Saturday, May 11, 2013

Reverse total shoulder in the setting of superior wear - cadaver study

This is a cadaver study carried out by 8 authors, seven of whom are either employed by the company making the prosthesis or receiving royalties from that company.

The authors observe that in rotator cuff tear arthropathy, the superior aspect of the glenoid may be eroded so that the glenoid surface is tilted upwards. The authors suggest that "superior glenoid wear, if left uncorrected, increases the likelihood of reverse shoulder glenoid malpositioning and can result in superior glenosphere tilt. Superior glenosphere tilt with reverse shoulder arthroplasty may increase the risk of aseptic glenoid loosening, potentially increasing the destabilizing shear forces and decreasing the stabilizing compressive forces experienced by the reverse shoulder glenoid component." 

Nevertheless, in this study, the authors created superior glenoid defects in 14 different scapulae and then used one of two strategies for a cadaver arthroplasty: (1) eccentric reaming with implantation of a standard glenoid baseplate and (2) off-axis reaming with implantation of a superior-augment glenoid baseplate. They found that both approaches resulted in good fixation of the glenoid baseplate after cyclic loading.

Comment: We can agree that a shoulder with superior glenoid wear represents a severe degree of superior instability and glenoid bone deficiency so that failure rates may be higher in this setting. It is not clear, however, that "correction" of this tilting increases the clinical survivorship of the arthroplasty (just as it is not clear that "correcting" glenoid retroversion in an anatomic arthroplasty increases clinical survivorship).

The management of bone loss in reverse shoulder arthroplasty requires the surgeon to balance the theoretical advantages of 'correcting' the tilt against accepting the tilt and preserving glenoid bone stock by minimizing reaming. Many factors go into the decision, including the design of the glenosphere (e.g. does it have some offset to avoid notching with superior tilt), the quality the initial fixation system, the quality, quantity and configuration of glenoid bone, the size of the patient, the clearance beneath the acromion, the presence of residual internal and external rotators, and the necessary activities of the patient (e.g. crutch, cane or walker use). Our inclination is to preserve as much glenoid bone as possible, use a system with excellence initial fixation, and use a glenosphere with sufficient offset to prevent leverage of the medial humeral component against the lateral scapula. 

Use the "Search" box to the right to find other topics of interest to you.

You may be interested in some of our most visited web pages including:shoulder arthritis, total shoulder, ream and runreverse total shoulderCTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'

See from which cities our patients come.

See the countries from which our readers come on this post.