Biomechanical study of different fixation with hollow screws in spinal laminoplasty / 中国组织工程研究

BACKGROUND: Spinal lamina reimplantation assisted hollow screw laminoplasty has achieved good clinical efficacy. The search literature found that there is no research at home and abroad on the biomechanical properties of unilateral and bilateral hollow screw fixation. OBJECTIVE: To evaluate the biomechanical property of different fixation with hollow screws in artificial and goat vertebrate laminoplasty. METHODS: A laminoplasty was conducted by using hollow screws. Based on the artificial vertebrate laminoplasty model, new models were generated by simulating unilateral screws fixation with a depth of screw insertion 5 mm (A group), unilateral screw fixation with a depth of screw insertion 8 mm (B group) and bilateral screw fixation with a depth of screw insertion 5 mm (C group). Based on the goat vertebrate laminoplasty model, new models were generated by simulating unilateral screws fixation (A group) and bilateral screw fixation (B group). The pull-out strength and static pressure were tested in the biomechanical testing machine with a sensor. RESULTS AND CONCLUSION: (1) In the artificial vertebrate model, the average pull-out strength of the group B was stronger than that of the groups A and C (P < 0.01); the average pull-out strength of the group A was stronger than that of group C (P < 0.01), the difference was statistically significant (P < 0.05). However, the average static compression of the group A and group B was similar; the average static compression of the group C was lower than that of the groups A and B, and the difference was statistically significant (P < 0.01). (2) In the goat vertebrate model, the average pull-out strength and static compression of the group A were stronger than that of the group B, and the difference was statistically significant (P < 0.05). (3) Results suggest that unilateral screw fixation in the artificial and goat vertebrate laminoplasty can provide sufficient pull-out strength and static compression, and the biomechanical strength is positively related to the depth of the screw.

Clinical results and intramedullary signal changes of posterior decompression with transforaminal interbody fusion for thoracic myelopathy caused by combined ossification of the posterior longitudinal ligament and ligamentum flavum / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Surgical treatment of thoracic myelopathy caused by ossification of the posterior longitudinal ligament (OPLL) and ossification of the ligamentum flavum (OLF) is technically demanding, and the results tend to be unfavorable. Various operative approaches and treatment strategies have been attempted, and posterior decompression with transforaminal thoracic interbody fusion (PTTIF) may be the optimal method with which the anterior-posterior compression was removed in one step. It is comparatively less traumatic with fewer serious complications.</p><p><b>METHODS</b>Sixteen patients with thoracic myelopathy due to concurrent OLF and OPLL at the same level underwent PTTIF. We investigated clinical outcomes and neurological improvements. Magnetic resonance imaging (MRI) was performed on all patients preoperatively and postoperatively, and intramedullary signal changes were evaluated.</p><p><b>RESULTS</b>The mean operating time was 275 minutes, and the mean operative bleeding amount was 1031 ml. Cerebrospinal fluid leakage occurred in three patients and healed well after repair. Neurological symptom deterioration occurred in one patient, but the patient recovered to nearly the preoperative level after methylprednisolone treatment. The follow-up period ranged from 28 to 47 months. The mean score on the Japanese Orthopedic Association scale improved from 4.3±1.2 preoperatively to 7.3±1.7 at 3 months postoperatively to 8.5±1.5 at the final follow-up (P < 0.01), with a recovery rate of (63.6±20.0)%. Postoperative images showed a significant improvement in local kyphosis (P < 0.01). Eleven patients (68.8%) showed increased signal intensity (ISI) on preoperative T2-weighted MRI. At the final follow-up, the intramedullary ISI totally recovered in five patients. Neurological improvement was worse in patients with persistent ISI than in the other patients (P < 0.05).</p><p><b>CONCLUSIONS</b>PTTIF is an effective therapeutic option for combined OPLL and OLF and provides satisfactory neurological recovery and stabilized thoracic fusion through a single posterior approach. Intramedullary signal changes do not always indicate a poor prognosis; only irreversible ISI is correlated with a poor clinical result.</p>

Analysis of axial symptoms after indirect decompression for ossification of the posterior longitudinal ligament of the cervical spine / 中华外科杂志

