The Impact of Positive Sagittal Balance in Adult Spinal Deformity

• a, b, d, e - Medtronic Sofamor Danek

Introduction: In a prior study of 298 adults with spinal deformity, positive sagittal balance was identified as the radiographic parameter most highly correlated with adverse health status outcomes. While consistent with the perception that clinical symptoms occur with sagittal imbalance secondary to flat back or severe thoracolumbar kyphosis, the study suggested that even limited positive sagittal balance was relevant.

Purpose: The purpose of the present study is to investigate adult deformity patients with positive sagittal balance to define parameters, such as etiology, magnitude or region of kyphosis, which might differentially predict clinical symptoms.

Methods: This is a prospective multi-center study of 352 patients (289 female, 63 male) with positive sagittal balance from 725 consecutive patients with adult spinal deformity enrolled in the database. The SF-12, SRS-29 and Oswestry Disability Index (ODI) were determined. Sagittal Cobb angles from T2-T5 (high thoracic), T5-T12 (thoracic), T12-L2 (thoracolumbar), and T12- Sacrum (lumbar) were measured. For each region, patients were categorized as lordotic (> 1 s.d. below the mean sagittal Cobb), normal (within 1 s.d. of the mean sagittal Cobb angle), or kyphotic (> 1 s.d. above the mean sagittal Cobb). Statistical software was used to band patients into 10 relatively equal groups of increasing positive C7 plumb line measurement. Patient scores on the SF-12, the SRS-29 and ODI were analyzed to determine the relationship between type, location, or magnitude of deformity with overall health status, pain, and function. Other variables (coronal imbalance, previous surgery, smoking, age, and BMI) potentially impacting health status were assessed.

Results: S: In the high thoracic region, patients classified as kyphotic had significantly less pain (SRS-29) and disability (SRS-29 and ODI) than patients in the normal or lordotic range (p<0 .05). In the lumbar region, patients classified as kyphotic had significantly more disability (SRS-29 and ODI) than in normal or lordotic range (p<0.05). There was clear evidence of increased pain decreased function positive sagittal balance increased. All measures health status (SF-12, SRS-29, showed poorer scores C7 plumb line Evaluation potentially confounding variables revealed that ODI varied with smoking BMI, but not by age, coronal balance, surgical history. None these five factors interacted to influence status. The study able detect a significant relationship between area greatest kyphosis clearest trend observed on ODI, where distal location maximal kyphosis, greater degree

Conclusions: This study demonstrates that even mildly positive sagittal balance is detrimental, but that the severity of symptoms increases in a linear fashion with progressive sagittal imbalance. The results also show that patients with the greatest relative kyphosis in the upper thoracic region did well, but that kyphosis was poorly tolerated in the lumbar spine. These findings emphasize the importance of thoroughly assessing sagittal balance in the treatment of adults with spinal deformity.

• If noted the author indicates something of value received. The codes are identified as: a-research or institutional support; b-miscellaneous funding; c-stock or stock options; d-royalties; e-other financial or material support including consulting.