Grease-gun injury of the orbit: two cases report and literature review.

BACKGROUND: The grease-guns injury is an uncommon injury to the orbit. We present the twelfth and thirteenth cases of grease-gun injury to the orbit to be reported in the English language literature since 1964. Here we discus and review the presentation, investigation, and treatment of this unusual trauma. CASE PRESENTATION: Case 1 was a 29-year-old man who presented 1 day after a grease-gun injury of the left orbit with severe pain, marked periorbital swelling, and proptosis. Computed tomography (CT) revealed penetration of grease into his left orbit. Following surgical removal, proptosis decreased. The limitation of extraocular movement and loss of visual acuity to finger count was discovered after the initial surgery. Motility gradually returned. Visual acuity recovered after phacoemulsification, capsular tension ring and intraocular lens implantation for traumatic cataract and subluxation. Case 2 was a 6-year-old boy who was referred 2 months after a grease-gun injury for worsening swelling with sinus, necrosis and slight ptosis of the upper left eyelids. This is a case of orbital chronic inflammation from grease-gun injuries masquerading as orbital cellulitis. The imaging findings of CT and magnetic resonance imaging (MRI) are not typical. Surgical exploration and debridement was inevitable and actually relieved the symptoms. CONCLUSIONS: Grease-gun injuries can damage the orbit in different degrees. Careful history inquiry and taking is important to establish the diagnosis. Imaging examinations using CT or MRI are helpful to determine depth of trauma and foreign bodies in the orbit at diagnosis. We suggest that surgical exploration and debridement is a key step in the management.

Effect of endplate reduction on endplate healing morphology and intervertebral disc degeneration in patients with thoracolumbar vertebral fracture.

OBJECTIVE: To determine the effect of endplate reduction on the final healing morphology and degenerative changes in intervertebral discs. METHODS: Forty-eight patients with single-level thoracolumbar fractures with endplate injury were included. All patients underwent posterior reduction and pedicle screw fixation, and postoperative imaging was used to determine whether endplate reduction was successful. The healing morphology of the endplate was divided into three types: increased endplate curvature, irregular healing and traumatic Schmorl node. MRI was performed at baseline and at the last follow-up evaluation to observe changes in disc degeneration (disc height and nucleus pulposus signal) and Modic changes. RESULTS: The reduction rate in the central area was significantly lower than that in the peripheral area (P = 0.017). In patients with successful reduction, 90.9% (20/22) of the endplates healed with increased curvature. In patients with an unsuccessful endplate reduction, 63.4% (26/41) of the endplates healed irregularly, and 34.1% (14/41) of the endplates formed traumatic Schmorl nodes. Endplate reduction was closely related to the final healing morphology of the endplate (P < 0.001), which had a significant protective effect on the degeneration of the intervertebral disc. At the last follow-up evaluation, there was no statistically significant correlation between different endplate healing morphologies and new Modic changes. CONCLUSIONS: The reduction rate in the central area is significantly lower than that in the peripheral area. Although all of the intervertebral discs corresponding to fractured endplates had degenerated to different degrees, successful endplate fracture reduction can obviously delay the degeneration of intervertebral discs.

Associations of muscle size and fatty infiltration with bone mineral density of the proximal femur bone.

