Interadductor approach to obturator nerve blockade for spastic conditions of adductor thigh muscles

The authors describe a new approach for the management of adductor muscle spasm associated with multiple sclerosis and paraplegia.

An obturator nerve block was performed by needle insertion behind the upper end of the adductor longus muscle; the needle was directed laterally, with slight upward and posterior inclination, toward the obturator canal. The obturator nerve was identified by its response to nerve stimulation. An initial diagnostic block using 5 mL of 2.0% lidocaine followed by two or three prognostic blocks using 5 mL of 0.5% bupivacaine and 1:200,000 epinephrine were performed. In the final block, 5 mL of 6.0% phenol in glycerin was injected.

Evaluation of the efficacy of the block was achieved in terms of its success rate, the degree of alleviation of muscle spasm, the improvement of gait in the patients with multiple sclerosis, and the facilitation of nursing hygienic care in bedridden patients. In comparison with the traditional approach, the success rate and improvements were highly significant.

The interadductor approach is a new approach based on the anatomy of the obturator nerve trunk, which, though in the obturator canal, is shielded by its osseous part from the anteroposterior perspective of the traditional approach. The interadductor approach allows needle positioning inside the obturator canal through a mediolateral perspective, thus facilitating the blockade of the obturator nerve trunk before it branches immediately outside the canal. The new approach proved to be successful, reproducible and without complications.