Radiological Determination of Postoperative Cervical Fusion: A Systematic Review

Abstract

Study design: Systematic review.

Objective: To determine best criteria for radiological determination of postoperative subaxial cervical fusion to be applied to current clinical practice and ongoing future research assessing fusion to standardize assessment and improve comparability.

Summary of background data: Despite availability of multiple imaging modalities and criteria, there remains no method of determining cervical fusion with absolute certainty, nor clear consensus on specific criteria to be applied.

Methods: A systematic search in MEDLINE/Cochrane Collaboration Library (through March 2014). Included studies assessed C2 to C7 via anterior or posterior approach, at 12 weeks or more postoperative, with any graft or implant. Overall body of evidence with respect to 6 posited key questions was determined using Grading of Recommendations Assessment, Development and Evaluation and Agency for Healthcare Research and Quality precepts.

Results: Of plain radiographical modalities, there is moderate evidence that the interspinous process motion method (<1 mm) is more accurate than the Cobb angle method for assessing anterior cervical fusion. Of the advanced imaging modalities, there is moderate evidence that computed tomography (CT) is more accurate and reliable than magnetic resonance imaging in assessing anterior cervical fusion. There is insufficient evidence regarding the optimal modality and criteria for assessing posterior cervical fusions and insufficient evidence to support a single time point after surgery as being optimal for determining fusion, although some evidence suggest that reliability of radiography and CT improves with increasing time postoperatively.

Conclusion: We recommend using less than 1-mm motion as the initial modality for determining anterior cervical arthrodesis for both clinical and research applications. If further imaging is needed because of indeterminate radiographical evaluation, we recommend CT, which has relatively high accuracy and reliability, but due to greater radiation exposure and cost, it is not routinely suggested. We recommend that plain radiographs also be the initial method of determining posterior cervical fusion but suggest a lower threshold for obtaining CT scans because dynamic radiographs may not be as useful if spinous processes have been removed by laminectomy.

Level of evidence: 1.