Novel placement of cortical bone trajectory screws in previously instrumented pedicles for adjacent-segment lumbar disease using CT image-guided navigation

Top 25 Most Cited Articles on Intraoperative Computer Tomography-Guided Navigation in Spine Surgery

BACKGROUND

In recent years, the use of intraoperative computer tomography-guided (CT-guided) navigation has gained significant popularity among health care providers who perform minimally invasive spine surgery. This review aims to identify and analyze trends in the literature related to the widespread adoption of CT-guided navigation in spine surgery, emphasizing the shift from conventional fluoroscopy-based techniques to CT-guided navigation.

METHODS

Articles pertaining to this study were identified via a database review and were hierarchically organized based on the number of citations. An "advanced document search" was performed on September 28th, 2022, utilizing Boolean search operator terms. The 25 most referenced articles were combined into a primary list after sorting results in descending order based on the total number of citations.

RESULTS

The "Top 25" list for intraoperative CT-guided navigation in spine surgery cumulatively received a total of 2742 citations, with an average of 12 new citations annually. The number of citations ranged from 246 for the most cited article to 60 for the 25th most cited article. The most cited article was a paper by Siewerdsen et al., with 246 total citations, averaging 15 new citations per year.

CONCLUSIONS

Intraoperative CT-guided navigation is 1 of many technological advances that is used to increase surgical accuracy, and it has become an increasingly popular alternative to conventional fluoroscopy-based techniques. Given the increasing adoption of intraoperative CT-guided navigation in spine surgery, this review provides impactful evidence for its utility in spine surgery.

The accuracy of cortical bone trajectory screw placement guided by spinous process clamp hardware in lumbar spinal surgery: a retrospective study

This study aimed to assess the accuracy of cortical bone trajectory (CBT) screws placement guided by a spinous process clamp (SPC) guide. A total of 32 patients who received single-level midline lumbar fusion (MIDLF) surgery between June 2019 and January 2020 were retrospectively analyzed and divided into free-hand (FH) and SPC-guided groups according to the surgical approach. In the FH group, CBT screws was implanted with the assistance of fluoroscopy, while in the SPC group, CBT screws was implanted using the SPC navigator hardwire. A total of 128 screws were assessed in this study, with higher rates of clinically acceptable screw placement (grades A and B) and grade A screws in the SPC group than in the FH guide group (92.2% vs. 79.7%, P = 0.042 and 54.7% vs. 35.9%, P = 0.033, respectively). Misplacement screws (grades C, D, and E) occurred more often in the FH group than in the SPC guide group (20.3% vs. 7.8%, P = 0.042). The incidence of proximal facet joint violation (FJV) was higher in the FH group than in the SPC group (15.6% vs. 3.1%, P = 0.030). The radiation dose and time in the SPC guide group were comparable to those in the FH group (P = 0.063 and P = 0.078). The average operative time was significantly longer in the SPC guide group than in the FH group (267.8 ± 45.5 min vs. 210.9 ± 44.5 min, P = 0.001). Other clinical parameters, such as the average bone mineral density (BMD), intraoperative blood loss, and postoperative hospital stay, were not significantly different. Oswestry disability index (ODI) and back pain visual analogue scale (VAS) scores were significantly improved in both groups compared with preoperatively. SPC guided screw placement was more accurate than the fluoroscopy-assisted FH technique for single-level MIDLF at L4/5. Patients undergoing SPC-guided screw placement can achieve similar clinical outcomes as the fluoroscopy-assisted FH technique.

The Cortical Bone Trajectory Screw Technique Assisted by the Mazor Renaissance Robotic System as a Salvage Strategy for Failed Lumbar Spine Surgery: Technical Note and Case Series

Purpose

The objective of this study was to describe the Mazor Renaissance robotic system-assisted CBT (cortical bone trajectory) screw technique as a salvage strategy for failed lumbar spine surgery.

Patients and Methods

Between January 2018 and June 2022, 7 patients underwent salvage surgery with the CBT screw fixation technique assisted by the Mazor Renaissance robot system in our institution. Intraoperative observations were recorded for blood loss, duration of operation, and fluoroscopy time. Complications related to CBT screws were also recorded. The accuracy of CBT screws was recorded in accordance with the modified Gertzbein-Robbins classification. The JOA (Japanese Orthopedic Association) score for low back pain was used to evaluate surgical outcomes.

Results

A total of 26 CBT screws were placed in 7 patients, including 4 females and 3 males. Three patients underwent ASD (adjacent segment disease) and four patients underwent lumbar union failure with loose or compromised PSs (pedicle screws). The mean operation time was 129.29 ± 32.97 minutes, the mean blood loss was 180 ± 52.60 mL, and the mean intraoperative fluoroscopy time was 14.29 ± 3.15 s. All screws were clinically acceptable according to the Gertzbein-Robbins classification. There were no complications related to CBT screws in any of the cases. The JOA scores for low back pain of all patients were significantly improved at the final follow-up.

Conclusion

The CBT screw fixation technique supplemented the traditional PS fixation technique, which can be performed as a salvage strategy for failed lumbar spine surgery and achieved good clinical results. The spinal robot was very helpful in evaluating pedicle size and determining CBT screw direction, especially in a previously instrumented lumbar pedicle.

Multitrack and multianchor point screw technique combined with the Wiltse approach for lesion debridement for lumbar tuberculosis

BACKGROUND

The incidence of lumbar tuberculosis is high worldwide, and effective treatment is a continuing problem.

AIM

To study the safety and efficacy of the multitrack and multianchor point screw technique combined with the contralateral Wiltse approach for lesion debridement to treat lumbar tuberculosis.

METHODS

The C-reactive protein (CRP) level, erythrocyte sedimentation rate (ESR), visual analogue scale (VAS) score, oswestry disability index (ODI) and American Spinal Injury Association (ASIA) grade were recorded and analysed pre- and postoperatively.

RESULTS

The CRP level and ESR returned to normal, and the VAS score and ODI were decreased at 3 mo postoperatively, with significant differences compared with the preoperative values (P < 0.01). Neurological dysfunction was relieved, and the ASIA grade increased, with no adverse events.

CONCLUSION

The multitrack, multianchor point screw fixation technique combined with the contralateral Wiltse approach for debridement is an effective and safe method for the treatment of lumbar tuberculosis.

Biomechanical Analysis of Cortical Bone Trajectory Screw Versus Bone Cement Screw for Fixation in Porcine Spinal Low Bone Mass Model

STUDY DESIGN

A prospective study of in vitro animal.

OBJECTION

To compare the biomechanics of cortical bone trajectory screw (CBT) and bone cement screw (BC) in an isolated porcine spinal low bone mass model.

SUMMARY OF BACKGROUND DATA

The choice of spinal fixation in patients with osteoporosis remains controversial. Is CBT better than BC? Research on this issue is lacking.

METHODS

Ten porcine spines with 3 segments were treated with EDTA decalcification. After 8 weeks, all the models met the criteria of low bone mass. Ten specimens were randomly divided into groups, group was implanted with CBT screw (CBT group) and the other group was implanted with bone cement screw (BC group). The biomechanical material testing machine was used to compare the porcine spine activities of the two groups in flexion, extension, bending, and axial rotation, and then insertional torque, pull-out force, and anti-compression force of the 2 groups were compared. Independent sample t test was used for comparison between groups.

RESULTS

Ten 3 segments of porcine spine models with low bone mass were established, and the bone mineral density of all models was lower than 0.75 g/cm 2 . There is no difference between the CBT and BC groups in flexion, extension, bending, and axial rotation angle, P >0.05. However, there were significant differences between the 2 groups and the control group, with P ＜0.01. The 2 groups significantly differed between the insertional torque ( P =0.03) and the screw pull-out force ( P =0.021). The anti-compression forces between the 2 groups have no significant difference between the two groups ( P =0.946).

CONCLUSIONS

The insertional torque and pull-out force of the CBT were higher than those of the BC in the isolated low bone porcine spine model. The range of motion and anti-compression ability of the model was similar between the 2 fixation methods.

