TOGGLE PIN FIXATION FOR COXOFEMORAL LUXATION

One of the more frustrating orthopedic challenges facing us is reduction and stabilization of coxofemoral luxation in the dog. While closed reduction of the hip is occasionally successful, it has been reported to fail in as many as 50% to 70% of cases. For those cases unable to be managed with a closed reduction, an open repair is an option. While there are several techniques available, I find that in our practice we frequently rely on two or three methods of repair when performing open coxofemoral reduction.

Guidelines I use when recommending an open coxofemoral reduction include:

1. Inability to keep the hip reduced via closed reduction and coaptation. Closed reduction may be tried more than once without compromising success rates of an open reduction.
2. Poor anatomical conformation of the hip joint such as a shallow acetabulum.
3. Fractures off the femoral head. Frequently a piece of bone will be noted within the acetabulum avulsed off the femoral head at the attachment of the round ligament.
4. Bilateral limb injury where the animal must bear weight on the operated hip.

Several methods for open reduction have been described including capsular imbrication, DeVita pinning, trans-acetabular pin fixation, suture stabilization and the Knowles toggle pin technique, among others.

My preference is to perform an open reduction and combine repair/reconstruction of the joint capsule with an ancillary fixation to enhance stability of the hip. For small breeds a trans-acetabular pin repair is many times very successful. Problems with this technique include those associated with keeping the leg in a non weight-bearing sling (Ehmer sling) for 10-21 days and the need for a second surgery to remove the pin. Also, if the dog has another fracture in the same leg, an Ehmer sling may be contraindicated. Bilateral limb injuries can preclude use of a trans-acetabular pin and Ehmer sling.

The toggle pin method of fixation was originally described by Dr. Robert Knowles and has been used with slight modification since. The intent of the toggle pin is to recreate the effect of the round ligament, which attaches the femoral head to the acetabulum in the acetabular fossa.

Previously, the toggle pin was fashioned from a piece of Kirschner orthopedic wire around a jig. There are now commercially available toggle pins (IMEX Veterinary, 800-828-4639) which simplify the surgical technique.

Either a 3.2 mm or a 4.0 mm toggle pin is selected based upon patient size. An appropriately sized hole is drilled across the acetabulum, through which the toggle pin and attached suture is passed. A "tunnel" is then drilled from the area of attachment of the round ligament on the femoral head, down the femoral neck and out the lateral cortex of the proximal femur. The heavy nylon suture used is passed through this tunnel and out the lateral side of the femur to allow the femoral head to be pulled firmly into the acetabulum. The suture is then tied on the lateral side of the femur to maintain the reduction of the femoral head.

The toggle pin repair has the advantage of allowing the animal to bear weight on the leg early in the postoperative period. Weight-bearing must be controlled, as over-activity, jumping or falling could cause the suture to break prematurely and reluxation to occur.

Please call if you have any questions about the toggle pin technique, or hip luxation in general.

CHALLENGES OF COAPTATION

One of the challenges in fixation of fractures and luxations in practice, is when to cast or splint a limb. While open reduction has advantages and disadvantages, closed reduction and coaptation also poses a unique set of advantages and disadvantages. Some of the advantages seen with coaptation splints include faster healing time, decreased patient morbidity and less cost to the client.

When we preserve the intrinsic blood supply to a fracture through a closed reduction, clinical experience has shown that many times we can achieve healing faster than with an open reduction. Balancing that, in many cases is a less precise reduction and stabilization that may negate the positive benefits of closed reduction and coaptation.

In general, fractures that may be amenable to a closed reduction technique are those located below the elbow, and below the stifle joint.

The purpose of this newsletter is not to detail bandaging/casting techniques, but to hopefully help with the postoperative care of those. Over the years, our biggest frustration has been with patient and owner compliance in bandage care once we have discharged the animal. For that reason, whenever we discharge a patient with a cast, splint or bandage, we now include a printed instruction sheet detailing proper bandage care. Those instructions are included here, and offered for your use if you wish to copy them, or include them in your practice.

Please do not hesitate to call should you have any questions about bandaging, bandaging techniques, or if you have questions about whether or not a fracture could be managed appropriately in a coaptation splint or cast.

Bandage Care Instructions

1. Keep the bandage clean and dry. Cover with a plastic bag if going outside and the grass is wet!
2. Monitor the toes for swelling by checking to make sure both toes remain positioned together. Call if you suspect the foot is swelling.
3. Watch for any wet spots seeping through the cast/bandage.
4. Monitor for any foul odor detected from the cast/bandage.
5. If your pet is licking or chewing at the cast/bandage excessively, it may indicate there is a problem underneath and it should be checked.
6. Make sure the bandage/cast is not slipping down the leg and that no sores are developing at contact points with the skin.

Please do not hesitate to call should you have any questions about bandaging, bandaging techniques, or if you have questions about whether or not a fracture could be managed appropriately in a coaptation splint or cast