Biomechanical Comparision And Clinical Research Of Lower Thoracic Spinal Stability After Transarticularis Approach Discectomy

Objective: To compare the stability of the lower thoracic spine in different facetectomy states through biomechanical measurement in the cadaver spine processed by transarticularis approach discectomy, sequentially, providing biomechanical evidence for the clinical application of transarticularis approach discectomy. To evaluate clinical index of transarticularis approach discectomy in lower thoracic spine, providing feasibility evidence for clinical application of this surgical procedure.Method: Biomechanics test: The lower thoracic spine of 6 fresh cadaveric specimens from T₉ to L₁ were obtained. The age at the time of death ranged from 25 to 48 years old. The average age is 37 years old. All specimans were evaluated radiographically before testing, to exclude congenital deformity, fracture, dislocation, degeneration disease. The specimens were dissected with preservation of osteoligamentous structures. The two ends (T₉ and L₁) were Embedded using tooth powder separately. The lower thoracic spines were double-bagged and frozen at -20℃until the day of testing. Before testing the specimens were graded thawed out. Then, trans-articularis approach discectomy models were made in different degree. Every specimen were performed the following processes:â‘ ULF(T_11-12 Unilateral facetectomy),â‘¡ULF+D(T_11-12 Unilateral facetectomy+discectomy),â‘¢ULF+L+D (T_11-12 Unilateral facetectomy + Laminectomy +discectomy),â‘£BLF+L+D(T_11-12 Bilateral facetectomy+ Laminectomy +discectomy),⑤T_11-12 fixation,â‘¥BLF+L+D(T_10-12 Bilateral facetectomy+ Laminectomy +discectomy),⑦T_10-12 fixation. Then in these seven states and intact state,all specimen were tested in turn, separatedly, in flexion, extending, left and right rotation, left and right bending six directions. Each test was repeated for three cycles, consisting of 20 seconds. In the third cycle, the range of motion (ROM) was recorded for analysis. The data obtained from all test were presented in the original scales as mean±standard deviation. The loading strength was from 50N to 100N. Paired t-test was used as statistics analysis method. Statistical significance level for the test was set at P<0.05. Clinical research: This is a retrospective study. From January 2001 to June 2005, 38 patients (12 males, 26 females)lower thoracic disc herniation (TDH) were treated in our hospital, being 73.08% of all TDH patients in the same period. In 38 patients, 23central herniation types, 15lateral herniation types. Clinical situation was classified three categories. 1.intercostal nerve symptom 2.spinal pressed symptom 3.horsetail nerve symptom. Before operation, in addition to anteroposterior, lateral thoracic or thoracolumbar spine radiographs and CT/MRI were obtained in all patients. In all patients, laminectomy 4 cases, anterolateral approach 11cases and trans-articularis approach 23 cases. All 38 patients were followed up for an average time of 2.6 years (range 1.1-3.8 years). According to Otani's classification criterion, clinical symptoms were evaluated at preoperation, 1week postoperative, 1year follow-up. In the same time, blood loss and operating time of the three type operation were evaluated.Results: Biomechanical testing results: (1) seven states comparing with IS: ROMs increase slightly in flexion, extension and lateral bending, while increasing significantly (P<0.05) in axial rotation following T_11-12ULF and T_11-12ULF+D. ROMs increase significantly (P<0.01) in flexion, extension, lateral bending and axial rotation directions following T_11-12ULF+L+D, T_11-12BLF+L+D, T_10-12 BLF+L+D, respectively. The stability of lower thoracic spine was damaged significantly . Following decompression and T_11-12 fixation, there were significant (P<0.01)increase of stability in extension and lateral bending, and there were no significant difference in axial rotation and flexion directions. ROMs decrease significantly (P<0.01) in flexion, extension and lateral bending following T_10-12 fixation, while in axial rotation direction, there was no significant change. (2) single level comparing with double levels: Comparing T_11-12BLF+L+D with T_10-12 BLF+L+D, there were significant (P<0.01)difference in all six direction ROMs. Comparing T_11-12 fixation with T_10-12 fixation, ROMs was changed slightly in axial rotation, while increasing significantly (P<0.01) in other directions.Clinical research results: The intraoperative blood loss was 190.00±23.00ml in laminectomy group, 260.00±26.00 ml in trans-articularis approach group and 410.00±28.00 ml in anterolateral approach group. The operation lasting time was 90.10±32.60min in laminectomy group, 118.60±25.20 min in trans-articularis approach group, 150.20±38.50 min in anterolateral approach group respectively. There were significant difference in blood loss and operation lasting time between laminectomy group and trans-articularis approach group(P=0.035 and P=0.017). There were significant difference in blood loss and operation lasting time between anterolateral approach group and trans-articularis approach group(P=0.005 and P=0.003). Trans-articularis approach group was superior to anterolateral approach group obviously. The clinical rate of excellent and good was 33.33% in laminectomy group, 86.96% in trans-articularis approach group and 81.82% in anterolateral approach group. Comparing laminectomy group and trans-articularis approach group, there was significant difference(P=0.0128),the latter is superior to the former in the rate of excellent and good. There were no significant difference between anterolateral approach group and trans-articularis approach group in the rate of excellent and good.(P=0.8792).Conclusion: Articulations zygapophysiales is an important role to the stability of lower thoracic spine. Following unilateral facetectomy thoracic discectomy, the stability of lower thoracic spine in axial rotation was damaged. After proceeding of bilateral facetectomy thoracic discectomy, the stability of lower thoracic spine in all six directions were damaged significantly. The stability of lower thoracic spine could be enhanced by proceeding of single level or double levels fixation. Following clinical researching, trans-articularis approach method is superior to anterolateral approach method in operation lasting time and blood loss. In curative effect, trans-articularis approach method is superior to laminectomy method, and no significant difference with anterolateral approach method.