Purpose: To investigate the relationship of muscle atrophy and fat infiltration around the hip joint with areal bone mineral density (aBMD) in each subregion of the proximal femur. Materials and methods: In total, 144 participants (66 women and 78 men) were examined by quantitative computed tomography (QCT), and areal bone mineral density (aBMD) of the femoral neck (FN), trochanter (TR), and intertrochanter (IT) of the proximal femur were obtained. The cross-sectional area (CSA) and proton density fat fraction (PDFF) of the gluteus maximus (G.MaxM), gluteus medius (G.MedM), gluteus minimus (G.MinM), and iliopsoas (IliopM) were obtained via magnetic resonance imaging (MRI) using the mDIXON-Quant sequence. A multivariate generalized linear model was used to evaluate the correlation of the CSA and PDFF of muscles with aBMD in all subregions of the proximal femur. Results: The FN integral (Int) aBMD was significantly associated with the G.MaxM CSA (men: P = 0.002; women: P = 0.008) and PDFF (men: P < 0.001; women: P = 0.047). Some muscle indexes were related to the FN aBMD in males or females, including the CSA of G.MedM, G.MinM, and IliopM as well as the PDFF of IliopM and G.MinM. Associations of hip muscle parameters with the TR Int aBMD in both males and females were observed, including G.MaxM CSA (men: P < 0.001; women: P = 0.028) and G.MaxM PDFF (men: P = 0.031; women: P = 0.038). Other muscle indexes, including G.MedM and IliopM, were related to the TR aBMD, mainly affecting the aBMD of TR cortical (Cort) and TR Int. The IT Int aBMD and IT Cort aBMD showed significant correlation with the muscle indexes of G. MaxM, IliopM, and G.MedM, including the PDFF and CSA in males and females. Further, more indicators of the G.MedM and IliopM correlated with the TR and IT aBMD compared to the FN aBMD. Conclusions: The CSA of gluteus muscles and iliopsoas had a positive association with the aBMD in the proximal femur, and the PDFF of gluteus muscles and iliopsoas had a negative correlation with the aBMD in the proximal femur. In addition, there was an interaction of the proximal femur aBMD with the muscle size and fatty infiltration of hip muscles.

Accurate Placement of Cannulated Screws in Femoral Neck Fractures: Screw and Guide Wire Combined Technique.

Cannulated screw fixation is widely used in the treatment of femoral neck fractures. During surgery, we often face the situation that a guide wire needs to be adjusted because of poor positioning in the femoral neck. It is difficult to adjust the direction of the guide wire in the neck of the femur due to its elasticity. This study developed a practical technique to adjust the guide wire to the correct position. When the direction of insertion of the guide wire has deviated, first, measure the length of the guide wire. Second, select the appropriate cannulated screw based on the measurement, and screw the cannulated screw in along the direction of the guide wire to Ward's triangle. Then return the guide wire to the front of the cannulated screw. At this time, the cannulated screw can be used as a built-in guide, and a screwdriver can be used to fine-tune the position of the screw to the optimal direction under the X-ray guidance. Finally, the cannulated screw is screwed in in this direction until it passes through the Ward triangle area, and the guide wire is inserted. This technique can help doctors insert a guide wire more quickly and accurately, reducing intraoperative injury and the operation time.

Quantitative evaluation of upper urinary tract pump function in pigs with acute unilateral lower ureteral obstruction by 640-slice dynamic volume CT.

BACKGROUND: It is a challenging problem to differentiate obstructive hydronephrosis from noninvasive evaluation of renal pelvis and ureteral motility in patients. The purpose of this study was to explore the value of 640-slice dynamic volume CT (DVCT) in the quantitative measurement of upper urinary tract (UUT) pump function after acute unilateral lower ureteral obstruction in pigs. METHODS: In this study, a perfusion pig model was constructed by constant pressure perfusion testing of the renal pelvis and left nephrostomy. The perfusion and pressure measuring devices were connected to create a state of no obstruction and acute obstruction of the lower part of the left ureter. After successful modelling, continuous dynamic volume scanning of the bilateral renal excretion phase was performed with 640-slice DVCT, and pump functions of the renal pelvis and part of the upper ureter were calculated and analysed. No obstruction or acute obstruction of the lower part of the left ureter was observed. Pump functions of the renal pelvis and part of the upper ureter were determined. RESULTS: The results showed that after LUUT fistulostomy, the time difference between the average UUT volume and positive volume value increased gradually, and the calculated flow velocity decreased, which was significantly different from that of the RUUT. The volume difference of the LUUT increased significantly in mild obstruction. In the bilateral control, the volume change rate of the LUUT increased with mild obstruction and decreased with severe obstruction, and there was a significant difference between the left and right sides. CONCLUSION: The continuous dynamic volume scan and measurement of 640-slice DVCT can obtain five pump function datasets of UUT in pigs with acute lower ureteral obstruction.

