Tibial Tuberosity Transposition (TTT)
a surgical procedure used to return normal function of knees in dogs and cats that suffer from patella luxation (trick knees).
This condition is most often seen in miniature breeds of dogs, but can be seen in large dogs and cats as well. The most common clinical sign displayed by pets suffering from patella luxation is stretching their rear limbs straight out behind them immediately after they get up from lying down, other common signs are a reluctance to jump up, a knee that is rotated outward when walking and a popping or movement of the patella (knee cap) while walking. The condition is defined as Medial Patellar Luxation (MPL) if the knee cap is riding on the inside of the knee or Lateral Patellar Luxation (LPL) if the knee cap is riding on the outside of the knee.
- Most likely to occur in small or miniature breeds for dogs and some larger breeds, i.e. Labrador Retrievers; occasionally Domestic shorthair cats
- Symptoms are slight but include dislocation of the patella (kneecap) in varying degrees:
- Grade I: carrying of the leg occasionally, skipping or hopping
- Grade II: joint becomes dislocated more often, crepitus (crackling) can be heard in joint, DJD can set in
- Grade III: permanent dislocation, still may be weight bearing however may appear to be bowlegged
- Grade IV: permanent luxation, carrying the leg all the time
In approximately half of all cases, both knees require correction. The condition is usually hereditary and becomes evident at a young age. Occasionally patella luxation can result from traumatic injury to the knee which causes sudden lameness and hinders weight-bearing ability. In cases where no trauma has occurred, the femoral groove (trochlear groove) is usually either very shallow or absent. There is no single cause for patellar luxation, but the corrective surgery is highly successful with little incidence of complication.
Surgical correction of patella luxation in cats and dogs begins with improving the alignment of the patella mechanism with tibial tuberosity transposition. In dogs that are more severely affected the trochlear groove can be reconstructed with block recession trochleoplasty, in extreme cases corrective osteotomies of the femur or tibia must be completed. The severity of patella luxation is graded from I-IV, most general practitioners are comfortable diagnosing this condition and will then recommend surgery be completed by a board certified veterinary orthopedic surgical specialist, like Dr. Dew, due to the small size of the patients and the technical nature of the procedure.