To comprehend hip dislocation and its treatment, it's essential to have a basic understanding of anatomy. The normal hip joint is akin to a ball and socket, where the thigh bone, or femur, forms the ball, and the pelvic bone's acetabulum constitutes the socket. This joint relies on the femoral head and the acetabulum working in harmony. The femoral head is kept securely in place by the capital ligament, also known as the round ligament of the femoral head, which spans across the joint's center. Additional support comes from the surrounding hip muscles, the upper rim of the acetabulum acting as a protective ledge, and the fibrous capsule enveloping the entire joint.
Understanding Hip Dislocation
Hip dislocation, or hip luxation, occurs when the femoral head becomes separated from the pelvic acetabulum. For this to happen, traumatic forces must be severe enough to rupture the capital ligament and tear the joint capsule. Typically, the femur dislocates up and forward in relation to the acetabulum.
Identifying a Patient with Hip Dislocation
Recognition of hip dislocation doesn't always require radiographs; it's often evident simply by observing the patient's gait. An affected pet will avoid bearing weight on the affected leg, which may appear shorter than the others.
If left untreated, a false joint composed of scar tissue and fibrous connections may form, allowing the pet to bear some weight but in an abnormal manner. These false joints are not robust and do not offer a normal range of motion. However, they may suffice for small, less active pets such as indoor cats or sedentary toy-breed dogs. Nevertheless, restoring the hip to its natural configuration usually yields better results.
The Role of Radiographs
While clinical examination can sometimes indicate luxation, radiographs are crucial for comprehensive patient evaluation. Radiographs provide essential information beyond confirming the luxation. In cases where the capital ligament tears, a bone chip may detach from where the ligament was attached to the femoral head. If the hip were simply popped back into place without addressing the chip, it would continue to cause pain and discomfort. Radiographs also help assess hip dysplasia, which may impede manual joint reduction or necessitate surgical intervention. In puppies or kittens, damage to the growth plate must be assessed, particularly if trauma is involved.
Closed Reduction: Putting the Pieces Back Together
Closed reduction involves repositioning the dislocated bones without surgical intervention. If the hip appears normal aside from the luxation, closed reduction is typically attempted, though success diminishes after approximately three days due to local muscle contraction. In cats, closed reduction is often unsuccessful, regardless of the luxation's duration. Anesthetizing the patient to relax local muscles is necessary for this procedure. The femoral head is manipulated back into place, often accompanied by a noticeable "pop" sound. Radiographs confirm the successful reduction, and the patient is confined to a cage or a similar small area for approximately two weeks while the joint tissue heals. Traditionally, an Ehmer sling has been used to hold the leg in position during healing, but this method can lead to bandage sores if not precisely fitted. Many specialists prefer cage rest for safety reasons.
Surgery: When Closed Reduction Falls Short
When closed reduction is ineffective, surgical options come into play. Various surgical techniques aim to stabilize the hip joint:
- Joint Capsule Repair: In ideal cases, where the joint capsule is only slightly damaged, it can be sutured back together to maintain proper alignment.
- Screw Fixation: When the capsule is too damaged for direct repair, screws can be placed around the acetabulum. A hole is drilled through the femoral neck, and a sturdy suture runs around the screws and through the femoral neck to secure the femoral head.
- Pinning: This technique involves inserting a pin through the femur, out the femoral head, and into the acetabulum, effectively recreating the torn capital ligament.
The choice of surgical method depends on the specific case and the surgeon's judgment. Following surgery, bandaging may be required for at least a week, with confinement recommended for several weeks to support healing.
Femoral Head Ostectomy (FHO): A Viable Alternative
FHO is a surgical option commonly employed for smaller dogs (50 pounds or less), very active dogs, or cats. This procedure entails removing the femoral head, allowing the joint to heal as a false joint—a capsule connecting the two bones without direct bone-to-bone contact. While the pet may initially avoid using the leg, they typically begin to bear some weight after 4 to 6 weeks, with nearly normal leg usage returning within a few months. FHO surgery is cost-effective compared to other methods, making it a practical choice for many pet owners.
For patients with significant hip dysplasia, this can be an opportune time to address the condition surgically, further enhancing the pet's quality of life.
Restoring Mobility and Comfort
Hip dislocation in pets is a challenging condition that requires prompt diagnosis and appropriate treatment. Whether through closed reduction, surgical intervention, or FHO, the goal is to restore mobility and comfort, allowing our furry companions to lead happy, active lives. Consult with your veterinarian to determine the most suitable treatment option for your pet's specific needs.
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