<p><b>OBJECTIVE</b>To study the etiology and clinical significance of axial symptoms after posterior operative procedures for ossification of the posterior longitudinal ligament (OPLL).</p><p><b>METHODS</b>From February 2005 to February 2010, 76 patients with OPLL treated were retrospectively experienced. There were 34 male and 42 female with average of 52.1 years (range from 37 to 74 years), the average duration of the disease was 32.1 months (range from 11 to 56 months). Nineteen patients underwent traditional laminectomy in group A, 33 patients received open-door laminoplasty in group B and 24 patients underwent lateral mass screw fixation in group C. All patients underwent X-ray examination pre- and post operative, computed tomography were used for diagnosis of OPLL, the recovery rate was calculated using pre- and postoperative Japanese Orthopedic Association (JOA) scores for each patient. Pre- and postoperative cervical curvature index and axial symptoms were measured and compared. χ(2) test and SNK test were used as statistical methods.</p><p><b>RESULTS</b>All patients were followed up for 14 - 35 months, average (21 ± 5) months. Loss of cervical curvature index was 4.2% ± 1.7% in group A, 2.9% ± 2.2% in group B and 2.3% ± 1.9% in group C. The difference was significant in loss of cervical curvature indice between group A and B (q = 2.94, P < 0.01), group A and C (q = 4.23, P < 0.01). The average JOA recovery rate was 58.3% for group A, 64.3% for group B and 66.7% for group C. There was no significant difference in JOA recovery rate among the three groups (P > 0.05). The rate of early evident axial symptoms was 7/19 in group A, 30.3% in group B and 33.3% in group C and the difference was not statistically significant (P > 0.05). The incidence of late evident axial symptoms was 5/19 in group A, 12.1% in group B and 8.3% in group C, the difference was not significant between group B and C (χ(2) = 13.762, P < 0.01), but of statistical difference between group A and B(χ(2) = 6.368, P < 0.01), group A and C (χ(2) = 11.481, P < 0.01). No kyphotic deformity in the group A, no "Close Door" phenomenon in group B and no internal failure in group C.</p><p><b>CONCLUSION</b>The incidence of early axial symptoms are of no significant difference among the three groups, but late axial symptoms are higher in the laminectomy than other groups, which may be associated with loss of cervical lordosis.</p>

Analysis of factors of formation and development about degenerative lumbar scoliosis / 中华外科杂志

<p><b>OBJECTIVES</b>To investigate the correlation between scoliosis angle and the asymmetric index of degenerative lumbar scoliosis, the degree of intervertebral disc degeneration, decreased bone density.</p><p><b>METHODS</b>As a retrospectively study, a total of 96 patients with degenerative lumbar scoliosis were retrospectively enrolled from January 2002 to August 2010 as scoliosis group, meanwhile 96 patients with lumbar spinal stenosis matched in gender, age and body mass index (BMI) were selected as control group. All patients were studied with plain radiographs, MRI and dual energy X-ray absorptiometry at presentation. Radiographic measurements include Cobb angle, the height of the convex and concave side of the apical disc and the contiguous disc superiorly and inferiorly, the height of the convex and concave side of the apical and the contiguous vertebral body superiorly and inferiorly in scoliosis group, the height of L(2-3), L(3-4), L(4-5) discs and the height of L(2-4) vertebral body in control group. The average relative signal intensity of lumbar intervertebral disc and cerebrospinal fluid in T2WI sagittal image was measured in apex intervertebral disc and adjacent discs by Adobe Photoshop 6.0 in scoliosis group, which was measured in L(2-3), L(3-4), L(4-5) disc in control group. The bone density of lumbar, femoral neck, trochanter, and Ward's triangle regions were measured with dual-energy X-ray absorptiometry.</p><p><b>RESULTS</b>The intervertebral disc height in convex side was greater than the height in the concave side [(40 ± 7) mm vs. (28 ± 7) mm, P < 0.01], the vertebral body height in convex side was greater than the height in the concave side [(76 ± 12) mm vs. (72 ± 10) mm, P = 0.016] in scoliosis group. There was significant statistically difference in the degenerative degree of intervertebral discs between two groups (P = 0.003). There was significant statistically difference of the average T-value and the rate of osteoporosis between two groups (P < 0.01). Multiple linear regression analysis showed that the asymmetric disc index, the degenerative degree of intervertebral disc and osteoporosis were the predominant correlative factors, which affected the development of degenerative lumbar scoliosis.</p><p><b>CONCLUSIONS</b>Degenerative lumbar scoliosis is always accompanied by the height asymmetry of intervertebral discs and vertebral body from convex and concavity sides. There is positive correlation between the angle of scoliosis and the asymmetric disc index, the degeneration of intervertebral disc, and negative correlation between the angle of scoliosis and the bone density (T-value).</p>