Humerus
The humerus is the bone of the upper arm. It articulates proximally with the scapula to form the shoulder joint and distally with the radius and ulna to form the elbow. Compared with the lower limb bones it is relatively short. Important landmarks include the deltoid tuberosity and the musculospiral (spiral) groove where the radial nerve wraps around the bone. The bone provides leverage for the large muscles of the shoulder and arm and forms the proximal joints of the forelimb. Because the humerus is covered by thick muscle, fractures are hard to image with plain radiographs and difficult to stabilize. Humeral fractures are most common in foals and in racehorses. Radial-nerve damage is a frequent complication because the nerve lies in the spiral groove; paralysis produces a dropped elbow and inability to extend the limb.
Origin: N/A (bone)
Insertion: N/A (bone)
Action: Provides leverage for forelimb movement; forms the shoulder and elbow joints
Adult humeral fractures carry a poor prognosis. Foals have a better chance of successful repair. Radial-nerve paralysis can accompany the fracture or occur independently from trauma or prolonged lateral recumbency under anesthesia. Diagnosis requires careful radiographic technique or advanced imaging.
## Overview Humeral fracture is a break of the upper arm bone. In adult horses it usually results from trauma or a stress fracture propagating to completion (especially in racehorses). Signs are acut
## Overview Radial nerve paralysis results from damage to the nerve that innervates the extensors of the elbow, carpus, and digit. Common causes are prolonged lateral recumbency during anesthesia or
Sudden non-weight-bearing forelimb lameness after a fall, kick, or racing accident should be treated as a potential fracture. Keep the horse quiet and call the veterinarian immediately. Do not force the horse to walk on a suspected fracture.
## Overview Humeral fracture is a break of the upper arm bone. In adult horses it usually results from trauma or a stress fracture propagating to completion (especially in racehorses). Signs are acute non-weight-bearing lameness, marked upper-arm swelling, and often a dropped elbow if the radial nerve is affected. Prognosis in adults is poor. ## Causes Trauma or fatigue fracture. ## Diagnosis Clinical signs and radiographs. The limb may appear shortened. Crepitus is often present. ## Treatment Internal fixation is rarely successful in adults because of bone size and opposite-limb complications. Most adult horses are euthanized. Foals have a better chance with surgery in selected cases. ## Recovery and Prognosis Poor in adults. Guarded in foals. ## Prevention Training management to reduce stress-fracture risk in racehorses. Signs include: acute severe forelimb lameness; marked swelling of the upper arm; non-weight-bearing; possible dropped elbow from radial nerve damage
## Overview Radial nerve paralysis results from damage to the nerve that innervates the extensors of the elbow, carpus, and digit. Common causes are prolonged lateral recumbency during anesthesia or humeral fracture. The horse has a dropped elbow, cannot extend the limb, knuckles at the fetlock, and drags the toe. ## Causes Compression during anesthesia or trauma (including humeral fracture). ## Diagnosis Characteristic posture and gait. The limb can bear weight if the elbow and carpus are splinted in pure nerve paralysis. ## Treatment Supportive care, splinting, anti-inflammatories, and time for compressive injuries. Humeral fracture cases have a poor outlook. ## Recovery and Prognosis Good for many post-anesthetic compressive injuries if the limb is protected. Poor if associated with fracture. ## Prevention Proper padding and positioning during anesthesia. Signs include: dropped elbow; inability to extend the elbow and carpus; knuckling at the fetlock; dragging the toe
Adult humeral fractures carry a poor prognosis. Foals have a better chance of successful repair. Radial-nerve paralysis can accompany the fracture or occur independently from trauma or prolonged lateral recumbency under anesthesia. Diagnosis requires careful radiographic technique or advanced imaging.
Sudden non-weight-bearing forelimb lameness after a fall, kick, or racing accident should be treated as a potential fracture. Keep the horse quiet and call the veterinarian immediately. Do not force the horse to walk on a suspected fracture.
See the Humerus on our interactive 3D horse model. Open 3D Model