Anterior Cervical Hybrid Constructs Reduce Upper Adjacent Segment Hypermobility Compared to Anterior Cervical Discectomy and Fusion

Introduction: Traditional surgical treatment for symptomatic cervical degenerative disc disease is anterior cervical discectomy and fusion (ACDF). However, there's increased risk of adjacent segment degeneration requiring additional surgery. Disc arthroplasty can preserve physiologic range of motion (pROM), decreasing the need for adjacent segment surgery. For patients with multilevel pathology requiring at least 1-level fusion, there is growing interest in hybrid (ACH) constructs as a partial motion-preserving procedure

Methods: In this single-center retrospective cohort study, 2- and 3-level ACH and ACDF cases were identified between 2013 and 2021. Patients with incomplete records, imaging, or less than 6 months of follow-up were excluded. Degrees of motion (DOM) were analyzed on flexion/extension views using Cobb angles to measure lordosis at C2-C7 (global), constructs, adjacent segments. Pre- and post-operative neutral lateral x-rays were analyzed for alignment parameters: global lordosis, cervical sagittal vertical axis, T1 slope. Differences were determined via independent t-test and Fisher’s exact test.

Results: 50 patients were in each cohort (2-level: 18 ACH, 20 ACDF) (3-level: 32 ACH, 30 ACDF). Hybrid patients were younger, (51 ACH, 59 ACDF, p< 0.001) with lower CCI scores (0.8 ACH, 1.7 ACDF, p< 0.001). Postoperatively, total ROM across the construct (16.3° ACH, 4.7° ACDF, p< 0.001) and total global ROM (38.0° ACH, 28.0° ACDF, p< 0.001) were greater in the ACH cohort. DOM decreased at the construct level were less in the ACH cohort (-10.0° ACH, -18.1° ACDF, p< 0.001). Postoperatively, DOM at the upper adjacent segment only increased in the ACDF cohort (-1.3° ACH, 1.6° ACDF, p< 0.005).

Conclusion : Hybrid constructs partially preserved motion across operative levels compared to ACDF constructs. Postoperative total global ROM was greater with ACH constructs and postoperative upper adjacent segment hypermobility was only seen with ACDF constructs, supporting consideration of hybrid surgery in patients with multilevel cervical pathology requiring at least a 1-level fusion.