BACKGROUND: Sagittal plane malalignment has been established as the main radiographic driver of disability in adult spinal deformity (ASD).
OBJECTIVE: To evaluate the amount of sagittal correction needed for a patient to perceive improvement (minimal clinically important difference, MCID) in health-related quality of life (HRQOL) scores.
METHODS: This was a multicenter, retrospective analysis of prospectively consecutively enrolled ASD patients. Inclusion criterion was a sagittal vertical axis (SVA) >80 mm. Demographic, radiographic, and HRQOL preoperative and 2-year postsurgery data were collected. Surgical treatment was categorized based on SVA correction: <60 mm, 60 mm to 120 mm, and >120 mm. Changes in parameters were analyzed using paired t test, 1-way analysis of variance, and χ2 test.
RESULTS: Seventy-six patients (preoperative SVA = 140 mm) were analyzed; each subgroup revealed significant HRQOL improvements following surgery. Compared with the <60 mm correction group, the likelihood of reaching MCID was significantly improved for the >120 mm group (Oswestry Disability Index) but not for the 60 mm to 120 mm group. A significantly greater likelihood of reaching MCID thresholds was observed for corrections above 66% of preoperative SVA.
CONCLUSION: Best HRQOL outcomes for ASD patients with severe sagittal plane deformity were obtained with a correction >120 mm for SVA and at least 66% of correction. Although lesser amounts of SVA correction yielded clinical improvement, the rate of MCID threshold improvement was not significantly different for mild or modest corrections. These results underline the need for complete sagittal plane deformity correction if high rates of HRQOL benefit are sought for patients with marked sagittal plane deformity.
ABBREVIATIONS: ASD, adult spinal deformity
HRQOL, health-related quality of life
LL, lumbar lordosis
MCID, minimal clinically important difference
ODI, Oswestry Disability Index
PCS, Physical Component Score
PT, pelvic tilt
SCB, substantial clinical benefit
SRS, Scoliosis Research Society
SVA, sagittal vertical axis
TK, thoracic kyphosis