Comparison of coronal and sagittal pelvic-lower limb alignment after open wedge distal tibial tuberosity osteotomy and total knee arthroplasty using the EOS imaging system

Background The evaluation in pelvic-lower limb alignment compared to both open wedge distal tuberosity osteotomy (OWDTO) and total knee arthroplasty (TKA) using the EOS imaging system remain unclear. The primary objective of this study is to evaluate the pelvic–lower limb alignment after OWDTO and TKA using the EOS imaging system. The secondary objective is to investigate the relationship between coronal and sagittal alignment parameters. Patients and methods A total of 102 patients, including 51 who underwent OWDTO and 51 who underwent TKA, were included. Radiographic evaluations were performed using the EOS imaging system pre-operatively and at 12 months post-operatively. Coronal alignment parameters (medial proximal tibial angle (MPTA), coronal hip-knee-ankle angle (c-HKA), pelvic obliquity (PO), and sagittal alignment including sagittal HKA (s-HKA), pelvic incidence (PI), pelvic tilt (PT) and sacral slope (SS)) were assessed. Changes (Δ) and their correlations were analyzed. To account for potential confounding by age, sex, and Kellgren-Lawrence grade, partial correlation analysis adjusting for these variables was additionally performed. Results TKA resulted in significant improvements in coronal and sagittal alignment parameters except PT (p < 0.001). OWDTO showed significant changes in coronal parameters except PO (p < 0.001), with no significant changes observed in sagittal alignment. Δs-HKA was weakly and moderate negatively correlated with Δc-HKA, ΔSS and ΔPO (r = −0.20, −0.22 and −0.33, 95%CI: −0.38 to −0.01, −0.40 to −0.03 and −0.49 to −0.14, p = 0.04, 0.03 and 0.001). ΔSS was weakly negatively correlated with the change in ΔMPTA (r = −0.24, 95%CI: −0.44 to −0.05, p = 0.02). ΔPI was strongly positively correlated with the change in ΔPT (r = 0.77, 95%CI: 0.67 to 0.83, p < 0.001). After adjusting for age, sex, and K-L grade, the correlations between changes in coronal and sagittal alignment parameters remained largely consistent with the unadjusted results. Conclusion TKA resulted in greater improvements in both coronal and sagittal alignment parameters compared to OWDTO. Among sagittal parameters, the change in s-HKA showed the strongest, although modest, correlation with coronal alignment changes. The EOS imaging system may serve as a useful tool for simultaneously and reproducibly assessing coronal and sagittal alignment in patients undergoing OWDTO and TKA.