Application of the cortical bone trajectory technique in posterior lumbar fixation

The cortical bone trajectory (CBT) is a novel technique in lumbar fixation and fusion. The unique caudocephalad and medial-lateral screw trajectories endow it with excellent screw purchase for vertebral fixation via a minimally invasive method. The combined use of CBT screws with transforaminal or posterior lumbar interbody fusion can treat a variety of lumbar diseases, including spondylolisthesis or stenosis, and can also be used as a remedy for revision surgery when the pedicle screw fails. CBT has obvious advantages in terms of surgical trauma, postoperative recovery, prevention and treatment of adjacent vertebral disease, and the surgical treatment of obese and osteoporosis patients. However, the concept of CBT internal fixation technology appeared relatively recently; consequently, there are few relevant clinical studies, and the long-term clinical efficacy and related complications have not been reported. Therefore, large sample and prospective studies are needed to further reveal the long-term complications and fusion rate. As a supplement to the traditional pedicle trajectory fixation technique, the CBT technique is a good choice for the treatment of lumbar diseases with accurate screw placement and strict indications and is thus deserving of clinical recommendation.

A Dual-Screw Technique for Vertebral Compression Fractures via Robotic Navigation in the Osteopenic Lumbar Spine: An In-Vitro Biomechanical Analysis

STUDY DESIGN

Biomechanical cadaveric study.

OBJECTIVES

Multi-rod constructs maximize posterior fixation, but most use a single pedicle screw (PS) anchor point to support multiple rods. Robotic navigation allows for insertion of PS and cortical screw (CS) within the same pedicle, providing 4 points of bony fixation per vertebra. Recent studies demonstrated radiographic feasibility for dual-screw constructs for posterior lumbar spinal fixation; however, biomechanical characterization of this technique is lacking.

METHODS

Fourteen cadaveric lumbar specimens (L1-L5) were divided into 2 groups (n = 7): PS, and PS + CS. VCF was simulated at L3. Bilateral posterior screws were placed from L2-L4. Load control (±7.5Nm) testing performed in flexion-extension (FE), lateral bending (LB), axial rotation (AR) to measure ROM of: (1) intact; (2) 2-rod construct; (3) 4-rod construct. Static compression testing of 4-rod construct performed at 5 mm/min to measure failure load, axial stiffness.

RESULTS

Four-rod construct was more rigid than 2-rod in FE (P < .001), LB (P < .001), AR (P < .001). Screw technique had no significant effect on FE (P = .516), LB (P = .477), or AR (P = .452). PS + CS 4-rod construct was significantly more stable than PS group (P = .032). Stiffness of PS + CS group (445.8 ± 79.3 N/mm) was significantly greater (P = .019) than PS (317.8 ± 79.8 N/mm). Similarly, failure load of PS + CS group (1824.9 ± 352.2 N) was significantly greater (P = .001) than PS (913.4 ± 309.8 N).

CONCLUSIONS

Dual-screw, 4-rod construct may be more stable than traditional rod-to-rod connectors, especially in axial rotation. Axial stiffness and ultimate strength of 4-rod, dual-screw construct were significantly greater than rod-to-rod. In this study, 4-rod construct was found to have potential biomechanical benefits of increased strength, stiffness, stability.

Evaluating the contact anatomy and contact bone volume of spinal screws using a novel drilled surface image

Intraoperative navigation systems have been widely applied in spinal fusion surgery to improve the implantation accuracy of spinal screws using orthogonal tomographic and surface-rendering imaging. However, these images contain limited anatomical information and no information on bone volume contact by the implanted screw, which has been proven to affect the stability of implanted screws. This study proposed a novel drilled surface imaging technique that displays anatomical integration properties to calculate the contact bone volume (CBV) of the screws implanted along an implantation trajectory. A cylinder was used to represent the area traversed by the screws, which was manually rotated and translated to a predetermined implantation trajectory according to a vertebra model obtained using computed tomography (CT) image volumes. The drilled surface image was reconstructed by interpolating the CT numbers at the predefined sampling points on the cylinder surface. The anatomical integration property and CBV of the screw implanted along the transpedicular trajectory (TT) and cortical bone trajectory (CBT) were evaluated and compared. The drilled surface image fully revealed the contact anatomical structure of the screw under the trajectories, improving the understanding of the anatomical integration of the screw and surrounding tissues. On average, the CBV of the CBT was 30% greater than that of the TT. The proposed drilled surface image may be applied in preoperative planning and integrated into intraoperative navigation systems to evaluate the anatomical integration and degree of bone contact of the screw implanted along a trajectory.

Cortical bone trajectory screws in the treatment of lumbar degenerative disc disease in patients with osteoporosis

Lumbar degenerative disc disease (DDD) in the elderly population remains a global health problem, especially in patients with osteoporosis. Osteoporosis in the elderly can cause failure of internal fixation. Cortical bone trajectory (CBT) is an effective, safe and minimally invasive technique for the treatment of lumbar DDD in patients with osteoporosis. In this review, we analyzed the anatomy, biomechanics, and advantages of the CBT technique in lumbar DDD and revision surgery. Additionally, the clinical trials and case reports, indications, advancements and limitations of this technique were further discussed and reviewed. Finally, we concluded that the CBT technique can be a practical, effective and safe alternative to traditional pedicle screw fixation, especially in DDD patients with osteoporosis.

Accuracy and Screw Insertion Time of Robotic-Assisted Cortical Bone Trajectory Screw Placement for Posterior Lumbar Interbody Fusion: A Comparison of Early, Middle, and Late Phases

Introduction The purpose of this study was to evaluate robotic-assisted cortical bone trajectory (CBT) screw placement. Early, middle, and late phases of robotic-assisted CBT screw placement were compared for accuracy and screw insertion time by comparing time and accuracy in every phase.  Methods A retrospective review was conducted on the initial 40 patients who underwent spinal fusion using CBT screws in one institution from September 2021 to September 2022 utilizing a spine surgery robot system (Mazor X Stealth Edition, Medtronic Inc., Dublin, Ireland). The inclusion criterion was one- or two-level posterior lumbar interbody fusion (PLIF). Exclusion criteria were 1) patients who underwent posterior-lateral fusion in other segments, 2) patients who underwent additional decompression in other segments, 3) patients who underwent reoperation, and 4) patients with spondylolysis. The deviation of the CBT screw was evaluated on computed tomography (CT) one week after surgery using the Gertzbein-Robbins grade system. The rate of Grade A was considered the perfect accuracy rate, and the rate of penetration of 2 mm or more (Grades C, D, and E) was calculated as the deviation rate. To assess the learning curve, patients were divided into three groups. The first 10 cases were in the early phase group, the subsequent 10 cases were in the middle phase group, and the last 10 cases were in the late phase group. We compared the perfect accuracy rate, deviation rate, operative time, operative time per segment, intraoperative blood loss, registration time, and screw insertion time among the three groups. Results Thirty patients met the criteria. Overall, the perfect accuracy (Grade A) rate of the screw was 95.3% and the deviation rate was 1.4%. The perfect accuracy rate was 90.4% in the early phase, 95.5% in the middle phase, and 100% in the late phase. The deviation rate was 3.8% in the early phase, 0% in the middle phase, and 0% in the late phase, and there was no statistically significant difference between the three groups. Among the three groups, the operative time, the operative time per segment, the intraoperative blood loss, and the registration time were not significantly different. There was no significant difference in the screw insertion time among the three groups, but it decreased with experience (early phase: 156.9 ± 54.7 sec, middle phase: 139.9 ± 41.6 sec, and late phase: 106.4 ± 39.9 sec, p=0.060). The screw insertion time of the late phase tended to be shorter than that of the early phase (p=0.052). Conclusions The deviation rate of robotic-assisted CBT screw placement with one- or two-level PLIF was 1.4%, which was highly accurate. The deviation rate was 3.8% in the early phase, 0% in the middle phase, and 0% in the late phase. Although the deviation rate was low even in the early period, the screw insertion time in the early 10 cases tended to be longer than that in the late 10 cases. After passing the experience of 10 cases, this study concluded that robotic-assisted CBT screw placement was proficient.

