Dorsal column lesion prevents mechanical hyperalgesia and allodynia in osteotomy model

Withdrawal reflex responses to graded von Frey filaments applied to the pla ntar 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 metho ds were employed to produce models of osteotomy; a small hole was drilled t hrough either the (1) tibia or (2) calcaneus (Houghton, A.K., Hewitt, E. an d Westlund, K.N., Enhanced withdrawal responses to mechanical and thermal s timuli 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 developme nt of mechanical hyperalgesia and allodynia which peaked at 2.5 h. Nocifens ive 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-lin e 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 t he medial part of the dorsal column are involved in the development of mech anical hyperalgesia and allodynia after bone hole injury. (C) 1999 Internat ional Association for the Study of Pain. Published by Elsevier Science B.V.