Biomechanical assessment of different transforaminal lumbar interbody fusion constructs in normal and osteoporotic condition: a finite element analysis.

BACKGROUND CONTEXT: With the aging population, osteoporosis, which leads to poor fusion, has become a common challenge for lumbar surgery. In addition, most people with osteoporosis are elderly individuals with poor surgical tolerance, and poor bone quality can also weaken the stability of internal fixation. PURPOSE: This study compared the fixation strength of the bilateral traditional trajectory screw structure (TT-TT), the bilateral cortical bone trajectory screw structure (CBT-CBT), and the hybrid CBT-TT (CBT screws at the cranial level and TT screws at the caudal level) structure under different bone mineral density conditions. STUDY DESIGN: A finite element (FE) analysis study. METHODS: Above all, we established a healthy adult lumbar spine model. Second, under normal and osteoporotic conditions, three transforaminal lumbar interbody fusion (TLIF) models were established: bilateral traditional trajectory (TT-TT) screw fixation, bilateral cortical bone trajectory (CBT-CBT) screw fixation, and hybrid cortical bone trajectory screw and traditional trajectory screw (CBT-TT) fixation. Finally, a 500-N compression load with a torque of 10 N/m was applied to simulate flexion, extension, lateral bending, and axial rotation. We compared the range of motion (ROM), adjacent disc stress, cage stress, and posterior fixation stress of the different fusion models. RESULTS: Under different bone mineral density conditions, the range of motion of the fusion segment was significantly reduced. Compared to normal bone conditions, the ROM of the L4-L5 segment, the stress of the adjacent intervertebral disc, the surface stress of the cage, and the maximum stress of the posterior fixation system were all increased in osteoporosis. Under most loads, the ROM and surface stress of the cage and the maximum stress of the posterior fixation system of the TT-TT structure are the lowest under normal bone mineral density conditions. However, under osteoporotic conditions, the fixation strength of the CBT-CBT and CBT-TT structures are higher than that of the TT-TT structures under certain load conditions. At the same time, the surface stress of the intervertebral fusion cage and the maximum stress of the posterior fixation system for the two structures are lower than those of the TT-TT structure. CONCLUSION: Under normal bone mineral density conditions, transforaminal lumbar interbody fusion combined with TT-TT fixation provides the best biomechanictability. However, under osteoporotic conditions, CBT-CBT and CBT-TT structures have higher fixed strength compared to TT-TT structures. The hybrid CBT-TT structure exhibits advantages in minimal trauma and fixation strength. Therefore, this seems to be an alternative fixation method for patients with osteoporosis and degenerative spinal diseases. CLINICAL SIGNIFICANCE: This study provides biomechanical support for the clinical application of hybrid CBT-TT structure for osteoporotic patients undergoing TLIF surgery.

A prospective study of lumbar facet arthroplasty in the treatment of degenerative spondylolisthesis and stenosis: cost-effective assessment from the Total Posterior Spine system (TOPSTM) IDE Study: 2-year model revision and sensitivity analyses based on 305 subjects.

BACKGROUND CONTEXT: A previous cost-effectiveness analysis published in 2022 found that the Total Posterior Spine (TOPSTM) system was dominant over transforaminal lumbar interbody fusion (TLIF). This analysis required updating to reflect a more complete dataset and pricing considerations. PURPOSE: To evaluate the cost-effectiveness of TOPSTM system as compared with TLIF based on an updated and complete FDA investigational device exemption (IDE) data set. STUDY DESIGN/SETTING: Cost-utility analysis of the TOPSTM system compared to TLIF. PATIENT SAMPLE: A multicenter, FDA IDE, randomized control trial (RCT) investigated the efficacy of TOPSTM compared to TLIF with a current population of n=305 enrolled and n=168 with complete 2-year follow-up. OUTCOME MEASURES: Cost and quality adjusted life years (QALYs) were calculated to determine our primary outcome measure, the incremental cost-effectiveness ratio. Secondary outcome measures included: net monetary benefit as well at willingness-to-pay (WTP) thresholds. METHODS: The primary outcome of cost-effectiveness is determined by incremental cost-effectiveness ratio. A Markov model was used to simulate the health outcomes and costs of patients undergoing TOPSTM or TLIF over a 2-year period. alternative scenario sensitivity analysis, one-way sensitivity analysis, and probabilistic sensitivity analysis were conducted to assess the robustness of the model results. RESULTS: The updated base case result demonstrated that TOPSTM was immediately and longitudinally dominant compared with the control with an incremental cost-effectiveness ratio of -9,637.37 $/QALY. The net monetary benefit was correspondingly $2,237, both from the health system's perspective and at a WTP threshold of 50,000 $/QALY at the 2-year time point. This remained true in all scenarios tested. The Alternative Scenario Sensitivity Analysis suggested cost-effectiveness irrespective of payer type and surgical setting. To remain cost-effective, the cost difference between TOPSTM and TLIF should be no greater than $1,875 and $3,750 at WTP thresholds of $50,000 and 100,000 $/QALY, respectively. CONCLUSIONS: This updated analysis confirms that the TOPSTM device is a cost-effective and economically dominant surgical treatment option for patients with lumbar stenosis and degenerative spondylolisthesis compared to TLIF in all scenarios examined.

