TPLO - TTA, and other Advanced orthopaedic procedures

These procedures have been done at Phoenix Vets by Ian M B Simpson BVSc CertSAO MRCVS AVP for many many years, but Ian has now moved on to Lumbry Park Veterinary Specialists , a first class facility just outside of Alton in Hampshire.  He would be happy to see your orthopaedic referral cases there if you would like to be sent there,  by referral from your own vets .  Lumbry Park can be contacted directly on (01420) 481777

 

If you would like to understand TPLO in greater depth, please find a detailed overview we have written for you below.

 

TPLO – a detailed overview

TPLO stands for Tibial Plateau Levelling Osteotomy, and is a method of helping to improve functionality in a dog’s knee joint or stifle, following damage to the cranial cruciate ligament. The procedure was invented in the 1980s by Barclay Slocum, an American surgeon, who first recognised the forces involved in predisposing the dog’s knee to cruciate injury. As cruciate injury is extremely common in domestic dogs, and over one hundred methods of surgical repair are already described. This new method was welcomed, initially with reservation, by the orthopaedic veterinary community worldwide. Nowadays, the procedure is seen as a valuable part of treatment options available to help your dog with cruciate disease.

Causes Of Cruciate Disease

Image showing cross section of dogs knee showing ligaments

Dogs who present with ruptured, partially ruptured or torn cruciate ligaments are usually partially or totally lame on the affected limb. The history is commonly of over-exertion, especially involving jumping, or twisting, and perhaps landing awkwardly. In people, this ligament is also commonly damaged, typically by skiers or footballers. These injuries are due to a high build-up of pressure in the knee while performing the relevant sport, and then suddenly loading the ligament beyond its elastic capability through twisting or stretching it, which leads to a non-elastic failure, resulting in permanent stretching, or complete rupture. A human cruciate ligament is around 12mm in cross section. A dog’s cruciate ligament is between 3mm and 8mm depending on the breed and size. No one breed is more predisposed to this problem than another, though one does tend to get more forces in a larger dog, for obvious reasons so larger dogs do seem to suffer from this most commonly. This does not mean that small dogs do not get cruciate disease, as Jack Russells, West Highland White Terriers and Yorkshire terriers are all regular candidates for corrective surgery to their knees.

Methods Of Repair

 

As mentioned there are a large number of different ways of dealing with this disease. Old and outdated methods include injection of blood into the joint, which was supposed to invoke a fibrous scar tissue reaction within the joint and thus stabilise things without much intervention of the surgeon. This method could possibly be likened to using a chocolate teapot.

Lateral view of cross section of dogs knee showing ligaments

Various materials have been used to replace the broken part over the years, since cruciate damage was first addressed surgically in the dog in the 1950s. The ligament itself is made of collagen fibres, which are very strong parallel fibres, connecting bone to bone, and very strong in tension, but less so in shear or compression. Collagen has a very low elasticity, which makes it useful as a ligament, but also makes it unforgiving and prone to failure in sudden high-loading situations (see above). Over the years, veterinary surgeons have tried to replace the broken ligament using skin, (too elastic and prone to infection) fascia (a muscle sheath) – also too elastic, and prone to losing its blood supply and thus dying and failing. Tendon – a good material, though needing harvesting from other areas on the body, thus further trauma and damage to the patient, and also prone to necrotising (dying off) due to lack of blood supply.

Synthetic materials have also been used, including catgut, linen, silk, polyester fibre, carbon fibre, stainless steel, and nylon. These all have advantages and disadvantages, with single-filament nylon probably being the most successful, due to its zero reactive capacity within body tissues, but retaining a degree of elasticity and flexibility. Steel wire works well as it has high tensile strength and does not stretch, but does tend to fail due to metal fatigue, usually around six months after implantation.

How Does The Repair Work?

 

All the methods described using various materials above are used to try and limit the unstable and abnormal moment and instability in the stifle joint. When the cruciate ligament breaks, the tibia is allowed to slip forwards relative to the femur, and this movement, which is known as “Cranial Drawer Movement” can be detected by your veterinary surgeon, normally in a conscious dog, but more easily under general anaesthetic or deep sedation when the muscles are far more relaxed. The aim of the conventional repair methods is to limit or stop this movement, to allow the knee to function more normally again. This works well if the cause of the initial injury is an overload on the ligament and not the actual shape of the knee. If the top of the tibia is sloped backwards to any significant degree, then the cruciate ligament or any material designed to replace it, is fighting a losing battle. This can be likened to setting a handbrake on a car left in neutral. If the car is on a hill, the handbrake wire is in constant tension and has to work hard to stop the car rolling down the hill. If the car is on a flat piece of ground, the handbrake wire doesn’t have to do too much work – just resist any movement induced in the vehicle by, perhaps being pushed.

