Analysis of reasons for medical malpractice litigation due to laminectomy.

OBJECTIVE: The aim of this study was to identify the incidence and characteristics of malpractice lawsuits pertaining to laminectomy performed either as a stand-alone operation or concurrent with another procedure by querying the Westlaw Edge and VerdictSearch databases. Malpractice claims analysis is performed by several medical specialties to provide insight into patient values, methods to improve quality of care, and risk factors for litigation pertaining to specific procedures or treatments. METHODS: Westlaw and VerdictSearch were queried using the keywords "laminectomy" and "spine." Claims were reviewed, with the inclusion criteria defined as a case filed between 2000 and 2022 that involved the plaintiff's basis of litigation resting on a claim of medical malpractice due to laminectomy. Additional collected data included the case date, verdict ruling, state or federal location of the filed claim, sustained injuries, and payment or settlement amount. RESULTS: After review of 4732 cases, 201 were identified as malpractice claims due to laminectomy. The most common reasons for litigation were delayed or denied treatment (n = 106), procedural errors (n = 38), inadequate management of postlaminectomy syndrome (n = 26), and incorrect procedural selection (n = 14). Regarding the verdict ruling, 47.3% (n = 95) of cases ruled in favor of the defendant, 9.0% (n = 18) resulted in a mixed ruling, 15.9% (n = 32) ruled in favor of the plaintiff, and 9.5% (n = 19) were resolved with an out-of-court settlement. An average payment of $4,530,277 resulted from the cases that ruled in favor of the plaintiff, while out-of-court settlements yielded an average payment of $1,193,146. CONCLUSIONS: This study suggests that there are several well-documented risk factors for malpractice claims attributed to laminectomy. The study findings suggest that prompt and accurate diagnosis, coordination of care, timely referral for surgical intervention, and understanding of the indications versus limitations of conservative therapy may help to mitigate the risk of litigation associated with laminectomy.

Opportunistic assessment of bone density in patients with adolescent idiopathic scoliosis using MRI-based vertebral bone quality.

Patients with Adolescent Idiopathic Scoliosis (AIS) have increased prevalence of lower bone mineral density (BMD) compared to healthy adolescents. Our goal was to compare bone density in patients with AIS and a nonaffected control group using an MRI-based vertebral bone quality (VBQ) score. We reviewed 50 consecutive lumbar MRIs of patients with AIS and of 50 nonaffected controls that were matched for age and sex. The VBQ score was calculated and compared between the groups. The VBQ score for the AIS group was 2.5 (SD 0.4) and for the control group 2.1 (SD 0.3) (p < 0.001). Multiple linear regression analyses were performed for control of confounding from body weight, body height, corrected BMI, and Cobb angle. Besides the diagnosis of AIS, there was no variable that was independently associated with the VBQ score. This is the first study to evaluate bone density in pediatric patients with AIS. We found a significant difference in the VBQ-score between patients with AIS and nonaffected controls matched for sex, age, and race. MRI can be used to assess the bone quality in patients with adolescent idiopathic scoliosis.

Effect of Preoperative Opiate Use on Outcomes After Posterior Lumbar Surgery.

Introduction The prescription opioid epidemic and widespread use of narcotic medications have introduced new challenges when treating patients undergoing spine surgery. Given the ubiquity of preoperative opioid consumption amongst patients undergoing spine surgery, further research is needed to characterize perioperative risks. Our goal is to compare outcomes following primary lumbar decompression, instrumentation, and fusion based on preoperative opioid prescriptions. Methods Patients older than 18 years of age who underwent a primary one- to two-level lumbar decompression, instrumentation, and fusion were included in the study. Patients with known malignancy, surgery involving three or more lumbar levels, current or previous use of neuromodulation, revision surgery, anterior or far lateral interbody fusions, acute fractures, or other concurrent procedures were excluded. Patients were divided into chronic opioid therapy (COT; over six months), acute opioid therapy (AOT; up to six months), and opiate-naïve groups. Opioid prescriptions, demographics, smoking status, readmission rates within one year, and reoperation rates within two years were recorded based on electronic medical record documentation. Results Out of 416 patients identified, 114 patients met the inclusion criteria. Thirty-eight patients (33.3%) were on COT, 38 patients (33.3%) were on AOT, and 38 patients (33.3%) were opioid naïve preoperatively. Readmission rates within one year for COT, AOT, and opioid naïve patients were 34.2%, 26.3%, and 10.5%, respectively (p=0.047). Reoperation rates within two years for COT, AOT, and opioid naïve patients were 34.2%, 15.8%, and 13.2%, respectively (p=0.049). We also found current or former smokers were more likely to be on AOT or COT than never smokers (78.4% vs. 57.1%; p=0.017).  Conclusion Long-term opiate use is associated with an increased risk for readmission within one year and revision within two years. Physicians should discuss the increased risks of readmission and revision surgery associated with lumbar decompression and fusion seen in patients on preoperative opioid therapy.

