Clinical outcomes during the learning curve of MIDline Lumbar Fusion (MIDLF®) using the cortical bone trajectory

Minimally invasive fusion surgery for patients with degenerative spondylolisthesis and severe lumbar spinal stenosis: a comparative study between MIDLIF and TLIF

PURPOSE

This study aims to compare midline lumbar interbody fusion (MIDLIF) and minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) for treatment of patients with severe stenosis and lumbar degenerative spondylolisthesis (DS), focusing on dural tears rates, other complications, clinical and radiological outcomes.

METHODS

This cohort study included patients with severe lumbar spinal stenosis (Shizas C or D) and lumbar DS who underwent MIDLIF or MIS-TLIF. Propensity score matching was done and the groups were compared regarding surgery time, length of stay, perioperative complications, clinical results and radiological outcomes, at 1 year of follow-up.

RESULTS

The study included initially 80 patients, and 72 patients after matching, 36 in each group. Six patients had dural tears, four in the MIDLIF group and two in the MIS-TLIF group (p = 0.67). General complication rates and reoperations were not significantly different between the groups. Good or excellent clinical was achieved in 75% of the MIDLIF patients and 72% of the MIS-TLIF patients (p = 0.91). Radiological parameters showed small but statistically significant (p < 0.01) improvements after surgery, particularly in segmental lordosis and lumbar lordosis (2.0° and 1.7°), while pelvic tilt and global tilt decreased (1.6° and 2.6°). These findings were similar for both groups.

CONCLUSION

Our study confirms that MIDLIF is a safe and reliable minimally invasive alternative for lumbar interbody fusion in DS, even in patients with severe stenosis and previous spine surgery. It seems to offer similar results to MIS-TLIF regarding clinical results, radiological outcomes and complications.

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.

The treatment efficacy of cortical bone trajectory (CBT) pedicle screws for lumbar degenerative disease in the Chinese Han population

Purpose

To provide reference data on CBT pedicle screws from CT measurements of L1 to L5 in the Chinese Han population and to assess the treatment efficacy of CBT pedicle screws in cases of lumbar degenerative disease.

Methods

In total, 100 patients were identified from the CT database for CBT morphometric measurement of the lumbar spine. According to sex and age, patients were divided into four groups. The diameter, length, and angle of the vertebral pedicle and trajectory were measured. Then, a total of 36 patients with lumbar degenerative disease were included in this study for clinical and radiographic evaluation. Demographic characteristics, health-related quality of life (HRQOL), and extent of intervertebral disc herniation and spondylolisthesis were evaluated.

Results

The mean diameter and the mean length varied from L1 to L5 in Groups I to IV. The lateral angles ranging from L1 to L5 were 8.9 to 9.2°, 8.7 to 12.2°, 8.7 to 11.2°, and 9.2 to 10.1° in Groups I to IV, respectively. The cephalad angles from L1 to L5 were 23.5 to 28.6°, 24.7 to 26.6°, 25.0 to 28.2°, and 24.7 to 27.9° in Groups I to IV, respectively. In the case series, all patients’ neurological function and HRQOL were significantly improved at the final follow-up (p < 0.0001), and 75% of patients achieved satisfaction.

Conclusions

The morphology of the lumbar vertebral pedicle varied from L1 to L5, and the trajectory was feasible and safe. CBT pedicle screws were effective in treating lumbar degenerative diseases and benefited the patients.

Accuracy and safety of robot-assisted cortical bone trajectory screw placement: a comparison of robot-assisted technique with fluoroscopy-assisted approach

Objective

To compare the safety and accuracy of cortical bone trajectory screw placement between the robot-assisted and fluoroscopy-assisted approaches.

Methods

This retrospective study was conducted between November 2018 and June 2020, including 81 patients who underwent cortical bone trajectory (CBT) surgery for degenerative lumbar spine disease. CBT was performed by the same team of experienced surgeons. The patients were randomly divided into two groups—the fluoroscopy-assisted group (FA, 44 patients) and the robot-assisted group (RA, 37 patients). Robots for orthopedic surgery were used in the robot-assisted group, whereas conventional fluoroscopy-guided screw placement was used in the fluoroscopy-assisted group. The accuracy of screw placement and rate of superior facet joint violation were assessed using postoperative computed tomography (CT). The time of single screw placement, intraoperative blood loss, and radiation exposure to the surgical team were also recorded. The χ² test and Student’s t-test were used to analyze the significance of the variables (P < 0.05).

