[Unilateral versus bilateral pedicle fixation at the level of fracture in the treatment of thoracolumbar fractures with mild to moderate instability].

OBJECTIVE: To evaluate the efficacies of unilateral versus bilateral pedicle screw fixation through the pedicle of fractured vertebra plus short-segment pedicle instrumentation (SSPI) in the treatment of thoracolumbar fractures. METHODS: Between June 2008 and September 2010, a total of 46 patients with fractures of thoracolumbar junction, whose scores of load sharing classification (LSC) ranging from 5 to 7, underwent the combined treatment of SSPI and fracture level pedicle screw at our department. They were divided into 2 groups. Group I included 25 patients undergoing SSPI plus unilateral pedicle screw fixation through the pedicle of fractured vertebra (5 screws) while Group II included 21 patients had SSPI plus bilateral pedicle screw fixation through the pedicle of fractured vertebra (6 screws). The data of anterior body height compression (AVHC), sagittal Cobb's angle, internal fixation failure, restoration of nervous function, visual analogue score (VAS) and Oswestry disability index (ODI) were analyzed. RESULTS: The groups were similar with regards to age, gender, LSC, AVHC and sagittal Cobb's angle preoperatively. Blood loss volume and operative duration were less in the Group I (109.2 ± 30.68 vs 110.0 ± 32.06 min, t = -0.086, P > 0.05 and 376.0 ± 303.1 vs 409.5 ± 361.1 ml, t = -0.342, P > 0.05). They were followed up for a minimum period of 12 months. In follow-up period was 17.48 ± 4.14 months in Group I versus 18.33 ± 4.31 months in Group II (t = -0.683, P > 0.05). All patients with initial partial neurologic deficits improved at the final follow-up. Radiographic parameters and clinical outcomes were similar in both groups. CONCLUSIONS: Pedicle screw fixation through the pedicle of fractured vertebra plus SSPI is an excellent surgical therapeutic choice for patients with a LSC range of 5-7 thoraclumbar fractures. The efficacies of unilateral and bilateral pedicle screw fixation at fracture level are the same.

[Efficacy analysis of intermediate screws technique plus injectable calcium sulfate for thoracolumbar fracture in postmenopausal patients].

OBJECTIVE: To explore the clinical efficacies of intermediate screws plus injectable calcium sulfate MIIGX3 for thoracolumbar fracture in postmenopausal patients. METHODS: A total of 21 postmenopausal patients with vertebral compression fractures reconstructed with posterior internal fixation of intermediate screws technique and anterior vertebral augmentation of MIIGX3 technique in three dimension were retrospectively analyzed. The changes of fracture vertebral height and Cobb's angle were compared.Visual analogue scale (VAS) was performed to evaluate their symptoms. All patients were followed up. RESULTS: Intermediate screws surgical technique plus MIIGX3 was successfully performed. The average injection dose was 4.6 ml.Leakage occurred intraoperatively in two cases. The average follow-up period was 15 (6-36) months. The VAS system demonstrated that pain decreased significantly (preoperative:7.8, postoperative:2.2). The height and Cobb's angle of fractured vertebra improved greatly. The preoperative values were 45.0 ± 6.4% and 19.4 ± 4.5° and postoperative ones 15.4 ± 3.9% and 8.64 ± 3.18° respectively. There was no occurrence of severe complications related with treatment.Except for 2 patients with a loss of 15% of vertebral height, the average heights of fractured vertebra in other 19 patients recovered to 85% of normal ones. CONCLUSION: Thoracolumbar fracture in postmenopausal patients may be managed satisfactorily by intermediate screws and injectable calcium sulfate technique.Such a technique is both safe and effective. And its stable and durable reduction offers significant improvement.

[Unilateral pedicle screw fixation through the pedicle of fractured vertebra in combination with the short segment of pedicle screw in the treatment of thoracolumbar fracture of mild to moderate instability].

