Tibial Plateau Leveling Osteotomy – TPLO


Key Points

One of the important functions of the cruciate ligament is to prevent forward and backward sliding of the femur on the tibia bone, also known as drawer motion

Rupture of this ligament leads to debilitating lameness

The TPLO surgery compared to other techniques results in

  • a more rapid recovery
  • better range of motion of the joint
  • development of less arthritis return to athletic or working activity

The TPLO surgery has a steep learning curve – choose an experienced surgeon for your companion

 

 

Introduction

  • The stifle joint (in layman’s terms called the knee) of the dog is similar to a human’s knee. The cranial cruciate ligament is located inside the joint and is responsible for maintaining a stable joint. One of the important functions of the ligament is to prevent forward and backward sliding of the femur on the tibia bone (drawer motion).
  • Cranial cruciate ligament rupture is the most common orthopedic condition that we treat.
  • This problem afflicts all ages and breeds of dogs.
  • Frequently cruciate ligament rupture is a gradual process and not simply due to a single traumatic injury. Most dogs have a predisposing factor such as age-related ligament degeneration, pre-existing inflammation, anatomical abnormalities, and excessive slope of the top of the tibia bone, which cause the ligament to rupture.
  • Clinical signs of early cruciate disease includes stiffness or very mild lameness. As the disease advances and the ligament progressively tears, the lameness becomes more pronounced. Complete tears initially result in nonweight-bearing on the limb, but as time goes on the dog will start to use the limb. It is unusual that the lameness will resolve in a large breed dog with no surgery.
  • Rupture of the cruciate ligament in both knees is common. In fact, one out of three dogs will also develop a cruciate rupture of the opposite stifle.
  • Above is a photo of a front view of the stifle joint in a dog illustrating the cranial cruciate ligament (labeled C) and the front horn of the medial meniscus (labeled M), which is a cartilage pad located within the stifle joint that is commonly damaged with cruciate ligament tears.

Wagon Model Used to Explain Instability of the Knee Joint

  • The tibial plateau of a dog’s stifle is sloped.
  • Understanding the importance of the tibial slope when the cranial cruciate ligament is torn is somewhat difficult. We therefore present a model of a wagon on a hill, which is tied to a post.
  • The slope of the hill represents the tibial plateau, the wagon represents the femur bone, and the cable represents the cranial cruciate ligament.
  • If the cable is torn, the wagon will roll down the hill (see fig below). Likewise, when cranial cruciate ligament is torn the femur bone will slide down the slope of the tibial plateau.
  • When surface that the wagon is placed on is level and weight is put in the wagon, it does not to roll backward (see fig below).
  • In the dog, the tibial plateau leveling osteotomy levels the slope of the tibial plateau so that the femur no longer slides down the plateau. Thus a dynamically stable joint is created even when no cruciate ligament is present.

Tibial Thrust

  • When the cruciate ligament is ruptured, the slope of the tibial plateau, along with the forces exerted by the calf and quadriceps muscles cause the femur bone to slide down the top of the tibia bone called the tibial plateau. This in essence causes the tibial plateau to thrust forward with each weight-bearing stride and is called cranial tibial thrust.
  • This thrusting results in excessive wear of the cartilage of the joint. In addition, as the tibia thrusts forward it stretches the tissues which surround the joint, which causes pain.
  • Excessive cranial tibial thrust also can tear of one of the cartilage pads in the knee called the medial meniscus. This usually results in a meniscal bucket handle tear or crush injury.
  • The tibial plateau leveling osteotomy  or TPLO can eliminate cranial tibial thrust, thus creating a dynamically stable stifle and sound gait.

