Distal junctional kyphosis in adult cervical deformity patients: where does it occur?

Purpose To evaluate the impact of the lowest instrumented vertebra (LIV) on Distal Junctional kyphosis (DJK) incidence in adult cervical deformity (ACD) surgery. Methods Prospectively collected data from ACD patients undergoing posterior or anterior–posterior reconstruction at 13 US sites was reviewed up to 2-years postoperatively ( n = 140). Data was stratified into five groups by level of LIV: C6-C7, T1-T2, T3-Apex, Apex-T10, and T11-L2. DJK was defined as a kyphotic increase > 10° in Cobb angle from LIV to LIV-1. Analysis included DJK-free survival, covariate-controlled cox regression, and DJK incidence at 1-year follow-up. Results 25/27 cases of DJK developed within 1-year post-op. In patients with a minimum follow-up of 1-year ( n = 102), the incidence of DJK by level of LIV was: C6-7 (3/12, 25.00%), T1-T2 (3/29, 10.34%), T3-Apex (7/41, 17.07%), Apex-T10 (8/11, 72.73%), and T11-L2 (4/8, 50.00%) ( p