Effects of endplate healing morphology on intervertebral disc degeneration after pedicle screw fixation for thoracolumbar fractures.

ABSTRACT: The cartilage endplate plays an important role in the stress distribution and nutrition metabolism of the intervertebral disc. The healing morphology of the endplate after spinal fracture and its effect on the intervertebral disc degeneration are still unclear.This was a retrospective study. Patients with traumatic single-level thoracolumbar fractures treated in our orthopedic trauma service center from June 2011 to May 2019 were included and the relevant data were collected from the medical records. Based on combined computed tomography and MRI images, the endplate injury status was determined (no endplate injury, unilateral and bilateral endplate injury). According to the location of the injury, endplate injury was further divided into endplate central injury and endplate peripheral injury. The degree of posttraumatic disc lesions and disc degeneration during follow-up were classified based on the Sander classification and the Pfirrmann classification, respectively. According to the T1 image of MRI at the final follow-up, the healing morphology of endplates was determined and classified. Univariate analyses and correlation analyses were performed to evaluate the within- and between-group differences.There were in total 51 patients included in this study. Cartilage endplate fracture was significantly closely related to the degree of degeneration of the intervertebral disc (P = .003). Injuries in different parts of the endplate have no significant effect on the intervertebral disc degeneration (P = .204). The healing morphology after endplate fracture significantly affected the degree of intervertebral disc degeneration (P = .001). The comparisons of groups showed that the effects of irregular healing and traumatic Schmorl nodes on disc degeneration were not statistically significant, but were significantly significant with increased curvature.These results suggest that the irregular healing and the traumatic Schmorl nodes are closely related to intervertebral disc degeneration. The presence and severity of the endplate injury can provide valuable information for individualized clinical decision-making processes.

Laser lithotripsy for proximal ureteral calculi in adults: can 3D CT texture analysis help predict treatment success?

OBJECTIVE: To explore whether multiple 3D computed tomography texture analysis (3D-CTTA) parameters can predict the therapeutic effects of holmium: YAG laser lithotripsy (LL) on ureteral calculi. METHODS: The files from 94 patients (102 stones) with proximal ureteral calculi treated only by LL at a single institution were retrospectively retrieved from January 2016 to March 2019. According to intra-operative observations and postoperative reexamination, samples were divided into a completely crushed and a non-crushed group. Preoperative non-contrast-enhanced computed tomography (NCCT) images obtained by multiple CT scanners were imported to MaZda software for 3D texture analysis (TA). The CT-derived value of each target stone was measured, and 15 TA parameters were extracted by delineating volumes of interest (VOIs). Receiver operating characteristic (ROC) curves were drawn to determine the optimal critical value of each parameter based on the Youden index, and univariable and multivariable logistic regression analyses determined the significant factors for LL success. RESULTS: In univariable analysis, significant differences (p < 0.05) were observed among 7 parameters. In multivariable analysis, Perc.01 3D > 2062 (p = 0.03) and Z-fraction of image in runs (Z-Fraction) > 0.45570 (p = 0.009) were significant independent predictors, with odds ratios (ORs) of 24.204 and 60.329, respectively. In subgroup analysis based on the cutoff value of the CT-derived value (HU = 960), Perc.01 3D (OR = 44.154, 95% CI (2.379, 819.618), p = 0.011) and Z-Fraction (OR = 14.519, 95% CI (2.088, 100.953), p = 0.007) remained statistically significant. CONCLUSIONS: The combination of 3D-CTTA parameters and the CT-derived value can be used as a quantitative reference to predict whether a target stone could be completely crushed by LL. KEY POINTS: • Computed tomography texture analysis (CTTA) may be helpful in selecting suitable laser lithotripsy (LL) patients. • 3D-CTTA better predicts stone fragility than commonly used methods (such as the CT-derived value). • The combination of CTTA and the CT-derived value can be used as a preoperative quantitative reference.

