Feasibility of using cortical bone trajectory screws in osteoporotic thoracolumbar fixation based on evaluation of bone CT values at bone-screw interface / 中华创伤骨科杂志

Objective:To evaluate the feasibility of using cortical bone trajectory (CBT) screws in the osteoporotic thoracolumbar fixation by comparing the bone CT values at the bone-screw interface between traditional trajectory (TT) screws and CBT screws in patients with different bone densities.Methods:The high-resolution CT imaging data of thoracolumbar segments following thoracic or lumbar spine fractures from April 2020 to October 2022 were collected at The Second Hospital Affiliated to Wenzhou Medical University for retrospective analysis. They were divided into 3 groups: a normal bone mass group, an osteopenia group and an osteoporosis group. From each group 30 cases were chosen (90 cases in total, 36 males and 54 females). All the data were imported into Mimics 18.0 for three-dimensional bone reconstruction in which placement of TT and CBT screws was simulated on the vertebrae from T10 to L2 (non-fractured vertebrae). Regions of interest (ROI) where each simulated screw intersected the bone were segmented to measure their CT bone values. For each vertebra in each group, the relative difference percentage in average CT value of ROI between TT and CBT screws was calculated. The CT values of ROI were compared in the same group between TT and CBT screws from T10 to L2; the CT values of ROI were compared in the same screws among the 3 groups from T10 to L2; the CT values of ROI were compared between the CBT screws in the osteopenia and osteoporosis groups and the TT screws in the normal bone mass group; the relative difference percentages in average CT value of ROI between CBT and TT screws were compared between the 3 groups from T10 to L2.Results:The average CT value of ROI for CBT screws was significantly higher than that for TT screws from T10 to L2 in every group ( P< 0.001); as for the CT values of ROI for CBT and TT screws from T10 to L2, the osteoporosis group<the osteopenia group<the normal bone mass group ( P<0.001); from T10 to L2, the CT value of ROI for CBT screws in the osteopenia group was significantly higher than that for TT screws in the normal bone mass group ( P<0.001); the CT value of ROI for CBT screws in the osteoporosis group was not significantly different from that for TT screws in the normal bone mass group ( P>0.05). At T10, T12, and L1, the relative difference percentage in average CT value of ROI between CBT and TT screws was significantly higher in the osteopenia and osteoporosis groups than that in the normal bone mass group ( P<0.05), but there was no such a difference between the osteopenia and the osteoporosis groups ( P>0.05). At T11 and L2, there was no significant difference between the 3 groups in the relative difference percentage in average CT value of ROI between CBT and TT screws ( P>0.05). Conclusions:As bone mass decreases, both CBT and TT screws lead to a significant decrease in the bone density at the bone-screw interface. In patients with osteoporosis, CBT screws can still lead to a higher bone density at the bone-screw interface than TT screws, thus providing a higher strength at the bone-screw interface.

Biomechanical Comparison of Internal Fixation by Traditional and Cortical Bone Trajectory Pedicle Screw / 医用生物力学

Objective To compare the effects of cortical bone trajectory ( CBT) and traditional trajectory ( TT)pedicle screw internal fixation on the range of motion (ROM) and rod system stress of normal and osteoporotic(OP) spines. Methods The L3-S1 finite element models of normal and OP spines were established. The screwrod system with two kinds of trajectory was used for internal fixation of the L4-5 segment, so as to simulate sixphysiological loads, namely, flexion, extension, left / right bending, left / right rotation. The effects of two internalfixation methods on ROMs and maximum equivalent stress of screws in normal and OP spines were compared.Results For both bone conditions, CBT and TT significantly reduced ROM of the fixed segment (L4-5) and theentire segment of lower lumbar spine ( L3-S1). However, the ROM decline of CBT group was slightly smaller than that of TT group, and their ROMs were similar under flexion and extension, but the ROM differences were significant under lateral bending and axial rotation. In addition, for both the normal and OP spine models, themaximum equivalent stress of screws in CBT group was significantly higher than that in TT group. Compared withTT group, the screw stress of CBT group in normal spine model under flexion and extension, lateral bending,axial rotation was increased by 27% , 268% and 58% , respectively. However, when CBT technique was used atthe same time, the OP spine model had a smaller screw stress distribution than the normal spine model.Conclusions Compared with TT technique, CBT technique can achieve higher screw stress under OP conditionand reduce screw stress concentration under normal bone condition. In addition, CBT slightly increases ROMs of each segment, which is conducive to recovery of spinal physiological function after surgery. Lateral bending and axial rotation can produce negative mechanical effects, and these two physiological loads should be avoided.