TPLO Surgery

  • The first part of the surgery involves removing the torn ends of the cruciate ligament and examining the medial and lateral meniscus cartilages.
  • To the right is an illustration of the front view of the stifle; note the medial meniscus, the cranial cruciate ligament and the lateral meniscus
  • The medial meniscus is concurrently torn in about 40 to 50% of dogs that have a torn cruciate ligament.
  • When the femur bone shifts backwards the femur bone pinches the medial meniscus, causing it to tear from the back part of the stifle joint and flip forward. Put your cursor over the illustration to the right – take note that as the femur bone shifts backwards the back horn of the medial meniscus tears and flips forward.
  • A torn meniscus will make a patient much more painful than a cranial cruciate ligament tear alone. As the patient walks the torn part of the meniscus may flip back and forth resulting in a audible popping or clicking noise.
  • Every attempt is made to save as much of the normal meniscus as possible and only trim out the damaged portions of this structure. This is called a partial menisectomy. It is believed that partial menisectomy results in less arthritis than a complete menisectomy.
Arthroscopy can also be used to examine the inside of the stilfe joint. This technique can also be used to clean out the joint. This is a video of arthroscopy of a dog that has a minor tear of the cranial cruciate ligament. In this case, the cruciate ligament is preserved.
  • Additional images from arthroscopy of a stifle joint. Image below left of grossly normal meniscus (mild curl of the edge of the meniscus is normal). The image below right is a partially torn cruciate ligament
  • The tibial plateau leveling osteotomy – TPLO involves making a curved cut in the top of the tibia bone (osteotomy) to include the tibial plateau. The tibial plateau is then rotated along the curved osteotomy in order to level the slope. A plate and screws are used to hold the tibial plateau in place so that the bone can heal in its new position. Below left is radiograph of a stifle before TPLO surgery and below right is a radiograph demonstrating the curved cut in the tibia bone and rotation of the the tibial plateau. Take note of the metal plate and screws that hold the bone together. The tibial plateau should not be leveled to 0 degrees or less as this will strain and potentially tear the caudal cruciate ligament. One research study indicated that dogs that had a postop tibial plateau angle between 2 and 14 degrees clinically did very well, however the original recommendation by Dr. Slocum is 5 degrees.
preop rad postop TPLO rad

 

Take note of this radiograph which is a front view of the stifle after TPLO surgery has been completed. A plate, which has been manually contoured by the surgeon to the shape of the tibia bone, is fastened in place with six screws. It is critical to ensure that no screws penetrate through the top of the tibia bone into the stifle, as this will result in severe damage to the joint with resultant arthritis. TPLO postop AP rad

 

  • Healing Phases Following TPLO surgery:
    • Unlike the convalescence from other extra-articular or intra-articular techniques, recovery from TPLO surgery frequently is more rapid and complete. In our experience, about 50% of the dogs will start to walk on the limb within 24 hours after surgery. Within 5 days after surgery most dogs will begin weight-bearing on the operated limb.
    • By 2 weeks after surgery, a moderate amount of weight-bearing can be expected. Dogs with partial tears tend to recover quicker than dogs having complete ligament tears. We have seen some dogs having partial tears recover to near full weight-bearing within 2 weeks after surgery…this is phenomenal, as we have never seen this type of a recovery with any of the other surgical techniques that are used to stabilize the knee.
    • Radiographs taken at 6 to 8 weeks postop should reveal healing of the osteotomy site.  At this time most dogs have mild or no lameness; when we evaluated our patients having TPLO, the average time for the lameness to resolve was 10 weeks.
    • At 2 months after surgery, exercise in the form of leash walks should be gradually increased each week. Increasing the number of walks per day tends to be better than just increasing the duration of each period.
    • At 4 months after surgery most restrictions of exercise can be lifted. Full working activities (hunting, agility, etc) can begin at 6 months after surgery. Unconstrained activity prior to this time can cause spraining of the soft tissues of the stifle (patellar ligament sprain) resulting in a prolonged recovery.
  • Yearly radiographs of the stifle should be taken to evaluate the degree of arthritis. The TPLO procedure should minimize the progression of degenerative joint disease.  One study indicated a trend to a slower progression of arthritis following TPLO surgery, versus dogs that received the lateral imbrication technique, however arthritis usually will develop regardless of technique.