Upregulation of Sirt1 by tyrosol suppresses apoptosis and inflammation and modulates extracellular matrix remodeling in interleukin-1ß-stimulated human nucleus pulposus cells through activation of PI3K/Akt pathway.

Intervertebral disc degeneration (IDD) is the major pathogenesis of lower back pain. Tyrosol is a polyphenolic compound that exhibits anti-oxidant, anti-apoptotic, and anti-inflammatory effects. Herein, we explored the effects and mechanisms of tyrosol on IDD progression in interleukin (IL)-1ß-stimulated human nucleus pulposus cells (HNPCs). Cell viability and apoptosis were detected by CCK-8 and flow cytometry analysis, respectively. The production of tumor necrosis factor-α (TNF-α), IL-6, nitric oxide (NO), and prostaglandin E2 (PGE2) was examined to evaluate inflammation. The mRNA expression of matrix metalloproteinases (MMPs) (MMP-3/9/13), collagen type II, SRY-related high mobility group box 9 (SOX-9), and aggrecan was measured by qRT-PCR. Protein levels of silent information regulator 2 homolog 1 (Sirt1), phosphorylated protein kinase B (p-Akt), Akt, collagen type II, SOX-9, and aggrecan were determined by western blot. Results showed that tyrosol attenuated IL-1ß-induced viability reduction, apoptosis, and caspase-3/7 activity in HNPCs. The increase in the production of TNF-α, IL-6, NO, and PGE2 in IL-1ß-treated HNPCs was abolished by tyrosol treatment. Tyrosol treatment reversed IL-1ß-induced upregulation of MMP-3, MMP-9, and MMP-13, and downregulation of collagen II, SOX-9, and aggrecan in HNPCs. Additionally, tyrosol treatment activated the phosphatidylinositol 3-kinase (PI3K)/Akt pathway in IL-1ß-stimulated HNPCs. Sirt1 was upregulated by tyrosol, and Sirt1 silencing inhibited Akt phosphorylation in HNPCs. Sirt1 knockdown attenuated the effects of tyrosol on IL-1ß-induced apoptosis, inflammation, and ECM remodeling in HNPCs. In summary, upregulation of Sirt1 by tyrosol suppressed apoptosis and inflammation and regulated ECM remodeling in IL-1ß-stimulated HNPCs through activation of PI3K/Akt pathway.

Hallermann-Streiff syndrome with uncommon ocular features, ultrasound biomicroscopy and optical coherence tomography findings: A case report.

RATIONALE: Hallermann-Streiff syndrome (HSS) is a rare congenital disorder characterized by craniofacial malformations, sparse hair, degenerative skin changes, eye abnormalities, dental defects, and proportionate short stature. PATIENT CONCERNS: A 24-year-old Chinese male patient presented to the ophthalmologist because of his sore eye and blurred vision. DIAGNOSES: The final diagnosis of presented case is HSS having the main features of the syndrome, however, associated with uncommon ocular features, ultrasound biomicroscopy (UBM) and optical coherence tomography (OCT)changes, including aphakia, glaucoma, long eye axes, cilliary abnormalities, and chorioretinal atrophy. INTERVENTIONS: Antiglaucomatous medical therapy failed to reduce the pressure in the right eye and a cyclocryotherapy was carried out. The antiglaucoma eye drops was continued in the left eye. OUTCOMES: The intraocular pressure has been reduced to the normal range, but the vision has not improved. LESSONS: In the diagnosis of HSS, we should not ignore the extraordinary information especially uncommon ophthalmic features, UBM and OCT changes. We highlight the necessity of a multidisciplinary approach for accurate diagnosis and appropriate management.

