The humeral shaft is defined as the region from 1 cm distal to the surgical neck of the humerus to 2 cm proximal to the humeral condyles. Humeral shaft fractures are most common in young adults, with the middle portion being the most frequently affected, followed by the lower portion, and the upper portion being the least common. Fractures in the middle and lower third are prone to radial nerve injury, while fractures in the lower third are more likely to result in nonunion. There is usually a clear history of trauma, accompanied by pain and limited mobility in the affected limb. X-rays can confirm the fracture location and the extent of displacement.

bubble_chart Etiology

Causes of Disease

(1) Direct violence: Often occurs in traffic and industrial accidents, mostly seen in the middle third, with comminuted or transverse fractures.

(2) Indirect violence: Caused by falling with the palm or elbow hitting the ground, mostly seen in the lower third, with oblique or spiral fracture lines.

(3) Rotational force: Commonly occurs during throwing training for new recruits, frequently seen in the middle to lower third, with spiral fracture lines.

Pathogenesis

The displacement of the humeral shaft fracture is not only related to the direction of the force and the weight of the limb but also directly influenced by muscle contraction. When the fracture is located in the upper part of the humeral shaft, above the insertion point of the deltoid muscle, the proximal fragment is pulled forward and inward by the pectoralis major, latissimus dorsi, and teres major muscles, while the distal fragment is pulled upward and outward by the deltoid muscle. For mid-shaft humeral fractures, when the fracture is below the insertion point of the deltoid muscle, the proximal fragment is pulled outward and forward by the contraction of the deltoid and coracobrachialis muscles, and the distal fragment is pulled upward by the contraction of the biceps and triceps muscles. For lower humeral shaft fractures, the muscle pull on both ends is roughly balanced, and the direction of displacement depends on the external force, the position of the limb, and gravity.

Fracture: Local swelling may be present, with possible shortening or angular deformity. There is severe localized tenderness, abnormal movement, and bone crepitus. Upper limb mobility is restricted. When combined with radial nerve injury, symptoms such as wrist drop may occur.

bubble_chart Treatment Measures

1. Non-displaced fracture

   includes closed transverse

2. short oblique
3. comminuted or linear non-displaced fractures without nerve injury, which do not require anesthesia. Gentle manual reduction is used to correct angular or rotational deformities. External fixation methods can be selected based on specific conditions and circumstances: a. Lightweight long-arm hanging gypsum or upper arm "U"-shaped gypsum with a triangular bandage to suspend the forearm; b. Small splintage; c. Long-arm gypsum with an abduction brace or shoulder spica gypsum fixation; d. Single-arm external fixation frame. Gypsum fixation lasts for 6 weeks, and external fixation is removed after X-rays show initial callus formation, followed by limb movement exercises. For those with external fixation frames, joint movement can be initiated early.
4. Displaced fracture

   requires manual reduction under brachial plexus or local hematoma anesthesia, followed by small splintage or external fixation frame. When conditions permit, closed reduction

5. with interlocking intramedullary nail fixation can also be performed under fluoroscopy with a TV X-ray machine.
6. Fracture combined with radial nerve injury

   If the fracture is non-displaced, the nerve is often contused. After fracture external fixation, observe for 1–3 months. If the nerve does not recover, surgical exploration is indicated. For fractures with significant displacement, the radial nerve may be trapped between the fracture ends, and manual reduction should not be attempted to avoid nerve rupture. Surgical exploration of the nerve should be performed, along with open reduction and internal fixation of the fracture.

7. Open reduction and internal fixation

   is suitable for open fractures within 8 hours

8. after injury, where thorough debridement minimizes infection risk; closed medial malleolus fractures with soft tissue interposition between fracture ends that cannot achieve functional reduction manually, or comminuted humeral fractures; multiple bone and joint injuries in the same limb; fractures combined with vascular injury or fractures with significant displacement and radial nerve injury; non-union or severe malunion fractures. For those treated with plate and screws, reliable external fixation is still required postoperatively. Compression plate
9. interlocking intramedullary nail internal fixation and external fixation frame allow early functional exercises.