Incidence of Peripheral Nerve Injury in Revision Total Shoulder Arthroplasty: An Intraoperative Nerve Monitoring Study

Introduction: The incidence of nerve injuries in revision total shoulder arthroplasty (TSA) is not well defined in the literature and may be higher than primary procedures with one study reporting a complication rate of 50% for shoulder revisions. Given that continuous intraoperative nerve monitoring (IONM) can be an effective tool in diagnosing evolving neurologic dysfunction and preventing postoperative injuries, the purpose of this present study is to report on IONM data and nerve injury rates of a series of revision TSA.

Methods: A retrospective cohort review of consecutive patients who underwent revision TSA was performed from January 2016-March 2020. Indications for revision included infection (N=7), failed total and hemi-arthroplasty secondary to pain, dysfunction and/or loose components (N=36), and a periprosthetic fracture (N=1). Thirty-two patients were revised to a rTSA, six to an aTSA and six had a spacer placed. IONM data included transcranial electrical motor evoked potentials (MEPs), somatosensory evoked potentials (SSEPs), and free-run electromyography (EMG). Motor alert threshold was set at ≥ 80% signal attenuation in any one or more peripheral nerves. Patients were screened for neurological deficits immediately following surgery, prior to administration of interscalene nerve block, and in the first two postoperative visits. Additional data collection included surgical indication, gender, laterality, age at surgery, procedure performed, body mass index (BMI), history of tobacco use, Charlson comorbidity index (CCI), past medical history and preoperative range of motion (ROM).

Results: A total of 44 shoulders in 38 patients were included with a mean age of 63.2 years (standard deviation, 13.0). 22.4% of procedures (n=10) had a MEP alert with eight isolated to a single nerve (seven axillary, one radial) and one isolated to the axillary and musculocutaneous nerves. Only one patient experienced a major brachial plexus alert involving axillary, musculocutaneous, radial, ulnar, and median nerve MEP alerts as well as ulnar and median nerve SSEP alerts. Age, gender, BMI, CCI, and preoperative ROM were not found to be significantly different between cases in which a MEP occurred compared to those with no MEP. There were zero minor or major nerve injuries found in the postoperative period, while four (9.1%) developed distal peripheral neuropathy (DPN).

Conclusion: In 44 surgeries, no (0%) patients had a postoperative major or minor nerve injury, and four (9.1%) patients complained of postoperative DPN. In this study, we show that through the use of IONM, the rate of minor and major nerve injuries can be minimized in revision shoulder arthroplasty.

Level of evidence: Level III; Retrospective Case-Control Design; Prognosis Study.

Keywords: Complications; Intraoperative Nerve Monitoring; Nerve Injury; Neuromonitoring; Revision; Shoulder Arthroplasty.