Biomechanical investigation of the hybrid modified cortical bone screw–pedicle screw fixation technique: Finite-element analysis

Background

Hybrid fixation techniques including the both modified cortical bone trajectory (MCBT) and traditional trajectory (TT) at the L4 and L5 lumbar segment are firstly proposed by our team. Therefore, the purpose of this study is to evaluate and provide specific biomechanical data of the hybrid fixation techniques including the MCBT and TT.

Methods

Four human cadaveric specimens were from the anatomy laboratory of Xinjiang Medical University. Four finite-element (FE) models of the L4–L5 lumbar spine were generated. For each of them, four implanted models with the following fixations were established: TT-TT (TT screw at the cranial and caudal level), MCBT-MCBT (MCBT screw at the cranial and caudal level), hybrid MCBT-TT (MCBT screw at the cranial level and TT screw at the caudal level), and TT-MCBT (TT screw at the cranial level and MCBT screw at the caudal level). A 400-N compressive load with 7.5 N/m moments was applied to simulate flexion, extension, lateral bending, and rotation, respectively. The range of motion (ROM) of the L4–L5 segment and the posterior fixation, the von Mises stress of the intervertebral disc, and the posterior fixation were compared.

Results

Compared to the TT-TT group, the MCBT-TT showed a significant lower ROM of the L4–L5 segment (p ≤ 0.009), lower ROM of the posterior fixation (p &lt; 0.001), lower intervertebral disc stress (p &lt; 0.001), and lower posterior fixation stress (p ≤ 0.041). TT-MCBT groups showed a significant lower ROM of the L4–L5 segment (p ≤ 0.012), lower ROM of the posterior fixation (p &lt; 0.001), lower intervertebral disc stress (p &lt; 0.001), and lower posterior fixation stress (p ≤ 0.038).

Conclusions

The biomechanical properties of the hybrid MCBT-TT and TT-MCBT techniques at the L4–L5 segment are superior to that of stability MCBT-MCBT and TT-TT techniques, and feasibility needs further cadaveric study to verify.

Historical Note: The Evolution of Cortical Bone Trajectory and Associated Techniques

Cortical bone trajectory (CBT) for posterior fixation with pedicle screws is considered a relatively new alternative trajectory that travels in the medio-lateral direction in the transverse plane and in the caudo-cephalad path in the sagittal plane. Various biomechanical studies have already validated its superior pullout strength and mechanical stability over the traditional trajectory of convergent pedicle screws. Due to the relatively medial starting point of this trajectory, the CBT also poses the clinical advantage of requiring a smaller surgical field of exposure, thus minimizing tissue and muscle injury while reducing operative time and intraoperative blood loss. The evolution of CBT through time has closely been linked to the unwavering philosophy of prioritizing patient outcomes, advancements in neuronavigational technology, and the mounting biomechanical, morphometric, and clinical evidence. In this historical review, we provide a unique perspective on how CBT surgical technique has developed through time, highlighting key milestones and attempting to explain its explosive rise in popularity.

Effects of Revision Rod Position on Spinal Construct Stability in Lumbar Revision Surgery: A Finite Element Study

Revision surgery (RS) is a necessary surgical intervention in clinical practice to treat spinal instrumentation–related symptomatic complications. Three constructs with different configurations have been applied in RS. One distinguishing characteristic of these configurations is that the revision rods connecting previous segments and revision segments are placed alongside, outside, or inside the previous rods at the level of facetectomy. Whether the position of the revision rod could generate mechanical disparities in revision constructs is unknown. The objective of this study was to assess the influence of the revision rod position on the construct after RS. A validated spinal finite element (FE) model was developed to simulate RS after previous instrumented fusion using a modified dual-rod construct (DRCm), satellite-rod construct (SRC), and cortical bone trajectory construct (CBTC). Thereafter, maximum von Mises stress (VMS) on the annulus fibrosus and cages and the ligament force of the interspinous ligament, supraspinous ligament, and ligamentum flavum under a pure moment load and a follower load in six directions were applied to assess the influence of the revision rod position on the revision construct. An approximately identical overall reducing tendency of VMS was observed among the three constructs. The changing tendency of the maximum VMS on the cages placed at L4-L5 was nearly equal among the three constructs. However, the changing tendency of the maximum VMS on the cage placed at L2-L3 was notable, especially in the CBTC under right bending and left axial rotation. The overall changing tendency of the ligament force in the DRCm, SRC, and CBTC was also approximately equal, while the ligament force of the CBTC was found to be significantly greater than that of the DRCm and SRC at L1-L2. The results indicated that the stiffness associated with the CBTC might be lower than that associated with the DRCm and SRC in RS. The results of the present study indicated that the DRCm, SRC, and CBTC could provide sufficient stabilization in RS. The CBTC was a less rigid construct. Rather than the revision rod position, the method of constructing spinal instrumentation played a role in influencing the biomechanics of revision.

Placement of Unilateral Cortical Bone Trajectory Screws in Previously Instrumented Pedicle without Removal of Existing Hardware for Adjacent Segment Disease

Adjacent segment disease (ASD) in the lumbar spine is a possible consequence in segments adjacent to a fusion. As the number of lumbar fusions in the United States increases, the rates of ASD will continue to climb. There are several treatment options for ASD with open decompression and extension of the fusion being common. However, need for exposure and removal of existing instrumentation can lead to increased operative times resulting in increasing blood loss and infection risk. The purpose of this paper is to describe a case report for unilateral cortical trajectory screw instrumentation, allowing for posterior instrumentation without having to remove the existing pedicle screws in the setting of ASD. Our technique can be done with standard c-arm fluoroscopy without the need for navigation.

Cortical bone trajectory fixation in cemented vertebrae in lumbar degenerative disease: A case report

BACKGROUND

Percutaneous vertebroplasty (PVP) has been widely used in osteoporotic vertebral compression fracture (OVCF). Following surgery, the bone cement would be positioned permanently. However, in some cases of lumbar degenerative disease, the cemented vertebrae needs to be fixed after decompression and fusion procedure. It is difficult to implant traditional pedicle screws into the cemented vertebrae because of the bone cement filling. At present, the main treatment strategy is to skip the cemented vertebra and conduct a long segment fixation. This article presents a cortical bone trajectory (CBT) fixation technique for cemented vertebrae.

CASE SUMMARY

PVP involving the L3 and L4 was performed in an 82-year-old man due to OVCF. During the surgery, bone cement leakage occurred, resulting in compression of the root of the right L3 nerve. We performed a partial facetectomy to retrieve the leaked bone cement and to relieve the patient’s neurological symptoms. After 3 mo, the patient developed lumbar disc herniation in L3/4, potentially due to instability caused by the previous surgery. Therefore, it was necessary to perform intervertebral fusion and fixation. It was difficult to implant traditional trajectory pedicle screws in L3 and L4 because of the bone cement filling. Hence, we implanted CBT screws in the L3 and L4 vertebrae. As a result, the patient’s symptoms resolved and he reported satisfaction with the surgery at follow-up after 8 mo.

CONCLUSION

It is feasible to utilize CBT in cemented vertebrae for the treatment of lumbar degenerative disease.

Minimally Invasive Robot-Guided Dual Cortical Bone Trajectory for Adjacent Segment Disease

Here we present a novel application of cortical bone trajectory (CBT) fixation utilizing robotic guidance in a previously instrumented spine with a traditional pedicle screw (PS), obviating the need for a larger posterior incision, reducing the risk of infection, muscular dissection, and likely decreasing hospital length of stay.

A 60-year-old woman with prior left L3-L4 extreme lateral interbody fusion and unilateral percutaneous PS placed at L3 to L5 presented with progressive bilateral lower-extremity pain and diminished sensation in the S1 dermatome secondary to adjacent segment disease (ASD). The patient underwent an L5-S1 anterior lumbar interbody fusion for indirect decompression and restoration of segmental lordosis. After the first stage was completed, she was turned prone for posterior percutaneous instrumentation. Given prior instrumentation at L3-L5 on the left side, a robot planning software was used to plan a cortical bone screw on the left L5 pedicle. A left S1 PS was then planned with the screw head aligning with the left L5 cortical bone screw. Instrumentation was then placed percutaneously using the robot bilaterally without issue. Intraoperative fluoroscopic imaging demonstrated accurate placement of PS, and postoperative computed tomography demonstrated the excellent positioning of all PSs.

