The Procedure:

The Modified Macquet Procedure (MMP) is a surgical technique used to treat rupture of the cranial cruciate ligament in dogs. An MMP is a form of Tibial Tuberosity Advancement (TTA). The tibial tuberosity is the part of the shin bone that would be in contact with the ground if we were to kneel.

During an MMP a porous titanium wedge is slotted into a cut made behind the tibial tuberosity to move it forward. The surgery changes the angle of the forces within the joint itself, so that the pull of the quadriceps muscle helps to stabilize the joint when weightbearing.

A diagram of how the cruciate ligament functions in the joint

The joint prior to the MMP – note how the angle of the force is at an irregular angle

The joint post-MMP. With the addition of a wedge, the forces acting on the knee are at a right angle.

Cruciate Failure in Dogs:

Cruciate failure is the second most common orthopaedic condition affecting dogs after osteoarthritis. It is usually the result of an average force acting upon a weakened ligament rather than an excessive force upon a healthy joint. The disease process that affects the ligament is often also present in the other leg and about 30% of dogs that suffer cruciate failure in one limb go on to develop the problem in the other. It is not well understood why some dogs develop the condition while others do not. For example, sighthounds (such as greyhounds) are almost never affected, while the condition is quite common in labradors and rottweilers. However, individuals of any breed can be affected by a traumatic rupture.

Diagnosis:

The condition is usually diagnosed by feeling for instability, often via the “cranial drawer test” wherein the dog’s leg is manipulated to see if the tibia will slide forward – similar to the motion of opening a drawer. Not every affected dog has a positive test, but it is a very good indicator of cruciate ligament rupture.

X-rays are useful for surgical planning for many problems such as: calculating which size implant to use, ruling out other concurrent problems (arthritis, hip dysplasia and bone tumours) and detecting any swelling suggestive of cruciate disease if the drawer test was insufficient.

Management:

Cruciate rupture can be managed conservatively with medicines instead of surgery, and this treatment is sometimes appropriate for older patients, smaller patients (i.e. under 10kg) and patients that are already in need of pain relief drugs for other reasons.

Goals of the Procedure:

When performing an MMP, our end objective is that after the recovery period, there is:

NO LAMENESS

NO EXERCISE RESTRICTION

NO NEED FOR ANTI-INFLAMMATORY MEDICINES

In almost all cases this is achieved by the MMP. Complications are very uncommon and those that do occur often include implant failure or infection. At our surgery we have performed over 100 MMPs to date. We believe these cases do not usually require costly referrals to an orthopaedic specialist or referral centre. Of course, feel free to discuss all available options at a consultation.

Post-operative x-rays are sometimes required 6-8 weeks after the operation, but this is decided on a case-by-case basis.

X-ray of a dog’s leg post-operation

An x-ray illustrating how the wedge and implants sit in the dog’s leg bone

Cost:

Our approximate cost for an MMP is £1,700. This includes the costs of anaesthetising the pet, the surgery itself, the implant(s), the medicine that goes home with the pet on the day and any post-operative check overs.

Please call the surgery if you have any questions.

David Wilson BVSc MRCVS

Caroline Goldsbrough MVB CertSAS MRCVS