[Cage assisted fusion operation of the spine]

Subsidence as of 12 months after single-level anterior cervical inter-body fusion. Is it related to clinical outcomes?

BACKGROUND

Subsidence is a frequent phenomenon in the interbody fusion process in patients with anterior cervical discectomy and fusion (ACDF). There is little evidence of whether subsidence in the cervical spine has any impact on clinical outcomes.

OBJECTIVES

The purpose of this study is to investigate the correlation of subsidence and clinical outcomes after ACDF and to consider reasons subsidence might not cause unfavorable clinical outcomes.

METHODS

A total of 158 consecutive patients who underwent single-level ACDF were included. The patients were divided into a subsidence group (S-group) and a no subsidence group (N-group), with subsidence defined as a decrease by ≥3 mm in total intervertebral height (TIH). We analyzed outcomes resulting from subsidence, particularly focusing on clinical outcomes and subsequent global and segmental kyphosis using a repeated measure analysis of variance (RM-ANOVA).

RESULTS

Subsidence occurred in 74 patients (46.8%) as of a 12-month follow-up. The S-group included 58.6% with a stand-alone cage for interbody fusion (p = 0.002). Clinical outcomes improved significantly over time (neck pain, RM-ANOVA: F(1.3, 205) = 125.1, p < 0.001; arm pain, RM-ANOVA: F(1.3, 203) = 290.8, p < 0.001). There was no significant difference in interaction with subsidence and clinical outcomes between the S- and N-group (neck pain, RM-ANOVA: F(2,153) = 1.04, p = 0.356, partial η(2) = 0.229; arm pain, RM-ANOVA: F(2,153) = 0.56, p = 0.571, partial η(2) = 0.142). Segmental angle increased in both groups over time and showed a statistically significant difference between the S- and N-groups (RM-ANOVA: F(3,143) = 6.148, p = 0.001, partial η(2) = 0.959). Although, global cervical angle decreased generally and displayed no statically significant difference between the S- and N-group (RM-ANOVA: F(3,119) = 2.361, p = 0.075, partial η(2) = 0.056).

CONCLUSIONS

Radiographic subsidence after ACDF occurred in 46.8% patients as of 12 months after the single-level ACDF. The lack of correlation between bad clinical outcome and radiographic subsidence may be due to segmental kyphosis, preserved posterior height, and maintaining the global cervical angle.

Is the radiographic subsidence of stand-alone cages associated with adverse clinical outcomes after cervical spine fusion? An observational cohort study with 2-year follow-up outcome scoring

Background

The stand-alone treatment of degenerative cervical spine pathologies is a proven method in clinical practice. However, its impact on subsidence, the resulting changes to the profile of the cervical spine and the possible influence of clinical results compared to treatment with additive plate osteosynthesis remain under discussion until present.

Methods

This study was designed as a retrospective observational cohort study to test the hypothesis that radiographic subsidence of cervical cages is not associated with adverse clinical outcomes. 33 cervical segments were treated surgically by ACDF with stand-alone cage in 17 patients (11 female, 6 male), mean age 56 years (33–82 years), and re-examined after eight and twenty-six months (mean) by means of radiology and score assessment (Medical Outcomes Study Short Form (MOS-SF 36), Oswestry Neck Disability Index (ONDI), painDETECT questionnaire and the visual analogue scale (VAS)).

Results

Subsidence was observed in 50.5% of segments (18/33) and 70.6% of patients (12/17). 36.3% of cases of subsidence (12/33) were observed after eight months during mean time of follow-up 1. After 26 months during mean time of follow-up 2, full radiographic fusion was seen in 100%. MOS-SF 36, ONDI and VAS did not show any significant difference between cases with and without subsidence in the two-sample t-test. Only in one type of scoring (painDETECT questionnaire) did a statistically significant difference in t-Test emerge between the two groups (p = 0.03; α = 0.05). However, preoperative painDETECT score differ significantly between patients with subsidence (13.3 falling to 12.6) and patients without subsidence (7.8 dropped to 6.3).

Conclusions

The radiological findings indicated 100% healing after stand-alone treatment with ACDF. Subsidence occurred in 50% of the segments treated. No impact on the clinical results was detected in the medium-term study period.