SPONDYLOLISTHESIS

Spondylolisthesis means forward slipping of a vertebra on the one below. The term spondylolisthesis is derived from the Greek words “spondylos” (meaning vertebra) and “olisthesis” (meaning to slip). This forward slipping of the vertebra occurs when the posterior (back part) hook mechanism of the vertebra is damaged by one of the following conditions:

1. Congenital defect of the facet joints or hook mechanism
2. Defect in the pars interarticularis. This is referred to as isthmic spondylolisthesis. The basic lesion consists of a stress or fatigue fracture of the pars interarticularis (the portion between the upper and lower facet joints). The highest prevalence occurs at ages 5 to 7 years and again during increased activity at ages 11 to 16 years. The lowest incidence is found in black woman (1, 1 %) and the highest in young sportsmen with an incidence of up to 50 percent in gymnasts and 36 percent in weightlifters. It occurs in approximately five percent of the general population. The L5/S1 level is most commonly involved followed by L4/5.
3. Degeneration of the facet joints with destruction of the cartilage (degenerative spondylolisthesis). This condition occurs in an older population group with the highest incidence in the sixties and seventies. In the late stages of the disease severe narrowing of the spinal canal (spinal stenosis) and the nerve root canal occurs. The L4/5 level is most commonly involved.
4. Pathological disease where tumour or infection cause elongation or destruction of the pars interarticularis.
5. Trauma of the spine with fracture of any part of the hook mechanism except the pars interarticularis.

DIAGNOSIS

1. Plainly x-rays remain the most important single modality to determine anterior displacement, rotation, lumbar lordosis (spinal curvature) and the sacral angulation. It also provides evidence of the type of spondylolisthesis in most patients.
2. CT scan (computed tomography) is rarely indicated when plain x-rays failed to determine the lesion in the pars interarticularis in doubtful cases.
3. Bone scan (Technicium 99) is the most sensitive modality for detecting early stress fractures in children and young adults.
4. MRI (Magnetic Resonance Imaging) is important for the diagnosis of neurological compression associated with the spondylolisthesis

TREATMENT

1. CONSERVATIVE TREATMENT

Physiotherapy, back exercise programme under the supervision of a biokineticist, patient education with postural information by an occupational therapist and weight loss if indicated remain the cornerstones of conservative treatment and give good results in up to 80 percent of patients.

2. SURGICAL TREATMENT

Surgical treatment is indicated when the conservative treatment failed to alleviate the pain and the pain intensity is so severe that the patient cannot live with the pain any longer. It is also indicated with neurological deficit, especially when progressive and in patients with a progressive slip.

The traditional surgical treatment consists of decompression of neurological tissue followed by a fusion without reduction of the slipped vertebra or instrumentation. Pedicle fixation instrumentation was introduced later and seems to increase the fusion and success rate. The most recent surgical treatment consists of decompression of the neurological tissue, reduction of the spondylolisthesis with restoration of the anatomy, followed by an anterior and posterior fusion and instrumentation.

An extensive back rehabilitation programme to restore normal function should always follow the surgical treatment.
Figure 1: On the left side an x-ray of an isthmic spondylolisthesis with a severe degree slip. The normal pars interarticularis of L4 is indicated by the small arrow and the defect at the L5 level by the large arrow.
Figure 2: The x-ray appearance after reduction of the spondylolisthesis with pedicle fixation instrumentation followed by an anterior and posterior fusion.