WL PETS CORNER
CRUCIATE LIGAMENT
INJURY IN THE DOG
by Dugie Gemmill, Parkside Veterinary Practice
Given the seismic shift in the foundations of our lives and community
in recent 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 both I, or my son Finn had ever attempted! Important
facts initially – my time was nine minutes faster than I had predicted,
and quite respectable, and 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
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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!
Dugie is a graduate of Glasgow University and has worked at Parkside
Veterinary Practice since 1990 and has been the Clinical Director for the
last seven years. He has a keen interest in laparoscopic and orthopaedic
surgery.