Cadaveric study of anatomical measurement of isthmus parameters of lumbar spine to guide cortical bone screw placement

SUMMARY OBJECTIVE: To reduce surgical exposure and improve accuracy, this study evaluated the anatomical distance parameter D (including D1, D2, and D3) of the lumbar isthmus for cortical bone screw insertion. METHODS: A total of 25 structurally complete lumbar dry specimens were used for lumbar anatomy measurements. The six cadaver specimens were divided into upper and lower parts on the plane of the T11-T12 vertebrae, and we use the lower parts. Therefore, six lumbar wet specimens and another four complete lumbar dry specimens were selected. The lumbar isthmus tangent point was considered a coordinate origin, and the insertion point was determined through translating the distance of D1 value to the midline of the vertebral body horizontally and then vertically moved toward inferior board of the transverse process with the distance of D3 value. RESULTS: In four dry and six wet intact lumbar specimens, cortical bone screws were placed according to the average value of the isthmus parameter D. A total of 100 trajectories were verified in specimens by X-ray and computed topography scan to evaluate the safety, accuracy, and feasibility of the surgical use of isthmus parameter D. Using this parameter, the rates of excellent screw placement were 95% (38/40) in four dry specimens and 88.7% (53/60) in six wet specimens. CONCLUSION: The isthmus parameter D is easier to use by the operator, which can improve surgical accuracy and reduce operation time. LEVEL OF EVIDENCE: Level IV, prospective study.

Finite Element Analysis on Biomechanical Properties of Traditional Trajectory and Modified Cortical Bone Trajectory / 医用生物力学

Objective To study mechanical properties of traditional trajectory (TT) and modified cortical bone trajectory (MCBT) on osteoporotic vertebrae through finite element analysis. Methods The three-dimensional model of L4 segment was established, and pedicle screw (PS) (diameter 6.0 mm, length 45 mm) and MCBT screw (diameter 4.5 mm, length 40 mm) were placed on both sides of the lumbar spine. The pull-out strength and the load-displacement ratio of screws in two different screw trajectories under up, down, left, right working conditions were analyzed, and the stability between the screw and vertebral body under osteoporotic conditions was evaluated. Results Compared with TT, the pull-out strength of MCBT screw was increased by 13.1%. Compared with PS, the load-displacement ratio of MCBT screw under up, down and left working conditions was increased by 57.2%, 32.4%, and 31.6%. Under right working condition, although the load-displacement ratio of MCBT screw was higher than that of PS, no statistical difference was found. The load-displacement ratio of vertebral body in MCBT group under lateral bending and axial rotation was significantly higher than that in TT group. The load-displacement ratio of vertebral body in MCBT group under flexion was lower than that in TT group. Although the load-displacement ratio of vertebral body in MCBT group under extension was higher that that in TT group, no statistical difference was found. Conclusions MCBT is superior to TT in pull-out strength, screw stability and vertebral body stability under lateral bending and axial rotation, but its vertebral body stability under flexion and extension was weaker than that of TT. The research findings demonstrate the superiority of MCBT under osteoporotic conditions and lay the foundation for clinical application of MCBT.

Two-Year Outcomes of Midline lumbar Fusion Versus Minimally Invasive Transforaminal Lumbar Interbody Fusion in the Treatment of L4-L5 Degenerative Disease / 生物医学与环境科学（英文）

Objective@#We aimed to compare the clinical and radiological outcomes of midline lumbar fusion (MIDLF) versus minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) in patients with degenerative spondylolisthesis and/or stenosis in L4-L5 two years after surgery.@*Methods@#Consecutively treated patients with lumbar pathology who underwent MIDLF ( @*Results@#The mean operative time and hematocrit (HCT, Day 1) were significantly shorter and lower in MIDLF cases (174 min @*Conclusion@#MIDLF is comparable to MI-TLIF at L4-5 in clinical outcomes and fusion rates, and the results verified the meaningful advantage of using MIDLF for the elderly with osteoporosis.

