Personalized Realignment in Adult Cervical Deformity Surgery: Consideration of Upper Cervical Region and Morphology in the Cervical Lordosis Distribution Index

Introduction: The cervical lordosis distribution index tailored correction to patient. However, impact of morphologic differences and upper cervical region has not been characterized.

Methods: Cervical deformity patients with up to 2 yr data included. Caudal (CaLDI) and Cranial lordosis distribution index (CrLDI) developed by dividing each arch by total segment (C0-T2) and multiplying by 100. Conditional inference tree analysis developed thresholds (Cranial 70-100, Caudal -10-30). Patients stratified by Ames classification then assessed against thresholds. Those meeting thresholds with upper cervical compensation (defined by C0‑C2 angle, C0 slope, McGregor’s Slope [MGS]) compared against without compensation. Good clinical outcome (GCO) defined by no DJF and meeting Virk et al Criteria: [Meeting 2 of 3: 1. NDI>20, 2. mJOA ≥14, 3. NRS-Neck≤5]. Multivariate regression analysis assessed differences with classification and upper cervical region, controlling for T1 Slope.

Results: 82 met inclusion (Age: 61.4 yrs, BMI: 29.1kg/m2, 64%F, CCI: 1.06). Mean CrLDI: 53±138, mean CaLDI: 47±138. Those meeting cranial threshold had 93% more likely to be classified into primary cervical deformity (OR: .07, [1.15,1.59], p<.05) followed by cervico-thoracic (OR: .29, [1.08, 1.41], p=.057). Caudal threshold were 51% more likely to be classified as cervical (OR:.49, [.22,.53], p>.05) and 39% more likely as cervico-thoracic (OR: .61, [.32, .68], p>.05). Meeting CrLDI threshold significantly predicted a decrease in C0-C2 angle (OR: -3.7 [1.80, 2.70], p=.009) and C0 slope (OR:-6.1 [1.19, 1.72], p<.001). CaLDI threshold had a decrease in C0-C2 angle (OR: -1.5, [1.12,2.33], p=.03) and C0 slope (OR: -4.7, [.85,1.23],p=.045). Compensation with CrLDI thresholds had lower DJK (10% vs. 23%, p=.03) and higher GCO (68% vs. 54%, p=.046). CaLDI generated similar results with lower DJK (11% vs. 29%, p=.042) and higher GCO (72% vs. 48%, p=.048). Overall, CrLDI threshold with compensation had higher odds of GCO compared to CaLDI (2.71 vs. 2.23, p<.05).

Conclusion : Despite morphology differences, upper cervical region functions as a reserve in all deformity types. Consideration of regional and global factors allows for a comprehensive assessment and individualization of realignment surgery.