Transpedicular grafting after short-segment pedicle instrumentation for thoracolumbar burst fracture: calcium sulfate cement versus autogenous iliac bone graft

Posterior pedicle screw fixation combined with transpedicular bone grafting for treatment of single-level thoracolumbar fractures with the aid of a vertebroplasty tool

OBJECTIVE

This study was performed to assess the efficacy of a novel tool to assist transpedicular bone grafting in short-segment pedicle screw fixation combined with pedicle fixation at the level of the fractured vertebra (six-screw fixation).

METHODS

We retrospectively analyzed 80 patients (40 in the control group and 40 in the tool-aided group) with single-level thoracolumbar fractures. Patients in the control group underwent traditional six-screw fixation combined with transpedicular bone grafting. In the tool-aided group, we introduced a novel vertebroplasty tool to assist transpedicular bone grafting. Basic information and related indicators were recorded.

RESULTS

There were no significant differences in the patients' baseline characteristics or surgical outcomes between the control group and tool-aided group. Both traditional surgery and tool-aided surgery restored the height of the fractured vertebrae and decreased the Cobb angle, visual analog scale score, and Oswestry Disability Index. However, tool-aided surgery more effectively restored the height of the fractured vertebrae and reduced the visual analog scale score and Oswestry Disability Index than did traditional surgery.

CONCLUSION

Vertebroplasty tool-aided surgery facilitated more precise and successful grafting of bone into damaged vertebrae than did traditional surgery and therefore might be recommended for treating single-level thoracolumbar fractures.

Better vertebrae remodeling in pediatric spinal eosinophilic granuloma patients treated with kyphoplasty and short-term posterior instrumentation: A minimal two-year follow-up with historical controls

OBJECTIVE

To assess the validity and safety of kyphoplasty combined with short-term posterior instrumentation to treat children with vertebrae plana due to eosinophilic granuloma (EG).

PATIENTS AND METHODS

Clinical data of EG patients, who received kyphoplasty and short-term instrumentation from March 2019 to March 2020, were retrospectively reviewed. The recovery of diseased vertebrae was assessed and compared with historical case data.

RESULTS

Nine patients with EG had received kyphoplasty and short-term posterior instrumentation. The mean age at initial treatment was 66.7 months old (range, 28-132 months). The average number of follow-up months was 26.7. (range, 24-30 months).Four and 5 cases presented with thoracic and lumbar vertebral destruction, respectively. Under Garg's classification, 7 and 2 cases were classified as Grade IIA and IIB, respectively. The average diseased vertebral heights at 1-year and 2-year after surgery were significantly higher than the preoperative heights. The average percentages of diseased vertebral heights to references at 1-year and 2-year after surgery were 72.0% and 86.0%, respectively. The average percentage of diseased vertebral heights to the references at 2-year after surgery was significantly higher than that of the historical cases at the same time. No minor or major adverse events were observed.

CONCLUSIONS

Transpedicular balloon kyphoplasty for the direct restoration of vertebrae plana seems feasible and safe in combination with short-term posterior instrumentation. Better short-time vertebrae remodeling was observed 2 years after surgery. Active surgical treatment is suggested for children who have vertebrae plana as a result of EG in order to maintain the ability to recover vertebral height.

Improved Anti-Washout Property of Calcium Sulfate/Tri-Calcium Phosphate Premixed Bone Substitute with Glycerin and Hydroxypropyl Methylcellulose

Calcium sulfate/calcium phosphate (CS-CP)-based bone substitutes have been developed in premixed putty for usage in clinical applications. However, it is difficult to completely stop the bleeding during an operation because premixed putty can come into contact with blood or body fluids leading to disintegration. Under certain conditions depending on particle size and morphology, collapsed (washed) particles can cause inflammation and delay bone healing. In this context, anti-washout premixed putty CS-CP was prepared by mixing glycerin with 1, 2, and 4 wt% of hydroxypropyl methylcellulose (HPMC), and the resultant anti-washout properties were evaluated. The results showed that more than 70% of the premixed putty without HPMC was disintegrated after being immersed into simulated body fluid (SBF) for 15 min. The results demonstrated that the more HPMC was contained in the premixed putty, the less disintegration occurred. We conclude that CS-CP pre-mixed putty with glycerin and HPMC is a potential bone substitute that has good anti-washout properties for clinical applications.

[Surgical treatment of delayed spinal cord injury caused by atypical compression of old thoracolumbar fractures]

OBJECTIVE

To explore the clinical characteristics and surgical treatment strategies of delayed spinal cord injury (SCI) caused by atypical compression of old thoracolumbar fracture.

METHODS

Between January 2011 and June 2018, 32 patients with delayed SCI caused by atypical compression of old thoracolumbar fracture who met the inclusion criteria were admitted and divided into group A (20 cases, underwent anterior subtotal vertebral body resection+titanium mesh reconstruction+screw rod internal fixation) and group B (12 cases, underwent posterior 270° ring decompression of vertebral canal+titanium mesh reconstruction+screw rod internal fixation) according to the different operation approaches. There was no significant difference between the two groups in age, gender, cause of injury, fracture segment, disease duration, preoperative American Spinal Injury Association (ASIA) classification, and preoperative back pain visual analogue scale (VAS) score, lumbar Japanese Orthopaedic Association (JOA) score, kyphosis angle, and vertebral canal occupational ratio ( P>0.05). The incision length, operation time, intraoperative blood loss, complications, and bone fusion time of reconstructed vertebrae were recorded and compared between the two groups; the kyphosis angle, back pain VAS score, and lumbar JOA score were used to evaluate the effectiveness.

