Accuracy of corrective osteotomies in fibular malunion: a cadaver model.

BACKGROUND: While incorrect length of a fibular fracture reduction can be measured by plain radiographs, accurate imaging of rotational deformities requires computed tomography (CT). Operative correction of fibular malrotation has not been accurately measured. The aim of this study was to evaluate the accuracy of operative correction of fibular malrotation. MATERIALS AND METHODS: Six pairs of formalin-fixed, lower leg cadaver specimens had shortening with additional internal or external rotation induced by segmental fibular resection and plate fixation. The deformity was measured by CT. Two experienced surgeons performed standardized corrective operations on six specimens each. The postoperative results were measured by CT. RESULTS: The mean overall accuracy for correction of malrotation was 1.58 degrees (SD = 0.8 degrees). There were no significant differences between the two surgeons performing the corrections. CONCLUSION: The accuracy of operative correction of malrotation in this cadaver model is in accordance with the requirements reported in clinical studies. CLINICAL RELEVANCE: Considering the error margin for CT analysis, correction within 5 to 10 degrees seems practical.

Fifth metatarsal avulsion fracture: a rational basis for postoperative treatment.

BACKGROUND: Lacking rational basis for the postoperative treatment of fifth metatarsal avulsion fractures. METHODS: Biomechanical test of stability of tension banding and screw fixation of fifth metatarsal avulsion fractures in cadaver specimen, sonographic measuring of the maximum cross-section of the peroneus brevis muscle, electromyographic examinations of the activity of the peroneus brevis muscle at different loads and means of immobilization. RESULTS: The forces acting on the base of the fifth metatarsal bone during voluntary activation of the peroneus brevis muscle or activation in the gait cycle are of the same magnitude as the failure forces of internal fixation. Immobilization of the talocrural joint achieves no reduction in muscle activation. Partial weight bearing reduces muscle activation. CONCLUSIONS: The postoperative treatment after osteosynthesis of fifth metatarsal avulsion fractures should be partial weight bearing. For safety reasons we add an elastic ankle orthesis to prevent supination. A below-knee cast is not necessary.

Fracture models in the lumbar sheep spine: a biomechanical investigation.

The purpose of this study was to find out if a limited resection of the cranial vertebral body leaving the posterior wall intact is a sufficient model for AO type 3 fractures, or if additional resection of the posterior wall is necessary. In six, fresh-frozen, lumbar sheep spine specimens, the segmental stability was tested in three motion planes in a spine tester. First, the intact specimens were tested. Then, partial resection of the intervertebral disc L3/4 and resection of the cranial vertebral body of L4 was performed, leaving the posterior wall intact. This defect was tested without instrumentation and with a ventral monosegmental interlocking plate mounted. Then, the defect was extended to a total cranial resection, including the posterior wall, and the tests were subsequently repeated. The stability of both types of defects under the different conditions was compared. Without instrumentation, the total cranial resection showed significantly more ROM in flexion/extension and axial rotation than partial cranial resection. With the ventral interlocking plate mounted, the instability in total cranial resection was significantly higher in flexion/extension, with the relative relation even being increased. In axial rotation and lateral bending, the differences were equalized by the mounted plate. From a biomechanical point of view, total cranial resection including the posterior wall should be preferred as a sheep spine fracture model for AO type 3 fractures.