The Tibial Tuberosity Advancement (TTA)
Relative to TPLO, TTA is a newer (ca. 2004), alternative "bone cutting" surgical procedure designed to correct the CrCL deficient stifle and relies upon the patella tendon to provide joint stability. The objective of the TTA is to neutralize tibiofemoral shear force during weight bearing loads.
TTA advances the tibial tuberosity (patella tendon insertion) forward and thereby changes the angle of the patella tendon such that it is perpendicular to the tibial plateau at normal standing angles. This movement may relieve the load required of the CrCL and applies that load to the patella tendon.
During TTA, the tibial tuberosity is cut vertically and moved forward a predetermined distance. The advanced bone is classically, and according to the original described technique, held in place by a titanium "cage", fork and tension band plate. Bone is expected to grow over and through the cage-like spacer and fills the void between the tibia and the advanced tibial tuberosity.
Now for some straight talk on TTA...
- The TTA technique is claimed by some to be less invasive than the TPLO.
FALSE. TTA is a bone-cutting operation that requires a saw to break the bone of the tibia, to move that bone and hold it in place with permanent, metallic orthopedic implants. As such, it is by definition an invasive technique. Ironically, these same practitioners will perform open approaches (arthrotomy) to the knee to treat the torn CrCL and meniscus. Arthrotomy requires much longer and deeper incisions through the muscle of the thigh and joint capsule.
- As with TPLO, the TTA is appropriate for most dogs with a CrCL tear.
FALSE. TTA is not appropriate for dogs with tibial slopes greater than 27-30 degrees. TTA may also not be suitable for large or giant breed dogs because of the limitation in the size/width of the cage implants. Lastly, TTA is not recommended in dogs with normal variations of tibial conformation, viz. a "low" tibial tuberosity.
- TTA presents numerous problems should implants removal be required.
TRUE. New healing bone will grow into and over the TTA cage with time. Should implants removal be required due to pain, loosening, breakage and/or infection, aggressive surgery may be required to extract the cage with the creation of a large and potentially unstable bone defect.
- Be wary of newer and alternative TTA fixation techniques.
TRUE. Certain wedge-like ceramics or ‘biofoams’ have been suggested as a ‘quicker and easier’ alternative to the classical technique. Bone fixation may be limited to a single pin and be grossly inadequate resulting in tibial crest instability, fracture and loss of tuberosity advancement with recurrent joint instability.