Results

A total of 376 screws were inserted in 81 patients, including 172 screws in the robot-assisted group and 204 pedicle screws in the fluoroscopy-assisted group. Screw placement accuracy was higher in the RA group (160, 93%) than in the FA group (169, 83%) (P = 0.003). The RA group had a lower violation of the superior facet joint than the FA group. The number of screws reaching grade 0 in the RA group (58, 78%) was more than that in the FA group (56, 64%) (P = 0.041). Screw placement time was longer in the FA group (7.25 ± 0.84 min) than in the RA group (5.58 ± 1.22 min, P < 0.001). The FA group had more intraoperative bleeding (273.41 ± 118.20 ml) than the RA group (248.65 ± 97.53 ml, P = 0.313). The radiation time of the FA group (0.43 ± 0.07 min) was longer than the RA group (0.37 ± 0.10 min, P = 0.001). Furthermore, the overall learning curve tended to decrease.

Conclusions

Robot-assisted screw placement improves screw placement accuracy, shortens screw placement time, effectively improves surgical safety and efficiency, and reduces radiation exposure to the surgical team. In addition, the learning curve of robot-assisted screw placement is smooth and easy to operate.

Biomechanical Evaluation of Cortical Bone Trajectory Fixation with Traditional Pedicle Screw in the Lumbar Spine: A Finite Element Study

Cortical bone trajectory (CBT) is increasingly used in spinal surgery. Although there are many biomechanical studies, the biomechanical effect of CBT in combination with traditional pedicle screws is not detailed. Therefore, the purpose of this study was to investigate the effects of the traditional pedicle screw and CBT screw implantation on the lumbar spine using finite element methods. Based on the combination of the traditional pedicle screw and the CBT system implanted into the lumbar spine, four finite element spinal lumbar models were established. The models were given four different load conditions (flexion, extension, lateral bending, and axial rotation), and the deformation and stress distribution on the finite element model were observed. The results show that there was no significant difference in the structural stability of the lumbar spine model between the traditional pedicle screw system and the CBT system. In addition, CBT may reduce stress on the endplate. Different movements performed by the model may have significant biomechanical effects on the spine and screw system. Clinical spinal surgeons may also consider using the CBT system in revision spinal surgery, which may contribute to smaller wounds.

Clinical and radiological results of treating lumbar spondylosis with cortical bone trajectory screws

The cortical bone trajectory screws technique (CBTT) is a popular minimally invasive spine surgery. Few studies have reported long-term outcomes. We aimed to evaluate the complication profile and long-term follow-up results of patients with lumbar degenerative disease treated with the CBTT.This retrospective analysis included the first 40 consecutive patients that underwent the CBTT. The indication for surgery was critical stenosis of the intervertebral foramen, which required removal of the entire intervertebral joint, on at least 1 side, during decompression.The last follow-up showed minimal clinically important differences in the numerical rating scale of leg pain, the numerical rating scale of back pain, and the Oswestry Disability Index, in 97%, 95%, and 95% of patients, respectively. Thirty-nine patients completed long-term radiological follow-up. Computed tomography demonstrated solid bone union on 47 (92%) operated levels, collapsed union on 2 (4%) levels, nonunion on 1 (2%) level, and 1 (2%) patient was lost to follow-up. Seven patients experienced complications (4 hardware-related). Three patients required 4 revision surgeries.The CBTT effectively achieved spinal fusion; over 90% of patients achieved clinical improvement at a mean follow-up of 4.4 years (range: 3-5.75 years).

Long-Term Outcome After Midline Lumbar Fusion for the Treatment of Lumbar Spine Instability Due to Degenerative Disease

BACKGROUND

Midline lumbar fusion (MIDLF) is one promising new surgical technique that has been developed to minimize perioperative damage to the paravertebral stabilizing musculotendinous system. The aim of this study was to assess long-term clinical and radiological effects of MIDLF.

METHODS

This prospective cohort study evaluated patients who underwent MIDLF for degenerative spinal instability. Clinical and radiological examinations were performed before and after surgery. Perioperative and postoperative complications were recorded. Follow-up was 2 years. P ≤ 0.05 was considered statistically significant.