Predicting the Failure Risk of Internal Fixation Devices in Chinese Patients Undergoing Spinal Internal Fixation Surgery: Development and Assessment of a New Predictive Nomogram.

The current study is aimed at developing and validating a nomogram of the risk of failure of internal fixation devices in Chinese patients undergoing spinal internal fixation. We collected data from a total of 1139 patients admitted for spinal internal fixation surgery at the First Affiliated Hospital of Guangxi Medical University from May 2012 to February 2019. Of these, 1050 patients were included in the spinal internal fixation group and 89 patients in the spinal internal fixation device failure group. Patients were divided into training and validation tests. The risk assessment of the failure of the spinal internal fixation device used 14 characteristics. In the training test, the feature selection of the failure model of the spinal internal fixation device was optimized using the least absolute shrinkage and selection operator (LASSO) regression model. Based on the characteristics selected in the LASSO regression model, multivariate logistic regression analysis was used for constructing the model. Identification, calibration, and clinical usefulness of predictive models were assessed using C-index, calibration curve, and decision curve analysis. A validation test was used to validate the constructed model. In the training test, the risk prediction nomogram included gender, age, presence or absence of scoliosis, and unilateral or bilateral fixation. The model demonstrated moderate predictive power with a C-index of 0.722 (95% confidence interval: 0.644-0.800) and the area under the curve (AUC) of 0.722. Decision curve analysis depicted that the failure risk nomogram was clinically useful when the probability threshold for internal fixation device failure was 3%. The C-index of the validation test was 0.761. This novel nomogram of failure risk for spinal instrumentation includes gender, age, presence or absence of scoliosis, and unilateral or bilateral fixation. It can be used for evaluating the risk of instrumentation failure in patients undergoing spinal instrumentation surgery.

Risk Factor Analysis of Facet Fusion Following Cervical Lateral Mass Screw Fixation with a Minimum 1-Year Follow-up: Assessment of Maximal Insertional Screw Torque and Incidence of Loosening.

Posterior stabilization is a common surgical procedure, which aims for rigid stabilization by facet fusion. Facet non-union has a potential risk of the screw loosening and malalignment. Although some authors have reported the influencing factors about screw loosening in the lumbar spine, there are few reports about the risk factor contributing to the facet non-union in the cervical spine. In all, 22 patients (78 facets and 122 screws) with degenerative cervical kyphosis or spondylolisthesis who underwent decompression and lateral mass screw (LMS) fixation were analyzed. Age, gender, smoking, bone mineral density (BMD), the degree of facet decortication with bone packing, and screw loosening were investigated as risk factors contributing to the facet non-union at each segmental fused level. Facet fusion rate was 85.9% (67/78 facets) and the incidence of loosening was 4.9% (6/122 screws, 4 patients). Insufficient facet decortication with bone packing is a significant risk factor of facet non-union (p <0.05, odds ratio: 26.5). All six loosened screws were associated with bony non-union of the facet and were located in the uppermost or lowermost vertebrae. Comparing loosened screws and stable screws, the average maximal insertional screw torque (MIT) was 9.8 cNm and 39.5 cNm, respectively (p <0.05). Additionally, the length of the stable screws was significantly longer versus the loosened screws (p <0.05). Lower MIT and shorter screw length located near the ends of the lateral mass may predict loosening, which can lead to facet non-union. Sufficient facet decortication with bone packing is one of the important factors contributing to the facet fusion.

Accuracy of EOS Imaging Technology in Comparison to Computed Tomography in the Assessment of Vertebral Rotational Orientation in Instrumented Spines in Adolescent Idiopathic Scoliosis.