This report is the first documented case of a robotically placed CBT screw placed in the same pedicle as a prior traditional PS for ASD. This method expands the surgical options for ASD to include robotic percutaneous placement of posterior instrumentation at the same level as previous instrumentation.

A Minimally Invasive Technique Using Cortical Bone Trajectory Screws Assisted by 3D-Printed Navigation Templates in Lumbar Adjacent Segment Degeneration

Purpose

Revision surgery for adjacent segment degeneration (ASD) commonly requires exposing and removing the original fixation. To minimize trauma and to reduce the operation time and blood loss, we introduced a minimally invasive lumbar revision technique using cortical bone trajectory (CBT) screws assisted by three-dimensional (3D)-printed navigation templates.

Methods

From April 2017 to October 2019, 18 patients with ASD underwent revision surgery with CBT screws assisted by 3D-printed templates in our hospital. All surgical data, including the operation time, blood loss, and incision length, were recorded. We evaluated the clinical efficacy using the visual analog scale (VAS), the Oswestry Disability Index (ODI), and the Japanese Orthopedic Association (JOA) score. X-ray and computed tomography (CT) scans were used to evaluate the stability of CBT screw fixation, the accuracy of screws, and the fusion rate.

Results

The mean follow-up was 22.4±4.7 months (12–31 months). The VAS, ODI, and JOA scores were analyzed by SPSS 21.0 and showed significant improvement at 2 weeks and the last follow-up compared with preoperative data (P<0.05). Seventy-six CBT screws were inserted with navigation templates; 2 screws were Grade B, and the other screws were Grade 0 or A. Changes in intervertebral height showed good stability of CBT screw fixation (P>0.05). All the patients exhibited satisfactory fusion results.

Conclusion

Revision surgery for ASD with CBT screws assisted by 3D-printed navigation templates has satisfactory clinical efficacy with the advantages of a short operation time, a small incision, and less blood loss.

Feasibility of cortical bone trajectory screws for bridging fixation in revision surgery for lumbar adjacent segment degeneration

BACKGROUND

To investigate the feasibility of using cortical bone trajectory (CBT) screws for bridging fixation in revision surgery for lumbar adjacent segment degeneration and to provide a reference for clinical practice.

METHODS

Computed tomography scans of the lumbar spines of 36 patients in our hospital were used. Sixteen males and 20 females with an average age of 65.5 ± 10.5 years (range: 46 to 83 years) were included. Three-dimensional reconstruction was performed using computer software. Screws with appropriate sizes were selected for the L1 to L5 vertebral segments, and traditional pedicle screws were placed using the standard method. After completing screw placement, simulated placement of CBT screws was performed separately. No overlap occurred between the two screws in the process of CBT screw placement, and the placement point and direction were adjusted until screw placement completion. After all screw placement simulations were complete, according to the contact area of the cortical bone of the screw trajectory and the screw puncture position and distance through the trajectory, the screw placement results were categorized as excellent, good, general, and failure. Excellent and good ratings were considered successful, while a general rating was regarded as acceptable. Then, the success rate and acceptable rate of each segment of the lumbar spine were calculated.

RESULTS

Three hundred and sixty screw placement simulations were performed in lumbar pedicles, and 72 CBT screws were implanted in each vertebral body of the lumbar spine. The success rates in the L1 to L5 segments were 73.6%, 80.6%, 83.3%, 88.9%, and 77.8%, respectively, and the acceptable rates were 91.7%, 97.2%, 97.2%, 100%, and 91.7%, respectively. The overall success rate and acceptable rate of CBT screw placement in the lumbar spine were 80.8% and 95.6%, respectively.

CONCLUSION

CBT screws are feasible for bridging fixation in lumbar adjacent segment degeneration revision surgery, and the accuracy of screw placement in different lumbar vertebrae varies.

Fluoroscopic versus CT-guided cortical bone trajectory pedicle screw fixation: Comparing trajectory related complications

Cortical bone trajectory (CBT) pedicle screw fixation is an emerging technique for treatment of degenerative spine disease which requires either intraoperative fluoroscopy or intraoperative CT guidance (iCT). To date, there has been no direct comparison of these two navigation modalities; here we compare fluoroscopic versus iCT navigation for CBT pedicle screw fixation. We retrospectively reviewed all patients who underwent CBT screw fixation with either fluoroscopic or iCT guidance for lumbar degenerative disease by the senior author. Trajectory-related complications such as medial or lateral breach were compared on postoperative CT, in addition to the incidence of trajectory-related dural tear. We also compared general surgical complications such as postoperative infection and decompression related durotomies. Thirty-eight patients (19 fluoroscopic, 19 CT-guided) who underwent placement of 182 cortical screws (88 fluoroscopic, 94 CT-guided) were identified. In terms of trajectory-related complications, the iCT cohort had fewer medial breaches (1/94) compared to the fluoroscopic cohort (6/88) (p = 0.05). Each group had one lateral breach (p = 0.73). There was one case of CSF leak from screw placement in the fluoroscopic cohort, but none in the iCT cohort (p = 0.48). Overall, there were eight trajectory-related complications in the fluoroscopic cohort versus two in the iCT cohort (p = 0.04). Our data suggests statistically significant decreased trajectory-related complications with iCT-guided CBT screw fixation as compared to fluoroscopically guided. In terms of general surgical complications, while we observed increased postoperative infections in our fluoroscopic cohort, there was no statistically significant difference.

Investigation of clinical efficacy of screw fixation with cortical bone trajectory for adjacent segment disease after lumbar interbody fusion

To evaluate the clinical efficacy of screw fixation with cortical bone trajectory for adjacent segment disease after lumbar interbody fusion. A total of 14 patients with adjacent segment disease were enrolled, and a retrospective analysis was performed. All patients experienced posterior lumbar interbody fusion of the affected segments combined with internal fixation of cortical bone trajectory screw. Operation time, intraoperative blood loss, and complications were recorded. Clinical outcomes was evaluated by Visual Analogue Scale, Oswestry disability index, and Japanese Orthopaedic Association score. X-ray and computed tomography and sagittal reconstruction were used to check regularly during the follow-up. Bone graft fusion rate was evaluated by Brantigan classification. Preoperatively, Visual Analogue Scale, Oswestry Disability Index, and Japanese Orthopaedic Association scores were 7.0 ± 1.0, 72.2 ± 3.2, and 11.9 ± 1.3 points, respectively. At the 12th month after surgery, their scores were 1.9 ± 0.7, 28.6 ± 1.2, and 23.7 ± 0.9 points, respectively, which were significantly improved compared with those before surgery, and there were statistical significance in all differences (all p < 0.05). At the 12th month after surgery, X-ray and computed tomography showed there were no complications related to internal fixation, such as breakage and displacement. At the 12th month after surgery, according to the Brantigan classification, 10 patients were classified as Grade E, 3 as Grade D, and 1 as Grade C, with a fusion rate of 92.9%. At the final follow-up, clinical outcomes were assessed by the Stauffer-Coventry criteria: there were 10 patients with excellent outcomes, 1 with good outcomes, 3 with fair outcomes, and 0 with poor outcomes, with an excellent and good rate of 78.6%. The clinical outcomes of posterior lumbar interbody fusion combine with cortical bone trajectory screw for adjacent segment disease without removing the previous internal fixator were satisfactory, but further clinical researches were still required to explore its long-term outcome.

Anatomical study of the ideal cortical bone trajectory in the lumbar spine

BACKGROUND

To explore the ideal trajectory of lumbar cortical bone trajectory screws and provide the optimal placement scheme in clinical applications.

