Objective Peri pheral nerve injury is a common cl inical disease, to study the effects of the physical therapy on the regeneration of the injured sciatic nerve, and provide a reference for cl inical treatment. Methods Sixty-four female adult Wistar rats (weighing 252-365 g) were chosen and randomly divided into 4 groups (n=16): group A, group B, groupC, and group D. The experimental model of sciatic nerve defect was establ ished by crushing the right sciatic nerve in groups B, C, and D; group A served as the control group without crushing. At 2 days after injury, no treatment was given in group B, electrical stimulation in group C, and combined physical therapies (decimeter and infrared ray) in group D. At 0, 7, 14, and 30 days after treatment, the sciatic nerve function index (SFI) and the motor nerve conduction velocity (MNCV) were measured, and morphological and transmission electron microscopy (TEM) examinations were done; at 30 days after treatment, the morphological evaluation analysis of axons was performed. Results At 0 and 7 days after treatment, the SFI values of groups B, C, and D were significantly higher than that of group A (P lt; 0.05); at 14 and 30 days after treatment, the SFI value of group D decreased significantly, no significant difference was observed between group D and group A (P gt; 0.05) at 30 days; whereas the SFI values of groups B and C decreased, showing significant difference when compared with the value of group A (P lt; 0.05). At 0, 7, and 14 days after treatment, the MNCV values of groups B, C, and D were significantly lower than that of group A (P lt; 0.05), and there were significantly differences between group B and groups C, D (P lt; 0.05); at 14 days, the MNCV value of group D was significantly higher than that of group C (P lt; 0.05); and at 30 days, the MNCV values of groups B and C were significantly lower than that of group A (P lt; 0.05), but there was no significant difference between group D and group A (P gt; 0.05). At 0 and 7 days, only collagen and l i pid were observed by TEM; at 14 and 30 days, many Schwann cells and perineurial cells in regeneration axon were observed in groups B, C, and D, especially in group D. Automated image analysis of axons showed that there was no significant difference in the number of myelinated nerve fibers, axon diameter, and myelin sheath thickness between group D and group A (P gt; 0.05), and the number of myelinated nerve fibers and axon diameter of group D were significantly higher than those of groups B and C (P lt; 0.05). Conclusion Physical therapy can improve the regeneration of the injured sciatic nerve of rats.
ObjectiveTo investigate the biomechanical characteristics of the proximal tibia (including cortical bone, cancellous bone, and bone cement) after lateral unicompartmental knee arthroplasty (L-UKA) under conditions of normal bone mass, osteopenia, and osteoporosis through finite element analysis of the tibial plateau, and to evaluate the impact of osteoporosis on the risk of postoperative tibial fracture from a biomechanical perspective, focusing on stress, strain, and deformation distribution patterns. MethodsBased on CT data of the tibia from a healthy adult male volunteer, a three-dimensional finite element model of L-UKA was established, including the femoral component, tibial component, ultra-high molecular weight polyethylene insert, bone cement, medial tibial cartilage, and tibia (comprising cortical and cancellous bone). Three groups of bone density parameters were defined: normal bone mass (T-score ≥?1.0SD), osteopenia (T-score –2.5SD-–1.0SD), and osteoporosis (T-score ≤–2.5SD). Different bone conditions were simulated by adjusting the elastic modulus of cortical and cancellous bone. Boundary conditions included complete constraint of the distal tibia, application of a 600 N vertical load on the femoral component, and a 400 N vertical load on the medial tibial cartilage to simulate single-leg stance during slow walking. The maximum stress, maximum strain, and maximum deformation of key structures were measured. Results As bone mass decreased, the biomechanical responses of bone and bone cement changed significantly. Specifically, the maximum stress, maximum strain, and maximum deformation of cortical bone and the bone cement layer increased markedly. For cancellous bone, the maximum stress decreased, while the maximum strain and maximum deformation increased. The maximum stress of the insert were similar across the three groups, with minimal variation (<1%); the peak stress was located at the contact area between the insert and the femoral component. ConclusionThe biomechanical risk of tibial fracture after L-UKA significantly increases in patients with osteoporosis, particularly for periprosthetic stress or fragility fractures.