STUDY DESIGN: Retrospective radiographic reliability study. OBJECTIVE: The aim of this study was to assess the validity of EOS 3D imaging technology in the determination of vertebral rotations in the spine of patients with previous instrumentation. SUMMARY OF BACKGROUND DATA: There is a lack of evidence on the accuracy of vertebral rotational measurement using EOS 3D morphological analysis in the instrumented spine. METHODS: A retrospective review of 31 patients with adolescent idiopathic scoliosis (AIS) who underwent instrumented fusion and postoperative computed tomography (CT) scans of the spine was performed. Vertebral rotations of the apex vertebra, the uppermost (UIV) and lowermost (LIV) instrumented vertebra, the noninstrumented vertebra one level cranial to the UIV (UIV + 1) and one level caudal to LIV (LIV + 1) were determined using EOS 3D reconstruction. The vertebral rotation was also measured using reformatted CT axial images. Relative vertebral rotational difference (VRD) were calculated for UIV to apex, UIV + 1 to apex, LIV to apex, LIV + 1 to apex, UIV to LIV and UIV + 1 to LIV + 1. Paired t tests were used to compare the VRD measured using the two different imagining modalities. For values where P > 0.05, the Bland-Altman plot was used to assess the agreement between the measures. Interclass correlation (ICC) was used to determine interobserver and intraobserver reliabilities of EOS and CT measurements. RESULTS: EOS analysis of relative VRD was found to be significantly different from that of CT for UIV to apex (P = 0.006) and UIV + 1 to apex (P = 0.003). No significant differences were found for LIV to apex (P = 0.06), LIV + 1 to apex (P = 0.06), UIV to LIV (P = 0.59) and UIV + 1 to LIV + 1 (P = 0.64). However, Bland-Altman plots showed that agreement was poor, and variance was beyond acceptable. ICC showed good interobserver and good to very good intraobserver reliability for EOS. CONCLUSION: EOS 3D morphological analysis of VRD in the instrumented levels of the spine demonstrated significant difference and unacceptable variance in comparison to CT measurement.Level of Evidence: 4.

Analysis of Clinical and Radiological Outcomes of Posterior Dynamic Stabilization for Direct Repair of Bilateral L5 Pars Interarticularis Defect: Dynamic Assessment of Pars Fusion.

AIM: To evaluate the satisfactory clinical and radiological outcomes of posterior dynamic stabilization for the direct repair of bilateral L5 pars interarticularis defects and pars fusion. MATERIAL AND METHODS: This is a retrospective evaluation of postoperative follow-up results of 13 patients with bilateral L5 pars interarticularis defects without spondylolisthesis. The patients underwent dynamic transpedicular stabilization between 2013 and 2018. Our surgical criteria included unilateral or bilateral L5 spondylolysis; excessive low back pain; low back pain accompanied by leg pain without neurological findings; symptoms lasting at least six months despite conservative treatments, age < 50 years; and lack of significant adjacent disc degeneration. RESULTS: There were seven female and six male patients with a mean age of 38.9 years. All patients achieved satisfactory postoperative results during a mean follow-up period of 22 months. Preoperative visual analog scale score and Oswestry Disability Index value were 8.85 ± 0.69 and 54.46 ± 7.62, respectively, which decreased to 1.31 ± 0.48 and 9.85 ± 3.51, respectively, at the postoperative 24th month. In all patients, the bony fusion of the pars interarticularis at the stabilized segment was confirmed on the computed tomography scan at an average of 22 months postoperatively. CONCLUSION: The posterior dynamic system ensures that the spine moves within physiological limits and carries the load by sharing it with the spine. The advantages of direct pars repair using our technique are the restoration of the posterior structures? normal anatomy, protection of the functional mobility segment, and early functional recovery without degeneration in the adjacent segment. Therefore, when there is no significant instability, patients with spondylolysis can be treated with posterior dynamic stabilization techniques with satisfactory clinical and radiological results.

Is it feasible to implement a rapid recovery pathway for adolescent idiopathic scoliosis patients undergoing posterior spinal instrumentation and fusion in a single-payer universal health care system?

PURPOSE: The purpose of this project was to determine if it is feasible to implement a rapid recovery pathway (RRP) for the surgical treatment of adolescent idiopathic scoliosis (AIS) within a single-payer universal healthcare system while simultaneously decreasing length of stay (LOS) without increasing post-operative complications. METHODS: A retrospective analysis was completed for all patients who underwent posterior spinal fusion for AIS at a tertiary children's hospital in Canada between March 2010 and February 2019, with date of implementation of the RRP being March 1st, 2015. Patient demographic information was collected along with a variety of outcome variables including: LOS, wound complication, infection, 30-day return to the OR, 30-day emergency department visit, and 30-day hospital readmission. An interrupted time series analysis was utilized to determine if any benefits were associated with the implementation of the RRP. RESULTS: A total of 244 patients were identified, with 113 patients in the conventional pathway and 131 in the RRP. No significant differences in demographic features or post-operative complications were found between the two cohorts (p > 0.05). Using a robust linear time series model, LOS was found to be significantly shorter in the RRP group, with the average LOS being 5.2 [95% IQR 4.3-6.1] days in the conventional group and 3.4 [95% IQR 3.3-3.5] days in the RRP group (p < 0.05). CONCLUSION: This study shows that it is possible to implement a RRP for the surgical treatment of AIS within a single-payer universal healthcare system. Use of the pathway can effectively reduce hospital LOS without increasing the risk of developing a post-operative complication. This has the upside potential to reduce healthcare and family costs. LEVEL OF EVIDENCE: Therapeutic III.

Pilot study of oblique lumbar interbody fusion using mobile percutaneous pedicle screw and validation by a three-dimensional finite element assessment.

