Predictive value of dynamic F-wave In surgical treatment of Hirayama disease / 中华骨科杂志

ABSTRACT

Objective　To investigate the predictive value of dynamic F wave in the treatment of Hirayama disease(HD)after anterior cervical fusion and internal fixation.Methods　From February 2014 to January 2016,thirty-six patients with HD were included in this study(age17.9±2.6 years,height173.1±6.2 cm,disease duration20.1±13.1 months;male to female ratio351),and all of these 36 patients underwent anterior cervical autogenous iliac fusion and internal fixation.All of these patients underwent bilateral dynamic F-wave detection(The F-wave was tested on the cervical standard position and at least 30 minutes after cervical flexion)on the median nerve before operation and 3-5 days after operation.The latency and maximum amplitude of M-wave,the persistence of F-wave,the shortest latency of F-wave,the ratio of F/M and the persistence of repeated F-wave were measured.Dynamic F-wave abnormalities were defined when repeated F-wave was only found during neck flexion or the standard-flexion difference of each measurements of F-wave was more than 2 standard deviations from the normal value(the shortest latency of F-wave0.6±0.5 ms,persistence of F-wave7.3%±5.7%,the ratio of F/M1.1±1.0).Furthermore,these patients with HD accepted both bilateral grip strength and hand function score(disabilities of arm,shoulder and hand,DASH)before and 1 year after operation.According to the presence of abnormal dynamic F-wave before operation,patients were divided into abnormal dynamic F-wave group and normal dynamic F-wave group.Fisher exact test was used to compare the percentage of the patient with improved DASH score in both patient groups after operation.Both DASH score and bilateral grip strength were analyzed by paired sample t test before and after operation.Results　Before operation,eleven(11/36,30.6%)patients with HD had abnormal dynamic F-wave,and there was no significant difference of age(t=-0.849,P=0.412),duration(t=1.110,P=0.282),DASH scores(t=2.002,P=0.055)and handgrips(more-symptomatic sidet=-0.673,P=0.507;symptomatic sidet=-1.729,P=0.094)between the patients with or without preoperative dynamic F-wave abnormalities.One-year follow-up demonstrated that significantly greater number of the patients presented with reduced DASH scores in the patients with preoperative dynamic F-wave abnormalities(10/11,90.9% vs 12/25,48.0%;P=0.025).Compared with the patients without preoperative dynamic F-wave abnormalities,the patients with preoperative dynamic F-wave abnormalities showed reduced DASH scores after operation(t=2.347,P=0.041).Furthermore,abnormal dynamic F-waves disappeared soon after operation in ten patients(90.9%,10/11)with preoperative dynamic F-wave abnormalities,and DASH scores reduced significantly in these ten patients after operation(4.4±3.8 vs 1.5±0.4,t=3.094,P=0.013),and the DASH score in another patient whose dynamic F wave did not disappear after operation increased significantly one year after operation(preoperative vs.postoperative6.66 vs 9.87).Conclusion　Dynamic F-wave can be used as a preoperative evaluation method for HD to predict the recovery of upper limb function after operation.At the same time,the comparison of dynamic F-wave before and after operation is an effective and immediate method to evaluate the effectiveness of surgical treatment of HD.