Effects of shear force on intervertebral disc: an in vivo rabbit study.

PURPOSE: A new in vivo rabbit model was developed to investigate the effects of shear force on intervertebral disc (IVD). METHODS: Japanese white rabbits (n = 38) were used for this study. The L4/5 discs in Group A (n = 10) were subjected to a constant shear force (50 N) using a custom-made external loading device for 1 month; in Group B (n = 10) for 2 months; whereas in Group C (n = 10), loading device was attached to the spine but the discs remained unloaded. Group D (n = 8) was a non-operated intact control group. After loading, the loading devices were taken out and the animals were given X-ray and MRI examination. After X-ray and MRI examination, the animals were euthanized for histological analysis. RESULTS: After 1 and 2 months of loading, radiographic findings showed significant disc height narrowing in L4/5 discs of the animals in loading groups, and slight lumbar spondylolisthesis in some animals of Group B. MRI showed a significant decrease in nucleus pulposus (NP) area and signal intensity from T2-weighted images. Histologically, loss of normal NP cells and disorganization of the architecture of the annulus occurred, and proteoglycan stain decreased. CONCLUSIONS: The results of this study suggest that disc degeneration can be induced by hyper-physiological shear loading in the rabbit IVD. Long-term shear loading may result in structural disc failure inducing lumbar spondylolisthesis and progressive disc degeneration, which, however, has to be proven by further studies.

Computed tomography morphometric analysis of C2 translaminar screw fixation of Wright's technique and a modified technique in the pediatric cervical spine.

PURPOSE: To establish reference data on the dimensions of C2 lamina to guide the use of translaminar screws with Wright's technique and a modified technique for pediatric patients in different age groups. METHODS: 113 pediatric patients were divided into six age groups, and their cervical vertebrae were studied on CT scans. Laminar height, width, length and screw angle were measured. Statistical analysis was performed using Student t tests, Pearson's correlation and linear regression analysis. RESULTS: Mean laminar height was 10.95 ± 2.81 mm, and mean width was 6.01 ± 0.90 mm. For Wright's technique, mean laminar length was 30.65 ± 3 mm, and the screw angle was 56.02° ± 3.62°. For the modified technique, mean laminar length was 22.07 ± 2.38 mm, and the screw angle was 67.40° ± 3.39°. 95.6% (108/113) of the children could insert a screw into the lamina (laminar width ≥ 4.5 mm), 72.6% (82/113) could accept bilateral translaminar screws (laminar width ≥ 4.5 mm and laminar height ≥ 9 mm). CONCLUSION: Our investigation provides insight into the anatomy of C2 lamina in six pediatric age groups. Compared to adults, the benefits of C2 translaminar screws fixation are more obvious in the pediatric spine which has a large C2 lamina. Compared to Wright's technique, the modified technique should insert a screw with bigger insert angle and shorter screw length.

An imaging study of the compressed area, bony fragment area, and the total fracture-involved area in thoracolumbar burst fractures.

STUDY DESIGN: Imaging study. SUMMARY OF BACKGROUND DATA: X-ray and computed tomography (CT) sagittal reconstruction images are used to evaluate the stability of the spine. However, we did not know the extent of difference between them. OBJECTIVE: The aim of the study was to compare the differences seen in thoracolumbar burst fractures on lateral radiographs and CT sagittal reconstruction images and investigate their clinical relevance. MATERIALS AND METHODS: Lateral radiographs and CT sagittal reconstruction images of 45 patients with thoracolumbar burst fractures were used to record the following measurements: the compressed area of the fractured vertebrae, from lateral radiographs, and the sagittal compressed area, bony fragment area, and total fracture-involved area, from CT sagittal reconstruction images. RESULTS: The percentage of compressed area of fractured vertebrae was 29.32±13.80% on lateral radiographs and 27.93±12.21% on CT sagittal reconstruction images; there was no significant difference between them (P>0.05). The percentage of total fracture-involved area was 53.20±20.64% on CT sagittal reconstruction images, higher than the compressed area measured on lateral radiographs (P<0.01) and CT sagittal reconstruction images (P<0.01). The percentage of bony fragment area was 25.27±15.18% on CT sagittal reconstruction images; there was no significant relationship between bony fragment area and the compressed area (r=0.1258, P>0.05). CONCLUSIONS: The compressed area of fractured vertebrae on lateral radiographs could not represent the fracture-involved area and underestimated the total fracture-involved area. We suggested that the above 3 parameters could be easily obtained on CT sagittal reconstruction images, which might be better for assessing the potential instability of the thoracolumbar burst fracture and could become a valuable and indispensable examination for therapeutic decision making.

[Pressure side and tension side comminution of femoral neck cortex are independent risk factors for aseptic necrosis after femoral neck fracture surgery].