RESULTS

The study included 64 patients (mean age 58.9 ± 10.7 years; 41 women [64.1%]). The most frequent indication for MIDLF was degenerative spondylolisthesis grade I (28 cases [43.8%]); the prevalent spinal segment to be fused was L4-L5 (35 cases [54.7%]). Mean duration of surgery was 148.2 ± 28.9 minutes. Relief of low back pain and leg pain was significant and stable in the postoperative period as assessed by visual analog scale (P < 0.001). Of patients, 86.9% reported fair, good, or excellent outcomes in terms of pain relief based on MacNab score 2 years after surgery. Patients' level of function in activities of daily living improved significantly based on Oswestry Disability Index score: from 66.8 ± 9.8 before surgery to 33.9 ± 16.5 2 years after surgery (P < 0.001). X-rays and computed tomography at 12 months showed interbody fusion in 46 cases (73.4%), inconclusive results in 13 cases (20.3%), and no fusion in 4 cases (6.3%). No damage to neural or vascular structures and no failure of hardware or screw loosening were recorded.

CONCLUSIONS

MIDLF is a safe, efficient method for surgical treatment of lumbar spine instability. Its limited invasiveness contributes to better preservation of paravertebral muscles and enhanced postoperative spinal stability.

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.

Characterizing the Surgeon Learning Curve in Instrumented Minimally Invasive Spinal Surgery: Does the Evidence Account for Training and Experience? A Systematic Literature Review

STUDY DESIGN

This was a systematic literature review.

OBJECTIVE

The purpose of this systematic literature review was to aggregate all evidence characterizing the learning curve of instrumented minimally invasive surgery (MIS) techniques in spinal surgery and summarize what, if any, consideration has been given to surgeon training and experience.

SUMMARY OF BACKGROUND DATA

MIS techniques have become prevalent in spine surgery given the ability to diminish the intraoperative footprint, translating to quicker patient recovery, and improved long-term outcomes. However, technical demand on the surgeon can be significant, particularly during the procedural adoption (learning curve) phase. Many studies have sought to quantify the duration and severity of these learning curve phases, with the intent to characterize MIS procedural appropriateness and safety. However, while these studies are robust regarding outcome metrics, it is not well understood whether they adequately characterize surgeon training and experience.

METHODS

A systematic literature review was performed in the PubMed and MEDLINE databases in accordance with the PRISMA guidelines. All inclusion articles were screened for statements regarding surgeon experience/training. Statements were further classified by the types of metrics/variables utilized to establish a contextual history of experience/training. Descriptive statistics were reported.

RESULTS

Initial search criteria yielded 458 articles, 12 met final inclusion. Seven articles (58.3%) attempted a summary statement of experience which acknowledged at least one of the following metrics: total years in practice (41.7%), years/number of cases performed using the traditional/gold-standard technique (16.7%), specification of residency/fellowship training (16.7%), use/nonuse of cadaveric or course/lab training (16.7%), and/or design of operating team (8.3%). No articles considered experience as a quantitative variable in their study analyses.

CONCLUSIONS

Spine MIS learning curve studies for instrumented fusion procedures provide inadequate context/characterization of surgeon experience and training. Future efforts leveraging learning curve methodology utilized in other surgical specialties would be beneficial.

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.

Simulation with 3D Neuronavigation for Learning Cortical Bone Trajectory Screw Placement

BACKGROUND AND OBJECTIVE

 Learning a new technique in neurosurgery is a big challenge especially for trainees. In recent years, simulations and simulators got into the focus as a teaching tool. Our objective is to propose a simulator for placement of cortical bone trajectory (CBT) screws to improve results and reduce complications.

METHODS

 We have created a platform consisting of a sawbone navigated with a 3D fluoroscope to familiarize our trainees and consultants with CBT technique and later implement it in our department. Objective Structured Assessment of Technical Skills (OSATS) and Physician Performance Diagnostic Inventory Scale (PPDI) were obtained before and after the use of the simulator by the five participants in the study. Patients who were operated on after the implementation of the technique were retrospectively reviewed.

RESULTS

 During the simulation, there were 4 cases of pedicle breach out of 24 screws inserted (16.6%). After having completed simulation, participants demonstrated an improvement in OSATS and PPDI (p = 0.039 and 0.042, respectively). Analyzing the answers to the different items of the tests, participants mainly improved in the knowledge (p = 0.038), the performance (p = 0.041), and understanding of the procedure (p = 0.034). In our retrospective series, eight patients with L4-L5 instability were operated on using CBT, improving their Oswestry Disability Index (ODI) score (preoperative ODI 58.5 [SD 16.7] vs. postoperative ODI 31 [SD 13.4]; p = 0.028). One intraoperative complication due to a dural tear was observed. In the follow-up, we found a case of pseudoarthrosis and a facet joint violation, but no other complications related to misplacement, pedicle fracture, or hardware failure.