A finite element study on posterior short segment fixation combined with unilateral fixation using pedicle screws for stable thoracolumbar fracture.

The objective of this study was to use finite element models to investigate the biomechanics of stable thoracolumbar burst fracture repair using unilateral short-segment fixation and 4 alternate pedicle screw systems.Four posterior pedicle screw systems were compared for unilateral short-segment fixation using finite element models: intermediate bilateral short pedicle screw fixation, intermediate bilateral long pedicle screw fixation, intermediate unilateral short pedicle screw fixation, and intermediate unilateral long pedicle screw fixation. We compared range of motion (ROM), von Mises stresses on the implants, and stress on the intervertebral discs superior and inferior to the injured vertebra during simulated spinal movements.There were no significant differences in ROM, von Mises stress, or intervertebral disc stress among the 4 intermediate pedicle screw fixation techniques for all spinal movements evaluated. In addition, there were no consolidated trends depicting beneficial differences between the short and long screw models, or between the unilateral and bilateral screw models.ROM, von Mises stress, and intervertebral disc stress are the same across the 4, posterior short-segment fixation techniques evaluated using finite element models. The simplest technique-posterior short segment fixation combined with intermediate unilateral short pedicle screw fixation-is a feasible treatment strategy for stable thoracolumbar fracture.

640-slice DVCT multi-dimensionally and dynamically presents changes in bladder volume and urine flow rate.

The present study aimed to explore the application of 640-slice dynamic volume computed tomography (DVCT) to excretory cystography and urethrography. A total of 70 healthy subjects were included in the study. Excretory cystography and urethrography using 640-slice DVCT was conducted to continuously record the motions of the bladder and the proximal female and male urethra. The patients' voiding process was divided into early, early to middle, middle, middle to late, and late voiding phases. The subjects were analyzed using DVCT and conventional CT. The cross-sectional areas of various sections of the male and female urethra were evaluated, and the average urine flow rate was calculated. The 640-slice DVCT technique was used to dynamically observe the urine flow rate and changes in bladder volume at all voiding phases. The urine volume detected by 640-slice DVCT exhibited no significant difference compared with the actual volume, and no significant difference compared with that determined using conventional CT. Furthermore, no significant difference in the volume of the bladder at each phase of the voiding process was detected between 640-slice DVCT and conventional CT. The results indicate that 640-slice DVCT can accurately evaluate the status of the male posterior urethra and female urethra. In conclusion, 640-slice DVCT is able to multi-dimensionally and dynamically present changes in bladder volume and urine flow rate, and could obtain similar results to conventional CT in detecting urine volume, as well as the status of the male posterior urethra and female urethra.

OM-LV20, a novel peptide from odorous frog skin, accelerates wound healing in vitro and in vivo.

The healing of chronic wounds remains a considerable challenge in clinical trials and imposes severe financial and physiological burdens on patients. Many works are being tried to find ideal clinical promoting wound healing biomaterials. Small bioactive peptides with low cost and easy production, store and transfer become excellent candidates. Here, we identified a novel peptide (named OM-LV20) from skin secretions of odorous frog Odorrana margaretae. The peptide had an amino acid sequence of "LVGKLLKGAVGDVCGLLPIC," contained an intramolecular disulfide bridge at the C-terminus, and was produced by post-translational processing of a 71-residue prepropeptide. Our results showed that OM-LV20 had no direct microbe-killing effects, hemolytic activity, or acute toxicity, but did exhibit weak antioxidant activity. OM-LV20 promoted wound healing against human keratinocytes (HaCaT) and human skin fibroblasts (HSF) in both time- and dose-dependent manners. In addition, it induced the proliferation of HaCaT but not HSF cells. Of note, OM-LV20 showed strong wound healing-promoting activity in a mice model of full-thickness skin wound. Our research indicates the cellular and animal level wound healing potential of OM-LV20, and thus provides a novel bioactive peptide template for the development of wound healing agents and medicine.

