Disc Wedging Research Articles

Intervertebral disc deformation in the lower lumbar spine during object lifting measured in vivo using indwelling bone pins

Object lifting is often categorized into squat and stoop techniques, with the former believed to protect the back by maintaining a neutral spine, and the latter considered harmful due to spinal flexion. Despite the widespread promotion of these beliefs, there is no evidence to support such dichotomy, as spinal flexion is not conclusively linked to low back pain. This study aimed to investigate intervertebral disc deformation in the lower lumbar spine during squat and stoop lifting using indwelling bone pins. Five healthy males underwent insertion of Kirschner wires into the L3, L4, and L5 spinous processes, followed by biomechanical data collection using magnetic and optical tracking systems during upright standing, isolated flexion/extension, and object lifting with both squat and stoop techniques. Except for one subject, stoop lifting resulted in up to 90 % greater disc wedging compared to squat lifting, with a significant difference at L4/L5 (p = 0.042). The anterior annulus fibrosus experienced 10 % to 40 % more compression during stoop lifting, but no significant differences were found in posterior annulus fibrosus expansion between techniques. Lever arms were about 35 % longer during stoop compared to squat lifting. These results indicate that even though stoop lifting generally led to greater disc deformation, significant deformation was also observed during squat lifting, challenging the notion of maintaining a neutral spine with this technique. Moreover, the considerable variability observed among participants raises concerns about the suitability of current one-size-fits-all lifting guidelines.

MRI study on the influence of lumbosacral vertebral body and disc factors on lumbar lordosis in children.

To evaluate the influence of vertebral and disc wedging on the contribution of lumbar lordosis and the change of disc thickness before and after walking based on MRI. Cross-sectional study. A total of 96 normally developing children, aged 5.7 ± 3.0 years old, 55 boys and 41 girls. They were divided into 3 groups: Pre-walking group, Walking group, and Post-walking group. lumbar lordosis Angle (LLA), the sum of the lumbar disc wedge Angle (∑D), the sum of the lumbar vertebral body wedge Angle (∑B), disc height (DH). (1) LLA, ∑D, ∑B, and DHL1-S1 were 33.2 ± 8.7°, 14.1 ± 8.6°, 11.9 ± 8.6°, and 6.9 ± 1.2mm, 7.6 ± 1.4mm, 8.2 ± 1.6mm, 8.9 ± 1.7mm, 8.5 ± 1.8mm. (2) The difference in LLA values between the Pre-walking and the Post-walking group was statistically significant. DH were significantly different among the three groups. (3) In the Post-walking group, LLA value of girls was significantly higher than that of boys, and DHL3 - 4 and DHL4 - 5 values of girls were significantly lower than that of boys. (4) Age had a low positive correlation with LLA and ∑D and a moderate to strong positive correlation with DH; LLA showed a moderate positive correlation with ∑D, and a low positive correlation with ∑B and DH. Age and walking activity are the influencing factors of lumbar lordosis and disc thickening. Walking activity can significantly increase lumbar lordosis, and age is the main factor promoting lumbar disc thickening. DHL4-5 was the thickest lumbar intervertebral disc with the fastest intergroup thickening. Disc wedging contributes more to lumbar lordosis than vertebral wedging.

Differential vertebral body growth is maintained after vertebral body tethering surgery for idiopathic scoliosis: 4-year follow-up on 888 peri-apical vertebrae and 592 intervertebral discs.

To radiographically evaluate if vertebral body tethering (VBT) can maintain differential peri-apical vertebral growth at medium-term follow-up of 4years. A prospective, international, multicenter database was queried to identify idiopathic scoliosis patients treated with thoracic VBT. Concave vs. convex vertebral body height, vertebral wedging, and disc wedging of the 3 peri-apical vertebrae were measured by two independent observers at 5 timepoints (pre-operative to 4-year follow-up). 65 skeletally immature patients (60 female, mean 12.8years old, 21 with open triradiate cartilages) met inclusion criteria. Mean pre-operative maximum scoliosis of 50 ± 8° decreased significantly post-operatively to 27 ± 9° (p < 0.001), which remained stable at 4-year follow-up 30 ± 17° (p = 0.38 vs. post-operative). Mean instrumented scoliosis was 21 ± 14° at 4-year follow-up, which was significantly different than 4-year maximum scoliosis (p < 0.001). Mean pre-operative kyphosis of 30 ± 12° did not significantly change post-operatively (p = 1.0) and remained stable at 4-year follow-up (35 ± 18°; p = 0.05). Mean individual convex vertebral height increased from 17.7 ± 1.9mm to 19.8 ± 1.5mm (p < 0.001), while mean individual concave height increased from 14.8 ± 1.9mm to 17.6 ± 1.6mm (p < 0.001). Summing the peri-apical heights, the difference in height from pre-operative to 4-year follow-up was greater on the concave (8.3 ± 4.7mm) than on the convex side (6.2 ± 4.7mm) (p < 0.001). Mean individual vertebral wedging decreased from 6 ± 2° at pre-operative to 4 ± 2° at 4-year follow-up (p < 0.001). Mean total vertebral and disc wedging started at 29 ± 7° pre-operatively, decreased to 16 ± 6° at post-operative (p < 0.001), then further decreased to 14 ± 8° at 4-year follow-up (p < 0.001). Patients with open triradiate cartilages at the time of surgery had a larger height change over the 4years compared to those with closed triradiate cartilages (p < 0.001). Patients with idiopathic scoliosis treated with VBT demonstrated differential vertebral growth which was maintained at minimum 4-year follow-up. This effect was more pronounced in patients whose triradiate cartilages were open at the time of surgery. III.

