ABSTRACT
Objective To compare the stability effect of the fixation segment using the new test system based robotics to simulate the complex human movement at natural state about the three-level fixa-tion by using four, five or six pedicle screws in treatment of thoracolumbar burst fractures. Methods Six human cadaveric spines were dissected from T_(11)-L_3. The inferior half part of L_1 vertebral bodies and L_1-L_2 dises were resected to mimie an unstable L_1 burst fracture with loss of anterior column support. Specimens were tested in accordance with the following order:intact, 4,5 and 6 pedicle screws fixation at the three-level fixation. The range of motion (ROM) of the fixation segment (T_(11)-L_3) was measured with the six-freedom degree robotics system controlled by mixed force and displacement during flexion, exten-sion, lateral bending and axial torsion, when the stiffness was calculated. One-way statistieal analysis was used for analyzing the collected data. Results With increased number of screws, the ROM of the fixa-tion segment (T_(11)-L_3) was gradually decreased and the stiffness gradually increased. The ROM under ax-ial rotation of six and five screws group became smaller than four screws group (P < 0.05). The stiffness under axial rotation of six screws group was higher than four screws group (P < 0.05). There was no sta-tistical difference between five screws group and four screws group in regard of the stiffness in axial rota-tion (P > 0.05). There were no significant differences in ROM and stiffness under six different loading directions between six screws group and five screws group (P > 0.05). No statistical difference was observed for three fixation modes in aspects of ROMs and stiffness under flexion-extension or lateral ben-ding (P > 0.05). Conclusions Three-level fixation of burst fractures with five or six screws offers im-proved biomechanical stability compared with traditional four screws fixation. But the difference is insig-nificant between six and five screws fixations.
ABSTRACT
Objective To explore the operative method and clinical effect of total hip arthroplasty with normal prosthesis in treatment of the advanced stage avascular necrosis of femoral head combined with severe femoral anteversion. Methods There were 15 patients ( 15 hips) including nine males and six females, at age range of 30-42 years (mean 37 years). The femoral anteversion was 40°-50° and Harris score of (59 ± 8) points. Total hip arthroplasty with normal prosthesis was performed to reduce the femoral anteversion for 20°-30° and increase the acetabulum anteversion for 10°-15°so as to recover a good involution relationship of the femoral head and the acetabulum and avoid anterior dislocation. The imaging examination and Harris scoring were performed regularly postoperatively. Results A follow-up for mean 2.9 years (2.5-3.7 years) in 15 patients showed that all patients obtained good range of joint motion and good stability of all the hip prostheses. Harris score was (88±6) points at 2 years post-opera-tively, which was significantly better than preoperation (P < 0.01 ). Conclusions Total hip arthro-plasty with normal prosthesis can obtain good involution of the femoral head and the acetabulum in patients with advanced stage avascular necrosis of femoral head combined with severe femoral anteversion by simul-taneously regulating implant angle of femoral prosthesis and acetabular cup, which helps avoid use of small or specially made femoral stem or subtrochanteric derotational osteotomy.
ABSTRACT
[Objective] To explore the effect of B-Twin intervertebral cage for degenerative lumbar instability with posterior mini-incision.[Methods]Thirteen patients(13 disc-spaces)treated with B-Twin intervertebral cage in combination with autogenous morselized bone were enrolled in this study.Among the patients,11 had degenerative instability in L4、5 and 2 in L5S1.Patients were graded postoperatively with JOA scoring system.[Results]The lower back pain and leg pain were relieved significantly in all patients after operation.All were followed-up for an average of 16.2 months,and the JOA scores inproved from 4.2 preoperatively to 14.4 at the final follow-up.The good to excelleat rate was 92.3%.The bony fusions presented in an average of 19.8 weeks postoperatively by CT scan.Neither cage loosening nor neurological injury was found.[Conclusion]B-Twin intervertebral cage combined with autogenous morselized bone insertion for lumbar degenerative instability by posterior mini-incision operation is a good technique,which could achieve satisfactory clinical results with less injury.