Dorsal column lesion prevents mechanical hyperalgesia and allodynia in osteotomy model

Withdrawal reflex responses to graded von Frey filaments applied to the plantar surface of the paw were measured before and after bone hole damage in rats with either a dorsal column (DC) lesion or a sham DC lesion. Two methods were employed to produce models of osteotomy; a small hole was drilled through either the (1) tibia or (2) calcaneus (Houghton, A.K., Hewitt, E. and Westlund, K.N., Enhanced withdrawal responses to mechanical and thermal stimuli after bone injury, Pain, 73 (1997) 325-337). In the rats with a sham DC lesion, a hole through the tibia or calcaneus resulted in the development of mechanical hyperalgesia and allodynia which peaked at 2.5 h. Nocifensive behavior, characterized by a lifting and guarding of the damaged limb, was also observed in animals with a hole through the calcaneus. In contrast, we found that interrupting the dorsal column pathway with a small mid-line lesion (1 week prior to the osteotomy) prevented the development of both the primary and secondary mechanical hyperalgesia and allodynia but not the guarding of the damaged limb. This study provides evidence that axons in the medial part of the dorsal column are involved in the development of mechanical hyperalgesia and allodynia after bone hole injury.