Impact of Accumulating Risk Factors on the Incidence of Dislocation After Primary Reverse Total Shoulder Arthroplasty Using a Medial Glenoid Lateral Humerus Onlay Prosthesis

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Journal of shoulder and elbow surgery / American Shoulder and Elbow Surgeons ... [et al.]


INTRODUCTION: The aim of this study is to facilitate preoperative identification of patients at-risk for dislocation after reverse total shoulder arthroplasty (rTSA) using the Equinoxe rTSA prosthesis (medialized glenoid, lateralized onlay humerus with a 145° neck angle) and quantify the impact of accumulating risk factors on the occurrence of dislocation.

METHODS: We retrospectively analyzed 10,023 primary rTSA patients from an international multi-center database of a single platform shoulder prosthesis and quantified the dislocation rate associated with multiple combinations of previously identified risk factors. To adapt our statistical results for prospective identification of patients most at-risk for dislocation, we stratified our dataset by multiple risk factor combinations and calculated the odds ratio for each cohort to quantify the impact of accumulating risk factors on dislocation.

RESULTS: 136 (52F/83M/1UNK) of 10,023 primary rTSA patients were reported to have a dislocation for a rate of 1.4%. Patients with zero risk factors were rare, where only 12.7% of patients (1,268 of 10,023) had no risk factors, and only 0.5% of these (6 of 1,268) had a report of dislocation. The dislocation rate increased in patient cohorts with an increasing number of risk factors. Specifically, the dislocation rate increased from 0.9% for a patient cohort with 1 risk factor to 1.0% for 2 risk factors, 1.6% for 3 risk factors, 2.7% for 4 risk factors, 5.3% for 5 risk factors, and 7.3% for 6 risk factors. Stratifying dislocation rate by multiple risk factor combinations identified numerous cohorts with either an elevated risk or a diminished risk for dislocation.

DISCUSSION: This 10,023 rTSA multi-center study demonstrated that 1.4% of rTSA patients experienced dislocation with one specific medialized glenoid/lateralized humerus onlay rTSA prosthesis. Stratifying patients by multiple combinations of risk factors demonstrated the impact of accumulating risk factors on incidence of dislocation. rTSA patients with the greatest risk of dislocation were: male gender, age ≤67 years at the time of surgery, patients with BMI ≥31, patients who received cemented humeral stems, patients who received glenospheres having a diameter >40mm, and/or patients who received expanded/laterally offset glenospheres. Patients with these risk factors who are considering rTSA using a medial glenoid/lateral humerus, should be made aware of their elevated dislocation risk profile.

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ePub ahead of print