Allograft Versus Autograft in Anterior Cervical Discectomy and Fusion: A Propensity-Matched Analysis.

Objective To compare the 30-day complication rate associated with allograft versus autograft in anterior cervical discectomy and fusion (ACDF) and to determine preoperative factors that may influence complication rate. Methods The American College of Surgeons National Surgical Quality Improvement Program database was retrospectively queried from 2014 to 2017 for all procedures with CPT codes for ACDF (22551). Patients undergoing ACDF with either autograft or allograft were matched by propensity scores based on age, sex, body mass index, and comorbidities. The incidence of adverse events in the 30-day postoperative period was compared. Results A total of 21,588 patients met the inclusion and exclusion criteria. Following the 10:1 propensity match, 17,061 remained in the study (1,551 autograft and 15,510 allograft). The overall adverse event rate was 3.18%; 3.48% for autograft and 3.15% for allograft (P=0.494). Autograft had a significantly greater incidence of extended length of stay (>2 d) (LOS) (48.9% vs 34.8%; P<0.001). Multivariate analysis suggested that autograft selection was associated with extended LOS (OR 1.4; 95% CI 1.3-1.5). Conclusion The results of this study provide information regarding how graft selection can relate to extended hospital LOS and influence postoperative complications. Extended LOS may be associated with worse patient outcomes and increase the overall cost of care. Further study should be performed to determine which patients would benefit from autograft versus allograft with regards to long-term outcomes, in consideration of these increased short-term complications.

Pedicle subtraction osteotomy in adult spinal deformity correction: Clinical and radiographic risk factors for early instrumentation failure.

BACKGROUND: Early instrumentation failure (EIF) after pedicle subtraction osteotomy (PSO) is a known complication of adult spine deformity (ASD) correction. In contrast to the more common failure that occurs secondary to pseudarthrosis, early instrumentation failure (<6 months after surgery) and its risk factors are not as well understood. OBJECTIVE: To identify risk factors for EIF in patients undergoing PSO for ASD correction. METHODS: Patients with ASD who underwent correction with PSO from 2013 to 2018 were retrospectively reviewed. Demographic characteristics, number of rods, spinopelvic parameters, bone density derived from computed tomography (CT) attenuation in Hounsfield units (HU), Global Alignment and Proportion (GAP) score, and type of instrumentation failure were evaluated. Potential risk factors for EIF were analyzed. RESULTS: 9 out of 46 (19.5%) patients who underwent PSO had EIF. All 9 patients with EIF had 2-rod constructs and failed secondary to rod fracture. The number of rods used in the EIF group was significantly lower than the non-EIF group (2.00 ± 0.00 vs 2.81 ± 0.995, p = .000. The EIF group demonstrated a significantly higher pre-op PI (77.33 ± 13.23), p = .022, pre-op PT (37.22 ± 6.46),p = .012, and post-op SVA (89.96 ± 23.85), p = .028 compared to the non-EIF group. CONCLUSION: High pre-op PI, pre-op PT, and post-op SVA were significant risk factors associated with EIF after PSO. Use of multiple rod constructs are protective and may help mitigate risk of EIF in these patients.