The purpose of this study was to try oblique lateral interbody fusion (OLIF) using percutaneous pedicle screws (PPS) with mobility. Twelve patients who underwent single-level OLIF were observed for at least one year. These included 6 patients with conventional PPS (rigid group), and 6 with movable PPS (semi-rigid group). Mobile PPS used cosmicMIA, which is a load sharing system. The anterior and posterior disc height, screw loosening and bone healing period, and implant failure were evaluated at final observation by CT. Moreover, the stress on the vertebral body-cage, on the vertebral body-screw/rod and on the bone around the screw was estimated using a three-dimensional finite element assessment in both groups. There was no significant difference in surgical time, amount of bleeding, JOA score, or low back pain VAS between groups. There were no differences between groups in anterior and posterior disc height, screw loosening, and implant failure at final observation. The bone healing period was significantly shorter in the semi-rigid screw group (18.3 months vs 4.8 months, p = 0.01). The finite element analysis showed that the lower stress on the rod/screw would contribute to fewer implant fractures and that lower stress on the bone around the screw would reduce screw loosening, and that higher compressive force on the cage would promotes bone healing. OLIF combined with a movable screw accelerated bone healing by nearly 75%. We conclude that mobile PPS in combination with OLIF promotes bone healing and can be a better vertebral fusion technique.

Use of instrumented lumbar spinal surgery for degenerative conditions: trends and costs over time in Ontario, Canada

Background: Instrumented lumbar surgeries, such as lumbar fusion and lumbar disc replacement, are increasingly being used in the United States for low back pain, with utilization rates approaching those of total joint arthroplasty. It is unknown whether there is a similar pattern in Canada. We sought to determine utilization rates and total medical costs of instrumented lumbar surgeries in a single-payer system and to compare these with the rates and costs of total hip and knee replacements. Methods: We included Ontarians aged 20 years and older who underwent instrumented lumbar surgery or total knee or total hip replacement between April 1993 and March 2012. Utilization and medical cost of the procedures were evaluated and compared using linear regression in a time-series analysis. Instrumented lumbar surgical procedures were stratified by age and main indication for surgery. Results: Utilization of instrumented lumbar surgeries rose from 6.2 to 14.2 procedures per 100 000 population between 1993 and 2012 (p < 0.001), well below the utilization of knee and hip arthroplasties. Patients were younger than 50 years for 29.2% of all instrumented lumbar surgery cases; annual procedure rates among those older than 80 years rose 7.6-fold. Direct medical costs of instrumented lumbar surgeries from 2002 to 2012 totaled $176 million. Spinal stenosis and spondylolisthesis were the most common indications for instrumented lumbar surgeries. Conclusion: Use of instrumented lumbar surgeries in Ontario's single-payer system has increased rapidly, especially among patients older than 80 years. In contrast to the situation in the United States, these rates were well below those of total joint arthroplasties. These data provide useful insights about resource allocation for surgical treatment of lumbar degenerative disorders.

Contexte: Les chirurgies lombaires instrumentées, telles que l'arthrodèse ou la prothèse discale lombaires, sont de plus en plus utilisées aux États-Unis pour le traitement de la lombalgie, leurs taux d'utilisation s'approchant de ceux de l'arthroplastie totale. On ignore si la tendance est la même au Canada. Nous avons voulu mesurer les taux d'utilisation et les coûts médicaux totaux des chirurgies lombaires instrumentées et les comparer aux taux et aux coûts de l'arthroplastie totale de la hanche et du genou. Méthodes: Nous avons inclus les Ontariens de 20 ans et plus ayant subi une chirurgie lombaire instrumentée ou une arthroplastie totale du genou ou de la hanche entre avril 1993 et mars 2012. L'utilisation et les coûts médicaux des interventions ont été évalués et comparés par analyse de régression linéaire des séries chronologiques. Les chirurgies lombaires ont été stratifiées selon l'âge et la principale indication. Résultats: Le recours aux chirurgies lombaires instrumentées a augmenté de 6,2 à 14,2 interventions par 100 000 de population entre 1993 et 2012 (p < 0,001), ce qui reste bien inférieur au recours à l'arthroplastie du genou et de la hanche. Les patients avaient moins de 50 ans pour 29,2 % de tous les cas de chirurgies lombaires instrumentées; le taux annuel d'interventions chez les patients de plus de 80 ans a augmenté selon un facteur de 7,6. Les coûts médicaux directs des chirurgies lombaires instrumentées ont totalisé 176 millions de dollars entre 2002 et 2012. La sténose rachidienne et le spondylolisthésis étaient les plus fréquentes indications des chirurgies lombaires instrumentées. Conclusion: L'utilisation de la chirurgie lombaire instrumentée pour le régime d'assurance santé à payeur unique ontarien a augmenté rapidement, particulièrement chez les patients de plus de 80 ans. Comparativement à la situation qui prévaut aux États-Unis, ces taux sont bien inférieurs aux taux d'arthroplasties totales. Ces données sont intéressantes du point de vue de l'allocation des ressources pour le traitement chirurgical de la dégénérescence discale lombaire.