METHODS

Lumbar computed tomography (CT) data of 40 patients in our hospital were selected, and the cortical vertebral bone contour model was reconstructed in three dimensions (3D). Depending on the different regions of the screw through the entrance and exit of the pedicle, 9 trajectories were obtained through combinational design: T-Aa, T-Ab, T-Ac, T-Ba, T-Bb, T-Bc, T-Ca, T-Cb, and T-Cc. Cortical bone trajectory (CBT) screws with appropriate diameters were selected to simulate screw placement and measure the parameters corresponding to each trajectory (screw path diameter, screw trajectory length, cephalad angle, and lateral angle), and then determine the optimal screw according to the screw parameters and screw safety. Then, 23 patients in our hospital were selected, and the navigation template was designed based on the ideal trajectory before operation, CBT screws were placed during the operation to further verify the safety and feasibility of the ideal trajectory.

RESULTS

T-Bc and T-Bb are the ideal screw trajectories for L1-L2 and L3-L5, respectively. The screw placement point is located at the intersection of the inner 1/3 vertical line of the superior facet joint and the bottom 1/3 horizontal line of the outer crest of the vertebral lamina (i.e., 2-4 mm inward at the bottom 1/3 of the outer crest of the vertebral lamina). CBT screws were successfully placed based on the ideal screw trajectory in clinical practice. During the operation or the follow-up period, there were no adverse events.

CONCLUSION

CBT screw placement based on the ideal screw trajectory is a safe and reliable method for achieving effective fixation and satisfactory postoperative effects.

Individual Navigation Templates for Subcortical Screw Placement in Lumbar Spine

Subcortical screw placement is currently performed using frontal view fluoroscopy or intraoperative O-arm navigation system. The emergence of a novel technique for spinal navigation based on individual navigation templates created using 3D printing technology determines the need to study their safety and effectiveness in subcortical implantation.

The aim of the study was to evaluate and compare the efficacy of subcortical implantation of pedicle screws in the lumbar spine using individual navigation templates versus intraoperative fluoroscopy.

Guidelines for cortical screw versus pedicle screw selection from a fatigued decompressive lumbar laminectomy model show similar stability and less bone mineral density dependency

BACKGROUND

Traditional pedicle screws are the gold standard for lumbar spine fixation; however, cortical screws along the midline cortical bone trajectory may be advantageous when lumbar decompression is required. While biomechanic investigation of both techniques exists, cortical screw performance in a multi-level lumbar laminectomy and fusion model is unknown. Furthermore, longer-term viability of cortical screws following cyclic fatigue has not been investigated.

METHODS

Fourteen human specimens (L1-S1) were divided into cortical and pedicle screw treatment groups. Motion was captured for the following conditions: intact, bilateral posterior fixation (L3-L5), fixation with laminectomy at L3-L5, fixation with laminectomy and transforaminal lumbar interbody fusion at L3-L5 both prior to, and following, simulated in vivo fatigue. Following fatigue, screw pullout force was collected and "effective shear stress" [pullout force/screw surface area] (N/mm²) was calculated; comparisons and correlations were performed.

FINDINGS

In flexion-extension and lateral bending, all operative constructs significantly reduced motion compared to intact (P < 0.05), regardless of pedicle or cortical screws; only posterior fixation with and without laminectomy significantly reduced motion in axial rotation (P < 0.05). Pedicle screws significantly increased average pullout strength (944.2 N vs. 690.2 N, P < 0.05), but not the "effective shear stress" (1.01 N/mm² vs. 1.1 N/mm², P > 0.05).

INTERPRETATION

In a posterior laminectomy and fusion model, cortical screws provided equivalent stability to pedicle screw fixation, yet had significantly lower screw pullout force. No differences in "effective shear stress" warrant further investigation of the effect of screw length/diameter in the aforementioned screw trajectories.

Anatomy and Imaging Studies on Cortical Bone Screw Freehand Placement Applying Anatomical Targeting Technology

OBJECTIVES

A series of constant anatomical structures were used as guide targets for screw placement to improve the accuracy of cortical screw placement and reduce surgical injury and fluoroscopy radiation. The most commonly used angles and distances between the cortical bone screw insertion point and the lateral margins of the isthmus were selected as the contents of the questionnaire.

METHODS

A total of 40 physicians were selected to determine the specific values for each angle and distance. Screw placements were performed on four dry and six wet lumbar spine specimens according to the proposed anatomical target guidance technique. A total of 100 cortical bone trajectories were evaluated using X-ray and CT scanning of the specimens to verify the practicability, accuracy, and safety of the anatomical target guidance technique in screw placement.

RESULTS

The average deviation rates for angle and distance determination were 105.5% and 14.33%, respectively, indicating a significant difference between the estimated and actual values from other angles (P < 0.05). Based on visual inspection, probe penetration, X-ray, and CT examination of 100 cortical bone trajectories, the excellent rate of 40 trajectories on four dry specimens was 95%, while that of 60 trajectories on six wet specimens was 88.7%.

CONCLUSION

Use of lumbar constant anatomical structures as targeting guidance could assist cortical bone screw placement and reduce surgical damage.

Risk of pedicle and spinous process violation during cortical bone trajectory screw placement in the lumbar spine

Background

Previous studies have confirmed the feasibility of the cortical bone trajectory (CBT) technique. However, there are few reports on spinous process violation and screw penetration during the screw insertion. The purpose of this study was to evaluate the incidence of spinous process violation and screw penetration through the pedicle during CBT screw insertion.

Methods

Computed tomography (CT) scans with normal lumbar structures were consecutively obtained and three-dimensional (3D) reconstructions of the lumbar spine were created. Bilateral CBT screw placement was simulated on each segment using a screw diameter of 4.5 mm, 5.0 mm, or 5.5 mm. Incidences of these complications were recorded and analyzed.

Results

A total of 90 patients were enrolled. Spinous process violation was observed in 68.3, 53.3, 25.5, 1.7, and 0% from L1 to L5, respectively, using 4.5 mm screws. A significant difference was found among the five segments but this was unconnected to gender or screw diameter. The incidence of screw penetration through the inner wall decreased from L1 to L4; in turn, L1 (16.7–35.5%), L2 (12.7–34.4%), L3 (2.8–23.8%) and L4 (1.1–6.7%). This trend was reversed in L5 (6.7–16.7%). Moreover, screw penetration through the outer wall was rare. The incidence of screw penetration varied with screw size as well as lumbar level, but not with gender.

Conclusions

There are more difficulties of CBT screw fixation in upper lumbar spine. The low rate of screw penetration, using 4.5 mm screws, suggests the safety for CBT fixation in the lumbar spine. Larger screws (5.0 mm or 5.5 mm) are more recommended for use in the lower lumbar spine. Moreover, CBT fixation in L5 deserves greater attention because of the unique morphology of the pedicle.

Ten techniques for improving navigated spinal surgery

With the identification of literature shortfalls on the techniques employed in intraoperative navigated (ION) spinal surgery, we outline a number of measures which have been synthesised into a coherent operative technique. These include positioning, dissection, management of the reference frame, the grip, the angle of attack, the drill, the template, the pedicle screw, the wire, and navigated intrathecal analgesia. Optimizing techniques to improve accuracy allow an overall reduction of the repetition of the surgical steps with its associated productivity benefits including time, cost, radiation, and safety.

Cite this article: Bone Joint J 2020;102-B(3):371–375.

Index episode-of-care propensity-matched comparison of transforaminal lumbar interbody fusion (TLIF) techniques: open traditional TLIF versus midline lumbar interbody fusion (MIDLIF) versus robot-assisted MIDLIF

OBJECTIVE

Posterior fixation with interbody cage placement can be accomplished via numerous techniques. In an attempt to expedite recovery by limiting muscle dissection, midline lumbar interbody fusion (MIDLIF) has been described. More recently, the authors have developed a robot-assisted MIDLIF (RA-MIDLIF) technique. The purpose of this study was to compare the index episode-of-care (iEOC) parameters between patients undergoing traditional open transforaminal lumbar interbody fusion (tTLIF), MIDLIF, and RA-MIDLIF.

