Humeral Shaft Fractures

Humeral shaft fractures are unusual among long-bone fractures in that non-operative management achieves excellent outcomes in the majority of cases. The shoulder and elbow compensate well for residual angulation and shortening, which is why functional bracing is the gold standard.

Who. The distribution is bimodal: young men from high-energy injuries (sport, motor vehicle accidents) and older women from low-energy osteoporotic falls. The mean age is 45-55 years; the Swedish Fracture Register population is older, with a mean of 66.8 years and most fractures from low-energy falls in patients over 50, so contemporary population data show a predominantly low-energy injury in older adults.

Mechanism. Falls are the most common mechanism overall, with motor vehicle accidents and sport (throwing, arm wrestling) making up the rest of the list. A direct blow produces a transverse fracture (50%); an indirect torsional load produces a spiral or oblique fracture (50%).

Where. The middle third takes most of the fractures and the distal third carries the highest nerve risk:

• Proximal third - 30%. Spiral or oblique; the axillary nerve is at risk, rarely
• Middle third - 60%. Transverse or spiral; the radial nerve is at risk in the spiral groove
• Distal third - 10%. Spiral (Holstein-Lewis); the highest radial nerve risk

The radial nerve. It is the nerve most commonly injured in humeral shaft fractures. It enters the arm in the axilla from the posterior cord and supplies triceps proximally, then enters the posterior compartment from medial to lateral and wraps around the posterior humerus in the spiral groove, 14-20cm from the lateral epicondyle, at the junction of the middle and distal thirds. Here it is tethered by the lateral intermuscular septum, which it pierces in the distal third, before dividing into the posterior interosseous and superficial radial nerves at the elbow.

Why triceps is spared. The branches to triceps leave before the spiral groove, so a nerve injured at the groove may still extend the elbow. Wrist and finger extension are the findings that reveal the palsy, and they are what must always be tested.

Landmarks. The levels that organise the shaft:

• Surgical neck - the transition to the shaft (axillary nerve)
• Deltoid insertion - V-shaped, on the lateral mid-shaft
• Spiral groove - posterior, at the middle-distal junction
• Supracondylar ridge - the transition to the distal humerus

Deforming forces. The muscles inserting above and below the fracture pull the fragments in predictable directions, so the level of the fracture predicts the deformity:

View larger

View larger

View larger

The AO/OTA system grades complexity and comminution, which is what sets the treatment tendency: simple (A) fractures have excellent outcomes with functional bracing, and complex (C) fractures often require surgical stabilisation. The descriptive and location-based classifications add the pattern and the level, which between them predict stability in a brace and the nerve at risk.

AO/OTA ClassificationDescriptive ClassificationLocation-Based

12-A (Simple)

Description

Two fragments, over 90% cortical contact

Subgroups

A1: Spiral, A2: Oblique (over 30°), A3: Transverse (under 30°)

Treatment Tendency

Functional bracing

12-B (Wedge)

Description

Three fragments, contact between main fragments possible

Subgroups

B1: Spiral wedge, B2: Bending wedge, B3: Fragmentary wedge

Treatment Tendency

Bracing or surgery

12-C (Complex)

Description

Multiple fragments, no contact between main fragments

Subgroups

C1: Spiral, C2: Segmental, C3: Irregular comminuted

Treatment Tendency

Usually surgical

Type	Description	Subgroups	Treatment Tendency
12-A (Simple)	Two fragments, over 90% cortical contact	A1: Spiral, A2: Oblique (over 30°), A3: Transverse (under 30°)	Functional bracing
12-B (Wedge)	Three fragments, contact between main fragments possible	B1: Spiral wedge, B2: Bending wedge, B3: Fragmentary wedge	Bracing or surgery
12-C (Complex)	Multiple fragments, no contact between main fragments	C1: Spiral, C2: Segmental, C3: Irregular comminuted	Usually surgical

View larger

Transverse

Mechanism

Direct blow

Stability

Unstable in brace

Nerve Risk

Moderate

Oblique

Mechanism

Bending/torsion

Stability

Variable

Nerve Risk

Moderate

Spiral

Mechanism

Torsion

Stability

More stable

Nerve Risk

Higher (distal)

Comminuted

Mechanism

High energy

Stability

Unstable

Nerve Risk

Variable

Segmental

Mechanism

High energy

Stability

Very unstable

Nerve Risk

High

Pattern	Mechanism	Stability	Nerve Risk
Transverse	Direct blow	Unstable in brace	Moderate
Oblique	Bending/torsion	Variable	Moderate
Spiral	Torsion	More stable	Higher (distal)
Comminuted	High energy	Unstable	Variable
Segmental	High energy	Very unstable	High

Holstein-Lewis. A distal third spiral oblique fracture, named as a pattern because of its radial nerve palsy rate of 22-32%: the sharp proximal spike can lacerate or entrap the nerve as it passes through the lateral intermuscular septum. With or without a palsy it warrants strong consideration for ORIF, since fixation allows direct visualisation and protection of the nerve.