CONCLUSION

 The simulation we have created is useful for the implementation of CBT. In our study, consultants and trainees have valued very positively the learning obtained using the system. Moreover, simulation facilitated the learning of the technique and the understanding of surgical anatomy. We hope that simulation helps reducing complications in the future.

Cortical bone trajectory technique's outcomes and procedures for posterior lumbar fusion: A retrospective study

Cortical Bone Trajectory screws allow a limited soft tissue dissection with mechanical properties comparable to traditional pedicle screws. However, clinical results are still reported on limited samples. The study aimed to evaluate perioperative and mid-term follow up outcomes, clinical results and complications in 238 consecutive patients underwent CBT fusion for degenerative lumbosacral disease. Pre- and intraoperative data, clinical outcomes and complications were collected. The patients were stratified in three groups. The original technique was performed in the first 43 cases without a preoperative CT scan planning. The second group includes the patients who underwent preoperative CT scan for entry point and screw trajectory planning (158 patients). Surgical procedures in the last group were performed with patient-matched 3D printed guide (37 patients). The accuracy in screws positioning was evaluated on postoperative CT scan. The mean follow-up was 32.3 months. Mean ODI and VAS index improved with statistical significance. Mean procedural time was 187, 142 and 124 min in the three subgroups. The total amount of recorded complications was 4.2% (16.3%, 3.8% and 0.0% respectively). Screws entirely within the cortex of the pedicle were 78.9%, 90.5% and 93.9% in the three groups. Fusion was obtained in 92.4% of cases. The CBT technique is a safe procedure, especially with an accurate preoperative CT scan-based planning. This seems more evident with the 3D template patient-matched guide. More studies are needed to directly compare traditional pedicle screws and CBT screws on long-term outcomes.

Advancements in osteoporotic spine fixation

With the global rise in the population of elderly along with other risk factors, spine surgeons have to encounter osteoporotic spine more often. Osteoporotic spine, however, causes problems in management, particularly where instrumentation is involved, resulting in screw loosening, pull out, pseudoarthroses or adjacent segment kyphosis. Osteoporosis alters the bio mechanics at the bone implant interface resulting in various degrees of fixation failure. Various advancements have been made in this field to deal with such issues in addition to modification of basic surgical techniques such as increasing the diameter and length of the screw, smaller pilot hole, under tapping, longer constructs, supplemental anterior fixation, sublaminar wires or laminar hooks, use of transverse connectors and triangulation techniques, among others. They include novel surgical techniques such as cortical bone trajectory, superior cortical trajectory, double screw technique, cross trajectory technique, bicortical screw technique or prophylactic vertebroplasty. Advances in the screw design include expandable screws, fenestrated screws, conical screws and coated screws. In addition to PMMA cement augmentation, other biodegradable cements have been introduced to mitigate the side effects of PMMA such as calcium phosphate, calcium apatite and hydroxyapatite. Pharmacotherapy with teriparatide can aid fusion and lower the rate of pedicle screw loosening. Many of these strategies have only bio mechanical evidence and require well designed clinical trials to establish their clinical efficacy. Though no single technique is fool proof, little modifications in the existing techniques or utilizing a combination of techniques without adding to the cost of the surgery may help to achieve a near-ideal result. Surgeons have to equip their armamentarium with all the recent advances, and should be open to novel thoughts and techniques.

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.

Early Clinical Outcome of Lumbar Spinal Fixation With Cortical Bone Trajectory Pedicle Screws in Patients With Osteoporosis With Degenerative Disease

