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Experimental evidence that muscle atrophy impairs fracture healing
This study employed a rat model of femur union to find out more about how muscular atrophy and low muscle function impact fracture healing. Forty-four male rats were injected with two units of botulinum toxin-A (BXTA) into their quadriceps muscle on one side, and with saline into the corresponding muscle on the other side. Following an induced femur fracture, progress of fracture healing was assessed over a period of weeks. The fracture sites on both sides were examined by X-ray imaging and histologically, and bone biomechanical testing was also performed.
Injection of BXTA resulted in a significant loss of muscle weight and volume. At the 8 week point, when fracture healing was almost complete on the control side, the bone next to the BXTA treated muscle showed a clear residual gap on X-ray. Bone histology studies revealed a lack of woven bone or osseous calluses, and there was evidence of bone resorption. Finally, biomechanical testing indicated that the femur on the BXTA-treated side exhibited inferior mechanical properties compared with the control side.
Editor's comment: Bone union was adversely affected in the rats administered with botulinum toxin-A (BXTA) in the quadriceps, showing experimentally that a lack of muscle compression and mechanical stimulation can delay fracture repair.
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