The Conceptualization and Derivation of the Cervical Lordosis Distribution Index.

Summary Of Background Data: 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.

Objective: Tailor correction of cervical deformity by incorporating the cervical apex into a distribution index(CLDI) to maximize clinical outcomes while lowering rates of junctional failure.

Study Design/setting: Retrospective cohort.

Methods: CD patients with complete 2Y data were included. Optimal outcome is defined by no DJF, and meeting Virk et al Good Clinical Outcome Criteria:[Meeting 2 of 3: 1)an NDI<20 or meeting MCID, 2)mJOA>=14, 3)an NRS-Neck<=5 or improved by 2 or more points]. C2-T2 lordosis was divided into cranial (C2 to apex) and caudal (apex to T2) arches postoperatively. A cervical lordosis distribution index(CLDI) was developed by dividing the cranial lordotic arch(C2 to apex) by the total segment(C2-T2) and multiplying by 100. Cross-tabulations developed categories for CLDI producing the highest chi-square values for achieving Optimal Outcome at two years and outcomes were assessed by multivariable analysis controlling for significant confounders.

Results: 84 CD patients were included. Cervical apex distribution postoperatively was: 1% C3, 42% C4, 30% C5, 27% C6. Mean cervical LDI was 117±138. Mean cranial lordosis was 23.2±12.5°. Using cross-tabulations, a CLDI between 70 and 90 was defined as 'Aligned'. Chi-square test revealed significant differences among CLDI categories for DJK, DJF, Good Clinical Outcome, and Optimal Outcome(all P<0.05). Patients aligned in CLDI were less likely to develop DJK(OR: 0.1, [0.01-0.88]), more like to achieve GCO (OR: 3.9, [1.2-13.2]) and Optimal Outcome (OR: 7.9, [2.1-29.3] at two years. Patients aligned in CLDI developed DJF at a rate of 0%.

Conclusion: The cervical lordosis distribution index, classified through the 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.

Level Of Evidence: III.