Application of three-dimensional reconstruction simulation to define the starting point of lumbar cortical bone trajectory / 中国修复重建外科杂志

Objective: CT three-dimensional reconstruction technology was used to simulate the placement of the lumbar cortical bone trajectory (CBT), to determine the starting point and direction of the screw trajectory. Methods: Between February 2017 and April 2018, 24 patients with lumbar CT were selected as the study object. There were 7 males and 17 females, with an average age of 50.4 years (range, 37-68 years). The CT DICOM data of patients were imported into Mimics 16.0 software, and the three-dimensional model of lumbar spine was established. A 5 mm diameter cylinder was set up to simulate the CBT by using Mimics 16.0 software. According to the different implant schemes, the study was divided into groups A, B, and C, the track of the screw respectively passed through the upper edge, the medial edge, and the lower edge of the isthmus of the pedicle. The intersection of simulated screw and lumbar spine was marked as region of interest (ROI) and a mask was generated. The average CT value [Hounsfield unit (HU)] and the screw length of ROI were automatically measured by Mimics 16.0 software. In addition, the head inclination angle and head camber angle of the screw were measured respectively. Point F was the intersection of the level of the lowest edge of the transverse process and the lumbar isthmus periphery. The horizontal and vertical distance between point F and the starting point were measured, and the relationship between the three schemes and the position of the zygapophysial joint and spinous process was observed. Results: Plan A has the highest ROI average HU, with the maximum value appearing in L 4; plan B has the longest screw length, with the maximum value appearing in L 5; plan C has the largest nail track head inclination angle, with the maximum value appearing in L 4; plan B has the largest nail track head camber angle, with the maximum value appearing in L 3. The screw length and head camber angle of the nail in group B were significantly greater than those in groups A and C ( P0.05). In plan A, 74.48% (143/192) screws had a horizontal distance of -2 to 4 mm from point F, a vertical distance of 6-14 mm from point F, a head inclination angle of (14.64±2.77)°, and a head camber angle of (6.55±2.09)°, respectively; in plan B, 84.58% (203/240) screws had a horizontal distance of 1-6 mm from point F, a vertical distance of 1-5 mm from point F, a head inclination angle of (26.93±2.21)°, and a head camber angle of (10.29±2.46)°, respectively; in plan C, 85.94% (165/192) screws had a horizontal distance of -2 to 3 mm from point F, a vertical distance of -2 to 4 mm from point F, a head inclination angle of (33.50±3.69)°, and a head camber angle of (6.47±2.48)°, respectively. Conclusion: Plan B should be selected as the starting point of the L 1-L 5 CBT implant. It is located at the intersection of the lowest horizontal line of the transverse process root and the lateral edge of the lumbar isthmus, which is 1-6 mm horizontally inward, 1-5 mm vertically upward, with a head inclination angle of (26.93±2.21)°, and a head camber angle of (10.29±2.46)°, respectively.

Effect of Indirect Neural Decompression with Oblique Lateral Interbody Fusion Was Influenced by Preoperative Lumbar Lordosis in Adult Spinal Deformity Surgery

STUDY DESIGN: Retrospective clinical study on the indirect decompressive effect of oblique lateral interbody fusion (OLIF) for adult spinal deformity. PURPOSE: To evaluate the effect of interbody distraction by OLIF for the treatment of adult spinal deformity. OVERVIEW OF LITERATURE: Adult spinal deformity with symptomatic stenosis has been addressed conventionally using a direct posterior decompression approach with fusion. However, stenotic symptoms can also be alleviated indirectly through restoration of intervertebral and foraminal heights and correction of spinal alignment. METHODS: Twenty-eight patients with adult spinal deformity underwent OLIF combined with modified cortical bone trajectory screws at 94 lumbar levels with neuromonitoring. The patients were divided into three groups based on their preoperative lumbar lordosis: group A, 20°. The cross-sectional area (CSA) of the thecal sac was measured preoperatively and postoperatively on axial magnetic resonance images. Differences in CSA were evaluated, and the relationship between the CSA extension ratio and preoperative CSA was assessed. Changes in disc height and segmental disc angle were measured from plain radiographs. RESULTS: OLIFs were performed successfully without neural complications. In group A, the mean CSA increased from 120.6 mm² preoperatively to 148.5 mm² postoperatively (p<0.001). The mean CSA for group B increased from 120.1 mm² preoperatively to 154.4 mm² postoperatively (p<0.001). Group C had an increase in mean CSA from 114.7 mm² preoperatively to 160.7 mm² postoperatively (p<0.001). The mean CSA enlargement ratio was 27.5%, 32.1%, and 60.4% in groups A, B, and C, respectively. The mean CSA extension ratio was inversely correlated with preoperative CSA. CONCLUSIONS: The effect of indirect neural decompression in adult spinal deformity with OLIF varies with the degree of preoperative lumbar lordosis.

