Proximal humeral fractures treated with locking plate can fail due to varus collapse, especially in osteoporotic bone with medial cortex comminution. The use of an intramedullary strut together with locking plate fixation may strengthen fixation and provide additional medial support to prevent the varus malalignment. This study biomechanically investigates the influence of an intramedullary cortical bone strut on the cyclic stability of proximal humeral fractures stabilized by locking plate fixation in a cadaver model. Ten cadaveric humeri were divided into two groups statistically matched for bone density. Each specimen was osteotomized with 10 mm gap at the surgical neck. The non-augmented group stabilized with locking plate alone; in the augmented group, a locking plate was used combined with an intramedullary cortical bone strut. The strut was retrograded into the subchondral bone, and three humeral head screws were inserted into the strut to form a plate-screw-strut mechanism. The cyclic axial load was performed to 450 N for 6000 cycles and then loaded to failure. Construct stiffness, cyclic loading behavior and failure strength were analyzed to identify differences between groups. The augmented constructs were significantly stiffer than the non-augmented constructs during cycling. On average, the maximum displacements at 6000 cycles for non-augmented and augmented groups were 3.10 ± 0.75 mm and 1.7 ± 0.65 mm (p = 0.01), respectively. The mean peak-to-peak (inter cycle) displacement at 6000 cycles was about 2 times lower for the augmented group (1.36 ± 0.68 mm vs. 2.86 ± 0.51 mm). All specimens showed varus collapse combined with loss of screw fixation of the humeral head. The failure load of the augmented group was increased by 2.0 (SD = 0.41) times compared with the non-augmented group (p < 0.001). The stability and strength of the locking plate augmented with an intramedullary strut were significantly increased. For bone with poor quality, the subsidence of the locked screws led larger displacement, decreased the stability of the constructs, however, the plate-screw-strut mechanism provided more rigidity to stabilize the fixation. This study emphasized the importance of intramedullary support for the proximal humeral fractures fixed with a locked plate under cyclic loading, especially in bone with poor quality. This work is based on the results of cadaver model, further in vivo analysis is necessary to determine if the clinical results can be extrapolated from this data.

Bone drilling is a common procedure used to create pilot holes for inserting screws to secure implants for fracture fixation. However, this process can increase bone temperature and the excessive heat can lead to cell death and thermal osteonecrosis, potentially causing early fixation failure or complications. We applied a three-dimensional dynamic elastoplastic finite element model to evaluate the propagation and distribution of heat during bone drilling and assess the thermally affected zone (TAZ) that may lead to thermal necrosis. This model investigates the parameters influencing bone temperature during bone drilling, including drill diameter, rotational speed, feed force, and predrilled hole. The results indicate that our FE model is sufficiently accurate in predicting the temperature rise effect during bone drilling. The maximum temperature decreases exponentially with radial distance. When the feed forces are 40 and 60 N, the maximum temperature does not exceed 45 °C. However, with feed forces of 10 and 20 N, both the maximum temperatures exceed 45 °C within a radial distance of 0.2 mm, indicating a high-risk zone for potential thermal osteonecrosis. With the two-stage drilling procedure, where a 2.5 mm pilot hole is predrilled, the maximum temperature can be reduced by 14 °C. This suggests that higher feed force and rotational speed and/or using a two-stage drilling process could mitigate bone temperature elevation and reduce the risk of thermal osteonecrosis during bone drilling.

The unilateral approach for bilateral decompression was developed as an alternative to laminectomy. Unilateral laminotomy has been rated technically considerably more demanding and associated with more perioperative complications than bilateral laminotomy. Several studies have indicated that bilateral laminotomy are associated with a substantial benefit in most outcome parameters and thus constituted a promising treatment alternative. However, no complete kinematic data and relative biomechanical analysis for evaluating spinal instability treated with unilateral and bilateral laminotomy are available. Therefore, the purpose of this study was to compare the stability of various decompression methods. Ten porcine lumbar spines were biomechanically evaluated regarding their strain and range of motion, and the results were compared following unilateral or bilateral laminotomies and laminectomy. The experimental protocol included flexion and extension in the following procedures: intact, unilateral or bilateral laminotomies (L2–L5), and full laminectomy (L2–L5). The spinal segment kinematics was captured using a motion tracking system, and the strain was measured using a strain gauge. No significant differences were observed during flexion and extension between the unilateral and bilateral laminotomies, whereas laminectomy yielded statistically significant findings. Regarding strain, significant differences were observed between the laminectomy and other groups. These results suggest that laminotomy entails higher spinal stability than laminectomy, with no significant differences between bilateral and unilateral laminotomies. The laminectomy group exhibited more instability, including the index of the range of motion and strain. However, bilateral laminotomy seems to have led to stability similar to that of unilateral laminotomy according to our short-term follow-up. In addition, performing bilateral laminotomies is easier for surgeons than adopting a unilateral approach for bilateral decompression. The results provide recommendations for surgeons regarding final decision making. Future studies conducting long-term evaluation are required.

This study concerns the effects of different drilling parameters of pilot drills and twist drills on the temperature rise of alveolar bones during dental implant procedures. The drilling parameters studied here include the feed rate and rotation speed of the drill. The bone temperature distribution was analyzed through experiments and numerical simulations of the drilling process. In this study, a three dimensional (3D) elasto-plastic dynamic finite element model (DFEM) was proposed to investigate the effects of drilling parameters on the bone temperature rise. In addition, the FE model is validated with drilling experiments on artificial human bones and porcine alveolar bones. The results indicate that 3D DFEM can effectively simulate the bone temperature rise during the drilling process. During the drilling process with pilot drills or twist drills, the maximum bone temperature occurred in the region of the cancellous bones close to the cortical bones. The feed rate was one of the important factors affecting the time when the maximum bone temperature occurred. Our results also demonstrate that the elevation of bone temperature was reduced as the feed rate increased and the drill speed decreased, which also effectively reduced the risk region of osteonecrosis. These findings can serve as a reference for dentists in choosing drilling parameters for dental implant surgeries.