Texture analysis of X-ray radiographs is a more reliable descriptor of bone loss than mineral content in a rat model of localized disuse induced by the Clostridium botulinum toxin

Botulism is a generalized paralyzing disease caused by the toxin of Clostri dium botulinum (BTX), The toxin acts 3-4 days after injection by blocking t he release of acetylcholine to the muscle, Six Wistar rats received a 2-U i njection of BTX in the right quadriceps. Six rats were similarly injected w ith saline and were used as control, Paralysis of the quadriceps was obtain ed 4-5 days after the injection. Animals were killed 4 weeks after the BTX injection. The bone mineral content (BMC) was measured by dual-energy X-ray absorptiometry (DXA) on the femur and tibia, No side-to-side difference wa s observed for BMC on the whole tibia and femur in the BTX group. When subr egions were selected in the bones, a significant decrease in BMC was obtain ed on the proximal tibia (-17,4 +/- 2.5%, p < 0.02), No significant differe nce could be observed on the proximal or distal femur, nor on the diaphysea l shafts, Numeric X-rays were done and a region of interest was transferred to an image analyzer, The texture of the trabecular bone was analyzed by t he run length and fractal methods (skyscrapers and blanket). Significant di fferences were obtained on the proximal tibia for all methods except with f ractal skyscrapers. On the distal femur, significant differences were obtai ned with the run length method, and the skyscrapers and the blanket method in the vertical direction. No differences were obtained with any method on the tibia and femur from control animals. Bone is a highly anisotropic mate rial and its architecture at the microscopic level is conditioned by strain s. The trabecular pattern differs in the proximal tibia than in the distal femural, Depending on the trabecular anisotropy, the algorithms can be more or less pertinent. BTX induced a significant bone loss on the bony subpart s that are directly influenced by disuse. Texture analysis of X-ray images can reveal differences that were not evidenced by naked eyes, However, a co mbination of several methods appears necessary to appreciate the bone loss. (C) 2001 by Elsevier Science me. All rights reserved.