Patellar luxations that do not cause any clinical sign should be monitored but do not typically warrant surgical correction, especially in small dogs. Surgery is considered in grades 2 and over. Surgical treatment of patellar luxation is more difficult in large breed dogs, especially when combined with cranial cruciate disease, hip dysplasia or angulation of the long bones. One or several of the following strategies may be required to correct patellar luxation: Reconstruction of soft tissues surrounding the knee cap to loosen the side toward which the patella is riding and tighten the opposite side.
Lateral ImbricationThis procedure alone may be adequate for a mild case but is often used as an adjunctive procedure to supplement one of the other surgeries. When the patella slips out of its groove, the joint capsule surrounding it is stretched to allow this motion. Imbrication simply involves taking a tuck in the joint capsule. The tightened joint capsule does not allow for the slipping of the kneecap and the kneecap is confined to its proper groove.
TrochleoplastyDeepening of the trochlear groove, or trochleoplasty, can be accomplished with a variety of techniques. A chondroplasty technique involves cutting out a taco-shaped wedge of cartilage, removing a small portion of bone beneath it, and then replacing the cartilage. The result is a deeper groove. This procedure can only be performed on very young dogs, because their cartilage is thicker.
Trochlear recession involves cutting out the cartilage and bone in such a way as to create a deeper trough. This trough will then fill in with scar tissue over time. Because this scar tissue is not as good as cartilage for joint function, this technique has given way to others that attempt to preserve normal cartilage. It can, however, be useful in carefully selected cases.
Wedge recession creates a taco-shaped piece of cartilage and underlying bone. Then, the bone below the wedge is removed and the wedge is replaced, forming a deeper groove. Block recession is identical in principle to wedge recession, except that a rectangular piece of cartilage and bone, rather than a wedge, is removed.
Tibial Tuberosity Transposition
The kneecap attaches to the lower leg via its patellar tendon at a bony site called the tibial tuberosity. Many times this site forms abnormally on the inside, as with MPL, or on the outside, as with LPL. In this procedure, the surgeon fractures the tibial tuberosity and moves the tibial tuberosity back into proper alignment and secures it in place with a pin and or wire. Realigning the joint, kneecap, and tendon prevents dislocation from reoccurring.
Are there any potential complications associated with surgery?Any surgical procedure has the potential for complications. Fortunately, surgery for a patellar luxation is commonly performed and complications are rare. Potential complications include problems with general anesthesia, surgical infection, migration of the surgical implants (i.e. pins that stabilize the tibial tuberosity transposition) associated with the repair, complete disruption of the tibial crest, rarely patellar tendon rupture and failure of the surgery to completely stabilize the patella and resolve lameness.
Greater than 90% of dogs with surgical repair of grade 1, 2 and 3 patellar luxations will not have any significant complications and will return to normal or near normal function with surgery. If pins had to be used to transpose the tibial crest, these may need to be removed in 3-12 months. Some dogs “allergic” to the metal. Ultimate results will depend on the amount of arthritis existing prior to surgery and/or the severity of the patellar luxation.