Effects of Bone Cross-Link Bridging on Fracture Mechanism and Surgical Outcomes in Elderly Patients with Spine Fractures.

STUDY DESIGN: This study adopted a cross-sectional study design. PURPOSE: This study was designed to investigate the effects of bone cross-link bridging on fracture mechanism and surgical outcomes in vertebral fractures using the maximum number of vertebral bodies with bony bridges between adjacent vertebrae without interruption (maxVB). OVERVIEW OF LITERATURE: The complex interplay of bone density and bone bridging in the elderly can complicate vertebral fractures, necessitating a better understanding of fracture mechanics. METHODS: We examined 242 patients (age >60 years) who underwent surgery for thoracic to lumbar spine fractures from 2010 to 2020. Subsequently, the maxVB was classified into three groups: maxVB (0), maxVB (2-8), and maxVB (9-18), and parameters, including fracture morphology (new Association of Osteosynthesis classification), fracture level, and neurological deficits were compared. In a sub-analysis, 146 patients with thoracolumbar spine fractures were classified into the three aforementioned groups based on the maxVB and compared to determine the optimal operative technique and evaluate surgical outcomes. RESULTS: Regarding the fracture morphology, the maxVB (0) group had more A3 and A4 fractures, whereas the maxVB (2-8) group had less A4 and more B1 and B2 fractures. The maxVB (9-18) group exhibited an increased frequency of B3 and C fractures. Regarding the fracture level, the maxVB (0) group tended to have more fractures in the thoracolumbar transition region. Furthermore, the maxVB (2-8) group had a higher fracture frequency in the lumbar spine area, whereas the maxVB (9-18) group had a higher fracture frequency in the thoracic spine area than the maxVB (0) group. The maxVB (9-18) group had fewer preoperative neurological deficits but a higher reoperation rate and postoperative mortality than the other groups. CONCLUSIONS: The maxVB was identified as a factor influencing fracture level, fracture type, and preoperative neurological deficits. Thus, understanding the maxVB could help elucidate fracture mechanics and assist in perioperative patient management.

Incidence and predictive factors of shoulder imbalance after selective anterior spinal fusion surgery in Lenke type 5C adolescent idiopathic scoliosis.

Background: No study has assessed the incidence or predictors of postoperative shoulder imbalance (PSI) in patients with Lenke type 5C adolescent idiopathic scoliosis (AIS) who underwent selective anterior spinal fusion (ASF). This study evaluated the incidence and predictors of shoulder imbalance after selective ASF for Lenke type 5C AIS. Methods: In total, 62 patients with Lenke type 5C AIS (4 men and 58 women, mean age at surgery of 15.5 ± 1.5 years) were included and divided into the following two groups according to the radiographic shoulder height (RSH) at the final follow-up: PSI and non-PSI groups. All patients in this study underwent a whole-spine radiological evaluation. Various spinal coronal and sagittal profiles on radiographs were compared between the 2 groups. The clinical outcomes were assessed using the Scoliosis Research Society (SRS)-22 questionnaires. Results: The mean final follow-up duration was 8.6 ± 2.7 years. PSI was observed in 10 patients (16.1%) immediately after surgery; however, in the long-term follow-up period, PSI improved in 3 patients spontaneously, whereas the remaining 7 patients had residual PSI. The preoperative RSH and correction rates of the major curve immediately after surgery or at the final follow-up were significantly larger in the PSI group than in the non-PSI group (p=.001, p=.023, and p=.019, respectively). Receiver operating characteristic curve analysis indicated that the cutoff values for preoperative RSH and the correction rates immediately after surgery and at the final follow-up were 11.79 mm (p=.002; area under the curve [AUC], 0.948), 71.0% (p=.026; AUC, 0.822), and 65.4% (p=.021; AUC, 0.835), respectively. No statistically significant difference was observed in the preoperative and final follow-up SRS-22 scores in any domain between the PSI and non-PSI groups. Conclusions: Paying attention to the preoperative RSH and avoiding excessive correction of the major curve can prevent the occurrence of shoulder imbalance after selective ASF for Lenke type 5C AIS.

Reduction Capacity and Factors Affecting Slip Reduction Using Cortical Bone Trajectory Technique in Transforaminal Lumbar Interbody Fusion for Degenerative Spondylolisthesis.

