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Skeletal Radiology

, 37:443 | Cite as

Radiological findings and healing patterns of incomplete stress fractures of the pars interarticularis

  • Andrew J. Dunn
  • Robert S. D. CampbellEmail author
  • Peter E. Mayor
  • Dai Rees
Scientific Article

Abstract

Objective

The objective was to retrospectively record the CT and MRI features and healing patterns of acute, incomplete stress fractures of the pars interarticularis.

Method

The CT scans of 156 adolescents referred with suspected pars interarticularis stress fractures were reviewed. Patients with incomplete (grade 2) pars fractures were included in the study. Fractures were assessed on CT according to vertebral level, location of cortical involvement and direction of fracture propagation. MRI was also performed in 72 of the 156 cases. MRI images of incomplete fractures were assessed for the presence of marrow oedema and cortical integrity. Fracture healing patterns were characterised on follow-up CT imaging.

Results

Twenty-five incomplete fractures were identified in 23 patients on CT. All fractures involved the inferior or infero-medial cortex of the pars and propagated superiorly or superolaterally. Ninety-two percent of incomplete fractures demonstrated either complete or partial healing on follow-up imaging. Two (8%) cases progressed to complete fractures. Thirteen incomplete fractures in 11 patients confirmed on CT also had MRI, and 92% demonstrated oedema in the pars. Ten out of thirteen fractures (77%) showed a break in the infero-medial cortex with intact supero-lateral cortex, which correlated with the CT findings. MRI incorrectly graded one case as a complete (grade 3) fracture, and 2 cases as (grade 1) stress reaction. Six fractures had follow-up MRI, 67% showed partial or complete cortical healing, and the same number showed persistent marrow oedema.

Conclusions

Incomplete fracture of the pars interarticularis represents a stage of the evolution of a complete stress fracture. The direction of fracture propagation is consistent, and complete healing can be achieved in most cases with appropriate clinical management. CT best demonstrates fracture size and extent, and is the most appropriate modality for follow-up. MRI is limited in its ability to fully depict the cortical integrity of incomplete fractures of the pars, but the presence of marrow oedema on fat-saturated T2-weighted sequences is a useful means of detecting acute spondylolysis.

Keywords

Spondylolysis Pars interarticularis Stress fracture Computed tomography Magnetic resonance imaging Stress fracture 

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Copyright information

© ISS 2008

Authors and Affiliations

  • Andrew J. Dunn
    • 1
  • Robert S. D. Campbell
    • 1
    Email author
  • Peter E. Mayor
    • 2
  • Dai Rees
    • 3
  1. 1.Department of Medical ImagingRoyal Liverpool and Broadgreen University Teaching HospitalsLiverpoolUK
  2. 2.Department of Medical ImagingLeighton HospitalCreweUK
  3. 3.Department of Orthopaedic SurgeryRobert Jones and Agnes-Hunt Orthopaedic HospitalOswestryUK

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