METHODS

A retrospective review of a prospective, multisurgeon surgical database was performed. Consecutive patients undergoing 1- or 2-level tTLIF, MIDLIF, or RA-MIDLIF for degenerative lumbar conditions were identified. Patients in each cohort were propensity matched based on age, sex, smoking status, BMI, diagnosis, American Society of Anesthesiologists (ASA) class, and number of levels fused. Index EOC parameters such as length of stay (LOS), estimated blood loss (EBL), operating room (OR) time, and actual, direct hospital costs for the index surgical visit were analyzed.

RESULTS

Of 281 and 249 patients undergoing tTLIF and MIDLIF, respectively, 52 cases in each cohort were successfully propensity matched to the authors' first 55 RA-MIDLIF cases. Consistent with propensity matching, there was no significant difference in age, sex, BMI, diagnosis, ASA class, or levels fused. Spondylolisthesis was the most common indication for surgery in all cohorts. The mean total iEOC was similar across all cohorts. Patients undergoing RA-MIDLIF had a shorter average LOS (1.53 days) than those undergoing either MIDLIF (2.71 days) or tTLIF (3.58 days). Both MIDLIF and RA-MIDLIF were associated with lower EBL and less OR time compared with tTLIF.

CONCLUSIONS

Despite concerns for additional cost and time while introducing navigation or robotic technology, a propensity-matched comparison of the authors' first 52 RA-MIDLIF surgeries with tTLIF and MIDLIF showed promising results for reducing OR time, EBL, and LOS without increasing cost.

Midline lumbar interbody fusion (MIDLIF) with cortical screws: initial experience and learning curve

BACKGROUND

A variety of surgical techniques can be used to achieve lumbar spinal fusion for management of degenerative conditions. Transforaminal lumbar interbody fusion (TLIF) is the most popular technique; however, midline lumbar interbody fusion (MIDLIF) is a valid alternative to the more traditional pedicle screw trajectory with potential advantages. The aim of this study is to evaluate the clinical outcomes from a cohort of patients submitted to MIDLIF in a single hospital during the surgical team's initial learning period.

METHODS

The first 30 consecutive patients who underwent single- or two-level MIDLIF surgery for lumbar degenerative disease were included in this retrospective study. Patients' demographics, surgical data, length of hospitalisation, and perioperative complications were analysed. Preoperative and postoperative radiographic parameters were obtained. Validated questionnaires, Core Outcome Measure Index for the back, Euro-QoL 5-Dimensional Questionnaire, and Oswestry Disability Index, were used for clinical assessment.

RESULTS

Mean surgery time was 278.53 ± 82.16 min and mean hospitalisation time was 6.17 ± 3.51 days. Six patients experienced complications, four of which being dural tears with no consequences, and two required reoperations during the mean follow-up of 25.23 ± 9.74 months. Preoperative and postoperative radiological parameters did not demonstrate significant differences. All clinical parameters significantly improved after surgery (p < 0.001). A complexity score was developed to more accurately compare the different procedures, and it strongly correlated with surgery duration (r = 0.719, p < 0.001). Furthermore, a moderate correlation was found between a developed Duration Index and the patient's order number (r = - 0.539, p = 0.002).

CONCLUSIONS

In our initial experience, MIDLIF showed to be effective in significantly improving the patients' functional status, pain scores, and quality of life. The technique seems safe, with an acceptably low complication rate. Hence, MIDLIF can be considered as a promising alternative to more traditional TLIF and PLIF techniques even at the beginning of the learning curve.

Accuracy of cortical bone trajectory screw placement in midline lumbar fusion (MIDLF) with intraoperative cone beam navigation

Background

Cortical bone trajectory (CBT) screws have been recently described as a method of lumbosacral fixation. These screws are typically inserted under fluoroscopic guidance with a medial-to-lateral trajectory in the axial plane and a caudal-to-cephalad trajectory in the sagittal plane. In an effort to reduce surgeon radiation exposure and improve accuracy, CBT screws may be inserted under navigation with intraoperative cone beam computed tomography (CT). However, the accuracy of CBT screw placement under intraoperative navigation has yet to be assessed in the literature. The purpose of the study was to evaluate the accuracy of CBT screw placement using intraoperative cone beam CT navigation.

Methods

One hundred and thirty-four consecutive patients who underwent CBT fixation with 618 screws under intraoperative navigation were analyzed from May 2016 through May 2018. Screws were placed by one of three senior spine surgeons using the Medtronic O-Arm Stealth Navigation. Screw position and accuracy were assessed on intraoperative and postoperative CT scans using 2D and 3D reconstructions with VitreaCore software.

Results

The majority of surgeries were primary cases (73.1%). The mean age at the time of surgery was 61.5±10.0 years and the majority of patients were female (61.2%). Most patients underwent surgery for a diagnosis of degenerative spondylolisthesis (47.8%) followed by mechanical collapse with foraminal stenosis (22.4%). Ten violations of the vertebral cortex were noted with an average breach distance of 1.0±0.7 mm. Three breaches were lateral (0.5%) and seven were medial (1.1%). The overall navigated screw accuracy rate was 98.3%. The accuracy to within 1 mm of error was 99.2%. There were no intra-operative neurologic, vascular, or visceral complications related to the placement of the CBT screws.

Conclusions

CBT screw fixation under an intraoperative cone beam CT navigated insertion technique is safe and reliable. Despite five breaches greater than 1mm, there were no complications related to the placement of the CBT screws in this series.

Differences in bone mineral density of trajectory between lumbar cortical and traditional pedicle screws

BACKGROUND

Cortical bone trajectory (CBT) has been well-known in spine surgery for obtaining improved fixation while minimizing soft tissue dissection. This study was designed to compare the bone mineral density (BMD) between the CBT and traditional trajectory (TT) by using Hounsfield unit (HU) values and identify the ideal decades of patients and the suitable lumbar segments using this CBT technology from a radiological standpoint.

METHODS

Patients were selected randomly from an institutional database based on age (evenly distributed by a decade of life) and gender. A total of 240 healthy patients had a computed tomography (CT) scan of the chest, abdomen, and pelvis. For each patient, axial slices of every vertebra were cut in two planes: one horizontal to the pedicle representing the plane wherein pedicle screws were inserted using the TT and the other in a caudocranial plane representing the plane wherein pedicle screws were inserted using the CBT. For each trajectory, a region of interest (ROI) was selected within the area wherein the screws were inserted. A CT number (HU values) was then calculated within each ROI to represent bone density.

RESULTS

HU values measured at the ROI of CBT were significantly greater than those of the traditional pedicle screw in all age groups, and the specific value (ratio of the HU values of CBT/the HU values of TT) between CBT and TT was 1.92. A significant difference was observed between male and female. The HU values of CBT and TT of males were generally higher than those of females (males: CBT/TT 1.89 ± 0.45; Females: CBT/TT 1.95 ± 0.47). The specific value in HU values significantly increased with increasing age (p = 0.000) and cauda lumbar level (p = 0.000) in males and females.

CONCLUSION

BMD, as measured by HU values for the ROI of the CBT screw, was significantly greater than that of the traditional pedicle screw, especially in old patients and cauda lumbar segments.

Comparative Finite Element Analysis of Lumbar Cortical Screws and Pedicle Screws in Transforaminal and Posterior Lumbar Interbody Fusion

Objective

Lumbar cortical screw fixation (CSF), rather than pedicle screw fixation (PSF), has recently been attempted in lumbar interbody fusion. The purpose of our study was to evaluate the biomechanical stability of lumbar CSF using a finite element (FE) model.

Methods

A 3-FE model, including the L1 to S1 levels, was designed to evaluate and compare the biomechanical stability of lumbar CSF and PSF in single-level lumbar interbody fusion at L4–5. Cortical or pedicle screws were inserted bilaterally, and posterior lumbar interbody fusion (PLIF) and transforaminal lumbar interbody fusion (TLIF) were modeled at L4–5, respectively. We compared the stability of CSF to that of PSF in these 2 different anatomic variations of PLIF, as well as in TLIF.

