Evaluation of the effects of extremity elongation on brachial plexus nerves via intraoperative neuromonitoring in patients undergoing reverse total shoulder arthroplasty

Reverse total shoulder arthroplasty (RTSA) is one of the most common treatment method for irreparable rotator cuff tear. One of the significant complications of this surgery is nerve injury. This study aimed to identify the patterns of brachial plexus nerve involvement and to determine the surgical stages associated with increased nerve vulnerability during reverse total shoulder arthroplasty using intraoperative neuromonitoring (IONM). Additionally, the relationship between extremity lengthening, acromiohumeral distance (AHD) changes and intraoperative nerve events were evaluated. Twenty patients diagnosed with rotator cuff tear arthropathy who underwent total reverse shoulder arthroplasty in a single center were included in the study. Demographic data, preoperative shoulder range of motion (ROM), and functional scores were recorded. Radiological measurements were performed to evaluate extremity lengthening and preoperative acromiohumeral distances (AHD) differences on both shoulders. The relationship between these values and intraoperative motor-evoked potential (MEP) amplitude drops was analyzed. The nerves affected and the corresponding surgical stages were documented. Statistical analysis was performed to assess the relationship between nerve involvement and preoperative variables. Among the 20 patients evaluated, the musculocutaneous and radial nerves were most frequently affected, particularly during the glenoid preparation stage. Smoking history (p = 0.019) and increased preoperative internal rotation (p = 0.05) were significantly associated with higher risk of nerve involvement. Binomial logistic regression analysis shows that smoking history is independently associated with a higher risk of intraoperative nerve events (OR 11.49, 95% CI 1.03-128.57; p = 0.048). A preoperative difference of less than 3.7 mm in preoperative AHD between the operated and contralateral sides reduced the risk of nerve involvement by 4.2 times. The musculocutaneous and radial nerves were found to be most commonly affected, during glenoid preparation phase, due to the excessive traction and improper positioning of the retractors. Lower preoperative AHD difference of less than 3.7 mm increases the risk of nerve events. The use of IONM during RTSA surgery has a preventive effect along with its diagnostic use. 4, prospective case series.