Parallax radiology of the hip

We report our use of a simple radiographic technique that uses the principle of parallax for evaluating the anterior-posterior relationship of the proximal femur to the triradiate cartilage in skeletally immature patients. Thirty-six paired plain radiograph parallax views were compared with 13 respective computed tomography scans of the hips in seven patients. All had undergone closed or open reductions and were in spica casts at the time of radiographic evaluation. The parallax views detected all cases of anterior or posterior subluxation or dislocation when present. We found this method to be reliable and easily performed in the casted patient for use in radiographically evaluating pediatric hip subluxation in the anterior-posterior dimension.