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The Bone & Joint Journal
Vol. 100-B, Issue 12 | Pages 1600 - 1608
1 Dec 2018
The lever arm ratio of the rotator cuff to deltoid muscle explains and predicts pseudoparalysis of the shoulder
Bouaicha S Ernstbrunner L Jud L Meyer DC Snedeker JG Bachmann E
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Aims

In patients with a rotator cuff tear, tear pattern and tendon involvement are known risk factors for the development of pseudoparalysis of the shoulder. It remains unclear, however, why similar tears often have very different functional consequences. The present study hypothesizes that individual shoulder anatomy, specifically the moment arms (MAs) of the rotator cuff (RC) and the deltoid muscle, as well as their relative recruitment during shoulder abduction, plays a central role in pseudoparalysis.

Materials and Methods

Biomechanical and clinical analyses of the pseudoparalytic shoulder were conducted based on the ratio of the RC/deltoid MAs, which were used to define a novel anatomical descriptor called the Shoulder Abduction Moment (SAM) index. The SAM index is the ratio of the radii of two concentric spheres based on the centre of rotation of the joint. One sphere captures the humeral head (numerator) and the other the deltoid origin of the acromion (denominator). A computational rigid body simulation was used to establish the functional link between the SAM index and a potential predisposition for pseudoparalysis. A retrospective radiological validation study based on these measures was also undertaken using two cohorts with and without pseudoparalysis and massive RC tears.

The Bone & Joint Journal
Vol. 106-B, Issue 10 | Pages 1133 - 1140
1 Oct 2024
Glenohumeral joint kinematics during apprehension-relocation test in patients with anterior shoulder instability and glenoid bone loss
Olsen Kipp J Petersen ET Falstie-Jensen T Frost Teilmann J Zejden A Jellesen Åberg R de Raedt S Thillemann TM Stilling M
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Aims

This study aimed to quantify the shoulder kinematics during an apprehension-relocation test in patients with anterior shoulder instability (ASI) and glenoid bone loss using the radiostereometric analysis (RSA) method. Kinematics were compared with the patient’s contralateral healthy shoulder.

Methods

A total of 20 patients with ASI and > 10% glenoid bone loss and a healthy contralateral shoulder were included. RSA imaging of the patient’s shoulders was performed during a repeated apprehension-relocation test. Bone volume models were generated from CT scans, marked with anatomical coordinate systems, and aligned with the digitally reconstructed bone projections on the RSA images. The glenohumeral joint (GHJ) kinematics were evaluated in the anteroposterior and superoinferior direction of: the humeral head centre location relative to the glenoid centre; and the humeral head contact point location on the glenoid.

The Bone & Joint Journal
Vol. 100-B, Issue 3 | Pages 331 - 337
1 Mar 2018
Glenoid osteotomy for atraumatic posteroinferior shoulder instability associated with glenoid dysplasia
Inui H Nobuhara K
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Aims

We report the clinical results of glenoid osteotomy in patients with atraumatic posteroinferior instability associated with glenoid dysplasia.

Patients and Methods

The study reports results in 211 patients (249 shoulders) with atraumatic posteroinferior instability. The patients comprised 63 men and 148 women with a mean age of 20 years. The posteroinferior glenoid surface was elevated by osteotomy at the scapular neck. A body spica was applied to maintain the arm perpendicular to the glenoid for two weeks postoperatively. Clinical results were evaluated using the Rowe score and Japan Shoulder Society Shoulder Instability Score (JSS-SIS); bone union, osteoarthrosis, and articular congruity were examined on plain radiographs.

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