Basic Principles of Distal Humerus Fractures

Definition

Epidemiology

• Approximately 7% of all adult fractures involve the elbow; of these, roughly one-third involve the distal humerus - making distal humerus fractures about 2% of all fractures
• Bimodal age distribution:
  • Peak 1: Ages 12-19, predominantly males, from high-energy mechanisms
  • Peak 2: Age 80+, predominantly females, from low-energy falls
• Overall incidence ~5.7 cases/100,000/year with a nearly equal male-to-female ratio
• The incidence is increasing, paralleling the trends seen in hip, proximal humerus, and wrist fractures
• The most common mechanism overall is a simple fall from standing height (>60% in the elderly)
• High-energy mechanisms (MVCs, sports, falls from height, industrial accidents) predominate in younger adults and are associated with open fractures and polytrauma
• Open fractures occur in approximately 7% of cases overall (up to 40% with falls from height)

Anatomy - The Column Concept

• Lateral column: terminates in the capitellum, which articulates with the radial head
• Medial column: terminates in the trochlea, which articulates with the olecranon
• The olecranon fossa (posteriorly) and coronoid fossa (anteriorly) are separated by only a thin septum of bone
• The anterior angulation of the articular surface (~40° anterior to the humeral shaft axis) and the anterior bow of the distal humerus are critical to restore during fixation
• The carrying angle (physiologic valgus ~10-15° in women, 5-10° in men) must also be preserved
• Key neurovascular structures at risk: the ulnar nerve (in the cubital tunnel, medial epicondyle) and the brachial artery (anterior compartment)

Classification - AO/OTA System

Type A - Extra-Articular

Type B - Partial Articular

Type C - Complete Articular (Bicolumn)

Clinical Assessment

History

• Mechanism (high vs. low energy), time of injury, handedness, pre-injury functional status
• In elderly: evaluate precipitants of the fall (cardiac arrhythmia, cerebrovascular disease, polypharmacy)
• Comorbidities, mental status, ability to cooperate with rehabilitation

Physical Examination

• Circumferential inspection: abrasions, bruising, swelling, fracture blisters, skin tenting, open wounds
• Neurologic exam (mandatory, document pre- and post-op): ~26% of patients have an associated incomplete ulnar neuropathy at presentation
• Vascular exam: brachial artery injury is rare but must be ruled out
• Assess for compartment syndrome signs in high-energy injuries

Imaging

• AP and lateral radiographs of the elbow (minimum)
• CT scan (with 3D reconstruction where available) is strongly recommended for complex intra-articular fractures (especially AO type C) to characterize fragment size, comminution, and plan fixation
• Fat pad signs on lateral X-ray ("sail sign" - anterior; "posterior fat pad" sign) indicate hemarthrosis and suggest occult fracture

Treatment Principles

Historical Perspective

• "Bag of bones" technique (Evans, 1953) - conservative management with early active motion, advocated for elderly
• AO group principles (modern era) - ORIF with anatomic reduction and rigid fixation to allow early range of motion is now the standard for most fractures

General Goals

Nonoperative Treatment

• Reserved for: truly nondisplaced fractures, patients with minimal functional demands, or patients unfit for surgery
• Involves splinting followed by early active motion
• "Bag of bones" technique remains an option in very elderly low-demand patients with severely comminuted fractures

Operative Treatment - ORIF (Standard)

• Indication: virtually all displaced distal humerus fractures in active patients
• Dual-plate fixation (orthogonal 90°/90° or parallel plating) is the gold standard for bicolumn (AO type C) fractures
• Parallel plate configuration (medial and lateral plates on their respective columns) shows biomechanical equivalence or superiority to orthogonal plating in some studies
• Key principles:
  1. Restore articular congruity (anatomic reduction of the joint surface)
  2. Fix the articular block to the metaphysis
  3. Fix the metaphyseal block to the diaphysis
  4. Rigid fixation sufficient to allow early ROM

Surgical Approaches

• Posterior approach is most common - provides wide exposure of the entire distal humerus
• Olecranon osteotomy (chevron or transverse) gives the best articular visualization for complex intra-articular fractures (type C)
• Triceps-reflecting approaches (Bryan-Morrey) or triceps-splitting approaches avoid olecranon osteotomy complications
• Extensile posterior approach with triceps split is used for extra-articular and less complex fractures

Total Elbow Arthroplasty (TEA) - Elderly Patients

• Viable primary treatment for elderly patients (typically >65-70 years) with:
  • Severely comminuted articular surfaces
  • Osteopenia precluding stable ORIF
  • Pre-existing elbow arthritis
• Avoids the prolonged rehabilitation, stiffness risk, and high reoperation rate of ORIF in this population
• Linked semi-constrained designs are most commonly used

Distal Humerus Hemiarthroplasty

• A renewed interest exists as an alternative to TEA, particularly for fractures of the capitellum and trochlea
• Preserves the native ulnohumeral articulation

Complications

Key Surgical Principle Summary

"Starting with a highly traumatized distal humerus and finishing with a stable, mobile, and pain-free joint requires a systematic approach - determining operative indications, managing the soft tissues, selecting a surgical approach, obtaining an anatomic articular reduction, and creating a fixation construct that is rigid enough to tolerate early range of motion."

• Rockwood and Green's Fractures in Adults, 10th ed., p. 1567