What the eponym does not do. It does not lower the threshold for exploring a primary palsy in a closed fracture, which is observed exactly as in any other pattern. Shao's review found transverse fractures as strongly associated with palsy as spiral ones, with the association strongest in the middle and middle-distal shaft rather than the distal third alone, and several later series have failed to show that this pattern carries a higher palsy rate than other distal-third fractures. Use it as a named pattern that should raise suspicion and prompt a careful, documented nerve examination.

Proximal third

Boundaries

Surgical neck to deltoid insertion

Clinical Relevance

Muscular forces cause abduction/ER of proximal fragment

Middle third

Boundaries

Deltoid insertion to supracondylar region

Clinical Relevance

Most common site, radial nerve at risk posteriorly

Distal third

Boundaries

Supracondylar region

Clinical Relevance

Holstein-Lewis pattern, highest nerve risk, consider ORIF

Location	Boundaries	Clinical Relevance
Proximal third	Surgical neck to deltoid insertion	Muscular forces cause abduction/ER of proximal fragment
Middle third	Deltoid insertion to supracondylar region	Most common site, radial nerve at risk posteriorly
Distal third	Supracondylar region	Holstein-Lewis pattern, highest nerve risk, consider ORIF

History. The mechanism (direct blow, torsion or fall) predicts the pattern. The other answers that change management:

• Hand dominance and occupation - manual or sedentary work
• Comorbidities - diabetes, smoking, osteoporosis
• Previous injury - the pathological fracture concern

Examination. Look for deformity, swelling, bruising and the condition of the skin; feel for point tenderness and crepitus; movement is limited by pain, but the shoulder and elbow are still tested. The neurovascular examination is the part that matters, and the two structures in question are the radial nerve and the brachial artery.

Reading the examination. Wrist drop is the classic finding. Wrist extension (ECRL, ECRB) is carried by the radial nerve proper, while thumb and finger extension (EPL, EDC) and supination (supinator) are posterior interosseous nerve functions. A palsy found at this first examination is a primary palsy; one that appears after a manipulation is secondary, and the two are managed differently (see Radial Nerve Palsy Management).

Radiographs. AP and lateral views of the entire humerus, which must include the shoulder and elbow joints; if either joint is not fully visualised, add separate views of it. The films are read for fracture pattern, displacement, angulation and any articular involvement, and for the associated injuries that change the plan, a floating elbow or a shoulder dislocation.

What to measure. The pattern first, simple or comminuted, because simple fractures brace well and comminuted fractures may need surgery. Then coronal (varus/valgus) angulation on the AP view, sagittal (anterior/posterior) angulation on the lateral, shortening against the normal side, and joint involvement, which prompts a CT if suspected. The thresholds that make alignment acceptable, and the reduction that follows if they are exceeded, are given under Management.

Further imaging. CT is indicated for articular extension, for preoperative planning of comminuted fractures and for the pathological fracture work-up. MRI evaluates a suspected pathological fracture and soft-tissue injury. Angiography is for suspected vascular injury, which is rare.

Algorithm

View larger

The decision. Radial nerve function is documented before anything else happens. An open fracture or a vascular injury goes to emergency surgery; a secondary palsy after manipulation, or a progressive deficit, is explored; a floating elbow, polytrauma, a bilateral or pathological fracture, or unacceptable alignment is fixed. Everyone else is a candidate for a brace, provided they are compliant, their skin and body habitus suit it, and the pattern is simple and stable.

Primary palsy is present at the time of injury and is usually a neurapraxia from stretch or contusion. About 70% recover spontaneously within 3-4 months (in Shao's pooled data, 70.7% spontaneous recovery among conservatively managed patients and 88.1% overall recovery including those explored), and early exploration confers no benefit, so the palsy is observed with a wrist splint and clinical and EMG monitoring. If there is no recovery by 4 months, explore.

Secondary palsy develops after manipulation or surgery and suggests the nerve is entrapped in the fracture site. Spontaneous recovery is unlikely without exploration, so it is explored urgently.