OBJECTIVE: To evaluate the efficacy of unilateral pedicle screw fixation through the pedicle of fractured vertebra in combination with the short segment of pedicle screw in the treatment of thoracolumbar fracture of mild to moderate instability. METHODS: Twenty-six patients with single segment thoracolumbar fracture received unilateral pedicle screw fixation through the pedicle of fractured vertebra in combination with the short segment of pedicle screw from January 2008 to December 2009. There were 16 patients were male and 10 were female with an average age of 47.3 years (range from 39 to 60 years). Fracture severity score was constructed by using the load-sharing classification (4 points for 2 cases, 5 points for 14 cases, 6 points for 10 cases). By Frankel assessment system, 2 cases were in grade C, 3 in grade D, 21 in grade E. The assessment included anterior vertebral body height, the sagittal Cobb angle, the restoration of nervous function, visual analogue score (VAS) and Oswestry disability index (ODI). RESULTS: The follow-up after the surgery was 13 - 26 months, with an average of 18.6 months. There were no fixation failure, defined as implant failure or ≥ 10° correction loss. The neurological status of 4 patients, who had an associated neurologic deficit preoperatively, was completely recovered. The Frankel grade of another case was re-rated D from the original C. The mean anterior vertebral body height increased from 57.0% ± 6.3% before the surgery to 93.1% ± 1.7% at the last follow-up(F = 455.276, P < 0.05). The sagittal Cobb angle decreased from 15.6° ± 4.7° before the surgery to 2.6° ± 5.2° at the last follow-up (F = 34.623, P < 0.05). VAS and ODI were 1.0 ± 0.7 and 17.0 ± 5.9 at the last follow-up. CONCLUSION: Unilateral pedicle screw fixation through the pedicle of fractured vertebra combined with the short segment of pedicle screw is effective for thoracolumbar fracture with mild to moderate instability.

[Digital simulation of unipedicular thoracolumbar vertebroplasty puncture].

OBJECTIVE: To measure such operative parameters of unipedicular kyphoplasty as optimal entry point, angle and depth so as to provide rationales for its clinical management and formulate a standardized protocol for unipedicular vertebroplasty. METHODS: Ten dry thoracolumbar specimens were prepared for measurement. The entry and target points were defined according to the Roy-Camille method. A 3mm Kirschner wire was used to puncture and view in the anteroposterior and lateral aspects of radiography until a satisfying position. The outside oblique and upward oblique angles were measured on the radiographic pictures. After extraction, the depth of Kirschner wire was measured. The positions of entry point were changed and the largest upward oblique angle and largest declination angle measured on the radiographic pictures. RESULTS: For safe puncturing, as the outside oblique and upward oblique angles enlarged from T(11) to L(3), the length enlarged from T(11) to T(12) and L(1) to L(3). The accepted error was that the largest upward oblique angle and largest declination angle enlarged from T(11) to L(3). The alteration range for outside oblique angle was extremely narrow. CONCLUSION: The experimental results provide the guiding data for the operative management of unipedicular thoracolumbar vertebroplasty. If the pedicle is too small or the angle too narrow, the operative sophistication of vertebroplasty will be highly demanding.

Treatment of isolated posterior coronal fracture of the lateral tibial plateau through posterolateral approach for direct exposure and buttress plate fixation.

PURPOSE: To present a case series of patients with isolated posterior coronal fractures of lateral tibial plateau treated by direct exposure and buttress plate fixation through posterolateral approach. METHODS: Between May 2007 and April of 2008, eight middle aged patients were identified that had isolated posterior coronal fractures of the lateral tibial plateau. All eight patients underwent direct fracture exposure, reduction under visualization, and buttress plate fixation through posterolateral approach. RESULTS: There were 1 case of split, two cases of pure depression and five cases of split-depression fractures. Four were associated fibular head split fractures without common peroneal nerve injuries. Five patients were injured from a simple fall on riding electrical bicycle while the knee was relaxed in 90 degrees position The articular displacement (8 cases) measured in CT scan was 10.5 mm in average (range 8-15 mm). The cortical split length (from the articular rim to the distal tip, 6 cases) was 2.8 cm in average (range 2.4-3.5 cm). The articular reduction was perfect in seven (absolutely no step-off) and imperfect in 1(<2 mm step-off) as measured by X-ray. With a mean follow-up of 10 months (6 cases > 12 months), the average range of motion arc was 119 degrees , four patients have flexion lag 10 degrees -20 degrees . The average SMFA dysfunction score was 15.8, and average HSS score was 98. All eight patients stated they were highly satisfied. CONCLUSIONS: Direct posterolateral approach by dividing lateral border of soleus muscle, provides excellent fracture reduction under visualization and internal buttress plate fixation for posterior coronal fracture of the lateral tibial plateau. Good functional results and recovery can be expected.

A finite element analysis of the pelvic reconstruction using fibular transplantation fixed with four different rod-screw systems after type I resection.

