Overview
The scapula is a flat, roughly triangular bone lying against the lateral surface of the first ribs. Its dorsal border is extended by the scapular cartilage. Because the dog has no functional clavicle, the thoracic limb is attached to the trunk by a synsarcosis: the scapula hangs from the serratus ventralis, trapezius, rhomboideus and pectoral muscles, which gives the shoulder a wide range of motion.
Key features
- Spine of the scapula (spina scapulae): ridge dividing the lateral surface into the supraspinous and infraspinous fossae, where the muscles of the same names originate. It ends in the acromion, palpable in the live animal and a landmark for shoulder arthrocentesis.
- Glenoid cavity (cavitas glenoidalis): shallow articular surface that receives the head of the humerus. Shoulder stability depends mostly on soft tissues.
- Supraglenoid tubercle: origin of the biceps brachii muscle.
- Neck and caudal border: the caudal border is thick and palpable; the cranial border is thin.
Clinical relevance
Scapular fractures are uncommon and usually follow major trauma. Osteochondrosis (OCD) of the humeral head affects the shoulder joint in young large-breed dogs. The acromion and spine are landmarks for nerve blocks and injections.