Pedicle screws with modular head vs. preassembled head used in cortical bone trajectory: Can pars and pedicle fractures be prevented in osteoporotic bone?

Pars and pedicle fractures as a result of CBT (cortical bone trajectory) during pedicle screw placement have been reported. The primary aim of the study is to compare the fracture rate between screws with modular heads to screws with standard pre-assembled tulip heads. The secondary aim of the study is to determine the potential variables that can be identified prior to instrumentation in order to predict risk of fractures. Twenty-four fresh frozen lumbar vertebrae were obtained from five different cadavers. Anatomical landmark measurements were obtained. Right and left pedicles of each vertebra were randomly instrumented with the preassembled head screws (n=24) and modular head screws (n=24) under video recording. X-ray images were obtained for measuring relative angle deviations between tapped and final screw trajectories. Finally, pullout tests were performed. Seventeen out of twenty-four (70.8%) of the spinous processes had to be excised in order to obtain proper trajectories. Six fractures occurred with pre-assembled head screws versus one in the modular head screws (p=0.04). Distances from the midline to the medial wall of the pedicle were marginally significant as a predictor for fracture (p=0.08). The pullout loads between both types of screws were not statistically different (p=0.38). Age was better correlated with pullout load than absolute bone density value (p<0.001). In conclusion, modular head screws had a significantly lower fracture rate than pre-assembled head screws for cortical bone trajectory in osteoporotic bone. There was no clear anatomic variable that could be measured pre-operatively to predict potential fracture risk in CBT.

C1 Lateral Mass Displacement and Transverse Atlantal Ligament Failure in Jefferson's Fracture: A Biomechanical Study of the "Rule of Spence".

BACKGROUND: Jefferson's fracture, first described in 1927, represents a bursting fracture of the C1 ring with lateral displacement of the lateral masses. It has been determined that if the total lateral mass displacement (LMD) exceeds 6.9 mm, there is high likelihood of transverse atlantal ligament (TAL) rupture, and if LMD is less than 5.7 mm TAL injury is unlikely. Several recent radiographic studies have questioned the accuracy and validity of the "rule of Spence" and it lacks biomechanical support. OBJECTIVE: To determine the amount of LMD necessary for TAL failure using modern biomechanical techniques. METHODS: Using a universal material testing machine, cadaveric TALs were stretched laterally until failure. A high-resolution, high-speed camera was utilized to measure the displacement of the lateral masses upon TAL failure. RESULTS: Eleven cadaveric specimens were tested (n = 11). The average LMD upon TAL failure was 3.2 mm (±1.2 mm). The average force required to cause failure of the TAL was 242 N (±82 N). From our data analysis, if LMD exceeds 3.8 mm, there is high probability of TAL failure. CONCLUSION: Our findings suggest that although the rule of Spence is a conceptually valid measure of TAL integrity, TAL failure occurs at a significantly lower value than previously reported (P < .001). Based on our literature review and findings, LMD is not a reliable independent indicator for TAL failure and should be used as an adjunctive tool to magnetic resonance imaging rather an absolute rule.

Rotation effect and anatomic landmark accuracy for midline placement of lumbar artificial disc under fluoroscopy.

PURPOSE: Total disc arthroplasty can be a viable alternative to fusion for degenerative disc disease of the lumbar spine. The correct placement of the prosthesis within 3 mm from midline is critical for optimal function. Intra-operative radiographic error could lead to malposition of the prosthesis. The objective of this study was first to measure the effect of fluoroscopy angle on the placement of prosthesis under fluoroscopy. Secondly, determine the visual accuracy of the placement of artificial discs using different anatomical landmarks (pedicle, waist, endplate, spinous process) under fluoroscopy. METHODS: Artificial discs were implanted into three cadaver specimens at L2-3, L3-4, and L4-L5. Fluoroscopic images were obtained at 0°, 2.5°, 5°, 7.5°, 10°, and 15° from the mid axis. Computerized tomography (CT) scans were obtained after the procedure. Distances were measured from each of the anatomic landmarks to the center of the implant on both fluoroscopy and CT. The difference between fluoroscopy and CT scans was compared to evaluate the position of prosthesis to each anatomic landmark at different angles. RESULTS: The differences between the fluoroscopy to CT measurements from the implant to pedicle was 1.31 mm, p < 0.01; implant to waist was 1.72 mm, p < 0.01; implant to endplate was 1.99 mm, p < 0.01; implant to spinous process was 3.14 mm, p < 0.01. When the fluoroscopy angle was greater than 7.5°, the difference between fluoroscopy and CT measurements was greater than 3 mm for all landmarks. CONCLUSIONS: A fluoroscopy angle of 7.5° or more can lead to implant malposition greater than 3 mm. The pedicle is the most accurate of the anatomic landmarks studied for placement of total artificial discs in the lumbar spine.

