What Is A Cruciate Ligament?
You’ve probably heard of anterior cruciate ligament injury in human sports, and in fact dogs are very similar.
There are actually two cruciate ligaments in each knee: cranial & caudal (or anterior & posterior). As the name suggests, they cross over inside the joint. Their job is to stop the bones above and below from sliding forwards or backwards when the stifle is weight bearing.
An odd feature of the canine stifle (knee) is that the weight bearing surface (the tibial plateau) slopes backwards at an angle. Whenever a dog puts weight on their knee the cranial cruciate ligament must therefore take the strain. It’s like parking a car on a slope and relying on the handbrake to keep it there. If it fails, the tibia slides forwards and the joint capsule is stretched.
We call this motion tibial thrust or cranial drawer, and it hurts! It’s why when a cruciate ligament is ruptured a dog won’t put much weight on the leg.
Signs Of Cruciate Rupture
A cruciate ligament usually ruptures in the course of normal activities. For example, a dog will be running along and suddenly lift the hind leg and start limping. Sometimes they will yelp but there is often no obvious cause. After the injury, the leg does not appear painful as long as the dog avoids full weightbearing.
Why Do Dogs Rupture Their Cruciate?
We don’t know! It’s almost never a sporting injury like in humans. In dogs we talk about ‘cruciate ligament disease’ not ‘cruciate ligament rupture’. There are a number of factors that seem to be important:
- Genetics: some breeds are much more likely to do it than others
- Weight: overweight dogs are more likely to rupture cruciate ligaments
- Age: it seems to be a degenerative process with a peak at 6 to 8 years of age
- Age of desexing may matter for Golden Retrievers, Labradors and German Shepherds.
These factors explain why dogs who rupture their ligaments often do it without any special activity. This also explains why dogs that rupture one are very likely to rupture the second within a few years. It’s important to have the first leg back in full function before this happens.
How Common Is Cruciate Ligament Injury?
- The number one cause of chronic hind limb lameness
- The most common orthopaedic surgery of dogs
- The leading cause of stifle arthritis
A week would not go by at Walkerville Vet without a new diagnosis. Each of these will join the many other dogs who are living with the effects of this condition.
Do All Dogs Need Cruciate Surgery?
No. Sometimes, usually only for dogs under 10kg bodyweight who aren’t especially active, there can be a return to normal leg use without surgery. If this is going to happen it will usually occur within 4 weeks.
If you wish to try this we strongly advise a course of pentosan polysulphate injections. However, please note that recoveries without surgery are rare, and there is an increased risk of meniscal cartilage damage in dogs when surgery is delayed.
How Do We Repair Cruciate Ligaments?
Dogs with cruciate ligament rupture almost always require surgery. Some small dogs can get adequate return to function with other treatments, but these are rare.
All dogs who have suffered a cruciate ligament rupture will develop arthritis in that knee. In fact, many already have significant arthritis at the time of diagnosis. Our job is to:
- Stabilise the joint
- Treat the arthritis
Which Cruciate Procedure Is Best For Small Dogs?
Most dogs under 15kg currently receive extra capsular techniques, which produce good outcomes. You can expect your dog’s limp to disappear once they recover from surgery.
TPLO and other osteotomy procedures are only commonly performed on large dogs. Emerging evidence such as Barnes et al (2016) suggests that TPLO will become the standard of care for all sizes of dog with cruciate injuries. Watch this space…
Which Cruciate Surgery Is Best For Large Dogs?
There is a wide range of surgical procedures developed to treat cruciate injuries in dogs. For a long time we had no good evidence for whether to do one or the other.
It is now clear that they are not equal. Techniques using existing ligaments or other internal stabilisations are highly prone to failure. These have fallen out of favour, like Fibular Head Transposition, Paatsama fascial strip, Over-The-Top patella tendon graft & Under and Over fascial replacement technique. An earlier tibial osteotomy procedure, Tibial Closing Wedge Osteotomy, is no longer performed as well.
Whichever procedure is chosen, complications are always possible. These can include infection, implant loosening or failure, fracture at the implant site or secondary damage to the meniscal cartilages (‘meniscus’ on diagram).
Complications are reduced by closely following your vet’s recommendations for postoperative care.
The following cruciate surgeries are still in use in Adelaide. Here are our views on each technique.
