Prophylaxis of C5 palsy after cervical expansive laminoplasty by bilateral partial foraminotomy

Background context It is known that postoperative motor palsy at the C5 level occurs with anterior decompression or posterior decompression and has a relatively good prognosis, but the pathogenesis and possible prophylactic measures of the palsy remain unknown. Purpose The purpose of this study was to evaluate the effectiveness of bilateral partial foraminotomy for preventing C5 palsy from occurring after cervical decompression surgery. Study design A retrospective review was performed concerning the risk factors of the C5 palsy based on the preoperative clinical findings. To investigate the prophylactic effect of the partial foraminotomy, we examined a difference of an incidence of the C5 palsy by performing concurrent partial foraminotomy with expansive laminoplasty. Patient sample A total of 305 cases of cervical expansive laminoplasty performed for spondylotic myelopathy or ossification of the posterior longitudinal ligament were reviewed. Methods We analyzed 305 cases of cervical expansive laminoplasty to investigate the preoperative risk factors that may cause postoperative C5 palsy. To clarify the relationship of the foraminotomy and development of the C5 palsy, we examined 230 patients in whom foraminotomy could be confirmed by operative records. Results Of the 305 patients, postoperative C5 palsy occurred in 13 patients (4.3%): 10 patients had radicular pain (77%), and 8 patients had sensory disturbances (62%). We assessed all neurological findings and X-ray, computed tomography and electromyographic findings, but no statistical differences were found in any of the preoperative clinical findings relative to the occurrence of postoperative C5 palsy. For the open side, 108 cases underwent foraminotomy and 122 cases did not, whereas on the hinge side, 54 cases received foraminotomy and 176 cases did not. In order to investigate the prophylactic effect of foraminotomy, we totaled the open side and hinge side, and calculated the number of bone gutters: 162 gutters had concurrent foraminotomy and 298 gutters did not. Postoperatively, C5 palsy occurred in 1 gutter (0.6%) in the former group and in 12 gutters (4.0%) in the latter group (p<.05, Fisher's direct method). Conclusions There were no specific risk factors among the preoperative clinical findings related to C5 palsy. Bilateral partial foraminotomy was effective for preventing C5 palsy.