Reduced Preoperative Cervical Spine Flexion-Extension Range of Motion Is Associated With the Development of Upper Thoracic Proximal Junction Kyphosis in Adult Spinal Deformity Patients

Study Design: Retrospective, Single-center. Objective: To evaluate preoperative cervical range-of-motion via cervical flexion-extension radiographs and its relation to the development of PJK/PJF following ASD correction in patients with a UIV in the upper thoracic spine. Methods: Patients with an UIV between T1-T4, preoperative cervical flexion/extension radiographs and instrumented to the pelvis, and minimum 1yr follow-up were included. Cervical measurements included range-of-motion (ROM), flexion, extension and cervical SVA (cSVA). Patients were stratified into 3 groups: No-PJK, asymptomatic PJK (A-PJK) and symptomatic PJK including PJF (S-PJK/PJF). Results: 151 patients were included: Mean age 59.6 ± 8.0 yrs, BMI of 25.1 ± 4.5, 88.7% (n = 134) were female. PJK status: No PJK = 111 (73.5%) patients, A-PJK = 21 (13.9%), S-PJK/PJF = 19 (12.6%). S-PJK/PJF patients, however, were more likely to be diagnosed with osteopenia/osteoporosis(S-PJK/PJF: 68.4% vs A-PJK: 23.8% vs No PJK: 52.3%, P = 0.0138). S-PJK/PJF patients had significantly less cervical flexion (No PJK: 19.5 ± 14.2 vs A-PJK: 19.9 ± 10.9 vs S-PJK/PJF: 7.7 ± 11.9, P = 0.0029) and ROM than the other groups (No PJK: 52.8 ± 17.7 vs A-PJK: 53.1 ± 14.5 vs S-PJK/PJF: 39.2 ± 17.9, P = 0.0085). On multivariable models for the development of S-PJK/PJF, reduced baseline cervical flexion and ROM were independent risk factors yielding threshold values of 22.8° and 48.2°, respectively. Conclusion: Multivariable models for the development of S-PJK/PJF demonstrated that reduced baseline cervical ROM and flexion were independent risk factors yielding threshold values of 48.2° and 22.8°, respectively. All of S-PJK/PJF patients had preop flexion <22.8°. Flexion-extension radiographs provide a quick and easy option at a relatively low cost to offer additional information that may aid in surgical planning and shared decision making with the patient regarding potential outcomes.