Spinal Fusion Evaluation in Various Settings: A Summary of Human-Only Studies

Abstract

Degenerative spinal conditions may lead to abnormal motion and biomechanical instability of diseased spinal segments, resulting in pain, deformity, and neural element compromise. Various spinal fusion techniques have been developed over the years to address spinal segment instability. Degenerative conditions of the lumbar spine can be addressed through different approaches in terms of fusion. These include posterolateral fusion, posterior lumbar interbody fusion, and transforaminal interbody fusion, which are performed with the patient lying prone. Anteriorly, degenerative lumbar spine conditions can be addressed with anterior lumbar interbody fusion, direct lateral (transpsoas) lumbar interbody fusion, or oblique lumbar interbody fusion (using an anterior to psoas approach). The cervical spine with degenerative changes can be treated with fusion anteriorly, using anterior cervical discectomy and fusion, or posteriorly, with posterior cervical decompression and fusion. The success or failure of the fusion procedure is determined on the absence or presence of pseudarthrosis based on clinical findings supplemented by diagnostic evidence of bridging bone. Imaging modalities most commonly used for evaluation of fusion include radiographs, magnetic resonance imaging, and computed tomography, with CT as the gold standard for assessment. Recent studies support CT as the imaging modality of choice, with some studies presenting different techniques that may aid in the evaluation of fusion status. In the hope of attaining higher outcomes for fusion along with decrease in morbidity associated with graft harvest, several bone graft substitutes and extenders have been developed. Several studies have been produced supporting their use. None have provided clear-cut evidence or recommendations that would help determine any advantage of one bone graft substitute/extender over the other.