Extradural implantation of sacral anterior root stimulators. A technique for extradural deafferentation of the S2 to S5 segments and extradural implantation of stimulating electrodes is described, and its application to twelve patients with spinal cord lesions is reported. Nine patients use their implants for micturition, and seven are fully continent. The advantages and disadvantages of this technique compared with the more usual intrathecal procedure are discussed. 