Cruciate ligament injury

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1 Cruciate ligament injury This is an extremely common injury in dogs, less so in cats. Let s start by looking at the anatomy of the stifle (knee) joint of the dog.

2 The important differences between the dog and the human essentially relate to how they stand. Look at any dog from the side, and you will see the stifle joint is slightly bent, or flexed, whereas a standing human has a completely straight knee joint. The result of this stance is that when the dog puts weight on the leg, the weight runs behind the stifle joint, and results in a force pushing the lower leg forwards. We call the direction towards the front of the dog cranial, so this force is called the cranial tibial thrust (CTT), since it acts on the tibia.

3 What stops the lower leg moving forwards in response to this CTT is the cranial cruciate ligament (CCL), which lies inside the stifle joint and runs in this direction. There is also a caudal cruciate ligament, which runs in the opposite direction, and prevents the lower leg moving backwards, or caudally. This ligament is much less important than the crania one. There are also two collateral ligaments, the medial and the lateral collaterals. These can also be damaged. Rupture of the CCL is a result of excessive force on the ligament, either caused by over extension of the stifle joint or inward rotation of the lower leg when the joint is flexed. These conditions occur most frequently when: The dog jumps a fence and gets its foot caught on the top, resulting in sudden hyperextension of the stifle joint Puts the foot down a hole in the ground while running Sudden braking to a halt when chasing a thrown object Leaping into the air and landing with a flexed leg while twisting The majority of CCL ruptures in dogs occur in animals which already have arthritis in the joint and the force needed to snap the ligament is much less than a healthy joint. There are some risk factors which lead to degeneration in the joint and increase the risk of CCL rupture: Dislocating patella (kneecap). This is the most common cause of CCL in small breed dogs. Untreated dislocating patella dogs have a 25% chance of rupturing their CCL

4 Excessively straight stifle joint Tibial plateau slopes downwards excessively. What is the tibial plateau? This is the articular surface of the tibia, and the slope it makes relative to the long axis of the leg can be measured on x-rays. If the tibial plateau slopes steeply down at the back, it increases the cranial tibial thrust, thus putting more pressure on the CCL and leading to degeneration and ultimately rupture. Note that many dogs have partial rupture of the CCL, resulting in varying degrees of lameness. These almost all progress to full rupture in time, and are generally treated the same way. Rupture of the CCL will result in lameness, often sudden in onset but not always. There is a degree of joint swelling detected, and pain on manipulation, but this can reduce significantly in the first few days. The diagnosis is made by performing a couple of physical tests called the cranial draw test, and the tibial compression test. These look to see if there is a looseness in the joint suggesting the ligament has snapped. There may also be a loud clicking noise noticed. This is called a meniscal click, and is commonly associated with damage to the meniscal cartilages in the joint.

5 X-ray does not show the ligament or cartilages. It will normally show increased fluid in the joint if there is damage, and will show arthritic changes if present. X-ray is also used to measure the tibial plateau angle to see what form of surgery is best for the patient. Treatment The essential fact is that most patients do much better with surgery than without it, and that fact becomes critically important as the patient gets larger. There are some patients under 10kg who can do reasonably well without surgery, once the joint has fibrosed enough to provide the support that the CCL used to supply. But this does not remove torn cartilage which remains a source of significant pain for the patient. There are a very large number of procedures developed for treating this injury. Each surgeon has their preferences. It is simple to consider the operations as falling into two main groups. Extracapsular support This involves placing some form of prosthetic ligament in the leg to prevent the cranial tibial thrust movement from sliding the lower leg forwards when weight-bearing. There are a variety of materials that can be used, from nylon leader line, to FibreWire, or Ligafiber. They can be anchored either around the fabella at the back of the joint, or attached to the bone with special screws. They can be tied, or joined with stainless steel crimps. There is a very wide range of options available. This surgery works well for small dogs. For dogs over about 15kg it is less effective, and for larger dogs it is commonly not effective.

6 Tibial plateau levelling and tibial tuberosity advancement These procedures approach the problem from a completely different angle. The basis of them is that some kind of saw cut or cuts are made to the tibia, so that either the tibial plateau is rotated downwards at the front of the joint, or the tibial crest is levered forwards. The result is a change in the angle between the tibial plateau and either the long axis of the bone (TPLO surgery) or the front of the patellar tendon (TTO or TTA surgery). This means that when the dog puts weight on the limb, there is no cranial tibial thrust, so there is no need for a CCL anymore. These are more complex procedures, but the results in normally dramatically better than the older extracapsular options. The benefits of these procedures are: Faster return to weight-bearing on the leg Less muscle wasting Faster reduction in pain Faster return to full range of motion in the stifle Both stifles can be operated on a week apart or less in cases with bilateral rupture Much easier physiotherapy post-surgery and better results A dog with a severely sloped tibial plateau will need major correction of the slope, and for that we perform a triple tibial osteotomy (TTO), while a dog with a less severely sloped tibia will have an Ossability tibial tuberosity advancement (TTA).

7 Some surgeons perform the original operation in this group, the tibial plateau levelling osteotomy (TPLO). This produces results no better than the TTO or TTA, and both of these procedures are faster to learn and have a lower rate of complications.

8 There are many versions of the TTA procedure as well. We chose the Ossability TTA as the implant stability is vastly superior to any of the other versions, and the complication rate is dramatically reduced. We have been performing this operation since 2015 and have been extremely impressed with the speed of recovery. We are aware there are cheaper versions of the TTA procedure available, but they are not using the 3D-printed titanium wedge implant, which is what gives this procedure such unrivalled stability. Some dogs and cats will rupture more than just the CCL, and may snap one or both collateral ligaments and even the caudal cruciate as well (multiligament stifle injury). These cases are a challenge as each ligament needs reconstructing individually during the surgery. Recovery can be prolonged but results can still be good. Cats are another challenge, partly because the bones and ligaments are so small, and partly because the fabella in cats cannot easily be used as an anchor point as it is so mobile. This means bone anchors are essential in cats for extracapsular surgery. Cats will sometimes do a multiligament injury as well. So what are our take home messages about cruciate injury in dogs and cats? This is s surgical condition, in which the best chance of a good outcome is always going to be from surgery. There are multiple options available for treating these patients, and prices can vary enormously. We recommend TTO or TTA surgery for patients over about 15kg, and extracapsular surgery for those under 15kg. There are some small dogs whose tibial plateau is sloped so steeply that extracapsular surgery will not work, and these may need a tibial plateau operation as well.

9 Pre-surgical preparation There are some things that need to be done before surgery can take place. The first is a full clinical assessment of the patient as a whole. This is going to include blood testing, and of course xrays for planning which surgery will be best for your patient. Some of these tests may have been done prior to referral to us, which is fine, and we are not then going to need to repeat them. This will reduce your costs. The blood and urine lab tests required pre-surgery include biochemistry (normally a 6- or 10-test panel), electrolytes, a complete blood count, urine specific gravity, and urinalysis. The xrays must include a perfectly positioned lateral view of the joint. This is not always easy to obtain, and if the images are not suitable we may have to repeat them. This is all done under the same anaesthetic as the surgery. Post-surgical care We have a detailed exercise plan for patients to follow after surgery. Alternatively, you may choose to seek advice from a physiotherapist. We have Total Physiotherapy now providing veterinary physiotherapy on-site at our Pukekohe clinic 3 days per week, and they can provide a full package for physio care after cruciate ligament surgery.