Saturday, December 22, 2012

Glenoid reimplantation

Aseptic glenoid loosening or failure in total shoulder arthroplasty: revision with glenoid reimplantation

Glenoid component failure is a critical concern in total shoulder arthroplasty.  The major factors associated with glenoid component failure are reviewed here. This article is humbling because it represents the best efforts of highly qualified surgeons to revise cases of glenoid component failure - the most common serious complication of total shoulder arthroplasty.

The authors present a retrospective multicenter study of 42 total shoulders with symptomatic failed glenoids. 32 of the glenoids were metal backed and 10 were cemented polyethylene. The main cause of glenoid failure was component loosening in 19 cases (46%) and PE wear or dissociation in 23 (54%).

These failures were revised by reimplantation of an all–polyethylene cemented glenoid component. In this series complications were very frequent, including rotator cuff tears, subscapularis insufficiency, and prosthesis instability. At last follow-up, 7 patients (17%) had already been re-revised because of symptomatic recurrent glenoid loosening. The overall rate of recurrent glenoid loosening (re-revision
plus radiologic loosening) was 67%. Soft-tissue problems and prosthetic instability were significantly associated with recurrent loosening. Of the 10 associated bone grafts performed during the revision procedure, all were partially or totally lysed.

"Aseptic loosening" is term used to refer to loosening without positive cultures - it does not mean that bacteria were not associated with the loosening (only that their presence was not discovered). The most common organism in failed total shoulders is Propionibacterium and special means are necessary to avoid false negative cultures. Failure to manage deep infections may result in failure of replanted components. The authors report that "several intraperative samples of bone and tissue were obtained for
a systematic bacteriologic analysis." but the culture protocol were not detailed and results not presented.

Bone grafting is often discussed as a solution to managing glenoid bone defects, but we have not seen good results reported with this approach. 

Filling the defect from a prior arthroplasty with cement exposes the glenoid to high levels of heat from the curing PMMA. In this figure from the article, "A" shows the index arthroplasty with a substantial cement volume. The revision in "B" used even more cement with subsequent failure.

Our approach to the failed glenoid component is to obtain cultures for Propionibacterium and hold them for at least 3 weeks, perform vigorous washout, continue antibiotics until culture results are finalized, remove the glenoid component and smooth the residual bone without grafting and implant a large diameter head prosthesis.


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