Calcaneal fracture after cortical bone removal.

Four patients developed calcaneal fractures while walking, soon after bone removal from the undersurface of the calcaneus. Heel spur or osteomyelitic bone removal can lead to this complication.

Ingrowth and formation of bone in defects in an uncemented fiber-metal total hip-replacement model in dogs.

An osseous defect was created in the acetabulum and femur of twenty dogs, and then a fiber-metal total hip prosthesis was inserted. A comparison was made between the effects of leaving the defects unfilled, filling the defects with an autogenous bone graft, and filling them with a 50:50 mixture of autogenous bone graft and a biphasic ceramic composed of hydroxyapatite and tricalcium phosphate. The characteristics of formation of bone within the sites of the defects and the extent of the ingrowth of bone into the underlying porous surface were analyzed. At six and twelve weeks after implantation, the dogs in the control group (unfilled defects) had the least amount of bone in the sites of the defects. In the dogs that had had an autogenous bone graft and those in which the defects had been filled with a mixture of autogenous bone graft and biphasic ceramic, there were excellent osteoconductive properties in the filling of the sites of the defects with new bone. A comparison was made between the amount of bone that formed in the osseous defects and the amount that formed in the spaces of the porous-surfaced fiber-metal components of the prostheses, directly underlying and adjacent to the defects. At six weeks, the greatest amount of ingrowth of bone into the spaces of the underlying titanium fiber-metal acetabular components was seen in the control group (22 per cent of the porous surface), followed by the group in which the defects had been filled with a mixture of autogenous bone graft and biphasic ceramic (19 per cent). The defects that had been filled only with autogenous bone graft had poor ingrowth of bone into the porous surface (4 per cent) and predominantly fibrous ingrowth. At twelve weeks, these defects again showed the least amount of ingrowth of bone (15 per cent) compared with the defects in the control group (24 per cent) and those that had been filled with a mixture of autogenous bone graft and biphasic ceramic (24 per cent). No statistically significant differences were found in the amount of ingrowth of bone into the defects that had been created in the femur in the three groups of dogs at either six or twelve weeks. However, the trends appeared to correlate with the data for the acetabular defects.

Posterior cervical fusions using cerclage wires, methylmethacrylate cement and autogenous bone graft. An experimental study of a canine model.

UNLABELLED: Forty-eight adult mongrel dogs underwent posterior exposure of C4-C5, fixation of the two posterior spinous processes together with a no. 20-gauge cerclage wire, posterior element decortication, wound irrigation and the following: bone fusions (application of a standard volume of iliac crest autograft), polymethylmethacrylate (PMMA) fusions (application of a standard volume of methylmethacrylate cement), Combination 1 fusions (application of one-half the volume of graft used in the bone fusions, over the facet joints. Methylmethacrylate cement was pressed into position centrally to surround the posterior spinous processes and cerclage wire), Combination 2 fusions (application of the same volume of graft used in the bone fusions, over the facet joints. Methylmethacrylate cement was applied as in the Combination 1 fusions). For each preparation, six animals survived 2 weeks or 3 months. All had monthly lateral cervical radiographs. At the appropriate times, they were killed and their C4-C5 segments excised and studied mechanically and histologically. At 2 weeks all of the above preparations were mechanically inferior to normal C4-C5 segments in respect to at least one of the parameters studied. At 3 months, the bone fusions and both combination fusions had developed sufficient mechanical stability so that they were equivalent to normal segments. At this time, the PMMA fusions remained inferior to the "normals." The mechanical data for the PMMA and both combination fusions was corroborated by the histology which demonstrated a fibrosynovial layer between the cement masses and underlying posterior element bone. In the 3-month combination fusions, the lateral aspects of the posterior elements had been spanned by a fusion mass. CLINICAL RELEVANCE: Previously, the authors defined some of the problems associated with constructs modeled by their PMMA fusions. This work confirms the previous research. It also demonstrates that ultimate spinal stability is produced by combination constructs. Because of the 2-week mechanical data, it is recommended that when combination constructs are used clinically, the patient's neck be protected by an external orthosis in the early postoperative period.

Carotenoid compound crocetin improves cerebral oxygenation in hemorrhaged rats.

The carotenoid compound crocetin has been shown to increase oxygen diffusivity in vitro. In the present study the effect of crocetin on tissue oxygenation was examined in the cerebral cortex of rats subjected to hemorrhage. Twelve male Sprague-Dawley rats were anesthetized with pentobarbital and ventilation was controlled (PaCO2 = 33 mm Hg). A craniotomy was performed and the animals were hemorrhaged (20% of estimated total blood volume). Six of 12 animals then received a bolus of crocetin (2 U in 0.1 ml saline); the remaining animals received saline (0.1 ml i.v.) only. Values for mean arterial pressure. PO2, PCO2, pH, and hematocrit did not differ in rats that received either saline or crocetin. Tissue oxygen tension (PtO2) was measured at approximately 170 locations in the parietal cerebral cortex of each rat by a platinum-oxygen microelectrode technique. Results were compared by PtO2 frequency histograms. Crocetin as compared with saline treatment resulted in a right shift of the PtO2 frequency distribution and a significant decrease in the frequency of occurrence of low PtO2 values. The average of individual median PtO2 values was significantly greater in crocetin-treated animals as compared with those receiving saline (7.6 +/- 1.7 vs. 3.2 +/- 1.2 mm Hg, respectively). The results suggest that the carotenoid compound crocetin improves tissue oxygenation in the cerebral cortex of hemorrhaged rats.