The differences between TPLO, TTA and MMP cranial cruciate ligament rupture surgery

This procedure was developed in the 1990’s and was designed to support larger breed dog’s predisposed to a steep tibial slope – often resulting in injury that requires surgery to repair. These dogs were not candidates for surgical stabilisation through the use of suture acting as replacement tendons as the pressure and tension would often cause the suture to snap (in large to giant breed dogs), rendering the surgery ineffective. These dogs required a change to the bone structure (osteotomy), hence the inception of the TPLO.

The procedure ultimately requires the tibia to be cut and reshaped. This is carried out via a wedge shape being resected from the head of the tibia which is then rotated a pre-set number of degrees; thus, allowing the weight bearing surface of the joint to rotate and is then plated and stabilised in place. This action moves the patella tendon attachment forward, changing the physics at which the knee previously used to work at, offsetting the force lost by the cruciate ligament. The procedure orients the pressure and force away from the previous weight bearing motion, and results in stabilisation and the ability of the dog to weight bear again in the modified position [1].

As this procedure has been around for some time, there is a large number of studies that have been carried out and the procedure and post operative weight bearing, measured by force plate gait analysis continues to stand up as a comparative against the other surgeries [2]. Advantages for this surgery are based on evidence of a good recovery and ability to return to normal within 12 months and 6 months for smaller dogs [3]. The disadvantages are that the surgical incision is larger (20cm or more depending on the size of the dog), and therefore involves increased vascularisation and soft tissue manipulation and a higher risk of osteomyelitis [9].

X-rays and follow up revisits are generally required to check the healing progress at week 8 and possibly 12 of recovery. TPLO surgery usually has a recovery time of ten to twelve weeks. The dog should be able to walk using the leg within 24 hours and moderately weight bear within two weeks of surgery. Leash walks can be introduced at this time to the toilet only and by week eight the dog can be lead walked for up to 30 minutes twice daily. By 12 to 16 weeks the animal can be slowly increased to normal activity levels. However, this is acutely down to the individual practice’s protocol for the client.

Developed in Switzerland in 2005, the TTA has been incorporated into mainstream veterinary practice as it is less invasive than TPLO surgery. The procedure requires the tibial tuberosity to be cut and advanced forward. The strong and thick patella tendon that runs over the kneecap and inserts back into the head of the tibia then takes the tension reducing the force that the CCL rupture creates. By advancing the tibial tuberosity it decreases the angle of the slope and lengthens the patella tendon [1].

Due to the less invasive manner in which the surgery is carried out, a smaller incision is required (7.5-12cm) [9] and therefore resulting in decreased anaesthesia, and surgical time; patients were quick to weight bear and showed fewer complications directly after surgery as compared to the TPLO. However many studies that have been carried out over a longer period of time, show similar outcomes for each procedure [2],[4],[5].

Similar post op requirements to the TPLO; xrays and follow up revisits are generally required to check the healing progress at week 8 and possibly 12 of recovery. TTA surgery usually has a recovery time of ten to twelve weeks. The dog should be able to walk using the leg within 24 hours and moderately weight bear within two weeks of surgery. Leash walks can be introduced at this time to the toilet only and by week eight the dog can be lead walked for up to 30 minutes twice daily. By 12 to 16 weeks the animal can be slowly increased to normal activity levels. However, this is acutely down to the individual practice’s protocol for the client.

MMP is described as being a faster technique to use than the tibial tuberosity advancement (TTA) and is considered an advancement on the TTA procedure. The surgery requires a cut to be made in the front aspect of the tibial tuberosity allowing the patella tendon to move forward and a wedge shaped porous titanium insert is placed in the resected area. The wedge alters the joint angle reducing the importance of the damaged ligament – It isn’t needed. There is no need to secure the wedge in place with screws; simply a pin and staple are used to effectively maintain everything in place [6].

Having been carried out in human medicine since the 1960’s, the technique is relatively new to the veterinary space. The concept for the Maquet technique is that reduced incision size is required resulting in soft tissue integrity, reduced vascularisation and minimal implants are required and support rapid biological bone growth and fixation to develop. New bone cells permeate the wedge and bond it to the surrounding area, creating a solid repair. In turn reducing the convalescence time for the patient [8].

There are significant advantages to using this technique due to its less invasive nature including smaller incision (7.5-12cm) [9], reduction in the surgical and anaesthesia time, less implants are used, a lower incidence in osteomyelitis has been observed and the procedure reflects an overall lower cost [8]. Disadvantages noted have been due the placement of the wedge; it cannot be advanced too far as may cause the tibial crest to fracture [7]. There is a specialised kit for this procedure containing all of the required specifically engineered instruments that comes in a fully sterilizable kit [6].

This procedure is relatively new and is starting to see comparative research being carried out with varying degrees of opinion on results. One such study suggests dogs that underwent TPLO surgery had a marginally better outcome than those dogs that underwent MMP surgery. In a force plate gait analysis, the TPLO group reached 84.8% and 89.9% of normal ground reaction forces over 3 and 6 months, versus 79.85% and 84.5% for MMP [8].

Post-op requirements seem to be fairly rapid for MMP surgery are suggested xrays at week 4-6 to check progress. The animal should be floor touching within two days whilst walking, by week two may not be fully weight bearing but should be floor touching on every step. They can be lead walked from day 1-3 for five minutes (up to 20 times daily), increasing up to 20 minutes (as often as required) from day 4-14. Again, increasing distance and duration throughout weeks 14-28, then gradual off lead walks (day 28-56) heading back to normal by 3-6 months [6]. This is quite a contrast from the above recommendations and again is at the individual practice’s discretion for the patients.

Interestingly, Orthomed™ (the company that makes the MMP wedge and instrument kit) reported in 67 out of 71 cases that were seen with a tibial fracture within within three weeks of surgery (before the bone had time to heal and remodel) the owner reported that the dog was exercising off the leash. So highlights the importance of owner education on post operative instructions and during the post operative period [6].

In any of the surgeries outlined above the Veterinary nurse can play an important role in the procedure itself, post operative care immediately after surgery and in client education and follow up progress calls to assist the recovery of these patients.