Canine Cruciate Ligament Repair

Canine cruciate ligament (CrCL) rupture, analogous to an ACL tear in people, is a common condition that usually needs surgical repair.

With surgery, there is an excellent prognosis for return to a pain free active lifestyle. Without surgery, the knee usually becomes a persistent source of pain and a limit to normal activity.

Short Answer

A small percentage of canine cruciate patients can be successfully treated non-surgically (see below). Whether or not non-surgical options will work depends on the size and fitness of the patient as well as the severity and underlying reason for the cruciate ligament tear.

There are multiple ways to repair the knee, and great controversy over which procedure is best. Despite the fact that surgeons often have strong opinions favouring a specific procedure, multiple studies have shown that there is no difference in long term outcomes for the most commonly performed procedures.

It is important for owners to educate themselves about the pro’s and con’s of each procedure, and to discuss them with their veterinarian before deciding which surgery is best for their pet.

Selecting the Best Procedure

When selecting the best procedure for your pet, it is important to consider the potential complications. 

Below is a list of complications reported in the literature for each of the most common techniques for repairing a torn canine cruciate ligament. 
(ES = extracapsular stabilization, TR = tightrope, TTA = tibial tuberosity advancement, TPLO = tibial plateau levelling osteotomy).

Surgical Complication Chart PDF – click to open

 

It is important for owners to educate themselves about the pro’s and con’s of each procedure, and to discuss them with their veterinarian before deciding which surgery is best for their pet.

Long Answer

Summary

There are four main procedures for correcting canine cruciate ligament instability and all provide excellent results. No long term study has shown one procedure is superior to another, despite the fact that most surgeons personally believe certain procedures work better than others1,2,3,4,5,6. This is further complicated by the fact that what works best in one surgeon’s hands may not work the best for another.

Since the long term results are the same, it is important to consider the potential for short term complications – what are they and how frequently do they occur? What is the worst case scenario? Which ones are greatest concern for your pet specifically?

Discuss these issues with your surgeon. Consider your pet’s age, weight, energy level, future athletic expectations, etc., and weigh this against the pro’s and con’s of each procedure. Only then can you make an informed decision about such a complicated issue.

To find out more information about these procedures and options click on a link below:

What is a Canine Cruciate Ligament Tear?

The canine cruciate ligament is a major stabilizing ligament within the knee (stifle) joint. Due to a number of reasons, in some dogs it is placed under excessive strain even while engaging in normal exercise and ruptures as a result. The reason why it has become such a common injury is the source of much debate

Sometimes the canine cruciate ligament only partially tears. Grade I tears are minor, not very painful and have the greatest potential for non-surgical repair. Grade II tears are more extensive and very painful, often more painful than a complete tear even though the joint is still stable. They usually require surgery. Grade III tears involve complete rupture of the ligament and are a surgical problem.

Once the joint becomes unstable, the meniscus is prone to tearing. Menisci are cartilage pads that cushion the impact between the femur and tibia, and once a meniscus tears the patient becomes profoundly lame – tearing a canine cruciate hurts a little, but tearing the meniscus hurts a lot.

Typical Cruciate Presentation

A common presentation is that owners notice a hind leg lameness that lasts for a day or two then resolves, so they assume it was a pulled muscle. After that, their dog could still run and play but would become stiff and limp when getting up from a nap. This situation usually worsens until one day the dog is profoundly lame.

What happened was that the CrCL tore initially, but wasn’t too painful so the dog kept using the leg. Because the knee was unstable, inflammatory degeneration following exercise began, causing morning stiffness in the joint. Eventually, the instability caused a meniscal tear and now the patient is hesitant to use the leg at all.

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Surgical Options

There are two main surgical categories for addressing canine cruciate ligament disease in dogs; one approach is to replace the ligament with a synthetic implant, the other is to alter the anatomy of the joint in order to improve stabilization.

