Tibial plateau angle

The tibial plateau angle also known as the tibial plateau slope, is a measurement used to assess the amount of inclination of the tibial plateau and provide guidance for correction during tibial plateau levelling osteotomy. It is is determined from a mediolateral radiograph of the tibial. The X-ray beam is centred at the stifle joint, with the normal standing joint angles of the pelvic limb. The mediolateral projection is considered acceptable when the medial condyle and lateral condyle of femur are superimposed.

The most common description of the tibial plateau angle refers to Slocum and Slocum 1993. However, Inauen et al. 2009 proposed another definition

According Slocum and Slocum 1993

The tibial plateau angle is the angle between the proximal tibial joint orientation line and a line drawn perpendicular to the mechanical tibial axis.

The following results have been published by Su et al. 2015 for the tibial plateau angle in various breed of dogs:

Breeds (Number of dogs, number of stifles): Mean TPA +/- SD

• Akita (11): 22.2 +/- 4.0°

• American bulldog (16): 27.6 +/- 2.8°

• American pit bull terrier (12): 30.1 +/- 3.6°

• Australian shepherd (14): 26.9 +/- 2.7°

• Australian terrier (1, 1): 35.1 +/- 1.5°

• Bernese mountain dog (11): 27.8 +/- 4.0°

• Bichon frise (20, 28): 32.6 +/- 4.6°

• Boston terrier (6, 8): 22.2 +/- 2.6°

• Boxer (13): 28.0 +/- 2.9°

• Brussels griffon (1, 1): 15.8 +/- 1.8°

• Bull mastiff (16): 25.8 +/- 4.8°

• Cairn terrier (5, 7): 38.7 +/- 6.0°

• Cavalier King Charles spaniel (6, 8): 25.5 +/- 3.3°

• Chihuahua (7, 7): 25.2 +/- 2.9°

• Doberman pinscher (11): 29.1 +/- 3.6°

• English bulldog (16): 26.4 +/- 3.1°

• English mastiff (13): 25.3 +/- 3.2°

• English toy spaniel (1, 1): 23.1 +/- 1.5°

• German shepherd dog (11): 25.2 +/- 2.8°

• Golden retriever (13): 25.2 +/- 4.0°

• Great dane (12): 30.0 +/- 3.8°

• Great Pyrenees (13): 29.2 +/- 5.7°

• Havanese (2, 2): 23.1 +/- 1.6°

• Jack Russell terrier (10, 11): 27.5 +/- 3.6°

• Labrador retriever (11): 28.1 +/- 2.6°

• Lhasa apso (1, 1): 32.3 +/- 1.9°

• Maltese dog (5, 7): 30.6 +/- 2.6°

• Miniature pinscher (1, 2): 22.2 +/- 0.8°

• Miniature poodle (2, 3): 30.2 +/- 2.8°

• Miniature schnauzer (4, 4): 29.4 +/- 1.4°

• Newfoundland (18): 28.6 +/- 3.4°

• Norwich terrier (1, 1): 36.3 +/- 0.9°

• Papillon (2, 3): 29.8 +/- 2.9°

• Pekingese (1, 2): 27.8 +/- 5.6°

• Pomeranian (8, 12): 22.4 +/- 3.7°

• Pug (2, 2): 24.1 +/- 2.8°

• Rat terrier (1, 1): 35.6 +/- 0.9°

• Rottweiler (12): 24.6 +/- 1.9°

• Saint Bernard (16): 30.6 +/- 4.2°

• Shetland sheepdog (11, 12): 27.6 +/- 4.6°

• Shiba inu (1, 1): 29.1 6+/-3.4°

• Shih tzu (6, 9): 25.9 +/- 3.7°

• Siberian husky (13): 29.5 +/- 2.7°

• Silky terrier (1, 2): 32.5 +/- 2.3°

• Toy fox terrier (2, 2): 23.7 +/- 0.3°

• Toy poodle (5, 6): 28.4 +/- 5.3°

• Weimaraner (13): 29.5 +/- 5.2°

• West Highland white terrier (7, 7): 40.4 +/- 2.8°

• Wire haired fox terrier (1, 2): 26.3 +/- 0.5°

• Yorkshire terrier (25, 32): 28.7 +/- 5.0°

According to Inauen et al. 2009

The following points are identified:

• A = most cranial point of the proximal articular surface;

• B = midpoint between the caudal parts of the articular surfaces of the lateral condyle and medial condyle of the tibia.

• C = most proximal point of the cranial border of the tibia;

The tibial plateau angle is the angle formed by the lines AB and BC

Inauen et al. 2009 found that the tibial plateau angle was 33.6+/-3.7° in healthy dogs.