Surgical Rationale
The triple tibial osteotomy was developed by a New Zealand veterinary orthopaedic specialist, Dr. Warrick Bruce, while he was working in Adelaide, South Australia. By changing the geometry of the forces of gravity and muscle contractions that act on the stifle during weight-bearing, it aims to neutralise the shear force that causes the cranial movement of the tibia with respect to the femur.
This shear force develops because the canine tibial plateau – the weight-bearing aspect of the joint – is sloped caudally (downwards towards the back of the joint)and there is an acute angle between the tibial plateau slope and the patellar ligament. In the TTO procedure, the tibia has three osteotomies (cuts into the bone with a bone saw) performed upon it with the aim of realigning the tibial plateau slope so that it ultimately becomes aligned at right angles to the patellar ligament instead of sloping backwards. By achieving this, shear forces within the joint are neutralised and the joint is stable as the dog weight-bears.
The joint is not stable, however, when it is physically manipulated by attempting to move the tibia cranially.This contrasts with previous methods of CrCL repair which aimed to provide stability to the joint by replacing the ligament either with a fascial graft within the joint, or using a prosthesis made of nylon placed externally from the lateral fabella to a hole drilled in the tibial crest.
The TTO procedure has been developed as a hybrid of two previously available orthopaedic procedures, the tibial tuberosity advancement (TTA) and the tibial plateau leveling osteotomy (TPLO). The TTA neutralises shear force within the stifle by advancing the tibial tuberosity until the tibial plateau is at right angles to the patellar ligament. The TPLO neutralises shear force by rotating the tibial plateau so that it is approximately horizontal with respect to the long axis of the tibia. The TTO combines both of these procedures and as such less radical changes than either are required.
Read more about this topic: Triple Tibial Osteotomy
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