Halo-gravity traction in the treatment of severe spinal deformity: a systematic review and meta-analysis.

PURPOSE: Halo-gravity traction has been reported to successfully assist in managing severe spinal deformity. This is a systematic review of all studies on halo-gravity traction in the treatment of spinal deformity to provide information for clinical practice. METHODS: A comprehensive search was conducted for articles on halo-gravity traction in the treatment of spinal deformity according to the PRISMA guidelines. Appropriate studies would be included and analyzed. Preoperative correction rate of spinal deformity, change of pulmonary function and prevalence of complications were the main measurements. RESULTS: Sixteen studies, a total of 351 patients, were included in this review. Generally, the initial Cobb angle was 101.1° in the coronal plane and 80.5° in the sagittal plane, and it was corrected to 49.4° and 56.0° after final spinal fusion. The preoperative correction due to traction alone was 24.1 and 19.3%, respectively. With traction, the flexibility improved 6.1% but postoperatively the patients did not have better correction. Less aggressive procedures and improved pulmonary function were observed in patients with traction. The prevalence of traction-related complications was 22% and three cases of neurologic complication related to traction were noted. The prevalence of total complications related to surgery was 32% and that of neurologic complications was 1%. CONCLUSION: Partial correction could be achieved preoperatively with halo-gravity traction, and it may help decrease aggressive procedures, improve preoperative pulmonary function, and reduce neurologic complications. However, traction could not increase preoperative flexibility or final correction. Traction-related complications, although usually not severe, were not rare.

Sagittal spinal alignment in asymptomatic patients over 30 years old in the Korean population.

BACKGROUND: We aim to provide sagittal and pelvic parameters according to different age groups in an asymptomatic population all over 30 years old and to investigate the possible causes of changes in these parameters. METHODS: Whole-spine, standing lateral radiographs were taken in 128 asymptomatic Korean people over 30 years old. The spinal parameters (the total thoracic kyphosis (TTK), maximal lumbar lordosis (MLL), total lumbar lordosis (TLL), lower lumbar lordosis (LLL), thoracolumbar junctional angle (TLJA), and lumbar inclination (LI)), pelvic parameters (pelvic incidence (PI), sacral slope (SS), and pelvic tilt (PT)), and spinal balance parameters (spinal balance, sacropelvic balance, and spinopelvic balance) were measured. The body mass index, body protein mass, waist line, skeletal muscle mass, and body fat mass were also measured for potential causes. RESULTS: TTK and TLJA were significantly increased in the group over 70 years of age compared to the other age groups (p = 0.0002, <0.001). TLL was significantly decreased in the group over 70 years of age (p = 0.002), whereas the PI values were similar to PI even in over 70-year age group. LLL did not differ in the group over 70 years of age (p = 0.29), gradually increasing with an increase in age. SS was significantly decreased and PT was significantly increased in the group over 70 years of age as compared to the other age groups (p = 0.049, 0.049, respectively). PI was similar in all age groups (p = 0.75). Spinal balance was significantly decreased in the group over 70 years of age (p = <0.0001). PT was significantly associated with body protein mass and skeletal muscle mass (p = 0.01, 0.001, respectively). Body protein mass and skeletal muscle mass were significantly lower in the group over 70 years of age (p = 0.02, 0.02) and were possible causes. CONCLUSIONS: Several sagittal and pelvic parameters are different in asymptomatic adults over 70 years of age. Decreased body protein mass and skeletal muscle mass are possible causes of these changes.

Posterior vertebral column resection in spinal deformity: a systematic review.

PURPOSE: This study aimed to assess the amount of correction and risk of complications of posterior vertebral column resection (PVCR) in the treatment of spinal deformity. METHODS: A comprehensive research was conducted in MEDLINE, EMBASE and Cochrane Database of Systematic Reviews for published articles about PVCR in spinal deformity. Data from these included studies were pooled with the help of the Review Manager software from the Cochrane Collaboration and the R software. The amount of correction of PVCR was indicated with change of coronal and sagittal Cobb angle after operation. Risk of complications was demonstrated with prevalence. RESULTS: 7 studies, a total of 390 patients, were included for analysis. The average operative time for PVCR was 430 min and the estimated blood loss was 2,639 ml. The mean amount of correction by PVCR was 64.1° in scoliosis and 58.9° in kyphosis, accounting a correction rate of 61.2 and 63.1 %, respectively. As to coronal and sagittal imbalance, data were limited. The overall prevalence of complications of PVCR was 32 % (95 % CI 12-54 %). The most common was neurologic complications, estimated to be 8 % (95 % CI 2-16 %). And risk of spinal cord injury was 2 % (95 % CI 0-3 %). The revision rate was 6 % (95 % CI 1-13 %). Incidence of infection was pooled to be 2 % (95 % CI 1-4 %). Complication rate related with implant was 2 % (95 % CI 0-6 %). CONCLUSION: PVCR is a powerful surgical procedure for severe spinal deformity. However, it has the risk of excessive blood loss and major complications. Decision of PVCR should be prudent and the procedure should be performed by an experienced surgical team.

Modified iliac screw fixation: technique and clinical application.

