Orthopaedic Resident Columbia University Medical Center New York City, New York, United States
Introduction: Optimizing coronal alignment is an important goal for adult spinal deformity(ASD) surgery. Recently, the horizontal distance from C7 to the Central Sacral Pelvic Line(CSPL= line bisecting the sacrum and perpendicular to the line touching the acetabular sourcils) measured on intraoperative prone radiographs was introduced as an accurate target for postoperative coronal alignment, particularly for patients without leg length discrepancy. However, the clinical utility of this intraoperative measure in predicting patient reported outcomes and postoperative lower extremity(LE) compensatory changes have not yet been described.
Methods: ASD patients with minimum 6 level fusion(including pelvic fixation), preoperative coronal malalignment(CVA≥3cm), no LLD( < 1cm), and minimum 2 year follow up were reviewed. Patient demographics, comorbidities, baseline PROs, surgical factors, and radiographic factors (both coronal and sagittal) were collected. The intraoperative distance (cm) from C7 to CSPL was measured for each patient. The outcome of interests included the minimum clinically important difference(MCID) for ODI/SRS and postoperative LE changes(pelvic obliquity[PO]>1deg, asymmetric knee bending, LE mechanical axis difference(LMAD)>2deg) at 2 years postop. Bivariate and multivariate logistic regression were performed to determine the independent factors for the outcomes of interest.
Results: 76 patients (age 58.3±13.7, female 77.6%, levels fused 14.1±3.9) with preop/2yr CVA 5.0±1.9/2.1±1.8cm and SVA 5.7±6.0/3.0±3.9cm were reviewed. Preop/2yr ODI 39.3±17.5/18±17, SRS function 3.2±0.9/3.8±0.8, SRS pain 2.7±.9/3.8±1.1, and SRS appearance 2.4±0.8/4.0±0.9. The rate of preop LE changes was 57.9% (PO=2.4⁰, LMAD=4.2⁰, and 27% had asymmetric knee bending). The rate of 2yr LE changes was 26.3% (pelvic obliquity PO=2.0⁰, LMAD=3.9⁰, and 12.6% had asymmetric knee bending). The mean error between intraop C7-iCSPL and 2yr CVA was 0.5±1.3cm. Worse C7-iCSPL was associated with higher risk for LE changes (2.9 vs. 1.9cm, p=0.04) and remained significant in the multivariate (OR 3.0, p< 0.01). Lower C7-iCSPL was associated with improved 2 year ODI MCID (1.8 vs. 3.2cm, p=0.03), but did not remain significant in the multivariate. Instead, patients with LE changes was the strongest independent predictor for worse ODI MCID (OR 15.9, p< 0.01).
Conclusion : For ASD patients with coronal malalignment, optimizing intraoperative coronal correction may reduce iatrogenic LE compensation, which was found to significantly contribute to worse patient reported outcomes at 2 years.
