COPYRIGHT © 2006 BY THE JOURNAL OF BONE AND JOINT SURGERY, INCORPORATED 55 Predicting Fracture Through Benign Skeletal Lesions with Quantitative Computed Tomography BY BRIAN D. SNYDER, MD, PHD, DIANA A. HAUSER-KARA, PHD, JOHN A. HIPP, PHD, DAVID ZURAKOWSKI, PHD, ANDREW C. HECHT, MD, AND MARK C. GEBHARDT, MD Investigation performed at Children’s Hospital and the Orthopaedic Biomechanics Laboratory, Beth Israel Deaconess Medical Center, Boston, Massachusetts Background: There are no proven radiographic guidelines for predicting fracture risk in children and young adults with a benign skeletal lesion. An in vivo diagnostic study was conducted to determine whether a reduction in the load- carrying capacity of a bone measured with quantitative computed tomography was more accurate than current radio- graphic guidelines for predicting pathologic fracture in patients with a benign skeletal lesion. Methods: Eighteen patients who presented with a fracture through a benign skeletal lesion were compared with eighteen patients who had a benign skeletal lesion that had been thought to be at increased risk for fracture on the basis of currently used radiographic criteria but had not fractured over a two-year period. Structural analysis was performed to calculate the resistance of the affected bones to compressive, bending, and torsional loads with use of serial transaxial quantitative computed tomography data obtained along the length of the bone containing the lesion and from homologous cross sections through the contralateral, normal bone. At each cross section, the ratio of the structural rigidity of the affected bone divided by that of the normal, contralateral bone was deter- mined. The cross section with the greatest reduction in compressive, bending, and torsional rigidity was identified as that most likely to fracture. Results: The mean age (and standard deviation) of the thirty-six patients was 12.5 ± 3.6 years. Twenty lesions were located in the femur; eleven, in the tibia; three, in the humerus; one, in the ulna; and one, in the pelvis. A combina- tion of the minimum bending and torsional rigidities calculated from the tomographic data provided optimal perfor- mance in differentiating between the fracture and non-fracture groups (100% sensitivity and 94% specificity). In contrast, plain radiographic criteria demonstrated 28% to 83% sensitivity and 6% to 78% specificity. Conclusions: The combination of bending and torsional rigidity measured noninvasively with quantitative computed tomography was more accurate (97%) for predicting pathologic fracture through benign bone lesions in children than were standard radiographic criteria (42% to 61% accuracy). We believe that this method can provide accurate objec- tive criteria for planning treatment of benign bone lesions and monitoring treatment response. Level of Evidence: Therapeutic Level III . See Instructions to Authors for a complete description of levels of evidence. enign skeletal neoplasms represent a diverse group of pathologic and clinical entities that vary greatly in ag- gressiveness and clinical behavior 1,2 . The true incidence is unknown, but benign fibrous lesions such as nonossifying fibromas and fibrous cortical defects have been found in up to 33% of asymptomatic children who were evaluated with ra- diographs of long bones for reasons other than surveillance of a lesion 3,4 . After confirming that the lesion is benign, the or- thopaedist must decide whether the defect has weakened the bone sufficiently to cause a pathologic fracture and whether treatment is indicated. Pathologic fractures in the axial and appendicular skeleton are often associated with pain and loss of function 5 , so preventing these fractures is a primary goal of treatment. Optimal treatment for benign bone lesions re- B A commentary is available with the electronic versions of this article, on our web site (www.jbjs.org) and on our quarterly CD-ROM (call our subscription department, at 781-449-9780, to order the CD-ROM).