Sound Pressure Signal Analysis During Milling Process In Anterior Cervical Spine Surgery In Vitro

Objective The objective of this study is to collect the sound pressure signals generated in the process of milling with various kinds of tissues and discriminate its difference among the tissues of annular fibrosus,end plate cortical bone,vertebral cancellous bone and posterior longitudinal ligament in bovine cervical spine in vitro.Methods A total of 8 bovine lumbar spines(9 weeks)were used in this experiment.C3 to C7 were all included.All specimen sections include all parts of C3 to C7.Specimens were excluded if fractures,traumatic pathology,bridging osteophytes,or hypertrophy,calcification or ossification of ligament,because these conditions can significantly affect the biomechanics of the cervical spine.In each sample randomly used one of the segments,and chose complete annular fibrosus,endplate cortical bone,cancellous bone of the vertebral body and the posterior longitudinal ligament as experimental object.They were grouped into 4 groups by different tissues.The experimental specimens were frozen and thawed at room temperature before the experiment.Bovine cervical simple were surgical treatment,made complete exposure of the test tissues.Installed and tested sound pressure signal devices,and the spindle speed of the motor is set as 60,000 RPM.The sampling frequency of the sound signal FS is fixed at 50,000 Hz.Milled the 4 tissues separately.The sound pressure signal generated during the milling process is collected by the experimental microphone and transmitted to the dynamic signal acquisition module.Using MATLAB 8.4 software and wavelet packet transform(WPT)software package for wavelet packet transform of sampling signal,gain wavelet packet coefficient tree structure and select the function,using the best wavelet packet basis selection algorithm to select the best medium.The wavelet packet coefficients corresponding to the best orthogonal wavelet packet basis were processed.The wavelet packet reconstruction algorithm is used to reconstruct the wavelet packet coefficients.The sound pressure spectrum of four kinds of tissues were obtained.SPSS 22.0 for windows software was used to analyze the data of the sound pressure signal,and the multi-group independent sample rank sum test(Kruskal-Wallis Test)was performed for the sample mean at the same frequency.Results 1.Sound pressure signal spectrum shows that the state of each milling process at different frequencies have different magnitude,and there is a remarkable difference between each other.Of which the most obvious are at of 1000 Hz,2000Hz,3000 Hz,4000Hz and 5000 Hz.The overall difference between sound pressure signal of annular fibrosus,endplate cortical bone,vertebral cancellous bone and posterior longitudinal ligament was statistically significant(P < 0.05).2.Sound pressure signal data between annular fibrosus and endplate cortical bone in 1000 Hz,2000Hz,3000 Hz and 5000 Hz have statistical significance(P < 0.05),there was no significant difference in the frequency of 4000Hz(P > 0.05).The data between annular fibrosus and posterior longitudinal ligament in 2000 Hz,3000Hz,4000 Hz and 5000 Hz have statistical significance(P < 0.05),there was no significant difference in the frequency of 1000Hz(P > 0.05).The data between endplate cortical bone and vertebral cancellous bone in 1000 Hz,2000Hz,3000 Hz and 4000 Hz have statistical significance(P < 0.05),no significant difference in the frequency of 5000Hz(P > 0.05).Conclusion 1.The sound pressure signal of annular fibrosus,endplate cortical bone,vertebral cancellous bone and posterior longitudinal ligament from milling process are remarkably different.2.It is hopeful that the sound pressure signal from milling process could be one of the candidates for the application of feedback control in ACDF surgery.