Predicting C5 palsy via the use of preoperative anatomic measurements

Background contextC5 nerve root palsy (C5P) is a relatively rare complication after anterior and posterior cervical decompression surgery that leads to a variety of debilitating symptoms. The precise etiology remains obscure, and a clear understanding of preoperative risk factors for C5P development does not exist.PurposeTo determine whether postoperative C5P can be predicted from preoperative anteroposterior diameter (APD), foraminal diameter (FD), and/or cord-lamina angle (CLA).Study designRetrospective review.Patient sampleConsecutive patients who underwent either anterior or posterior decompression surgery at C4–C5 for cervical spondylotic myelopathy.Outcome measuresDevelopment of C5P.MethodsBlinded reviewers retrospectively assessed magnetic resonance images for each included patient's C4–C5 interspace, including the midline APD, the left and right FDs, and the left and right CLA. Multivariable logistic regression was used to model the probability of palsy on the basis of one or more predictors. A jackknife validation was performed to internally validate the model and assess its generalizability.ResultsA total of 98 patients fit the inclusion criteria; 12% had developed symptoms of C5 palsy postoperatively. Using the three variables in a predictor-model, we found that the odds ratio of having palsy for APD, FD, and CLA was 0.3, 0.02, and 1.4, respectively. For every 1-mm increase in APD and FD, the odds of developing palsy decrease 69% (p<.0001) and decrease 98% (p<.0003), respectively. In contrast, for every 1-degree increase in CLA, the odds of developing palsy increase by 43% (p<.0001). The receiver-operating characteristic curve for this three-variable model predicting development of palsy has an area under the curve (concordance index) of 0.97. After implementing a jackknife validation, the area under the curve was 95%.ConclusionsThis study is the first to use the combination of APD, FD, and CLA to predict development of postoperative C5 palsy after decompression surgery for patients with spondylotic myelopathy. This prediction formula may allow for better patient selection and to prepare patients that have an increased probability of developing this complication.