Single-use versus reusable medical devices in spinal fusion surgery: a hospital micro-costing analysis.

PURPOSE: Healthcare facilities could minimize the cost of surgical instrument and implant processing by using single-use devices. The main objective was to prospectively compare the total cost of a single-use and reusable device used in short lumbar spine fusion. METHODS: A 1-year, single-centre, prospective study was performed on patients requiring a one- or two-level lumbar arthrodesis. Patients were randomized in two groups treated with either reusable or single-use device. A cost minimization analysis was performed using a micro-costing approach from a hospital perspective. Every step of the preparation process was timed and costed based on hourly wages of hospital employees, cleaning supplies and hospital waste costs. RESULTS: Forty cases were evaluated. No significant difference in operation time was noted (reusable 176.1 ± 68.4 min; single use 190.4 ± 71.7 min; p = 0.569). Mean processing time for single-use devices was lower than for reusable devices (33 min vs. 176 min) representing a cost of 14€ versus 58€ (p < 0.05). Pre-/post-sterilization and spinal set recomposing steps were the most time-consuming in reusable device group. A total cost saving of 181€ per intervention resulted from the use and processing of the single-use device considering an additional sterilization cost of 137€ with the reusable device. The weight of the reusable device was 42 kg for three containers and 1.2 kg for the single-use device. CONCLUSIONS: Owing to the absence of re-sterilization, single-use devices in one- and two-level lumbar fusion allow significant money and time savings. They may also avoid delaying surgery in case of reusable device unavailability.

Retrospective Multicenter Assessment of Rod Fracture After Anterior Column Realignment in Minimally Invasive Adult Spinal Deformity Correction.

BACKGROUND: Anterior column realignment (ACR) was developed as a minimally invasive method for treating sagittal imbalance. However, rod fracture (RF) rates associated with ACR are not known. Our objective was to assess the rate of and risk factors for RF following ACR in deformity correction surgery. METHODS: We conducted a retrospective multicenter review of patients with adult spinal deformity (ASD) who underwent ACR for deformity correction. ASD was defined as coronal Cobb angle ≥20°, pelvic incidence-lumbar lordosis >10°, sagittal vertical axis ≥5 cm, pelvic tilt ≥25°, or thoracic kyphosis ≥60°. Inclusion criteria were ASD, age >18 years, use of ACR, and development of RF or full radiographs obtained at least 1 year after surgery that did not demonstrate RF. RESULTS: Ninety patients were identified, with mean follow-up of 2.3 ± 1.4 years (age, 64.1 ± 9.4; 54 [60%] women). The most common ACR location was L3/4 (42 cases; 47%). Mean fusion length was 7.5 ± 3.6 levels. Four (4.4%) of 90 patients developed RF within 12 months of surgery. RF occurred adjacent to ACR in all cases; RF was not associated with focal correction (P = 0.49), rod material (P = 0.8), degree of correction (P > 0.07), or interbody at L5/S1 (P = 0.06). RF was associated with longer fusion constructs in univariate (P = 0.002) and multivariate (P = 0.03) analyses. CONCLUSIONS: RF occurred in 4.4% of patients with ASD who underwent ACR with a minimum of 1-year follow-up. RF was not associated with focal correction but appears to be associated with global correction and extent of fixation.

A Systematic Review and Meta-Analysis of Perioperative Parameters in Robot-Guided, Navigated, and Freehand Thoracolumbar Pedicle Screw Instrumentation.

BACKGROUND: Robotic guidance (RG) and navigation (NV) have been shown to reduce radiologic and clinically relevant pedicle screw malpositions. It remains unknown if there are any additional benefits to these techniques in intraoperative and perioperative end points. METHODS: We conducted a systematic review in MEDLINE, Embase, Scopus, and the Cochrane Library and identified controlled studies comparing RG, NV, and freehand (FH) thoracolumbar pedicle screw insertion and carried out random-effects meta-analyses. RESULTS: Thirty-two studies (24,008 patients) were included. Only 8 studies (26%) were randomized, and study quality was rated as very low or low in 24 cases (77%). Compared with NV, FH procedures showed longer length of hospital stay (Δ, 0.7 days; 95% confidence interval, 0.2-1.2; P = 0.006) and more overall complications (odds ratio, 1.6; 95% confidence interval, 1.3-1.9; P < 0.001). No statistically significant differences among RG and FH were identified, likely because of lack in statistical power (all P > 0.05). In particular, both RG and NV did not show increased intraoperative radiation use, as determined by seconds of fluoroscopy, compared with FH (both P > 0.05). CONCLUSIONS: It seems that navigation may offer potential benefits in perioperative outcomes such as length of hospital stay and overall complications, without significant increase in intraoperative radiation, which cannot yet be said for robotic guidance. The findings must be interpreted with caution, because the evidence is severely limited in both quantity and quality. Further evaluation will establish any demonstrable intraoperative or perioperative benefits to computer assistance, which may warrant the high costs often associated with these devices.

