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At the New Plymouth Vet Group, we have been offering this new modification of the TTA (tibial tuberosity advancement) procedure for the last 7 years and have performed the operation on over 250 cases.

Many different surgical techniques exist to treat dogs with cranial cruciate ligament failure but remarkably few of these have been subject to proper review and reported in veterinary literature. There remains considerable controversy about the absolute or relative merits of the range of currently used cranial cruciate operations.

Extra-articular stabilizations 
A synthetic material is placed outside the knee and anchored to the bones on either side of the joint. A wide variety of fixation methods and locations are employed. The aim is to stabilize the joint against excessive movement and in the end, the scar tissue that forms around the joint provides the long term stabilization. This procedure called a lateral tie is now best used in small dogs and cats.

Tibial Osteotomy 
These operations aim to change the mechanics of the joint by altering the shape of the tibia.
TPLO tibial plateau leveling operation was developed in the 1980s and TTA  tibial tuberosity advancement was developed in 2002. It is widely accepted that the tibial osteotomy (bone-cutting) operations offer the best chance of a return to pre-injury levels of athletic activity, especially in larger or more active dogs. However, the original TPLO and TTA techniques are complex and costly.

Prices from Veterinary specialists may be between $5000 to $7000 dollars for a TPLO operation where the MMP procedure at New Plymouth Vet Group is around $2500 with good results.

With prices like these, it is not surprising that most dogs which could benefit from these operations do not get them. The  MMP technique using a wedge-shaped implant of titanium foam has found widespread popularity across the world with 30,000 dogs successfully treated. The surgery is technically less challenging and less invasive than conventional TTA and  TPLO, it takes less time and therefore can be charged out at a rate that means that more animals can use this more successful surgery. The MMP surgery now only costs slightly more than the old lateral suture technique (due to the costs of the titanium foam implant). The system is designed with carefully designed instrumentation and we have attended courses with Orthomed, the company that has designed the system that has allowed us to achieve good results in general practice using this technique.
We charge one fee that includes post-op revisits and so no hidden costs, but we are not orthopaedic specialists and have not undergone the years of training and examinations that allow this claim so if you would prefer we can arrange a referral for these surgeries to a specialist.
We have adopted a zero-pain philosophy for these operations, so we are using morphine preoperatively then once under a general anesthetic a constant rate infusion of ketamine is given intravenously during the surgery and local blocks are used before the dog is awake to keep everything comfortable post-op.
An epidural is performed once under anaesthetic. A spinal needle is used to administer morphine and local anesthetic around the nerves in the spinal cord dulling any sensation meaning that the anaesthetic can be kept to a minimum.

The operation is based on a technique developed almost 50 years ago for use in human knees by Dr Maquet, a Belgian orthopaedic surgeon. The operation works by redirecting the force generated by the large quadriceps muscles to compensate for the failed cruciate ligament. This is achieved by cutting free and moving forward, the front part of the tibia (the tibial tuberosity) attached to the quadriceps muscle.
The bone cut is called an osteotomy and the osteotomy is stabilized using a modern wedge-shaped orthopaedic implant made from material called Orthofoam. The pin and staple seen in the x-ray are used to hold the implant in place.
The porous titanium Orthofoam promotes remarkably rapid bone ingrowth and healing and this is key to the reduced resting time and minimal pain seen with MMP surgery.
Successful recovery after knee surgery, no matter which procedure has been used requires a period of controlled activity. Compared to other procedures MMP causes less discomfort and while a comfortable, pain-free patient is obviously a good thing, many dogs are tempted to use the operated leg too much, too soon.
No matter how comfortable and confident your pet is feeling in the days after their MMP operation it is absolutely essential that running, jumping, and general “rough and tumble” with other pets is avoided for the first 6 weeks or so.

The bone must be given time to heal adequately and too much strain placed on the osteotomy too early can result in a stress fracture or implant failure and while this is rarely catastrophic, the ensuing complication may be painful and will certainly delay the recovery. 94% of fractures occur while a dog is exercising off the leash against the advice given.

The recovery period is outlined below:
First 2 weeks
Bandages are not used following MMP because it is important that your pet is able to flex and extend the operated knee freely right from day one. A light dressing may be placed over the incision. The skin sutures are removed 10 days after surgery.

During the first 14 days
Your pet should be encouraged to take frequent short leash walks, 5 -10 minutes six or eight times daily is a good starting point. It is important that the operated knee joint is returned to use as quickly as possible – concentrate on walking relatively slowly as this will encourage the patient to use the leg. This is the dog’s physiotherapy post-surgery so it is vital that we get out and move around. Ideally, your dog should go outside ON A LEASH to the toilet during the first two weeks after surgery. Do not swim the dog. No other exercise is recommended for the first 14 days – it is important to not let your pet loose to run freely in the house, particularly up and downstairs.

Third and fourth weeks
The amount of activity can now be gradually increased but it is essential that the patient is still not allowed off the leash. Leash walks can be longer and faster though you need to take care to ensure that the patient continues to use the operated limb confidently at every step.

Fifth and sixth weeks
Check X rays are scheduled for the end of week four and these should confirm that the osteotomy is healing well. Bear in mind that although bone healing and remodeling will be progressing nicely, full strength will not be established for several more weeks. At this stage, the patient will be capable of frequent lengthy (30 minutes or more) leash walks and we will soon be introducing some free-running activity. The key to success is a program of gradually increasing activity. At first, the patient can be allowed off the leash towards the end of the last walk of the day – choose a quiet area with a good surface (a short cut grassy park is ideal) without dogs or other distractions that might encourage your pet to do too much too soon. Five minutes is enough for the first day off the leash. Subsequently, the amount of free running play and exercise can be increased gradually back towards normal pre-injury levels. Most dogs will be capable of full, unrestricted athletic activity within 12 weeks of their MMP operation. Some residual low-grade stiffness and lameness may still be seen at twelve weeks, but this will resolve completely over the subsequent month or two as the patient regains full fitness and muscle tone.

If you have any questions, please don’t hesitate to email info@npvet.co.nz

Dr Robert O’Connor BVSc

References:

  • Orthomed publications
  • An owner’s guide to MMP and the MMP handbook Owners discharge Information
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