L1-pelvic angle: a convenient measurement to attain optimal deformity correction

Area of Science:

• Spine surgery
• Orthopedics
• Biomechanical analysis

Background:

• Adult spinal deformity (ASD) significantly impacts patient quality of life.
• Sagittal alignment is crucial for spinal health and function.
• The L1-pelvic angle (L1PA) is an emerging parameter for assessing spinal alignment.

Purpose of the Study:

• To evaluate the association between the L1-pelvic angle (L1PA) and sagittal vertical axis (SVA) and T1-pelvic angle (T1PA).
• To assess the clinical impact of achieving an ideal L1PA in patients undergoing ASD surgery.

Main Methods:

• Retrospective cohort study of 145 patients undergoing ASD surgery (2013-2017).
• Ideal L1PA defined as (0.5 x Pelvic Incidence) - 21.
• Pearson correlation and regression analyses were used to assess L1PA associations and clinical outcomes, controlling for confounding factors.

Main Results:

• Preoperative and postoperative L1PA showed modest linear correlations with SVA and T1PA.
• Patients achieving ideal L1PA (±5°) had a significantly decreased risk of rod fracture/pseudarthrosis (OR=0.33).
• No association was found between ideal L1PA and patient-reported outcomes.

Conclusions:

• The L1-pelvic angle is correlated with key sagittal parameters (SVA, T1PA) in ASD patients.
• Achieving an ideal L1PA is associated with reduced mechanical complications, specifically rod fracture/pseudarthrosis.
• Further research is needed to fully elucidate the clinical significance of optimizing L1PA.