Sun Joo Lee MD, Presenter: Nothing to Disclose

Qian Dong MD, Abstract Co-Author: Nothing to Disclose

Jenny Zhao, Abstract Co-Author: Nothing to Disclose

Sung Moon Kim MD, Abstract Co-Author: Nothing to Disclose

Jon A. Jacobson MD, Abstract Co-Author: Consultant, BioClinica, Inc Royalties, Reed Elsevier Grant, Harvest Technologies Corporation

Yebin Jiang MD, PhD, Abstract Co-Author: Research grant, General Electric Company

Investigation of muscle and bone interaction is of considerable research interest. The largest loads applied to bones during daily activities come from the muscles. We investigated the relationships between muscle and bone and used an in vitro fracture model to identify how bone and muscle predicted fracture load.

Cross-sectional area (CA) of cortical bone and muscles, cross-sectional moments of inertia (CSMIs) of the cortical bone were determined from MR images of 20 fresh human cadaveric forearms that were also evaluated using a peripheral quantitative CT (pQCT) scanner at 15% of the length of the forearm. The specimens were randomly assigned to different loading patterns with wrist either in a neutral position or extended/dorsiflexion 45˚ adjusted between the axes of the radius and the third metacarpal confirmed on radiographs. The load to fracture was applied at a displacement rate of 75 mm/second, mimicking an impact from a fall.  

There was no significant difference in the maximum load between dorsiflexion (2388±1685 N) and neutral position (2782±1104 N). The pressure sensitive films showed focal pressure concentration in the center of the radiocarpal joint in neutral upright loading configuration, and in an equally distributed pressure pattern across the radiocarpal joint in extended-wrist situation. Correlations (r2) were 0.61 (p<0.0001) between MRI muscle CA and cortical bone CA, and 0.52 (p<0.0001) between MRI muscle CA and pQCT BMC at the 15% site. Correlations (r2) between MRI and pQCT at the 15% site were 0.89 and 0.90 (p<0.0001) for polar CSMI and CA, respectively. The fracture load could be predicted by MRI cortical CA, MRI muscle CA, and pQCT cortical BMC at the 15% site with r2 of 0.85, 0.57, and 0.84 (p<0.0001), respectively. Similar strong correlations with the fracture load were found after adjustment for bone size.

The muscle and bone are significantly associated. The properties of cortical bone and the muscle in the distal radius contribute significantly to its biomechanical competence and predict strength and risk of forearm fractures. Rather than directly influencing fracture load, the different loading configurations influenced the load transfer pattern from the carpal bones into the radius.

Osteoporotic fracture is associated with muscle and bone interactions.

Lee, S, Dong, Q, Zhao, J, Kim, S, Jacobson, J, Jiang, Y, Muscle and Cortical Bone Predict Distal Radius Fracture Load.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11034435.html