Summary
Hip internal rotation causes motion of the contra-lateral Sacroiliac Joint with realtively more motion with a decreased head neck offset
Data
Background
A causative link between femoroacetabular impingement and increased motion of the other pelvic joints could give one possible explanation for the clinical observation that subsets of people with labral injury secondary to femoroacetabular impingement also have other pelvic pain generators.
Hypothesis/Purpose
The purpose of this study was to investigate if internal rotation of the hip past the point of bony contact of the femoral neck and acetabulum will cause increasing motion at the sacroiliac joints.
Study Design
Controlled Laboratory Study.
Methods
Twelve hips from six fresh-frozen human cadaveric pelvises were used to simulate Cam-type femoroacetabular impingement. The hips were held in a custom jig and maximally internally rotated at 90 degrees of flexion and neutral adduction. Three-dimensional motion of the sacroiliac joints were measured by a motion tracking system for three stages: intact, small cam, and large cam. Load-displacement plots were generated between the internal rotational torque applied to the hip and the responding motion in three anatomical planes of the sacroiliac joints.
Results
As the hip was internally rotated, the motion at the contra-lateral sacroiliac joint increased proportionally with the degrees of the rotation as well as the applied torque measured at the distal femur for all three states. The primary rotation of the contra-lateral sacroiliac joint was in the transverse plane and on average accounted for 40 to 50% of the total rotation. At the torque level of 10.0 Nm, the mean transverse rotation in degrees was 0.28±0.22 for the intact, 0.45±0.26 and 0.38±0.28 for the small and large Cams.
Conclusions
The dynamic impingement type of femoroacetabular impingement as caused by contact of the proximal femur with the acetabulum causes rotational motion at the contra-lateral sacroiliac joint.
Clinical Relevance
Repetitive loading of the sacroiliac joint by femoroacetabular impingement could potentially lead to anatomic injury patterns, and sacroiliac joint pain.
Article info
Identification
Copyright
© 2012 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.
