Ultrasound for the Early Diagnosis of Tibial Fracture Healing After Static Interlocked Nailing Without Reaming: Histologic Correlation Using a Canine Model

OBJECTIVE: Ultrasound is thought to be clinically useful in evaluating bone formation through its presumed identification of fracture callus. However, documentation of the actual histology of the tissue identified by ultrasound has been lacking. The purpose of this study was to determine the histologic composition of the hyperechoic tissue "seen" by ultrasound. STUDY DESIGN: Unilateral fractures were created in eight canine tibias and then fixed by using locked intramedullary nailing without reaming. The limbs were studied at two, three, four, six, and eight weeks postoperatively with plain radiographs, ultrasound, and ultrasound-directed needle biopsy. RESULTS: The presence of a hyperechoic ultrasound signal was found to have a 100 percent correlation with the presence of hard fracture callus biopsy tissue. In addition, fracture union by ultrasound criteria significantly predated radiographic fracture union (5.6 vs. 7.3 weeks, p = 0.05). CONCLUSIONS: These results support and provide a scientific basis for the clinical use of ultrasound to assess tibial fracture healing following static interlocked nailing without reaming.