DIFFERENT HEALING PATTERNS OF EXPERIMENTAL OSTEOTOMIES TREATED BY INTRAMEDULLARY NAILING

The healing of 52 diaphyseal osteotomies in rabbit tibiae was followed up histologically from 3 to 24 weeks after rigid intramedullary naili ng. The histological evaluation was made from longitudinal sections th rough the osteotomy area. Particular attention was paid to the fractur e healing pattern. A bulky periosteal response was visible in every sp ecimen. At 24 weeks, the external callus was always well remodeled. Th e osteotomy line rapidly filled with bone from 6 weeks onwards. At 24 weeks. the site of osteotomy was detectable only on the basis of sligh t irregularity in the cortex. The secondary gap healing seen in 19 spe cimens was the most common type of bone union from 6 weeks onwards. In 13 specimens, the exact type of osteonal healing was not definable, s ince a solid union with good cortical reconstruction was always the fi nal outcome. Altogether, four nonunions were detected throughout the s tudy, none of these, however, in the specimens at 24 weeks. Considerab le endosteal resorption was detected at 24 weeks, at which time at lea st one third of the original cortex had dissappeared in all specimens. The rigid nail seems to ensure a relatively uneventful healing of the experimental osteotomies. Vast endosteal resorption and some nonunion s make the use of medullary reaming in this connection doubtful.