BACKGROUND: The pelvis often needs to be reconstructed after bone tumor resection. A major challenge here for the orthopedic surgeons is to choose a method that gives the best performance which depends upon its biomechanical properties. In this study, a 3-dimensional finite element analysis (FEA) was used to analyze the biomechanical properties of reconstructed pelvis using fibula transplant fixed by four commonly used rod-screw systems. METHODS: A total pelvic finite-element model including the lumbar-sacral spine and proximal femur was constructed based on the geometry of CT image from a healthy volunteer. Three-dimensional finite element models of different implants including fibula, rod and screw were simulated using ways of solid modeling. Then various reconstructed finite element models were assembled with different finite element implant model and type I resected pelvic finite element model. The load of 500 N was imposed vertically onto the superior surface of L3 vertebral body, and the pelvis was fixed in bilateral leg standing positions. FEA was performed to account for the stress distribution on the bones and implants. The pelvis displacement of the different rod-screw fixation methods and the maximum equivalent stress (max EQV) on all nodes and element were figured out to evaluate the advantages and disadvantages of different reconstructive methods. RESULTS: Stress concentration in the fibula transplant was extremely high in the reconstructed pelvis, but could be substantially decreased by internal fixation, which partially transferred the stress from the fibula to the rod-screw systems. High stress concentration was also found in the implants, especially in the connection sites between screw and rod. Among the four methods of fixation, a double rod system with L5-S1 pedicle and ilium screws (L5-S1 HR) produced the best performance: least stress concentrations and least total displacement. CONCLUSION: According to the stability and stress concentration, the method of L5-S1 HR fixation combined with fibula transplantation is better than other fixation methods in pelvic reconstruction after type I resection.

[Analysis of the pelvic stability after type I resection of iliac tumor].

OBJECTIVE: To analyze the pelvic stability after type I resection of iliac tumor. METHODS: Six adult cadaveric specimens were tested. The iliac subtotal resection models were established according to Ennecking's type I resection. Markers were affixed to the key region of the pelves. Axial loading from the proximal lumbar was applied by MTS load cell in the gradient of 0-500 N in the double feet standing state. Images in front view were obtained using CCD camera. Based on Image J software, displacements of the first sacral vertebrae (S1) of the resected pelves and the intact pelves were calculated using digital marker tracing method with center-of-mass algorithm. RESULTS: Serious instabilities were found in the resected pelves. S1 rotational movements around the normal side femoral head of the resected pelvis were found. The average vertical displacement of S1 of the resected pelvis was (7 +/- 3) mm under vertical load of 500 newtons, which were 8.3 times compared to the intact pelvis. The average angle of S1 rotation around the normal side femoral head of the resected pelvis was (4.0 +/- 1.8) degrees, which were 12.5 times compared to the intact pelvis. CONCLUSIONS: Biomechanical model of type I resection of iliac tumor are established. Essential pelvic reconstruction must be introduced because of the serious instability of the bone defection after tumor resection.

[Development and validating of a three-dimensional finite element model of total human pelvis].

OBJECTIVE: To develop a three-dimensional finite element model of normal total adult human pelvis and to establish a platform for biomechanical research of human pelvis. METHODS: 186 series of traverse CT images of the pelvis, from the third lumbar vertebra (L3) to the upper third of femur, obtained with spiral CT scanning on a healthy man, aged 42, without diseases of lumbar vertebrae and pelvis, were processed. A three-dimensional finite element model of pelvis was constructed directly by producing the units and nodes with the pixels of the original CT films, using ANSYS finite analytical system. RESULT: A three-dimensional finite element model of normal human pelvis was constructed including lumbar and proximal femur, which could be divided into 207,248 nodes and 721,820 units. CONCLUSION: The established three-dimensional finite element model of normal adult is valid and reasonable, and can be used for biomechanical analysis.

Analysis of risk factors for adjacent superior vertebral pedicle-induced facet joint violation during the minimally invasive surgery transforaminal lumbar interbody fusion: a retrospective study.

BACKGROUND: The purpose was to explore possible risk factors of facet joint violation induced by adjacent superior vertebral pedicle screw during the minimally invasive surgery transforaminal lumbar interbody fusion (MIS-TLIF). METHODS: A total of 69 patients with lumbar degenerative disease, who underwent MIS-TLIF were retrospectively reviewed. Postoperative computed tomography images were used to assess the facet joint violation. The correlation of facet joint violations with gender, age, body mass index (BMI), the adjacent superior vertebral level, fusion segment numbers, position of screw insertion, straight leg-raising test (SLRT) results, clinical diseases and renal dysfunction were analyzed by Chi-square tests and binary logistic regression analysis. RESULTS: The incidence of adjacent superior facet joint violations was 25.4 %. Chi-square test showed the patients with age <60 and high BMI (≥30 kg/m(2)) were more prone to have facet joint violations (P = 0.007; P = 0.006). The single segment fusion presented more facet joint violations than the double segments fusion (P = 0.048). The vertebral pedicle screw implant location at L5 showed more facet joint violations compared with that at L3 and L4 (P = 0.035). No correlation was found between gender, screw implant position, SLRT results, clinical diseases and renal dysfunction and facet joint violations. Logistic regression analysis revealed that age <60 years (OR: 2.902; 95 % CI 1.227-6.864; P = 0.015) and BMI ≥30 kg/m(2) (OR: 2.825; 95 % CI 1.191-6.700; P = 0.018 < 0.05) were significantly associated with facet joint violation. CONCLUSION: These results found a high incidence of adjacent superior vertebral facet joint violation in the MIS-TLIF. Age <60 and BMI ≥30 kg/m(2) might be risk factors of facet joint violation. Evidence level: Level 4.

