Biomechanical Comparison of Skip-level Cervical Disc Arthroplasty and Skip-level Cervical Discectomy and Fusion

Introduction: This study aimed to assess the biomechanical distinctions between skip-level Anterior Cervical Discectomy and Fusion, skip-level Artificial Disc Replacement, and a hybrid approach integrating both ACDF and ADR. The current landscape of spinal surgery research shows that while ACDF is highly effective for stability, it often restricts motion, potentially increasing the risk of adjacent segment degeneration. Conversely, ADR is known for preserving more natural spinal movement but may introduce higher stress at adjacent levels. A hybrid technique that combines ACDF and ADR seeks to balance stability with motion preservation. This research fills a critical gap by comparing these methods to inform optimal surgical strategies that minimize complications and promote better biomechanical outcomes.

Methods: A finite element model of the cervical spine (C3-T1) was constructed utilizing 3D modeling techniques derived from computed tomography (CT) data. Three surgical scenarios were simulated: skip-level ACDF (C4-C5, C6-C7), skip-level ADR at the corresponding levels, and a hybrid approach combining ACDF at C4-C5 and ADR at C6-C7. Simulations encompassed flexion, extension, lateral bending, and axial rotation. The study quantified stress distribution, intradiscal pressure (IDP), facet joint forces, and range of motion (ROM) to evaluate the potential for adjacent segment degeneration (ASD).

Results: ADR demonstrated lower stress levels and preserved motion at the operated levels, particularly during flexion and lateral bending. However, it exhibited elevated stresses at adjacent levels. ACDF exhibited enhanced stability at the operated levels but restricted motion, thereby increasing the risk of ASD. The hybrid approach yielded intermediate outcomes, striking a balance between stress distribution and motion preservation.

Conclusion : Skip-level ADR promotes natural motion but may elevate the risk of adjacent segment degeneration. Skip-level ACDF provides superior stability but restricts motion, leading to elevated adjacent segment stress. The hybrid approach offers a compromise by harmonizing stability and motion preservation, potentially mitigating the risk of ASD.