Construction Of Artificial Abdominal Wall-bladder Reflex Arc Using Saphenous Nerve With Blood Vessel In Dogs

Since breakthroughs are absent in the research on spinal cord regeneration to date, urination and defecation disorders caused by spinal cord injury (SCI) after severe trauma remain a tough problem facing orthopedists. Neurogenic bladder dysfunction, which leads to serious urinary retention and infections of the urinary tract, and even chronic renal failure, is the leading cause of death in paraplegic patients. In addition, ever-increasing SCI patients give rise to grave economic and societal issues. Traditional treatments targeting bladder-controlling nerve roots and detrusor muscles, such as bladder denervation, electrically or magnetically stimulated urination, and detrusor musculoplasty, bring about poor effects and have many limitations. Over recent years, researchers, basing on previous studies on bladder reinnervation, have constructed the artificial bladder reflex arcs using intact somatic reflexes under the paraplegic level, helping the patients maintain controllable urination. Hence, without being aided by instruments or equipment, SCI patients can partially or mostly recover bladder urination after surgery on the remnant spinal cord and nerves, which provides a bright future for unraveling this medical problem. The progress in the diagnosis and treatment of SCI and the increasing application and improvement of microsurgical techniques has provided favorable conditions for the treatment of post-SCI nervous bladder. Since the 1990s, by improving operative methods and techniques and by using the remnant spinal reflexes, many authors have helped SCI patients maintain controllable urination, thus achieving breakthroughs in this field. In 1998, Hou CL first reconstructed the artificial tendon-spinal cord center-bladder reflex arc using the remnant achilles reflex under the paraplegic level in 8 patients, resulting in satisfactory therapeutic effects. In 2003, Zhang SC attempted to reestablish the urination and defecation functions in 30 paraplegic patients by using selective anastomosis of intercostal nerves with blood vessels with sacral nerve roots, resulting in recovery of active urination in 23 patients. In 15 paraplegic patients with functional disorders of the detrusor muscles and sphincter of the bladder, Xiao CG retained the left dorsal root (DR) of L 5 nerve root, and anastomosed L 5 nerve root with the ventral root (VR) of S 2 or S 3 nerve root. Of these patients treated, 10 attained satisfactory control over the bladder, and their renal function, detrusor reflex, and coordination of detrusor muscles and sphincters ameliorate or turn normal. Since then, the authors have confirmed by morphological, electrophysiological, and functional means that after anastomosis of the motor efferent limb of the somatic nerve with autonomic nerve, the former grows, through regenerated axons, into parasympathetic fibers of the latter, transmitting motor impulse soundly. The studies above realized controllable urination by using the remnant reflexes under the SCI level. However, in this present study we attained that goal by constructing the abdominal wall-artificial bladder reflex arc in continuous spinal cord segments through free grafting and bridging anastomosis using saphenous nerves with saphenous veins. Based on this achievement, an animal model for sensation reflex pathways was also established. This study is composed of two sections: 1. Establishment of canine model for artificial abdominal wall-bladder reflex arc using saphenous nerve with blood vessels: The artificial canine abdominal wall-spinal cord center-bladder reflex pathway was constructed by free grafting and bridging anastomosis using saphenous nerves with saphenous veins. Microsurgical anastomoses were performed within canine dura mater between the dorsal and the ventral roots of T12-S2 nerve roots using saphenous nerves with saphenous veins. End-to-side anastomoses were applied to anastomose saphenous nerves and T12 dorsal root; otherwise, end-to-end anastomoses were applied. For the experimental group, saphenous veins were anastomosed with the ramifications of the intercostal arteries of similar sizes; for the control group, only saphenous nerves were anastomosed. 2. After the dogs had been fed for 180 d, function of the artificial reflex arc was evaluated: For the experimental and the control groups, models for complete transection of spinal cord blow the T12 level were established, electrophysiology (action potential curve and bladder electromyography), urinary dynamics, and retrograde tracing of horseradish peroxidase (HRP), and functional evaluation were conducted. Results: Electrophysiological studies revealed that in both the experimental and thecontrol groups, all the anastomotic junctions transmitted action potentials, and that stimulations of the detected sites brought about recordable electromyograms of the bladder, with action potential curves and bladder electromyograms similar to those before paraplegia. Study of urinary dynamics showed that 48 h after paraplegia, electric stimulation elicited bladder contraction via artificial reflex arc to the extent of 67% of the normal value in the experimental group and 49% of the normal value in the control group, respectively; stimulation of the abdominal wall also elicited bladder contraction to the extent of 53% of the normal value in the experimental group and 48% of the normal value in the control group, respectively; stimulation of the right dorsal root of S2 elicited bladder contraction to the extent of 34% of the normal value in the experimental group and 21% of the normal value in the control group, respectively. HRP tracing showed a large number of brownish black, HRP-labeled cells that had intact contours of cell nucleus or cell body and obvious processes. Computerized image analysis revealed that the number of HRP-labeled positive cell bodies at the T12 level was 38% of the normal value in the experimental group and 30% of the normal value in the control group. Conclusions: To reinnervate the nervous bladder caused by SCI, based on the intact abdominal wall reflex arc above the paraplegic level, the artificial abdominal wall-spinal cord center-bladder reflex arc was constructed by free grafting and bridging anastomosis using saphenous nerves with saphenous veins. This intervention may help realize controllable bladder urination. Early functional recovery of the bladder in the group grafted with saphenous nerves with blood vessels is superior to that in the group grafted with simply saphenous nerves. Meanwhile, bladder sensory efferent pathways were constructed, which provided an animal model for contructing nervous pathways for autonomous urination by nervous bladder caused by SCI.