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 and subsequent defects are among the main complications. Necrosis vs. revascularisation are supposed to be reflected by local tissue contents of high energy phosphates.

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. Cortical bone of the fragment created and of the adjacent cortical bone with and without periostal linig was analysed. The bone was removed after euthanisation and analysed histomorphologically. Simultaneously, fragments were deep frozen in liquid nitrogen at −190°C, a two by one centimeter fragment from the unaffected contralateral tibia harvested as control. Analysis of high energy phosphates (ATP) was performed by high pressure liquid chromatography as described by NEES (HPLC). All animals were kept i

Results: The average ATP contents in healthy cortical bone was 0,092 +/− 0,009 nmol/mg dry weight. A muscle flap after three days led to significantly higher concentrations as compared to 7 days with 0,081 +/− 0,011 vs 0,03 +/− 0,008 nml/mg dry weight (mean +/− SEM; p < 0,05, paired t-test), the latter resembling sequestration. 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%).

Discussion: Delayed plastic covering of open lower leg fractures led to decreased ATP levels, delayed healing and infection in our experimental setting. For the first time, we could determine the contents of ATP by HPLC in cortical bone. Increase in ATP contents reflected the biological quality of the bone investigated, ranging from reconstituted healthy bone to sequesters.