Preventing Instrumentation Failure in Three-Column Spinal Osteotomy: Biomechanical Analysis of Rod Configuration.

STUDY DESIGN: Biomechanical analysis. OBJECTIVES: To show the role of additional rods and long-term fatigue strength to prevent the instrumentation failure on three-column osteotomies. SUMMARY OF BACKGROUND DATA: Three-column osteotomy such as pedicle subtraction osteotomy (PSO) and vertebral column resections are surgical correction options for fixed spinal deformity. Posterior fixation for the PSO involves pedicle screw-and rod-based instrumentation, with the rods being contoured to accommodate the accentuated lordosis. Pseudarthrosis and instrumentation failure are known complications of PSO. METHODS: Unilateral pedicle screw and rod constructs were mounted in ultra-high-molecular-weight polyethylene blocks using a vertebrectomy model with the rods contoured to simulate posterior fixation of a PSO. Each construct was cycled under a 200 N load at 5 Hz in simulated flexion and extension to rod failure. Three configurations (n = 5) of titanium alloy rods were tested: single rod (control), double rod, and bridging rod. Outcomes were total cycles to failure and location of rod failure. RESULTS: Double-rod and bridging-rod constructs had a significantly higher number of cycles to failure compared with the single-rod construct (p < .05). Single-rod constructs failed at or near the rod bend apex, whereas the majority of double-rod and bridging-rod constructs failed at the screw-rod or rod-connector junction. CONCLUSIONS: Double-rod and bridging-rod constructs are more resistant to fatigue failure compared with single-rod constructs in PSO instrumentation and could be considered to mitigate the risk of instrumentation failure.

A comparison of Staphylococcus aureus biofilm formation on cobalt-chrome and titanium-alloy spinal implants.

The use of cobalt chrome (CoCr) implants in spinal surgery has become increasingly popular. However, there have been no studies specifically comparing biofilm formation on CoCr with that of titanium-alloy spinal implants. The objective of this study was to compare the difference in propensity for biofilm formation between these two materials, as it specifically relates to spinal rods. Staphylococcus aureus subsp. Aureus (ATCC 6538) were incubated with two different types of spinal rods composed of either CoCr or titanium-alloy. The spinal rods were then subject to a trypsin wash to allow for isolation of the colonized organism and associated biofilms. The associated optical density values (OD) from the bacterial isolates were obtained and the bacterial solutions were plated on brain-heart infusion agar plates and the resultant colony-forming units (CFU) were counted. The OD values for the titanium-alloy rods were 1.105±0.096nm (mean±SD) and 1.040±0.026nm at 48hours and 96hours, respectively. In contrast, the OD values for the CoCr rods were 1.332±0.161nm and 1.115±0.207nm at 48 and 96hours, respectively (p<0.05). The CFU values were 1481±417/100mm(2) and 745±159/100mm(2) at 48 and 96hours, respectively for the titanium-alloy group. These values were significantly lower than the CFU values obtained from the CoCr group which were 2721±605/100mm(2) and 928±88/100mm(2) (p<0.001) at both 48 and 96hours respectively. Our findings, evaluating both the OD and CFU values, indicate that implants composed of CoCr had a higher proclivity towards biofilm formation compared to titanium-alloy implants.

A comparison of open versus percutaneous cervical transfacet fixation.

