Wisconsin Veterinary Orthopedics is currently employing several methods to correct both medial[ inside] and lateral[outside] luxation of the patella: preoperative x-rays and an exam determine what procedures[s] will give the patient the most long term benefit. Many patients with luxating patellas have an angular limb deformity; our goal is to neutralize the forces on the patella to prevent luxation. Below we’ve outlined the procedures we most commonly employ.
This very non-invasive method of correction simply involves pleating the joint capsule with ligatures on the side opposite the luxation; this tightens the joint capsule on the opposing side to avoid luxation. This procedure is very safe, has few complications and is employed on almost all of our luxating patella surgeries. For some small dogs with mild disease this can be employed as the only means of correction.
Lateral Fabellar/Patellar Ligament Suture
This procedure is used in more severe cases of luxation where imbrication of the joint capsule alone will not function to prevent further luxations. A decision to perform this procedure is usually made during surgery. Here, the patellar ligament is simply pulled back from the direction of luxation with a new nylon ligament; this is a low risk procedure with minimal postoperative pain.
As most luxations occur on the inside or medial side, two muscles can be incised to relieve some of the force on the patella; these muscles to be cut and thus released are the Sartorius and Vastus Medialis. They are transected where they join the patella[ see diagram]. This procedure is generally used along with some of the other procedures in this discussion and creates very little swelling or discomfort to the patient.
Tibial Tuberosity Transposition and Advancement
A small osteotomy[cut] of bone is performed where the patella attaches to the Tibia . This segment is advanced slightly with a “cage” and transposed toward the luxation where it is fastened with a stainless steel plate called an X-Gen Plate. A “spacer” of either 2,4 or 6 mm is applied to transpose the plate the most optimal amount. This procedure is optimal for severe luxations or where angular limb deformity is present. This redirects the forces on the patella down the limb rather than off to the side.
For the treatment of Cranial Cruciate Ligament Deficiency
Cruciate ligament deficiency is the most common orthopedic lameness seen in the dog today. Large breeds seem to be more at risk of this ailment. Physically, the cranial cruciate ligament tears when excessive internal rotation occurs when the knee is in slight extension. The caudal cruciate ligament rarely tears, but when it does it generally happens concurrently with a cranial cruciate tear. Your pet usually yelps when the injury occurs and will limp afterwards. This limp may become better over the next week only to become chronically lame thereafter.
Though over 200 procedures are cited in the literature as being available for treatment of cruciate ligament tears, in my opinion the Tibial Tuberosity Advancement [TTA] and Tibial Plateau Leveling Osteotomy[TPLO] have four main advantages:
compared to procedures we have performed for the last 20 years using crimp tubes and synthetic ligaments, the TTA and TPLO are simply MUCH STRONGER.
• Recovery Period
Simply put, the recovery period of leash walking is literally one third as long. Using nylon implants we generally perform leash walking for up to six months; for TTA and TPLO surgery we generally only use leash walking for 60 days or until evidence of bone healing is seen radiographically.
For the working dog, this is an easy decision; TTA/TPLO patients have the potential to resume an active working life in many cases. Comparatively, the instability of nylon and crimp tube techniques can lead to more joint swelling for the working patient.
Unlike nylon crimp tube techniques that rely heavily on surgeon technique for success, the TTA and TPLO generally have high success rates.
TTA/TPLO- What’s the difference?
Perhaps a better explanation of how these two procedures are different is answered in how they are alike; both procedures prevent tibial thrust. Tibial Thrust is the forward momentum produced in the tibia or lower leg bone when a force is applied to the leg through forward or other weight bearing motions on the leg. This thrust creates a sensation of instability for the patient and results in joint swelling of the knee. By limiting Tibial Thrust we thus limit knee instability and pain.
The TTA accomplishes this[Limitation of Tibial Thrust] by dragging the femur back into its normal position through tension placed on the patellar ligament. This broad ligament now acts as the new cruciate ligament to prevent instability of the joint.
The TPLO limits tibial thrust by reducing the angle of the joint itself. In a normal knee joint the angle of the tibial plateau[ shelf created by the lower leg bone or tibia] may be 20-30 degrees; hence when force is applied to the leg the tibia tends to thrust forward. By rotating the tibial plateau through the osteotomy[bone cut] the new joint becomes nearly flat making it difficult for tibial thrust to occur.
In our orthopedic practice we have seen similar results with these two procedures; younger patients seem to recover much faster than middle to older patients. Having performed the TTA for 4 years at this point, we currently endorse the TPLO over the TTA for the following reasons:
1. The meniscus is spared to a large degree with the TPLO
2. TPLO has less chance of implant failure as screws are larger and more stable
3. TTA has more chance of bone fracture
4. We currently can achieve more cost effectiveness with the TPLO and we insure all of our work with the TPLO because of its strength.
Post Operative Directions: TPLO/TTA
What to expect after surgery
Historically, veterinarians have used Cage Rest as the main means of rehabilitation following knee surgery. Most veterinarians were afraid that the crimp tubes historically used would stretch and come apart destroying all of their efforts. The TTA allows a different means of rehabilitation. Like human medicine, the sooner the patient is up and moving around the quicker the recovery. Please remember though, premature overuse can result in damage to the healing process; do not let your dog run loose until pronounced fully healed by your veterinarian.
First Two Weeks
Leash walking is a must during this period. The first 5 days you may have to support your pet’s abdomen with a towel or leash while walking and especially when getting into the car or going up steps to avoid using the repaired limb. Expect swelling of the limb below the surgery site and expect the pain to be the worst the first 48 hours.
- First 5 days – ice pack the knee 3-4 x/day for 15 minutes; this will limit swelling
- Pain medication- as directed by your veterinarian, we generally use tramidol and Previcox together during this time
- After 48 hours, apply heat to the area 3x/day for 15 minutes. Afterwards, perform range of motion exercises to at least 45 degrees of flexion for at least 20 repetitions
- No other exercise is recommended the first two weeks
- Clean the wound daily if needed with dilute hydrogen peroxide and DO NOT allow the dog to lick it by applying your Elizabethan collar
Second Two Weeks
At this point walking on a leash is tolerated.
- Pain medication- continue using an anti- inflammatory such as Previcox daily
- Apply heat to the leg for 20 minutes 2x/ day and exercise the knee through the entire range of motion[ie. 90 degrees of flexion and full extension], move the hip joint and hock as well
- Walking on a leash is acceptable, but begin with one block and stop. If the dog returns home and is not in pain you may increase this by one block increments every 5 days as tolerated , provided your dog is not in pain when the walk is over
- While walking, push the dogs hips towards the operated leg to help convince him /her that the leg can be used
- Lift the front end of the dog for 5 seconds prior to your walks to increase the strength of the leg. Try several repetitions
- Walk figure 8’s to encourage use of the leg
Third Two Weeks
No running yet, walks should no more than 20 minutes on a leash. Swimming is ok, but do not allow swimming over your pet’s head or for more than 10 minutes as this may cause inflammation.
Fourth Two Weeks
Walks over 20 minutes are now allowed, but still on a leash as you slowly build back up to normal exercise as tolerated based on pain observed after your walks. X-rays are scheduled after 8 weeks to assess the ability to exercise off leash and to assess proper healing.
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