Epidural fat interposition between dura mater and spinous process: a new sign for the diagnosis of spondylolysis on MR imaging of the lumbar spine

Abstract

The purpose of this study was to assess the diagnostic value of epidural fat interposition between the dura mater and spinous process of L5 as an indirect sign of spondylolysis on mid-sagittal MR imaging of the lumbar spine. Mid-sagittal T1-weighted MR images of the lumbar spine of 85 patients with spondylolysis and 93 patients without pars interarticularis fractures were randomized and evaluated by a masked reader. After a training sample of five cases, the reader was asked to note the presence or absence of epidural fat interposition between the dura mater and spinous process of L5 on the randomized images. The epidural fat interposition between the dura mater and spinous process of L5 was noted in 67 out of the 85 patients with spondylolysis (78.8%) and three of the patients without pars interarticularis fracture (3.2%). The difference was statistically significant ( P<0.01). This sign has a specificity of 96.7%, sensitivity of 78.8%, positive predictive value of 95.7%, negative predictive value of 83.3% and accuracy of 88.2% for diagnosis of spondylolysis. Epidural fat interposition between the dura mater and spinous process may be a helpful sign for the diagnosis of spondylolysis on mid-sagittal MR imaging of the lumbar spine.

Hypoplasia of L5 and Wedging and Pseudospondylolisthesis in Patients with Spondylolysis: Study with MR Imaging

“…Other less frequent signs include the wedging of the posterior aspect of the vertebral body, bone marrow changes in the pedicle, 8 and epidural fat interposition between the dura mater and the spinous process. 13 In our study, we could confirm with MR imaging the conclusions of Frank and Miller 1 that hypoplasia of L5 is a strong predictor of bilateral spondylolysis, especially in the absence of spondylolisthesis. In our series, there was no patient with hypoplasia of L5 who did not present with bilateral spondylolysis, though in the series of Frank and Miller, 1 there was 1 patient with thinning of the isthmus without a complete defect.…”

Imaging of Orthopedic Sports Injuries

“…With such abnormal movement the increased stress on the facet joints and the spinal nerves in the adjacent intervertebral foramina may be explained. Sherif and Mahfouz (2004) mentioned the interposition of fatty tissue between the dural sac and the spinous process of L5 as a helpful indirect sign of spondylolysis. 23.3).…”

Contribuição dos métodos de diagnóstico por imagem na avaliação da espondilólise

“…O sinal mais confiável de pars interarticularis normal à RM é a continuidade da intensidade de sinal da medular óssea, através da pars interarticularis, principalmente, nas seqüências ponderadas em T1. Entretanto, este aspecto é visualizado somente em 30-66% dos casos (5) .…”

“…Alterações escleróticas com perda do sinal da medular óssea podem ser causadas pelas alterações degenerativas das facetas articulares adjacentes e efeito de volume parcial das partes moles circunjacentes. Por isso, sinais indiretos têm sido usados para auxiliar no diagnóstico (5) (Figura 6 D, E, F e G).…”