Images below require Macromedia's Flash Player to view

Neuroradiology Case of the Week

Case 380

January 2009

Iris Young, RPA-C and P-L Westesson MD, PhD, DDS

Clinical Presentation: Patient is a 51-year-old female with low back pain that radiates into the bilateral lower extremities, left side worse than right. Pain moves into the buttocks, along the left lateral thigh to the knee. At times, pain radiates into the dorsum of the left foot, associated with numbness, tingling, and weakness.

Imaging Findings: CT with intrathecal contrast and myelographic imaging shows a grade II anterolisthesis of L5 on S1 with a corresponding bilateral pars interarticularis fractures of L5. There is a significant shift of the spondylolisthesis which is improved in the supine sagittal images, compared to the standing myelographic images.

Diagnosis: Unstable Grade II anterolisthesis of L5 on S1 with bilateral spondylolysis of L5

Discussion: Spondylolysis is a defect in the pars interarticularis, which is the weakest portion of the vertebrae. Ninety percent of pars defects occur at the L5 level, less commonly at L4 and L3. Elongation of the pars is thought to be due to repetitive microfractures with subsequent healing in an elongated position. Athletes in gymnastics, soccer, tennis, baseball, football, and wrestling are more likely to have symptomatic spondylolysis at some point. When the defects are bilateral, spondylolisthesis may occur.
     Spondylolisthesis is the forward slippage of one vertebral body on another. This most commonly occurs at the lumbosacral junction with L5 slipping over S1, but it can occur at higher levels as well. The etiology of spondylolisthesis is multifactorial, with a hereditary disposition combined with forces of posture, gravity and rotational forces. Six types of spondylolisthesis were classified by Wiltse, et al. [6] according to etiology: dysplastic or congenital, isthmic, degenerative, traumatic, pathologic, and iatrogenic. The amount of vertebral subluxation was adapted from Meyerding [7]: Grade 1-slippage of less than 25% of the vertebral diameter, Grade 2 is 25-50%, Grade 3 is 50-75%, Grade 4 is 75-100% and spondyloptosis is greater than 100% subluxation.
     The instability of the spine can lead to back pain, radiculopathy, and neurogenc claudication from lateral recess stenosis, facet and ligamentous hypertrophy and/or disc herniation. The pain is sometimes relieved when the patient flexes the spine by sitting or by leaning on shopping carts. Flexion increases canal size by stretching the protruding ligamentum flavum and enlargement of the foramina. This relieves the pressure on the exiting nerve roots and decreases the pain. The goal of surgery is to stabilize the segment with listhesis and decompress any of the neural elements under pressure.

References:

1. Krupski W, Majcher P, Tatara MR. Computed tomography diagnostic of lumbar spondylolysis. Ortop Traumatol Rehabil. 2004 Oct 30;6(5):652-7. [PubMed]
2. Newman PH, Stone KH. The etiology of spondylolisthesis. J Bone Joint Surg Br 1963 Feb 45B;(1):39-59. [PDF]
3. Theiss SM. Isthmic spondylolisthesis and spondylolysis. J South Orthop Assoc. 2001 Fall;10(3):164-72. [PubMed]
4. Vokshoor A, Jamall AR. Spondylolisthesis, spondylolysis, and spondylosis. Emedicine Feb 1, 2008. http://emedicine.medscape.com/article/1266860-overview
5. Weinberg EP. Spondylolysis. Emedicine, Jan. 7, 2008. http://emedicine.medscape.com/article/395916-overview
6. Wiltse LL, Newman PH, Macnab I. Classification of spondylolysis and spondylolisthesis. Clin Orthop Relat Res. 1976 Jun;(117):23-9. [PubMed]
7. Meyerding HW. Spondylolisthesis. Surg Gynecol Obstet. 1932; 54:31-7.