 

Success

  • One of the best things you can do to help your dog achieve a successful recovery is to follow the recommendations by a trained therapist. In addition, to learning what you can do at home, consider finding a canine rehabilitation facility in your area.
  • A successful outcome will return your dog to full function on the limb.  In my experience, about 90% of the dogs having the TPLO regain normal or near normal function of the limb (full weight-bearing); this information is based on a retrospective survey that we conducted on our patients.  The remaining 10% of dogs have concurrent arthritis in other joints of the operated limb or advanced degenerative joint disease in the stifle; most of these dogs in this group are still helped by the surgery.
  • We have found that most working dogs will return back to full working function.
  • Dogs that have sustained a blowout fracture of the tibial plateau as a complication of falling after surgery may have residual stiffness or lameness.
  • Dogs that have been previously operated using another technique frequently are improved with the TPLO surgery, but the outcome may not be as good, versus a virgin knee that has received the TPLO surgery.

Potential complications

  • As with any surgery, complications may arise. Even though rare, anesthetic death can occur. With the use of modern anesthetic protocols and extensive monitoring devices (blood pressure, EKG, pulse oxymetry, inspiratory and expiratory carbon dioxide levels, and respiration rate), the risk of problems with anesthesia is minimized.
  • Infection is an unusual complication as strict sterile technique is used during the surgery and antibiotics are administered during the procedure.
  • Poor healing of the bone can occur if the pet is too active, especially during the first 2 months after surgery. If steroids are given to a pet for reasons such as skin allergies, healing of the bone may be severely impaired. Breakage of plates or screws or backing of screws out of the bone can occur if activity is not limited during the first 2 months. Even after the bone has healed, the soft tissues need to also heal.
  • If activity is unleashed prematurely, straining of the patellar ligament can occur. Rest and anti-inflammatory medication is used to resolve this problem.
  • Fracture of the narrow front part of the tibial crest can occur. This is not common, and usually will heal without any surgical intervention.  Recovery will be delayed, but the final result still should be very good.
  • A blow-out fracture of the tibial plateau has been seen in 0.4% of the cases (in a series of 700 cases) at our hospital.  The cause of this is due to the dog falling on the stifle after surgery.  Reoperation is performed in these cases.
  • Loosening of the screws with shifting of the slope of the plateau may occur if the pet is not restricted during the healing phase.  If the plateau has shifted a significant amount reoperation is performed.  This complication is more common in the giant breed dog, as a result we generally use a larger TPLO plate and 8 screws, instead of the standard sized TPLO plate and 6 screws to help prevent this problem.
  • It has been reported that dogs that have a very steep tibial slope (greater than 35 degrees) are at greater risk of having complications (shifting of the bones, fracturing of bones, loosening of implants). However, once the healing had taken place the function of these dogs too was very good and client satisfaction was usually very good.
  • A bone cancer can develop in the tibia bone due to the presence of the surgical implants (bone screws and plate), however, this complication is rare. Removal of the plate after healing takes place may help to prevent this complication. Because the formation of this tumor is so uncommon, there is no study available that has truly shown that removing the implants is helpful.
  • Arthritis usually is present at the time of surgery and will progress to some degree regardless of treatment or no treatment. Unfortunately we cannot reverse the arthritic and degenerative state of the joint, but the surgery may help to minimize the progression of this. I have seen cases receiving the TPLO surgery that have developed minimal arthritis years later, yet other cases have developed a lot of arthritis as seen on x-rays. Just because arthritis may be seen on x-rays does not mean that your dog will be lame on the limb. Warning signs of clinical arthritis include stiffness associated with heavy exercise and cool damp weather. Anti-inflammatory medications are useful to ameliorate a flare-up of arthritis.
  • Tearing of the meniscus (cartilage pad in the knee) may occur following TPLO surgery and additional surgery would be needed. This complication occurs less frequently following the TPLO versus when other surgical techniques used to stabilize the stifle joint.

 

Tibial Tuberosity Advancement or TTA Surgery


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