RESULTS

Except that the incision length in group A was significantly shorter than that in group B ( t=-4.865, P=0.000), there was no significant difference in intraoperative blood loss and operation time between the two groups ( P>0.05). There was no deaths or postoperative paraplegia cases in the two groups, and no deep infection or skin infection occurred. There was 1 case of cerebrospinal fluid leakage, 1 case of inferior vena cava injury, and 1 case of chyle leakage in group A. No serious complications occurred in group B. There was no significant difference in the incidence of complications between the two groups ( P=0.274). All 32 patients were followed up 12-61 months, with an average of 20.8 months. The follow-up time for groups A and B were (19.35±5.30) months and (23.25±12.20) months respectively, and the difference was not significant ( t=-1.255, P=0.219). The reconstructed vertebrae in all cases obtained bony fusion postoperatively. The fusion time of groups A and B were (8.85±2.27) months and (8.50±2.50) months respectively, and the difference was not significant ( t=0.406, P=0.688). The kyphosis angle, back pain VAS score, and lumbar JOA score of the two groups at each time point after operation and last follow-up were significantly improved when compared with preoperatively ( P<0.05); the lumbar JOA score was further improved with time postoperatively ( P<0.05), while the kyphosis angle and the VAS score of back pain remained similarly ( P>0.05). Comparison of kyphosis angle, back pain VAS score, and lumbar JOA score between the two groups at various time points postoperatively showed no significant difference ( P>0.05). At last follow-up, the JOA score improvement rate in groups A and B were 83.87%±0.20% and 84.50%±0.14%, respectively, and the difference was not significant ( t=-0.109, P=0.914); the surgical treatment effects of the two groups were judged to be significant.

CONCLUSION

In the later stage of treatment of old thoracolumbar fractures, even mild kyphosis and spinal canal occupying may induce delayed SCI. Surgical correction and decompression can significantly promote the recovery of damaged spinal cord function. Compared with anterior approach surgery, posterior approach surgery has the advantages of less trauma, convenient operation, and fewer complications, so it can be preferred.

Clinico-Radiological Efficacy of Posterior Instrumentation, Decompression, and Transpedicular Bone Grafting in Osteoporotic Burst Fracture Associated with Neurological Deficit

Objective

The aim of this study is to evaluate clinico-radiological outcomes of posterior surgery (decompression + instrumentation + transpedicular bone graft) in osteoporotic burst fracture associated with neurological deficit [OFND].

Materials and Methods

Forty patients with neurological deficit due to delayed osteoporotic vertebral collapse managed by posterior surgery (decompression + instrumentation + transpedicular bone graft) with minimum 2 years follow-up were included in the study. Approval from the Institutional Review Board was taken. Demographic data (age, sex, mode of injury, and the severity of osteoporosis); clinical parameters (Visual Analog Score [VAS], Oswestry Disability Index [ODI], Frankel grade), radiological parameters (local kyphosis), and surgical variables (blood loss, surgery duration, and intraoperative events) were recorded. Neurological worsening/improvement, complications, and implant failures were noted.

Results

Significant improvement was noted in VAS (preoperative 8.20 ± 0.65/postoperative 4.1 ± 0.64) and ODI (preoperative 76.54 ± 6.96/postoperative 30.5 ± 6.56). Complete neurological recovery was noted in 37 patients (Frankel Grade E), three patients remained nonambulatory (Frankel Grade C). Significant improvement was noted in local kyphosis angle (preoperative = 21.80 ± 2.70; postoperative 11.40 ± 1.80), with 10% loss of correction (2.5 ± 0.90) at final follow-up. Symptomatic implant failure was noted in two patients and proximal junctional failure in one patient requiring an extension of fixation.

Conclusions

OFND can be managed with a single posterior-only surgery with significant improvement in neurology and functional scores of patients. Aggressive kyphosis correction is often not required and optimal correction of kyphosis is noticed due to prone-positioning alone. Transpedicular grafting is safe and simple alternative to cement augmentation or anterior surgery for collapsed vertebrae.

Short-Segment Instrumentation with Fractured Vertebrae Augmentation by Screws and Bone Substitute for Thoracolumbar Unstable Burst Fractures

BACKGROUND

For thoracolumbar burst fractures, traditional four-screw (one above and one below) short-segment instrumentation is popular and has a high failure rate. Additional augmentation at the fractured vertebrae is believed to reduce surgical failure. The purpose of this study was to examine the clinical and radiographic results of patients who underwent short-segment posterior instrumentation with augmentation by screws and bone substitutes at the fractured vertebrae and to compare these data to those of patients who underwent long-segment instrumentation for thoracolumbar burst fractures.

METHODS

The study group had twenty patients who underwent short-segment instrumentation with additional augmentation by two screws and bone substitutes at the fractured vertebrae. The control group contained twenty-two patients who underwent eight-screw long instrumentation without vertebra augmentation. Local kyphosis and the anterior body height of the fractured vertebrae were measured. The severity of the fractured vertebrae was evaluated with the load sharing classification (LSC). Any implant failure or loss of correction >10° at the final follow-up was defined as surgical failure.

RESULTS

Both groups had similar distributions in terms of age, sex, the injured level, and the mechanism of injury before operation. During the operation, the study group had significantly less blood loss (136.0 vs. 363.6 ml, p=0.001) and required shorter operating times (146.8 vs. 157.5 minutes, p=0.112) than the control group. Immediately after surgery, the study group had better correction of the local kyphosis angle (13.4° vs. 11.9°, p=0.212) and restoration of the anterior height (34.7% vs. 31.0%, p=0.326) than the control group. At the final follow-up, no patients in the study group and only one patient in the control group experienced surgical failure.

CONCLUSIONS

Patients with thoracolumbar burst fractures who received six-screw short-segment posterior fixators with augmentation at the level of the fractured vertebrae via injectable artificial bone substitute achieved satisfactory clinical and radiographic results, and this method could replace long-segment instrumentation methods used in unstable thoracolumbar burst fractures.

Efficacy of Vertebroplasty in Short-Segment Pedicle Screw Fixation of Thoracolumbar Fractures: A Meta-Analysis

BACKGROUND Short-segment pedicle screw instrumentation provides superior outcomes in treating thoracolumbar fractures. Nevertheless, the effect of intermediate screws on the outcome of short-segment instrumentation at the fracture level has not been specifically analyzed. We performed an update meta-analysis of the effect of additional vertebroplasty on the outcome of short-segment instrumentation to determine the role of screws for patients with fractured vertebra. MATERIAL AND METHODS A systematic literature search was conducted, updated to January 2019, in terms of the efficacy of additional vertebroplasty on the outcome of short-segment instrumentation at the fracture level. After rigorous quality review, we extracted the data from qualified clinical studies. We further analyzed odds ratios (ORs) of the endpoints of interest based on the included trials. RESULTS Compared with the control group, short-segmental fixation combined with intermediate screws restored Cobb angle (P<0.001) and reduced anterior vertebral height compression (P=0.001). However, our results did not reveal statistically significant differences in operative time (P=0.28) or estimated blood loss (P=0.23). A statistically significant difference was observed in mean hospital stay (P=0.02). CONCLUSIONS Reinforcement with fracture-level screw combination can help stabilize the fractures and restore the anatomy. Nevertheless, additional trials and studies with longer follow-ups and on larger populations are warranted to confirm the current findings.

