Fractures of the adult tibial shaft are common and often result in considerable morbidity because a significant number exibit slow healing. The reasons for this are not known and, therefore, prevention is not possible. This has been investigated using clinical and experimental methods. One hundred closed adult tibial shaft fractures treated by closed methods were studied to determine the true delayed union rate and the clinical factors that may be of importance. In addition, an attempt was made to predict fractures at risk using serial biochemical measurements and scintigraphic examination using technecium 99m methylene diphosphonate. The patterns of soft tissue damage in tibial shaft fractures were investigated experimentally in rabbits. Healing of a simple osteotomy was studied after the exclusion of periosteum, medullary or both tissues respectively from the fracture site. Cortical arterial perfusion was studied after the Isolation of periosteal, nutrient and epiphyseo-metaphyseal circulations respectively using a diaphyseal segment model and barium sulphate perfusion techniques. The delayed union rate was 19% at 20 weeks and 15 more fractures united at 30 weeks with continued conservative treatment. Of the clinical factors investigated, only the severity of trauma appeared to play a part in delayed union. Serum creatinine phosphokinase levels rose after fracture and provided some indication of severity of trauma. Serum calcium and inorganic phosphate levels rose after fracture and then progressively fell over a 20 week period. Serum levels of osteocalcin and somatomedins did not fluctuate. Biochemical parameters were not useful in identifying fractures at risk of developing delayed union. Of all scintigraphic methods, only the A/C ratio of uptake over the fracture site relative to an adjacent site, with a cut off value of 2.0, clearly separated normal from delayed union. Simple osteotomies of the rabbit tibial diaphysis healed normally in the absence of medullary tissues but not in the absence of periosteum. Cortical arterial perfusion was observed in diaphyseal segments of the rabbit tibial diaphysis up to 2 weeks but not thereafter when entrusted to the nutrient circulation alone. When entrusted to the periosteal circulation alone, cortical perfusion could be observed immediately after death, but not thereafter until 2 weeks after the procedure had been performed.
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