Biomechanics of anatomic and reverse shoulder arthroplasty.

The biomechanics of the shoulder relies on careful balancing between stability and mobility. A thorough understanding of normal and degenerative shoulder anatomy is necessary, as the goal of anatomic total shoulder arthroplasty is to reproduce premorbid shoulder kinematics.With reported joint reaction forces up to 2.4 times bodyweight, failure to restore anatomy and therefore provide a stable fulcrum will result in early implant failure secondary to glenoid loosening.The high variability of proximal humeral anatomy can be addressed with modular stems or stemless humeral components. The development of three-dimensional planning has led to a better understanding of the complex nature of glenoid bone deformity in eccentric osteoarthritis.The treatment of cuff tear arthropathy patients was revolutionized by the arrival of Grammont's reverse shoulder arthroplasty. The initial design medialized the centre of rotation and distalized the humerus, allowing up to a 42% increase in the deltoid moment arm.More modern reverse designs have maintained the element of restored stability but sought a more anatomic postoperative position to minimize complications and maximize rotational range of motion. Cite this article: EFORT Open Rev 2021;6:918-931. DOI: 10.1302/2058-5241.6.210014.

Hydrodilatation with corticosteroids is the most effective conservative management for frozen shoulder.

PURPOSE: The purpose of this overview is to summarise the findings of meta-analyses of randomised controlled trials that compare conservative treatment options for frozen shoulder. METHODS: The authors conducted an electronic literature search for meta-analyses published using PubMed, Web of Science and the Cochrane Library. Two researchers independently applied selection criteria and assessed quality of meta-analyses using A MeaSurement Tool to Assess systematic Reviews (AMSTAR-2). Short-, medium- and long-term outcomes were synthesised narratively. RESULTS: A total of 319 studies were identified, of which 8 meta-analyses were eligible for inclusion. All included meta-analyses were judged to be low or critically low quality according to AMSTAR-2, however, their data synthesis and interpretation was considered valid. Physiotherapy, intra-articular and subacromial corticosteroid injection (CSI), and arthrographic distension/hydrodilatation with corticosteroid were reported with sufficient evidence. Intra-articular CSI and arthrographic distension/hydrodilatation with corticosteroid provide advantages over placebo in short-term pain relief, range of motion (ROM) and shoulder function, with improvements in ROM continuing into the medium and long term. Arthrographic distension/hydrodilatation with corticosteroid provides medium-term and long-term improvements in ROM over intra-articular CSI and physiotherapy. Proprioceptive neuromuscular facilitation provides advantages over conventional physiotherapy for pain improvement and external rotation in the short term. CONCLUSIONS: Arthrographic distension/hydrodilatation with corticosteroid provides superior pain relief in the short term and improvement in range of motion across all time frames for frozen shoulder when compared to CSI or physiotherapy. LEVEL OF EVIDENCE: Level IV.

Scapulothoracic Alignment Alterations in Patients with Walch Type B Osteoarthritis: An In Vivo Dynamic Analysis and Prospective Comparative Study.

BACKGROUND: Kinematic changes of the scapulothoracic joint may influence the relative position of the glenoid fossa and, consequently, the glenohumeral joint. As the alignment of the scapula relative to the thorax differs between individuals, such variability may be another factor in the development of posterior head subluxation. The purpose of this study was to compare scapulothoracic alignment in pathologic type B shoulders with contralateral healthy shoulders. METHODS: Seven adult volunteers with unilateral type B glenohumeral osteoarthritis (OA) underwent bilateral computed tomography (CT) scans of the shoulders and arms. A patient-specific, three-dimensional measurement technique that coupled medical imaging (i.e., CT) and optical motion capture was used. RESULTS: The scapulothoracic distance at the trigonum was 75 ± 15 mm for pathologic shoulders and 78 ± 11 mm for healthy shoulders (p = 0.583), while at the inferior angle, it was 102 ± 18 mm for pathologic shoulders and 108 ± 12 mm for healthy shoulders (p = 0.466). CONCLUSION: Scapula positioning at a resting position did not differ between pathologic and healthy shoulders. However, pathologic shoulders tended to be limited in maximal glenohumeral motion and exhibited greater anterior tilt of the scapula in internal rotation at 90 degrees, which may be adaptive to the restricted glenohumeral motion.