This cohort study aimed to elucidate early surgical outcomes after midline lumbar fusion (MidLIF) with cortical bone trajectory (CBT) screw fixation compared with transforaminal lumbar interbody fusion (TLIF) using traditional pedicle screw (TPS) fixation for lumbar degenerative disease (LDD) in patients with osteoporosis. The authors randomly assigned 70 patients with osteoporosis who had LDD at 1 or 2 adjacent vertebral levels to undergo either MidLIF with CBT (CBT group) or TLIF with TPS fixation (TPS group) from February 2015 to March 2016. Pre- and postoperative lumbar Japanese Orthopaedic Association (JOA) scale scores were assessed and radiographic measurements on dynamic plain radiographs and computed tomography images were analyzed. The final data analysis included 31 patients in the CBT group (mean age, 73.42±6.74 years; t-score, -2.94±0.75) and 32 patients in the TPS group (mean age, 74.84±5.37 years; t-score, -2.92±0.66). Mean JOA score improved significantly in both groups, although no intragroup differences of JOA score improvement were found at the latest follow-up evaluation (P>.05). In addition, significantly higher rates of screw loosening (28.13% vs 6.5%, P=.03) and the amount of subsidence (3.01±0.52 vs 2.49±0.45 mm, P=.02) were found in the TPS group. Rate of radiographic fusion of both groups showed no statistical difference. Both groups of patients achieved a similar rate of radiographic fusion at the 1.5-year follow-up and experienced similar intra- or postoperative complications and postoperative recovery. The MidLIF with CBT screw fixation for short-level lumbar fusion in patients with osteoporosis provided improvement of clinical symptoms comparable to that of TLIF using traditional TPS fixation. In addition, statistically significant lumbar stability was found in the CBT group compared with the TPS group. [Orthopedics. 2019; 42(5):e465-e471.].

Comparison of outcomes between cortical screws and traditional pedicle screws for lumbar interbody fusion: a systematic review and meta-analysis

Purpose

The clinical outcomes of using a cortical screw (CS) for lumbar interbody fusion were evaluated by comparison with conventional pedicle screw (PS) fixation.

Methods

All of the comparative studies published in the PubMed, Cochrane Library, MEDLINE, Web of Science, and EMBASE databases recently as 18 March 2019, were included. All outcomes were analyzed by using Review Manager 5.3.

Results

Twelve studies were included with a total of 835 patients, and two of the studies were randomized controlled trials. The outcomes of the meta-analysis indicated that the use of CS fixation for lumbar interbody fusion was better than conventional PS fixation in regard to operating time (p = 0.02), intraoperative blood loss (p < 0.00001), length of stay (p = 0.02), incidence of complications (p = 0.02), adjacent segmental disease (ASD) incidence (p = 0.03), and Oswestry Disability Index (ODI) (p = 0.03). However, there were no statistically significant differences in the back and leg pain visual analog scale (VAS), Japanese Orthopaedic Association (JOA) scale, and intervertebral fusion rate (all p > 0.05) between the CS fixation group and the PS fixation group.

Conclusions

Based on this systematic review and meta-analysis, our outcomes indicated that both CS and conventional PS can result in good postoperative outcomes in lumbar interbody fusion. No significant differences were found in the back and leg pain VAS, JOA scale, and intervertebral fusion rate. However, CS fixation is superior to PS fixation in the following measures: operating time, intraoperative blood loss, length of stay, incidence of complications, ASD incidence, and ODI.

Trial registration

PROSPERO registration number is CRD 42019132226.

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.

Cortical pedicle screw placement in lumbar spinal surgery with a patient-matched targeting guide: A cadaveric study

BACKGROUND

Cortical pedicle screw placement is an attractive technique in terms of both fixation strength and less invasiveness. However, to insert the screw with penetrating cortical bone on the ideal trajectory is technically demanding. The use of three-dimensional (3D) patient-matched guides may facilitate the use of this technique.

PURPOSE

To examine the accuracy of cortical screw placement using a patient-matched targeting guide with a cadaveric study assessing the accuracy.

METHODS

The 3D planning of the pedicle screw placement, including the location at which the screw would pass through the center of the pedicle, sagittal/transverse trajectory (angle), length, and diameter, was developed using 3D CAD design software. Three-dimensional guides based on the preoperative planning were created for three cadaveric specimens (L1 to S1, 36 pedicles). Screws (n = 18) and pins (n = 18) were placed using K-wire or drill-based guides, without X-ray exposure. Actual positioning was compared to the preoperative plan by superimposing the inserted screws/pins based on postoperative CT. The placement accuracy was graded based on the degree of perforation of the pedicle by the pedicle screw or pin using an acceptance criterion (no perforation; Grade A, 0-2 mm; Grade B, 2-4 mm; and Grade C, >4 mm). The mean deviation between the planned and inserted screw positions on the coronal plane at the midpoint of the pedicle was compared to the accuracy of screw guide for traditional pedicle screw trajectory (0.70 mm).

RESULTS

Of 35 evaluated screws and pins, 32 (91.4%) were inserted completely inside the pedicle. All pedicle perforation was within 2 mm. The mean deviation from the plan at the midpoint of pedicle was 0.66 mm; thus, the accuracy was within the predefined criteria.

CONCLUSIONS

Cortical pedicle screw placement using 3D-patient matched guides is accurate. Further clinical studies are required to confirm the radiographic and clinical effects.