Morphological alterations of lumbar intervertebral discs in patients with adolescent idiopathic scoliosis

BACKGROUND CONTEXTEtiology of adolescent idiopathic scoliosis (AIS) is still unknown. Prior in vitro research suggests intervertebral disc pathomorphology as a cause for the initiation and progression of the spinal deformity, however, this has not been well characterized in vivo. PURPOSETo quantify and compare lumbar disc health and morphology in AIS to controls. STUDY DESIGN/SETTINGCross-sectional study. METHODSAll lumbar discs were imaged using a 3T MRI scanner. T2-weighted and quantitative T2* maps were acquired. Axial slices of each disc were reconstructed, and customized scripts were used to extract outcome measurements: Nucleus pulposus (NP) signal intensity and location, disc signal volume, transition zone slope, and asymmetry index. Pearson's correlation analysis was performed between the NP location and disc wedge angle for AIS patients. ANOVAs were utilized to elucidate differences in disc health and morphology metrics between AIS patients and healthy controls. α=0.05. RESULTSThere were no significant differences in disc health metrics between controls and scoliotic discs. There was a significant shift in the NP location towards the convex side of the disc in AIS patients compared to healthy controls, with an associated increase of the transition zone slope on the convex side. Additionally, with increasing disc wedge angle, the NP center migrated towards the convex side of the disc. CONCLUSIONSThe present study elucidates morphological distinctions of intervertebral discs between healthy adolescents and those diagnosed with AIS. Discs in patients diagnosed with AIS are asymmetric, with the NP shifted towards the convex side, which was exacerbated by an increased disc wedge angle. CLINICAL SIGNIFICANCEInvestigation of the MRI signal distribution (T2w and T2* maps) within the disc suggests an asymmetric pressure gradient shifting the NP laterally towards the convexity. Quantifying the progression of these morphological alterations during maturation and in response to treatment will provide further insight into the mechanisms of curve progression and correction, respectively.

Posterior spinal fusion with lowest instrumented vertebra at L4 in idiopathic scoliosis: optimizing radiographic outcomes using pre-operative flexibility radiographs.

In idiopathic scoliosis (IS), there is general agreement ending PSFs at L3 or more cranial is preferred to optimize spinal motion, and extending PSFs to L4 may be necessary; however, this may also cause coronal imbalance or caudal disc wedging post-operatively due to leveling of L4 tilt. The purpose of this study was to identify a pre-operative radiographic measurement, which can be used to quantify the optimal amount of L4 tilt for ideal post-operative radiographic alignment. The study was a retrospective analysis of IS patients who underwent PSF to L4, with minimum 2-year follow-up post-operatively. Optimal outcome was defined by coronal balance, and L4-5 and L5-S1 disc wedging. 44 patients (84% females, mean age 13.6years) were included. Analysis of pre-operative flexibility radiographs determined only the L5 tilt on the right side-bending (RSB) radiograph correlated with optimal outcome 2 (p = 0.03). To confirm the validity, the RSB value was subtracted from the post-operative C7-L4 tilt and the odds ratio analysis which was significantly correlated with optimal outcome 1 at final follow-up (OR 1.04, 95% CI 1-1.09). In PSF to L4 for IS, L5 tilt measured from the pre-operative supine RSB radiograph can be used to optimize radiographic outcomes. Matching the pre-operative L5 tilt on RSB radiograph by leaving L4 tilted at the end of the PSF construct during surgery, quantified by the C7-L4 acute angle tilt, appears to be a useful method to achieve the desired post-operative alignment.

Pre-operative parameters influencing vertebral body tethering outcomes: patient's characteristics play an important role in determining the outcomes at a minimum of 2 years post-op.

