"Asymmetric scalloping of the regenerate": a radiological sign of pseudoaneurysm in distraction osteogenesis.

Pseudoaneurysm formation is an uncommon but well-recognised and important complication in limb reconstruction surgery. Postoperative diagnosis is usually clinical or an incidental finding. We present an 11-year-old girl, who underwent two-stage limb lengthening with a circular fixator, for a previously treated pseudoarthrosis of the tibia. During the lengthening plan, a concave defect was noted on one side of the regenerate, which was found to be due to extrinsic compression by a pseudoaneurysm. Normal regenerate formation was seen after selective embolisation of the pseudoaneurysm. This concave appearance on one side of the regenerate has previously been described secondary to a difference in stability on the two sides of the osteotomy, when a monolateral fixator is used, but not due to extrinsic compression by a pseudoaneurysm. The authors propose that this radiographic appearance of "asymmetrical scalloping" on one side of the regenerate may represent a radiological sign of a pseudoaneurysm formation and should provoke investigation for the same.