and low-grade spondylolisthesis in athletes
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
Spondylolysis and Spondylolisthesis - Patient
Most patients with spondylolysis or pars stress reactions respond favorably to non-operative treatment. Usually this treatment includes a period of rest or immobilization followed by physical therapy. The role and best type of bracing continue to be debated. In selective cases, epidural steroid injections or selective nerve root blocks help in controlling symptoms. Most authors agree that patients may return to normal activities when they are pain-free, regardless of whether there is radiographic evidence of pars healing.9
(11a) A T2-weighted axial image at the L4-5 level reveals severe bilateral facet hypertrophic changes (arrows). This feature is typical of a degenerative etiology of spondylolisthesis, and is rarely found in patients with spondylolysis.
Spondylolisthesis, Spondylolysis - Radsource
The final ancillary observation that may aid in the detection of spondylolysis is an abnormal wedging of the posterior aspect of the vertebral body at the level of the pars defect. This finding is a well-known radiographic finding that occurs at the level of spondylolisthesis. It is unclear if this finding is an effect of the spondylolisthesis, a predisposing condition, or a combination of both. On sagittal MR images, wedging of the posterior vertebral body is seen both in patients with spondylolisthesis and in those with spondylolysis and no significant subluxation.8 Therefore, such wedging may suggest the presence of pars defects (Figure 8).
Spondylolisthesis, Spondylolysis ..
(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.
Spondylolysis & Spondylolisthesis in the Adolescent Athlete
Reactive marrow changes similar to those observed in patients with degenerative disc disease are identified within the posterior elements adjacent to pars defects in a significant number of patients. In one study, these changes were observed in 40% of patients with spondylolysis and were distributed as a function of age. This observation may be an additional clue that a pars defect is present (E,F) and may be a reflection of the duration of disease. Type I changes (similar to marrow edema – low signal on T1 and high signal on T2 images) are most commonly seen in patients less than 24 years of age. Type II changes (similar to fat signal – high signal on T1 and isointense or high signal on T2 images) are seen in patients with a median age of 35 years. Type III changes (similar to fibrous tissue – low signal on both T1 and T2 images) are seen in patients with a median age of 51 years.7 As both acute and chronic pars defects can demonstrate hyperintensity on routine T2-weighted images, fat-suppressed T2 or STIR sequences are often helpful in order to more easily identify marrow edema suggestive of more recent injury.
Spondylolysis and Spondylolisthesis in Athletes
A midline (6a) sagittal T2 weighted image from the same patient in A. The AP diameter of the canal at L1 measures 1.7cm (line 4) and the AP diameter of the canal at L5 measures 2.5cm (line 3). The ratio of L5:L1 is 1.47, which is above the normal value of 1.25. Even without this calculation, it is clear the canal is enlarged at the L5 level with the posterior elements displaced slightly posterior when compared with the posterior elements of the more cranial vertebral bodies.