Intermediate screws or kyphoplasty: Which method of posterior short-segment fixation is better for treating single-level thoracolumbar burst fractures?

PURPOSE

To compare intermediate screws (IS) with kyphoplasty (KP) in posterior short-segment fixation (PSSF) for patients with single-level thoracolumbar burst fractures.

METHODS

Between 2010 and 2016, 1465 patients were retrospectively reviewed; 48 patients were enrolled with a minimal follow-up of 2 years. Perioperative and functional outcomes were compared. The regional Cobb angle (CA) was included in radiographic analysis. Implant failures or CA correction loss over 10° were regarded as surgical failures. Multiple linear regression was performed to investigate the risk factors of kyphosis recurrence.

RESULTS

Fluoroscopic time (23.7 ± 3.6 vs. 79.3 ± 12.1 s, p < 0.001), operative time (109.6 ± 13.1 vs. 123.8 ± 19.0 min, p = 0.006) and blood loss (104.6 ± 34.9 vs. 129.1 ± 21.7 ml, p = 0.005) were all lower in the IS group. The KP group had lower Visual Analogue Scale scores (3.3 ± 0.9 vs. 2.7 ± 0.8, p = 0.028) and greater anterior body height (ABH) (30.3 ± 9.0 vs. 36.3 ± 11.0%, p = 0.044) after surgery, and less correction loss (5.6 ± 2.7 vs. 0.4 ± 1.2%, p < 0.001). Both groups had a CA correction loss of 4° with a 10% failure rate. The A3 Magerl subclassification, smaller preoperative ABH and smaller postoperative CA had positive correlations with CA correction loss.

CONCLUSION

PSSF with KP provides better back pain relief, greater ABH reduction and less correction loss, while IS has the advantages of less operative time, fluoroscopic time and blood loss. Magerl subclassification of burst fracture is a potential predictor for recurrent kyphosis. Reducing fractured vertebral body height rather than segmental curvature may be more important in PSSF.

STUDY DESIGN

Retrospective, non-randomized controlled study. These slides can be retrieved under Electronic Supplementary Material.

3D-printed IFN-γ-loading calcium silicate-β-tricalcium phosphate scaffold sequentially activates M1 and M2 polarization of macrophages to promote vascularization of tissue engineering bone

To promote vascularization of tissue-engineered bone, IFN-γ polarizing macrophages to M1 was loaded on 5% calcium silicate/β-tricalcium phosphate (CaSiO₃-β-TCP) scaffolds. IFN-γ and Si released from the scaffold were designed to polarize M1 and M2 macrophages, respectively. β-TCP, CaSiO₃-β-TCP, and IFN-γ@CaSiO₃-β-TCP were fabricated and biocompatibilities were evaluated. Polarizations of macrophages were detected by flow cytometry. Human umbilical vein endothelial cells with GFP were cultured and induced on Matrigel with conditioned culture medium extracted from culture of macrophages loaded on scaffolds for evaluating angiogenesis. Four weeks after the scaffolds were subcutaneously implanted into C57B1/6, vascularization was evaluated by visual observation, hematoxylin and eosin staining, as well as immunohistochemistry of CD31. The results showed that IFN-γ@CaSiO₃-β-TCP scaffolds released IFN-γ in the early stage (1-3 days) to stimulate macrophages to M1 polarization, followed by release of Si inducing macrophages to M2 polarization while scaffolds degraded. The activation of M1/M2 allows macrophages to secrete more cytokines, including VEGF, CXCL12 and PDGF-BB. The IFN-γ@CaSiO₃-β-TCP scaffolds formed more blood vessels in vitro and in vivo compared to the control groups. The study indicated that the design of tissue-engineered scaffolds with immunomodulatory function utilized host macrophages to increase vascularization of tissue-engineered bone, providing a new strategy for accelerating vascularization and osteogenesis of tissue-engineered scaffolds and showing the potential for treatment of major bone defects.

STATEMENT OF SIGNIFICANCE

A 3-D printed immunomodulatory scaffold was designed for repair of massive bone defects. Through the release of interferon γ and silicon ions, the new immunomodulatory scaffold promoted the M1 and M2 polarization of macrophages, boosting angiogenesis. This scaffold provided a new strategy for accelerating vascularization and osteogenesis of tissue-engineered scaffolds and showing the potential for treatment of major bone defects.

Biomechanical effects of different vertebral heights after augmentation of osteoporotic vertebral compression fracture: a three-dimensional finite element analysis

Background

Clinical results have shown that different vertebral heights have been restored post-augmentation of osteoporotic vertebral compression fractures (OVCFs) and the treatment results are consistent. However, no significant results regarding biomechanical effects post-augmentation have been found with different types of vertebral deformity or vertebral heights by biomechanical analysis. Therefore, the present study aimed to investigate the biomechanical effects between different vertebral heights of OVCFs before and after augmentation using three-dimensional finite element analysis.

Methods

Four patients with OVCFs of T12 underwent computed tomography (CT) of the T11-L1 levels. The CT images were reconstructed as simulated three-dimensional finite-element models of the T11-L1 levels (before and after the T12 vertebra was augmented with cement). Four different kinds of vertebral height models included Genant semi-quantitative grades 0, 1, 2, and 3, which simulated unilateral augmentation. These models were assumed to represent vertical compression and flexion, left flexion, and right flexion loads, and the von Mises stresses of the T12 vertebral body were assessed under different vertebral heights before and after bone cement augmentation.

