BONE MEASUREMENTS BY PERIPHERAL QUANTITATIVE COMPUTED TOMOGRAPHY (pQCT) IN CHILDREN WITH CEREBRAL PALSY TERESA BINKLEY, MS, J ULIE J OHNSON, MD, LOIS VOGEL, MS, PT, PCS, HEIDI KECSKEMETHY, RD, CSP, RICHARD HENDERSON, MD, PHD, AND BONNY SPECKER,PHD Objective To use peripheral quantitative computed tomography (pQCT) to determine bone measurements in patients with cerebral palsy (CP) age 3 to 20 years and compare them with control subjects. Study design A total of 13 (5 male) patients with CP, along with 2 sex- and age-matched controls for each, were included in a mixed-model analysis with matched pairs as random effects for pQCT bone measurements of the 20% distal tibia. Results Tibia length was similar in the CP and control groups (P = .57). Weight was marginally higher in the control group (P = .06). Cortical bone mineral content (BMC), area, thickness, polar strength-strain index (pSSI), and periosteal and endosteal circumferences were greater in the control group (P < .05 for all). Relationships between bone measurements and weight showed that cortical BMC, area, periosteal circumference, and pSSI were greater at higher weights in the control group (group-by-weight interaction, P < .05 for all). Cortical thickness was greater in the control group and was correlated with weight. Cortical volumetric bone mineral density (vBMD) was greater with higher weights in the CP group (group-by-weight interaction, P = .03). Conclusions Bone strength, as indicated by pSSI, is compromised in children with CP due to smaller and thinner bones, not due to lower cortical bone density. (J Pediatr 2005;147:791-6) F ractures are prevalent in children with cerebral palsy (CP), with the femur the most common site, followed by the tibia. 1 Repeated fractures diminish the quality of life and add to the care requirements of these children. 1,2 CP is increasing in preva- lence, 3,4 and fractures continue to be a challenge for patients and clinicians. Areal bone mineral density (aBMD) measurements by dual-energy X-ray absorpti- ometry (DXA) of the lateral distal femur, developed specifically for use in CP patients, 5,6 as well as standard measurements of the spine and proximal femur by DXA, have been used to assess bone quality. 1,2,7,8 Several studies in CP show a relationship between bone mea- sures and weight-bearing ability. 1,7,8 In a study of 139 children with spastic CP, aBMD z-scores of the proximal femur and spine were lower in nonambulators than in normal ambulators. 7 Another study in children with moderate to severe CP found lower lateral distal femur and spine aBMD z-scores in children with gross motor functional classifica- tion 5 (more motor impairment) than in children with gross motor functional classification 3 (less motor impairment). 1 Weight-bearing physical activity has been shown to increase total proximal bone mineral content (BMC) and femoral neck BMC in children with CP who participated in an 8-month exercise program compared with those who maintained their usual activity. 8 Relationships between bone-loading and bone measures also have been shown in other populations. 9,10 For example, side-to-side differences in periosteal apposition among racquet-sport players show greater increases in the impact-loaded side. 9 Eser et al 10 re- cently reported bone changes in geometry and volumetric bone mineral density (vBMD) aBMD Areal bone mineral density BMC Bone mineral content CP Cerebral palsy DXA Dual-energy X-ray absorptiometry pQCT Peripheral quantitative computed tomography pSSI Polar strength-strain index vBMD Volumetric bone mineral density 791 From the Ethel Austin Martin Human Nutrition Program, South Dakota State University, Brookings, South Dakota; Children’s Care Hospital and School, University of South Dakota School of Medicine, Sioux Falls, South Dakota; Department of Research, A.I. duPont Hospital for Children, Wil- mington, Delaware; and Department of Orthopedics, University of North Carolina, Chapel Hill, North Carolina. Submitted for publication Jan 12, 2005; last revision received Apr 21, 2005; accepted Jul 14, 2005. Reprint requests: Bonny Specker, EAM Bldg. Box 2204, South Dakota State University, Brookings, SD 57007. E-mail: Bonny.Specker@sdstate.edu. 0022-3476/$ - see front matter Copyright ª 2005 Elsevier Inc. All rights reserved. 10.1016/j.jpeds.2005.07.014