The four most successful procedures are described below – extracapsular stabilization (ES), tightrope(TR), tibial tuberosity advancement (TTA), tibial plateau levelling osteotomy (TPLO). Each has strengths and weaknesses, and no single procedure is the best choice for all patients.
Dr. Lane prefers the extra-capsular technique or the TTA, depending on the patient. The tightrope procedure works well, but in his hands not as well as extra-capsular repairs. He has reservations about the TPLO, and only recommends it for patients with an abnormally steep tibial plateau.

The two most commonly performed procedures are the ES and TPLO, although the TTA is rapidly gaining popularity. Although many surgeons claim that the TPLO yields better results than the ES, every prospective, head-to-head, cohort study published in the peer reviewed literature to date has shown no difference in outcomes for any of the techniques based on kinematics, client based and veterinarian based subjective assessments, radiographic progression of osteoarthritis or muscle mass measures.1,2,3,4,5,6 Because long term outcomes appear to be the same for all procedures, one needs to scrutinize the short term complication rates, healing rates, and worst case scenarios should a complication occur.

Surgeries that replace the ligament with an implant

The advantage of this type of canine cruciate ligament repair is that it is safer3,5,6, less invasive, less expensive, and should the procedure suffer a catastrophic complication and fail completely, then there is still the backup option for a TTA or TPLO repair.

Because this type of procedure requires the formation of scar tissue along the implant’s path, dogs who might have impaired scar tissue forming ability should consider a different procedure. Dogs taking corticosteroid medication (e.g. steroids for allergic itchy skin), or dogs with hyperactive adrenal glands fall into this category.

Extra-Capsular Repair
Extra-Capsular Repair

In this procedure, a nylon filament is woven from a bone behind the knee through holes drilled in the tibia. The path of this implants mimics the path of the cruciate ligament except that instead of running inside the joint, it runs just outside of the joint. Eventually, this implant will weaken- it is not intended to be the long term ligament – but in the first two months post-op, scar tissue forms around it and it is this scar tissue that becomes the long term ligament.

Exercise needs to be sharply restricted for the first two months while this scar tissue forms. After that initial rest period your pet is returned to the old lifestyle – increasing exercise as quickly as possible without overdoing it and suffering a sports injury in the process. Working with someone trained in veterinary rehabilitation accelerates this recovery process, but typical patients are back to full activity level four months post-operatively.
Nylon is a material that has a quality known as “creep”, meaning that with repeated loading, it has the potential to stretch and loosen. Minimizing creep so that it doesn’t result in premature loosening of the joint is one of the major intra and post operative goals. Isometric point selection, intra operative cycling and post operative exercise restriction are some of the measures taken to prevent this phenomenon. Loosening of the implant is of particular concern in larger dogs, especially those that are likely to resist enforced rest.  For these patients, a TTA might be a more appropriate procedure.

Most studies report a 90-95% success rate with this procedure.1,2,5,7,8 However, all these studies were published before Hulse & Beale’s work on isometric point selection for optimal placement of synthetic cruciate implants9. It has yet to be proven how much this research has improved surgical outcomes, particularly in larger patients, but Dr. Lane feels the difference is significant.

In Dr Lane’s experience, this procedure yields excellent results. Many surgeons agree that it is the treatment of choice for smaller dogs. Fifty pounds body weight or less is often quoted as the cut-off weight for choosing this procedure although there seems to be no scientific basis for this rule. Dr. Lane has repaired many knees belonging to dogs weighing more that double this amount with excellent results and few complications. He believes the fifty pound cut-off point is low and should not be considered an absolute. Having said that, the larger the dog, the more likely he is to consider the TTA to be the repair of choice.

Tightrope
Tightrope

The tightrope procedure is very similar to the ES repair; most of the difference lies in the implant material itself. The tightrope implant is a braided tape that is much stronger than nylon implants. It also does not undergo stretching or creep when asked to load bear.