Introduction: Vertebral slip reduction has been recommended in arthrodesis for lumbar degenerative spondylolisthesis (LDS) to achieve balanced spinal alignment and bone fusion. However, what determines the degree of slip reduction using cortical bone trajectory technique for lumbar pedicle screw insertion is yet to be determined. Thus, in this study, we aim to investigate the slip reduction capacity using cortical bone trajectory (CBT) technique and to identify factors affecting the slip reduction rate. Methods: This is a retrospective radiological evaluation of prospectively collected patients. In total, 49 consecutive patients who underwent single-level transforaminal lumbar interbody fusion for LDS using the CBT technique were included (mean follow-up: 28.9 months). Firstly, radiological parameters of fused segment including the percentage of anterior vertebral slip (%slip), lordotic angle, and disk height were measured. Then, patient and procedure-related parameters were examined to determine factors related to the slip reduction rate using multiple regression analysis. Results: The %slip was reduced from 15.0±4.8 to 1.6±2.3% immediately after surgery and 2.2±2.9% at the last follow-up (p<0.01), with a slip reduction rate of 87.5±15.7% and correction loss of 0.6±2.1%. As per multivariate regression analysis, it was found that preoperative %slip (standardized regression coefficient [ß]=-0.55, p=0.003) and the depth of screw insertion in the caudal vertebra (ß=0.38, p=0.03) were significant independent factors affecting slip reduction rate (adjusted R2=0.29, p=0.008). Conclusions: To the best of our knowledge, this study is the first to investigate the capacity for and factors affecting slip reduction using the CBT technique for LDS. The CBT technique may be a useful option for achieving slip reduction, and the depth of screw insertion in the caudal vertebra was identified as a significant technical factor to obtain a more significant reduction of slipped vertebra.

Normal pressure hydrocephalus due to an iatrogenic giant lumbar pseudomeningocele after posterior lumbar interbody fusion: illustrative case.

BACKGROUND: Iatrogenic pseudomeningocele incidence after lumbar surgery is 0.068%-2%, and most lumbar pseudomeningoceles are smaller than 5 cm; however, in rare cases, "giant" pseudomeningoceles greater than 8 cm in size may develop. Normal pressure hydrocephalus (NPH) is another rare condition in which the ventricles expand despite the presence of normal intracranial pressure. To date, pseudomeningocele associated with NPH has not been reported. OBSERVATIONS: An 80-year-old woman underwent L3-5 laminectomy and posterior lumbar interbody fusion, and her symptoms improved after surgery. However, dementia appeared 1 month after surgery. Repeated brain computed tomography showed ventricular enlargement, and lumbar magnetic resonance imaging showed a long pseudomeningocele in the subcutaneous tissues at the L4 level. Here, the authors report a rare case of an iatrogenic giant pseudomeningocele accompanied by NPH after lumbar surgery. The symptoms of NPH in the present case occurred after spinal surgery and recovered after dural repair surgery, indicating that the changes in cerebrospinal fluid circulation and/or pressure due to pseudomeningoceles may cause NPH. LESSONS: The prevention of dural tears through precise surgical technique and primary repair of dural tears are the best approaches to prevent pseudomeningocele incidence and subsequent events.

Radiological comparison of penetrating endplate trajectory versus anterior bicortical trajectory for sacral pedicle screw insertion in posterior lumbosacral interbody fusion.

BACKGROUND: The bicortical or tricortical fixation technique with purchase into the anterior sacral wall or promontory has been recommended to achieve rigid sacral pedicle screw fixation, which carries the potential risk of neurovascular injuries. The penetrating endplate screw (PES) technique was proposed as an alternative screw trajectory to facilitate both strong fixation and safety. However, there has been no report on the practical significance of using the PES technique. The aim of the present study was to investigate radiological outcomes using the PES technique for lumbosacral fusion by comparing it with the anterior bicortical technique. METHODS: The subjects consisted of 44 patients with L5 isthmic spondylolisthesis who underwent single-level posterior lumbar interbody fusion at L5-S using the PES technique (20 patients) or the anterior bicortical technique (24 patients) and were followed up for > 2 years (mean follow-up: 36.6 months). Screw loosening and bone fusion were radiologically assessed and compared between the two groups. Factors contributing to bone fusion were investigated using the following factors: (1) age, (2) sex, (3) body mass index, (4) bone mineral density, (5) screw diameter, (6) screw length, (7) pelvic incidence, (8) crosslink connector, (9) cage material, and (10) sacral screw insertion technique. RESULTS: Respective screw loosening and bone fusion rates were 10.0 and 90.0% using the PES technique and 29.2 and 79.2% using the anterior bicortical technique, with no significant differences between the two techniques. Multivariate logistic regression analysis revealed that the age (odds ratio = 0.87, p = 0.02) and PES technique (odds ratio = 22.39, p = 0.02) were significant independent factors contributing to bone fusion. CONCLUSIONS: This is the first study to demonstrate the significance of using the PES technique to improve radiological outcomes. The PES technique could be a valid option for lumbosacral fixation for L5 isthmic spondylolisthesis in terms of improved bone fusion.

