The need for neuromonitoring during growing rod surgical distractions

Abstract

Purpose: Intraoperative neurophysiological monitoring (IONM) is common practice during spine surgery and has been proven to be an accurate and reliable method for early detection of injury to neural structures. Drawbacks, however, include additional set-up time, financial cost, and particular anesthetic considerations. Although critical in high-risk procedures, the necessity of IONM in lower risk procedures, such as growing rod (GR) lengthenings, has not been extensively investigated. The aim of this study is to investigate the role of IONM during GR lengthening surgery. We hypothesize that it is reasonable to perform pediatric lengthening surgery in the absence of IONM.

Methods: Early onset scoliosis patients treated with GR between 2003 to 2023 who had routine IONM were retrospectively reviewed. Surgeries were categorized into implant placements, lengthenings, hardware exchanges and fusions. Descriptive statistics summarized baseline patient characteristics and surgical details. Neuromonitoring data for all procedures and any record of post-operative neurologic deficit were reviewed. Diagnostic sensitivity and specificity were calculated.

Results: For the 62 patients included (mean age 6.62y, 54.8% female), 470 procedures were reviewed, of which 450 had neuromonitoring. Average initial and post-treatment Cobb angle were 83.5 ± 16.6 and 61.1 ± 20.4 degrees, respectively. Fourteen patients were still undergoing treatment. Procedures included 67 implant placements, 326 lengthenings, 55 fusions and 2 hardware exchanges. There were 32 alerts in 25 procedures: 18 implant placements (26.9%), 3 lengthenings (0.92%), and 11 fusions (20%). Of the 3 alerts that occurred during lengthening procedures, 2 were the result of surgical position, and 1 was related to traction to the ipsilateral brachial plexus post-distraction. Two occurred in the same patient, who had previously had a positional alert during implant placement. There were no neurological deficits. IONM specificity was as follows: total 93.0%, implants 74.6%, lengthenings 99.1% and fusions 81.0%. Sensitivity was 100% for all procedures.

Conclusion: Neuromonitoring alerts were most common during implant placements and fusion surgeries and occurred during less than 1% of lengthenings. Given the rare occurrence of IONM alerts during distractions, and the absence of neurological injury following these cases, we propose that IONM is not necessary for routine lengthening procedures. IONM is not always indicated and should be considered on a case-by-case basis. However, neuromonitoring remains prudent in cases with pre-existing neurological deficits, prior alerts, or when postoperative assessment is limited, as these factors may increase the risk of neural compromise.

Keywords: Distraction osteogenesis; Internal fixation device; Intraoperative neurophysiological monitoring; Scoliosis; Spine.