|Patient: 8 year old male|
|History: 8 year old male with known cerebral palsy.|
|Findings: Hip radiograph shows bilateral coxa valga and incomplete coverage of the femoral heads, more marked on the right than the left with improved coverage on the frog leg lateral radiograph.|
Coxa valga is defined by an increase in the femoral neck-shaft angle, compared to age-appropriate standards. It is commonly present in patients with cerebral palsy and may lead to such complications as femoral head dislocation.
Coxa valga is generally noted in patients with known underlying neuromuscular or skeletal disease. Commonly, spasticiy in the adductor muscles of the hip will overpower the hip abductors and extensors, leading to deformity. They may have impaired ambulation and sitting balance secondary to bilateral adduction contractures or windswept deformities. Decubitus ulcers and pain may also be present, secondary to the resultant positioning.
The diagnosis of coxa valga depends on the measurement of the femoral neck-shaft angle on a true anterioposterior radiograph. The angle is present between the midaxis of the femoral shaft and a line along the midaxis of the femoral head/neck. Femoral anteversion (which is also commonly present in patients with cerebral palsy) and rotation may have projectional effects on the radiograph, causing the false appearance of coxa valga as well. Therefore, one must take care to recognize the possible geometric distortions of the true angle when reading films. Once subluxation occurs, medial/lateral flattening of the femoral head can be seen. In dislocation, a pseudoacetabulum can be seen along the lateral margin of the ilium. CT and MRI have also been suggested as imaging modalities. However, slice orientation and thickness must be accounted for when calculating the degree of torsion.
Neuromuscular disorders (i.e. cerebral palsy, spinal dysraphism, poliomyelitis); skeletal dysplasias; juvenile idiopathic arthritis
Severe coxa valga may lead to lateral subluxation or dislocation of the femoral head. Subluxation occurs superolaterally due to the forces of the spastic flexors and adductors of the hip. Chronic subluxation/dislocation can result in acetabular dysplasia and secondary degenerative joint disease. Non-surgical measures to prevent subluxation include physical therapy and exercises, aimed at stretching the spastic agonist muscles and strengthening the weaker antagonist muscles. Orthotic devices and casting may also be employed to ensure better positioning. Newer therapies to reduce spasticity in cerebral palsy include intrathecal baclofen and local injections of botulinum toxin. Surgical therapies may also be required, including tenotomy, neurectomy/dorsal rhizotomy, and varus derotation osteotomy.
|References: Morrell DS, Pearson JM, Sauser DD. Progressive bone and joint abnormalities of the spine and lower extremities in cerebral palsy. RadioGraphics 2002; 22: 257-268.|
Schneider B, et al. Measurement of femoral antetorsion and tibial torsion by magnetic resonance imaging. The British Journal of Radiology 1997; 70: 575-579.
GE Healthcare. Pediatric Imaging: Coxa Valga. Medcyclopaedia. http://www.medcyclopedia.com
Clancy McNally, MD (HO-II), Department of Pediatrics, Children's Hospital, Omaha, NE
Phillip Silberberg, MD, Department of Radiology, Children's Hospital, Omaha, NE
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Case Number: 7519228Last Updated: 06-20-2007 The reader is fully responsible for confirming the accuracy of this content.
The reader is fully responsible for confirming the accuracy of this content.