Results

Data showed that the von Mises stresses significantly increased under four loads of OVCFs of the T12 vertebral body before the operation from grade 0 to grade 3 vertebral heights. The maximum stress of grade 3 vertebral height pre-augmentation was produced at approximately 200%, and at more than 200% for grade 0. The von Mises stresses were significantly different between different vertebral heights preoperatively. The von Mises stresses of the T12 vertebral body significantly decreased in four different loads and at different vertebral body heights (grades 0–3) after augmentation. There was no significant difference between the von Mises stresses of grade 0, 1, and 3 vertebral heights postoperatively. The von Mises stress significantly decreased between pre-augmentation and post-augmentation in T12 OVCF models of grade 0–3 vertebral heights.

Conclusion

Vertebral augmentation can sufficiently reduce von Mises stresses at different heights of OVCFs of the vertebral body, although this technique does not completely restore vertebral height to the anatomical criteria.

Vertebroplasty Using Allograft Bone Chips with Posterior Instrumented Fusion in the Treatment of Osteoporotic Vertebral Fractures with Neurological Deficits

Introduction

In general, osteoporotic vertebral fractures with neurological deficits require surgery. However, the ideal surgical method remains controversial. We evaluated the efficacy of combining posterior instrumented fusion and vertebroplasty using allograft bone chips.

Methods

Twelve patients (five men, seven women; age 68-84 years, mean age 75.9 years) with osteoporotic vertebral fractures with neurological deficits were reviewed retrospectively. They underwent posterior instrumented fusion and vertebroplasty, using allograft bone, at our institution between January 2007 and June 2016. We assessed the surgical results, radiologically and neurologically, after a mean follow-up of 37.3 months.

Results

The mean local kyphosis angle was 10° before surgery, −3.3° immediately after surgery, and 4.4° at follow-up. The average spinal canal compromise was 26.9% before surgery and 19.5% at follow-up. All patients achieved bony fusion and none needed additional surgery. All patients improved by at least one grade on the modified Frankel grading system.

Conclusions

Combining vertebroplasty, using allograft bone chips, and posterior instrumented fusion appears to be an effective option for osteoporotic vertebral fractures with neurological deficits.

Is additional balloon Kyphoplasty safe and effective for acute thoracolumbar burst fracture?

BACKGROUND

Burst fracture is a common thoracolumbar injury that is treated using posterior pedicle instrumentation and fusion combined with transpedicular intracorporeal grafting after reduction. In this study, we compared the outcome of these two techniques by using radiologic imaging and functional outcome.

METHODS

Sixty-one patients with acute thoracolumbar burst fracture were operated with kyphoplasty (n = 31) or vertebroplasty (n = 30) and retrospectively reviewed in our institution between 2011 and 2014. All 61 patients underwent surgery within 5 days after admission to the hospital and then followed-up for 12 to 24 months after surgery.

RESULTS

Significant improvement was found in the anterior vertebral height (92 ± 8.9% in the kyphoplasty group, 85.6 ± 7.2% in the vertebroplasty group, p < 0.01) at 1 month post-operatively and (89 ± 7.9% in the kyphoplasty group, 78 ± 6.9% in the vertebroplasty group, p < 0.01) at the 24-month follow-up. Significant improvement was also observed in the kyphotic angle (1.2 ± 0.5° in the kyphoplasty group, 10.5 ± 1.2° in the vertebroplasty group, p < 0.01) at 1 month post-operatively and (5.4 ± 1.2° in the kyphoplasty group, 11.5 ± 8.5° in the vertebroplasty group, p < 0.01) at the 24-month follow-up. Both operations led to significant improvement of the patients' pain and the Oswestry disability index (p < 0.01). Cement leakage was noted in 29% of patients after kyphoplasty and 77% of patients after vertebroplasty (p < 0.01). Only one implant failure (3.3%), which required further surgical intervention, was reported in the vertebroplasty group.

CONCLUSIONS

Reduction with additional balloon at the fractured site is better than indirect reduction only by posterior instrumentation. The better reduction of kyphotic angle and the lower cement leakage rate in the kyphoplasty group indicate that additional balloon kyphoplasty is safe and effective for acute thoracolumbar burst fracture.

Post-operative bracing after pedicle screw fixation for thoracolumbar burst fractures: A cost-effectiveness study

PURPOSE

While frequently prescribed to patients following fixation for spine trauma, the utility of spinal orthoses during the post-operative period is poorly described in the literature. In this study, we calculated rates of reoperation and performed a decision analysis to determine the utility of bracing following pedicle screw fixation for thoracic and lumbar burst fractures.

METHODS

Pubmed was searched for articles published between 2005 and 2015 for terms related to pedicle screw fixation of thoracolumbar fractures. Additionally, a database of neurosurgical patients operated on within the authors institution was also used in the analysis. Incidences of significant adverse events (wound revision for either dehiscence or infection or re-operation for non-union or instability due to hardware failure) were determined. Pooled means and variances of reported parameters were obtained using a random-effects, inverse variance meta-analytic model for observational data. Utilities for surgical outcome and complications were assigned using previously published values.

RESULTS

Of the 225 abstracts reviewed, 48 articles were included in the study, yielding a total of 1957 patients. After including patients from the institutional registry, together a total of 2081 patients were included in the final analysis, 1328 of whom were braced. Non-braced patients were older then braced patients, although this only approached significance (p=0.051). Braced patients had significantly lower rates of re-operation for non-union or clinically significant hardware failure (1.3% vs. 1.8%, p<0.001) although the groups had comparable rates of operative wound dehiscence and infection (p=1.000). These two approaches yielded comparable utility scores (p=0.120). Costs between braced and non-braced patients were comparable excluding the cost of the brace (p=0.256); hence, the added cost of the brace suggests that bracing post-operatively is not a cost effective measure.

CONCLUSIONS

Bracing following operative stabilization of thoracolumbar fracture does not significantly improve stability, nor does it increase wound complications. Moreover, our data suggests that post-operative bracing may not be a cost-effective measure.