The aim of this study is to determine preoperative predictors of good radiographic outcomes in VBT patients at a minimum 2-year follow-up. From a single-center dataset, we reviewed patients who underwent VBT from January 2014 to November 2018. Data analysis included age, gender, Risser grade and biometric data. Radiographically, maximum Cobb angle, C-DAR and apical vertebral and disc wedging were measured preop and at a minimum 2-year follow-up. Patients were divided into two cohorts following two different outcome measures: (1) vertebral growth modulation, those patients that growth modulated or corrected ≥ 5° and those who did not; and (2) Maximum Cobb angle at 2years, < and ≥ 40°. Student T and Chi2 tests were used for comparison and a multiple linear correlation test was implemented between statistically significant variables. 79 patients were recruited. 26 patients (33%) did growth modulate their spine at 2-year follow-up. These patients were significantly younger, and more skeletally immature with less height (147cm vs 155cm;p < 0.0001), weight (38kg vs. 45kg;p = 0.0009) and BMI (17 vs 18.8;p = 0.0229) as those who did not. Multiple linear regression model with these variables resulted in a moderate correlation (r2 = 0.234). 67 patients (85%) finished at a 2-year follow-up with a maximum Cobb angle < 40°. These patients were also younger and skeletally immature. We found significant differences in outcome 2 regarding the average preoperative maximum Cobb angle (48.5° ± 9.5 vs. 59.1° ± 10), average C-DAR (7 ± 1.5 vs. 8.5 ± 2.1), average apical vertebral wedging (6.5° vs. 8.3°), average vertebral/disc wedging ratio (1.5 vs. 2.4) and the average immediate postoperative Cobb angle (25° vs. 38°). These variables predicted a 36% of the variation in final Cobb angle measurement at a 2-year follow-up (r2 = 0.362). Curve severity determined by a preoperative C-DAR, preoperative Cobb angles and immediate postoperative Cobb angle are significantly related to curves < 40° at a minimum 2-year follow-up, while the potential to growth modulate the spine is more dependent on skeletal maturity, lower body weight and lower BMI. These patients' characteristics should be considered preoperatively.

Clinical differences in preoperative symptoms and surgical outcomes between early and late-teen patients with Lenke type 5C adolescent idiopathic scoliosis.

This study aimed to compare the clinical features and postoperative outcomes in patients with Lenke type 5C AIS in the early and late teens. The study included eligible patients with AIS aged < 20years with Lenke type 5C curves who underwent selective thoracolumbar/lumbar (TL/L) fusion. The patients were divided into two groups according to the age: younger (11-15years) and older (16-19years). Demographic data, radiographic parameters, and 22-item scoliosis research society questionnaire (revised) (SRS-22r) scores were compared. Seventy-three (female: 69, male: 4, mean age: 15.1years) patients were included. There were 45 and 28 patients in the younger and older groups, respectively. The older group exhibited a significantly smaller TL/L curve than the younger group, whereas no between-group differences were identified regarding curve flexibility and fusion length. The change in coronal balance and subjacent disc angle from preoperative to 2years after surgery was significantly greater in the younger group, although each curve was equally corrected. Preoperative SRS-22r scores in the older group were significantly worse; however, they improved to the level of the younger group at 2years after surgery. Postoperative coronal malalignment was observed in six patients (21.4%) in the older group, whereas no cases in the younger group (p < 0.05). In patients with Lenke type 5C AIS, we showed that late teens had significantly worse SRS-22r scores than did early teens. Postoperative coronal malalignment was frequently observed in the late teens due to the reduced ability of compensation by subjacent disc wedging.

Dynamic Rod Constructs as the Preventive Strategy against Adjacent Segment Disease in Degenerative Lumbar Spinal Disorders: A Retrospective Comparative Cohort Study.

Adjacent segment degeneration (ASDe) and adjacent segment disease (ASDi) are potential long-term complications after lumbar fusion with rigid instrumentation. Dynamic fixation techniques (Topping-off) adjacent to the fused segments have been developed to curtail the risk of ASDe and ASDi. The current study sought to investigate whether the addition of dynamic rod constructs (DRC) in patients with preoperative degeneration in the adjacent disc was effective in reducing the risk of ASDi. A retrospective analysis was performed on clinical data of 207 patients with degenerative lumbar disorders (DLD) from January 2012 to January 2019, who underwent posterior transpedicular lumbar fusion (without Topping-off, NoT/O), and posterior dynamic instrumentation with DRC. Clinical and radiological outcomes were evaluated using Oswestry Disability Index (ODI), Visual Analogue Scale (VAS), and lumbar radiographs one, three, and 12 months postoperatively and annually. ASDe was defined as disc height collapse > 20% and disc wedging > 5. Patients with confirmed ASDe and aggravation of ODI > 20 or VAS score > 5 at final follow-up were diagnosed as ASDi. The Kaplan-Meier hazard method was used to estimate the cumulative probability of ASDi within 63 months of surgery. Over three years of follow-up, 65 patients in the NoT/O (59.6%) and 52 cases (53.1%) in the DRC groups met the diagnostic criteria for ASDe. Furthermore, 27 (24.8%) patients in the NoT/O group showed ASDi during the follow-up, compared to 14 (14.3%) cases in the DRC group (P=0.059). Revision surgery was performed on 19 individuals in the NoT/O and 8 cases in the DRC groups (P=0.048). The Cox regression model identified a significantly decreased risk of ASDi if DRC was used (Hazard ratio: 0.29; 95% CI: 0.13-0.6). Dynamic fixation adjacent to the fused segment is an effective strategy for preventing ASDi in carefully selected individuals with preoperative degenerative changes at the adjacent level.

Predictors of Vertebral Endplate Fractures after Oblique Lumbar Interbody Fusion.