Selective Anterior Fusion Surgery Does Not Influence Global Spinal Sagittal Alignment in Lenke Type 5 Adolescent Idiopathic Scoliosis Patients.

STUDY DESIGN: Retrospective comparative study. OBJECTIVE: The aim of this study was to evaluate the changes in global spinal sagittal alignment (GSSA) following selective anterior spinal fusion (ASF) in patients with Lenke type 5 adolescent idiopathic scoliosis (AIS). SUMMARY OF BACKGROUND DATA: Few studies have assessed the changes in postoperative GSSA, including cervical, thoracic, and lumbosacral sagittal alignment in AIS patients with major thoracolumbar/lumbar (TL/L) curve who underwent selective ASF. METHODS: Fifty-two patients with Lenke type 5 AIS (two males and 50 females, mean age at surgery of 16.4 ±â€Š3.1 years) were included in this study. The average final follow-up was 8.3 ±â€Š3.1 years after surgery. The variations of outcome variables were analyzed in various spinal sagittal profiles using radiographic outcomes (pre-operation, immediate post-operation, and final follow-up). The clinical outcomes at the final follow-up were assessed using Scoliosis Research Society (SRS)-22 and Oswestry Disability Index (ODI) questionnaires. RESULTS: The mean Cobb angle of the main TL/L and minor thoracic curve was significantly improved after selective ASF, which was maintained up to the final follow-up. However, in all cases, the various sagittal parameters examined (sagittal vertical axis [SVA], C2-7 SVA, C2-7 lordosis, T1 slope, thoracic kyphosis, T10-L2 kyphosis, lumbar lordosis, pelvic incidence, pelvic tilt, and sacral slope), did not significantly change in the immediate postoperative period, and all GSSA parameters were maintained up to the final follow-up. Furthermore, the magnitude of coronal curve correction and fused levels did not affect each GSSA parameter postoperatively. During the period up to the final follow-up, no significant clinical symptoms were observed. The final SRS-22 global score was 4.5 ±â€Š0.3, and ODI scored 0.8 ±â€Š2.4. CONCLUSION: Selective ASF did not influence various GSSA parameters postoperatively and could maintain excellent correction for coronal deformity with satisfactory final functional and clinical outcomes confirmed by long-term follow-up.Level of Evidence: 4.

Depth of vertebral screw insertion using a cortical bone trajectory technique in lumbar spinal fusion: radiological significance of a long cortical bone trajectory.

OBJECTIVE: Contrary to original cortical bone trajectory (CBT), "long CBT" directed more anteriorly in the vertebral body has recently been recommended because of improved screw fixation and load sharing within the vertebra. However, to the authors' knowledge there has been no report on the clinical significance of the screw length and screw insertion depth used with the long CBT technique. The aim of the present study was to investigate the influence of the screw insertion depth in the vertebra on lumbar spinal fusion using the CBT technique. METHODS: A total of 101 consecutive patients with L4 degenerative spondylolisthesis who underwent single-level posterior lumbar interbody fusion at L4-5 using the CBT technique were included (mean follow-up 32.9 months). Screw loosening and bone fusion were radiologically assessed to clarify the factors contributing to these outcomes. Investigated factors were as follows: 1) age, 2) sex, 3) body mass index, 4) bone mineral density, 5) intervertebral mobility, 6) screw diameter, 7) screw length, 8) depth of the screw in the vertebral body (%depth), 9) facetectomy, 10) crosslink connector, and 11) cage material. RESULTS: The incidence of screw loosening was 3.1% and bone fusion was achieved in 91.7% of patients. There was no significant factor affecting screw loosening. The %depth in the group with bone fusion [fusion (+)] was significantly higher than that in the group without bone fusion [fusion (-)] (50.3% ± 8.2% vs 37.0% ± 9.5%, respectively; p = 0.001), and multivariate logistic regression analysis revealed that %depth was a significant independent predictor of bone fusion. Receiver operating characteristic curve analysis identified %depth > 39.2% as a predictor of bone fusion (sensitivity 90.9%, specificity 75.0%). CONCLUSIONS: This study is, to the authors' knowledge, the first to investigate the significance of the screw insertion depth using the CBT technique. The cutoff value of the screw insertion depth in the vertebral body for achieving bone fusion was 39.2%.