Treatment of thoracolumbar burst fractures by short-segment pedicle screw fixation using a combination of two additional pedicle screws and vertebroplasty at the level of the fracture: a finite element analysis

Background

Traditional one-above and one-below four-screw posterior short-segment instrumentation is used for unstable thoracolumbar burst fractures. However, this method has a high rate of implant failure and early loss of reduction. The purpose of this study was to use finite element (FE) analysis to determine the effect of treating thoracolumbar burst fractures by short-segment pedicle screw fixation using a combination of two additional pedicle screws and vertebroplasty at the level of the fracture.

Methods

An intact T11-L1 spine FE model was created from the computed tomography images of a male subject. Four fixation models with posterior fusion devices (pedicle screws, rods, cross-link) were established to simulate an unstable thoracolumbar fracture with different fusion surgeries: short-segment fixation with: 1) a link (S-L); 2) intermediate bilateral screws (S-I); 3) a link and calcium sulfate cement (S-L-C); 4) intermediate bilateral screws and calcium sulfate cement (S-I-C). Different loading conditions (flexion, extension, lateral bending, and axial rotation) were applied on the models and analyzed with a FE package. The range of motion (ROM), and the maximum value and distribution of the implant stress, and the stress in the facet joint, were compared between the intact and fixation models.

Results

The ROM in flexion, extension, axial rotation, and lateral bending was the smallest in the S-I-C model, followed by the S-I, S-L-C, and S-L models. Maximum von Mises stress values were larger under lateral bending and axial rotation loadings than under flexion and extension loading. High stress was concentrated at the crosslink and rod junctions. Maximal von Mises stress on the superior vertebral body for all loading conditions was larger than that on the inferior vertebral body. The maximal von Mises stress of the pedicle screws during all states of motion were 265.3 MPa in S-L fixation, 192.9 MPa in S-I fixation, 258.4 MPa in S-L-C fixation, and 162.3 MPa in S-I-C fixation.

Conclusions

Short-segment fixation with two intermediate pedicle screws together with calcium sulfate cement at the fractured vertebrae may provide a stiffer construct and less von Mises stress of the pedicle screws and rods as compared to other types of short-segment fixation.

Two additional augmenting screws with posterior short-segment instrumentation without fusion for unstable thoracolumbar burst fracture - Comparisons with transpedicular grafting techniques

Background

Transpedicular grafting techniques with posterior short-segment instrumentation have demonstrated to prevent high implant failure in unstable thoracolumbar burst fractures. We tested our hypothesis that short-segment instrumentation with two additional augmenting screws in the injured vertebra could provide stability and was similar to those of the transpedicular grafting technique.

Methods

Twenty patients belonged to group A; treated with short-segment pedicle screw fixation and reinforced by two augmenting screws at the fractured vertebra. Group B had thirty-one patients; the fractured vertebra was augmented with transpedicular autogenous bone graft. Group C had twenty patients; the injured vertebra was strengthened with calcium sulfate cement. Clinical outcome and radiographic parameters were compared.

Results

Group A had the least blood loss (101.7 ± 72.5 vs. 600 ± 403.1 vs. 247.5 ± 164.2 ml, p < 0.001) and the least operation time (142.0 ± 57.2 vs. 227.2 ± 43.6 vs. 161.6 ± 28.5 min, p < 0.001). However, group A had the highest collapsed rate of the body height at the 18-month follow-up (10.5 ± 7.0 vs. 4.6 ± 4.8 vs. 7.2 ± 8.5%, p = 0.002). The failure rate, include implant failure or loss of 10° or more of correction, group B had the lowest failure rate (10% vs. 3.2% vs. 10%, p = 0.542). The group A had the highest rate of return to their previous employment (50% vs. 38% vs. 35%, p = 0.265).

Conclusions

Compared with transpedicular grafting techniques, additional two “augmenting screws” in the fracture vertebra with short-segment instrumentation are sufficient for one-level thoracolumbar burst fracture.

Posterior short-segment fixation in thoracolumbar unstable burst fractures - Transpedicular grafting or six-screw construct?

OBJECTIVES

Early implant failure and donor-site complication remain a concern in patients with thoracolumbar burst fracture underwent one-above and-below short-segment posterior pedicle screw fixation with fusion. Our aim was to evaluate the results of short-segment pedicle instrumentation enforced by two augmenting screws or injectable artificial bone cement in the fractured vertebra, and compare the differences between these two PATIENTS AND METHODS: We conducted a retrospective clinical and radiographic study. Twenty-seven patients were treated with a six-screw construct (group 1), and twenty-nine patients underwenta four-screw construct and fractured vertebra augmentation by injectable calcium sulfate/phosphate cement (group 2). Posterior or posterolateral fusions were not performed in both groups. The severity of the fractured vertebra was evaluated by the load-sharing classification (LSC). Local kyphosis and anterior body height of the fractured vertebra were measured and were follow-up at least 2 years. Any implant failure or loss of correction >10° degrees at the final was defined as failure of surgery. Patients' clinical results were assessed by the Denis scale.

RESULTS

Blood loss and operation time were less in group 1 (126.2±9.7 vs. 267.6±126.1ml, p<0.001 and 141.2±48.7 vs. 189.8±16.4min, p<0.001). Immediately after surgery, group 2 had a better local kyphosis angle (3.7±5.3 vs.6.0±4.1°, p=0.047) and acquired more anterior body height (94.9%±7.6% vs. 84.9%±10.0%, p<0.001). Both groups had similar clinical results (pain score: 1.5±0.8vs. 1.4±0.6, p=0.706; work score: 1.7±0.9 vs. 1.6±1.0, p=0.854). Group 1 had 3 cases of surgery failure; group 2 had 8 cases of implant failure (p=0.121). The average LSC score of these 11 patients with surgical failure was 7.2.

CONCLUSION

Thesix-screw construct had the advantage of shorter operating time, less blood loss, and lower failure rate. For those patients with anLSC score ≧7, posterior short-segment instrumentation should be used cautiously.

