Hip luxation is a common orthopaedic situation encountered in dogs. They account 90% of luxations. The goal of the treatment is to reduce the luxation, to avoid recurrence and to stabilize the joint. Surgeons must be familiar with more than one method of repair because one method cannot be used in all the cases due to the multiplicity of situations. Closed reduction is the first step; it's satisfactory in near of 50% of the cases. In those cases of recurrence of instablity, or where reduction is impossible we propose a surgical and evolutive strategywith 3 techniques: open reduction, deep gluteal muscle transfixion, prosthetic capsule.
Hip luxation can be detected by physical examination: rotation of the limb and dorsal displacement of the trochanter are the main facts. At least two radiographic views of the pelvis are essential to confirm the clinical diagnosis and to identify other injuties.
The hip is a ball-and-socket joint that allows a wide range of motion. Primary stability of the joint comes from this architecture and from joint capsule and round ligament; secondary support of the hip joint comes from surrounding muscles and a proposed hydrostatic stability factor. In cases of luxation the majority of these elements are involved. Avulsion fractures, interposition of the joint capsule may fill the acetabulum and thus prevent closed reduction.
Closed reduction should always be attempted as soon as possible after the injury. The patient is anesthesied and placed in a lateral recumbency. Countertraction is maintained during the reduction. The luxated limb is grasped by the stiffle, rotated laterally abducted and pulled distally to bring the femoral head to the acetabulum .As the femoral head moves distally over the rim of the acetabulum, the femur is rotated medially and adducted to a normal position. The joint is manipulated through a full range of motion and pressure is placed on the greater trochanter to evacuate clotted blood and debris. Proper reduction and stability are confirmed by radiographs and manipulation of the joint through a full range of motion.
Open reduction is necessary if the femoral head does not reduce adequately or reluxates easily from the acetabulum when slight stress is applied. Open reduction can be achieved via a cranio-dorsal or caudal approach to the hip joint. A reduction forceps placed on the sub-trocanteric part of the femur make easier handling of the hip. Acetabular debris is removed and the inverted joint capsule is everted; the joint is reduced and tears or incisions in the joint are sutured.
In case of instability or in extensive damage to the surrounding soft tissues a stabilization technique is necessary.
The transfixion of the deep gluteal muscle realize a substitue for the joint capsule. This technique involve a screw and a spiked washer anchored in the dorsal edge of the acetabulum. Acording to the size of the dog we use one or two 2,7 or 3,5 cortical screws. In an experimental study we have demonstrate the differentiation of the transfixed muscle into a structure closed of the tendon. Limit of this technique is extensives damages to the muscles. In a clinical retrospective study of 76 luxation we have success in 85% of the cases. If an instability persit we use a joint capsule substitution with a strip of polyester (Lygeron) anchored with two screws in the dorsal edge of the acetabulum, the stip is passed through a tunnel drilled in the trochanter and then fixed into the femur with a screw and a spiked washer. This technique can be used after the transfixion technique, using the screw and washer of the first technique.
The limits of the use of these techniques are hip dysplasia and neurological associated problems; in our experience the longer the hip joint remains luxated don't influence the quality of the results, we have used these techniques up to one month after injury.
In retrospective clinical studies we obtain 85% of excellent results. This is due to the fact of testing the stability of the hip after each steps of this evolutive strategy. In this manner we limit to very few cases recurrence, excision arthroplasty or total hip replacement.