Early Fusion Status after Posterior Lumbar Interbody Fusion with Cortical Bone Trajectory Screw Fixation: A Comparison of Titanium-Coated Polyetheretherketone Cages and Carbon Polyetheretherketone Cages

STUDY DESIGN: Retrospective cohort study. PURPOSE: We recently reported that when compared to posterior lumbar interbody fusion (PLIF) using traditional pedicle screw fixation, PLIF with cortical bone trajectory screw fixation (CBT-PLIF) provided favorable clinical outcomes and reduced the incidence of symptomatic adjacent segment pathology, but resulted in relatively lower fusion rates. Since titanium-coated polyetheretherketone (PEEK) cages (TP) could improve and accelerate fusion status after CBT-PLIF, early fusion status was compared between CBT-PLIF using TP and carbon PEEK cages (CP). OVERVIEW OF LITERATURE: A systematic review demonstrated that clinical studies at this early stage show similar fusion rates for TP compared to PEEK cages. METHODS: We studied 36 consecutive patients undergoing CBT-PLIF with TP (TP group) and 92 undergoing CBT-PLIF with CP (CP group). On multiplanar reconstruction computed tomography (MPR-CT) at 6 months postoperatively, vertebral endplate cysts (cyst signs) were evaluated and classified as diffuse or local cysts. Early fusion status was assessed by dynamic plain radiographs and MPR-CT at 1 year postoperatively. RESULTS: The incidences of cyst signs, diffuse cysts, and early fusion rate in the TP and CP groups were 38.9% and 66.3% (p0.05), respectively. Combining the two groups, 22 of 36 patients with diffuse cysts had nonunion at 1-year follow-up, compared to only three of 92 patients with local cysts or without cyst signs (p<0.01). CONCLUSIONS: Despite having fewer patients with endplate cysts at 6 months (a known risk factor for nonunion), the TP group had the same fusion rate as the CP group at 1-year follow-up. Thus, TP did not accelerate the fusion process after CBT-PLIF.

Biomechanical Evaluation of Upper-Middle Thoracic Vertebrae Fixed by Cortical Bone Trajectory Screws: A Finite Element Simulation Study / 医用生物力学

Objective To compare biomechanical properties of cortical bone trajectory (CBT) screw and traditional trajectory screw for fixing upper-middle thoracic spine. Methods The tomography images were obtained by CT scanning of normal T7 and T8 segments, and the three-dimensional (3D) model of T7-8 was reconstructed by Mimics software. The finite element model of upper-middle thoracic spine was established by optimizing FreeForm model and pre-processing function of ANSYS software. On this basis, the CBT screw and pedicle screw fixation models after discectomy were established, and 5 N·m flexion, extension, lateral bending and rotation loads were applied to the two model groups, respectively. The displacement and peak stress of vertebrae and implants under different working conditions were compared and analyzed. Results Under different loading conditions, the maximum displacement of CBT screw group was lower than that of pedicle screw group, and the range of motion of CBT screw group was lower than that of pedicle screw group. The stress level of both models was close, and the stress of CBT screw group was slightly lower than that of pedicle screw group. Under the load of flexion, extension and rotation, the maximum vertebral stress of pedicle screw group decreased by 31%, 17% and 18% compared with that of CBT screw group, and under lateral bending load, the vertebral stress of CBT screw group was 20% lower than that of pedicle screw group. Under the load of flexion and rotation, the maximum stress of pedicle screw group decreased by 2% and 11%; however, the maximum stress of CBT screw group was 11% and 1% lower than that of pedicle screw group. Conclusions The stability of CBT screw was better than that of pedicle screw, and the overall stress distribution was similar to that of pedicle screw. However, the vertebral stress distribution of CBT group was slightly inferior. The research findings provide a theoretical basis for the clinical application of cortical screw fixation after the failure in pedicle screw fixation for the upper-middle thoracic vertebrae.

