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Intracapsular pressure in congenital dislocation of the hip
1Department of Orthopedics, University Hospital, Lund, Sweden.
Insights
Certain hip positions used for treating congenital hip dislocation (CDH) in infants create high intracapsular pressure. This pressure may lead to avascular necrosis and growth disturbances in affected children.
Area of Science:
- Pediatric Orthopedics
- Developmental Biology
Background:
- Congenital dislocation of the hip (CDH) and acetabular dysplasia can lead to hip joint instability in infants.
- Avascular epiphyseal necrosis and growth disturbances are known complications in treated CDH patients.
Purpose of the Study:
- To measure intracapsular hip joint pressure in infants with CDH or hip instability.
- To investigate the relationship between joint positioning and intracapsular pressure.
- To determine if specific rotational positions contribute to complications like avascular necrosis.
Main Methods:
- Intracapsular hip joint pressure was measured in six infants (average age 4.3 months) with diagnosed CDH or hip instability.
- Pressure was recorded in extension/neutral rotation, frog-leg position, and 20 degrees flexion with varying degrees of abduction and inward rotation.
Main Results:
- Mean intracapsular pressure was 8.9 mm Hg in extension/neutral rotation.
- Pressure increased significantly to 74.6 mm Hg in the frog-leg position.
- Positions involving 20 degrees flexion with inward rotation resulted in mean pressures of 104 mm Hg and 160 mm Hg.
Conclusions:
- Specific rotational and flexion positions commonly used to stabilize hips in infants with CDH or instability generate high intracapsular pressures.
- These elevated pressures may occlude epiphyseal-physeal vessels.
- This occlusion is a potential cause of avascular epiphyseal necrosis and subsequent growth disturbances observed in these patients.
Abstract:
Intracapsular hip joint pressure was measured in six infants with congenital dislocation of the hip (CDH) or acetabular dysplasia with hip joint instability diagnosed at an average of 4.3 months of age (range: 3-8 months). In the extension and neutral rotation position, the mean pressure was 8.9 mm Hg. After reduction, obtaining stability with the hip joints in the "frog-leg" position (i.e., maximum flexion around the axis of the neck of the femur), the mean pressure was 74.6 mm Hg. When obtaining stability with the hip joints in 20 degrees of flexion, abduction, and inward rotation, the mean pressure was 104 mm Hg, and in approximately 20 degrees of flexion, abduction, and forced inward rotation it was 160 mm Hg. We conclude that these rotational positions, often used to retain the joint in CDH or hip joint instability, induce intracapsular pressures that may cause occlusion of epiphyseal-physeal vessels and thus may be responsible for the avascular epiphyseal necrosis and growth disturbance seen in these patients.