The Conceptualization and Derivation of the Cervical Lordosis Distribution Index

Introduction: Yilgor et al developed the lumbar Lordosis Distribution Index to individualize the pelvic mismatch to each patient’s pelvic incidence. The cervical lordosis distribution in relation to its apex has not been characterized.

Methods: CD patients with up to 2Y data included. Good clinical outcome (GCO) is defined by no DJF (DJK >15.3°), and meeting Virk et al Criteria: [2 of 3: 1) an NDI>20 or meeting MCID, 2) mJOA >=14), 3) NRS-Neck<=5 or improved by 2 or more]. Patients stratified by cervical lordosis into a cranial (C2 to apex) and caudal (apex to T2) arches postoperatively [up to three months (3M)]. A caudal (CaLDI) and cranial lordosis distribution index (CrLDI) was developed by dividing each arch by the total segment (C2-T2) and multiplying by 100. Conditional inference tree (CIT) analysis developed thresholds for each CLDI and thresholds were assessed with outcome measures.

Results: 81 CD patients included. Distribution of cervical apex at 3M was 1% C3, 42% C4, 30% C5, 27% C6. Mean cranial LDI was 53±261, and mean caudal LDI was 47±261. Mean cranial lordosis was 23±12.3°, caudal lordosis 2.4±12.4°. Caudal lordosis showed a correlation with 3M T4-T12 (r=-.242). Using CIT analysis to derive thresholds for achieving GCO, Cranial LDI thresholds were 70 to 100, while Caudal LDI were -10 to 30. The CrLDI thresholds generated lower rates of DJK (13% vs. 34%, p=.043) and higher rates of meeting GCO (78% vs. 55%, p=.046). CaLDI also generated lower rates of DJK (14% vs. 37%, p=.028) and higher rates of GCO (76% vs. 53%, p=.048), and trended towards significance for DJF (3% vs 16%, p=0.080). When assessing each CLDI in binary logistic regression analysis, the Caudal LDI had slightly higher OR for meeting GCO (3.4 vs. 3.0).

Conclusion : The cervical lordosis distribution index, whether classifying through the caudal or cranial segment, takes each unique cervical apex into account and tailors correction to the patient in order to better achieve good clinical outcomes and minimize catastrophic complications following cervical deformity surgery.