| Objective1.The digital study of the lumbar cortical bone trajectory for the clinical application of the best screw placement.2.Screw placement validation was performed on the digital lumbar model based on the best trajectory.3.Clinically,we further validated the safety and reliability based on optimal cortical channel placement.4.The feasibility of insertion of both pedicle screw and CBT screw into the same pedicle based on digital technology.Methods1.The CT scans of lumbar spine were selected from 40 inpatients in our hospital,and lumbar vertebral deformities,fractures or infections with destructed vertebrae were excluded.The original CT DICOM data of the above 40 patients were imported into Mimics 19.0 software to load all the tomographic image information.By adjusting the layer image threshold to distinguish between bone and soft tissue,the cortical and cancellous bones are refined.Finally,the vertebral body was segmented and the cortical bone contour model was reconstructed.2.The design of the screw trajectory:Take the left pedicle pedicle as an example,and treat the pedicle as an elliptical column channel.According to the characteristics of cortical screw placement,the pedicle elliptical section were divided into four equal division quadrants.The right lower quadrant of the pedicle entrance and the outer quadrant of the exit were taken as the contact area of the screw.The entrance area is divided into area A which is only in contact with the lower wall,while area B which is in contact with the lower wall and inner wall is only in the area C which is in contact with the inner wall.The exit area is divided into an area a only in contact with the upper wall,a b area in contact with the upper wall and the outer wall,and a c area in contact with only the outer wall.Nine channels of T-Aa,T-Ab,T-Ac,T-Ba,T-Bb,T-Bc,T-Ca,T-Cb and T-Cc were designed by combining.According to the relevant parameters of the pedicle and the channel,the appropriate diameter of the nail channel was chosen to simulate nail placement,and the contact volume,channel length,head tilt angle,external declination angle,and reverse direction of each channel’s cortical bone were calculated and calculated by Mimics 19.0 software.The location of the nail.A comprehensive multi-factor analysis ultimately identified the optimal cortical bone passages in each segment of the L1～L5 vertebral body.3.The CT data of 9 previously hospitalized patients were selected(the data were not included in the above 40 patient data),including 4 males and 5 females.The lumbar spine three-dimensional model was established by using the Mimics 19.0 and Geomagic studio 12.0 software on the lumbar spine CT data of 9 patients,and the optimal cortical bone channel-based navigation template for each segment of the lumbar spine was designed.A set of lumbar pedicle screw navigation template and two identical lumbar vertebrae models were printed on each patient through a 3D printer.Three operators(orthopedic surgeons with 1 year,5 years,and 12 years of work experience,respectively)randomly selected lumbar spine models from 3 patients.Two sets of lumbar models of each patient were fitted with free hands and navigation template.After the screw is placed,the result of the 3 hands of the free hand screwing is collectively set as group A,and the results of the nail setting of the navigation template for screw placement are collectively set as group B.Through direct observation and radiographs from the AP,lateral position and cross-section to determine the placement of screws,direction,whether the pedicle cortical rupture and whether the corresponding channel requirements.According to the above statistical results,the corresponding trajectory rate was calculated,and the success rate of nail placement and acceptability of the two screw placement methods were evaluated according to Grade,and then the nail placement effect was evaluated comprehensively.4.We selected 13 hospitalized patients in our hospital,5 males and 8 females;aged 42-70 years,mean age(55.62±9.16)years.Including L4～L5 spinal stenosis in 6 patients,L4～L5 spinal stenosis with L3～L5 vertebral fracture in 1 case,lumbar spondylolisthesis in 3(1 case of L3,2 cases of L4),L4～L5 disc herniation in 3 cases.The number of fixed lumbar segments:L2×1,L3×2,L4×13,and L5×11.All patients underwent CT scans of the lumbar spine before surgery.Three-dimensional reconstructions were performed and corresponding nail placement guides were designed based on the optimal trajectory.X-ray and CT examinations were performed to observe the placement of the screws and the corresponding placement rate was calculated.Determine the accuracy of the screws based on Grade ratings.The follow-up observation of screw fixation effect.5.The lumbar spine model was established by Mimics 19.0 software on the lumbar CT data of the above 40 patients.According to the relevant parameters to select the appropriate screw,first according to the standards of the pedicle screw placement,and then placed the CBT screw avoiding the existing pedicle screw;again in the case of the lumbar spine model,while the traditional pedicle screws and cortical bone trajectory screws in the same pedicle.The success rates of the two methods were statistically analyzed.In addition,according to the TRW group statistics,the