Choosing the implant. Plating is preferred for distal-third and Holstein-Lewis patterns, simple fractures and nonunions, because it allows the radial nerve to be seen and protected. A nail suits proximal and mid-shaft, segmental, comminuted or pathological fractures and cases with soft-tissue concerns; the antegrade nail avoids the radial nerve but risks the rotator cuff at its entry point.

ORIF PlatingIMN TechniqueCritical Pitfalls

Positioning. Supine with the arm on an arm board for the anterolateral approach; lateral decubitus or prone for the posterior approach; beach chair for proximal fractures.

Anterolateral approach. The incision follows the lateral border of biceps and the interval is developed between brachialis (musculocutaneous nerve) and brachioradialis (radial nerve). The radial nerve runs between these two muscles: identify it and protect it. The plate is applied to the flat anterolateral surface of the humerus.

Posterior approach. A midline posterior incision, with triceps split in the midline or its medial and lateral heads elevated. The radial nerve is identified in the spiral groove and protected, and the plate goes on the flat posterior surface.

The plate. A 4.5mm narrow or broad LCP, with a minimum of 3-4 screws (6-8 cortices) on each side of the fracture. Simple patterns are compressed; comminution is bridged.

MIPO. Minimally invasive plate osteosynthesis passes the plate submuscularly through small proximal and distal incisions, which reduces soft-tissue stripping and the theoretical risk of nerve injury. It requires fluoroscopy.

View larger

View larger

View larger

View larger

Entry. Antegrade entry is through the lateral greater tuberosity; retrograde entry through the olecranon fossa is rare.

Antegrade technique. In the beach chair or lateral position:

1. Entry at the greater tuberosity, slightly lateral to the articular surface
2. Guide wire across the fracture
3. Ream to the appropriate size
4. Insert the nail with rotational alignment maintained
5. Proximal and distal interlocking

Reduction. The fracture may need open reduction, with a mini-open approach to pass the guide wire; blocking screws correct angulation.

Protecting the cuff. Enter lateral to the articular margin, bury the nail below the bone surface, and, as some surgeons do, repair the cuff over the entry point.

Antegrade Entry Point

The entry point is critical. Too medial damages supraspinatus and cuff. Use lateral greater tuberosity entry or a medial entry (through tendon with repair). Shoulder pain remains problematic.

View larger

The radial nerve. Identify it before plating any mid-shaft fracture: it crosses from posterior to anterior at the junction of the middle and distal thirds. Mark its position and protect it throughout, and consider a preoperative EMG if there is a neurological deficit.

Malreduction. Verify rotation clinically against the other side and check alignment on fluoroscopy in two planes. Varus malreduction is common, from a plate applied too anteriorly.

Hardware failure. Adequate plate length (a minimum of 6 cortices on each side), locking screws in osteoporotic bone, and bridging rather than compressing comminuted segments.

Infection. Perioperative antibiotics, minimal soft-tissue stripping and careful haemostasis.

Nail entry. Too medial an entry damages the cuff; bury the nail to reduce impingement, and consider plating if the nail trajectory is poor.

The palsy figure. The table's 12-18% is the incidence of primary palsy; Shao's pooled prevalence across 4,517 fractures was 11.8%. Say which figure you are quoting.

Nonunion. Transverse fractures fail to unite in a brace more often (2-10%, against 5% or less for oblique and spiral patterns): the narrow isthmus and the transverse orientation provide poor cortical contact. Consider primary ORIF for a transverse fracture at the narrow diaphyseal portion.

Shoulder stiffness. Common at first and preventable. The key to successful functional bracing is early motion, so pendulum exercises begin on day one, and the stiff shoulder is treated with physiotherapy.

What decides the result. The prognostic factors are the ones already met. Fracture pattern is significant: simple patterns do well with bracing and transverse fractures are at risk. Patient compliance is critical for bracing, since non-compliance leads to malunion or nonunion. Radial nerve status matters, a primary palsy usually recovering and a secondary one needing surgery; associated injuries have a variable effect, with polytrauma patients possibly needing fixation; and smoking and diabetes are both negative, the first through higher nonunion rates and the second through delayed healing and more complications.

Plate or nail. Meta-analyses show similar union rates, both over 95%. Bhandari's pooling of three trials found plating reduced reoperation and shoulder problems; Heineman's later and larger pooling of four trials found no significant difference in complications, nonunion, infection, nerve palsy or reoperation, and neither was powered to settle the question. Nailing is faster but is associated with more shoulder pain (antegrade) or elbow issues (retrograde), so the implant is chosen on fracture pattern, bone quality and surgeon familiarity rather than a proven superiority.

Global Epidemiology

Guideline & Registry Landscape