Cervical Template to Optimize the Plate-to-Disc Distance in Instrumented Anterior Cervical Discectomies and Fusions: Instrumentation Assessment.

BACKGROUND: An increased incidence of adjacent segment degeneration in the cervical spine has been associated with a plate-to-disc distance (PDD) of <5 mm. OBJECTIVE: To introduce a template to size, position, and secure a cervical plate and ensure a 5-mm minimum PDD. METHODS: A prospective observational study was performed on 50 consecutive patients who had single-level anterior cervical discectomy and fusion (ACDF) using a cervical template. The cervical template was secured into the interbody spacer and assessed for length, PDD, and adequate vertebral body coverage. Holes were drilled through the template, which was then removed for cervical plate placement. Postoperative radiographs were assessed for PDD to adjacent segments, the angle from the vertical axis of the spine, and distance from midline. Neck Disability Index and visual analog scale scores for the neck and arm were obtained preoperatively and at 30-d and 90-d follow-up. RESULTS: Fifty patients underwent single-level ACDFs. The mean angle from the long axis of the spine was 2.4 (0.0-4.4) degrees; mean distance from midline was 1.3 (0.0-2.8) mm; and mean distance from the plate ends to the adjacent segments above was 5.4 (4.6-6.2) mm, and below, 5.1 (4.3-5.8) mm. CONCLUSION: A cervical template can reliably secure the midline and predetermine the size of the shortest cervical plate for adequately stabilizing the segment for arthrodesis. Use of a template standardizes the process of maximizing the PDD.

Polyetheretherketone Rods in Lumbar Spine Degenerative Disease: Mid-term Results in a Patient Series Involving Radiological and Clinical Assessment.

AIM: To evaluate the satisfaction of patients operated due to degenerative lumbar spinal diseases with dynamic stabilization placing polyetheretherketone (PEEK) rods and to share their radiological and clinical results (mid-term) with visual analogue scale (VAS) and Oswestry disability index (ODI) scores. MATERIAL AND METHODS: The preoperative and postoperative low back pain, leg pain VAS and ODI scores of 172 patients who were operated for degenerative spinal diseases, were evaluated. Preoperative and postoperative lumbar lordosis were compared. The patients included to the study were evaluated postoperatively around the 2nd year with lumbar MRI by means of adjacent segment disease (ASD) and additional problems. RESULTS: A statistically but not radiologically-by means of sagittal profile reconstruction-significant increase in lumbar lordosis angle was achieved. Significant improvement was observed in the comparison of preoperative and postoperative period in the analysis of patients’ preoperative low back pain (p < 0.0001), and decompression-related leg pain VAS scores (p < 0.0001). Significant improvement was also observed in the ODI scores of the patients (p < 0.0001). Among 172 patients with dynamic stabilization, there were 10 patients who underwent reoperation (5.8%). CONCLUSION: Although it is statistically significant, it can be seen that the lumbar lordosis can not be corrected at significant degrees radiographically in the operations performed with the PEEK rod. Dynamic stabilization with PEEK rod is insufficient for sagittal correction, but the mid-term results reached satisfactory reoperation rates clinically outcomes. Rate of ASD is quite low in stabilization with PEEK rod.

Measurement Techniques and Utility of Hounsfield Unit Values for Assessment of Bone Quality Prior to Spinal Instrumentation: A Review of Current Literature.

STUDY DESIGN: A systematic review. OBJECTIVE: The aim of this study was to evaluate the clinical utility of assessing bone quality using computed tomography (CT) attenuation in Hounsfield units (HU). SUMMARY OF BACKGROUND DATA: Assessing bone quality before spine instrumentation is an essential step of preoperative planning. Dual energy x-ray absorptiometry (DEXA) has been the gold standard for assessing bone mineral density (BMD); however, DEXA can result in spuriously elevated BMD measurements in patients with degenerative disease, compression fractures, and/or vascular calcifications. Measuring vertebral HU values has been proposed as an alternate method of assessing BMD and bone quality. METHODS: We searched MEDLINE, Cochrane Library, and EMBASE for studies correlating HU to BMD and to spine surgery outcomes. RESULTS: HU measurements correlate with success of lumbar interbody fusion (133.7 vs. 107.3 HU) and posterolateral fusion (167 vs. 139.8 HU), cage subsidence (112.4 vs. 140.2 HU), adjacent segment fractures (145.6 vs. 199.4 HU), pedicle screw loosening (116.4 vs. 132.7 HU) and (99.1 vs. 141.2 HU), and risk of incidental durotomy (149.2 vs. 177.0 HU). Intra and inter-rater reliability coefficients are 0.964 and 0.975. The correlation between HU values and BMD in nondegenerative patients is r = 0.52 compared with HU versus BMD in degenerative patients r = 0.18. CONCLUSION: HU value measurement is a simple and rapid technique to assess bone quality that should be performed in all patients with pre-existing CT scans. HU measurement has excellent inter and intra-rater reliability and can be performed on axial or sagittal images. L1 HU threshold values of 110 HU for detecting osteoporosis, and 135 HU for detecting osteopenia are 90% specific. In patients with significant degenerative disease, HU values should be given more credence. Additional high-quality prospective studies comparing HU and DEXA values to patient outcomes are necessary to validate the role of CT measurements in preoperative evaluation. LEVEL OF EVIDENCE: 4.