Cage subsidence after oblique lumbar interbody fusion (OLIF) induces restenosis and adversely affects patient outcomes. Many studies have investigated the causes of subsidence, one of which is endplate fracture (EF). This study aimed to identify predictors of EF after OLIF. This retrospective study reviewed consecutive patients who underwent OLIF at a single institute between August 2019 and February 2022. A total of 104 patients were enrolled. The patients' demographic data and surgical details were collected through chart reviews. Radiographic variables were measured. Related variables were also analyzed using binomial logistic regression, dividing each group into those with versus without EF. EF occurred at 30 of 164 levels (18.3%), and the binary logistic analysis revealed that sex (odds ratio [OR], 11.07), inferior endplate concave depth (OR, 1.95), disc wedge angle (OR, 1.22), lumbar lordosis (OR, 1.09), pelvic incidence (OR, 1.07), sagittal vertical axis (OR, 1.02), sacral slope (OR, 0.9), L3-4 level (OR, 0.005), and L4-5 level (OR, 0.004) were significantly related to EF. OLIF in older Asian patients should be performed carefully after recognizing the high possibility of EF and confirming the factors that should be considered preoperatively.

Is the Zero-P Spacer Suitable for 3-Level Anterior Cervical Discectomy and Fusion Surgery in Terms of Sagittal Alignment Reconstruction: A Comparison Study with Traditional Plate and Cage System.

The Zero-P spacer was primarily developed aiming to reduce the morbidity associated with the traditional anterior cervical plate. During the past decade, many authors have reported the use of Zero-P spacers for anterior cervical discectomy and fusion (ACDF) of one or two segments. Nevertheless, there is still a paucity of knowledge on the safety and feasibility of using Zero-P spacers for 3-level fixation. The objective of this study was to investigate the clinical and radiological outcomes, with a focus on the sagittal alignment reconstruction of 3-level ACDF surgery using Zero-P spacers versus those using a traditional plate and cage system. From Sep 2013 to Aug 2016, a total of 44 patients who received 3-level ACDF surgery due to cervical spondylotic myelopathy were recruited. The Zero-P spacer was used in 23 patients (group ZP) and the traditional plate and cage system in 21 (group PC). Clinical outcomes were analyzed by Neck Disability Index (NDI) and Japanese Orthopedic Association (JOA) scores, and dysphagia was evaluated using the Bazaz score. Radiological outcomes, including fusion rate, adjacent segment degeneration (ASD), and especially changes in cervical sagittal alignment, were analyzed. The NDI and JOA scores did not differ significantly between the two groups postoperatively (p &gt; 0.05); however, there was significantly less dysphagia in patients using Zero-P spacers at the 3- and 6-month follow-up (p &lt; 0.05). At the 24-month follow-up, the fusion rate and ASD were similar between the two groups (p &gt; 0.05). Interestingly, patients using Zero-P spacers had a significantly lower postoperative C2-7 Cobb angle and fused segment Cobb angle, compared to those using a traditional plate and cage system (p &lt; 0.05); meanwhile, the fused segment disc wedge was also found to be significantly smaller in patients using Zero-P spacers after surgery (p &lt; 0.05). Moreover, we further divided patients into subgroups according to their cervical lordosis. In patients with a preoperative C2-7 Cobb angle ≤ 10°, significantly less cervical and local lordosis, as well as disc wedge, were seen in group ZP after surgery (p &lt; 0.05), while in others with a preoperative C2-7 Cobb angle &gt; 10°, no significant difference in postoperative changes of the cervical sagittal alignment was seen between group ZP and group PC (p &gt; 0.05). Zero-P spacers used in 3-level ACDF surgery could provide equivalent clinical outcomes and a lower rate of postoperative dysphagia, compared to the traditional plate and cage system. However, our results showed that it was inferior to the cervical plate in terms of sagittal alignment reconstruction for 3-level fixation. We recommend applying Zero-P spacers for 3-level ACDF in patients with good preoperative cervical lordosis (C2-7 Cobb angle &gt; 10°), in order to restore and maintain physiological curvature of the cervical spine postoperatively.

Dual-Rod Instrumentation Via the Anterior Approach for Thoracolumbar and Lumbar Adolescent Idiopathic Scoliosis

