Orthopaedic Surgery - Nonunion of Fractures

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Basics

A fracture nonunion is a failure of normal bone healing in which the fracture shows little or no further progression toward union over an appropriate period of time.

The diagnosis is based on a combination of:

Clinical symptoms

Serial radiographs

Fracture biology

Mechanical stability

There is no single time threshold that applies to every fracture because expected healing varies according to the bone, fracture location, injury severity, fixation method, and patient factors.

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Epidemiology

The likelihood of nonunion varies substantially among different bones and fracture patterns.

Historical approximate rates include:

Tibial shaft fractures: about 10%

Clavicular shaft fractures: about 5%

Femoral shaft fractures: about 1%

Metaphyseal and epiphyseal fractures generally have a strong healing potential, although they may heal in an abnormal position and result in malunion if the original displacement is not adequately corrected.

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Risk Factors

The most important modifiable risk factor is:

Tobacco smoking.

Nicotine and other tobacco-related effects impair vascularity and bone healing.

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Nutritional Factors

Poor nutritional status can interfere with fracture healing.

Potential contributors include:

Vitamin D deficiency

Protein-calorie malnutrition

Other vitamin or mineral deficiencies

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Systemic Disease

Patients with systemic illness may have impaired fracture healing.

Examples include conditions that compromise:

Metabolism

Vascular supply

Immune function

Bone quality

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Open Fractures

Severe open fractures are at particularly high risk.

This is especially true for Gustilo-Anderson Type III open fractures, which may be associated with:

Extensive soft-tissue injury

Contamination

Bone loss

Compromised blood supply

Infection

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Etiology

Nonunion usually results from one or more problems involving:

Biology

Mechanical stability

Infection

or

Bone loss.

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Open Fractures

Open fractures may impair healing because of:

Soft-tissue destruction, periosteal stripping, contamination, and vascular injury.

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Bone Loss

A fracture gap or loss of a segment of bone can prevent the fragments from making sufficient biological or mechanical contact for union.

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Osteomyelitis

Bone infection is an important cause of nonunion.

An infected nonunion must be recognized because its treatment differs fundamentally from that of an aseptic nonunion.

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Diagnosis

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Signs and Symptoms

Persistent pain is a common presentation.

Typical symptoms include:

Pain with weight bearing

Pain with limb use

Failure of symptoms to improve over time

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History

Important historical features include:

Original fracture mechanism

Whether the injury was open

Previous operations

Smoking history

Nutritional status

Systemic disease

Prolonged wound drainage after the initial operation

Persistent or recurrent wound drainage raises particular concern for infection.

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Physical Examination

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Motion at the Fracture Site

Abnormal motion at a fracture that should have healed suggests nonunion.

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Pain With Stress

Applying stress across the involved bone may reproduce pain at the fracture site.

This may indicate persistent mechanical instability.

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Wound Examination

Inspect carefully for:

Persistent drainage

Sinus formation

Soft-tissue loss

Erythema

Swelling

These findings may indicate infection or inadequate soft-tissue coverage.

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Limb Function

Assess:

Alignment

Length

Rotation

Joint motion

Muscle strength

Neurovascular status

A healed bone alone is not the only objective; the limb must also have useful function.

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Imaging

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Plain Radiographs

Serial radiographs are the first-line imaging study.

Typical findings may include:

Persistent fracture line

Failure of the proximal and distal fragments to unite

Lack of bridging callus

Broken fixation hardware

Lucency around screws

Progressive deformity

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Hardware Failure

Broken plates, screws, nails, or other implants often indicate persistent mechanical loading across a fracture that has not united.

Lucency around screws may reflect:

Loosening, infection, or both.

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CT

CT is often the most useful advanced imaging study when plain radiographs are inconclusive.

It can demonstrate:

Absence of bridging bone across the fracture

Persistent fracture gaps

Partial union

Hardware failure

Complex deformity

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Laboratory Evaluation for Infection

When infection is suspected, evaluation may include:

CBC

ESR

CRP

These tests are supportive but cannot definitively rule infection in or out.