OBJECTIVE: To investigate the related factors of aseptic necrosis of femoral head after closed reduction and internal fixation of femoral neck fracture. METHODS: From January 2009 to January 2016, 236 patients with femoral neck fracture were treated with closed reduction and internal fixation with 3 hollow lag screws, including 111 males and 125 females, aged from 19 to 89 (50.17±12.88) years. According to the follow-up results, the correlation of aseptic necrosis of femoral head was analyzed. Univariate analysis of age, gender, injured side, body weight, injury mechanism, preoperative waiting time, Garden classification and whether there was comminution of femoral neck cortex was conducted to obtain the independent variables with significant difference. Then binary logistic regression analysis was conducted to explore the independent risk factors of avascular necrosis of femoral head. RESULTS: The average follow-up period of 236 cases was 4.58 years. There were significant differences in the range of injury (24.69% vs. 5.16%, χ2=19.405, P=0.000), operation waiting time>48 hours (20.00% vs. 6.38%, χ2=10.065, P=0.002), Garden type Ⅲ/Ⅳ (18.52% vs. 2.97%, χ2=13.357, P=0.000), femoral neck cortex comminution (66.67% vs. 4.88%, χ2=39.968, P=0.000). Multivariate logistic regression analysis showed that:injury mechanism [high energy injury, Exp (B)=4.397, 95%CI=(1.672-11.562), P=0.003], preoperative waiting time >48 h [Exp (B)= 3.060, 95%CI=(1.176-7.966), P=0.022], comminution of femoral neck cortex [comminution of femoral neck pressure side cortex, Exp (B)=3.944, 95%CI=(1.245-12.494), P=0.020;comminution of femoral neck pressure side and tension side cortex, Exp(B)= 23.761, 95%CI=(3.805-148.374), P=0.001) were independent risk factors for avascular necrosis after internal fixation of femoral neck fracture. Garden type Ⅲ/Ⅳ was not an independent risk factor in this study [Exp (B) = 1.985, 95%CI=(0.436-9.032), P=0.375]. CONCLUSION: High energy injury, preoperative waiting time (>48 h) and comminution of femoral neck cortex were independent risk factors for aseptic necrosis of femoral head. In addition, cortical comminution on the pressure side and tension side of the femoral neck is a strong prognostic risk factor for aseptic necrosis of the femoral head, because it indicates a more serious and complex injury mechanism.

A 3D navigation template for guiding a unilateral lumbar pedicle screw with contralateral translaminar facet screw fixation: a study protocol for multicentre randomised controlled trials.

INTRODUCTION: The incidence of lumbar disc degeneration disease has increased in recent years. Lumbar interbody fusion using two unilateral pedicle screws and a translaminar facet screw fixation has advantages of minimal invasiveness and lower costs compared with the traditional methods. Moreover, a method guided by a three-dimensional (3D) navigation template may help us improve the surgical accuracy and the success rate. This is the first randomised study using a 3D navigation template to guide a unilateral lumbar pedicle screw with contralateral translaminar facet screw fixation. METHODS AND ANALYSIS: Patients who meet the criteria of the surgery will be randomly divided into experimental groups and control groups by a computer-generated randomisation schedule. We will preoperatively design an individual 3D navigation template using CATIA software and MeditoolCreate. The following primary outcomes will be collected: screw angles compared with the optimal screw trajectories in 3D digital images, length of the wound incision, operative time, intraoperative blood loss and complications. The following secondary outcomes will be collected: visual analogue scale (VAS) for back pain, VAS for leg pain and the Oswestry Disability Index. These parameters will be evaluated on day 1 and then 3, 6, 12 and 24 months postoperatively. ETHICS AND DISSEMINATION: The study has been reviewed and approved by the institutional ethics review board of the Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University. The results will be presented at scientific communities and peer-reviewed journals. TRIAL REGISTRATION NUMBER: ChiCTR-IDR-17010466.

Computed tomographic morphometric analysis of the pediatric occipital condyle for occipital condyle screw placement.

STUDY DESIGN: This study is a computed tomographic (CT)-based morphometric analysis of the pediatric occipital condyles as related to occipital condyle screw placement. OBJECTIVE: To quantify reference data concerning the dimensions of the immature occipital condyles to guide the placement of occipital condyle screw. SUMMARY OF BACKGROUND DATA: To the best of our knowledge, no published study has provided insight into the anatomy of occipital condyle of the pediatric population with different age groups. METHODS: Sixty-nine pediatric patients were divided into 4 age groups, and their occipital condyles were studied on CT scans. Condylar length, width, height, sagittal angle, and sagittal angle lengths were measured on Philips Brilliance 16 CT. RESULTS: The mean pediatric coronal height, sagittal length, and axial width noted statistically significant age-related differences were 9.0 mm, 21.3 mm, and 9.8 mm, respectively. The mean sagittal angle for all patients was 27.2 ± 5.1° (range, 15.1-41.0°). In 82.6% (114/138) of the occipital condyles, the anatomy could accept the occipital condyle screw (width ≥8 mm and height ≥6.5 mm). CONCLUSION: Our investigation provides insight into the anatomy of occipital condyle of the pediatric population with different age groups. As the pediatric occipital condyles have sufficient occipital bone for appropriate fixation or fusion, the occipital condyle screws fixation is a feasible technique for children. Even so, given the evolution of this technique being still in its infancy and the complexity inherent to the craniovertebral junction, a careful radiological analysis of occipital condyle must be required in preoperative planning and feasibility determination. LEVEL OF EVIDENCE: N/A.