Results

Lumbar CSF showed less stability than PSF in PLIF when the midline posterior ligaments were not preserved, but demonstrated similar stability when the ligaments were preserved. The range of motion (ROM) at the treated level in CSF was larger than that observed for PSF, in all PLIF and TLIF models. Furthermore, the ROM in the posterior ligament-sacrificing PLIF with CSF model was larger than the ROM in the posterior ligament-preserving PLIF with CSF or PSF model.

Conclusion

Based on our FE analysis, the stability of CSF is comparable to that of PSF in PLIF and TLIF when the midline posterior ligaments are preserved.

Cortical bone trajectory screws used to save failed traditional trajectory screws in the osteoporotic lumbar spine and vice versa: a human cadaveric biomechanical study

OBJECTIVE

Traditional trajectory (TT) screws are widely used in lumbar fixation. However, they may require revision surgery in some instances, especially in patients with osteoporotic spines. Cortical bone trajectory (CBT) screws may potentially be used to rescue a failed TT screw and vice versa in nonosteoporotic spines. This study aimed to investigate whether a CBT screw can salvage a compromised TT screw in osteoporotic lumbar spines and vice versa.

METHODS

A total of 42 vertebrae from 17 cadaveric lumbar spines were obtained. Bone mineral density was measured, and a CBT screw was randomly inserted into one side of each vertebra. A TT screw was then inserted into the contralateral side. The biomechanical properties of the screws were tested to determine their insertional torque, pullout strength, and fatigue performance. After checking the screws for the failure of each specimen, the failed screw track was salvaged with a screw of the opposite trajectory. The specimen was then subjected to the same mechanical tests, and results were recorded. A repeat pullout test on TT and CBT screws was also performed.

RESULTS

When CBT screws were used to rescue failed TT screws, the original torque increased by 50%, an average of 81% of the pullout strength of the initial TT screws was retained, and the fatigue performance was equal to that of the original screws, which were considerably stronger than the loose TT screws-that is, the TT repeat screws/TT screws were 33% of the pullout strength of the initial TT screws. When the TT screws were used to salvage the compromised CBT screws, the TT screws retained 51% of the original torque and 54% of the original pullout strength, and these screws were still stronger than the loose CBT screws-that is, the loose CBT screws retained 12% pullout strength of the initial CBT screws. Fatigue performance and the ratio of the pullout strength considerably decreased between the CBT rescue screws and the original CBT screws but slightly changed between the TT rescue screws and the original TT screws.

CONCLUSIONS

CBT and TT screws can be applied in a revision technique to salvage each other in osteoporotic lumbar spines. Additionally, CBT and TT screws each retain adequate insertional torque, pullout strength, and fatigue performance when used for revision in osteoporotic lumbar spines.

Comparison of Cortical Bone Trajectory Screw Placement Using the Midline Lumbar Fusion Technique to Traditional Pedicle Screws: A Case-Control Study

Background

Cortical bone trajectory (CBT) screws are an alternative to traditional pedicle screws (PS) for lumbar fixation. The proposed benefits of CBT screws include decreased approach-related morbidity and greater cortical bone contact to prevent screw pullout. Relatively little data is published on this technique. Here, we compare the midline lumbar fusion (MIDLF) approach for CBT screw placement to transforaminal lumbar interbody fusion (TLIF) for traditional PS placement.

Methods

A prospectively maintained institutional database was retrospectively reviewed for all patients undergoing lumbar spinal fusion using CBT screws over the past 5 years. Controls were identified from the same database as patients undergoing lumbar spinal fusion with traditional PS placement and matched based on age, sex, and number of levels fused. Exclusion criteria included prior lumbar instrumentation. The electronic health record was retrospectively reviewed for demographic, perioperative, and postoperative data.

Results

A total of 23 patients who underwent CBT screw placement and 35 controls who received traditional PS were included in the study. The median follow-up time was 52.5 months. The CBT screw group had significantly less mean estimated blood loss than the PS group (186 mL versus 414 mL respectively; P = .008). Both groups experienced significant improvements in preoperative Oswestry Disability Index (ODI) and visual analog scale (VAS) scores for back and leg pain. However, there was no significant difference between the groups in regard to operative time and amount of improvement in VAS pain score or ODI. The CBT group was associated with a significantly shorter mean length of stay (LOS). There were 2 instances of screw pullout in each group.

Conclusions

The MIDLF approach with CBT screw placement is associated with less intraoperative blood loss and shorter LOS than traditional PS placement. There is no difference between the 2 techniques in regard to improvement in pain or disability.

Design and Application of Individualized, 3-Dimensional-Printed Navigation Template for Placing Cortical Bone Trajectory Screws in Middle-Upper Thoracic Spine: Cadaver Research Study

OBJECTIVE

To evaluate the safety and accuracy of use of a 3-dimensional printed navigation template in the placement of a cortical bone trajectory (CBT) screw in the middle-upper thoracic spine.

METHODS

Ten human cadavers were included in the study. Sixty CBT screws were placed on 1 side, using the free-hand technique, and 60 CBT screws were placed on the other side, using the navigation template that was designed and printed using data from 10 cadavers. The safety and accuracy of use of the CBT screws were directly evaluated by radiography and computed tomography.

RESULTS

Computed tomography revealed that 2 and 3 of 60 screws, placed using the navigation template, were broken in the medial or lateral areas and in the superior or inferior pedicle wall, respectively. Furthermore, 8 screws were broken in the medial or lateral areas and 11 screws were broken in the superior or inferior pedicle wall when the free-hand technique was used. Radiography revealed that 3 screws in zone I, 55 screws in zone II, and 2 screws in zone III were placed using the navigation template. Furthermore, 7 screws in zone I, 45 screws in zone II, and 8 screws in zone III were placed using the free-hand technique.

CONCLUSIONS

In this cadaver study, insertion of the CBT screws in the middle-upper thoracic spine with the assistance of the navigation template was safe and convenient.

Endoscope-Assisted Anterior Lumbar Interbody Fusion with Computed Tomography-Guided, Image-Navigated Unilateral Cortical Bone Trajectory Screw Fixation in Managing Adjacent Segment Disease in L5/S1: Technical Note

OBJECTIVE

We sought to describe a novel technique in managing a patient with adjacent segment disease at the L5/S1 level.

METHODS

We performed an endoscope-assisted anterior lumbar interbody fusion with computed tomography-guided, image-navigated unilateral cortical bone trajectory screw fixation to treat L5/S1 intervertebral disk pathology.

RESULTS

Patient was successfully treated by a direct endoscopic decompression through the anterior access, interbody fusion using an anterior lumbar interbody fusion cage, unilateral cortical bone trajectory instrumentation under computed tomography-guided image navigation.

CONCLUSIONS

This minimally invasive technique is effective in terms of decompression and fixation. It could be used as an alternative method to treat patients with L5/S1 adjacent segment disease.

Cortical Trajectory Pedicle Screws for the Fixation of Traumatic Thoracolumbar Fractures

Objective

Cortical bone trajectory pedicle screws (CBT) have a different trajectory compared to traditional pedicle screws (PS) and they may confer biomechanical advantages in some patient populations. We hypothesize that the placement of CBT in traumatic thoracolumbar fractures could be an alternative technique to the traditional utilization of PS.

Methods

Single surgeon, retrospective study was performed at a Level 1 Trauma Center from 2013 to 2017. All patients aged between 18 and 90 years with operative AO classification A, B, and C traumatic thoracolumbar fractures were included. Patients with pathological fractures, active spinal infections, or history of vertebral augmentation were excluded. Age, injury severity score (ISS), AO classification, operative time, estimated blood loss (EBL), length of stay (LOS), and presence of proximal junctional kyphosis (PJK) or construct failure were compared between CBT and PS groups. The PS group was further separated into open reduction internal fixation (ORIF) and minimally invasive spine (MIS) groups. All CBT and ORIF cases were completed via open incisions allowing arthrodesis of the involved lamina and facet joints whereas no arthrodesis was completed in the MIS patients. Choice of technique was at the attending surgeon’s discretion.