Background: Posterior spinal fusion with pedicle screw instrumentation is currently the standard technique for spinal surgery. However, the anterior approach remains useful for thoracolumbar and lumbar (TL/L) lesions, such as in adolescent idiopathic scoliosis (AIS) 1–4 and spinal injuries 5,6 . We previously documented that long-term radiographic findings and clinical measures were satisfactory in patients with TL/L AIS treated with anterior dual-rod instrumentation 1 . Description: This surgical technique is indicated for single TL/L (Lenke 5) curves and is performed with use of extrapleural retroperitoneal approaches. The extrapleural cavity is connected to the retroperitoneal space by diaphragmatic transection. The lateral aspect of the vertebral bodies is exposed by retracting the psoas major muscle posteriorly from the intervertebral discs. Segmental vascular bundles are divided with coagulation and/or ligation. Care should be taken to reflect the psoas in its entirety and avoid an intramuscular approach to prevent bleeding injury to nerves, including the femoral, ilioinguinal, and genitofemoral nerves, as well as ureteral injury. After the intervertebral discs and cartilage plates are removed to the vertebral end plates, 2 screws are inserted in each vertebral body through a vertebral staple 1,4 . The anterior rod is then placed in the screw heads and rotated anteriorly, providing 3-dimensional correction of kyphotic deformities with lordosis production 1,4 . After the posterior rod is applied in the same manner as the anterior rod, compression forces are applied between the screws to correct scoliosis 1,4 . The compression force is first applied to the posterior rod so that kyphosis can be corrected more effectively 1,4 . Alternatives: Posterior pedicle screw instrumentation techniques are widely utilized for TL/L AIS curve correction. However, anterior techniques have frequently also been applied to the curve. Dwyer et al. 7 first reported the use of anterior spinal fusion (ASF) with a single braided cable connecting vertebral screws for the treatment of TL/L AIS, and Zielke et al. 8 modified that procedure by replacing the cable with a threaded rod. Although these instrumentation techniques and other single anterior rod techniques such as the Texas Scottish Rite Hospital System effectively correct scoliosis in the coronal plane and improve vertebral derotation 1,9 , poor sagittal and rotational plane deformity correction, implant weakness, and high incidence of pseudarthrosis remain unresolved issues 1 . Rationale: The fundamental advantages of the anterior approach in dual-rod instrumentation are the ability to achieve 3-dimensional correction with extremely low rates of pseudarthrosis and implant failure 1,10–12 . Furthermore, the fusion is expected to include fewer motion segments than with posterior systems (usually 1 level less distally and proximally). However, low skeletal maturity and a TL/L to thoracic Cobb ratio of &lt;1.25 appeared to be important factors for postoperative curve progression of the thoracic coronal deformity following ASF for the treatment of Lenke 5 curves 1,13 . In addition, subjacent disc wedging may occur when the subjacent disc is nearly parallel before surgery 1,14 . Expected Outcomes: The described technique is expected to provide 3-dimensional spinal correction. In a previous study, 30 patients with Lenke 5 AIS were followed for a mean of 17 years 1 . The mean TL/L Cobb angle correction rate and correction loss were 79.8% and 3.4°, respectively, at the time of the latest follow-up 1 . The average percent of predicted forced vital capacity and of forced expiratory volume in 1 second were 91.8% and 81.8%, respectively 1 . The average total score on the Scoliosis Research Society-30 outcome instrument was 4.21. No instrumentation failure, pseudarthrosis, or clinically relevant neurovascular complications were observed 1 . Important Tips: This technique is applicable to Lenke 5 AIS curves. However, the anterior approach can also be utilized for other TL/L lesions.The anterior procedure is accomplished via extrapleural retroperitoneal approaches with diaphragmatic transection.Care should be taken to reflect the psoas in its entirety and avoid an intramuscular approach to prevent bleeding and nerve and ureteral injuries. Acronyms &amp; Abbreviations: SRS-30 = Scoliosis Research Society-30

Changes in the lumbar intervertebral foramen between supine and standing posture in patients with adult spinal deformity: a study with upright computed tomography.

To quantitatively assess the impact of supine and standing positions on the morphological changes in the lumbar intervertebral foramen (LIF) in patients with adult spinal deformity (ASD) using upright CT and conventional supine CT. Thirty patients with ASD were prospectively enrolled in this study. All subjects underwent standing whole spine posterior/anterior radiographs, lateral radiographs, and whole spine CT, both in the supine and upright standing positions. Two orthopedic surgeons independently measured nine radiographic parameters in the radiograph and the lumbar foraminal area (FA) and height (FH) in supine and upright CT. Statistical analyses were performed to evaluate the risk of LIF decrease when standing upright compared to the supine position. The chi-squared, t test, Pearson's coefficients, intra- and inter-rater reliabilities, and ROC curves were calculated. The level of significance was set at p < 0.05. Among the 300 LIFs, both the lumbar FA and FH were either increased or decreased by > 5% in approximately 30% of LIFs each. The FA decreased in the lower lumbar spine. The concave side had a significantly higher rate of decreased FA and FH than the convex side (p < 0.05 and < 0.05, respectively). ROC analysis showed that narrowing of the intervertebral disc (cutoff > 0.05°) is a risk factor for decreased FA and FH. This study describes the details of the changes in the neuroforamen using a novel upright CT. In patients with ASD, approximately 30% of LIFs either increased or decreased in size by > 5% when standing. The risk factors for LIF decrease are the lower lumbar spine, concave side, and narrow side of the disc wedge.

Reliability of radiographic assessment of growth modulation from anterior vertebral body tethering surgery in pediatric scoliosis.

