Ultrasonometric evaluation of bone healing: Experimental study using a model of diaphyseal transverse osteotomy of sheep tibiae.

Noninvasive ionizing-radiation-free methods of evaluation, such as ultrasonometry, are desirable in any medical situation. An in vitro ultrasonometric study was undertaken to evaluate the bone healing process of sheep tibiae submitted to a diaphyseal transverse osteotomy at different times after the procedure. Fifteen sheep weighing an average of 37 kg had surgery for a transverse mid-diaphyseal osteotomy of the right tibia; they were divided postoperatively into three groups of five for periods of observation at 30, 45 and 60 days. The intact left tibiae of the 15 animals were used for control. The healing process was monitored with conventional radiographs taken at two-week intervals, and the animals were killed at the end of the period of observation of each group. Both surgical and intact tibiae were removed, their diameters were measured and they were submitted to measurement of underwater ultrasound propagation velocities (USPV) at the osteotomy sites in both the sagittal and frontal planes. The diameters of the surgical tibiae decreased with time in both planes (from 26.9 mm to 22.0 mm and to 20.9 mm in the sagittal plane, and from 29.3 mm to 23.9 mm and to 23 mm in the frontal plane), with significant differences between the periods of observation (p < or = 0.018 and p < or = 0.003 between 30 and 45 days and 30 and 60 days, respectively, for the sagittal plane and p < or = 0.006 and p < or = 0.003 between 30 and 45 days and 30 and 60 days, respectively, for the frontal plane) and between surgical and intact tibiae at all time points (p < or = 0.0005 for each comparison). USPV increased with time from 2290 m/s to 2399 m/s and to 2382 m/s in the sagittal plane, and from 2376 m/s to 2472 m/s and to 2466 m/s in the frontal plane, accounting for an approximate 5% difference between 30 and 60 days Differences between the surgical and intact tibiae were significant at all time points (p < or = 0.0005 for both sagittal and frontal planes) but not between periods for either plane. There was a strong negative correlation between diameter and USPV (Pearson's correlation coefficient of -0.8998 for the sagittal plane and -0.9192 for the frontal plane). It was concluded that ultrasonometric evaluation of the bone healing process is feasible, yielding precise and reliable results, with a potential for clinical application.