Postoperative Curvature Loss in Three-Level Anterior Cervical Discectomy and Fusion With Zero-Profile Device

Cervical curvature loss is a frequent complication following 3-level anterior cervical discectomy and fusion (ACDF) using a Zero-Profile device. Consequently, the capacity of this device to maintain cervical sagittal alignment in 3-level ACDF remains highly controversial. This study aimed to identify potential predictors for postoperative curvature loss (PCL) and evaluate its impact on clinical outcomes.

A total of 113 patients who underwent ACDF for 3-level cervical degenerative disc disease (CDDD) between January 2021 and December 2023 were retrospectively reviewed. Demographic data, radiological parameters, and clinical outcomes were analyzed. Radiographic measures included cervical curvature, T1 slope, C2-7 sagittal vertical axis, and titanium plate and endplate (TPE) distance. Clinical outcomes were assessed using the Visual Analog Scale (VAS), Neck Disability Index (NDI), and Japanese Orthopaedic Association (JOA) scores. Statistical analyses were performed using paired and independent t-tests, as well as Pearson correlation coefficients.

The average curvature loss was 6.82° from 1 week postoperatively to the final follow-up (p < 0.001). However, the final curvature (11.65°) was maintained, representing a 4.33° improvement compared to preoperative values. Significant correlations were observed between PCL and preoperative curvature (r = -0.368, p = 0.013), preoperative T1 slope (r = -0.546, p < 0.001), ∆T1 slope (r = 0.443, p = 0.002), and ∆TPE distance (r = 0.417, p = 0.004). PCL did not correlate with Japanese Orthopaedic Association (JOA) scores or arm VAS scores at the final follow-up. Nevertheless, patients with a PCL ≥ 6° exhibited significantly higher neck VAS (p = 0.028) and NDI scores (p = 0.041).

Although contiguous 3-level ACDF with a Zero-Profile device may result in PCL, it preserves an improved cervical lordosis compared to the preoperative baseline. Low preoperative curvature and a low preoperative T1 slope are potentially predictive factors for PCL. Postoperative changes in TPE distance and T1 slope are significantly associated with PCL, suggesting a potential biomechanical link that requires direct validation. Furthermore, PCL may lead to higher neck VAS and NDI scores. Consequently, the Zero-Profile device may require careful consideration in 3-level CDDD patients presenting with low preoperative curvature and a low T1 slope. Importantly, the 6° PCL threshold identified is preliminary and requires prospective validation before clinical application.