Application of cortical bone trajectory screw in elderly patients with lumbar tuberculosis / 中国骨伤

OBJECTIVE@#To explore the clinical effect of cortical bone trajectory screw technology combined with anterior mini-open debridement and prop graft for lumbar tuberculosis in elderly.@*METHODS@#The clinical data of 22 patients with lumbar tuberculosis treated by cortical bone trajectory screw technology combined with anterior mini-open debridement and prop graft from February 2015 to December 2016 were retrospectively analyzed. There were 13 males and 9 females with an average age of (73.3±7.1) years old. The pre-operative Frankel grading showed that 2 cases were grade B, 5 cases were grade C, 6 were grade D, and 9 were grade E. Pre- and post-operative kyphosis Cobb angle, visual analogue scale (VAS), erythrocyte sedimentation rate(ESR) and the Frankel grade were analyzed, the conditions of complication, stability of internal plants, graft fusion were observed.@*RESULTS@#All 22 patients were follow-up for 12 to 24 months with an average of (18.7±4.6) years. Two patients with contralateral psoas major muscle abscess enlarged at 3 months after operation and were cured by drainage under the guidance of type-B ultrasonic. Other 20 cases got primary healing without sinus formation and recurrence of spinal tuberculosis. At the final follow-up, the Frankel grading showed that 3 cases was grade C, 5 cases were grade D, and 14 cases were grade E. The Cobb angle, visual analogue scale (VAS), ESR were respectively decreased from preoperative(17.68±3.86)°, (6.95±2.26) points, (47.14±20.85)mm/h to (4.77±2.47)°, (2.18±1.59) points, (16.77±11.42) mm/h at final follow-up. X-ray and CT scan showed bone union for 3 to 8 months after operation, with a mean time of(4.9±1.2) months.@*CONCLUSIONS@#It is effective method to treat lumbar tuberculosis with cortical bone trajectory screw technology combined with anterior mini-open debridement and prop graft.

Validity study of Coda Motion Analysis System for measuring cervical lateral flexion in normal adults / 中国骨伤

OBJECTIVE@#To investigate the validity of Coda Motion Analysis System for measuring cervical lateral flexion in normal adults in order to explore a new measuring tool for clinical and research practice.@*METHODS@#A total of 43 participants were involved in the study. Cervical range of lateral flexion were measured with Coda Motion Analysis System and "gold standard" X-ray simultaneously. The validity and agreement were assessed using the scatter diagram, the Pearson correlation coefficient and limits of agreement.@*RESULTS@#Cervical range of lateral flexion measured by Coda Motion Analysis System had no statistical differences with those measured by X-ray(>0.05). The Coda Motion Analysis System demonstrated a very good linear relation with the X-ray measurements in cervical range of right lateral flexion, left flexion and total lateral flexion, and the Pearson correlation coefficients were 0.72, 0.85 and 0.90 respectively.@*CONCLUSIONS@#Coda Motion Analysis System showed good validity for measuring cervical lateral flexion in normal adults. Because the reliability of Coda Motion Analysis System was established previously, the results of this study suggest that the system has the potential to be used to measure cervical lateral flexion in clinical and research practice.

Review of Cortical Bone Trajectory: Evidence of a New Technique

This article summarizes recent evidence on the cortical bone trajectory (CBT) obtained from published anatomical, biomechanical, and clinical studies. CBT was proposed by Santoni in 2009 as a new trajectory that can improve the fixation of pedicle screws in response to screw loosening in osteoporotic patients. Recently, research interest has been growing with increasing numbers of published series and frequent reports of new applications. We performed an online database search using the terms “cortical bone trajectory,”“pedicle screw,”“CBT spine,”“CBT fixation,”“MISS CBT,” and “traditional trajectory.” The search included the PubMed, Ovid MEDLINE, Cochrane, and Google Scholar databases, resulting in an analysis of 42 articles in total. These covered three aspects of CBT research: anatomical studies, biomechanical parameters, and clinical cases or series. Compared to the traditional trajectory, CBT improves pullout strength, provides greater stiffness in cephalocaudal and mediolateral loading, and shows superior resistance to flexion/extension; however, it is inferior in lateral bending and axial rotation. CBT seems to provide better immediate implant stability. In clinical studies, CBT has shown better perioperative results for blood loss, length of stay in hospital, and surgery time; similar or better clinical postoperative scores; and similar comorbidity, without any major fixation system complications due to instrumentation failure or screw misplacement. In addition, advantages such as less lateral exposure allow it to be used as a minimally invasive technique. However, most of the clinical studies were retrospective case series or case-control studies; prospective evidence on this technique is scarce, making a definitive comparison with the traditional trajectory difficult. Nevertheless, we can conclude that CBT is a safe technique that offers good clinical results with similar biomechanical and perioperative parameters to those of the traditional trajectory. In addition, new applications can improve its results and make it useful for additional pathologies.

