Hip spine relationships: application to total hip arthroplasty

Area of Science:

• Orthopedics
• Biomechanics
• Radiology

Background:

• Lumbo-sacral orientation in the sagittal plane is critical for spinal and hip joint function.
• Trunk equilibrium affects acetabular orientation and hip range of motion.
• Patient-specific morphological parameters, like incidence angle, influence sagittal balance through postural adaptations.

Purpose of the Study:

• To elucidate the relationship between sacral slope variations and acetabular anteversion.
• To highlight the importance of understanding lumbosacral posture for total hip arthroplasty (THA) planning.
• To identify patients at risk of hip impingement due to altered lumbosacral alignment.

Main Methods:

• Analysis of lateral pelvic X-rays to assess sacral slope.
• Evaluation of postural adaptations including pelvic tilt, sacral slope, lumbar lordosis, acetabular sagittal tilt, and functional anteversion.
• Correlation of lumbosacral posture with functional acetabular anteversion.

Main Results:

• Sacral slope variations directly influence the functional anteversion of the acetabulum.
• Posterior pelvic version (decreased sacral slope) is associated with increased functional acetabular anteversion.
• Anterior pelvic version (increased sacral slope) is associated with decreased functional acetabular anteversion.

Conclusions:

• Lumbosacral posture, particularly sacral slope, is a key determinant of acetabular orientation.
• Accurate assessment of sacral slope on lateral pelvic X-rays is essential for surgical planning in total hip arthroplasty.
• Understanding these biomechanical relationships can help mitigate risks such as hip impingement.