Research Article: Obtaining Glenoid Positioning Data from Scapular Palpable Points In Vitro

Date Published: April 4, 2013

Publisher: Hindawi Publishing Corporation

Author(s): Jordan H. Trafimow, Alexander S. Aruin.

http://doi.org/10.1155/2013/391260

Abstract

Both clinical and biomechanical problems affecting the shoulder joint suggest that investigators should study force transmission into and out from the scapula. To analyze force transmission between the humeral head and the glenoid, one must know the position of the glenoid. Studies have analyzed the position of the scapula from the positions of three palpable points, but the position of the glenoid relative to three palpable points has not been studied. Dry scapulae (N = 13) were subjected to X-rays and a critical angle, Θ (which relates the plane determined by the three palpable points on the scapula to a plane containing the glenoid center and the first two palpable points) was calculated. The mean value for Θ was 28.5 ± 5.60 degrees. The obtained Θ allows us to determine the position of the glenoid from three palpable points. This information could be used in calculation of forces across the shoulder joint, which in turn would allow optimizing the choice of strengthening exercises.

Partial Text

Both clinical and biomechanical problems affecting the shoulder joint suggest that investigators should study force transmission into and out from the scapula [1]. One clinical problem is the wearing away of the posterior part of the glenoid in patients who need total shoulder replacement [2]. Another problem is dyskinesis, (e.g., abnormal scapular motion) due to various clinical entities such as internal derangement of the shoulder, acromioclavicular instability, and fractured clavicle [1, 3]. In addition, movements of the scapula are subjected to extensive variations, which in itself influence the interaction of glenoid and humeral head [4]. Some authors postulate that dyskinesis causes swimmer’s shoulder and impingement syndrome [5, 6].

Means measured for each specimen, OP and PS lengths, and Θ are shown in Table 1. The obtained Θ for the group was 28.74 ± 5.60°.

Knowing the position of glenoid is essential in analyzing force transmission from the humerus to the glenoid. However, to date we could find no study which determines the position of the glenoid from palpable points on the scapula. To obtain the glenoid position one must start with points on the scapula that are palpable. However, what we need is the position of the glenoid. Obtaining Θ would allow us to determine this position.

The study outcome allows obtaining the position of the center line and as such the position of the glenoid from the positions of three palpable points on the scapula. This information could be used in calculation of forces across the shoulder joint, which in turn would allow optimizing the choice of strengthening exercises in patients with dyskinesis.

 

Source:

http://doi.org/10.1155/2013/391260

 

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