Surgical Usage of a Cortical Bone Trajectory Pedicle Screw to Treat Lumbar Pyogenic Spondylodiscitis: Preliminary Report

STUDY DESIGN: Retrospective clinical study. OBJECTIVES: To assess the efficacy of a cortical bone trajectory pedicle screw (CBT-PS) for the treatment of lumbar pyogenic spondylodiscitis. SUMMARY OF LITERATURE REVIEW: Pedicle screws were used for surgical treatment of pyogenic spondylodiscitis to prevent instability and deformity. CTB-PS are typically inserted from the inferomedial to superolateral direction of the pedicle and have yielded satisfactory results in degenerative or osteoporotic spinal disorders. MATERIALS AND METHODS: Eight patients with single segment lumbar pyogenic spondylodiscitis were analyzed. At first, anterior debridements and interbody fusions were perfomed with autogenous strut bone grafts, followed by posterior fixations and fusions with CBT-PS. The lordotic angles of operated levels were checked at the preoperative, postoperative, and final follow-ups. Visual analogue scales (VAS) were checked at the preoperative and final follow-ups. RESULTS: Lesion sites were found at four L3-4, three L4-5, and one L2-3. Follow-ups were held at 26.13±8.23 months. The lordotic angles at preoperative, postoperative, and final follow-ups were 12.13±3.09°, 14.63±3.16°, and 12.75±3.99°, retrospectively. There were significant differences between results from the preoperative-postoperative and postoperative-final follow ups. There was no difference in the preoperative-final follow up. There was a significant difference between the VAS at the preoperative and final follow-ups (8.13±0.83 and 2.38±0.92, retrospectively). Complete bony unions of were observed at the final follow-up in all cases. CONCLUSIONS: The advantages of using a CBT-PS for lumbar pyogenic spondylodiscitis included the ability to minimize damage from the screw for both the posterior structure damage and the operated anterior area to prevent instability and deformity, and to achieve rigid bone union. CBT-PS is a potential surgical option for pyogenic spondylodiscitis.

Short-Term Clinical Result of Cortical Bone Trajectory Technique for the Treatment of Degenerative Lumbar Spondylolisthesis with More than 1-Year Follow-Up

STUDY DESIGN: Retrospective follow-up study on the result of surgical treatment for patients with degenerative lumbar spondylolisthesis (DLS) using cortical bone trajectory (CBT) technique. PURPOSE: To evaluate the capability of CBT to manage patients with DLS. OVERVIEW OF LITERATURE: CBT is a recently advocated, novel, less-invasive technique of lumbar pedicle screw, which provides enhanced screw purchase by maximizing the thread contact with higher density bone surface. Despite the frequent use of CBT technique in the lumbar spine surgery, little is known of the capability of this technique to manage patients with DLS. METHODS: Thirty two consecutive patients (5 males, 27 females) surgically treated with single-level DLS in our institute using CBT were included. All patients were followed up at least 12 months (mean 24 months). Their clinical and radiological features were measured. RESULTS: Good leg pain relief was achieved in all patients. The mean postoperative percentage slip demonstrated significant reduction with significant neurological recovery when compared with preoperative percentage slip, and it was maintained until the latest follow-up. Loss of correction of more than 3 mm during the follow-up period was observed in 3 cases. Surgical site infection was observed in one case; however, pull-out of PSs or neurological deterioration was not found. No patient needed additional surgery during the follow-up period. CONCLUSIONS: These preliminary results confirmed that CBT is useful for the treatment for patients with DLS. This technique allows good reduction of spondylolisthesis and neurological improvement.

Radiological Evaluation of the Initial Fixation between Cortical Bone Trajectory and Conventional Pedicle Screw Technique for Lumbar Degenerative Spondylolisthesis

STUDY DESIGN: Retrospective study. PURPOSE: To compare initial fixation using the cortical bone trajectory (CBT) technique versus conventional pedicle screws (PS) in radiographs of postsurgical lumbar degenerative spondylolisthesis. OVERVIEW OF LITERATURE: Few reports have documented the holding strength of CBT technique for spondylolisthesis cases. METHODS: From October 2009 to June 2014, 21 cases of degenerative spondylolisthesis were surgically treated in our institution. Ten were treated with conventional PS technique and 11 of with CBT technique. Mean lumbar lordosis and percent slippage were evaluated preoperatively, immediately after surgery, and 6 months and 1 year postoperatively using radiographs. We also investigated percent loss of slip reduction. RESULTS: There were statistically significant differences between preoperative percent slippage and postoperative slippage in both PS and CBT procedures over 1 year, and both techniques showed good slip reduction. On the other hand, lumbar lordosis did not change significantly in either the PS or CBT groups over 1 year. CONCLUSIONS: CBT technique showed similarly good initial fixation compared with the PS procedure in the treatment of lumbar degenerative spondylolisthesis.