To assess the reliability of vertebral height and angular measurements for anterior vertebral body tethering (AVBT). Eight observers measured PA radiographs of 15 idiopathic scoliosis patients treated with AVBT, pre-operative and 4-year follow-up. Vertebral wedging, disc wedging, convex vertebral body heights, and concave vertebral body heights of the 3 apical vertebrae were measured. For each observer, there were a total of 90 measurements for vertebral body height and 75 measurements for all wedging types At least 14days elapsed between first and second round measurements. From the pre-operative to the 4-year follow-up time-point, the total wedging angle over the 3 peri-apical levels fell from 30 ± 7° to 16 ± 6° (p < 0.001) and the difference between the convex and concave vertebral heights decreased from 9 ± 4 to 6 ± 3mm (p < 0.001). Interobserver agreement for pre-operative vertebral body heights was good [ICC = 0.80; 95% CI (0.74-0.85)]. At 4-year follow-up there was a moderate agreement [ICC = 0.67 (0.59-0.74)]. There was a poor interobserver agreement for pre-operative wedging angle measurements [ICC = 0.41 (0.32-0.52)] and 4-year follow-up [ICC = 0.45 (0.36-0.56)]. The Limits of Agreement with the Mean (LOAM) for pre-op heights was ± 2.4mm, similar to the follow-up ± 2.6mm. When raters are averaged in random groups of two the agreement limits decrease to ± 1.8mm pre-op and ± 1.6mm at follow-up. Similarly for wedging angles, LOAM values among the 8 observers of ± 4.6° pre-op and ± 4.2° dropped to ± 2.7° for both pre-op and follow-up when random groups of two raters were averaged together. Intraobserver agreement ranged from good to excellent per individual (ICC = 0.84-0.94) for pre-operative vertebral body heights, but this decreased at 4-year follow-up (ICC = 0.52-0.88). Intraobserver agreement was low overall for wedging (pre-operative ICC = 0.41-0.71; 4-year follow-up ICC = 0.41-0.76). Based on 8 individual observers, interobserver agreement ranged from good (pre-operative vertebral body heights) to moderate (4-year follow-up vertebral body heights) to poor (all wedging angles). To improve the reliability of the measurement of wedging angles, we recommend averaging the measurements of at least two observers.

Prediction of post-operative adding-on or compensatory lumbar curve correction after anterior vertebral body tethering.

Anterior Vertebral Body Tethering (AVBT), a fusionless surgical technique based on growth modulation, aims to correct pediatric scoliosis over time. However, medium-term curvature changes of the non-instrumented distal lumbar curve remains difficult to predict. The objective was to biomechanically analyze the level below the LIV to evaluate whether adding-on or compensatory lumbar curve after AVBT can be predicted by intervertebral disc (ID) wedging and force asymmetry. 33 retrospective scoliotic cases instrumented with AVBT were used to computationally simulate their surgery and 2-year post-operative growth modulation using a finite element model. The cohort was divided into two subgroups according to the lumbar curvature evolution over 2years: (1) correction > 10° (C); (2) maintaining ± 10° (M). The lumbar Cobb angle and residual ID wedging angle under LIV were measured. Simulated pressures and moments at the superior endplate of LIV + 1 were post-processed. These parameters were correlated at 2years postoperatively. On average, the LIV + 1 simulated moment was 538Nmm for subgroup C, 155Nmm for subgroup M with lumbar Cobb angle > 20° and 34Nmm for angle < 20° whereas the ID angle was 1° for C and 0° for M. On average, a positive moment on the LIV + 1 superior growth plate led to correction of the lumbar curvature, whereas a null moment kept it stable, and a parallel immediate postoperative ID under LIV contributed to its correction or preservation. Nevertheless, the significant interindividual variability suggested that other parameters are involved in the distal non-instrumented curvature evolution. IV.

A Newer Way of Determining LIV in AIS Patients: Rotation of the Touched Vertebrae

A retrospective review. The objective of this study was to determine whether fusing to touched vertebra (TV) on prone x-rays (XRs) with minimal rotation (Gd 0/1) allow for shorter fusion with optimal correction. Previous studies have shown risk of "adding on" when TV is not selected as lowest instrumented vertebra (LIV). Fusion proximal to TV leads to suboptimal results but fusing to TV on standing XRs can result in longer fusions. On lying down XRs, TV moves proximally, and its rotation decreases by a grade. TV patients with minimal rotation were selected on prone (TVP) or standing XRs (TVS). Patients fused to rotated (Gd 2+) TV on standing or prone XRs were considered touched vertebra rotated (TVR). In the non-TV (NTV) group, LIV was fused proximal to TV. Disk wedging ≥5° determined risk of "adding-on." To compare patients fused to minimally rotated TV, to those that were not, patients in group A (TVP + TVS) were compared with group B (TVR + NTV).In part II: TVP, TVS, TVR, and NTV patients were compared. Subanalysis compared levels saved as the difference between predicted and real LIV in TVP and TVS patients. Another subanalysis was carried out for Lenke 1+2 and Lenke 3, 4, 5.In part III: XRs of nonoperative adolescents idiopathic scoliosis patients with Cobb <30 and Risser 4/5 were analyzed to determine "acceptable" end vertebra tilt and disc wedging and served as controls. There were a significantly greater number of patients in group B patients(TVR + NTV) with final disk wedging ≥5°, final LIV translation ≥1 and ≥2cm ( P <0.001).Utilizing prone XRs in TVP saved average 1 level, and 1.2 levels in TVS patients. TVP patients also had similar LIV tilt, disk wedging and coronal balance( P >0.05) to controls. Choosing minimally rotated (Gd 0/1) TV on prone XR saves levels without sacrificing radiographic outcomes.

