Quantification of Fracture Healing from Radiographs Using the Maximum Callus Index

Callus formation and growth are an essential part of secondary fracture healing. Callus growth can be observed radiographically and measured using the "Callus Index," which is defined as the maximum diameter of the callus divided by the diameter of the bone. We compared three groups of patients with tibial fractures treated by external fixation, intramedullary nailing, and casting to assess the validity of using serial measurements of callus index as a measure of fracture healing. When callus index was plotted against time for each patient, the point at which the fracture began to remodel, indicated by the highest point of the curve, was observed as a consistent feature regardless of fixation method. This occurred on average at 2A1/2 weeks after plaster cast removal (14 weeks post injury), 5 weeks after external fixator removal (22 weeks post injury), and 27 weeks post injury for the intramedullary nailed fractures. Because remodeling only occurs once the fracture is stable, a peak in callus index is a reliable sign that the fracture has united. Serial measurements of callus index would therefore appear to offer a simple method of quantifying secondary fracture healing regardless of the treatment method used. Level of Evidence: Level III, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.