OBJECTIVE The aim of this study is to describe a technique for percutaneous cervical transfacet screw placement and compare this technique to the open technique with regard to the accuracy of facet capture and the potential of placing neurovascular structures at risk. METHODS Eight cadaveric cervical spines were harvested. One side of each spine was assigned to the percutaneous group, and the other side to the open group. The spines were instrumented from C-3 to T-1 (80 screws). The distance to the spinal canal, foramen transversarium, and neural foramen were measured to determine the likelihood of placing neurovascular structures at risk. The percentage of the facet joint captured and the angle of screw trajectory compared with the ideal trajectory were used to determine the accuracy. RESULTS There were, in total, 11 misplacements of screws: 2 screws using the open technique and 9 screws using the percutaneous technique (p = 0.006). From a neurovascular point of view, 3 percutaneous screws violated the foramen transversarium. Two of these percutaneous screws violated the neural foramen. No neurovascular foramina were violated using the open technique. The open technique resulted in a significantly greater distance from the screw to the spinal canal (p < 0.001). The distance from the screw to the foramen transversarium (p = 0.015), as well as the distance from the screw to the neural foramen (p = 0.012), did not demonstrate statistical difference when using either technique. As for the accuracy of facet capture, 8 screws exhibited less than 15% purchase of the facet joint. Six of these screws were placed using the percutaneous technique, and 2 screws were placed using the open technique. CONCLUSIONS There is a higher incidence of screw misplacement using the percutaneous transfacet in comparison to the open transfacet technique. The accuracies of facet capture using the 2 techniques were not statistically different. Surgeons will need to understand the potential risk of using the percutaneous technique as an alternative to open transfacet fixation.

Survivorship and clinical outcomes after multi-level anterior lumbar reconstruction with stand-alone anterior lumbar interbody fusion or hybrid construct.

In multilevel disc disease, there is still uncertainty regarding whether multiple total disc replacement is more effective and safer than fusion. Our objective was to measure and compare the clinical outcome of multilevel hybrid constructs with stand-alone anterior lumbar interbody fusion (ALIF) using a retrospective analysis. Sixty-four patients with chronic low back pain determined to be from two or three-level degenerative disc disease were included. Thirty-three patients were treated with hybrid fusion and 31 with ALIF. Several parameters were retrospectively reviewed, including blood loss, operation time, hospital stay, Visual Analog Scale (VAS) score, Oswestry Disability Index (ODI), and survivorship without the need for revision surgery. Telephone follow-ups were conducted to ascertain survivorship, clinical outcomes (VAS, ODI) and patient satisfaction. Operation time was longer in the hybrid group (p=0.021). The hybrid group showed a significant improvement in VAS and ODI with 52.2% and 50.0% improvement versus 28.3% and 25.5% in the ALIF group (p<0.05). At the telephone follow-up for patient satisfaction, 95.7% (n=22) of the hybrid group were satisfied and 95.2% (n=21) of the ALIF group were satisfied. Seventy-four percent (n=17) in the hybrid group and 85.7% (n=18) in the ALIF group would choose to do the initial surgery again. Kaplan-Meier analysis showed 80.5% survivorship for hybrids and 75.9% for ALIF at 5years. With our clinical outcomes in VAS and ODI scores, these results, when taken together, indicate that hybrid fusion is a valid and viable alternative to ALIF fusion, with at least equal if not better clinical outcomes in terms of survivorship, back pain, and disability scores.

Fatigue Performance of Cortical Bone Trajectory Screw Compared With Standard Trajectory Pedicle Screw.

