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Multicenter Study
. 2025 Jun 2;97(4):901-907.
doi: 10.1227/neu.0000000000003538.

Quantifying the Importance of Upper Cervical Extension Reserve in Adult Cervical Deformity Surgery and Its Impact on Baseline Presentation and Outcomes

Peter G Passias  1 , Jamshaid M Mir  1 , Andrew J Schoenfeld  2 , Anthony Yung  1 , Justin S Smith  3 , Virginie Lafage  4 , Renaud Lafage  4 , Bassel Diebo  5 , Alan H Daniels  5 , Breton G Line  6 , Robert K Eastlack  7 , Gregory M Mundis  7 , Khaled M Kebaish  8 , Jeffrey P Mullin  9 , Richard G Fessler  10 , Praveen V Mummaneni  11 , Dean Chou  11 , David Kojo Hamilton  12 , Sang Hun Lee  8 , Alex Soroceanu  13 , Justin K Scheer  11 , Themistocles Protopsaltis  14 , Han Jo Kim  15 , Thomas J Buell  12 , Richard A Hostin Jr  16 , Munish C Gupta  17 , Eric O Klineberg  18 , K Daniel Riew  19 , Douglas C Burton  20 , Frank J Schwab  4 , Shay Bess  6 , Christopher I Shaffrey  1 , Christopher P Ames  11 ; International Spine Study Group
Affiliations
Multicenter Study

Quantifying the Importance of Upper Cervical Extension Reserve in Adult Cervical Deformity Surgery and Its Impact on Baseline Presentation and Outcomes

Peter G Passias et al. Neurosurgery. .

Abstract

Background and objectives: The concept of upper cervical ( C0-C2) extension reserve (ER) capacity, ER relaxation, and their impact on outcomes following surgical correction of adult cervical deformity (ACD) has not been extensively studied. We aimed to evaluate the impact of upper cervical ER on postoperative disability and outcomes.

Methods: Patients with ACD, from a retrospective cohort study of a prospectively collected multicenter database, undergoing subaxial cervical fusion with 2-year (2Y) follow-up data were included. ER was defined as: ΔC0-C2 sagittal Cobb angle between neutral and extension. Relaxation of ER was defined as the ER mean in those that met all ideal thresholds in radiographic parameters for Passias et al CD modifiers. We used multivariable logistic regression to adjust for confounding, with conditional inference tree approaches used to determine thresholds that affect postoperative ER resolution on patient-reported outcomes.

Results: A total of 108 patients with ACD met inclusion. Preoperative C0-C2 ER was 8.7° ± 9.0°, and at last follow-up was 10.3° ± 11.1°. Preoperatively 29% of the cohort had adequate ER, whereas 60% had improved ER postoperatively, with 50% achieving adequate ER by 2Y. Lower ER correlated with greater CD ( P < .05). Preoperatively, greater ER had lower Neck Disability Index ( P < .001). Controlled analysis found improved ER to have a greater likelihood of achieving Neck Disability Index minimum clinically important difference (odds ratio 6.94, [1.378-34.961], P = .019). In those with inadequate ER at baseline, the preoperative C2-C7 of < -18° and T1 slope-cervical Lordosis mismatch of >59° for T1 slope-cervical Lordosis mismatch was predictive of ER resolution. In those with preoperative C2-C7 >-18°, a T1PA of >13° was predictive of postoperative return of ER (all P < .05). Surgical correction of C2-C7 by > 16° from baseline was found to be predictive of ER return.

Conclusion: Increased preoperative use of the C0-C2 ER in CD was associated with worse baseline regional and global alignment and adversely affected health-related measures. Most of the patients had ER relaxation postoperatively. In those who didn't, however, there was a decreased likelihood of achieving satisfactory outcomes.

Keywords: ACD; Adult cervical deformity; Complications; High-risk; Optimization; Outcomes; Upper cervical extension reserve.

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References

    1. Smith JS, Line B, Bess S, et al. The health impact of adult cervical deformity in patients presenting for surgical treatment: comparison to United States population norms and chronic disease states based on the EuroQuol-5 dimensions questionnaire. Neurosurgery. 2017;80(5):716-725.
    1. Tretiakov PS, Budis E, Dave P, et al. Does the presence of cervical deformity in patients with baseline mild myelopathy increase operative urgency in adult cervical spinal surgery? A retrospective analysis. Neurosurg Focus. 2023;55(3):e9.
    1. Smith JS, Kelly MP, Buell TJ, et al. Adult cervical deformity patients have higher baseline frailty, disability, and comorbidities compared with complex adult thoracolumbar deformity patients: a comparative cohort study of 616 patients. Glob Spine J. 2025;15(2):846-857.
    1. Passias PG, Bortz C, Horn S, et al. Drivers of cervical deformity have a strong influence on achieving optimal radiographic and clinical outcomes at 1 year after cervical deformity surgery. World Neurosurg. 2018;112:e61-e68.
    1. Passias PG, Moattari K, Pierce KE, et al. Performance of the modified adult spinal deformity frailty index in preoperative risk assessment. Spine. 2022;47(20):1463-1469.

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