Natural history of spinopelvic alignment differs from symptomatic deformity of the spine

Abstract

Study Design: Cross-sectional study and systematic review of the literature. Objective: Describe the natural history of spinopelvic alignment parameters and their behavior in patients with degenerative spinal deformity. Summary of Background Data: Normal stance and gait requires congruence between the spine-sacrum and pelvis-lower extremities. This is determined by the pelvic incidence (PI), and 2 positional parameters, the pelvic tilt, and sacral slope (SS). The PI also affects lumbar lordosis (LL), a positional parameter. The final goal is to position the body's axis of gravity to minimize muscle activity and energy consumption. Methods: Two study cohorts were recruited: 32 healthy teenagers (Risser IV-V) and 54 adult patients with symptomatic spinal deformity. Standing radiographs were used to measure spinopelvic alignment and positional parameters (SS, PI, sacral-femoral distance [SFD], C7-plumbline [C7P], LL, and thoracic kyphosis). Data from comparable groups of asymptomatic individuals were obtained from the literature. Results: PI increases linearly with age (r = 0.8646) and is paralleled by increasing SFD (r = 0.8531) but not by SS. Patients with symptomatic deformity have higher SFD (42 ± 13.6 mm vs. 63.6 ± 21.6 mm; P < 0.001) and lower SS (42° ± 9.6° vs. 30.7° ± 13.6°; P < 0.001) but unchanged PI. The C7P also presents a linear increase throughout life (r = 0.8931), and is significantly increased in patients with symptomatic deformity (40 ± 37 mm vs. 70.3 ± 59.5 mm; P < 0.001). Conclusion: First, Gradual increase in PI is described throughout the lifespan that is paralleled by an increase in SFD, and is not by an increase in the SS. This represents a morphologic change of the pelvis. Second, Patients with symptomatic deformity of the spine present an increased C7P, thoracic hypokyphosis, reduced LL, and signs of pelvic retroversion (decreased LL and SS; increased SFD). © 2010, Lippincott Williams & Wilkins.