Significance of the Pars Interarticularis in the Cortical Bone Trajectory Screw Technique: An In Vivo Insertional Torque Study

STUDY DESIGN: Retrospective study. PURPOSE: Cortical bone trajectory (CBT), a more medial-to-lateral and shorter path than the traditional one for spinal fusion, is thought to be effective for severely degenerated vertebrae because screws are primarily stabilized at the posterior elements. We evaluated the efficacy of this approach through in vivo insertional torque measurement. OVERVIEW OF LITERATURE: There has been only one prior in vivo study on CBT insertional torque. METHODS: Between January 2013 and April 2014, a total of 22 patients underwent posterior lumbar fusion using the CBT technique. The maximum insertional torque, which covers the radial strength needed for insertion, was measured for 113 screws, 8 of which were inserted for L5 spondylolysis. The insertional torque for cases with (n=8) and without (n=31) spondylolysis of L5 were compared using one-way analysis of variance (ANOVA). To evaluate vertebral degeneration, we classified 53 vertebrae without spondylolysis by lumbar radiography using semiquantitative methods; the insertional torque for the 105 screws used was compared on the basis of this classification. Additionally, differences in insertional torque among cases grouped by age, sex, and lumbar level were evaluated for these 105 screws using ANOVA and the Tukey test. RESULTS: The mean insertional torque was significantly lower for patients with spondylolysis than for those without spondylolysis (4.25 vs. 8.24 in-lb). There were no statistical differences in insertional torque according to vertebral grading or level. The only significant difference in insertional torque between age and sex groups was in men <75 years and women ≥75 years (10 vs. 5.5 in-lb). CONCLUSIONS: Although CBT should be used with great caution in patient with lysis who are ≥75 years, it is well suited for dealing with severely degenerated vertebrae because the pars interarticularis plays a very important role in the implementation of this technique.

Curative effect of cortical bone trajectory screw combined with pedicle screw in internal fixation for senile osteoporosis lumbar degenerative disease / 第二军医大学学报

Objective To evaluate the curative effect of cortical bone trajectory (CBT) screw in combination with pedicle screw in lumbar posterior decompression. bone graft and internal fixation for the treatment of osteoporosis lumbar degenerative diseases. Methods From February 2014 to April 2015. 32 patients with osteoporosis lumbar degenerative diseases underwent posterior decompression, bone gratt and internal fixation after invalid conservative treatment. Internal fixation was performed by pedicle screws in 20 patients (A group) and by CBT screws combined with pedicle screws in 12 patients (B group). The recovery, operation time, intraoperative blood loss and VAS scores before and after operation, and JOA score were recorded in the two groups. Results The symptoms were improved in all the 32 patients. After surgery. JOA scores were significantly increased and VAS scores were significantly decreased. There were no significant differences in terms of operation time. blood loss. JOA score or VAS score between the two groups (P>0. 05). In A group. one side pedicle screw placement failed due to osteoporosis in 2 cases and unilateral fixation was subsequently carried out No poor screw holding force. nailing failure. or fracture breakage appeared in B group. No vascular or nerve damage caused by nailing was found in B group. The postoperative radiographic follow-up showed no screw loosening, fall-off or collapse; and the screw. connector, and fusion cage were all at the right position. There were no any adverse events in the two groups. Conclusion CBT screws in combination with pedicle screws in lumbar internal fixation have the advantage of less muscle and sott tissue injuries. strong screw holding force. and satisfied early curative effect in treating senile osteoporosis lumbar degenerative diseases.

Fixation Strength of Caudal Pedicle Screws after Posterior Lumbar Interbody Fusion with the Modified Cortical Bone Trajectory Screw Method