Tumor blood vessels formation in osteosarcoma: vasculogenesis mimicry.

BACKGROUND: Osteosarcoma is characterized by high neovascularization and a high propensity for metastasis through bloodstream. This study was to examine whether there is evidence for vasculogenic mimicry in osteosarcoma and to illustrate mechanism of tumor blood vessels formation in osteosarcoma. METHODS: Osteosarcoma cell lines (U-2OS) were tested for their ability to form tubular networks in three-dimensional culture containing type I collagen. The structures of the tubular networks were observed with phase contrast microscope and transmission electron microscope (TEM). Morphometric studies using hematoxylin and eosin (HE) stain and CD31 immunohistochemical stain to show tumor-lined channels in human osteosarcoma were also performed. RESULTS: Observation with light microscope and TEM showed that highly aggressive osteosarcoma cell lines (U-2OS) formed networks containing channels when grown in three-dimensional culture containing type I collagen, in the absence of endothelial cells or fibroblasts. Morphometric observation using HE stain and CD31 immunohistochemical stain showed that tumor cell-lined channels were also detected in vivo in osteosarcoma; by comparison, all vascular areas in the pedicle of osteochondroma or outside osteochondroma were endothelial-lined. CONCLUSION: These observations strongly suggest that aggressive osteosarcoma cells may generate vascular channels that facilitate tumor perfusion independent of tumor angiogenesis and have the ability of vasculogenic mimicry.

The strain at bone-implant interface determines the effect of spinopelvic reconstruction following total sacrectomy: a strain gauge analysis in various spinopelvic constructs.

PURPOSE: There is still some controversy regarding the optimal biomechanical concept for spinopelvic stabilization following total sacrectomy for malignancy. Strains at specific anatomical sites at pelvis/sacrum and implants interfaces have been poorly investigated. Herein, we compared and analyzed the strains applied at key points at the bone-implant interface in four different spinopelvic constructs following total sacrectomy; consequently, we defined a balanced architecture for spinopelvic fusion in that situation. METHODS: Six human cadaveric specimens, from second lumbar vertebra to proximal femur, were used to compare the partial strains at specific sites in a total sacrectomy model. Test constructs included: (1) intact pelvis (control), (2) sacral-rod reconstruction (SRR), (3) bilateral fibular flap reconstruction (BFFR), (4) four-rods reconstruction (FRR), and (5) improved compound reconstruction (ICR). Strains were measured by bonded strain gauges onto the surface of three specific sites (pubic rami, arcuate lines, and posterior spinal rods) under a 500 N axial load. RESULTS: ICR caused lower strains at specific sites and, moreover, on stress distribution and symmetry, compared to the other three constructs. Strains at pubic rami and arcuate lines following BFFR were lower than those following SRR, but higher at the posterior spinal rod construct. The different modes of strain distribution reflected different patient's parameter-related conditions. FRR model showed the highest strains at all sites because of the lack of an anterior bracing frame. CONCLUSIONS: The findings of this investigation suggest that both anterior bracing frame and the four-rods load dispersion provide significant load sharing. Additionally, these two constructs decrease the peak strains at bone-implant interface, thus determining the theoretical surgical technique to achieve optimal stress dispersion and balance for spinopelvic reconstruction in early postoperative period following total sacrectomy.

Formative mechanism of intracanal fracture fragments in thoracolumbar burst fractures: a finite element study.

BACKGROUND: Thoracolumbar burst fracture is a common clinical injury, and the fracture mechanism is still controversial. The aim of this research was to study the formation of intracanal fracture fragments in thoracolumbar burst fractures and to provide information for the prevention of thoracolumbar bursts fractures and reduction of damage to the nervous system. METHODS: A nonlinear three-dimensional finite element model of T11-3 segments was established, and the injury processes of thoracolumbar bursts were simulated. The intact finite element model and the finite element model after the superior articular were impacted by 100 J of energy in different directions. The distribution and variation of stress in the superior posterior region of the L1 vertebral body were analyzed. Abaqus 6.9 explicit dynamic solver was used as finite element software in calculations. RESULTS: A three-dimensional nonlinear finite element model of the thoracolumbar spine was created. In the intact model, stress was concentrated in the superior posterior region of the L1 vertebral body. The stress peak was a maximum for the extension impact load and a minimum for the flexion impact load. The stress peak and contact force in the facet joint had close correlation with time. The stress peak disappeared after excision of the superior articular process. CONCLUSIONS: The three-dimensional nonlinear finite element model was suitable for dynamic analysis. The contact force in the facet joint, which can be transferred to the superior posterior vertebral body, may explain the spinal canal fragment in thoracolumbar burst fractures.