Peripheral nerve injury may lead to the formation of a painful
neuroma. In patients, palpating the tissue overlying a
neuroma evokes paraesthesias/dysaesthesias in the distribution of the injured nerve. Previous animal models of
neuropathic pain have focused on the
mechanical hyperalgesia and
allodynia that develops at a location distant from the site of injury and not on the
pain from direct stimulation of the
neuroma. We describe a new animal model of
neuroma pain in which the
neuroma was located in a position that is accessible to mechanical testing and outside of the innervation territory of the injured nerve. This allowed testing of
pain in response to mechanical stimulation of the
neuroma (which we call
neuroma tenderness) independent of
pain due to
mechanical hyperalgesia. In the tibial
neuroma transposition (
TNT) model, the posterior tibial nerve was ligated and transected in the foot just proximal to the plantar bifurcation. Using a subcutaneous tunnel, the end of the ligated nerve was positioned just superior to the lateral malleolus. Mechanical stimulation of the
neuroma produced a profound withdrawal behavior that could be distinguished from the
hyperalgesia that developed on the hind paw. The
neuroma tenderness (but not the
hyperalgesia) was reversed by local
lidocaine injection and by proximal transection of the tibial nerve. Afferents originating from the
neuroma exhibited spontaneous activity and responses to mechanical stimulation of the
neuroma. The
TNT model provides a useful tool to investigate the differential mechanisms underlying the
neuroma tenderness and
mechanical hyperalgesia associated with
neuropathic pain.