Abstract
Introduction: Open lower leg fractures are frequently associated with severe soft tissue damage. Cortical bone tissue is thus denudated. Osteomyelitis and impaired circulation with loss of bone tissue with subsequent defects are among the main complications, arising from the condition. Surfacing bone is judged on its perfusional conditione solely by the surgeon. Minor bleedings with decortication of the respective cortical bone serve as parameter for the clinical assessment and subsequent therapeutic decisions.
Methods: 80 inbred white New Zealand rabbits with two groups of 40 animals each were employed. Each animal had a tibial fracture induced in a standardized fashion, stabilized by screw osteosynthesis. The fracture area was freed from soft tissue and periost and the medullary space reamed. After 3 or 7 days (group one or two, respectively), the tissue defect was covered by a local fascia-free gastrocnemius muscle flap. In increasing intervalls from one to 16 weeks, the implants were removed and the animals euthanized. At all three interventions, cortical microcirculation was measured by two-channel laser doppler flowmetry (LDF), counting erythrocyte flux as product of erythrocyte velocity with number of erthrocytes observed. Observed were cortical bone of the fragment created and of the adjacent cortical bone with and without periostal linig. The bone was removed after euthanisation and analysed histo-morphologically. All animals were kept in accordance with the procedures outlined in the “Guide for the Care a
Results: A muscle flap after three days led to significantly better perfusion as compared to 7 days with 24 vs 10 flux (mean +/− SEM; p < 0,05, paired t-test; baseline 1,4 flux ), resembling almost healthy values. Simultaneously, flap covering after three days displayed a lower rate of necroses with 23 vs. 40 % (p < 0,05, paired t-test). Incidence of osteomyelitis was as well higher in the 7-days-group (24%). Improved microcirculation as well as lower rate of infection were associated with the induction of neoperiost from the muscle flap.
Discussion: Delayed plastic covering of open lower leg fractures led to delayed healing as well as infection in our experimental setting. Two-channel doppler was a reliable and little invasive means for the objective evaluation of conditions, associated with experimental open fractures. Identification of less vital tissue could lead to reduction in the loss of vital bone tissue in clinical settings without the hazard of active decortication. Again, a vital periost has been proved to be the one central aspect of bone healing.
The abstracts were prepared by Professor Jegan Krishnan. Correspondence should be addressed to him at the Flinders Medical Centre, Bedford Park 5047, Australia.
