Tubular anomalous bones found in both thighs of a long-tailed macaque (Macaca fascicularis)

Tubular anomalous bones were found in both thighs of a 6-year-old male long-tailed macaque ( Macaca fascicularis ) bred in captivity. The bones had jagged ends and protruded from the skin. Radiographs showed that they developed in the femurs at the middle and elongated. They were removed with surgery under anesthesia. Histological analysis revealed that these bones had the same histological structure as the femur, though they were composed of primary and secondary osteon regions. This finding indicated that the new bones developed from the old bone piece(s), acquired a tubular shape, and elongated. It is suggested that the anomalous bones were produced not by the congenital deformity but by regeneration from fragments of the fractured femur that were embedded in the bone marrow; these acquired a tubular pattern and elongated.