Faculty Bibliography

BACKGROUND: We reviewed all revision operations performed by a single surgeon on previous hemi- and total shoulder arthroplasties from November 1987 to March 2005. METHOD: Thirty-five patients' charts were reviewed to determine the causes of failures. In addition, their outcomes after the revision surgery were analyzed. RESULTS: Overall, results were satisfactory in 71% by Neer criteria at a mean follow-up of 27.6 months. Outcomes were related to reason for failure. When failure was because of glenoid erosion, loosening, or humeral loosening, the mean improvement in forward elevation (FE) (28.9 degrees ) and external rotation (ER) (16.1 degrees ) was significantly better (P=.024 FE; P=.000 ER) than when the failure was because of infection, soft-tissue problems, or pain of undetermined origin (FE=-5.6 degrees ; ER=-6.8 degrees ).Likewise, UCLA scores in the first group were significantly better than in the second group (P=.003). In the first group, 16/18 patients were satisfied, while in the second group only 4/17 were satisfied. CONCLUSION: Our data suggest that patients whose revisions are because of glenoid erosion or component loosening can expect to have better outcomes than those whose revisions are performed for infection, instability, or other soft-tissue problems

Reverse total shoulder arthroplasty (rTSA) implants are intended to restore stability and function to shoulders with rotator cuff deficiency. The implant consists of a glenosphere projecting from a glenoid baseplate and articulating in a socket at the proximal end of a humeral component. Despite the demonstrated clinical efficacy, little information is available regarding the joint forces about this construct and the stability of the glenoid component against these forces. Our hypotheses were that the joint forces about the rTSA were comparable to that about a normal shoulder joint, and that the micromotion between the baseplate and the scapula against these loads would be sufficiently low to induce bone ingrowth. To investigate this, a custom testing rig was constructed to simulate active shoulder elevation in fresh-frozen shoulder specimens. The forces about the rTSA were calculated and found to include compressive and shear forces up to 0.7 and 0.4 BW, respectively. In contrast to a normal shoulder, where the joint forces peak at 90 degrees of abduction, forces about the rTSA were highest at about 60 degrees of abduction. These forces were then applied in cyclic loading conditions to the glenoid baseplate, and the micromotion of the implant relative to the bone was measured in the four quadrants of the component. For two different rTSA designs (DePuy Delta III(R) and Encore RSP(R)) and in the entire range of the fixation testing, the cyclical micromotions were always less than 62 microm. Thus, under loading conditions similar to physiological shoulder elevation, micromotion of the glenoid component was sufficiently low and within previously published limits to induce bone ingrowth