| Objectives: Instantaneous centers of rotation (ICR) can reflect the motion characteristics of lumbar spine, considering translation and rotation simultaneously. To determine the centers of rotation in the lumbar spine with computer and digitizer, calculations can be more accurate,, convenient and rapid. In this study, a special computer program is composed, with which we calculate and analyze the ICRs in lumbar spine of those patients who undergo fenestration and discectomy. To take advantage of digitized technique to investigate the effects of the fenestration and discectomy on stability of the lumbar spine, to provide biomechanical evidence for clinical treatment with this procedure and to supply an objective quantitative parameter for choosing surgery fashion and evaluating therapy effects are objectives of this study.Methods: Thirty patients were selected in this study. All of them had lumbar disc herniation at single level that was verified by imaging examination. These patients must be those range of motion in lumbar spine was not limited. Eighteen men and 12 women, aged 19-50 years (mean, 44.9years) ,were studied. The level of disc herniation was L4-5 in 12 patients, L5-S1 in 18 patients. The mean preoperative duration of radicular and/or cauda equina symptoms was 11.8 months (range, 20 days - 3 years). All of these patients was treated with surgery 梖enestration and discectomy. Three days after the operation, back and abdominal muscles exercises in bed were done. Seven days later, the patients began to walk gradually. At the 2nd day before operation and the 14th day after surgery, lateral radiographs were taken to the lumbar spine segment (in which disc herniated) in the standing position. These radiographs included those of full extension > semiextenskwu upright position^ semiflexion and full flexion. On each one of the radiographs, auxiliary lines and points were drawn at the same position of lower vertebra and of upper vertebra, respectively. A planer coordinate system was defined whose X axis was the upper border of the lower vertebra of the pair under study, and, whose origin was the superoposterior corner of this vertebral body. From these radiographs, four graphs were selected, between which motion intervals were greater. Auxiliary lines and points on the four radiographs were transferred onto an acetate sheet on which a coordinate system had been established. This acetate sheet was then digitized using a digitizer-microcomputer. A specially designed program was used and the motion from full extension to full flexion of thesegment under study was analyzed. To each set of radiographs, following parameter were displayed: X coordinate and Y coordinate of three ICRs and of the mean ICR^ length of centrode (LX area of centrode (S) and segmental range of motion (ROM) . All data from preoperative radiographs and postoperative radiographs were analyzed with SPSS 10.0 program. Paired Student's t test for self-contrast were used. Statistical significance was defined at P<0.05.Results: To 12 L4-5 segments, average X coordinate of ICR, centrode length > centrode area and segmental ROM increased compared with that before operation, and average Y coordinate decreased. But all of them had no statistical difference (P>0.05) . To 18 L5-S1 segments, average Y coordinate became smaller after operation, and the difference was significant (P<0.05) . Other parameters of them increased after surgery, but no significant difference was found between preoperation and postoperation(P>0.05) . Before and after surgery, the mean centrode length of L4-5 segments was 46.9 mm and 50.44 mm, respectively, and the average ICR coordinate was (11.56, 1.97) , respectively. To L5-S1 segments, preoperatively and postoperatively, the centrode length was 45.76 mm and 48.98 mm, respectively, and the average ICR coordinate was(10.51, 4.00) and (10.66, 0.62) , respectively. Above values were closed to those results that foreign researchersobtained form cadaver lumbar spines with moderate degenerati... |
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