The advantages to this additional strength are obvious, but because the TR implant is so inflexible, it needs to be placed in a very precise manner so that it undergoes equal loading no matter how flexed or extended the knee joint is (isometric point selection – see above). Post-operative recovery rates are the same as ES repairs.

In Dr. Lane’s experience, this procedure works very well in the majority of patients, and can be used in much larger dogs with confidence. However, correspondence with multiple surgeons has found variability in complication rates.  Personally, he found a higher complication rate for TR patients than with ES repairs using nylon. For that reason, he prefers the TTA repair over the tightrope for stabilizing larger dogs.

Surgeries that alter the mechanics of the joint

There are two procedures that fall into this category, the tibial tuberosity advancement procedure (TTA) and the tibial plateau levelling osteotomy (TPLO). Both of these are considered more invasive because they involve cutting bone, but only the TPLO involves cutting the weight bearing axis of the bone.  The TPLO also changes the geometry of the joint itself, whereas the TTA does not.

The advantages of these procedures are that the implants are stronger which make them more suitable for larger active dogs, and healing doesn’t require scar tissue formation so these procedures can be used in patients that don’t form scar tissue well. There is early evidence to suggest that they may be the treatment of choice in patients with partial CrCL tears (unpublished data).

Aside from the increased cost when compared to an ES repair, the main disadvantage of these procedures is that if the implant fails, the patient doesn’t just have a torn ligament, now the patient has a broken bone.

Because the TTA does not cut through the weight bearing portion of the bone, this complication is not as severe. However, because the TPLO cuts through the weight bearing portion of the bone, the implications can be quite severe – if the fracture cannot be repaired, then the patient may need to have the leg amputated.

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TTA

TTA

The TTA is based on the premise that by adjusting the angle of the patellar ligament, the ligament that runs from the kneecap to the tibia, it can now assume the load bearing that the CrCL once had to endure. Unlike the TPLO, the TTA does not change the geometry of the joint itself, nor does it alter the contact pressure between the femur and tibia.

A cut is made in the tibial tuberosity, the boney prominence where the patellar ligament inserts, and a spacer is inserted to distract the bone a pre-calculated distance away from the shaft of the tibia. By advancing the bone forward, the patellar ligament angles forward and assumes the stabilizing duties that once belonged to the canine cruciate ligament. A plate is screwed in place to stabilize the fragment, and bone graft is used to fill the gap so that the tibial tuberosity can fuse in it’s new position.

 

Exercise is strictly restricted for eight weeks until the bone has healed, then returned to normal over an additional six to eight week period.

This is a demonstration of a TTA patient exactly 1 month post operatively.

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TLPO

TPLO

The TPLO seeks to reduce the slope of the tibial plateau, the top surface of the tibia which normally has a backward angle. This slope is often steeper in dogs with cruciate disease and is a potential cause of cruciate rupture. In theory, by eliminating this slope the need for a cruciate ligament is eliminated. Ironically, levelling the tibial plateau also changes its angulation in relation to the patellar ligament, and in the end the TPLO may just be a more aggressive way of performing a TTA.

 

 

 

A circular cut is made through the shaft of the tibia, near the knee joint. The piece of cut bone is then pivoted a calculated distance to reduce the tibial slope, and then plated into its new position.

Exercise is strictly restricted for eight to twelve weeks until the bone has healed, then returned to normal over an additional six to eight week period.

Unlike the TTA which only changes the angulation of the patellar ligament, the TPLO significantly alters the geometry and distribution of load bearing through the joint. Complications are common; a recent summary of research papers reported that as many as one in three patients are affected.10 Many of these complications that are unique to the TPLO compared to other cruciate repair techniques, with the most severe being a fracture through the weight bearing axis of the tibia resulting in an unstable broken leg.

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Non-Surgical Options

For the vast majority of patients, surgical repair of canine cruciate disease will provide the best results. However, there are situations where surgery is not an option – geriatric patients or other patients with unacceptable anaesthetic risk, or families who are unable to afford surgery. There are also some patients who are able to heal without surgery.