Preoperative 3D and 4D-CT imaging using 640-Multislice CT (640-MSCT) in diagnosis of female urethral diverticulum.

OBJECTIVE: To determine the sensitivity and specificity of 640-Multislice CT (640-MSCT) in diagnosing the female UD. MATERIALS AND METHODS: We investigated 16 patients with symptomatic UDs preoperatively in our hospital from August 2010 to March 2016. The patients' average age was 38.8 years. All patients were performed 640-MSCT of pelvis; then, 3D and 4D images were reconstructed preoperatively. RESULTS: In 3D and 4D-CT images, out of 16 patients, thirteen patients had one ostium, two had 2 ostia and one had 3 ostia. Out of those thirteen patients, eight patients' ostia were located at 5 o'clock and five patients' at 7 o'clock. Patients with 2 ostia location were at 5 and 6 o'clock and 5 and 7 o'clock, respectively. Patients with 3 ostia location were at 5, 6 and 7 o'clock. The mean distance from the bladder neck to the ostia was 22.5 mm. The shape of UD was out-pouching in 11 patients (68.8%), U-shaped in four patients (25.0%) and circumferential in 1 patient (6.2%). The CT findings were confirmed by surgical findings. CONCLUSIONS: 640-MSCT is a useful tool in identifying UD's shape and ostium (including number, location) before operation. Preoperative 640-MSCT should be an adaptable modality for clinically suspected UD patients. ADVANCES IN KNOWLEDGE: Several imaging methods have been used to diagnose female UD. 640-MSCT may be more suitable to diagnose it for its higher sensitivity and specificity in diagnosis of female UD, especially in identifying UD's shape and number and location of ostium.

A retrospective study evaluating the correlation between the severity of intervertebral disc injury and the anteroposterior type of thoracolumbar vertebral fractures.

OBJECTIVE: To evaluate the correlation between the severity of intervertebral disc injury and the anteroposterior type of thoracolumbar vertebral fractures. METHODS: Fifty-six cases of thoracolumbar vertebral fractures treated in our trauma center from October 2012 to October 2013 were included in this study. The fractures were classified by the anteroposterior classification, whereas the severity of intervertebral disc injury was evaluated using magnetic resonance imaging. The Spearman correlation coefficient was used to analyze the correlation between the severity of intervertebral disc injury and the anteroposterior type of thoracolumbar fractures, whereas a χ2 test was adopted to measure the variability between different fracture types and upper and lower adjacent disc injuries. RESULTS: The Spearman correlation coefficients between fracture types and the severity of the upper and lower adjacent disc injuries were 0.739 (PU<0.001) and 0.368 (PL=0.005), respectively. It means that the more complex Arbeitsgemeinschaft für Osteosynthesefragen (AO) classifications are the disc injury is more severe. There was also a significant difference in the severity of injury between the upper and lower adjacent discs near the fractured vertebrae (p<0.001). CONCLUSIONS: In thoracolumbar spinal fractures, the severity of the adjacent intervertebral disc injury is positively correlated with the anteroposterior fracture type. The injury primarily involves intervertebral discs near the fractured end plate, with more frequent and severe injuries observed in the upper than in the lower discs. The presence of intervertebral disc injury, along with its severity, may provide useful information during the clinical decision-making process.

A retrospective study evaluating the correlation between the severity of intervertebral disc injury and the anteroposterior type of thoracolumbar vertebral fractures