STUDY DESIGN: Cadaveric biomechanical study. OBJECTIVE: To determine fatigue behavior of cortical bone trajectory (CBT) pedicle screws. SUMMARY OF BACKGROUND DATA: Cortical bone trajectory screws have been becoming popular in spine surgery; however, the long-term fatigue behavior of the new CBT screws remains understudied and limitations not well defined. METHODS: Twelve vertebrae from six cadaveric lumbar spines were obtained. After bone mineral density (BMD) measurements, each vertebral body was instrumented with screws from each group, that is, CBT (4.5 × 25 mm) or standard pedicle screw (6.5 × 55 mm). A load (± 4 Nm sagittal bending) was applied under displacement control at 1 Hz. Each construct was loaded for 100 cycles or until 6° of loosening was observed. After fatigue testing, the screws were pulled out axially at 5 mm/min. RESULTS: The standard pedicle screw showed better resistance against 100 cycle loading compared with the CBT screws (P < 0.001, 6.9° ± 4.8° vs. 15.2° ± 5.5°, respectively). The standard pedicle screw testing usually required more than 100 cycles of loading to achieve the critical loosening (3592 ± 4564 cycles), whereas the CBT screw never exceeded 100 cycles (84 ± 24 cycles) (P = 0.002). Increased BMD was significantly associated with a higher number of cycles and less loosening. The standard pedicle screw group had a higher postfatigue pullout load than the CBT screw group (P = 0.001, 776 ± 370 N and 302 ± 232 N, respectively). CONCLUSION: The standard pedicle screw had a better fatigue performance compared with the CBT screw in vertebra with compromised bone quality. The proper insertion of the CBT screw might be prevented by the laminar anatomy depending on the screw head design. The CBT screw damaged the bone along its shaft by rotating around a fulcrum, located at either the pars, pedicle isthmus, or the junction of the pedicle and superior endplate, contingent upon the strength of the bone.

Pars and pedicle fracture and screw loosening associated with cortical bone trajectory: a case series and proposed mechanism through a cadaveric study.

BACKGROUND CONTEXT: Cortical bone trajectory (CBT) technique for pedicle screw placement in the lumbar spine has become more popular since its introduction in 2009. The distinct advantages of using the CBT technique involve increased screw purchase within the cortical bone and reduced surgical dissection. However, contrary to several favorable biomechanical results, there were anecdotal reports of clinical complications associated with CBT. PURPOSE: This study aimed (1) to report on two unique pars and pedicle fracture cases involving the use of the CBT technique and (2) to perform a cadaveric pilot study to determine the possible mechanism for this fracture pattern. STUDY DESIGN/SETTING: A case report and cadaveric study were carried out. METHODS: After presenting two clinical cases, 19 fresh-frozen lumbar vertebrae were obtained from 8 cadavers. Pedicle screws were instrumented on each level using CBT under video recording. After the instrumentation, X-ray images were obtained, and anatomical dissections were performed. RESULTS: To be able to reach a necessary angle for medial to lateral CBT trajectory, 13 out of 19 (68%) spinous processes had to be removed. There were a total of seven complications. One pars and pedicle fracture out of 37 trajectories (2.7%) and 6 out of 37 trajectory deviations (16.2%), which resulted in gross loosening, were observed. CONCLUSIONS: The head of the pedicle screw impinging on the base of spinous process and lamina was observed in our cadaveric model. This mechanism could potentially explain both screw loosening and fractures associated with the CBT technique.

Novel posterior technique to temporize life-threatening hemorrhage after great vessel laceration during posterior osteotomy.

PURPOSE: Great vessel injury during posterior 3-column osteotomy is rare, but potentially fatal. Literature review revealed limited data guiding spine surgeons during this major catastrophe. In this study our aim was first, to present our case of mortality; second, to discuss a novel technique that can be performed to temporize hemorrhage in a life-threatening situation where an iatrogenic great vessel injury occurs and hemodynamic stability cannot be achieved through usual means of hemostasis; third, a cadaveric study to determine if this novel technique is feasible. METHODS: Three fresh cadavers including thoracic, lumbar, and pelvis were used. A thoraco-abdominal approach was used to access great vessels at the level of L3. The aorta and vena cava were identified and tagged. The cadavers were turned prone; a pedicle subtraction osteotomy was performed at the level of L3. A novel posterior peri-vertebral approach was used to reach the great vessels. The aorta and vena cava were occluded digitally with this approach and success confirmed visually through the thoraco-abdominal incision. Timing of the procedure and structures at risk were recorded. RESULTS: In all three cadavers, we were able to successfully occlude the great vessels from a prone position. The average amount of time it took to digitally occlude the great vessels was less than a minute. Structures at risk included the L1 and L2 nerve roots, lumbosacral plexus, and the sympathetic trunk. CONCLUSIONS: The posterior peri-vertebral approach can potentially be used by a spine surgeon during a life-threatening situation to temporarily occlude great vessel hemorrhage while waiting for the assistance of a vascular/trauma team.

