Lateral Suture ACL Repair Surgery |
Lateral Extracapsular Stabilization Technique (MRIT)

Lateral Extracapsular Stabilization Technique (MRIT)

What is MRIT?

MRIT is Modified Retinacular Imbrication Technique (MRIT) to repair torn cruciate ligament.
·  The cranial cruciate ligament (C) is one of the main stabilizing structures of the stifle joint (in man this joint would be called the knee). The cranial cruciate ligament serves to prevent forward movement/Slipping of the tibia bone (shin bone) relative to the femur bone (thigh bone), to prevent internal rotation of the tibia bone, and to limit hyperextension of the stifle. Its main job is to hold the femur and tibia in proper alignment during all forms of activity. 
Canine -Stifle-Joint-Canton-Animal-Hospital
·  Two meniscus cartilages (M) located inside of the joint are crescent-shaped pads that serve as cushions, provide stability to the joint, and help to push the nourishing joint fluid into the cartilage of the femur and tibia bones.
·  For more information "Cranial Ligament Rupture in Dogs."
Anterior Cruciate ligament Disease.
·         Anterior cruciate ligament disease is the most common orthopedic condition in dogs and inevitably results in degenerative joint disease (arthritis) in the knee joint. It is typically the result of a degenerative process in knee joint of dogs, rather than from athletic injury or trauma. Traumatic CCL rupture may be seen in less than 5-10% of the total ACL ruptures seen in dogs.
·         It may affect all breeds and all sizes of the dogs but most common in large breeds.
·         The ligament may undergo progressive degeneration and partial tearing over a period of months, before it suddenly ruptures during normal physical activity and show the symptoms of ACL rupture.
·         The cause is unknown, but conformation of the limbs and genetics may play a role.
·         Partial ligament tears may be difficult to diagnose and frequently occur in both legs at the same time.
·         When the ligament tears, the stifle becomes unstable. The femur and tibia bones that form the joint then rub back and forth on each other (termed "drawer movement"). This results in pain due to stretching of the joint capsule, potential damage to the meniscus cartilage, and inflammation of the joint (called arthritis). In about half of the patients, the meniscus cartilage on the inner side of the joint (medial meniscus) has been torn and the damaged portion must be removed.
  Symptoms of CCL disease
·  Limping
·  Holding the hind limb up
·  Sitting with the leg stuck out to the side
·  Stiffness, especially after exercise
·  Pain when the joint is moved or touched
·  Swelling of the joint
·  Sometimes clicking sound when walking
 How is ACL disease diagnosed?
·  Dog’s medical history and a complete examination using tests of the integrity of the ACL, including the “cranial drawer” and “tibial thrust” tests. X-rays should be performed to assess the amount of arthritis present and aid in determining treatment options. Sedation or anesthesia is necessary for making the definitive diagnosis, to avoid causing pain to your pet.
·  All dogs that are going to have cruciate surgery should have a correctly positioned x-ray taken to measure the slope of the tibia so that an informed decision can be made on the appropriate type of surgery that should be performed. In our experience dogs that have a steep tibial slope (especially large breeds) do much better with the TPLO surgery. This may not be an important factor in small breeds even with a steep tibial slope, but the clients should be aware of the fact that a steep tibial slope will put much greater force on the synthetic bands we use in surgery (MRIT), therefore they may break.
Surgical Treatment:
"Surgery is generally recommended as soon as possible to reduce permanent, irreversible joint damage and relieve pain."
Several surgical techniques are currently used to correct CCL rupture. Each procedure has unique advantages and potential drawbacks. Your veterinarian will guide you through the decision-making process and advise you on the best surgical option for your pet.
For information on other types of surgery used to correct CCL injuries in dogs, check link to "Cranial Cruciate Ligament Repair: Tibial Plateau Leveling Osteotomy (TPLO)" and "Cranial Cruciate Ligament Repair: Tibial Tuberosity Advancement (TTA)" and TightRope® procedure
Modified Retinacular Imbrication Technique (MRIT) /Lateral Suture Stabilization (LSS)
·         The MRIT /LSS technique is the oldest surgical correction for cruciate ligament injury in dogs. The name of the procedure originates from the fact that the joint is stabilized outside the joint capsule (externally).
·         CCL repair surgery typically consists of an initial examination of the inside of the knee. This examination may either be done by opening the joint capsule and looking inside or by using an arthroscope. Any damaged or torn portions of the CCL are removed. The shock absorber, or cartilage meniscus, that cushions the knee and sits between the femur and tibia, is examined. If the meniscus is torn or damaged, that part will be removed. After the joint capsule has been examined and any cartilage or ligament fragments are removed, the joint capsule is sutured closed.
·         “If the meniscus is torn or damaged, that part will be removed.”  
·         In the MRIT procedure, a suture is passed from the outside/lateral aspect of the knee joint to the front of the tibia. Some surgeons refer to this as imbricating, or overlapping, the extracapsular tissues to pull the joint tight and create stability to prevent front-to-back sliding of the femur and tibia. Usually, one or two bone channels or holes will be required to pass the suture from back to front.
·         There have been several innovations in external capsular repair during the past decade. New materials, anchoring devices, and tools have allowed veterinary surgeons to perform this surgery more successfully than ever before.
·         It is one of the extra-capsular techniques which mean the function of the ACL, which is inside the joint, is replaced by placing a suture outside the joint. The suture most commonly a type of medical grade "fishing line" is placed around the fabella and through the proximal tibia (Shin bone).  
·         This technique is used most commonly for small dogs and cats and has good outcomes in small breed dogs
 Expected Recovery period:
·  By 2 weeks after the surgery your pet should be touching the toes to the ground at a walk.
·  By 8 weeks the lameness should be mild to moderate.
·  By 6 months after the surgery your pet should be using the limb well.
Postoperative Care.
·         The limb may or may not be bandaged postoperatively (surgeon’s preference). Very restricted exercise is allowed for the first 8 weeks, with a gradual return to normal activity over the next several weeks. The muscle force across the knee joint is four to five times body weight, and “abuse” of the limb may cause implant failure before the development of strong fibrous tissue. Clinical experience indicates that if the lameness does not improve over the next 8 to 12 weeks, or if it improves but then worsens, there is either a torn meniscus or a suture break or reaction. It is therefore important for the surgeon to know exactly where the knots were placed in order to expedite suture removal. Such removal of the imbricating sutures after 3 months postoperatively does not increase drawer motion because the fibrosis created by surgery provides long-term stability.
·         With the extra-capsular techniques, about 85% of the cases are significantly improved from their preoperative state. With the extra-capsular technique, we can expect that 50% of these dogs will have some degree of lameness, whether it is mild or intermittent following heavy activity.  On the other hand, about 50% regain normal function of the limb.
·         Even though these surgeries may not return the limb to perfectly normal function, these dogs usually are greatly improved over their condition prior to surgery.
·         The extra-capsular techniques will not stop the progression of arthritis that is already present in the joint. As a result, your pet may have some stiffness of the limb in the mornings. In addition, your pet may have some lameness after heavy exercise or during weather changes. To help with stiffness Chondroitin sulfate, MSM and glucosamine combinations, Adequan injections and NSAID (Non- Steroidal Analgesic Inflammatory Drug) may be given.
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