Sagittal Alignment of a Strut Graft Affects Graft Subsidence and Clinical Outcomes of Anterior Cervical Corpectomy and Fusion

Abstract

Study design: Retrospective study.

Purpose: The purpose of this study was to investigate the influence of sagittal alignment of the strut graft on graft subsidence and clinical outcomes after anterior cervical corpectomy and fusion (ACCF).

Overview of literature: ACCF is a common technique for the treatment of various cervical pathologies. Although graft subsidence sometimes occurs after ACCF, it is one cause for poor clinical results. Malalignment of the strut graft is probably one of the factors associated with graft subsidence. However, to the best of our knowledge, no prior reports have demonstrated correlations between the alignment of the strut graft and clinical outcomes.

Methods: We evaluated 56 patients (33 men and 23 women; mean age, 59 years; range, 33-84 years; 45 with cervical spondylotic myelopathy and 11 with ossification of the posterior longitudinal ligament) who underwent one- or two-level ACCF with an autogenous fibular strut graft and anterior plating. The Japanese Orthopaedic Association (JOA) score recovery ratio for cervical spondylotic myelopathy was used to evaluate clinical outcomes. The JOA score and lateral radiograms were evaluated 1 week and 1 year postoperatively. Patients were divided into two groups (a straight group [group I] and an oblique group [group Z]) based on radiographic assessment of the sagittal alignment of the strut graft.

Results: Group I showed a significantly greater JOA score recovery ratio (p<0.05) and a significantly lower graft subsidence than group Z (p<0.01).

Conclusions: Our findings suggest that a straight alignment of the strut graft provides better clinical outcomes and lower incidence of graft subsidence after ACCF. In contrast, an oblique strut graft can lead to significantly increased strut graft subsidence and poor clinical results.

Keywords: Bone transplantation; Cervical vertebrae; Clinical study; Spinal cord compression; Spinal fusion.

Fig. 1. Typical examples of sagittal Cobb angle and span of the fused area. The C2–C7 lateral Cobb angle (α) (A), as a global cervical sagittal alignment, and segmental lateral Cobb angle (β) (B) were measured using Cobb's method. (B) The span of the fused area (γ) was measured from the midpoint of the superior endplate to that of the inferior endplate.

Fig. 2. Typical examples of the alignment of the strut graft. (A) The dotted line indicates the axis of the strut graft. Group I was defined as patients who received a straight strut graft, in which the strut axis was parallel to the line through the midpoints of both endplates of adjacent vertebrae. (B) Group Z was defined as patients who received an oblique strut graft, in which the strut axis was not parallel to the line through the midpoints of the endplates.