Posterior Pelvic Tilt Allows for Increased Hip Motion, While Anterior Pelvic Tilt Decreases Joint Stress: A Systematic Review of Biomechanical and Motion Analyses.

Abstract

Purpose: The purpose of this systematic review was to evaluate the effect of pelvic tilt on hip joint contact forces and range of motion in patients with femoroacetabular impingement (FAI) and acetabular dysplasia.

Methods: A literature review querying the U.S. National Library of Medicine (PubMed/MEDLINE), EMBASE, SCOPUS, and Cochrane Databases using the key words ("Femoroacetabular Impingement" OR "Hip Dysplasia") AND ((((("Pelvic Tilt") OR (Joint Contact) OR (Kinetics) OR ("Pelvic Incidence") OR (Lumbar Lordosis)))). 14 studies were included in the review with methodological quality evaluated through the Methodological Index for Non-Randomized Studies (MINORS) and Risk of Bias in Non-Randomized Studies- of Interventions (ROBINS-I) criteria.

Results: There were 474 total patients (577 hips) in the 14 studies reviewed. Two studies focused on hip joint contact forces and femoral head coverage in acetabular dysplasia. These found that posterior pelvic tilt was associated with decreased hip joint contact area (range: 490-581 mm² vs 919-1094 mm²), increased joint contact pressure (range: 3.9-7.3 mPa vs 1.8-3.5 mPa), and decreased femoral head coverage (range: 30.2-43.4% vs 38.9-50.3%) in dysplastic subjects compared to control populations. Twelve studies evaluated the range of hip motion in FAI populations undergoing different functional maneuvers. Posterior pelvic tilt in FAI patients was found to increase hip range of motion to impingement on supine testing and biomechanical modeling (Internal rotation in flexion range: -6.5° to 15.5° with anterior tilt, 12.9° to 31.4° with posterior tilt). With dynamic maneuvers, FAI patients had decreased pelvic mobility (range: 7.2°-14.7° vs 12.7°-24.2°) and decreased posterior pelvic tilt (range: 3.4°-15.9° vs 9.8°-21.1°) compared to patients without FAI.

Conclusions: Hip joint stress is increased with posterior pelvic tilt in dysplastic patients, while increasing posterior pelvic tilt increases hip range of motion to impingement in patients with FAI. During weight-bearing exercises, the ability for FAI patients to posteriorly tilt the pelvis is restricted compared to a control population.

Clinical relevance: Spinopelvic kinematics and alignment affect composite hip motion and play a critical role in bipedal locomotion. The influence of spinopelvic parameters on treatment outcomes for acetabular dysplasia and FAI is controversial and currently limited by an imperfect understanding of the hip-spine relationship as it relates to nonarthritic hip disease. The present systematic review provides a summary of the results of biomechanical studies investigating pelvic tilt in this population.