STABLE ELASTIC CENTROMEDULARY PINNING FOR PROGRESSIVE LENGTHENING

Abstract

Purpose: The purpose of this study was to evaluate centromedullary pinning for bone lengthening. We studied an animal model to discover the details of bone regeneration and assess the advantages of the technique. We present our early clinical results.

Material and methods: Progressive lengthenings of the tibia by centromedullary pinning were performed in eleven dogs. Distraction began on day 5 and lasted 28 days. Arteriograms were obtained after sacrifice.We also analysed 17 cases of limb lengthening in patients: one arm, two forearms, nine femurs, five tibias. Mean patient age was 14 years. Mean gain in bone length was 6.2 cm.

Results: The experimental work demonstrated that intensive bone regeneration requires faster distraction. Early bone union was observed in four dogs. Bone healing was complete at about 15 days in all dogs. The centromedullary pins were left in place in three dogs after removing the external fixator. There was no secondary deformation. The arteriogram showed that the nourishing artery was not ruptured. In our patients, delay to healing was shorter. The radiograms demonstrated intensive bone regeneration. Endosteal regeneration was significant and was never inhibited. Significant periosteal reaction was observed. The planned gain in length was achieved in all patients. We did not have any complications.

Discussion: Bone lengthening methods using a centromedullary nail provide absolute stability while avoiding external fixation but at the cost of complete destruction of the centromedullary vascular supply. Our animal experiments and clinical experience prove that elastic centromedullary pins do not inhibit endosteal regeneration but, on the contrary, partial destruction of the marrow with intact vascularisation stimulates bone regeneration. For bone lengthenings, centromedullary pinning is the only method of internal fixation allowing optimal conditions for bone regneration.

Conclusion: The progressive distraction of the elastic centromedullary pin during the lengthening period stimulates the regenerative processes. The biological effect of the vascular “displacement” from the centre to the periphery of the bone fragments leads to significant periosteal reaction. Elastic centromedullary pinning adds stability to the bone fragments. Associating the two methods allows removal of the external fixator leaving the centromedullary pins in place. By strengthening the regenerated bone, the pins provide a certain degree of additional stability.