Comparative Study of Cortical Bone Trajectory-Pedicle Screw (Cortical Screw) Versus Conventional Pedicle Screw in Single-Level Posterior Lumbar Interbody Fusion: A 2-Year Post Hoc Analysis from Prospectively Randomized Data

OBJECTIVE

The aim of this study was to report 2-year follow-up outcomes of posterior lumbar interbody fusion (PLIF) with cortical bone trajectory-pedicle screw (CS), in terms of fusion rates, clinical outcomes, surgical outcomes, and complications, and to compare these outcomes with outcomes for PLIF with conventional pedicle screw (PS).

METHODS

We enrolled 79 patients and randomly assigned them to 2 groups (group A with PS, 39 patients; group B with CS, 40 patients), and finally 37 and 35 in group A and B were analyzed in the study. The primary outcome measure was the fusion rate, evaluated by dynamic radiographs and computed tomography scans. Secondary outcome measures included 1) patient satisfaction; 2) clinical outcomes measured with pain intensity using a visual analog scale, the Oswestry Disability Index, and 12-Item Short Form Health Survey; 3) radiologic outcomes; and 4) complications.

RESULTS

At 2-year follow-up, the fusion rate was comparable between the PS and CS groups (35 of 37 patients in the PS group; 32 of 35 patients in the CS group; P > 0.99). The patient satisfaction rate at the 1-month follow-up was significantly greater in the CS group than in the PS group (P = 0.03); however, there was no significant difference between the groups at the 1-year and 2-year follow-ups. Clinical outcomes, radiologic outcomes, and related complications revealed no significant differences in both groups within 2 years postoperatively.

CONCLUSIONS

We suggest that CS in single-level PLIF may be an alternative to PS.

Lumbar pedicle screw fixation with cortical bone trajectory: A review from anatomical and biomechanical standpoints

Over the past few decades, many attempts to enhance the integrity of the bone-screw interface have been made to prevent pedicle screw failure and to achieve a better clinical outcome when treating a variety of spinal disorders. Cortical bone trajectory (CBT) has been developed as an alternative to the traditional lumbar pedicle screw trajectory. Contrary to the traditional trajectory, which follows the anatomical axis of the pedicle from a lateral starting point, CBT starts at the lateral part of the pars interarticularis and follows a mediolateral and caudocranial screw path through the pedicle. By markedly altering the screw path, CBT has the advantage of achieving a higher level of thread contact with the cortical bone from the dorsal entry point to the vertebral body. Biomechanical studies demonstrated the superior anchoring ability of CBT over the traditional trajectory, even with a shorter and smaller CBT screw. Furthermore, screw insertion from a more medial and caudal starting point requires less exposure and minimizes the procedure-related morbidity, such as reducing damage to the paraspinal muscles, avoiding iatrogenic injury to the cranial facet joint, and maintaining neurovascular supply to the fused segment. Thus, the features of CBT, which enhance screw fixation with limited surgical exposure, have attracted the interest of surgeons as a new minimally invasive method for spinal fusion. The purpose of this study was: 1) to identify the features of the CBT technique by reviewing previous anatomical and biomechanical literature, and 2) to describe its clinical application with a focus on the indications, limitations, surgical technique, and clinical evidence.

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.

Midline lumbar fusion with cortical bone trajectory as first line treatment in a selected series of patients with lumbar instability

BACKGROUND

The aim of the present study was to proof that for certain complex spinal conditions, midline lumbar fusion (MIDLF) technique is very convenient in terms of length of hospitalization, functional recovery and pain relief and time to back to work.

METHODS

MIDLF indications were set for patients with not more than 3 unstable levels, presence of osteoporosis (alternative to cemented screws), or cardiomyopathy with anticoagulation with or without spinal stenosis, and or discopathy. Surgical difficulties, operative time, hemoglobin loss and postoperative 45 days, 6 months and one-year follow-up data are shown.

RESULTS

In one-year period MIDLF was applied for 9 patients. For all cases motor deficits improved, pain decreased from a high VAS Score to VAS 1. No complications were seen so far. In one case small pedicles prevented the use of MIDLF technique.

CONCLUSIONS

Operative time, acceptable hemoglobin loss, short length of stay and encouraging follow-up result indicate that this technique is a valid option to improve patient's quality of life where osteoporosis makes traditional transpedicular screws less stable or where the surgeon has the need to reduce intraoperative blood loss or has to work in a deep surgical field.