Ten-year follow-up of Lenke 5 curves treated with spinal fusion.

Patients with surgically treated Lenke 5 curves require at least partial fusion of the lumbar spine. The implications of lumbar fusion remain unknown as long-term follow-up is sparse. A retrospective review of a prospectively collected registry of patients with Lenke 5 curves treated with spinal fusion was performed. Clinical and radiographic outcomes as well as SRS-22 scores were collected at 2- and 10-year follow-up. 54 of 247 available patients met all inclusion criteria [26 treated with posterior spinal fusion (PSF) and 28 with anterior spinal fusion (ASF)]. Preoperative lumbar curve magnitude was 45.1 ± 8.4° and corrected to 14.0 ± 7.2° (p < 0.001). A 3.3 ± 7.3° increase in curve size was noted at final follow-up (p < 0.008) with 20.3% of patients having a loss of correction (LOC)of 10° or more. Thoracic curve correction and kyphosis were stable at 10-year follow-up. End vertebrae angulation improved from 11.2 ± 23.2° to 0.96 ± 6.4° (p = 0.004) and translation improved from 2.5 ± 2.9 to 0.92 ± 1.5cm (p = 0.008) with no LOC. Disc wedging below the lower instrumented vertebrae increased from 0.3 ± 4.9° to 2.8 ± 4.4° (p < 0.001) with no change at 10years. SRS-22 self-image and satisfaction improved from post-operative to final follow-up. No patient required a second operation. Both ASF and PSF showed durable results at 10-year follow-up with no obvious difference between approaches. 20% of patients had a LOC > 10°; this did not correlate with pain or need for revision surgery. Disc wedging was stable. Selection of LIV did not correlate with pain scores. Level III.

Influence on lowest instrumented vertebra disc wedging by thoracolumbar/lumbar and thoracic Cobb ratio (TL/L:T Cobb ratio) after selective lumbar fusion in patients with adolescent idiopathic scoliosis Lenke type 5

Influence on lowest instrumented vertebra disc wedging by thoracolumbar/lumbar and thoracic Cobb ratio (TL/L:T Cobb ratio) after selective lumbar fusion in patients with adolescent idiopathic scoliosis Lenke type 5

Characteristics analysis of segmental and regional lumbar spontaneous compensation post thoracic fusion in Lenke 1 and 2 adolescent idiopathic scoliosis

ObjectiveTo explore the characteristics of compensation of unfused lumbar region post thoracic fusion in Lenke 1 and 2 adolescent idiopathic scoliosis.BackgroundPreserving lumbar mobility in the compensation is significant in controlling pain and maintaining its functions. The spontaneous correction of the distal unfused lumbar curve after STF has been widely reported, but previous study has not concentrated on the characteristics of compensation of unfused lumbar region post thoracic fusion.MethodA total of 51 Lenke 1 and2 AIS patients were included, whose lowest instrumented vertebrae was L1 from January 2013 to December 2019. For further analysis, demographic data and coronal radiographic films were collected before surgery, at immediate erect postoperatively and final follow-up. The wedge angles of each unfused distal lumbar segments were measured, and the variations in each disc segment were calculated at the immediate postoperative review and final follow-up. Meanwhile, the unfused lumbar curve was divided into upper and lower parts, and we calculated their curve angles and compensations.ResultsThe current study enrolled 41 females (80.4%) and 10 males (19.6%). Thirty-six patients were Lenke type 1, while 15 patients were Lenke type 2. The average main thoracic Cobb angle and thoracolumbar/lumbar Cobb angle were 44.1 ± 7.7°and 24.1 ± 9.3°, preoperatively. At the final follow-up, the disc wedge angle variation of L1/2, L2/3, L3/4, L4/5 and L5/S1 was 3.84 ± 5.96°, 3.09 ± 4.54°, 2.30 ± 4.53°, − 0.12 ± 3.89° and − 1.36 ± 2.80°, respectively. The compensation of upper and lower coronal lumbar curves at final follow-up were 9.22 ± 10.39° and − 1.49 ± 5.14°, respectively.ConclusionWhen choosing L1 as the lowest instrumented vertebrae, the distal unfused lumbar segments’ compensation showed a decreasing trend from the proximal end to the distal end. The adjacent L1/2 and L2/3 discs significantly contributed to this compensation.