Early complications after instrumentation of the lumbar spine using cortical bone trajectory technique.

This retrospective chart review aimed to identify and report on a series of early complications that resulted from instrumentation of the lumbar spine using the cortical bone trajectory (CBT) technique. CBT technique is a novel method for fixation of the lumbar spine. Since it was first described in 2009 this technique has gained significant popularity. Here we report a series of early complications that have developed in patients who had lumbar spine fusion using the CBT technique. A retrospective chart review was performed in which all cases utilizing the CBT technique for instrumentation of the lumbar spine by two fellowship trained spine surgeons at our institution between July 2012 and May 2014 were reviewed. Medical records were reviewed to determine the number of patients who went on to develop an early complication after instrumentation with this technique. An early complication was defined as any of the following occurring within 3 months of surgery: (1) early screw loosening confirmed by post-operative CT scan, (2) evidence of fracture development confirmed by post-operative CT scan, (3) intra-operatively identified durotomy, (4) superficial or deep post-operative infection and (5) neurological injury. A total of 22 cases using the CBT technique were performed in our department. Of these cases two patients went onto develop early screw loosening, one developed an intra-operative pars fracture, one developed a dural tear and lastly, one patient developed both a pedicle fracture and early screw loosening. At our institution a total of five patients thus far have developed early complications after undergoing instrumentation of the lumbar spine using the CBT technique between 2012-2014.

Cortical and Standard Trajectory Pedicle Screw Fixation Techniques in Stabilizing Multisegment Lumbar Spine with Low Grade Spondylolisthesis.

BACKGROUND: Cortical screw (CS) fixation has been recently proposed as an alternative to the standard pedicle screw (PS) fixation technique. Biomechanical studies involving individual screw pullout and single level motion segment stabilization showed comparable performance of both techniques. However, whether this new fixation technique can be applied to the stabilization of multilevel lumbar segments with significant destabilization has been unclear. PURPOSE: To compare stability of CS fixation to the traditional PS fixation in an unstable 3 level spondylolisthesis model. STUDY DESIGN: This is a biomechanical study comparing cortical trajectory pedicle screw fixation to traditional trajectory pedicle screw fixation in an unstable cadaveric model using nondestructive flexibility test. METHODS: Eight fresh frozen cadaveric lumbar spines (T12- S1) were obtained. After intact baseline testing, a 3-level lowgrade spondylolisthesis was simulated at the L1-4. Each specimen was instrumented with the PS and CS fixation systems. Standard nondestructive flexibility test was performed. Range of motion at each level was compared between the constructs during flexion-extension, lateral bending, and axial rotation. RESULTS: The destabilization model significantly increased the ROM in all planes (P<0.05). Both fixation techniques provided significant reduction in the ROM (P<0.05). There was no significant difference in ROM between the PS and CS groups in any of planes (P>0.05). CONCLUSIONS: Cortical trajectory pedicle screw fixation provided stabilization to multilevel lumbar segment with low-grade spondylolisthesis comparable to the standard trajectory pedicle screw construct.

Comparison Between Gearshift And Drill Techniques For Pedicle Screw Placement By Resident Surgeons.

