Defining the Role of the Lower Limbs in Compensating for Sagittal Malalignment

Area of Science:

• Spine surgery
• Orthopedics
• Biomechanical analysis

Background:

• Lower limb compensatory mechanisms are known responses to sagittal malalignment.
• Their specific role and impact on surgical planning remain unevaluated.

Purpose of the Study:

• To investigate the role of lower limb compensation in progressive sagittal malalignment.
• To determine if these mechanisms require separate consideration in surgical planning.

Main Methods:

• Retrospective review of full-body X-rays in patients over 20 years old.
• Analysis of sagittal vertical axis (SVA), pelvic tilt (PT), pelvic shift (P.shift), and knee angle (KA).
• Statistical analysis including ANOVA and hierarchical multiple regression to predict PT.

Main Results:

• Anteroposterior pelvic translation (P.shift) adjusted to maintain T9 alignment with the ankle across varying SVA.
• Pelvic tilt (PT) was significantly predicted by lower limb parameters (KA and P.shift), independent of PI-LL and SVA.
• Lower limb compensatory mechanisms showed a significant independent role in predicting PT.

Conclusions:

• Lower limb compensatory mechanisms are crucial in managing sagittal malalignment.
• These adaptations, including pelvic tilt and translation, allow for spinal alignment maintenance.
• The predictable nature of these mechanisms suggests they do not necessitate additional surgical planning considerations.