The larger and less physically fit your pet is, the less likely it is that they will heal without surgery. If the stifle joint is grossly unstable, then it is highly unlikely to heal without surgery.

Patients with many of the qualities listed below are the ones most likely to respond to non-surgical (conservative) treatment:

  • Smaller patients (e.g. <12kg)
  • Fit, well muscled patients with no excess body fat
  • Patients that have no future athletic expectations
  • Partial cruciate tears with little pain and no instability of the joint
  • Trauma induced cruciate injury with no genetic predisposition (“true” sports injuries)

 

Non-surgical treatment doesn’t just mean strict rest, although resting the leg is a crucial part of the treatment program. A comprehensive conservative treatment program includes:

  • Prescription medication to control pain and reduce acute inflammation
  • Nutritional supplements to augment healing (oral and injectable)
  • Weight control
  • Exercise modification
  • Personalized rehabilitation program to strengthen and balance supporting structures
  • Address any other neuromuscular or orthopaedic conditions that may be affecting weight distribution and comfort.

 

Even though they know the odds are their pet will eventually need surgery, some owners attempt conservative therapy first, just to be sure. This is especially true for owners that need time to gather the finances needed for surgery, and are wondering what they can do in the meanwhile.

For patients that stand a reasonable chance of responding to conservative therapy (e.g.: small and fit dogs), then non-surgical therapy should be considered the first line treatment.

For those patients for whom surgery is not an option, the above program is also the best way to minimize discomfort and hopefully still achieve a satisfactory lifestyle.

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References

1 Au II, Gordon-Evans WJ, Johnson AL, et al. Comparison of short and long term function and radiographic osteoarthrosis in dogs with naturally occurring cranial cruciate ligament injury receiving postoperative physical therapy and tibial plateau levelling osteotomy or lateral fabellar suture. Proceedings of the Veterinary Orthopaedic Society Annual Conference. Steamboat Springs, CO, 2009, p.14

2 Conzemius MG, Evans RB, Besancon MF, et al. Effect of surgical technique on limb function after surgery for rupture of the cranial cruciate ligament in dogs. J Am Vet Med Assoc 2005; 226: 232-236

3 Cook JL, Luther JK, Beetem J, et al. Clinical comparison of a novel extracapsular stabilization procedure and tibial plateau levelling osteotomy for treatment of cranial cruciate ligament deficiency in dogs. Vet Surg 2010; 39: 315-323

4 Lazar TP, Berry CR, de Haan JJ, et al. Long term radiographic comparison of tibial plateau levelling osteotomy versus extracapsular stabilization for cranial cruciate ligament rupture in the dog. Vet Surg 2005; 34: 133-141

5 Millis DL, Durant A, Headrick J, Weigel JP, Long term kinetic and kinematic comparison of cruciate deficient dogs treated with tibial plateau levelling osteotomy or modified retinacular imbrications technique. Proceedings of the Veterinary Orthopedic Society Annual Conference. Big Sky, MT, 2008, p12

6 Evans, unpublished data 

7 Chauvet AE, Johnson A:, Pijanowski GJ, et al. Evaluation fo fibular head transposition, lateral fabellar suture and conservative treatment of cranial cruciate ligament rupture in large dogs: A retrospective study. J Am Anim Hosp Assoc 1996; 32: 247-255

8 Innes JF, Bacon D, Lynch C, Pollard A. Long-term outcome of surgery for dogs with cranial cruciate ligament deficiency. Vet Rec 2000; 147: 325-328

9 Hulse D, Hyman W, Beale B, et al. Determination of isometric points for placement of a latereal suturen in treatment of the creanial cruciate ligament deficient stifle. Vet Comp Orthop Traumatol 2010; 23:163-167

10 Bergh MS, Peirone B, Vet Comp Orthop Traumatol 2012: prepublished online April 25, 2012