Mechanism of injury and diagnosis
Shaft injuries occur through two main mechanisms: direct (a direct heavy blow to the arm) or indirect (a fall on the hand or elbow joint).
Diagnosis is usually straightforward, as examination reveals absolute signs of a fracture:
- Visible deformity of the limb axis.
- Pathological mobility in the shaft zone.
- Crepitus (grinding) of bone fragments upon palpation.
- Severe impairment of upper limb function.
To confirm the diagnosis, radiography is performed in two standard projections. Important rule: the X-ray must capture the entire humerus as well as both adjacent joints (shoulder and elbow).
Biomechanics of fragment displacement
Numerous muscles attach to the humerus (deltoid, biceps, triceps, pectoralis major, supraspinatus). In a fracture, their pull leads to significant displacement of the fragments. The direction of displacement strictly depends on the level at which the fracture line occurred.
- Supra-deltoid fracture (fracture line above the attachment of the deltoid muscle):
- Central (upper) fragment is displaced medially and posteriorly under the action of the latissimus dorsi and pectoralis major muscles. It also rotates and moves upward.
- Distal (lower) fragment is pulled upward, laterally, and forward by the pull of the deltoid, coracobrachialis, and triceps muscles. In this case, the sharp ends of the bone can damage the neurovascular bundle.
- Sub-deltoid fracture (fracture line below the attachment of the deltoid muscle):
- Central fragment is sharply abducted and displaced laterally (due to the action of the deltoid muscle).
- Distal fragment is displaced upward and slightly posteriorly by the action of the biceps, triceps, and coracobrachialis muscles.
Clinically important anatomy: At the transition from the middle third of the shaft to the lower third, the radial nerve (n. radialis) wraps around the bone and lies in close proximity to it. In fractures at this level, it is extremely vulnerable to compression or rupture.
Pre-hospital stage and first aid
At the first aid stage, the patient must be administered general analgesics and provided with strict transport immobilization.
- Drug of choice: contoured ladder splints applied from the fingertips of the injured arm to the healthy shoulder joint on the opposite side.
- Alternative: if splints are unavailable, the arm is securely fixed to the torso using a Desault-type bandage.
- Strictly contraindicated: suspending the arm in a standard sling without additional fixation, as this may worsen the deformity and provoke secondary nerve and vascular injuries.
Conservative treatment
The main challenge in shaft fractures is not reducing the bone, but holding the fragments in the correct position. If conservative tactics are chosen, reduction of the upper half of the humerus is performed via axial traction, abduction, and moving the lower fragment anteriorly.
For fixation, a thoracobrachial plaster cast or abduction splint is used. The shoulder is fixed in 90° abduction and positioned 30–40° anterior to the frontal plane.
Skeletal traction: Performed via the olecranon with a 4–5 kg weight. Traction can be horizontal (on a TsITO abduction splint) or vertical (on a Balkan frame).
Combined techniques: Used in elderly individuals or patients with severe chest trauma (when a bulky cast hinders breathing). The essence of the method: the weight of the limb itself eliminates length displacement, while a bandage eliminates width displacement.
- Caldwell hanging cast: applied from the hand to the upper third of the arm, leaving the shoulder joint free.
- Shortened "sleeve": a circular cast from the elbow to the shoulder joint (preserving motion in all joints).
Surgical treatment
Today, surgical intervention is recognized as the leading method in the treatment of humeral shaft fractures.
Indications for surgery:
- Inability to achieve closed reduction of fragments.
- Need to shorten immobilization time.
- Prevention of functional limitations of the limb.
In addition to traditional plates, screws, and external fixation devices, the most modern and effective method is intramedullary osteosynthesis with an upper- and lower-locked nail. The surgery is most often performed closed (without an incision at the fracture site), and its main advantage is the ability to completely discontinue cast wear within just 4–5 days.
Briefly: answers to topical questions
What are the absolute and relative indications for surgical treatment of humeral shaft fractures?
Surgical treatment of humeral shaft fractures is indicated when closed reduction attempts fail. An urgent indication for surgical intervention is a fracture combined with radial nerve palsy. Additional goals of surgery include reducing the duration of external immobilization and minimizing functional limitation of the injured limb.
Into which morphological subgroups are types A, B, and C of humeral shaft fractures divided according to the AO/ASIF classification?
According to the AO/ASIF classification, humeral shaft fractures are divided into the following morphological subgroups:
- Type A (simple fracture) — spiral (A1), oblique $\ge$ 30° (A2), and transverse < 30° (A3).
- Type B (wedge fracture) — intact bending wedge (B2) and fragmented wedge (B3).
- Type C (complex comminuted fracture) — with an intact segmental fragment (C2) and irregular (C3).
What clinical symptoms of motor and sensory deficit occur when the radial nerve is injured at the level of the middle third of the arm?
When the radial nerve (n. radialis) is injured, a characteristic pattern of motor and sensory function loss develops.
- Motor impairments — paralysis of the wrist and finger extensors, inability to extend at the elbow and wrist joints, loss of the triceps brachii reflex. A "drop hand" sign is formed.
- Sensory impairments — anesthesia of the posterior surface of the arm, forearm, radial half of the dorsal hand, dorsal surface of the thumb, and proximal phalanges of the index and partially middle fingers.
What late complications associated with impaired bone healing processes are typical for humeral shaft fractures?
Typical late complications of humeral shaft fractures directly associated with impaired normal bone healing processes include nonunions (pseudarthroses). Additionally, in the late period, paresis may develop due to compression of the radial nerve by the forming callus or scar tissues.
To easily recall the displacement in a sub-deltoid fracture, imagine a scale: the deltoid muscle pulls the upper fragment "outward and upward," while the powerful forearm flexors and extensors (biceps and triceps) pull the lower fragment "toward themselves" (upward and posteriorly).
Class and exam questions
Why is it forbidden to use only a sling for humeral shaft fractures?
A sling does not provide rigid fixation of the joints and bone axis. Under the influence of gravity and muscle pull, the fragments can displace even further, damaging the radial nerve or blood vessels.
Which nerve is most commonly damaged in shaft fractures and why?
Radial nerve (n. radialis). At the border of the middle and lower thirds of the humerus, it spirals around the bone and lies so close to it that it is frequently compressed by the displaced bone fragments.
Why is an intramedullary nail better than a plaster cast?
The nail allows secure fixation of fragments from inside the bone without a large incision. As a result, the patient does not need to wear a heavy cast for months — external fixation is removed after just a few days, allowing rapid initiation of joint mobilization.
What else to study on this topic
- Fractures of the surgical and anatomical neck of the humerus
- Method of single-stage reduction of adduction and abduction fractures
- Prevention of post-traumatic contractures and the role of the «Reader's pouch»
- Complications of humeral fractures: avascular osteonecrosis and deforming arthrosis
- Management specifics of humeral fractures in elderly patients
Master the entire topic in the "Traumatology" course
This is a summary. The course covers everything tested in classes and exams.
- Complete guide on «Humeral shaft fractures» and 812 more pages on the subject
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 35 video lessons on the subject
Other topics in the "Specialized Adult Traumatology" section
The entire "Specialized Adult Traumatology" sectionPrepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.