Objective:To investigate the clinical effect of Dynamic neutralization system applied to the treatment of lumbar degenerative diseases with fatty infiltration of multifidus muscle.Methods:From Jan 2015 to Dec 2017, a total of 53 patients of lumbar degenerative diseases with multifidus fatty infiltration treated by Dynesys in our hospital were analyzed, included 21 males and 32 females, aged 66.2±7.4 (range 48-81) years. There were lumbar spinal stenosis in 37 casesand lumbar disc herniationin 16 cases; the index level included L 2-S 1 in 3 cases, L 3-S 1 in 13 cases, L 2-L 5 in 5 cases, L 4-S 1 in 17 cases, and L 3-L 5 in 15 cases. The pedicle screws were inserted at the point of intersection of the outer edge of superior articular process and the midline of transverse process. After discectomy of herniated disc and hyperplastic ligamentum flavum, the distance between the upper and lower pedicle screws was measured and then the spacer of the corresponding length was cut out. Finally, the spacer was placed and fixed between the upper and lower pedicle screws by the elastic rope. The degree of multifidus fat infiltration, lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), sacral slop (SS), range of motion (ROM), intervertebral height (IH), Japanese Orthopaedic Association (JOA) score, Oswestry disability index (ODI), the MOS 36-item short-form health survey (SF-36) and visual analog scale (VAS) were evaluated postoperatively. Results:The operation was performed successfully in all the patients. The operation duration was 173.5±64.7 (range 125-240) min. Intraoperative blood loss was 469.5±118.2 (range 380-620) ml. The patients were followed up for 47.9±6.7 (range 38-62) months averagely. At the last follow-up, the degree of fatty infiltration of the multifidus muscle showed no further progress by MR scan. There was no significant difference in ROM and IH at different time points preoperativelyand postoperatively. The LL recovered from 37.6°±8.8° to 43.2°±9.1°, the PT decreased from 24.7°±9.3° to 20.5°±5.1°, and the SS increased from 22.1°±7.7°to 26.3°±8.0°. The JOA score increased from preoperative 6.4±1.2 to 20.6±2.8, ODI decreased from preoperative 50.6%±11.3% to 13.0%±3.4%, SF-36 increased from preoperative 81.5±3.6 to 95.5±4.2, and the VAS decreased from preoperative 4.2±1.0 to 1.1±0.6. One patient experienced loosening and displacement on the left side pedicle screw of the L2 vertebral body 3.5 years after operation, and herclinical symptom improved significantly after conservative treatment.Conclusion:Dynesysis is safe and effective for the treatment of lumbar degenerative diseases with fatty infiltration of multifidus muscle, and it can restore the complete structure and function of tension band at lower back and prevent the progress of multifidus muscle fat infiltration combined with postoperative rehabilitation training.

BACKGROUND:The traditional view is that proximal fibular fractures do not require fixation.Others and our research suggest that the proximal fibular structure plays an important role in the stability of the posterolateral structure of the knee joint,and its mechanism of action is worth studying. OBJECTIVE:To investigate the biomechanical effects of proximal fibular fractures on various structures of the knee joint in an extended state. METHODS:Finite element method was used to conduct simulated biomechanical experiments.A healthy young male volunteer was selected to establish a finite element model of the knee joint in an extended state using MRI and CT image data,and four proximal fibular shapes were simulated(Model A:intact,Model B:1 cm fracture below the fibular head,Model C:1 cm tip defect fracture from the proximal end of the fibula to the distal end,and Model D:2 cm bone defect from the proximal end of the fibula).A longitudinal concentrated load of 1 500 N was applied to the femoral shaft to compare and analyze the distribution and changing trend of the maximum equivalent stress and maximum first principal stress of each structure of the knee joint in an extended state under four working conditions. RESULTS AND CONCLUSION:(1)In Model A,the maximum equivalent stress in the tibial cartilage and lateral compartment of the meniscus was greater than that in the medial compartment,while the maximum first principal stress in the tibial plateau and medial compartment of the meniscus was greater than that in the lateral compartment.The maximum equivalent stress of the medial condyle of the femoral cartilage was greater than that of the lateral condyle,and the maximum first principal stress of the medial condyle of the femoral cartilage was greater than that of the medial condyle.(2)Compared to Model A,there was no significant difference in the magnitude and distribution of the maximum equivalent stress and maximum first principal stress in the cartilage and meniscus of Model C.(3)Compared to Model A,the maximum equivalent stress increase amplitude of Model B was in the order of medial tibial cartilage(14.9％),medial condyle of femoral cartilage(13.6％),and medial meniscus(6.6％).The maximum first principal stress increase amplitude was the medial meniscus(11.06％),the medial tibial cartilage(8.65％),and the medial condyle of the femoral cartilage(7.46％).The maximum equivalent stress increase amplitude of the ligament was as follows:popliteal arch ligament(33.2％)>anterior cruciate ligament(21.3％)>fibular collateral ligament(17％)>posterior cruciate ligament(14.3％)>anterior lateral collateral ligament(13.2％)>medial collateral ligament(10.1％).(4)Compared to Model A,the maximum equivalent stress increasing trend of Model D followed the medial tibial cartilage(19.5％),femoral cartilage medial condyle(17.9％),and medial meniscus(9.9％).The maximum first principal stress in sequence was the medial meniscus(14.04％),the medial tibial cartilage(13.03％),and the medial condyle of the femoral cartilage(11.37％).The increasing trend of maximum equivalent stress in ligaments was as follows:anterior cruciate ligament(25.2％)>posterior cruciate ligament(18.9％)>medial collateral ligament(18.5％)>anterior lateral collateral ligament(12.7％).(5)It is suggested that when the knee joint is extended,a 1 cm fracture below the fibular head and a 2 cm fibular tip bone defect have a significant impact on the structure of the medial ventricular cartilage,anterior cruciate ligament,and posterior lateral ligament complex.

Objective To investigate the effect of medial collateral ligament (MCL) repair and coronoid process fracture fixation on stability of the Terrible Triad of the elbow. Methods CT and MRI scan images of elbow joints from one healthy 28-year-old male volunteer were used to establish three elbow models. Model A: normal model. Model B: repair of coronoid process fractures, without MCL repair. Model C: repair of MCL, without repair of ulnar coronoid processes. Longitudinal loads were applied on the three models to analyze the displacement and stress distributions of the elbow joint under different working conditions and compare the stability of the elbow joint. Results The displacement and stress distributions of the three models were similar. The maximum displacement and maximum stress of the articular surface were located at the ulna pulley notch, while the minimum displacement was located at the coronoid process and its medial side. The minimum stress was located at the lower lateral side of the coronoid process. There were no statistical differences in the maximum displacement and stress among the three models (P>0.05). Conclusions When the lateral column is stable, the effect of repairing the MCL and fixing the fracture block of ulnar coronoid process is similar.