Outcome after foot and ankle deformity correction using circular external fixation.

BACKGROUND: External fixation is the method of choice for correction of chronic severe foot and ankle deformities. We report our experience and outcomes of circular external fixation. METHODS: Fifty-five patients (60 feet) were treated with circular external fixation. The mean age at surgery was 36 (range 16 to 65) years. The mean followup was 4.4 (range 1 to 10) years. The mean time spent in external fixation was 2.1 (range 1 to 12) months. RESULTS: There were six excellent, 35 good, eight fair, and six poor results, five of which had below knee amputations. All the patients who had an amputation were treated for infected nonunion of the ankle. CONCLUSION: Circular external fixation was found to be an effective method for treating a variety of complex foot and ankle problems. The complications were more common in patients with infected nonunions.

Primary resective shortening followed by distraction osteogenesis for limb reconstruction: a comparison with simple lengthening.

Resective distraction osteogenesis is a new approach to treat segmental diaphyseal bone defects by primary limb shortening and secondary distraction osteogenesis from the same site. A rabbit model was introduced to compare the bone-regeneration characteristics of this technique with those of simple lengthening procedures. Twenty-four skeletally mature New Zealand White rabbits were divided into two equal groups. In the test group, limbs were lengthened after a 10-mm segmental diaphyseal bone resection and limb shortening. In the control group, a simple subperiosteal osteotomy for limb lengthening was performed without resection. New bone formation was evaluated mechanically, radiologically, histomorphometrically, and densitometrically. Bone bridging occurred in all animals. Normalized mechanical values for the newly reconstructed tibiae demonstrated similar torsional stiffness (71+/-3.3 compared with 71+/-8.2%; p = 0.95) and strength (64+/-5.3 compared with 68+/-7.3%; p = 0.66) in the two groups. The average normalized callus diameter was significantly greater in the test group than in the control group (p < 0.01). The remodeling index calculated from densitometry, however, showed a significantly less progressed stage of remodeling in the test group (p < 0.05). Histomorphometric analysis of the callus center supported this finding, showing significantly lower values for trabecular thickness (p < 0.05) and total bone volume (p < 0.01) in the test group. The results demonstrated the possibility of new bone formation after resection and monofocal shortening. This suggests a new therapeutic option to treat diaphyseal segmental bone defects.

Distraction osteogenesis after acute limb-shortening for segmental tibial defects. Comparison of a monofocal and a bifocal technique in rabbits.

BACKGROUND: Segmental bone defects can be treated with immediate limb-shortening followed by monofocal or bifocal distraction osteogenesis. In the present study, the efficacy of monofocal distraction osteogenesis was compared with that of bifocal distraction osteogenesis in a rabbit model. METHODS: Twenty-four skeletally mature New Zealand White rabbits were divided into two equal groups: one group had monofocal distraction osteosynthesis, and the other had bifocal distraction osteosynthesis. In both groups, a one-centimeter-long segment of bone was resected from the midpart of the tibial shaft. In the monofocal reconstruction group, the limb was immediately shortened to close the segmental defect and the defect was allowed to heal for ten days. Lengthening was then begun at this site, with use of a specially designed external fixator, at a rate of 0.5 millimeter per twelve hours. In the bifocal reconstruction group, the segmental defect was closed immediately and the fragments were fixed with microplates. A subperiosteal osteotomy was performed proximal to the tibiofibular junction, and lengthening was performed at the site of the osteotomy. The animals in both groups were killed twenty days after the lengthening was completed. New-bone formation then was evaluated with use of radiographs, densitometry, biomechanical testing, and histological and histomorphometric analysis. RESULTS: Osseous consolidation occurred in all but one of the animals. Biomechanical testing demonstrated that the tibiae that had been treated with use of the simple monofocal reconstruction technique tended to have greater torsional stiffness (p = 0.14) and strength (p = 0.09). Follow-up radiographs revealed that both groups had a significant decrease in radiolucent area (p < 0.05), which occurred at essentially the same rate after lengthening. No significant differences were found between the groups with respect to new-bone mineral density, new-bone area, or the amount of callus. Thus, after resection of a diaphyseal bone segment comprising 10 percent of the original length of the tibia and acute shortening, limb reconstruction was completed successfully through distraction osteogenesis with use of either a monofocal or a bifocal technique in rabbits. CONCLUSIONS: In the present study, both monofocal and bifocal techniques of shortening and distraction osteogenesis were effective for the reconstruction of segmental bone defects. Under some conditions, the monofocal method may provide a simpler means of treating such defects. CLINICAL RELEVANCE: Damage to the soft-tissue envelope as well as venous and lymphatic stasis impose limits on the amount of limb-shortening that can be achieved with use of the monofocal method and also influence the indications for this procedure in the clinical setting.

Comparison of two systems for tibial external fixation in rabbits.

BACKGROUND AND PURPOSE: Use of rabbits in orthopedic investigations is common. In this study, focus is on factors that influence bone healing and on distraction osteogenesis. Biomechanical characteristics of two external fixator systems (Orthofix device and Hoffmann device) for long bones were tested. METHODS: Twelve freshly dissected tibiae were obtained from six skeletally mature New Zealand White rabbits, and four-point bending stiffness in two planes (90 and 180 degrees to the fixator pins) and torsional stiffness and strength of the bone-fixator complex were evaluated by use of a material testing machine. RESULTS: In four-point bending, Orthofix device had higher stiffness and strength, compared with Hoffmann device. When the load was applied 180 degrees to the pins, both devices had higher stiffness, compared with that at 90 degrees. In torsional testing, Orthofix device had significantly higher stiffness and strength. CONCLUSIONS: Significant differences in structural properties between the two systems were evident. Loading direction and gap conditions were important factors in determining properties of the systems. Therefore, type of external fixation system and fixation technique should be considered when designing experiments, using the rabbit long bone model.

Recognition and treatment of osteosarcoma in the military health care system.

Forty-two patients with high-grade intramedullary osteosarcoma treated at Walter Reed Army Medical Center between 1985 and 1995 were reviewed to determine what effects military "managed health care" had on diagnosis, treatment, and outcome. Five-year survival was 61% overall (SE +/- 9.9%), despite local disease control obtained in 95% of patients. There was a statistically significant difference between active duty members and dependents in time to diagnosis (p = 0.008), yet there was no significant difference in survival between the two groups. Five-year survival in our patient population was slightly lower than 5-year survival reported in some large civilian medical centers despite good local disease control and intensive multiagent chemotherapy. Delays in diagnosis and military status had no apparent effect on survival, although limb salvage was not possible in nearly 40% of patients because of tumor size, disease extent, and involvement of neurovascular structures.