Improved Accuracy and Safety of Intracorporeal Transpedicular Bone Grafting - using Contrast Impregnated Bone: A Case Report

A method of transpedicular bone grafting using contrast impregnated bone to improve the visualization of bone graft on the image intensifier is reported. A - 36-year old man who had sustained traumatic burst fracture of T12 vertebra, with Load-Sharing Classification (LSC) score of 8, was treated with posterior short segment fusion from T11 to L1 with transpedicular bone graft of T12 vertebra. We were able to correct the kyphotic end plate angle (EPA) from 19º to 1.4º. Anterior bone graft augmentation was achieved with contrast enhaced transpedicular bone grafts. At six months follow up, CT scan showed good bony integration of the anterior column with EPA of 4.5º and two years later, radiographs showed EPA of 7.6 º.

Preparation and physical characterization of calcium sulfate cement/silica-based mesoporous material composites for controlled release of BMP-2

As a commonly used implant material, calcium sulfate cement (CSC), has some shortcomings, including low compressive strength, weak osteoinduction capability, and rapid degradation. In this study, silica-based mesoporous materials such as SBA-15 were synthesized and combined with CSC to prepare CSC/SBA-15 composites. The properties of SBA-15 were characterized by X-ray diffraction, transmission electron microscopy, and nitrogen adsorption-desorption isotherms. SBA-15 was blended into CSC at 0, 5, 10, and 20 wt%, referred to as CSC, CSC-5S (5% mass ratio), CSC-10S (10% mass ratio), and CSC-20S (20% mass ratio), respectively. Fourier-transform infrared spectroscopy and compression tests were used to determine the structure and mechanical properties of the composites, respectively. The formation of hydroxyapatite on composite surfaces was analyzed using scanning electron microscopy and X-ray diffraction after soaking in simulated body fluid. BMP-2 was loaded into the composites by vacuum freeze-drying, and its release characteristics were detected by Bradford protein assay. The in vitro degradation of the CSC/SBA-15 composite was investigated by measuring weight loss. The results showed that the orderly, nanostructured, mesoporous SBA-15 possessed regular pore size and structure. The compressive strength of CSC/SBA-15 increased with the increase in SBA-15 mass ratio, and CSC-20S demonstrated the maximum strength. Compared to CSC, hydroxyapatite that formed on the surfaces of CSC/SBA-15 was uniform and compact. The degradation rate of CSC/SBA-15 decreased with increasing mass ratio of SBA-15. The adsorption of BMP-2 increased and released at a relatively slow rate; the release rate of BMP-2 in CSC-20S was the slowest, and presented characteristics of low doses of release. In vitro experiments demonstrated that the physical properties of pure CSC incorporated with SBA-15 could be improved significantly, which made the CSC/SBA-15 composite more suitable for bone repair and bone-tissue engineering.

Short-segment posterior instrumentation combined with calcium sulfate cement vertebroplasty for thoracolumbar compression fractures: radiographic outcomes including nonunion and other complications

OBJECTIVE

To evaluate the radiographic outcomes of short-segment posterior instrumentation plus vertebroplasty using injectable calcium sulfate cement (CSC) for thoracolumbar compression fractures.

MATERIALS AND METHODS

Twenty-eight patients with a single-level thoracolumbar compression fracture, who underwent short-segment pedicle screw fixation and CSC vertebroplasty, were included in the study. The anterior vertebral body height ratio, local kyphosis angle, and the height of the intervertebral disc adjacent to the fractured vertebra were used to evaluate the radiographic results. Complications including bone nonunion, instrument failure, cement leakage, and disc vacuum formation were also assessed.

RESULTS

The patients were followed up for an average of 24.20±5.40 months. The relative preoperative anterior body height was 55.71±15.29%, which improved to 94.93±5.39% immediately after surgery (P<0.001), and at final follow-up showed a 6.50±3.89% loss of height correction (P<0.001). The mean preoperative local kyphosis angle was 22.23±5.65°, which corrected to 2.67±4.43° immediately after surgery (P<0.001), but reverted to 6.71±4.95° at final follow-up, showing a 4.04±1.91° loss of correction (P<0.001). The mean height of the intervertebral disc proximal to the fractured vertebra was 9.87±0.91 mm before surgery, 12.53±0.98 mm after operation (P<0.001), and the loss of correction at final follow-up was 2.35±1.15 mm with a significant difference compared to immediate postoperative values (P<0.001). Bone nonunion occurred in 7 patients, 2 patients had hardware failure, 9 patients had cement leakage, and 10 patients had disc vacuum phenomenon adjacent to the fractured vertebra.

CONCLUSIONS

The patients who underwent this procedure had a loss of correction of vertebral height and local kyphosis. Complications such as bone nonunion, instrument failure, cement leakage, and disc vacuum may occur. Rapid CSC resorption accounts for these radiographic outcomes and complications.

LEVEL OF EVIDENCE

Level IV, retrospective study.

Treatment of thoracolumbar fracture

The most common fractures of the spine are associated with the thoracolumbar junction. The goals of treatment of thoracolumbar fracture are leading to early mobilization and rehabilitation by restoring mechanical stability of fracture and inducing neurologic recovery, thereby enabling patients to return to the workplace. However, it is still debatable about the treatment methods. Neurologic injury should be identified by thorough physical examination for motor and sensory nerve system in order to determine the appropriate treatment. The mechanical stability of fracture also should be evaluated by plain radiographs and computed tomography. In some cases, magnetic resonance imaging is required to evaluate soft tissue injury involving neurologic structure or posterior ligament complex. Based on these physical examinations and imaging studies, fracture stability is evaluated and it is determined whether to use the conservative or operative treatment. The development of instruments have led to more interests on the operative treatment which saves mobile segments without fusion and on instrumentation through minimal invasive approach in recent years. It is still controversial for the use of these treatments because there have not been verified evidences yet. However, the morbidity of patients can be decreased and good clinical and radiologic outcomes can be achieved if the recent operative treatments are used carefully considering the fracture pattern and the injury severity.

Biomechanical effects of vertebroplasty on thoracolumbar burst fracture with transpedicular fixation: a finite element model analysis

OBJECTIVE

To investigate the biomechanical effects of augmentation of the fractured vertebrae after posterior instrumentation.

METHODS

By simulating internal fixation plus augmentation with cement, eight tridimensional, anatomically detailed finite element models of the T11-L1 functional spinal junction were developed. Two kinds of models for mimicking different severity of the fracture were established according to the Denis' classification. Augmentation with cement was conducted after reduction with posterior fixation using a universal spine system. These models assumed a three-column loading configuration as follows: compression, anteflexion, extension, lateroflexion and axial rotation. Stress of the implants and spine was evaluated.

