While some surgeons advocate structural bone grafting for glenoid bone loss in reverse total shoulder arthroplasty (RSA) these authors have observed different complication rates in 44 patients (61% females and 39% males, with an average age 74) who underwent RSA with structural bone grafting for glenoid bone defects.
The time to median final radiographic follow-up was 20 months, with 37 primary RSAs and 7 revision.
Graft resorption was found in 11 of 44 patients (25%), and radiographic failure was found in 11 of 44 patients (25%) at a median of 8 months (range 3-51 months).
Radiographic baseplate failure was associated with graft resorption (P .002) and more retroversion correction (P .02).
Radiographic baseplate failure was associated with graft resorption (P .002) and more retroversion correction (P .02).
The authors provide some instructive case examples, first of a graft that healed without baseplate failure.
And three examples of graft absorption with baseplate failure
Comment: In this context, stability of the baseplate depends on good surgical carpentry and secure compression of the graft into the host bone. This is especially the case if the graft lateralizes the baseplate so that it is subject to a greater loosening lever arm with upward loads applied by the humeral component.
Stability needs to be achieved well before bone healing has occurred in that upward directed loads will be applied to the glenosphere from day one after surgery - note that all four of these failures occurred with upwards displacement of the glenosphere from loads applied to the glenosphere through the humerus by the deltoid, by using a walker, by pushing down on the bed to get up, from a fall, etc.
Fixation of the graft using only the baseplate screws may be insufficient, as these cases show. With the central screw type baseplate (upper two cases), tightening the screw may twist the graft from its ideal position on the host bone and prevent adequate compression. With peg type baseplate (lower two cases) the small non-collinear screws may be insufficient for adequate compression of the graft into host bone. As these authors point out, many baseplate failures occur within the first year of surgery.
As emphasized in this article, Factors affecting fixation of the glenoid component of a reverse total shoulder prothesis, stability of the glenosphere against upward directed loads depends on excellent fixation with the inferior baseplate screws coupled with secure seating of the superior aspect of the baseplate on solid bone.
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