OBJECTIVE: To evaluate the correlation between the severity of intervertebral disc injury and the anteroposterior type of thoracolumbar vertebral fractures. METHODS: Fifty-six cases of thoracolumbar vertebral fractures treated in our trauma center from October 2012 to October 2013 were included in this study. The fractures were classified by the anteroposterior classification, whereas the severity of intervertebral disc injury was evaluated using magnetic resonance imaging. The Spearman correlation coefficient was used to analyze the correlation between the severity of intervertebral disc injury and the anteroposterior type of thoracolumbar fractures, whereas a χ2 test was adopted to measure the variability between different fracture types and upper and lower adjacent disc injuries. RESULTS: The Spearman correlation coefficients between fracture types and the severity of the upper and lower adjacent disc injuries were 0.739 (PU<0.001) and 0.368 (PL=0.005), respectively. It means that the more complex Arbeitsgemeinschaft für Osteosynthesefragen (AO) classifications are the disc injury is more severe. There was also a significant difference in the severity of injury between the upper and lower adjacent discs near the fractured vertebrae (p<0.001). CONCLUSIONS: In thoracolumbar spinal fractures, the severity of the adjacent intervertebral disc injury is positively correlated with the anteroposterior fracture type. The injury primarily involves intervertebral discs near the fractured end plate, with more frequent and severe injuries observed in the upper than in the lower discs. The presence of intervertebral disc injury, along with its severity, may provide useful information during the clinical decision-making process.

T1 finite element model of Kümmell's disease shows changes in the vertebral stress distribution.

The aims of this study were to develop a finite element model of delayed post-traumatic vertebral osteonecrosis, analyze its effect on the vertebral stress distribution, and provide experimental evidence for osteonecrosis as a risk factor for loss of the vertebral corrective angle. Three-dimensional reconstruction was performed on CT data of the lumbar vertebrae from a 29-year-old male without spinal lesions to develop a normal L1-L3 vertebral model and a model with post-traumatic vertebral osteonecrosis at level L2. Vertebral flexion, extension, and lateral bending were simulated using computer software to determine the stress distribution in the cortical and cancellous bone in the two models and the changes in the vertebral stress distribution with the size and location of the cavity. Simulation of a vertebral cavity tended to increase the Von Mises equivalent stress in the vertebral cancellous bone and reduce the equivalent stress in the cortical bone, while the vertebral equivalent stress displayed a reverse distribution. The equivalent stress was increased in both the cancellous and cortical bones with increasing cavity volume, and the equivalent stress in the cortical bone was always smaller than that in the normal vertebrae. Placing the cavity close to the endplate of the vertebrae tended to cause stress concentrations in the cancellous bone around the endplate. The cancellous bone with post-traumatic osteonecrosis tended to experience greater Von Mises equivalent stress than the normal vertebrae. Differences in the cavity volume and location may result in a more severe abnormal stress distribution.

Comparison of biomechanical properties of single- and two-segment fusion for Denis type B spinal fractures.

OBJECTIVE: To compare the biomechanical properties of single- and two-segment fusion for Denis type B spinal fracture. METHODS: Two female patients with Denis type B L1 vertebral fractures were studied. Both patients had achieved intervertebral fusion by 1 year postoperatively, at which time CT data were collected, including data of one patient before and after removal of pedicle screws and of another whose pedicle screws were not removed. The data were imported into Mimics software and T11 -L2 three dimensional models established. After construction of the models, they were imported into ANSYS software. An axial load (260 N) and 10 Nm torque were loaded to simulate the flexion, extension, lateral bending and rotation of the spine, respectively. RESULTS: There was no significant difference in the average displacement of the spine motion between the two-segment and single-segment fusion patients without removal of pedicle screws. However, for all motion forms, the average displacement of the single-segment fusion patient' spine after removal of pedicle screws was significantly greater than that before removal of pedicle screws and that of the two-segment fusion patient. The average Von Mises stress of T11-12 intervertebral disc of two-segment fusion patient was significantly greater than that of the one-segment fusion patient. Moreover, the average Von Mises stress of T11-12 intervertebral disc of single-segment fusion patient was greater before than after removal of pedicle screws. CONCLUSION: Provided there is satisfactory interbody fusion, removal of pedicle screws after one-segment fusion can increase spinal motion, reduce the stress on adjacent intervertebral discs and delay disc degeneration.