Factors important in bone union after posterior lumbar interbody fusion using the cortical bone trajectory technique.

BACKGROUND: The cortical bone trajectory (CBT) technique has developed as an alternative to the traditional pedicle screw fixation technique due to its minimum invasiveness for screw insertion and rigid fixation for posterior lumbar interbody fusion (PLIF). However, the factors contributing to bone union after CBT-PLIF is a controversial subject. The aim of this study was to investigate factors important to bone union after CBT-PLIF. METHODS: We analyzed 69 consecutive patients who underwent single-level CBT-PLIF from October 2011 to December 2016 and were followed for over two years. Bone union was evaluated using computed tomography (CT) and dynamic assessment in the radiograph within two years after CBT-PLIF. The following factors that may influence bone union were investigated: age, gender, bone mineral density (BMD), cage materials [polyether-ether-ketone (PEEK) or titanium (Ti)], vertebral-slip (neutral), translational motion (flexion/extension), angular motion (flexion/extension), screw depth into the vertebral body (% depth), interval of bilateral screw heads, and cage position. RESULTS: The bone union rate at the two-year follow-up was 88.4% (61/69). A univariate analysis revealed that variables with values of P<0.20 were age (P<0.01), gender (P=0.07), cage material (P=0.18), vertebral slip (neutral) (P=0.14), % depth (P=0.086), and cage position (P<0.01). Multiple logistic regression analyses revealed that factors related to bone union were young age (P<0.01), Ti cage (P<0.01), small vertebral slip (neutral) (P<0.01), high % depth (P<0.01), and anterior cage position (P<0.01). CONCLUSIONS: For CBT-PLIF, deeper screw insertion into the vertebral body, anterior cage placement, and Ti cage usage may be important surgical techniques to achieve a successful bone union.

Regional Hounsfield unit measurement of screw trajectory for predicting pedicle screw fixation using cortical bone trajectory: a retrospective cohort study.

BACKGROUND: The sufficiency of screw anchoring is a critical factor for achieving successful spinal fusion; however, no reliable method for predicting pedicle screw fixation has been established. Recently, Hounsfield units (HU) obtained from computed tomography (CT) was developed as a new reliable tool to determine the bone quality. The purpose of the present study was to demonstrate the utility of regional HU measurement of the screw trajectory to predict the primary and long-term fixation strength of pedicle screws. METHOD: The insertional torque of pedicle screws using the cortical bone trajectory technique was measured intraoperatively in 92 consecutive patients who underwent single-level posterior lumbar interbody fusion. The cylindrical area of each screw was plotted on the preoperative CT image by precisely confirming the screw position, and the screw trajectory was measured in HU. First, three parameters: the bone mineral density (BMD) of the femoral neck and lumbar vertebrae, and regional HU values of the screw trajectory, were correlated with the insertional torque and compared among three groups. Next, pedicle screw loosening was evaluated by postoperative CT obtained 12 months after surgery, and clinical and imaging data were analyzed to assess whether regional HU values could be used as a predictor of screw loosening. RESULTS: Regional HU values of the screw trajectory (r = 0.75, p < 0.001) had stronger correlation with the insertional torque than the femoral BMD (r = 0.59, p < 0.001) and lumbar BMD (r = 0.55, p < 0.001). The incidence of screw loosening was 4.6% (16/351). Multivariate logistic regression analysis revealed that regional HU value (odds ratio = 0.70; 95% confidence interval = 0.56-0.84; p = 0.018) was an independent risk factor significantly affected screw loosening. CONCLUSIONS: Regional HU values of the screw trajectory could be a strong predictor of both primary and long-term screw fixation in vivo.