Impact of cage type on subsidence following anterior cervical discectomy and fusion: a retrospective study.

Study design: Retrospective cohort study.

Purpose: This study investigated the impact of cage material on subsidence and segmental lordosis following anterior cervical discectomy and fusion (ACDF), comparing polyetheretherketone (PEEK), titanium, and ceramic synthetic cages, as well as structural allografts.

Overview of literature: Subsidence following ACDF surgery can negatively impact clinical outcomes. Although extensively studied, the relationship between cage type and subsidence remains unclear due to conflicting data and inconsistent control for confounders, underscoring the need for multivariable analysis to determine material-specific effects.

Methods: Retrospective study of 120 patients (223 fusion levels) who underwent ACDF between 2016 and 2021. Spacer types included structural allografts, PEEK, titanium, and ceramic cages. Radiographic measurements of subsidence were obtained from immediate (≤8 weeks) and long-term (≥6 months) postoperative lateral cervical radiographs. Multivariable linear regression was used to assess the association between spacer type and subsidence, adjusting for patient demographics, surgical levels, smoking history, and osteopenia.

Results: The mean age of patients was 53.6±10.9 years and 41.7% were male; 47.5% had a smoking history and 20.8% had osteopenia. There were 38 one-level (31.7%), 61 two-level (50.8%), and 21 three-level fusions (17.5%). Spacer distribution included 62 structural allografts (51.7%), 27 PEEK (22.5%), 20 titanium (16.7%), and 11 ceramic (9.2%) cages. On multivariable analysis, PEEK cages were associated with significantly less anterior subsidence (β=-0.972, p <0.001) and posterior subsidence (β=-0.666, p=0.001) compared to allografts, and greater preservation of segmental lordosis (β=1.393, p=0.024). No significant differences in subsidence were found between titanium, ceramic, and allograft spacers.

Conclusions: PEEK cages showed reduced subsidence and better preservation of cervical lordosis compared to structural allografts, while titanium and ceramic cages did not differ significantly from structural allografts. These results suggest that PEEK cages may help minimize subsidence-related complications and improve outcomes.