Pedicle Dysplasia in Proximal Thoracic Adolescent Idiopathic Scoliosis Curves: What are We Missing and What are its Possible Surgical Implications? An Observational Retrospective Study on 104 Patients

Abstract

Study Design Retrospective cohort study. Objectives To assess if pedicle dysplasia is present in proximal thoracic (PT), both structural and nonstructural, compared to main thoracic (MT) curves; and to assess if it is predictive of radiographic outcomes at minimum 2 years of follow-up. Methods A retrospective review of surgically-treated Adolescent Idiopathic Scoliosis (AIS) patients with Lenke 1-2-3-4 curves was performed. On preoperative CT-scan, at the apical vertebra, pedicle width on the concavity (PWc) and on the convexity (PWv) and Pedicle Dysplasia Index (PDI, defined as PWc/PWv) were measured. Preoperative and last follow-up (at least 2 years) x-rays were reviewed. Results 104 patients meeting the inclusion criteria were divided into Structural-PT (S-PT) and Nonstructural-PT (NS-PT) groups based on Lenke criteria. PWc ( P < .001). And PDI ( P < .001 for S-PT, P = .004 for NS-PT) were significantly smaller in the PT than in MT curves for both groups. PT-PWc significantly correlated with follow-up PT Cobb for both groups ( P < .001 and P = .015 respectively). PT-PDI significantly correlated with follow-up PT-Cobb ( P < .001), CA ( P < .040) and T1 tilt ( P < .002), only for NS-PT group. NS-PT patients with PWc PT <1 mm had higher RSHD ( P = .021) and T1 tilt ( P = .025) at follow-up. NS-PT patients with PDI PT <.3 had higher RSHD ( P < .001), CA ( P = .002) and T1 tilt ( P = .003) at follow-up. Conclusion S-PT and NS-PT curves show significant pedicle dysplasia on the concavity. Pedicle dysplasia significantly correlated with shoulder balance at follow-up, for NS-PT patterns. Patients with a PWc <1 mm or PDI <.30 are at particular risk of postoperative shoulder imbalance.