RESULTS

Data showed that for severely fractured models, augmentation apparently decreased the von Mises stresses by 50% for the rods and 40% for the screws, about 40% for the inferior endplate of T11, and 50% for the superior endplate of L1 in vertical compression and other load situations.

CONCLUSION

We should only apply vertebroplasty to prevent correction loss and implants failure based on the fact that it could significantly decrease stress of the instrumentations and spine when the vertebrae are severely fractured.

LEVEL OF EVIDENCE

Level IV, biomechanical study.

Posterior short-segment instrumentation and limited segmental decompression supplemented with vertebroplasty with calcium sulphate and intermediate screws for thoracolumbar burst fractures

PURPOSE

Thoracolumbar burst fractures treated with short-segment posterior instrumentation without anterior column support is associated with a high incidence of implant failure and correction loss. This study was designed to evaluate the clinical and radiographic results following posterior short-segment instrumentation and limited segmental decompression supplemented with vertebroplasty with calcium sulphate and intermediate screws for patients with severe thoracolumbar burst fractures.

METHODS

Twenty-eight patients with thoracolumbar burst fractures of LSC point 7 or more underwent this procedure. The average follow-up was 27.5 months. Demographic data, radiographic parameters, neurologic function, clinical outcomes and treatment-related complications were prospectively evaluated.

RESULTS

Loss of vertebral body height and segmental kyphosis was 55.3 % and 20.2° before surgery, which significantly improved to 12.2 % and 5.4° at the final follow-up, respectively. Loss of kyphosis correction was 2.2°. The preoperative canal encroachment was 49 % that significantly improved to 8.8 %. The preoperative pain and function level showed a mean VAS score of 9.2 and ODI of 89.9 % that improved to 1.4 and 12.9 % at the final follow-up, respectively. No implant failure was observed in this series, and cement leakage occurred in two cases without clinical implications.

CONCLUSIONS

Excellent reduction and maintenance of thoracolumbar burst fractures can be achieved with short-segment pedicle instrumentation supplemented with anterior column reconstruction and intermediate screws. The resultant circumferential stabilization combined with a limited segmental decompression resulted in improved neurologic function and satisfactory clinical outcomes, with a low incidence of implant failure and progressive deformity.

Combination of percutaneous osteosynthesis and vertebroplasty of thoracolumbar split fractures under CT and fluoroscopy guidance: a new technique

OBJECTIVES

The purpose of our study was to evaluate the technical feasibility of the combination involving percutaneous screw fixation and vertebroplasty in split fractures of thoracolumbar spine.

METHODS

Institutional review board approval and informed consent were obtained. Ten consecutive adult patients who had posttraumatic vertebral split fractures (Magerl A2) were prospectively treated by an interventional radiologist under computed tomography and fluoroscopy guidance. Using a bilateral route under local anesthesia, one 4.0-mm cannulated screw was placed on one side to fix the fracture, and on the other side, vertebroplasty was performed. Follow-up ranging from 12 to 24 months was assessed using visual analog scale (VAS) and Oswestry disability index (ODI) RESULTS: Combined procedures were performed on thoracic and lumbar vertebrae, creating both osteosynthesis and cement bridge between the displaced fragment and the rest of the vertebral body. Mean VAS measurements ± standard deviation (SD) decreased from 7.5 ± 1.5 preoperatively to 3.2 ± 1.9 at 1 day, 2.1 ± 1.2 at 1 month, and 1.9 ± 1.4 at the last examination (P < 0.001). Mean ODI scores ± SD decreased from 65.3 ± 16.2, preoperatively, to 16.1 ± 5.0 at the final examination (P < 0.001).

CONCLUSIONS

This study suggests that type A2 vertebral fractures could be successfully stabilized by the combination of percutaneous osteosynthesis and vertebroplasty.

Posterior fixation of thoracolumbar burst fractures: is it possible to protect one segment in the lumbar region?

Background

The treatment for thoracolumbar burst fractures is controversial. The aim of this retrospective study was to compare intermediate-segment (IS) and long-segment (LS) instrumentation in the treatment for these fractures.

Methods

IS instrumentation was considered as pedicle fixation two levels above and one level below the fractured vertebra (infra-laminar hooks attached to lower vertebra with pedicle screws). LS instrumentation was done two levels above and two levels below the fractured vertebra. Among a total of 25 consecutive patients, Group 1 included ten patients treated by IS pedicle fixation, whereas Group 2 included fifteen patients treated by LS instrumentation.

Results

The measurements of local kyphosis (p = 0.955), sagittal index (p = 0.128), anterior vertebral height compression (p = 0.230) and canal diameter expansion (p = 0.839) demonstrated similar improvement at the final follow-up between the two groups. However, there was a significant difference (p < 0.05) between Group 1 and Group 2 regarding clinical outcome [Hannover scoring system, Oswestry disability questionnaire and the range of motion of the lumbar region compared to neutral (0°)].

Conclusions

The radiographic parameters were the same between the two groups. However, the clinical parameters demonstrated that IS instrumentation is a more effective management of thoracolumbar burst fractures.

Application of real-time B-mode ultrasound in posterior decompression and reduction for thoracolumbar burst fracture

This study aimed to investigate the role of real-time B-mode ultrasound in posterior decompression and reduction and to observe the signal changes in spinal cord blood flow in a thoracolumbar burst fracture (TBF). Between February 2004 and December 2008, 138 patients with TBF were divided into group A (108 cases) and group B (30 cases). In group A, under the assistance of real-time B-mode ultrasound, posterior decompression and fracture piece reduction were performed, and we observed the signal changes in spinal cord blood flow. In group B, posterior fenestration was combined with pushing the fracture piece into the fractured vertebral body using an L-shaped operative tool. Presurgical and postsurgical recovery of neurological function was evaluated according to American Spinal Injury Association (ASIA) standards, and the range of spinal decompression was determined by measuring the proportion of encroached fracture piece in the spinal canal (spinal stenosis rate) on the computed tomography (CT) image. In group A, 12 patients had a grade A spinal injury according to the Frankel grading system, and there were six cases without neurological recovery. In the other patients, neurological function increased by 1–3 grades. There were no aggravated spinal cord injuries or other serious complications. In group B, three patients were categorized as grade A and there were two cases without neurological recovery. In the other patients, neurological function increased by 1–3 grades. In groups A and B, the postsurgical spinal stenosis rate was significantly lower than the presurgical stenosis rate (P<0.05). The postsurgical spinal stenosis rate in group B was significantly higher compared with group A (P<0.05). There was no significant difference in neurological function recovery between the groups (P>0.05). Real-time B-mode ultrasound is an effective method for posterior decompression and reduction and to observe signal changes in spinal cord blood flow in TBF.

