Surgical and Radiographic Outcomes in Cervical Deformity Patients with High T1 Slope and High C2 Slope (HTHC) Versus Low T1 Slope and High C2 Slope (LTHC)

Abstract

Study Design. Retrospective analysis of a prospective multicenter operative cervical deformity (CD) database. Objective. To determine whether T1 slope (T1S) and C2 slope (C2S) together identify distinct CD phenotypes: cervical-only versus global sagittal deformity, and to compare surgical invasiveness, radiographic correction, and patient-reported outcomes. Summary of Background Data. T1S and C2S mark cervical malalignment, and elevated T1S has been linked to global sagittal malalignment. Combining them may distinguish CD-only from global deformity on cervical imaging alone. Methods. Operative CD patients with ≥2 years follow-up and preoperative C2S >30° were stratified by T1S into low T1S–high C2S (LTHC; ≤30°) and high T1S–high C2S (HTHC; >30°). Multivariable regression assessed group effect on 2-year NDI change, adjusted for age, sex, baseline NDI, and posterior levels fused. NDI MCID was set a priori at ≥7 points per the ISSG threshold. Results. Ninety-two patients met criteria (31 LTHC, 61 HTHC). HTHC patients were older (64.7 vs. 60.0 years; P =0.035) with higher Charlson index ( P =0.022). Preoperatively, HTHC had greater thoracic kyphosis, TPA, cSVA, PI–LL mismatch, and C7 SVA (all P ≤0.010). HTHC underwent more extensive surgery: more posterior levels fused (10.3 vs. 6.7), more circumferential fusions (66.7% vs. 38.7%), and more caudal LIV (T7 vs. T3) (all P <0.05). At 2 years, HTHC retained higher TK and cSVA despite greater absolute correction. Baseline NDI was similar ( P =0.906), but 2-year NDI improvement was smaller in HTHC (−6.2 vs. −14.6 points; P =0.013), and fewer achieved MCID (45.9% vs. 71.0%; P =0.022). HTHC remained an independent predictor of smaller improvement (β=+7.4; P =0.020). Reoperation, DJK, and complication rates did not differ. Conclusions. Among CD patients with elevated C2S, additional elevated T1S identifies a global-deformity phenotype requiring more invasive correction and showing smaller 2-year patient-reported improvement despite comparable complications. T1S and C2S, measurable on cervical imaging alone, screen for which CD patients warrant full-spine imaging. Level of Evidence. III (retrospective analysis of prospectively collected multicenter data).