BACKGROUND: A conventional iliac bolt and the S2 alar iliac screw fixation technique (S2AI) are commonly used sacropelvic fixation techniques. However, conventional iliac bolt technique requires a lateral connector and commonly has prominent screw head problems. S2AI reportedly has a high instrument failure rate. We aim to introduce a modified iliac screw fixation technique and to investigate its clinical application in adult patients. METHODS: The entrance site of the modified iliac screw fixation technique was 1 cm medial and 1 cm caudal from the posterosuperior iliac spine. From 2009 to 2015, ten adult patients underwent sacropelvic fixation with the modified iliac screw fixation technique in our spine clinic. A minimum 12-month clinical and radiographic follow-up was adopted. The mean follow-up period was 30.7 months (12-74 months). Mean number of fixation levels was 7.7 segments (5-10 segments). RESULTS: Postoperatively, the C7 plumb line (SVA) was significantly decreased (P = 0.04). Upon the last X-ray, SVA did not differ between postoperative and the last X-ray (P = 0.1). There was no breakage during our follow-up period. There was no prominent screw head. There were no cases requiring implant removal. CONCLUSIONS: The modified iliac screw fixation technique does not cause prominence in the sacral region, and does not require a lateral connector, both of which are necessary when using the classical iliac bolt technique. This technique also avoids the acute angle between the screw head and the shaft of the screw commonly seen in S2AI. The modified iliac screw fixation technique can be an effective alternative for sacropelvic fixation.

Risk of rod fracture according to cross-link position in pedicle subtraction osteotomy (PSO): A finite element study.

PURPOSE: The purpose of this study is to investigate the effect of the cross-link position on the rod fracture phenomenon during pedicle subtraction osteotomy (PSO) surgery using finite element model (FEM). METHODS: A three-dimensional finite element model of a lumbar spine with sagittal imbalance was constructed using computed tomography data of a 65-year-old female patient. After simulating the standard PSO at the L4 level, we constructed four models, specifically a model without a cross-link and three models with a cross-link at three different sites. The peak von Mises stress (PVMS) of the rod around the PSO site was measured after applying physiological loads (flexion, extension, axial rotation, and lateral bending) in each model. RESULTS: The measured PVMS outcomes at the PSO site were 135.8, 135.9, 208.9, and 384.7 MPa for model 1, 2, 3, and 4 during flexion, and 180.0, 180.1, 210.1, and 445.7 MPa during extension. These results show that when the cross-link is located at the PSO site, the rod stress at the PSO site increases significantly during flexion and extension. As the cross-link moved away from the PSO site, the effect on the rod stress decreased. When the cross-link was placed two levels away from the PSO site, the rod stress was scarcely affected. CONCLUSION: When the cross-link during PSO surgery was positioned two levels away from the PSO site, the risk of rod fracture did not increase.

Cross-link is a risk factor for rod fracture at pedicle subtraction osteotomy site: A finite element study.

BACKGROUND: We aim to investigate using finite element model (FEM) whether the use of a cross-link is a risk factor for rod fracture at the pedicle subtraction osteotomy (PSO) site. METHODS: The geometry and dimensions of the FEM were obtained from a high-resolution computed tomography scan data of a 65 years old female patient with spinal sagittal imbalance. The intact model was modified to place PSO on the L4 spine. A cross-link was placed at the PSO site. A multisegment spinal fusion model from L1 to the pelvis was used to compare and analyze the peak von Mises stress (PVMS) values of the implants. A compressive follower load of 400 N was added to the validated intact lumbar spinal model in the follower load path direction. RESULTS: After PSO surgery, the PVMS of the rod was significantly increased during flexion and extension at the PSO site. With the cross-link at the PSO site, the PVMS of the rod was further significantly increased during flexion and extension. CONCLUSION: The cross-link at the PSO site increased the risk of rod facture, especially during flexion and extension stress.

Biomechanical characterization of three iliac screw fixation techniques: A finite element study.

We aim to characterize the biomechanical properties of a modified iliac screw fixation method compared with the classic iliac screw fixation and the S2 alar iliac screw (S2AI) fixation using a FEM. A three-dimensional, non-linear FEM of lumbosacral spine and pelvis (L1-pelvis) was modified to simulate 3 different iliac screw fixations based on posterior screw fusion. The peak von Mises stress (PVMS) values of the iliac screws in the 3 different iliac screw fixations were recorded in during flexion/extension/axial rotation/lateral bending. The interaction stress which arose between the screw head and the shaft of iliac screws, was also measured for each case. The PVMS values of the 3 different iliac screw fixation techniques were lower than the fatigue strength levels under physiological loadings. PVMS of iliac screws was observed in the screw shaft for S2AI, in the screw neck for the modified iliac screw technique, and in the offset connectors of the classic iliac screw technique. The interaction between the screw head and the neck was compressed in modified iliac screw fixation technique. On the other hand, distraction force was observed in the S2AI technique between the screw head and the screw shaft. This FEM study supports our previous clinical results, which found that the modified iliac screw fixation technique can be an effective alternative sacropelvic fixation technique comparable to the classic iliac screw and the S2AI technique.