Humeral shaft fractures are common diaphyseal injuries of the humerus and may be associated with radial nerve injury. Diagnosis is typically established with orthogonal (AP and lateral) radiographs of the humerus. Treatment may be nonoperative or operative, depending on fracture location, fracture pattern, stability, and associated ipsilateral injuries.
EPIDEMIOLOGY
Incidence / Burden
Approximately 3–5% of all fractures.
Reported annual incidence is roughly 7 to 11.3 per 100,000 population (rates vary by population and study). (Your provided figure; consistent with the epidemiology framework in the curriculum/derivations.)
Demographics
Age
~60% of cases occur in patients >50 years (your note).
Bimodal age distribution:
Younger patients: high-energy trauma; peak in the third decade of life.
Older patients: low-energy falls; often osteopenic/osteoporotic.
Sex
Your distribution statement:
<50 years: predominantly male
>50 years: predominantly female
(General concept aligns with bimodal epidemiology described in the OTA curriculum.)
Location
Proximal third: ~30% (your note)
Middle third: ~60% (most common)
Distal third: ~10% (your note)
Risk factors
Prior fracture history
Smoking (particularly in men)
Advanced age
Osteoporosis (conceptually consistent with low-energy fall cohort).
ETIOLOGY AND PATHOPHYSIOLOGY
Mechanism of injury
Ground-level fall (~60%): most common mechanism (especially older patients).
Motor vehicle collision (~30%): second most common mechanism (especially younger patients).
Pathologic fractures (~4.3%) (your note).
Open fractures (~3%) (your note).
Pattern–mechanism associations (practical correlations)
Proximal-third shaft fractures: common in older individuals; often after a fall onto the outstretched hand with impaction near the surgical neck (your note).
Middle-third shaft fractures:
Transverse: often due to a direct blow
Spiral: often due to torsional forces or FOOSH
Distal-third shaft fractures: may follow a fall onto a flexed elbow (your note).
Associated conditions
Floating elbow: humeral shaft fracture with associated proximal-to-middle radius/ulna fractures; typically high-energy; more common in pediatrics than adults.
Ipsilateral shoulder dislocation: uncommon; when present may be more often posterior than anterior (your note).
ANATOMY
The humeral shaft extends from the surgical neck to the supracondylar ridge and is generally cylindrical; distally it becomes more triangular with medial and lateral supracondylar ridges.
The intramedullary canal terminates 2–3 cm proximal to the olecranon fossa (your note; consistent with core anatomy concepts).
The radial groove (posterolateral) is traversed by the radial nerve and profunda brachii artery.
Muscles (deforming forces)
Fracture alignment depends on relation to muscle attachments (e.g., pectoralis major and deltoid).
Nerves (key surgical anatomy)
Radial nerve: travels medial-to-lateral; lies directly posterior at mid-diaphysis and is tethered to the lateral shaft distally—critical for mid/distal fractures and surgical approaches.
OTA curriculum provides commonly used operative distance estimates (e.g., radial nerve approximately 16–20 cm proximal to the medial epicondyle and 10–14 cm proximal to the lateral epicondyle).
Ulnar nerve: enters posterior compartment near the arcade of Struthers and courses toward the cubital tunnel (your note).
Axillary nerve: typically 3–7 cm distal to the acromion (OTA anatomy reference).
CLASSIFICATION
Descriptive: location (proximal/middle/distal third) + morphology (spiral, transverse, comminuted).
AO/OTA: diaphyseal humerus = bone 1, segment 2, pattern A/B/C.
Holstein–Lewis fracture: distal-third spiral fracture classically associated with radial nerve neuropraxia; incidence reported in the literature within broad ranges (your note; related risk concept addressed in OTA overview).
PRESENTATION
Symptoms
Pain
Weakness
Physical examination
Swelling, localized tenderness, possible skin tenting
Deformity assessment (often shortening and varus)
Pre-reduction and post-reduction neurovascular exam is critical, specifically documenting radial nerve motor/sensory status (wrist/thumb extension; dorsal hand sensation).
IMAGING
Radiographs: AP and lateral; include joints above and below (shoulder and elbow).
Transthoracic lateral may help define sagittal deformity (your note).
Traction views: may help in significant shortening or suspected extension; not routine (your note).
CT: if intra-articular extension suspected.
CT angiography: if vascular injury suspected.
EMG/NCS: helpful for monitoring recovery in nerve palsy; generally not indicated acutely solely to determine fracture treatment (consistent with standard practice concepts; OTA provides radial palsy framework).
TREATMENT
Nonoperative
Immobilization strategy
Coaptation splint or hanging arm cast for 7–10 days, followed by a functional brace.
Acceptable alignment
<20° anterior angulation
<30° varus/valgus angulation
<3 cm shortening (classic functional bracing thresholds).
Outcomes
OTA curriculum summarizes that many uncomplicated fractures do well in a functional brace; however, more recent studies report nonunion rates ~10–25%, higher than early Sarmiento-era results.
Operative
External fixation (ExFix)
Indications (typical)
High-energy comminuted/complex fractures
Open fractures
Significant soft-tissue injury or bone loss
Floating elbow
Hemodynamically unstable polytrauma
Associated vascular injury
Often used as temporary stabilization until definitive fixation, but may be definitive when necessary (your note; consistent with damage-control principles).
ORIF (plate fixation)
Absolute indications
Open fracture
Vascular injury requiring repair
Brachial plexus injury
Ipsilateral forearm fracture (floating elbow)
Compartment syndrome
Periprosthetic shaft fractures at stem tip
Failure to maintain acceptable reduction
Progressive nerve deficit after closed manipulation
Techniques
Conventional ORIF or MIPO, depending on fracture morphology and soft-tissue status.
After stable plate fixation, weight bearing as tolerated is considered safe.
Comparative outcomes
RCT data (FISH) show improved early function with surgery, with no significant DASH difference at 12 months.
Intramedullary nailing (IMN)
Relative indications
Pathologic fractures
Segmental fractures
Severe osteoporotic bone
Compromised soft tissue limiting open approach
Polytrauma
Key points
Plates and nails generally show similar union outcomes, but antegrade IMN has higher shoulder morbidity(often cited ~15–30% shoulder symptoms).
Total elbow arthroplasty
Considered in elderly low-demand patients with comminuted distal patterns and poor bone quality (your note).
TECHNIQUES (selected essentials)
Functional bracing
Weekly radiographs for the first 3 weeks to ensure maintained reduction; then every 3–4 weeks (your note; aligns with standard follow-up logic).
ORIF approaches (high-yield points)
Anterolateral approach is typical for proximal/middle third.
Posterior approach for distal third fractures; Gerwin et al. exposure percentages are summarized in OTA: triceps split alone exposes ~55% posterior diaphysis, increasing to ~76% with radial nerve mobilization and ~96% with further triceps elevation.
MIPO
Emphasizes extraperiosteal tunnel and neurovascular protection; OTA lists specific pitfalls and nerve risks by approach.
COMPLICATIONS
Nonunion
Fracture-site mobility at ~6 weeks predicts nonunion in nonoperative care (high specificity).
RUSHU (Radiographic Union Score for Humeral fractures) at 6 weeks: lower scores are associated with higher nonunion risk.
Radial nerve palsy
Systematic review data summarized in OTA: incidence ~11.8–12% with ~70–77% spontaneous recovery, and ~88% overall recovery.
Observation is appropriate for most closed-fracture palsies; exploration is recommended for open fractures and selected non-recovering cases (timing remains debated).