Intraoperative neuromonitoring during distal femoral extension osteotomy in children with cerebral palsy

Abstract

The most common treatment method for a fixed knee flexion contracture more than 10 degrees in cerebral palsy (CP) is distal femoral extension osteotomy (DFEO). However, a serious complication after a DFEO is neurological impairment. Its rates were reported as 5- 40%. Intraoperative neuromonitoring (IONM), widely used in spinal surgery and in other fields, is a valuable tool to define any neurological injury during operation. The aim of our study was to determine surgical steps with risk of neurological injury and to report if precautions would be effective in recovering signal loss. We performed IONM during DFEO of 23 knees of 12 children with CP. IONM was performed by recording somatosensory evoked potentials, transcranial motor evoked potentials and free-run electromyography during defined steps throughout the surgery. Preoperative and postoperative popliteal angles, flexion contractures and physeal posterior distal femoral angles were evaluated. We detected alert signals at osteotomy or manipulation steps of surgeries of all patients. We observed persistent alert signals in two cases (2 out of 23 knees; Group 2). In this group, the action potentials recovered only after 5 and 10 degrees of undercorrection at the osteotomy sites. Alert signals disappeared after a brief period of waiting in other cases. Throughout mean 37 months of follow-up, none of our patients experienced any neurological complication. The study concludes that the surgical steps in DFEO with a higher risk for a neurological complication were the osteotomy and manipulation steps. Alert signals were detected with the help of IONM, and preventive measures were effective in recovering neuromonitoring recordings.