Humeral Fracture

The long bones of dogs and cats closely resemble the bones found in the human arms and legs. Fractures of these bones can occur in dogs and cats for a variety of reasons, including motor vehicle accidents, altercations with other animals, and athletic or sporting injuries, among others.

Limb Anatomy

Forelimb (front limb):

• Front paws:
• Phalanges (toes; three bones per toe)
• Metacarpal bones (hand; four primary bones)
• Carpal bones (wrist)
• Forearm: radius and ulna
• Upper forelimb: humerus and scapula (shoulder blade)

Hindlimb (rear limb):

• Back paws:
• Phalanges (toes; same structure as front paws)
• Metatarsal bones (foot; four main bones)
• Tarsal bones (ankle or hock)
• Lower hindlimb: tibia (shin bone) and fibula
• Thigh: femur
• Pelvis: ilium, acetabulum (hip socket), and ischium

Joints:

• Carpus (wrist): composed of small carpal bones and the radius
• Elbow: formed by the radius, ulna, and humerus
• Shoulder: formed by the humerus and scapula
• Tarsus (ankle): composed of small tarsal bones and the tibia
• Stifle (knee): formed by the femur and tibia
• Hip: composed of the femur and pelvis (acetabulum)

Types of Fractures

Bones can break in a variety of patterns, collectively referred to as fractures. To assist with treatment planning, fractures are classified into specific categories.

• Incomplete fracture:
  The bone bends or cracks without breaking completely around its circumference. This type of fracture is most commonly seen in young animals (Figure 1).
• Complete fracture:
  The bone is broken entirely through its circumference, creating two or more separate fragments (Figure 2).

Complete fractures are further described based on fracture configuration:

• Transverse: a straight break across the bone, perpendicular to its long axis
• Oblique: a diagonal fracture producing two sharp-edged fragments
• Comminuted: the bone is shattered into three or more fragments of various shapes (Figure 3)

If a fracture is associated with an open skin wound, it is referred to as an open fracture. This can occur when bone fragments penetrate outward through the skin or when an external object enters the body and breaks the bone. Fractures without an associated skin wound are termed closed fractures. Open fractures are considered more urgent due to the increased risk of infection.

Severe lameness is typically observed, and the injured limb is usually obvious. Most pets will avoid bearing weight on the affected limb, although some may partially bear weight depending on the fracture’s location and severity. Animals involved in high-impact trauma, such as vehicular accidents or falls from height, may sustain multiple fractures and may be unable or unwilling to walk.

Additional signs include swelling, pain, and abnormal movement at the fracture site.

When fractures result from trauma, other systemic injuries may also be present. Abdominal trauma can cause internal bleeding or rupture of organs such as the urinary bladder. Thoracic trauma may result in lung contusions, bleeding around the lungs, or air leakage into the chest cavity due to lung tears. These associated injuries can be life-threatening and may delay definitive fracture treatment.

Your veterinarian will perform a thorough examination to assess for additional injuries, especially to vital organs. Radiographs (x-rays) of the affected limb are usually recommended. Pain medication or sedation may be required to safely obtain diagnostic images.

Additional diagnostic tests may include:

• Complete blood count and serum chemistry
• Chest and abdominal radiographs
• Abdominal ultrasound
• In some cases, a full-body trauma CT scan

Initial Management

The first priority following a fracture is immobilization of the bone fragments. Immobilization reduces pain and prevents further damage to surrounding muscles, nerves, and blood vessels.

Prior to veterinary evaluation, pets should be confined to a small, secure area such as a crate or box, with movement limited to essential activities only. Veterinary care should be sought immediately. No medications or treatments should be administered unless specifically directed by a veterinarian.

Closed fractures are ideally treated within 2–4 days. Open fractures require prompt wound and bone cleaning, ideally within 8 hours, with definitive repair occurring within 24–48 hours.

Temporary immobilization is often achieved using splints. Proper splinting requires immobilization of the joints above and below the fracture. Fractures below the elbow or knee are easier to splint, whereas fractures of the upper arm or thigh are more difficult due to shoulder and hip anatomy. In these cases, strict confinement is usually recommended until definitive treatment is planned.

Fracture Repair

Bones normally withstand forces such as:

• Bending
• Torsion (twisting)
• Compression (weight-bearing forces)
• Traction (muscle pull at attachment sites)

Once fractured, bones must be stabilized to resist these forces and allow healing.

Methods of stabilization include:

• External coaptation: splints or casts applied externally; effective against bending forces and moderately effective against torsion and compression.
• External fixation: surgically placed pins connected externally by rigid bars; excellent resistance to bending, compression, and torsion (Figure 4).
• Internal fixation: surgically implanted devices such as plates, screws, nails, pins, and wires placed on or within the bone (Figures 5 and 6).

Factors Influencing Fracture Healing

Treatment planning considers multiple factors related to the patient, fracture type, and environment. These factors influence healing speed and complexity.

Patient factors:

• Young, calm, healthy animals heal faster
• Older, active, ill, very small or very large animals heal more slowly

Fracture factors:

• Closed, low-impact, transverse fractures heal more easily
• Open, high-impact, comminuted fractures heal more slowly

Environmental factors:

• Close supervision and restricted activity promote healing
• Unrestricted activity increases complications

Veterinary surgeons guide owners through treatment choices based on home environment, care requirements, and financial considerations. Splints and casts are not always simpler or cheaper, as they require frequent monitoring and adjustments.

Bandage Care

Bandages and splints require careful monitoring. Owners should watch for slipping, wetness, odor, swelling of toes, or chewing damage. Any concerns should prompt immediate veterinary evaluation. Bandages must remain clean and dry, and owners should not modify them in any way.

Activity Restriction

Strict confinement is essential until healing is confirmed radiographically. Pets should not run, jump, or play. Dogs should be leash-walked briefly for elimination only. Cats are best confined to crates or small rooms without furniture.

Assistance

Pets may need help standing or walking during recovery. Commercial support slings are available and often easier to use than homemade alternatives.

Physical Therapy

Fractures cause muscle weakness, joint stiffness, and pain. Physical therapy helps maintain mobility and comfort without compromising bone healing.

Home-based therapies may include:

• Cold therapy during the first week to reduce pain and swelling
• Range-of-motion exercises to preserve joint flexibility
• Massage therapy to reduce scar tissue formation and discomfort

Healing time depends on age, tissue damage, and surgical trauma. Puppies may require as little as 4 weeks, while adult animals typically need at least 8 weeks before resuming normal activity.

Owners play a crucial role in enforcing restrictions. Although recovery can be lengthy, most fractures heal well, allowing pets to regain near-normal strength and function with appropriate care and rehabilitation.