Biomechanical Study of Novel Articular Process Fixation System Combined with Unilateral Pedicle Screw Fixation / 医用生物力学

Objective To study the stability of lumbar spine after transforaminal lumbar interbody fusion (TLIF) surgery combined with a novel articular process fixation system (APFS). Methods Based on the validated finite element model of L3-S1 intact segment (Model A), TLIF surgery was simulated to establish bilateral pedicle screw TLIF model (Model B), right unilateral pedicle screw TLIF model (Model C), APFS combined with right pedicle screw fixation TLIF model (Model D). The range of motion (ROM) of the lumbar spine model and stress distributions on pedicle screws, APFS and interbody fusion cages under different working conditions were observed. Results The overall ROMs of Models B, C, and D under different working conditions were comparable, which were all smaller than those of the physiological model. Compared with Models B and C, the maximum compressive stress of the right pedicle screw and the interbody fusion cage in Model D was the smallest or between Models B and C under different working conditions. Model D had the largest peak stress of APFS and right pedicle screw during anterior flexion. Conclusions APFS combined with contralateral pedicle screw fixation can be used as a novel fixation method for TLIF surgery of lumbar spine.

Sustained Release of Melatonin from GelMA Liposomes Reduced Osteoblast Apoptosis and Improved Implant Osseointegration in Osteoporosis.

A reduction in bone mass around an implant is the main cause of implant loosening, especially in postmenopausal osteoporosis patients. In osteoporosis, excessive oxidative stress, resulting in osteoblast apoptosis, largely contributes to abnormal bone remodeling. Melatonin (MT) synthesized by the pineal gland promotes osteoblast differentiation and bone formation and has been effectively used to combat oxidative stress. Therefore, we hypothesized that MT attenuates osteoblast apoptosis induced by oxidative stress, promotes osteogenesis in osteoporosis, and improves bone mass around prostheses. Moreover, considering the distribution and metabolism of MT, its systemic administration would require a large amount of MT, increasing the probability of drug side effects, so the local administration of MT is more effective than its systemic administration. In this study, we constructed a composite adhesive hydrogel system (GelMA-DOPA@MT) to bring about sustained MT release in a local area. Additionally, MT-reduced apoptosis caused by hydrogen peroxide- (H2O2-) induced oxidative stress and restored the osteogenic potential of MC3T3-E1 cells. Furthermore, apoptosis in osteoblasts around the implant was significantly attenuated, and increased bone mass around the implant was observed in ovariectomized (OVX) rats treated with this composite system. In conclusion, our results show that GelMA-DOPA@MT can inhibit osteoblast apoptosis caused by oxidative stress, thereby promoting osteogenesis and improving bone quality around a prosthesis. Therefore, this system of local, sustained MT release is a suitable candidate to address implant loosening in patients with osteoporosis.

Biomechanical evaluation of transverse acetabular fracture fixation / 中华创伤骨科杂志

Objective To conduct a biomechanical evaluation of the four internal fixation methods to treat transverse acetabular fracture and find the b est one. Methods The transverse acetabular fracture models were created by osteo tomy in 12 pairs of embalmed cadaveric hip joints, and fixed with one of the fou r different methods: an anterior column plate (P/N), an anterior column plate w ith a posterior column screw (P+S), a posterior column plate with an anterior screw (S+P) and two posterior column plates (N/P?2). The biomechanical stabi lity was evaluated on longitudinal displacement, level displacement and stiffnes s measurements for fixed fracture fragments which were under 800 Newton vertical compression load. Results The longitudinal displacement in S+P was 3.99mm, in P+S 4.09mm, in N/P?2 5.07mm and in P/N 5.66mm; the level displacement in S+P was 0.015mm, in P+S 0.016mm, in N/P?2 0.022mm and in P/N 0.025mm; the average stiffness in S+P was 205.77N/mm, in P+S 207.52N/mm, in N/P?2 162.36N/mm and i n P/N 146.67N/mm. There were significant differences between the groups of S+P and P+S and the groups of N/P?2 and P/N (P