Summary: This study identifies critical preoperative sagittal parameters that may lead to failures of short fusions (T10‐pelvis), and encourages extending fusions proximally at the index surgery.
Introduction: Global sagittal balance is critical to successful surgical reconstruction in adult idiopathic scoliosis. Selection of the upper instrumented veterbrae is based on several preoperative parameters. Our cohort analysis of long (T2‐pelvis) and short (T10‐pelvis) fusion constructs have identified several risk factors for loss of sagittal alignment and construct failure.
Methods: 57 pts with adult thoracolumbar and lumbar idiopathic scoliosis treated with PSF. All pts underwent ALIF at L4‐S1, and PSF to the pelvis. Preand postoperative radiographs were analyzed for: coronal curve magnitude, coronal alignment, cervical lordosis, C2 and C7 sagittal vertical axis (SVA), cervico‐thoracic, thoracic and thoracolumbar kyphosis. We also analyzed proximal junctional kyphosis (PJK), loss of sagittal balance, revision surgery, and previous history of ACDF.
Results: 47 females and 10 males with avg age 61 yrs (44‐73), avg f/u 38.7 mos. 21 pts had T2‐pelvis and 26 pts T10‐pelvis with avg 9.6 levels fused. At final f/u, 40 pts maintained sagittal balance (avg. C7 SVA: −2.0cm, PJK: −4.3°). Of these, 21/21 T2‐pelvis maintained sagittal balance, while 7/28 T10‐pelvis had progressive loss of sagittal alignment (avg. C7 SVA: 4.2cm, PJK: −9°). The failed group revealed an increase in preoperative: thoracic kyphosis (T2‐T12: 50° v. 32°), cervical kyphosis (C2 SVA: +2.0 v. +1.46cm), cervicothoracic (T1 tilt: 28.7° v. 15.8°) and thoracolumbar kyphosis (‐6.75° vs. 2.8°) compared to the balanced group (p<0.05). History of ACDF was also found to be significantly higher in failure patients (38% vs. 0%, p<0.05).
Conclusion: Our study identifies that C2 SVA >2 cm, T1 tilt >29°, thoracic kyphosis >50° and thoracolumbar kyphosis >7° are key preoperative risk factors that may predict sagittal balance failures. We theorize that patients with these preoperative sagittal parameters have constant cantilevering forces on short fusion constructs leading to failure. In these patients, our study suggests selecting a long fusion (T2‐pelvis).
Significance: Previous studies have shown that loss of global sagittal balance postoperatively produces poor clinical outcomes. We compared scoliosis patients with successful and failed fusions in attempts to identify preoperative radiographic risk factors.