Modified alpha wrap techniques for dynamic urethral graciloplasty in an animal model.

Urethral sphincter reconstruction with a stimulated skeletal muscle flap has been used for treatment of severe intrinsic sphincter deficiency. Urethral strictures and failures were reported in some of the initial experiences. The etiology of these problems is not known, but elevated resting urethral pressures and excessive urethral displacement with stimulation are possible causes. We modified two operative techniques in forming dynamic urinary graciloplasty (DUG) in an attempt to minimize resting urethral pressure without stimulation and urethral mobility during stimulation. Two types of DUG were used. In the first group, a small flap (partial muscle wrap) from the gracilis muscle with an attachment site on the muscle was constructed in four dogs. In the second group, three dogs with a modified alpha wrap and proximal attachments were used. All of the gracilis muscle wraps were stimulated using an implanted programmable pulse stimulator with electrodes attached over the motor nerve. Following a 2-week, postrecovery period, urethral pressure measurements were obtained with and without stimulation. Five weeks were used for stimulation to condition the muscle. This was followed by 4 weeks of continuous stimulation. Thus, devices were implanted for 11 weeks. Before conditioning of the muscles was initiated, the partial muscle wrap pressure at rest was 42 +/- 27 cm H2O, which was higher than the incomplete alpha wrap resting pressure of 20 +/- 4 cm H2O. Stimulated partial flap pressure was 161 +/- 50 cm H2O, and stimulated modified alpha wrap pressures was 71 +/- 27 cm H2O. After conditioning with the modified alpha wrap, the resting and stimulated pressures were unchanged from before conditioning. Technical problems precluded collection of data during the conditioning period in dogs with partial flaps. During stimulation, the partial muscle wrap demonstrated marked deviation, whereas the modified alpha wrap had minimal urethral movement. Postmortem evaluation indicated no urethral stricture or fistula formation with either of the two types of wraps. The modified alpha wrap had several positive features. Advantages over the partial wrap were minimal resting pressures, reduced urethral mobility, and adequate sustained pressures during stimulation. Therefore, in contrast to the partial gracilis muscle wrap, aspects of the incomplete alpha wrap should be considered further for DUG.