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With the increasing advocacy for total disc replacement (TDR) as a potential alternative to fusion in the management of lumbar degenerative disc disease, intradiscal pressures (IDPs) and facet joint stresses at the adjacent levels of spine have generated considerable interest. The purpose of this study was to compare adjacent-level IDPs and facet joint stresses among TDR, discectomy, and fusion.Ten fresh human cadaveric lumbar specimens (L2-S1) were subjected to an unconstrained load in axial torsion, lateral bending, flexion, and extension by using multidirectional flexibility test. Four surgical treatment modes-control (disc intact), discectomy, TDR, and fusion-were tested in sequential order at L4-5. During testing, the IDPs and facet forces following each treatment were calculated at the adjacent vertebral levels (L3-4 and L5-S1).Intradiscal pressures and facet force pressures were similar between the intact condition and the TDR reconstruction at the L3-4 and L5-S1 levels under all loading conditions (p0.05). Compared with the intact and TDR groups, the discectomy and fusion groups had higher IDPs at the L3-4 and L5-S1 levels under all loading conditions (p0.05). No significant difference in the facet force pressure was noted among the intact, discectomy, and TDR groups at the L3-4 and L5-S1 levels under any loading conditions (p0.05). However, the facet force pressure produced for fusion was significantly higher than the mean values obtained for the intact, discectomy, and TDR groups at the L3-4 and L5-S1 levels under all loading conditions (p0.05).Lumbar TDR maintained adjacent-level IDPs and facet force pressures near the values for intact spines, whereas adjacent-level IDPs tended to increase after discectomy or fusion and facet forces tended to increase after fusion.

To develop a new internal fixation device and the matching tools for subtrochanteric fracture, investigate the biomechanical features thereof, and compare its effects with those of other instruments.A new internal fixation device, static three dimensional screw-plate system: (STDSP) was developed based on the anatomical parameters and the biomechanical characteristics of proximal femur and combined with the biomechanical advantages of the model of three-dimensional plate and multiple-screws plate fixation. Sixteen paired cadaveric adult femurs were randomly divided into 2 equal groups: fracture healing group undergoing insertion of implant and then taking out thereof with a nail left, and fracture group with a trapezoid defect to mimic subtrochanteric fracture 4 of which were fixed with dynamic hip screw (DHS) and STDSP or Gamma nail and STDSP. All the specimens underwent A-P position four point bending test, axial compression test, torsion test, and destroyable test.(1) In the fracture group, A-P position four point bending test showed that the stretch displacement of STDSP group was (0.221 +/- 0.089) mm, significantly smaller than that of the Gamma nails group [(0.506 +/- 0.086) mm, t = 38.278 P = 0.000]; Axial compression test showed that the inferior displacement of the STDSP group was (2.804 +/- 0.585) mm, significantly larger than that of the Gamma nail group [(1.874 +/- 0.549) mm, t = -5.454, P = 0.012]; Torsion test showed that the torque values at 50 and 100 of the STDSP group were (3.78 +/- 0.84) J and (2.3 +/- 1.08) J, both significantly larger than those of the Gamma nail groups [(2.3 +/- 1.08) J and (4.35 +/- 1.81) J, t = -4.729 P = 0.018, and t = -3.227 P = 0.048] and those of the DHS group [(7.3 +/- 1.273) J and (4.325 +/- 0.88) J respectively, t = -3.242 P = 0.048]; and torsion destroyable test showed that the torque values at 200 of the STDSP group was (21.88 +/- 2.51) J, significantly larger than those of the Gamma nail and DHS groups, [(14.36 +/- 5.01) J and (15.475 +/- 1.924) J and (12.075 +/- 1.179) J, t = -3.323 P = 0.048, t = - 3.732 P = 0.034]. (2) In the fracture healing specimens, A-P position four point bending test showed that the radial degree displacement of the STDSP group was (1. 050 +/- 0.316) mm, significantly smaller than that of the DHS group [(1.261 +/- 0.364) mm, t = 3.4 P = 0.042].More capable of resisting bending than DHS and less capable of resisting axial compression, STDSP is an excellent internal fixator with good biomechanical feature in treating subtrochanteric femoral fracture.

To research the biomechanic property of 4 tendon grafts.The biomechanic properties of profound hypothermua froze tendon allogeneic grafts, profound hypothermua froze and dried allogeneic tendon grafts, autologous tendon grafts and allogeneic tendon grafts without intervention were tested.The biomechanic property of allogeneic tendon grafts with profound hypothermua freezing and profound hypothermua freezing and dying was better than that of allogeneic tendon grafts without intervention (P0.05). No significant difference was seen between the former 2 grafts and dried autologous tendon grafts (P0.05).Allogeneic tendon grafts with profound hypothermua freezing and profound hypothermua freezing and drying, have the same biomechanic property as dried autologous tendon grafts and can be used in clinical practice.