Biomechanical and histologic assessment of a novel screw retention technology in an ovine lumbar fusion model.

BACKGROUND CONTEXT: Screw loosening is a prevalent failure mode in orthopedic hardware, particularly in osteoporotic bone or revision procedures where the screw-bone engagement is limited. PURPOSE: The objective of this study was to evaluate the efficacy of a novel screw retention technology (SRT) in an ovine lumbar fusion model. STUDY DESIGN/SETTING: This was a biomechanical, radiographic, and histologic study utilizing an ovine lumbar spine model. METHODS: In total, 54 (n=54) sheep lumbar spines (L2-L3) underwent posterior lumbar fusion (PLF) via pedicle screw fixation, connecting rod, and bone graft. Following three experimental variants were investigated: positive control (ideal clinical scenario), negative control (simulation of compromised screw holes), and SRT treatments. Biomechanical and histologic analyses of the functional spinal unit (FSU) were determined as a function of healing time (0, 3, and 12 months postoperative). RESULTS: Screw pull-out, screw break-out, and FSU stability of the SRT treatments were generally equivalent to the positive control group and considerably better than the negative control group. Histomorphology of the SRT treatment screw region of interest (ROI) observed an increase in bone percentage and decrease in void space during healing, consistent with ingrowth at the implant interface. The PLF ROI observed similar bone percentage throughout healing between the SRT treatment and positive control. Less bone formation was observed for the negative control. CONCLUSIONS: The results of this study demonstrate that the SRT improved screw retention and afforded effective FSU stabilization to achieve solid fusion in an otherwise compromised fixation scenario in a large animal model.

Assessment of Change of Shoulder Balance in Patients with Adolescent Idiopathic Scoliosis after Correctional Surgery.

OBJECTIVE: To identify factors that influence shoulder balance and to determine whether a model can be made to predict shoulder balance after corrective surgery. METHODS: This is a retrospective study in which we examined the records of with adolescent idiopathic scoliosis (AIS) patients who underwent single posterior spinal correction and fusion using all pedicle screws with derotation in our institution between January 2008 and June 2010. For the radiographic outcome measurement, we measured the preoperative lumbar curve, the main thoracic curve, and their difference (L_TH_D), and the degree of correction of the lumbar curve, the main thoracic curve, and their difference (c_L_TH_D) to evaluate their influence on postoperative shoulder balance. The preoperative flexibility of the proximal non-fusion curve on the immediate postoperative tilt of the upper endplate of the uppermost vertebra of fusion segments (Up_FuS) was used to evaluate and predict the shoulder balance at follow-up. RESULTS: For patients who had shoulder balance at follow-up, the average balance time was 7.1 months, and in most of them, balance was detected within 12 months. The main thoracic curve has the greatest influence on preoperative shoulder tilt and correction of the main thoracic curve has the greatest influence on the postoperative alteration in shoulder balance. To evaluate the influence on the preoperative shoulder tilt, the lumbar curve must be larger than the main thoracic curve both pre operatively and postoperatively. If the preoperative flexibility of the proximal non-fusion curve on the immediate postoperative Up_FuS includes the horizontal line (With Horizontal group), shoulder balance can be ensured. The postoperative Up_FuS can be evaluated based on the preoperative Up_FuS and the degree of correction of the lumbar and main thoracic curves. CONCLUSION: Shoulder balance can be ensured in patients in the With Horizontal group after surgery. If the preoperative Up_FuS and the degree of correction of the main thoracic curve and the lumbar curve are considered in the preoperative plan, the desired postoperative Up_FuS can be achieved, ensuring shoulder balance at follow-up.

The Barrow Innovation Center Case Series: Early Clinical Experience with Novel, Low-Cost Techniques for Bone Graft Containment in the Posterolateral Fusion Bed.

