Given the seismic shift in the foundations of our lives and community in these COVID19 times, the eighth of March seems like a date from an ancient history class. However, it was the day of the 2020 Chester 10km Road Race. The first 10k that either I, or my son Finn had ever attempted! Important facts initially – my time was nine minutes faster than I had predicted, and quite respectable. Finn did the decent thing and let his old man finish first! What on earth has this to do with the world of Veterinary Surgery? When I run, my mind tends to drift off and given that I was pushing myself at about the 8km mark going uphill towards the city centre, I began to tick off my list of personal rugby-related injuries – from Achilles tendon tears, to sutured forehead and lip, subluxated shoulder, broken nose (twice – first time it was crooked and the second reset it!) and finally to a hip resurfacing procedure. As I ran, despite this extensive list, I decided that in a bizarre way I had dodged the proverbial bullet by avoiding a most common football and rugby injury – the ruptured cruciate ligament!
Known as an anterior cruciate ligament (ACL) injury in people, rupture of the cranial cruciate ligament (CCL) is incredibly common in dogs. In part this is because the average dog even if a canine couch potato, would be an accomplished amateur athlete in the human world. However, we frequently see the injury much more in some breeds of dog than others, particularly medium and large breeds, sometimes as young as eight months of age – a common patient is the Labrador Retriever.
The knee should only move in the manner of a hinge, but because it is often under stress through a range of angles from fully straight (extension) to bent (flexion), it contains an array of structures to combat these forces. Effectively the cranial cruciate ligament exists to keep the tibia (the shin bone) and the femur (the thigh bone) in a predictable position relative to one another. When the CCL is torn, partially or completely, then the tibia tends to slide forwards in respect to the femur. The resulting lameness varies from subtle, to the dog only touching its toes to the ground – due in part to the sense of instability as the patient tries to put weight through the leg, and in part to the inflammation and swelling in the joint. There are also two discs of cartilage between the femur and tibia which act to stabilise the bones rather like a chock behind a wheel. The inner one (the medial meniscus) is commonly damaged along with the cruciate ligament.
It is accepted that nearly all dogs will benefit from surgical treatment of a cruciate related lameness, however small dogs can make a reasonable recovery with rest, anti-inflammatories, then physiotherapy – although recovery time can be protracted. Surgical treatment of the injury is often the best option. Traditionally the instability within the knee was addressed by direct stabilisation using a variety of materials to replace the function of the ligament. These could be grafts of tissue harvested from the knee area, or synthetic material. These standard procedures served us well for many years, but it is recognised that these ligament replacements may stretch or fail completely leaving the knee joint unstable. Recovery can sometimes be quite protracted. We now recognise that we can neutralise the forces within the knee that drive the tibia forwards by altering the shape of the tibia itself. There are several procedures used by surgeons to accomplish this: TPLO (tibial plateau levelling osteotomy) and the TTA (tibial tubercle advancement) are the principle ones. It is also important to inspect and treat the medial meniscus, if damaged, at the time of surgery.
In the TTA, the front of the tibia where the patellar or knee-cap tendon attaches is moved forwards by a distance measured on digital radiographs. The bone is then held in place using a cage and screws, or a cage and plate. Although uncommon, complications can occur which can include infection, further damage to the meniscus, persistent instability or fracture.
While injury to the cruciate ligament in people or dogs is a serious occurrence, in the veterinary world as with human orthopaedics, surgical treatment performed by a surgeon experienced in the techniques can give great results and patients will often return to their sporting life!