Diagnosing Pseudoarthrosis After Anterior Cervical Discectomy and Fusion

Abstract

Radiographic confirmation of fusion after anterior cervical discectomy and fusion (ACDF) surgery is a critical aspect of determining surgical success. However, there is a lack of established diagnostic radiographic parameters for pseudoarthrosis. The purpose of this study is to summarize the findings of previous studies, review the advantages and disadvantages of frequently employed diagnostic criteria, and present our recommended protocol of fusion assessment. This study identified randomized controlled trials, case-control studies, and prospective and retrospective cohort studies reporting on spinal fusion and how successful fusion after ACDF. Among the 39 articles reviewed, bridging bone across the operated levels on static radiographs was the most commonly used criteria to confirm fusion (31 of 39, 79%). Dynamic flexion-extension radiographs were used to assess for interspinous movement (ISM) (22 of 39, 56.4%) and change in Cobb angle (12 of 39, 30.8%). Computed tomography (CT) based findings (21 of 39, 53.8%) were employed in ambiguous cases with improved sensitivity and specificity. Reconstructed CT scans were used to assess for intragraft bridging bone and extragraft bridging bone (ExGBB). ExGBB were proved to have the highest diagnostic sensitivity and specificity for pseudoarthrosis detection when compared to all other radiographic criteria. The ISM <1 mm on dynamic flexion-extension radiographs had high diagnostic sensitivity and specificity as well. After our reviewing, we recommend using dynamic lateral flexion-extension cervical spine radiographs at 150% magnificationin which the interspinous motion <1 mm and superjacent interspinous motion ≥4 mm confirms fusion. In ambiguous cases, we recommend using reconstructed CT scans to evaluate for ExGBB.

Keywords: Anterior cervical arthrodesis surgery; Anterior cervical discectomy and fusion; Anterior cervical spine surgery; Cervical spine fusion; Fusion; Pseudarthrosis.

Fig. 1.

Measurement of interspinous movement (ISM) at superjacent level (C4–5) and operated levels (C5–7) on the 150% magnified flexion and extension radiographs. The superjacent ISM at C4–5 (A and a) is 10.2 mm, which indicates adequate dynamic motion ( > 4 mm). ISM at C5–6 (B and b) is 0.21 mm, which is consistent with our definition of fusion ( < 1 mm). ISM at C6–7 (C and c) is 5.13 mm, which indicates pseudoarthrosis ( > 1 mm).

Fig. 2.

Evaluating bone bridging on multiaxial reconstructed coronal and sagittal computed tomographic images. It appears to be fused with bone bridging formation at both C5–6 (A and a) and C6–7 (B and b) levels.

Fig. 3.

Evaluating extragraft bridging bone (ExGBB) on multiaxial reconstructed coronal and sagittal computed tomographic images. The top level (C5–6) shows ExGBB on both the coronal and sagittal images (A and a). The bottom level (C6–7) shows intragraft bone bridging on the coronal view (B) but demonstrates a cleft and no ExGBB on sagittal image (b), which indicates pseudoarthrosis. This is consistent with the results of interspinous movement evaluation on X-rays and was confirmed to be pseudoarthrosis with intraoperative exploration.