BACKGROUND: A frequently encountered problem during posterolateral fusion (PLF) is bone graft displacement from the posterolateral space during closure. Commercially available solutions to this problem are seldom used because of their exceptionally high cost. The purpose of this report is to describe 3 novel, low-cost techniques we developed for bone graft containment during PLF. METHODS: Three low-cost bone graft containment techniques are described: rapid suture weave, makeshift bone bag, and cellulose rooftop. Early clinical experience with these techniques is reported for a 5-patient case series. RESULTS: One or more of these bone graft containment techniques were used in 5 patients who underwent PLF. Rapid suture weave was the least expensive (<$5.00) but required the longest additional time to perform (20 minutes). Makeshift bone bag and cellulose rooftop cost approximately the same ($48.00 and $46.00, respectively); the makeshift bone bag took less additional time (3 minutes) but created a potential barrier between the bone graft and the host site, whereas the cellulose rooftop took slightly longer to perform (5 minutes) but permitted direct contact between the bone graft and host site. CONCLUSIONS: These 3 novel surgical techniques for bone graft containment in the posterolateral space add minimally to the cost and length of the procedure. Our early clinical experience suggests that these techniques are safe and effective. Additional clinical experience is warranted, and prospective data collection is ongoing.

Assessment of Coronal Spinal Alignment for Adult Spine Deformity Cases After Intraoperative T Square Shaped Use.

STUDY DESIGN: Retrospectively reviewed surgeries between 2011 and 2015 of patients who underwent posterior spinal deformity instrumentation with constructs involving fusions to pelvis and encompassing at least five levels. OBJECTIVE: Measure the radiographic outcomes of coronal malalignment (CM) after use of an intraoperative T square shaped instrument in posterior spinal deformity surgeries with at least five levels of fusion and extension to pelvis. BACKGROUND: Neuromuscular children found to benefit from intraoperative T square technique to help achieve proper coronal spinal balance with extensive fusions. This intraoperative technique used in our posterior spine deformity instrumentation surgeries with the aforementioned parameters. METHODS: There were 50 patients: n = 16 with intraoperative T square and n = 34 no-T square shaped device. Subgroups divided based on greater than 20 mm displacement and greater than 40 mm displacement of the C7 plumb line to the central sacral vertical line on either side in preoperative radiographs. We analyzed the demographics and the pre- and postoperative radiographic parameters of standing films: standing CM (displacement of C7 plumb line to central sacral vertical line), and major coronal Cobb angles in total sample and subgroups and compared T square shaped device with no-T square shaped device use by analysis of variance. A p value ≤.05 is statistically significant. RESULTS: In the total sample, though postoperative CM mean was not statistically different, we observed greater CM corrections in patients where a T square shaped device was used (70%) versus no-T square shaped device used (18%). In >20 mm and >40 mm subgroups, the postoperative mean CM values were statistically lower for the patients where a T square shaped device was used, p = .016 and p = .003, respectively. Cobb corrections were statistically higher for T square shaped device use in both >20 mm and >40 mm subgroups, 68%, respectively. CONCLUSION: The intraoperative T square shaped device technique had a positive effect on the amount of spine coronal malalignment correction after its use and for lumbar and thoracic coronal Cobb angles. LEVEL OF EVIDENCE: Level III.

Assessment of Proximal Junctional Kyphosis and Shoulder Balance With Proximal Screws versus Hooks in Posterior Spinal Fusion for Adolescent Idiopathic Scoliosis.

STUDY DESIGN: A retrospective review of a prospectively collected multicenter database. OBJECTIVE: To assess the effect of proximal hooks versus screws on proximal junctional kyphosis (PJK) as well as shoulder balance in otherwise all pedicle screw (>80%) posterior spinal fusion (PSF) constructs in adolescent idiopathic scoliosis (AIS). SUMMARY OF BACKGROUND DATA: Less rigid forms of fixation at the top of constructs in degenerative lumbar PSF have been postulated to decrease the risk of PJK. METHODS: A multicenter AIS surgical database was reviewed to identify all patients who underwent PSF with all pedicle screw (>80%) constructs and minimum 2-year follow-up. Patients in the "hook" group had two hooks used at the top of the construct, whereas the "screw" group used only pedicle screws at all levels. RESULTS: A total of 354 patients were identified, 274 (77%) in the screw group, and 80 (23%) in the hook group. There were no significant preoperative differences with regards to curve type, coronal/sagittal Cobb angle, or curve flexibility for either group. At 2 years post-op, the coronal Cobb correction was similar for both groups (60%). There was no difference in correction of shoulder asymmetry and T1 rib angle, including when the groups were matched for preoperative shoulder balance. PJK, defined as the sagittal Cobb angle between the uppermost instrumented and uninstrumented vertebrae, was similar for the screw versus hook group as well (7.1° vs. 6.2°, P = 0.2). CONCLUSION: The use of different anchors (pedicle screws vs. hooks) at the top of an otherwise all pedicle screw PSF construct for AIS did not have any significant bearing on the correction of shoulder asymmetry and coronal Cobb angle at 2 years postoperative. There was also no significant difference in the magnitude of PJK or incidence of marked PJK (>15°) between either group at 2 years. LEVEL OF EVIDENCE: 3.