So Close yet So Far: The impact of undercorrection of cervical sagittal alignment during adult cervical deformity surgery − An Incremental correction analysis

Abstract

BackgroundTo compare degrees of cSVA correction and to theorize possible minimum and maximum thresholds of cSVA correction for patients to benefit clinically. Methods657 operative ACD patients in a retrospective cohort study of a prospectively enrolled database with complete baseline and two year radiographic and HRQL data were examined. Patients were grouped into an optimally corrected cohort (OC; postop cSVA ≤ 4 cm) and an undercorrected cohort (UC; postop cSVA > 4 cm) based on postoperative radiographs. Results265 patients met inclusion criteria (mean age 58.2 ± 11.4 years, BMI 28.9 ± 7.5, CCI 0.9 ± 1.3). 11.2 % of patients were UC, while 88.8 % of patients were OC. UC cohort experienced a significantly greater occurrence of radiographic complications (47.8 % v. 27.6 %, p = 0.046). UC also demonstrated a significantly greater rate of severe 6 M DJK (p < 0.001) and 1Y DJK (26.1 % v. 2.7 %, p < 0.001). In terms of HRQLs, the OC cohort demonstrated significantly greater 2Y EQ5D-Health values (76.9 v. 46.7, p = 0.012). Being UC was a significant predictor of moderate-high 1Y mJOA score (OR 3.0, CI 95 % 1.2–7.3, p = 0.015) Still, in terms of CIT, the threshold for DJF risk increased significantly (p = 0.026) when the cSVA were surgically corrected greater than 5 cm. ConclusionUndercorrection of cSVA yielded worse clinical outcomes and posed a significant risk for radiographic complications. Although undercorrection does not seem to be efficacious, surgical correction beyond certain thresholds should still be respected as there is a risk for DJK on either end of the spectrum.