FCPS IMM Master Series

Humeral Shaft Nonunion

Orthobullets High-Yield Revision

1. Epidemiology & Pathophysiology

Definition: Arrest of the fracture repair process of a humeral shaft fracture, often occurring after operative treatment with compression plating (with or without bone grafting).

Incidence of Primary Nonunion

• 2% to 33% with nonoperative management (functional bracing).
• 5% to 10% with surgical management.

High-Risk Location

Proximal third humeral shaft fractures have the highest rates of nonunion.

Risk Factors

Biologic Factors Metabolic/endocrine abnormalities (Vitamin D deficiency is most common), infection, smoking, obesity, malnutrition, noncompliance, open fracture.

Mechanical Factors Unstable fracture patterns with inadequate stability; shoulder or elbow stiffness (which directs force/motion directly to the fracture site).

Pathophysiology summary: Inadequate stability at the fracture site (mechanical) OR inadequate biology resulting from metabolic issues, infection, or smaller bone surface area for healing.

2. Core Anatomy & Biomechanics

Blood Supply

The nutrient vessel of the humerus courses along the medial aspect of the mid to distal third of the diaphysis. It is at significant risk during surgical exposure.

Deforming Forces

In proximal diaphyseal fractures, Pectoralis major and Deltoid create strong deforming forces, pulling fragments apart.

Interposition Factor

Biceps tendon interposition in proximal diaphyseal fractures blocks direct fracture apposition and directly leads to mechanical nonunion.

3. Clinical Presentation & Diagnostic Workup

Physical Examination

• Inspect fit of functional brace; check skin condition.
• Assess atrophy, angulation, and gross motion.
• Neurovascular: Must rigorously assess radial nerve function.

Radiographic Imaging

• Standard: AP & Lateral of humerus, shoulder, and elbow.
• Key Findings: Lack of fracture consolidation, pseudarthrosis.
• CT Scan: Evaluates bridging callus and aids pre-op planning.

Crucial Preoperative Serum Labs

Rule out infection: CRP, ESR, CBC.

Metabolic Workup: Total protein, Serum albumin, Vitamin D, TSH, PTH.

4 & 5. Management Algorithms & Surgical Techniques

Non-Operative Management

Indications: Rarely indicated. Low-demand patients who are high-risk surgical candidates with asymptomatic nonunion.

Modalities: Brace + bone stimulators (indicated if nonunion >9 months or no progress at 3 months).

Absolute Contraindications: Pseudarthrosis, fracture gap > 5 mm, or poor blood supply.

Operative Management (Gold Standard)

Compression Plating with Bone Grafting: Superior to IM nailing for nonunion treatment.

• Instrumentation: 4.5 mm compression plate (anterior, lateral, or posterior).
• Autologous Bone Graft: ICBG gold standard for atrophic nonunions.

Specialized Operative Indications

Dual Plating

Indicated for very proximal/distal nonunion, poor metaphyseal bone, or micromotion. (92-100% union at 16 wks).

Cortical Strut Allograft

Indicated for severe osteopenia, severe bone loss, or recalcitrant nonunions. (95-100% union).

BMPs

Limited role; no clinical studies show superior outcomes over standard grafting.

Surgical Approaches

Anterior / Anterolateral: Standard approach.

Posterior Approach: Specifically used for radial nerve exploration, neurolysis, or release of nerve entrapment in spiral groove.

Complications

Radial Nerve: Neuropraxia or operative traction injury.

ICBG Donor Site Morbidity: High rate of up to 44% (pain, sensory changes).

6. Complications, Salvage & Prognosis

Nerve Complications

Radial nerve is the most common nerve injured.

Ultimate Salvage

For recalcitrant atrophic nonunions despite plating, free fibular grafting is the ultimate salvage procedure.

Overall Prognosis

With adequate operative treatment of nonunion, 83% to 100% of patients go on to complete union.

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Ultimate Numeric & High-Yield Data Cheat Sheet

High-Yield memory triggers for last-minute exam revision

Parameter / Scenario	Key High-Yield Value / Threshold
Non-op Primary Nonunion Rate (Functional Bracing)	2% to 33%
Surgical Primary Nonunion Rate	5% to 10%
Absolute Non-op Contraindication (Fracture Gap)	> 5 mm (or pseudarthrosis)
Standard Compression Plate Size	4.5 mm
ICBG Donor Site Morbidity Rate	Up to 44%
Dual Plating Union Rate	92% - 100% (at 16 weeks)
Cortical Strut Graft Union Rate	95% - 100%
Overall Operative Nonunion Union Rate	83% - 100%
Bone Stimulator Indication Criteria	Nonunion > 9 months OR no progress at 3 months
Most Common Nerve Injury	Radial Nerve
Most Common Metabolic Abnormality	Vitamin D Deficiency
Ultimate Salvage for Recalcitrant Nonunion	Free Fibular Grafting

FCPS IMM Master Revision Bank • Humeral Shaft Nonunion • Orthobullets Derived