What is the role of SPECT in the workup of pars interarticularis injury?

Updated: Jan 22, 2019
  • Author: Gerard A Malanga, MD; Chief Editor: Craig C Young, MD  more...
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Answer

Radionuclide imaging studies, including planar bone scanning and, more specifically, SPECT bone scanning, have been found to be more sensitive than plain radiography in detecting pars lesions. Several authors comparing planar bone scan versus plain radiographs concluded that planar bone scans could potentially detect pars lesions earlier in the clinical course than could plain radiographs. Furthermore, it appears that bone scanning may be more sensitive in differentiating pain-producing pars lesions from incidentally found lesions.

In a study by Lowe et al, a group of patients found to have spondylolysis on plain films were further imaged with a bone scan. [42] A positive bone scan in each case correlated with the presence of LBP, whereas those with negative bone scans were all without pain. Similar results have been obtained in other studies, and it appears that bone scans may have a role in identifying those cases in which the spondylolytic lesion is the pain generator rather than just an incidental finding.

SPECT scanning has been found to be more sensitive than either plain radiography or planar bone scintigraphy in detecting spondylolysis and has, for the most part, replaced planar bone scanning as the radionuclide imaging study of first choice in suspected pars interarticularis lesions.

Studies carried out that compared plain radiography, planar bone scanning, and SPECT scanning by Bodner et al and Bellah et al, respectively, both found the SPECT scan to be more sensitive compared with the other 2 imaging studies. [43, 44] Furthermore, as with planar bone scans, SPECT scans may be helpful in detecting symptomatic pars lesions from asymptomatic lesions as they can identify metabolically active bone change.

A particularly interesting study comparing the clinical outcome following surgery for pars interarticularis defects with SPECT scanning found that patients who became pain free after surgery have positive preoperative SPECT scans, whereas those in whom pain persisted after surgery had negative preoperative scans. This finding implies that those with negative scans may have been experiencing their symptomatology from a source other than the pars lesion.

A Japanese study was performed to clarify the role of SPECT scans. In this study, plain radiographs and SPECT scans were obtained in young patients (mean age 15.6 y) who had LBP and were clinically suspected of having spondylolysis. This study concluded that the SPECT scan is primarily indicated in patients with no apparent abnormality seen on plain radiograph and/or CT scan and who are still suspected of having spondylolysis from their history and physical examination. A positive study was thought to represent a stress reaction in the pars interarticularis, which may be amenable to rest and immobilization. A negative study at this point strongly suggests that spondylolysis is not the likely source of pain and may warrant further imaging to evaluate for a different pathology that may be causing symptomatology. [45]

Herring and Standaert offer the opinion that considering the relatively high radiation exposure one is subjected to in undergoing multiple views on plain film, along with the increased sensitivity of SPECT scanning, the latter may be the most appropriate choice for the initial screening study. [46] The authors feel with the advantages of SPECT scanning, multiple plain radiographic views as an initial screening tool may not play a role in detecting spondylolytic lesions. [46] In cases in which plain radiographs do reveal pars lesions, SPECT scanning can be helpful in documenting the acuity of injury.


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