BACKGROUND: Various techniques have been described for pedicle screw placement with established clinical and radiological success. Suboptimal screw trajectories can compromise bony purchase and, worse yet, cause neurological and vascular injuries. Thus, it is of paramount importance to achieve maximum accuracy of screw placement. Our objective is to evaluate the accuracy of pedicle screw placement in the thoracolumbar spine by resident surgeons. Two popular techniques, gearshift versus drill, were compared. METHODS: This is a a cadaveric surgical technique comparison study. Six resident surgeons instrumented the spine from T1 to S1 using both gearshift and drill techniques. Each pedicle was randomly assigned to either of the techniques. Pedicle screws were placed freehand without radiographic guidance. Violations (medial, lateral, anterior, superior and inferior) were recorded by studying the computerized tomographic scans of instrumented cadavers by blinded observers. Critical perforations were defined as greater than 2mm breach of the pedicle wall. RESULTS: A total of 100 vertebrae (200 pedicles) were instrumented in the six cadavers. 103 pedicles were breached (51.5% of total pedicles). Lateral violations were the most encountered (65% of violations, 67 total, 48 critical, 19 noncritical) followed by medial (24%, 25 total, 13 critical, 12 noncritical), and the rest were anterior (3%), superior (4%) and inferior (4%). There was no overall difference in violations comparing the gearshift technique (49.5%, 51 total, 37 critical, 14 noncritical) with drill technique (50.5%, 52 total, 33 critical, 19 noncritical). Analyzing the breaches at individual vertebra indicated most violations at T6 (11), T5 (10), followed by T3 (9) and T4 (9), decreasing towards the lumbosacral vertebrae. CONCLUSION: The results of this study suggest that the gearshift and drill techniques for placement of pedicle screws in the thoracolumbar spine fare similarly with regards to risk of breach when applied by resident surgeons.

Unconstrained testing of spine with bi-axial universal testing machine.

BACKGROUND: In-vitro biomechanical assessment of the spine reveals significant information on the mechanics of spinal disorders, treatment methods, and surgical implants. Specialized devices for the evaluation of spine biomechanics have thus become popular. However, these devices might not be affordable for all research groups. PURPOSE: The purpose of this study was to describe an apparatus to be attached to a standard bi-axial universal testing machine that would make unconstrained testing of the spine possible. STUDY DESIGN/SETTING: A technical note on the definition of a spinal testing fixture with validation. METHODS: Intact lumbosacral spines (T12-S1) were tested in sagittal and lateral bending and axial rotation. Three-dimensional interlevel rotations at each level (L1-4) were analyzed. RESULTS: By comparison with the literature, we found that the new fixture was able to successfully produce reasonable relative rotation values for the lumbar spine. CONCLUSIONS: We demonstrated that the low cost fixture allowed unconstrained (six degree of freedom, 6 DOF) testing of fresh-frozen cadaveric lumbar spine.

MRI evaluation of the knee with non-ferromagnetic external fixators: cadaveric knee model.

INTRODUCTION: The advent of MRI-compatible external fixation devices has made the use of MRI possible in patients who have been treated with external fixation. However, although there have been multiple studies determining the safety of MRI scans with external fixator devices, there are no studies determining the artifact effect these devices can have on the MRI image. The purpose of our study was to evaluate the effect of two popular brands (Stryker and Synthes) of MRI-compatible external fixators on the diagnostic capacity of a knee MRI. We hypothesize that (1) MRI images would have higher noise due to the presence of an external fixator and (2) images of high diagnostic capacity will be obtainable in the presence of each external fixator spanning the knee. METHODS: Using seven cadaveric knees, a study was performed to analyze MRI images taken in the presence each external fixator. Scans taken with no external fixator present served as controls. Signal-to-noise ratios (SNRs) were measured at five anatomic structures. These structures were compared as a quantitative measure of image quality. A qualitative analysis was also performed using a five-point grading scale to assess the influence of metal artifact on the quality of the images. Each scan was graded by three blinded musculoskeletal radiologists focusing on six key anatomic structures. RESULTS: A reduction in SNR was identified on the external fixator group compare to the control groups at the patella tendon, MM and PCL. Qualitative scoring by three expert radiologists showed no difference in ability to identify the six key anatomic landmarks between the Stryker, Synthes and control images. CONCLUSION: Although the presence of external fixation devices does increase the noise artifact in MRI scans, patients treated with these external fixators can undergo MRI of local structures with high likelihood of obtaining diagnostic quality images.