![]() ![]() If the luxation is not corrected, a false joint, consisting of scarring and fibrous attachment, may form and the patient may begin to bear some weight again but not in a normal way. The patient will not be bearing weight on the affected leg and the leg may actually seem shorter than the other three. The femur almost always luxates the same way: up and forward.Ī radiograph is necessary to confirm the luxation but it will be clear simply from looking at the patient (assuming he or she is walking) that a major orthopedic problem exists. In order for the hip to luxate/dislocate, trauma must be severe enough to break the capital ligament and tear the joint capsule. The more medical term is “hip luxation” and you will probably hear your veterinarian use this term. Hip dislocation is the common term for the separation of the femoral head from the pelvic acetabulum. Also keeping the bones in their proper location are the muscles of the hip, the upper rim of the acetabulum which acts as a protective ledge, and the fact that the whole joint is enclosed in fibrous capsule. The femoral head is held in place by a thick ligament called the “capital” ligament or simply the “round ligament of the femoral head” which spans across the center of the joint. The normal hip joint can be described as a "ball and socket." The thigh bone, called the "femur" possesses a head that constitutes the "ball" part of the hip joint while the socket is a special area of the pelvic bone called the "acetabulum." In other words, the femoral head and acetabulum form the ball and socket of the hip joint. When the patient is properly positioned, as in Figure 2D, it is evident that coverage of the dorsal acetabular rim (white arrows) is similar on both sides.In order to understand how hips dislocate and how they can be put back in place, some knowledge of the anatomy is needed. The dorsal acetabular rim (white arrows) appears to provide more coverage of the right femoral head and less coverage on the left side. Oblique positioning will result in false assessment of dorsal acetabular rim coverage of the femoral head, as shown in Figure 2C. ![]() Additionally, the left (down) ilium appears narrower. In this image, the right (up) obturator foramen is increased in width compared with the left. In Figure 2B, the right hemipelvis has been elevated from the imaging plate. The pelvis is rotated with the right hemipelvis farther away from the imaging plate. The right stifle should be moved axially (medially) so the femurs are parallel. The right femur/stifle should be further internally rotated (so the patella is more centrally located over the femur). In this example, there are multiple positioning errors. Pelvic radiographs must be assessed for adequate positioning and should be repeated if the pelvis is oblique, as in Figure 2A. Ensuring that both limbs are positioned similarly allows side-to-side comparisons. This can be useful when radiographic changes are equivocal. Figure 1C shows an example of the pelvis correctly positioned.Īltering the degree of limb extension or flexion and changing the degree of internal or external rotation can significantly affect the appearance of the femoral head and neck. Ideally, the sacrum, ilial wings, and entire 7th lumbar vertebra should be included in the image. Note the uniform and equal size of the obturator foramen on this well-positioned radiograph. In this image the femurs are parallel with each other and parallel with the imaging plate. If the stifles are kept internally rotated, the patella should be centrally located over the distal femurs, as seen in the normally positioned radiograph ( Figure 1B). The limbs are then extended, maintaining the internal rotation, until the femurs are parallel with the table. While in a flexed position, the limbs are internally rotated and abducted so that the stifles are almost touching. All but the pelvis and hindlimbs are within the trough. This view is best obtained with the dog placed in dorsal recumbency, which is done by using a foam positioning trough. ![]() Step-by-Step: Pelvic Radiography Positioningįigure 1A demonstrates the normal positioning for the ventrodorsal hip-extended view (the view that should be submitted to the Orthopedic Foundation for Animals). ![]()
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