success rate of screw placement in each segment of the lumbar spine was calculated.The success rates of the two methods were statistically analyzed.In addition,according to the TRW group statistics,the success rate of screw placement in each segment of the lumbar spine was calculated.According to the statistical analysis results,the feasibility of dual-channel placement and the relationship between the success rate of nail placement and channel parameters were explored.Results1.By measuring the pedicle parameters,it was found that Mimics 19.0 and Boholo software had no significant difference in the measurement accuracy.There was no statistically significance between the traditional lumbar CT scan and the parameters measured by the pedicle scan.All operations were performed on the Mimics 19 software based on a lumbar CT scan.The safety considerations of the screw trajectory,the relationship between the screw length and the trajectory length,the contact between the screw and the channel cortical bone,and the angle at which the screw is placed are taken into consideration.Finally,we determined the optimal cortical bone trajectory of LI～L5 vertebral pedicle,L1(T-Bc):TRW(4.14mm±1.07mm),channel length(35.39mm±2.09mm),inclination angle(37.33± 3.94。),Outer deviation angle(22.16°±4.25°);L2(T-Bc):TRW(4.65mm±0.92mm),Channel length(34.15mm±2.51mm),Tilt angle(34.02°±2.74°),Outside Declination(21.62°±3.15°);L3(T-Bb):TRW(5.78mm±0.94mm),Channel Length(32.35mm±2.65mm),Tilt Angle(41.94°±3.05°),External Deflection Angle(20.69°±3.20°);L4(T-Bb):TRW(7.13mm±1.16mm),Channel Length(31.56mm±4.20mm),Tilt Angle(32.09°±2.54°),Outside Deflection Angle(19.25°±)3.75°);L5(T-Bb):TRW(6.56mm±0.97mm),Channel Length(32.94mm±4.32mm),Tilt Angle(26.49°±3.84°),Outside Deflection Angle(19.63°±4.54°).Lumbar CBT screw crossing point of medial 1/3 vertical line of upper zygapophyseal joint and lower 1/3 horizontal line of lateral spine of lamina(2-4mm medial to lower 1/3 of partial lateral spine of lamina).2.In the two groups of screws,90 cortical screws were placed,of which the placement rate of the corresponding channel of group A(unarmed nails)was 62.79%(54/86),the success rate was 70.00%(63/90),and the acceptability rate was 85.56%.(77/90);The placement rate of the corresponding channel in group B(guide plate assisted nails)was 89.53%(77/86),the success rate was 88.89%(80/90),and the acceptability rate was 97.78%(88/90);B The group-corresponding channel placement rate,nail placement success rate,and acceptability rate were all significantly higher than those in group A(a<0.05).3.All 13 patients in this group received posterior approach lumbar surgery.A total of 54 cortical bone screws,L2×2,L3×4,L4×26,and L5×22 were implanted in 13 patients.The corresponding screwing rate of L2(T-Bc)channel is 100%;the screwing rate of L3～L5(T-Bb)channel should be 88.46%.All screws were placed successfully according to the Grade standard,and the success rate of screw placement was 100%.The completion time of surgery was 1.5h～3.0h with an average of(2.1±0.75)h.Bleed volume:average(215.48± 34.52)mL in a single segment,and approximately 280 mL bleeding in a double-segment.JOA score:5～16 points before surgery,the mean(11.32±3.28)points;postoperative:19～27 points,the average(24.17± 2.09)points;the average improvement rate was(72.15± 12.85)%.VAS scores were preoperatively(5.37±1.86)points and postoperative(1.54±10.49)points.In the hands,there was no obvious lack of screw holding force,channel cleft palate,and nail placement caused nerve and spinal cord injuries.No adverse events occurred during the follow-up.4.The success rate of lumbar spine segments based on conventional pedicle screws for cortical bone screws was L1:47.50%,L2:62.50%,L3:57.50%,L4:70.00%,and L5:47.5%.At the same time,the success rate of conventional pedicle screws and cortical screws was L1:61.25%,L2:76.25%,L3:77.50%,L4:91.25%,and L5:82.50%.There was a statistically significant difference in the success rate of screw placement between the two groups(a<0.05),and the success rate of placement of double screws was significantly higher than that of pedicle screws placed in cortical bone screws again.The success rate of screw placement in each segment of the lumbar spine increases with increasing TRW.Therefore,according to the measurement results of TRW,it is important to evaluate whether the use of cortical screws for reconstructive surgery or whether double screw fixation is feasible.Conclusion1.The optimal cortical bone treajectory for L1～L5 are:T-Bc,T-Bc,T-Bb,T-Bb,and T-Bb.Lumbar CBT screw crossing point of medial 1/3 vertical line of upper zygapophyseal joint and lower 1/3 horizontal line of lateral spine of lamina(2～4mm medial to lower 1/3 of partial lateral spine of lamina).2.Based on the optimal cortical bone channel with clinical feasibility of nail placement,it is a safe,reliable and effective screw placement method.navigation template technology can improve the accuracy of screw placement to make surgery more secure.3.It is feasible to operate CBT screws and double screws at the same time based on the traditional pedicle screws;the preoperative measurement of TRW value has important guiding value for the safety and feasibility of lumbar double screw fixation;The success rate is significantly higher than the former. |
PDF Full Text Request