6 Ulmer JL, Mathews VP, Elster AD, King JC. Lumbar spondylolysis without spondylolisthesis: recognition of isolated posterior element subluxation on sagital MR. Am J Neuroradiology. 7:1393, 1995.
Spondylolysis is an osseous defect found in both symptomatic and asymptomatic individuals. It predisposes to pathologic intervertebral subluxation or spondylolisthesis, most commonly occurring at the L5-S1 level. The pars defects are thought to represent chronic stress related injuries. Although these often occur during the first decade of life, accompanying vertebral problems develop somewhat later in life. It is important for the interpreter of MR to recognize both the primary and ancillary findings of spondylolysis, and in patients with spondylolisthesis, characteristic MR findings allow differentiation of degenerative versus isthmic causes. MR’s ability to grade disease severity and directly visualize nerve root involvement assists in treatment decisions.
Type I. Dysplastic: This type results from congenital abnormalities of the upper sacral facets or inferior facets of the fifth lumbar vertebra that allow slipping of L5 on S1. There is no pars interarticularis defect in this type. The sacrum is not strong enough to withstand the weight and stress. Thus, the pars and inferior facets of L5 are deformed. If the pars elongates, it is impossible to differentiate it by x-ray from the isthmic (type II b) Spondylolisthesis. If the pars separates, it becomes impossible to differentiate it by x-ray from the isthmic lytic (type II a) Spondylolisthesis. This type is also associated with sacral and neural arch deficiencies. It has a familial tendency.
In Spondylolisthesis with a significant slip, a step-off at the lumbosacral junction is palpable, motion of the lumbar spine is restricted, and hamstring tightness is evident on straight leg raising. As the vertebral body displaces anteriorly, the individual assumes a lordotic posture above the level of the slip to compensate for the displacement. Adults may have objective signs of nerve root compression, such as motor weakness, reflex change, or sensory deficit. These signs are seldom seen in children.
Neurogenic Claudication 50% - worse with standing, relieved by flexion - claudication distance is variable - sensory changes - normal pulses 4. Cauda Equina 5% ROM - normal lumbar forward flexion - pain on extension Minimal tenderness & spasm Neurological deficit 50% - sensory alteration 30% - weakness 20% AP - facet hypertrophy / osteophyte formation Lateral - mild forward slip Dynamic Views - >10° or 4mm = objective instability Degeneration of facet Demonstrate stenosis with spondylolithesis Don't tend to progress past Grade II Do well if have no neurological symptoms Often need surgery for neurological claudication / stenosis Mild symptoms / short duration / unfit for surgery Activity modification / analgesics / physio Weinstein et al N Eng J Med 2007 - RCT of operative v non operative, multicentred - operative group had substantial improvement in pain and function at 2 years Pearson et al Spine 2009 - SPORT - RCT of operative v non operative - operative group had significantly better outcomes - grade 1 better outcome than grade 2 with surgery - dynamic instability better outcome than static - failure of non operative treatment - radiculopathy / neurogenic claudication - progressive neurological defect - bladder or bowel symptoms 1. Decompress + fusion - demonstrated superior results in degenerative spondylolithesis Herkowitz et al Spine 1991 - fusion & decompression alone had better results at 3 years than decompression alone - slip increased 95% vs 30% 2. Instrumentation - instrumentation increases fusion rate - ?
At times, direct visualization of a pars defect is difficult on sagittal MR images, and thus it may be difficult to determine whether a patient with spondylolisthesis has a degenerative origin or if the malalignment is due to spondylolysis. In such cases, characteristic ancillary findings can be utilized to differentiate degenerative spondylolisthesis from isthmic spondylolisthesis. An appearance that we have found to be highly characteristic of isthmic spondylolisthesis is the horizontal neural foramina sign. In patients with spondylolysis, the neural foramina often assume a horizontal configuration on far lateral sagittal images (9a,9b). This feature is not present in degenerative spondylolisthesis, and the configuration also accounts for radiculopathy due to foraminal stenosis in patients with more severe isthmic spondylolisthesis.
Imaging evaluation of a patient with low back pain typically begins with a series of lumbar spine radiographs. Spondylolysis is usually evident on lateral radiographs, although oblique projections may be useful. On frontal projections, fragmentation of the lamina may be identified.4 If spondylolisthesis is present, it should be graded according to the Myerding system,5 with grade I indicating anterior subluxation of less than 25%; grade II, 25% to 50%; grade III, 50% to 75%; and grade IV, 75% to 100%.
Many patients with spondylolysis are asymptomatic. Of those with symptoms, approximately one-quarter are associated with spondylolisthesis.3 Pain is usually limited to the low back. If the pain radiates, it is usually to the buttocks or the back of the thigh and is often from hamstring tightness rather than lumbar radiculopathy. With associated higher grade spondylolisthesis, however, radiculopathy becomes more common due to associated foraminal stenosis.
As in our patient, spondylolysis may lead to spondylolisthesis, a forward (ventral) subluxation of an upper vertebra on a lower vertebra. Wiltse and coworkers have classified spondylolisthesis into five types based upon etiology:12
(5a) A 3D illustration of the lumbosacral region demonstrates the typical location of the osseous defect in patients with spondylolysis. Illustration courtesy of Michael E. Stadnick, M.D.
Diagnosing Lumbar Radiculopathy
An MRI is most often used to confirm the diagnosis of lumbar radiculopathy. If you have had an MRI taken within the past year, the physicians at The Bonati Institute will review your MRI. There is no obligation when you have your MRI films reviewed by The Bonati Institute, and you'll receive a written report outlining the specific findings of the Bonati team of experts.
Lumbar radiculopathy is more commonly known as sciatica. It is not to be confused with myelopathy--pathological changes to the spinal cord--or radiculitis--irritation of the nerve root. It's important to have an accurate diagnosis before beginning any type of intervention. The diagnostic process may include electrodiagnostic studies to rule out or confirm other types of disease processes.
(7a) T1- and (7b) T2- weighted sagittal images of the lumbar spine in a 35 year-old male who presented with 4-5 months of bilateral lower extremity pain are provided. A defect of the pars interarticularis is seen (arrows) with cortical interruption and a resultant grade I spondylolisthesis. Reactive marrow changes are also present adjacent to the pars defect with increased signal within the marrow (arrowheads) on both the T1 and T2 weighted images.