Extra Capsular Repair or De Angelis Technique
A nylon, polyester or stainless steel suture is placed around the outside of the joint in the same alignment as the cranial cruciate ligament.
ECR is technically the easiest procedure to perform, and results appear very good for small dogs. However active medium and large dogs appear to do poorly and rarely achieve full return to function.
Recent data supports this. In a clinical study using pressure plate analysis to measure leg use (rather than relying on owner and vet impressions), only 40% of animals treated with ECR improved and only 15% returned to normal function. Complications are more likely in younger and larger dogs.
Tibial Osteotomy Techniques
The latest developments in improved surgical outcomes for dogs with cruciate ligament rupture are the techniques involving reshaping the proximal tibia. We believe that all dogs over 20kg should now receive one of these techniques. While most specialists now agree that the TPLO is better, any of these will produce good results in experienced hands.
Tibial Tuberosity Advancement (TTA)
A cut is made in the front of the shin bone (tibia) and a wedge inserted to move the point of attachment of the kneecap tendon forward. This creates a force opposing the forward movement of the tibia.
The MMP or Modified Maquet Procedure is a proprietary version of the TTA approach and is presumed to share its strengths and weaknesses.
This is a good technique. It appears to have a higher rate of late-onset meniscal tears (requiring a second surgery) and in comparisons with TPLO (see later), has a lower rate of return to full function (Christopher et al, 2013, Cook, 2016). There is also a low risk of tibial fracture.
Triple Tibial Osteotomy (TTO)
This is a hybrid procedure involving a degree of tibial tuberosity advancement together with the removal of a wedge of bone from the tibia to reduce the tibial plateau angle. A large plate and screws is necessary to hold the repair together.
Although less common, TTO is likely to be a good procedure much like TTA. Unfortunately there is very little evidence in the form of studies comparing this technique to the others available.
Tibial Plateau Levelling Osteotomy (TPLO)
The aim of TPLO is to reduce the angle of the tibial plateau. After successful surgery, tibial thrust and joint capsule stretching should not happen during weightbearing.
The surgery involves a curved or radial cut which avoids the patellar tendon but includes the entire tibia plateau. The plateau is then rotated by a pre-measured amount and a specially designed plate and screws are placed to hold the tibial plateau at its new angle.
These days TPLO has become one of the most researched surgical procedures in veterinary medicine. A majority of specialists now consider TPLO to be most likely to return dogs to full function and give the lowest complication rates (Christopher et al, 2013; Gordon-Evans et al, 2013; Krotscheck et al, 2016)
Our results lead us to believe that the TPLO is a more appropriate recommendation for active patients, if not for all patients considering an osteotomy procedure. As there are no differences at the trot between TTA and ECR, surgeons should consider carefully which of these procedures is preferable when taking into account client cost and surgical risk. (Krotscheck et al, 2016)
Based on the evidence, Walkerville Vet has started offering TPLO procedures to our Adelaide patients. Visit our page on what to expect when your dog has TPLO cruciate surgery.
Managing Stifle Arthritis
No matter how good the surgeon or the technique, dogs who damage or rupture their ACL will always develop arthritis in that knee. It seems clear that the newer techniques reduce its severity, not prevent it.
Barnes, D. C., Trinterud, T., Owen, M. R., & Bush, M. A. (2016). Short‐term outcome and complications of TPLO using anatomically contoured locking compression plates in small/medium‐breed dogs with “excessive” tibial plateau angle. Journal of Small Animal Practice, 57(6), 305-310.
Christopher, S. A., Beetem, J., & Cook, J. L. (2013). Comparison of long‐term outcomes associated with three surgical techniques for treatment of cranial cruciate ligament disease in dogs. Veterinary Surgery, 42(3), 329-334.
Gordon-Evans, W. J., Griffon, D. J., Bubb, C., Knap, K. M., Sullivan, M., & Evans, R. B. (2013). Comparison of lateral fabellar suture and tibial plateau leveling osteotomy techniques for treatment of dogs with cranial cruciate ligament disease. Journal of the American Veterinary Medical Association, 243(5), 675-680.
Krotscheck, U., Nelson, S. A., Todhunter, R. J., Stone, M., & Zhang, Z. (2016). Long Term Functional Outcome of Tibial Tuberosity Advancement vs. Tibial Plateau Leveling Osteotomy and Extracapsular Repair in a Heterogeneous Population of Dogs. Veterinary Surgery.