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Differences in anatomical parameters between the affected and unaffected hip in patients with bilateral cam-type
K C Geoffrey Ng1, Mario Lamontagne2, Paul E Beaulé3
1Department of Mechanical Engineering, University of Ottawa, Ottawa, ON, Canada.
Insights
Individuals with bilateral cam deformities experience unilateral symptoms due to variations in hip anatomy. Lower femoral neck-shaft and medial proximal femoral angles predict which hip is more likely to develop early femoroacetabular impingement symptoms.
Area of Science:
- Orthopedic surgery
- Radiology
- Sports medicine
Background:
- Femoroacetabular impingement (FAI) symptoms are often unilateral despite bilateral cam deformities.
- Additional anatomical factors likely contribute to symptom laterality in FAI.
Purpose of the Study:
- To compare anatomical hip joint parameters between symptomatic and asymptomatic hips in patients with bilateral cam deformities and unilateral symptoms.
Main Methods:
- Twenty participants with bilateral cam deformities and unilateral FAI symptoms underwent CT imaging.
- Measurements included alpha angles, femoral head-neck offset, neck-shaft angle, medial proximal femoral angle, femoral torsion, acetabular version, and center-edge angle.
- Clinical hip range of motion and physical examination signs were also assessed.
Main Results:
- Symptomatic hips exhibited limited range of motion compared to asymptomatic hips.
- Significantly lower femoral neck-shaft angles (mean 125° vs. 127°) and medial proximal femoral angles (mean 79° vs. 81°) were observed in symptomatic hips.
- No significant differences were found in cam deformity parameters, femoral torsion, acetabular version, or center-edge angle between hips.
Conclusions:
- Decreased femoral neck-shaft angle and medial proximal femoral angle can serve as diagnostic predictors for identifying hips at higher risk of early symptomatic FAI.
- These specific angular measurements may indicate a predisposition to developing symptoms even with bilateral cam deformities.
Background:
It is still unclear why many individuals with bilateral cam deformities demonstrate only unilateral symptoms of femoroacetabular impingement, thus symptoms may be attributed to additional anatomical parameters. The purpose was to examine patients with bilateral cam deformities, with unilateral symptoms, and compare anatomical hip joint parameters between their affected (symptomatic) hip and their contralateral, unaffected (asymptomatic) hip.
Methods:
Twenty participants (n=20) with unilateral symptoms, but bilateral cam deformities, underwent CT imaging to measure their affected and unaffected hip's: axial and radial alpha angles, femoral head-neck offset, femoral neck-shaft angle, medial proximal femoral angle, femoral torsion, acetabular version, center-edge angle; and a physical examination (hip flexion, straight-leg raise, internal rotation, external rotation) to ascertain clinical signs.
Findings:
The affected hips demonstrated limited motions during physical examination, compared with unaffected hips (effect size=0.550 to 0.955). The affected hips had significantly lower femoral neck-shaft angles (mean 125° (SD 3)) and lower medial proximal femoral angles (mean 79° (SD 4)), compared with the unaffected hips (mean 127° (SD 3), P=0.001, effect size=0.922; and mean 81° (SD 4), P=0.011, effect size=0.632; respectively). There were no differences in cam deformity parameters (axial and radial alpha angles, femoral head-neck offset), femoral torsion, acetabular version, and center-edge angle, between affected and unaffected hips.
Interpretation:
A decreased femoral neck-shaft angle or medial proximal femoral angle can be implemented as a diagnostic predictor, to determine which hip may be at a greater risk of developing early symptoms.
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