STUDY DESIGN: Clinical case series. PURPOSE: In the posterior lumbar interbody fusion (PLIF) procedure in our institute, the cephalad screw trajectory follows a mediolateral and caudocephalad directed path according to the original cortical bone trajectory (CBT) method. However, the starting point of the caudal screw is at the medial border of the pedicle on an articular surface of the superior articular process, and the trajectory takes a mediolateral path parallel to the cephalad endplate. The incidence of caudal screw loosening after PLIF with this modified CBT screw method was investigated, and significant risk factors for caudal screw loosening were evaluated. OVERVIEW OF LITERATURE: A biomechanical study of this modified caudal screw trajectory using the finite element method reported about a 20% increase in uniaxial yield pullout load compared with the traditional trajectory. However, there has been no clinical study concerning the fixation strength of this modified caudal screw trajectory. METHODS: The subjects were 193 consecutive patients who underwent single-level PLIF with modified CBT screw fixation. Caudal screw loosening was checked in computed tomography at 6 months after surgery, and screw loosening was defined as a radiolucency of 1 mm or more at the bone-screw interface. RESULTS: The incidence of caudal screw loosening after lumbosacral PLIF (46.2%) was significantly higher than that after floating PLIF (6.0%). No significant differences in sex, brand of the instruments, and diameter and length of the caudal screw were evident between patients with and without caudal screw loosening. Patients with caudal screw loosening were significantly older at the time of surgery than patients without caudal screw loosening. CONCLUSIONS: Fixation strength of the caudal screw after floating PLIF with this modified CBT screw technique was sufficiently acceptable. Fixation strength after the lumbosacral procedure was not.

Short-Term Results of Transforaminal Lumbar Interbody Fusion Using Pedicle Screw with Cortical Bone Trajectory Compared with Conventional Trajectory

STUDY DESIGN: Case-control study. PURPOSE: To evaluate clinical and radiological results of transforaminal lumbar interbody fusion (TLIF) performed with cortical bone trajectory (CBT) pedicle screw insertion with those of TLIF using 'conventional' or percutaneous pedicle screw insertion. OVERVIEW OF LITERATURE: CBT is a new trajectory for pedicle screw insertion in the lumbar spine; clinical and radiological results of TLIF using pedicle screws inserted with CBT are unclear. METHODS: In total, 26 patients (11 males, 15 females) were enrolled in this retrospective study and divided into three groups: TLIF with pedicle screw insertion by conventional minimally invasive methods via the Wiltse approach (M-TLIF, n=10), TLIF with percutaneous pedicle screw insertion (P-TLIF, n=6), and TLIF with pedicle screw insertion with CBT (CBT-TLIF, n=10). Surgical results and preand postoperative radiological findings were evaluated and compared. RESULTS: Intraoperative blood loss was significantly less with CBT-TLIF (p=0.03) than with M-TLIF. Postoperative lordotic angles did not differ significantly among the three groups. Complete fusions were obtained in 10 of 12 levels (83%) with M-TLIF, in seven levels (100%) with P-TLIF, and in 10 of 11 levels (91%) with CBT-TLIF. On postoperative computed tomography, correct positioning was seen in 84.1% of M-TLIF screws, 88.5% of P-TLIF screws, and 90% of CBT-TLIF screws. CONCLUSIONS: CBT-TLIF resulted in less blood loss and a shorter operative duration than M-TLIF or P-TLIF. Postoperative rates of bone union, maintenance of lordotic angles, and accuracy of pedicle screw positions were similar among the three groups.

Clear Zone Formation around Screws in the Early Postoperative Stages after Posterior Lumbar Fusion Using the Cortical Bone Trajectory Technique

STUDY DESIGN: Retrospective study. PURPOSE: To evaluate the initial fixation using the cortical bone trajectory (CBT) technique for posterior lumbar fusion through assessment of the clear zones around the screws and the risk factors involved. OVERVIEW OF LITERATURE: Postoperative radiolucent zones (clear zones) are an indicator of poor conventional pedicle screw fixation. METHODS: Between January 2013 and April 2014, 19 patients (8 men and 11 women) underwent posterior lumbar interbody fusion or posterior lumbar fusion using the CBT technique. A total of 109 screws were used for evaluation with measurement of the maximum insertional torque of last two screw rotations. Clear zone-positivity on plain radiographs was investigated 6 months after surgery. The relation between intraoperative insertional torque and clear zone-positivity was investigated by one-way analysis of variance. In addition, the correlation between clear zone-positivity and gender, age (75 years old), or operative stabilization level (3 vertebral levels) was evaluated using the chi-square test. RESULTS: Clear zones were observed around six screws (5.50%) in five patients (26.3%). The mean insertional torque (4.00+/-2.09 inlbs) of clear zone-positive screws was lower than that of clear zone-negative screws (8.12+/-0.50 in-lbs), but the difference was not significant. There was a significant correlation between clear zone-positivity and operative level of stabilization. CONCLUSIONS: The low incidence of clear zone-positive screws indicates good initial fixation using the CBT technique. Multilevel fusions may be risk factors for clear zone generation.