P1. Compression of the lumbosacral trunk and S1 nerve root by calcific posterior branches of the internal iliac artery: a potential source of sciatic pain

Abstract

<h3>BACKGROUND CONTEXT</h3> Sciatic pain caused by nerve root compression can be painful and debilitating. Compression of the nerve roots comprising the sciatic nerve can occur at their immediate exit from the spinal cord or anywhere along their length. Identifying the precise location of nerve root compression is critical for effective treatment of clinical signs and symptoms. <h3>METHODS</h3> Pelvic dissections were performed on 20 human cadavers (7 males and 13 females) with a mean age of 79.9 years at the time of death (SD, 10.4; range, 63-101 years). The donors were not selected based on any particular medical history or by criteria other than their convenient availability. All of the donors were Caucasians from greater Minnesota. The bodies were embalmed in a solution containing isopropyl alcohol (70%), phenol (13%), formaldehyde (8%), sorbitol (8%) and Barquat MB-50 disinfectant (1%). Each cadaver was sectioned transversely with a handsaw at approximately the L3 vertebral level. The resulting abdominopelvic portion was then sectioned completely down the midline, producing two hemipelvis regions for dissection. The pelvic structures were dissected with conventional dissection instruments (forceps, scalpel, scissors and blunt probe). A Canon EOS Rebel T3i (with a Macro 0.25m/0.8 ft. lens) was used to take photographs during the various phases of each dissection. Both sides of the pelvis were dissected for each cadaver, except for two (due to poor tissue quality). The right side of one could not be dissected due to a large destructive hematoma in the pelvic wall. The left side of another could not be dissected due to tough fibrous adhesions in the pelvis from radiation therapy. <h3>RESULTS</h3> This study of cadaveric hemipelvis dissections provides evidence to support that calcific branches of the internal iliac artery may compress and deform underlying nerve roots. This deformation suggests nerve compression. Specifically, when the posterior division of the internal iliac artery or superior gluteal artery contains calcific plaque, they form a visible impression on the nerves they course over in approximately 85.7% of the time. In this study, the lumbosacral trunk is the most commonly compressed nerve root in the pelvis, but the S1 nerve root can be affected as well. When the blood vessels lacked calcific plaque, they did not produce visible deformation of the underlying nerves. <h3>CONCLUSIONS</h3> Understanding this potential mechanism of nerve compression in the pelvis has clinical significance for patients with sciatic pain. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.