No Bone? No Problem! Is Bone-Grafting at the Time of Revision to a Reverse Shoulder Arthroplasty a Reasonable Option? (2015)

Commentary The treatment of a failed shoulder replacement is one of the most challenging problems facing a shoulder surgeon. Revision arthroplasty is technically complex, requiring osteotomies for implant removal, surgical dissection through abnormal tissue planes, and reconstruction of soft tissue and osseous defects. Glenoid defects are extremely common either because of erosion from failed hemiarthroplasty components or glenoid component loosening from a failed total shoulder replacement. Bone-grafting in the setting of an unconstrained arthroplasty has variable results with high rates of revision. Bone-grafting at the time of reverse total shoulder arthroplasty has the potential for improved results with lower reoperation rates. The rigid initial baseplate fixation of a reverse shoulder arthroplasty allows improved initial implant stability even in the setting of a bone graft. Relatively few authors have reported the results of bone-grafting in revision to a reverse total shoulder arthroplasty. Neyton et al. were the first, to my knowledge, to report on bone-grafting in the setting of revision to a reverse shoulder arthroplasty1. They described the cases of six patients in whom all grafts healed, although they had overall relatively modest functional results. Melis et al. reported on twenty-nine patients requiring bone-grafting during revision from anatomical shoulder arthroplasty to reverse total shoulder arthroplasty2. Complication and reoperation rates in that series were 30% and 22%, respectively. Infection (7%), instability (10%), and baseplate loosening (10%) were the common complications. The grafts were incorporated into the glenoid in 76% of the twenty-nine shoulders that had bone grafts. The average Constant score was 55 points, and the average anterior elevation was 121°. The graft source was structural iliac crest in twenty-one patients, autologous cancellous bone in five patients, and allograft in three patients. A majority of the bone deficiencies were isolated central cavitary defects. Finally, Kelly et al. also reported on revision arthroplasty in twelve shoulders requiring structural iliac crest bone-grafting in the setting of reverse shoulder arthroplasty3. They reported reasonable postoperative Constant scores (average, 65 points) and forward elevation (average, 106°), although the complication rate was 50%, with 23% requiring reoperation. The current study evaluates forty-one revisions to reverse shoulder arthroplasty with associated glenoid bone-grafting at the time of replacement. Eighty-eight percent of the patients had corticocancellous graft only and the remainder had structural grafts. Forty percent of the defects were central, and 60% were peripheral. Forty patients were followed for an average of three years postoperatively or until revision. Four different shoulder systems (five types of prostheses) were utilized, with two prostheses considered to have a lateral center of rotation and three, a medial center of rotation. Eighteen percent of the implants required revision with removal of the implants at an average of thirteen months postoperatively because of various complications (instability in 5%, infection in 2%, and glenoid loosening in 10%). Survival free of revision surgery at two years and five years was 88% and 76%, respectively, for the revisions with bone-grafting and was lower than that in the cohort that had not needed bone-grafting (94% and 93%, respectively). Final average postoperative American Shoulder and Elbow Surgeons (ASES) scores, Simple Shoulder Test (SST) scores, and abduction were 66 points, 6 points, and 112°, respectively. Preoperative moderate or severe subluxation was associated with worse postoperative ASES scores. Patients with an implant with a lateral center of rotation had worse final motion and ASES and SST scores. The rates of glenoid lucency were worse in patients with increasing body mass index (BMI), with a history of total shoulder arthroplasty, with an implant with a lateral center of rotation, and who smoked. In comparison with the previous series reported by Melis et al. and Kelly et al., the current study is similar with regard to final functional outcomes and forward elevation—that is, all had moderate levels of improvement2,3. Complication rates in the study by Melis et al. and the current study are almost identical, despite the fact that a majority of the grafts in the study by Melis et al. were structural and most in the current series were nonstructural3. Wagner et al. were able to identify certain at-risk variables in the patient population that predisposed to failure, including higher BMI, severe preoperative subluxation, revision of a total shoulder implant, and smoking. This information adds to the risk factor identified in the study by Melis et al. as a primary cause of failure—the failure to capture the central baseplate post in the native scapula. Preoperative counseling and consideration of other alternatives, including implant systems with long central screws or posts and metal augments, would be reasonable for these at-risk patients on the basis of the combined information from both studies. A majority of the grafts were corticocancellous in the current study, and reoperation rates were comparable with the data reported in Melis et al. and Kelly et al.2,3. This suggests that corticocancellous bone grafts might be an alternative to structural grafts, especially in smaller, contained central defects since structural grafts in the series by Melis et al. did not necessarily lead to better outcomes2. Nevertheless, caution should still be used for larger central defects or peripheral defects as purely corticocancellous grafting may have a limited ability to provide enough initial implant stability. Structural grafts should be considered for these larger central and peripheral defects as described in the authors’ treatment algorithm. Further research is required to determine the defects requiring structural or corticocancellous grafts only, whether allografts are comparable with autografts, and whether certain defects should be managed with metal augments alone. An implant with a lateral center of rotation was determined to have higher rates of glenoid lucency as well as worse outcomes. The authors hypothesized that this may be secondary to higher shear forces on the grafts instead of compressive forces seen with an implant with a more medialized center of rotation. The authors also recognized that the implant with a lateral center of rotation may have been utilized in patients with more severe medial glenoid wear. Finally, the current data are comparable with those in the series by Melis et al., in which an implant with a medial center of rotation was used exclusively2. Consequently, an implant with either a medial or lateral center of rotation should be considered a reasonable treatment option in these revision cases requiring bone-grafting until larger, appropriately powered studies are able to analyze the effects of each of these implants independently. There are numerous high points of the study, including follow-up of >90%, medium-term outcome information, and the largest series reported to date, as far as I know. Several questions also remain, including how a majority of defects were peripheral uncontained lesions and most of these had corticocancellous grafting only. The final position of the central screw or post is also not detailed in this series. Nevertheless, bone-grafting in the setting of glenoid defects at the time of revision to a reverse total shoulder arthroplasty is a very reasonable solution to a complicated problem. Increased awareness of risk factors associated with poorer outcomes will allow surgeons to optimize surgical techniques to reduce reoperation rates and improve overall implant longevity.