Triple Tibial Osteotomy (TTO)

Triple Tibial Osteotomy (TTO)

By changing the geometry of the forces and muscle contractions that at on the stifle during weight bearing, TTO aims to neutralize the shear force that causes the cranial movement of the tibia with respect to the femur.

Shear force develops because the dog's tibial plateau - the weight bearing surface 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 tendon.

In the TTO procedure, three distinct osteotomies (saw cuts into the bone) are performed to adjust the tibial slope so that it is aligned at right angles to the patellar tendon - as with the TTA - instead of sloping backwards. By this approach, shear forces within the joint are neutralized and the joint is stable as the dog bears weight.

The TTO procedure had been developed as a hybrid of the two previously reviewed techniques - the Tibial Tuberosity Advancement (TTA) and the Tibial Plateau Leveling Osteotomy (TPLO). The TTA neutralizes shear force within the stifle by advancing the tibial tuberosity until the tibial plateau is at right angles to the patellar tendon. The TPLO neutralizes shear forces by rotating the tibial plateau so that it is approximately horizontal (5-6 degrees) with respect to the long axis of the tibia. The TTO combines these very different approaches and, as such, less radical bone excursions are theoretically required.

The TTO involves removing a small, horizontal wedge of bone (average 12 degrees) halfway along a vertical osteotomy in the tibial tuberosity (as with TTA). By removing this wedge of bone and "closing" of the resulting horizontal defect, the tibial plateau may be levelled and the tibial tuberosity advanced simultaneously. The end result yields an average of 20 degrees of tibial plateau leveling as with the TPLO and approximately 9-12 mm of tibial tuberosity advancement like TTA.