Is it useful to apply transpedicular intracorporeal bone grafting to unstable thoracolumbar fractures? A systematic review

BACKGROUND

The debate over the use of intracorporeal bone graft in treating unstable thoracolumbar fractures continues. We compiled evidence for the effect of transpedicular intracorporeal bone grafting (TPG) on outcome in patients with traumatic thoracolumbar fractures.

METHOD

A systematic review was conducted to compare the outcomes of short segment fixation and posterolateral fusion (PLF) with or without TPG. We reviewed articles in PubMed, Ovid, and the Cochrane Database published between January 1995 and August 2011. The correction loss and hardware failure between TPG and TPG+PLF were compared. We assessed the methodological quality of the studies according to the inclusion criteria.

RESULT

We divided 19 papers, involving 22 series, into two groups: posterolateral fusion, and posterolateral fusion combined with intracorporeal bone graft. Meta-analysis regression revealed statistically significant differences in correction loss and hardware failure between the two groups. There were no statistically significant differences in average age, follow-up period, fracture levels, or application of orthosis rate between the two groups.

CONCLUSION

PLF+TPG reduces hardware failure and correction loss compared with PLF alone. It also minimizes the likelihood of severe correction loss. For serious spinal injury cases, PLF+TPG was recommended to improve the prognosis. Further studies would be useful in determining the benefits of applying this method to the treatment of unstable thoracolumbar fractures.

Improved workability of injectable calcium sulfate bone cement by regulation of self-setting properties

Calcium sulfate hemihydrate (CSH) powder as an injectable bone cement was prepared by hydrothermal synthesis of calcium sulfate dihydrate (CSD). The prepared materials showed X-ray diffraction peaks corresponding to the CSH structure without any secondary phases, implying complete conversion from CSD phase to CSH phase. Thermogravimetric (TG) analyses showed the crystal water content of CSH was about 6.0% (wt.), which is near to the theoretic crystal water value of CSH. From scanning electron microscopy (SEM) micrographs, sheet crystal structure of CSD was observed to transform into rod-like crystal structure of CSH. Most interesting and important of all, CSD as setting accelerator was also introduced into CSH powder to regulate self-setting properties of injectable CSH paste, and thus the self-setting time of CSH paste can be regulated from near 30 min to less than 5 min by adding various amounts of setting accelerator. Because CSD is not only the reactant of preparing CSH but also the final solidified product of CSH, the setting accelerator has no significant effect on the other properties of materials, such as mechanical properties. In vitro biocompatibility and in vivo histology studies have demonstrated that the materials have good biocompatibility and good efficacy in bone regeneration. All these will further improve the workability of CSH in clinic applications.

The role of fusion in the management of burst fractures of the thoracolumbar spine treated by short segment pedicle screw fixation: a prospective randomised trial

The purpose of this study was to determine whether patients with a burst fracture of the thoracolumbar spine treated by short segment pedicle screw fixation fared better clinically and radiologically if the affected segment was fused at the same time. A total of 50 patients were enrolled in a prospective study and assigned to one of two groups. After the exclusion of three patients, there were 23 patients in the fusion group and 24 in the non-fusion group. Follow-up was at a mean of 23.9 months (18 to 30). Functional outcome was evaluated using the Greenough Low Back Outcome Score. Neurological function was graded using the American Spinal Injury Association Impairment Scale. Radiological outcome was assessed on the basis of the angle of kyphosis. Peri-operative blood transfusion requirements and duration of surgery were significantly higher in the fusion group (p = 0.029 and p < 0.001, respectively). There were no clinical or radiological differences in outcome between the groups (all outcomes p > 0.05). The results of this study suggest that adjunctive fusion is unnecessary when managing patients with a burst fracture of the thoracolumbar spine with short segment pedicle screw fixation.

Osteogenesis of mineralized collagen bone graft modified by PLA and calcium sulfate hemihydrate: in vivo study

In this study, the biocompatibility and bone regeneration performance of nano-hydroxyapatite/collagen/poly(L-lactide) (nHAC/PLA) and nano-hydroxyapatite/collagen/calcium sulfate hemihydrate (nHAC/CSH) as bone-filling materials were evaluated and compared in a critical box-shaped defect model in the mandible of the rabbits. In vivo results indicated that there was significant difference in early bone remodeling between two types of bone substitutes. nHAC/PLA has shown excellent biocompatibility, but no adequate handling properties. The addition of CSH to nHAC provided better manipulability compared to nHAC/PLA. Furthermore, nHAC/CSH possesses superior properties in restoring critical-sized bone defects of maxillofacial region at the early stage of remodeling over nHAC/PLA. Our results suggested that nHAC/CSH could be an alternative to the conventionally used bone tissue engineering materials.

Mid-term results of PLIF/TLIF in trauma

Treatment of thoracolumbar fractures is still controversial. Several treatment options are reported to yield satisfactory results. There is no evidence indicating superiority of any treatment option. We have already presented radiological results of the use of PLIF/TLIF in trauma, which showed satisfactory results concerning intervertebral fusion and acceptable loss of correction. We examined 50 patients regarding loss of correction after implant removal and clinical outcome using a validated visual analogue score. The average time of follow-up (FU) was 35 months. We observed a total loss of correction of 4°. The pre-injury mean VAS score was 92. At FU, there was an average reduction of 17.2 points. Owing to the presented results, we suggest this method as an alternative to combined procedures.