These authors point out that revision of a prior anatomic arthroplasty to a reverse shoulder arthroplasty is a technically challenging procedure with high complication rates. They performed a retrospective study of the intraoperative complications for convertible humeral stems and non-convertible humeral stems stratified by stem length for conversion from and anatomic to a reverse total shoulder (RSA).
279 patients were included in the study, 70 with convertible stems and 209 with non-convertible stems. 70% of convertible stems were successfully retained.
Patients with nonconvertible stems had higher intraoperative blood loss, higher overall complication rate and greater risk of intraoperative fracture.
When revising stemless implants, there was a significantly lower rate of intraoperative fracture (3.6%) but there was no difference between short stems (24%) and standard stems (23.4%).
When revising stemless implants to RSA the rate of intraoperative fracture (3.6%) was similar to that for convertible stems (2.9%).
Comment: This is an interesting study.
Humeral osteotomy was necessary for stem extraction in 17.2% of patients in the nonconvertible group and 7.1% in the convertible group. It would be of value to know what percent of the stems were cemented - cementing is a common reason for osteotomy during extraction. By contrast, humeral osteotomy is not required to remove an impaction grafted canal sparing standard stem with a low filling ratio.
With respect to the use of convertible stems, almost one third required extraction because they were not placed in optimal positions or were not at an appropriate height to allow implantation of an RSA; this is consistent with prior reports. Removal of a bulky convertible stem can carry substantial risk of fracture. One must ask, therefore, whether the substantially increased cost of a convertible implant is justified for routine use.
Obviously the most cost effective care is to prevent the need for revisions, which are so costly for the patient and for the health care system. The table below demonstrates that the major reasons for revision in this series were cuff failure, glenoid loosening, and instability.
The risk of needing revision for these reasons can be minimized by thoughtful selection of patients for anatomic arthroplasty and by excellent surgical technique.
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