Jacobs Rr

Effect of Plates on Cortical Bone Perfusion

Using disulphine blue, sheep tibial cortex perfusion was decreased by subperiosteal stripping but not by extraperiosteal exposure. Semitubular plates applied with either low (20 kp) force, sufficient for extraosseous vascular occlusion, or high (200 kp) force, similar to that used clinically, both produced significant ischemia beneath the plate. In contrast, the dynamic compression plate produced significantly greater ischemia only with the higher force.

A study of external skeletal fixation systems for unstable pelvic fractures

This study was undertaken to determine the feasibility of constructing an anterior pelvic external fixator capable of resisting displacement of vertical shear fractures. Newly designed tapered thread pins for cancellous bone had better bone pin fixation and their greater 6-mm diameter provided more than twice the stiffness of Hoffmann 4-mm pins when tested in clusters. Using these pins and a more rigid anterior frame as one model, various pelvic fixators were tested to determine their resistance to vertical shear forces. These tests determined that this new fixator was 16 times stiffer than a Bonnel single anterior frame and five times stiffer than a double anterior frame (both constructed of Hoffmann components). Extrapolation from the data shows that 13 mm of posterior fracture displacement would occur with loads of one half body weight using the new fixator. Additionally it was noted that Hoffmann frames constructed with two 5-mm pins performed as well as those using three 4-mm pins.