Paraspinal myopathy-induced intervertebral disc degeneration and thoracolumbar kyphosis in TSC1mKO mice model—a preliminary study

BACKGROUNDIncreasing kyphosis of the spine in a human is a well-recognized clinical phenomenon that has been associated with back pain, poor physical performance and disability. The pathophysiology of age-related kyphosis is complex and has been associated with physiological changes in vertebrae, intervertebral disc (IVD) and paraspinal musculature, which current cross-sectional studies are unable to demonstrate. Creating an in vivo, paraspinal myopathic animal model for longitudinal study of these changes under controlled conditions is thus warranted. PURPOSETo confirm the TSC1 gene knockout effect on paraspinal muscle musculature; to analyze the development of spinal kyphosis, IVD degeneration and vertebra structural changes in a longitudinal manner to gain insights into the relationship between these processes. STUDY DESIGNA prospective cohort study of 28 female mice, divided into 4 groups—9-month-old TSC1mKO (n=7), 9-month-old control (n=4), 12-month-old TSC1mKO (n=8), and 12-month-old controls (n=9). METHODSHigh resolution micro-computed tomography was used to measure sagittal spinal alignment (Cobb's angle), vertebral height, vertebral body wedging, disc height index (DHI), disc wedge index (DWI), histomorphometry of trabecular bone and erector spinae muscle cross-sectional area. Paraspinal muscle specimens were harvested to assess for myopathic features with H&E stain, muscle fiber size, density of triangular fiber and central nucleus with WGA/DAPI stain, and percentage of fibers with PGC-1α stain. Intervertebral discs were evaluated for disc score using FAST stain. RESULTSCompared to controls, paraspinal muscle sections revealed features of myopathy in TSC1mKO mice similar to human sarcopenic paraspinal muscle. While there was significantly greater presence of small triangular fiber and density of central nucleus in 9-and 12-month-old TSC1mKO mice, significantly larger muscle fibers and decreased erector spinae muscle cross-sectional area were only found in 12-month-old TSC1mKO mice compared to controls. TSC1mKO mice developed accelerated thoracolumbar kyphosis, with significantly larger Cobb angles found only at 12 months old. Structural changes to the trabecular bone in terms of higher bone volume fraction and quality, as well as vertebral body wedging were observed only in 12-month-old TSC1mKO mice when compared to controls. Disc degeneration was observed as early as 9 months in TSC1mKO mice and corresponded with disc wedging. However, significant disc height loss was only observed when comparing 12-month-old TSC1mKO mice with controls. CONCLUSIONSThis study successfully shows the TSC1 gene knockout effect on the development of paraspinal muscle myopathy in a mouse which is characteristic of sarcopenia. The TSC1mKO mice is by far the best model available to study the pathological consequence of sarcopenia on mice spine. With paraspinal muscle myopathy established as early as 9 months, TSC1mKO mice developed disc degeneration and disc wedging. This is followed by kyphosis of the spine at 12 months with concomitant disc height loss and vertebral body wedging due to bone remodeling. Age-related bone loss was not found in our study, suggesting osteoporosis and myopathy-induced vertebral body wedging are likely two independent processes. CLINICAL SIGNIFICANCEThis is the first study to provide key insights on the early and late consequences of paraspinal myopathy on intervertebral disc degeneration, spinal kyphosis, and vertebral body changes. With this new understanding, future studies evaluating therapies for spinal degeneration may be performed to develop time-sensitive interventions.

MORPHOMETRY OF LUMBAR INTERVERTEBRAL DISC WEDGE ANGLE, DISC HEIGHT AND CONCAVITY INDEX IN NORMAL SPINES

BACKGROUND: The lordotic wedging and height of the presacral disc avert detrimental loads and shearing of the lumbar spine. Age and functional degenerations affect these causing spinal disarrays frequently requiring lumbar reconstructive surgery. Reinstating the disc height and wedging to its optimum healthy state is essential for accomplished spinal rehabilitation. The fourth and fth lumbar segments being most predisposed to mechanical pathophysiology and surgical interventions were evaluated in a north-east Indian population. MATERIALS &amp; METHOD: The disc wedge angle, vertebral and disc heights and concavity index were measured in eighty lumbar segments comprising of twenty males and twenty females. RESULTS: The disc-wedge angle, anterior, middle, posterior disc heights and concavity index were as follows: 12.06±1.67°, 12.27±1.25mm,10.83±1.04mm,6.95±0.77mm,0.90±0.01at L4/L5 and 15.65±1.83°, 15.15±1.67mm, 11.32±1.68mm, 6.79±0.79mm, 0.90±0.01 at L5/S1 in males and 13.02±1.66°, 13.03±1.30mm, 11.86±1.23mm, 6.44±0.95mm,0.90±0.01 at L4/L5 and 16.89±1.71°,36.40 ±1.29mm, 16.04± 1.62mm, 12.31± 1.77mm, 6.06±0.94mm and 0.088 ± 0.02 in females. CONCLUSION: The disc wedge angles and anterior and middle disc heights were signicantly higher in females while the vertebral and posterior disc heights and convexity index were larger in males. The larger lordotic wedging of L5/S1 intervertebral disc preserves the spinal conformation. All above dimensions decreased with age in both genders. Our study standardizes quantitative referral data for research, diagnosis and prothesis to resolve the existing discordances.