Sat., 10/10/09 Basic Sci./Injury Prevent./Spine, Paper #66, 10:27 am OTA-2009
Δ Power Doppler Ultrasound Allows for Real Time Blood Flow Analysis of Tibial Fracture Callus in Patients
Adam F. Rana, MD (n); Alda Cossi, MD (n); June F. Cheng, MD (n);
Elizabeth Krall Kaye, PhD (n); Paul Tornetta, III, MD (3,5A, 7-Smith &Nephew; 8-Exploramed);
Boston University Medical Center, Boston, Massachusetts, USA
Purpose: The biology of fracture healing is dependent on blood flow. The blood flow after intramedullary nailing has been examined in animals, but has never been characterized in patients. Knowledge about the timing of blood flow to the fracture may allow earlier prediction of healing abnormalities, and open the door to new treatment options. Power Doppler ultrasound (PDU) has been successfully used to evaluate microflow in other areas, but has not been applied to human fracture healing. The hypothesis of this OTA-funded pilot study is that a pattern of fracture healing can be modeled with the use of color and PDU. Specifically, we aimed to describe the timing of blood flow changes in early fracture healing. As a secondary outcome, we attempted to look for any correlation of blood flow with early callus formation.
Methods: Patients with open or closed tibial shaft fractures treated with reamed intramedullary nails were offered entry into this IRB-approved prospective protocol. The protocol included PDU examinations and standardized AP and lateral radiographs at 2, 4, 6, 8, and 12 weeks after intramedullary nail placement. All PDU examinations were performed by a single examiner using a Philips iU22 ultrasound scanner. PDU studies were performed in the sagittal and axial planes over a minimum 120° arc centered over the anterior aspect of the tibia. The color area within the fracture was quantified using Image J, a public domain image-processing program developed at the National Institutes of Health and designed for color pixel quantification. A region of interest (ROI) was identified in both the axial and sagittal plane to include maximum color signal within the fracture site. This ROI and total number of pixels within the ROI was kept constant per patient throughout the study to allow for longitudinal comparison of data. Radiographic evaluation was done using the RUST (Radiographic Union Scale for Tibial Fractures) method, which scores the callus at each of the 4 cortices seen on the AP and lateral radiographs from 0 to 3, allowing a total of 0 to 12. Pearson correlation coefficients were used to evaluate associations between ultrasound values and the corresponding healing scores at each time point, as well as associations between ultrasound values at 2 weeks or 4 weeks and subsequent healing scores. Data analyses were performed with SAS (version 9).
Results: 18 patients (11 male and 7 female; average age 40 years [range, 18-61]) with 11 open and 7 closed fractures were enrolled. Three patients had true segmental fractures; in these cases, both fractures were evaluated separately, bringing the number of fractures to 21. Blood flow, based on the PDU scoring, peaked at 8 weeks after nailing, with values of 43.1 at 2 weeks, 144.1 at 4 weeks, 156.0 at 6 weeks, 274.6 at 8 weeks, and 172.1 at 12 weeks:
Radiographic healing scores continually rose through the 12-week period: 0.1 at 2 weeks, 1.9 at 4 weeks, 3.1 at 6 weeks, 4.2 at 8 weeks, and 6.8 at 12 weeks. No ultrasound healing scores correlated significantly with RUST healing scores, but a positive correlation coefficient of 0.5 approached statistical significance (P = 0.085) when comparing ultrasound flow at 4 weeks and RUST score at 12 weeks.
Conclusions: This is the first study to characterize the timing of blood flow changes to the fracture callus in humans after intramedullary nailing of tibial shaft fractures. The blood flow to the fracture site increases for the first 8 weeks, then diminishes at some point between 8 and 12 weeks. In this pilot study, there was a correlation between blood flow at 4 weeks and radiographic callus formation at 12 weeks. In conclusion, the findings in this pilot study demonstrated that PDU may have a role in the evaluation or even prediction of union in tibia fractures, and warrants further investigation.
• The FDA has not cleared this drug and/or medical device for the use described in this presentation (i.e., the drug or medical device is being discussed for an “off label” use). ◆FDA information not available at time of printing. Δ OTA Grant