Preventing distal junctional kyphosis: Choosing a stable end for the lowest-instrumented vertebra is protective following adult cervical deformity surgery.

PURPOSE: This study investigates the role of a stable end vertebra (SEV) in surgical planning for adult cervical deformity (ACD). While the stable sagittal vertebra (SSV) is an established landmark in adolescent scoliosis, an equivalent concept in ACD is undefined. The objective was to assess whether selecting the lowest instrumented vertebra (LIV) at an SEV reduces the risk of distal junctional kyphosis (DJK) and related complications.

METHODS

A retrospective cohort study was conducted using a single-center, single-surgeon database of cervical deformity records. Patients with baseline and 2-year radiographic data were included. SEV was defined by three criteria: (1) LIV inclination angle ≥10°°, (2) LIV at or distal to the SSV, and (3) LIV Hounsfield unit >210. The primary outcome was DJK, defined as ≥≥10°° kyphosis between the superior endplate of the LIV and the inferior endplate of the vertebra two levels below. Multivariate regression adjusted for age and baseline deformity.

RESULTS

Among 120 patients (mean age, 58.5 ± 10 years; 60% female), 21 met the SEV criteria. DJK occurred in 20.6% overall but only 9.5% of SEV patients (vs. 30%, P = 0.009). SEV was associated with lower odds of DJK (odds ratio [OR], 0.28), distal junctional failure (OR, 0.03), and reoperation (OR, 0.016). SEV patients also had fewer radiographic and perioperative complications and were more likely to achieve neck disability index minimal clinically important difference (OR 2.8).

CONCLUSION

Using SEV to guide LIV selection significantly reduces mechanical and clinical complications and improves outcomes in ACD surgery. It should be prioritized in preoperative planning.