elevation movement in frontal and sagittal plane. ResultsThe ratio of glenohumeral to shoulder girdle contribution was reduced compared to healthy individuals: Shoulder girdle contribution to elevation was 36.5% (SD: 8.1) in the aTSA group vs. 28.5% (SD: 8.2) in the control group in the sagittal plane and 38.1% (SD: 9.1) vs. 30.2% (SD: 7.1) in the frontal plane. Kinematics of the sternoclavicular and acromioclavicular joints showed significantly different patterns. ConclusionPatients after aTSA showed altered shoulder girdle kinematics and higher contribution of the shoulder girdle towards elevation. Whether this is a result of the surgery, of limited glenohumeral range of motion or due to the preoperative status remains unclear. Further investigation with a prospective study design is necessary.