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Figure. Anteroposterior radiograph of the left shoulder.
A 68-year-old man presents to the office with chronic pain in his left shoulder. He believes that the pain originated more than 10 years ago, and he has progressively lost motion and strength in his shoulder since. Physical examination of the left shoulder reveals 90° of active forward flexion and significant weakness with forward flexion in the scapular plane. Anteroposterior radiograph of the shoulder (Figure) is obtained.
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The patient’s shoulder pain can be attributed to end-stage shoulder arthritis consistent with rotator cuff arthropathy. Stability of the glenohumeral joint largely depends on the ability of the rotator cuff to keep the humeral head centered in the glenoid cavity.1,2
The rotator cuff exerts an inferior pull on the humeral head that is balanced by a superior pull of the deltoid muscle. When the rotator cuff tears and fails to maintain this inferior pull, the humeral head begins migrating superiorly. This migration can be seen as a decreased acromiohumeral interval on imaging. As the humeral head migrates superiorly, the contact forces at the glenohumeral joint are altered, resulting in progressive cartilage degeneration.1,2
Reverse total shoulder arthroplasty is the optimal treatment for shoulder pain associated with rotator cuff arthropathy. Standard total shoulder arthroplasty requires an intact rotator cuff for the implants to function appropriately. Without a rotator cuff, the humeral head prosthesis would migrate superiorly and fail. A reverse prosthesis reverses the anatomy of the shoulder joint by placing a “ball” on the glenoid side and a “socket” on the humeral side. This arrangement moves the center of rotation distally and medially, which improves the ability of the deltoid muscle to forward flex the humerus. This arrangement also improves stability and range of motion in the shoulder.1,2
Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor in chief of the Journal of Orthopedics for Physician Assistants.
References
1. Wall B, Nové-Josserand L, O’Connor DP, Edwards TB, Walch G. Reverse total shoulder arthroplasty: a review of results according to etiology. J Bone Joint Surg Am. 2007;89(7):1476-1485.
2. Guery J, Favard L, Sirveaux F, Oudet D, Mole D, Walch G. Reverse total shoulder arthroplasty: survivorship analysis of eighty replacements followed for five to ten years. J Bone Joint Surg Am. 2006;88(8):1742-1747.
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