Image of dogs knee showing leg at two different angles

The idea of the TPLO or tibial plateau levelling procedure is to take the hill out of the equation, so that the ligament has far less work to do.

TPLO Or Non-TPLO ?

Not all cases of cruciate rupture in the dog require a TPLO. Whjere there is minimal angulation to the tibia, there is no point in changing the angle through what is quite an involved procedure, when a more simple procedure will do. In our clinic we do both conventional and TPLO procedures and try to make a sensible judgement as to which has the greater possibility of success in each individual patient, fully engaging the owner in this decision process. Measurement of the angle, and examining the cause of the injury are the major factors which determine the method to be used.

The TPLO Method

X ray image of TPLO operation on dogs knee

Again, several ways of achieving the same thing are described. The aim of all of them is to level the plateau, or table-top part of the tibia, or shin bone, to reduce or neutralise the forces acting on the cruciate ligament. This is achieved either by cutting free a cylindrical section of bone and rotating it forwards, or cutting a wedge shaped piece of bone out of the tibia and closing the wedge shaped defect together to achieve the same effect. Recently, more complex methods of sectioning the tibia, such as triple tibial Osteotomy have been proposed, which add to the complexity but may not necessarily improve the final outcome.

The Operation

Image of drawing showing TPLO operation before and after

A most important part of any operation to sort out cruciate disease is to remove the remnants of the broken ligament in its entirety because, if this is not done, these will start turning to bone within the joint, causing extreme pain and discomfort over time. Equally, the meniscal cartilages must also be checked and damaged sections removed, or these too will become ossified, and form “pebbles” or joint mice, within the knee joint which will prevent a proper pain-free recovery. This may be achieved by opening the joint surgically and removing the damaged tissues, or by arthroscopy. The disadvantage of surgery is the added trauma of the approach and dissection, the disadvantage of arthroiscopy, is the potential to be unable to remove all the tissues adequately enough to give an improvement to the function. On balance a surgical approach gives better exposure and allows a far more thorough tidy up and correction of problems within the joint.

The tibia is then cut and repaired in its new shape, reducing the slope of the plateaus. The repair is usually achieved with a plate and screws, which looks like a small piece of meccano, normally specially designed to fit the individual dog’s tibia.

Image of  metal plate used in the TPLO operation

Sometimes an extra piece of wire is used for added stability, and sometimes the whole fixation is achieved with an external fixator, which is an external frame, though this is unusal.

Recovery

Picture of dog with bandage on leg

Dogs are naturally rather painful after these procedures and we like to use strong painkillers given through a drip line while they are in hospital. Normally an overnight stay afterwards is a good idea to allow further infusion of pain relief and to monitor the recovery. After the first day, patients can normally be switched on to tablet or oral fluid pain relief, for the next 7-10days. Skin sutures are removed at ten days and we expect the patient to start using the leg by six weeks post-operatively. Sometimes this can be a lot quicker, from as little as two days, and sometimes it can take a lot longer.

Aftercare

Picture of dog doing hydrotherapy

The longer a limb is immobilised the greater the chance of stiffening up due to fibrosis (scarring inside the limb) building up. We like to encourage early return to function through sensible and cautious exercise as early as possible after the operation. Walking on a short lead for ten minutes five or six times daily is important as it encourages the dog to use the leg, more than allowing unrestricted running around. Sometimes use of the lead in the house too can be beneficial, as it again limits sudden movemts and running, during which dogs tend not to try and use the operated limb as much. Hydrotherapy and physiotherapy after the TPLO operation are excellent too, and helping to restore the natural function and range of movement to the limb.

Longterm Prognosis

Generally this should be good, though certain factors do play a role in determining how good the end result will be. If the cruciate has been damaged for some time before operating, more permanent damage could have resulted in the knee, which may not resolve, even with the surgery. Complications including infection, breakage of the plate or loosening of the screws can occur but are rare. A degree of degenerative joint disease or osteoarthrosis, is inevitable with any surgery to a joint, and the more traumatic the surgery, the more likely this is to occur. An experienced surgeon will cause far less trauma to the joint than an inexperienced one, in general. The endpoint aim of any surgical procedure is to improve function for the patient to better than it was before the procedure. This may seem a simple statement but it is amazing how many owners are duped into having their pets operated on without good cause, and end up with only a marginal improvement, or even worse, a deterioration in function following surgery.