Foraminotomy and Pitfalls

Introduction
Lumbosacral foraminotomy is performed for decompression of the 7th lumbar nerve roots within the L7-S1 neuroforamina. Nerve root compression can occur unilaterally or bilaterally and is usually caused by extruded disc material, reactive bone formation, hypertrophic ligament development, thickening of the facet joint capsule, or scar tissue caused by previous operations.

Clinical signs of foraminal nerve root compression may include rear limb lameness, hyperaesthesia, a poor withdrawal reflex occasionally combined with patellar hyperreflexia, and pain elicited by hind limb extension or lumbosacral palpation.

Proprioceptive deficits or even hind limb ataxia may be observed in cases of marked compression. Lameness caused by unilateral foraminal stenosis can be confused with similar features in posture and gait caused by cranial cruciate ligament pathology. Lameness may show a tendency to increase during activity. A reduced perineal reflex, tail flaccidity, and urinary and fecal incontinence occur only in the presence of concurrent severe nerve root compression in the central region of the lumbosacral spinal canal.

Prior to the availability of computed tomography (CT) and magnetic resonance imaging (MRI) the adequacy of the opening of the spinal foramina and the status of the 7th lumbar nerves travelling through them could not be effectively visualized. With the availability of MRT, the lumbosacral neuroforamina and the 7th lumbar nerve’s path out of the spinal canal could now be assessed. As lesions in this area were clearly identified, surgeons began investigating possible techniques to relieve nerve root compression.

The surgical procedure to relieve nerve root compression requires removal of the offending bone and soft tissue. An early technique involved the removal of the articular facets to free compressed nerve roots and was at one time a commonly performed procedure. However, because it may lead to severe instability it is no longer recommended and should be avoided (Danielsson and Sjöström, 2002).  [...]