Results

The study included 71 patients, out of which 12 received CBT and 59 received PS. Of the 59 PS patients, 39 were ORIF and 20 were MIS. The average operative time was 22.9 minutes less in CBT compared to ORIF (p = 0.24). EBL was 337.50 mL for CBT, 184.33 mL for MIS, and 503.33 mL for ORIF (p = 0.01) demonstrating that MIS technique results in a significantly reduced blood loss. However, EBL was comparable for CBT versus MIS (p > 0.05). ISS was not significantly different between the three groups (p = 0.89). LOS was 4.06 days fewer for CBT patients compared to ORIF patients (p = 0.36). There was one case of construct failure as well as one case of incisional site infection in the PS group, but none were found in the CBT group. Instances of PJK complications were determined by the change in the Cobb angle over time and they were not statistically different between the three groups (p = 0.68).

Conclusions

CBT is noninferior to PS in the fixation of unstable adult traumatic thoracolumbar fractures. With the exception of EBL, CBT was not statistically different compared to MIS and ORIF. This study establishes a precedent to expand the application of this new technique and investigate with larger sample sizes.

Comparative Study of Two Surgical Techniques for Proximal Adjacent Segment Pathology after Posterior Lumbar Interbody Fusion with Pedicle Screws: Fusion Extension using Conventional Pedicle Screw vs Cortical Bone Trajectory-Pedicle Screw (Cortical Screw)

OBJECTIVE

To present a minimally invasive surgical technique using cortical bone trajectory pedicle screws (cortical screws [CS]) for adjacent segment pathology (ASP) after lumbar fusion surgery, and to thoroughly compare postoperative outcomes of surgical techniques with either a CS or conventional pedicle screws (PS) for ASP at a 1-year follow-up.

METHODS

Among 59 patients who underwent surgical treatment for proximal ASP after lumbar fusion surgery, 53 patients who met the study criteria (group A, 31 patients with conventional technique using PS; group B, 22 patients with minimally invasive technique using CS) were enrolled in the study. The primary outcome measure was the fusion rate at 1 year after surgery, and secondary outcome measures included patient satisfaction, clinical outcomes, radiologic outcomes, and surgical outcomes and complications.

RESULTS

Fusion at 1 year postsurgery was achieved by 90% of the patients in group A with PS and 91% of those in group B with CS (P > 0.99). Patient satisfaction at 1 month postsurgery (P = 0.03) and pain intensity within 1 month postsurgery (P = 0.04) were significantly better in group B compared with group A. Regarding surgical outcomes, blood loss was significantly less, operation time and length of hospital stay were significantly shorter, and the incision was significantly shorter n group B than in group A. Other clinical parameters and outcomes were similar in the 2 groups.

CONCLUSIONS

We suggest that a minimally invasive surgical technique using CS for ASP can be a viable alternative to a conventional surgical technique using PS.

Application of Cortical Bone Trajectory Screws in Elderly Patients with Lumbar Spinal Tuberculosis

OBJECTIVE

To investigate the clinical efficacy of cortical bone trajectory (CBT) screws in the treatment of elderly patients with lumbar spinal tuberculosis.

METHODS

A total of 45 elderly patients with lumbar spinal tuberculosis were allocated to 1 groups based on different surgical methods: 22 patients in group A received posterior CBT screw fixation combined with anterior debridement with a small incision and bone grafting, and 23 patients in group B underwent posterior pedicle screw fixation combined with anterior debridement with a small incision and bone grafting. The intraoperative blood loss, postoperative drainage volumes, Cobb angles, visual analogue scale scores, erythrocyte sedimentation rates (ESRs), and Frankel grades before and after surgery were analyzed. The surgical complications and spinal fusion were also assessed.

RESULTS

After a 3-month follow-up, 2 patients in group A and 3 patients in group B experienced anterior psoas muscle abscesses, which were cured by a second surgery. The remaining patients were healed by the first surgery. Spinal fusion after bone graft required 3 to 8 months (average, 4.9 months). There were no significant differences in surgery time, blood loss, drainage volume, and hospital stay between the 2 groups. The visual analogue scale scores, Cobb angles, ESRs, and Frankel grades were significantly improved after surgery in both groups.

CONCLUSION

The CBT screws were not inferior to traditional pedicle screws. The application of CBT- screws fixation combined with anterior debridement with a small incision and bone grafting was an effective and safe method to treat elderly patients with lumbar spinal tuberculosis.

Feasibility and safety of using thoracic and lumbar cortical bone trajectory pedicle screws in spinal constructs in children: technical note

Thoracic and lumbar cortical bone trajectory pedicle screws have been described in adult spine surgery. They have likewise been described in pediatric CT-based morphometric studies; however, clinical experience in the pediatric age group is limited. The authors here describe the use of cortical bone trajectory pedicle screws in posterior instrumented spinal fusions from the upper thoracic to the lumbar spine in 12 children. This dedicated study represents the initial use of cortical screws in pediatric spine surgery. The authors retrospectively reviewed the demographics and procedural data of patients who had undergone posterior instrumented fusion using thoracic, lumbar, and sacral cortical screws in children for the following indications: spondylolysis and/or spondylolisthesis (5 patients), unstable thoracolumbar spine trauma (3 patients), scoliosis (2 patients), and tumor (2 patients). Twelve pediatric patients, ranging in age from 11 to 18 years (mean 15.4 years), underwent posterior instrumented fusion. Seventy-six cortical bone trajectory pedicle screws were placed. There were 33 thoracic screws and 43 lumbar screws. Patients underwent surgery between April 29, 2015, and February 1, 2016. Seven (70%) of 10 patients with available imaging achieved a solid fusion, as assessed by CT. Mean follow-up time was 16.8 months (range 13-22 months). There were no intraoperative complications directly related to the cortical bone trajectory screws. One patient required hardware revision for caudal instrumentation failure and screw-head fracture at 3 months after surgery. Mean surgical time was 277 minutes (range 120-542 minutes). Nine of the 12 patients received either a 12- or 24-mg dose of recombinant human bone morphogenic protein 2. Average estimated blood loss was 283 ml (range 25-1100 ml). In our preliminary experience, the cortical bone trajectory pedicle screw technique seems to be a reasonable alternative to the traditional trajectory pedicle screw placement in children. Cortical screws seem to offer satisfactory clinical and radiographic outcomes, with a low complication profile.

Cortical bone trajectory screws fixation in lumbar adjacent segment disease: A technique note with case series

Lumbar adjacent segment disease after lumbar fusion surgery often requires surgical intervention. However, subsequent surgical treatment often needs to expose and remove all of the previous instruments. This additional surgery leads to significant post-operative pain, muscular fibrosis, poor wound healing and infection, etc. From October 2015 to March 2016, we collected six cases underwent cortical bone trajectory screws fixation with minimal invasive inter-body cage fusion for lumbar adjacent segment disease. Patients in the study all had improvement after surgery without recurrence or instruments failure during follow-up. The technique negates removal of pre-existing instruments and when combined with minimal invasive fusion surgery, the wound length, blood loss and soft tissue damage could be reduced compared with traditional surgery. We introduce the surgical procedures in detail and wish this technique could be an option for spine surgeons who encounter a similar situation.

Systematic review of cortical bone trajectory versus pedicle screw techniques for lumbosacral spine fusion

Fusion of the lumbosacral spine is a common surgical procedure to address a range of spinal pathologies. Fixation in lumbar fusion has traditionally been performed using pedicle screw (PS) augmentation. However, an alternative method of screw insertion via cortical bone trajectory (CBT) has been advocated as a less invasive approach which improves initial fixation and reduces neurovascular injury. There is a paucity of robust clinical evidence to support these claims, particularly in comparison to traditional pedicle screws. This study aims to review the available evidence to assess the merits of the CBT approach. Six electronic databases were searched for original published studies which compared CBT with traditional PS and their findings reviewed. Nine comparative studies were identified through a comprehensive literature search. Studies were classified as retrospective cohort, prospective cohort or case control studies with medium quality as assessed by the GRADE criteria. The available literature is not cohesive regarding outcomes and complications of CBT versus PT procedures. Most studies found no difference in operative time, but reported less blood loss during CBT. Radiological outcomes show no difference in slippage at one year although CBT is associated with greater bone-density compared to PT. Results for post-operative pain are inconclusive.