Definitive diagnosis often requires:

Deep tissue or bone cultures obtained at surgery.

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Pathological Findings

The fracture gap is commonly filled with:

Fibrous tissue rather than bridging bone.

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Pseudoarthrosis

With longstanding instability, a false joint may develop between the bone ends.

This can form a synovial pseudoarthrosis, in which the opposing surfaces behave like an abnormal joint.

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Classification by Biology

Although not specified in the original entry, nonunion is commonly described biologically as:

Hypertrophic

Oligotrophic

Atrophic

This distinction can help guide treatment.

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Hypertrophic Nonunion

A hypertrophic nonunion demonstrates abundant callus but failure of bridging because of excessive motion.

The principal problem is usually:

Insufficient mechanical stability.

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Atrophic Nonunion

An atrophic nonunion has little callus and poor biological activity.

Contributing factors may include:

Poor vascularity

Bone loss

Soft-tissue compromise

Infection

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Differential Diagnosis

The most important distinction is between:

Septic nonunion

and

Aseptic nonunion.

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Septic Nonunion

An infected nonunion may be suggested by:

Persistent drainage

Sinus tract

Elevated inflammatory markers

Implant loosening

Previous deep infection

However, infection may occasionally be clinically subtle.

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Aseptic Nonunion

Aseptic nonunion occurs without active infection and is more commonly related to:

Mechanical instability

Poor biological environment

Bone loss

or a combination of these factors.

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Synovial Pseudoarthrosis

The presence of a mature false joint may alter surgical planning because fibrous and synovial tissue must usually be removed before definitive healing can occur.

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Treatment

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General Principles

Treatment begins by identifying why the fracture failed to unite.

Successful management requires correction of every important problem rather than simply adding more fixation.

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Smoking Cessation

All tobacco and nicotine products should be stopped.

Continued smoking substantially reduces the likelihood of successful union.

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Nutritional Optimization

Correct identifiable deficiencies, including:

Vitamin D deficiency

Poor protein intake

Other nutritional abnormalities

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Medical Optimization

Systemic conditions that impair healing should be treated or optimized whenever possible.

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Surgical Planning

Before surgery, determine:

Is the nonunion infected?

Is there adequate blood supply?

Is there significant bone loss?

Is the fixation mechanically inadequate?

Is deformity present?

Is the soft-tissue envelope adequate?

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Septic Nonunion

If infection is present, identifying the causative organism is critical.

Failure to obtain appropriate microbiologic diagnosis can lead to:

Persistent infection and repeated treatment failure.

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Microbiologic Diagnosis

Multiple deep tissue cultures are generally preferred.

Superficial swabs are less reliable.

Management may include:

Débridement

Culture-directed antibiotics

Removal or revision of infected hardware

Staged reconstruction

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Débridement

All nonviable tissue may need to be removed, including:

Necrotic bone

Fibrous tissue

Infected soft tissue

Loose implants

The goal is to leave a viable biological environment capable of healing.

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Soft-Tissue Coverage

Adequate vascularized soft-tissue coverage is essential.

If local tissue is inadequate, reconstruction may require:

Rotational muscle flap

or

Free tissue transfer.

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Mechanical Stability

When excessive movement is the primary cause, treatment must reduce motion at the fracture site.

Stable fixation may be achieved using:

Revision intramedullary nailing

Plate fixation

Compression plating

Dual plating

External fixation

depending on the bone and fracture pattern.

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Rigid Fixation

Some nonunions require very rigid stabilization, such as:

Double-plate fixation, particularly when substantial mechanical instability is present.

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Bone Grafting

When biology is insufficient, bone grafting may be used to stimulate healing.

Options may include:

Autologous cancellous bone graft

Structural graft

Vascularized bone graft

Bone graft substitutes in selected situations

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Bone Defects

Large segmental defects may require:

Bone transport

Masquelet-type induced membrane techniques

Vascularized grafting

or other reconstructive strategies.

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Follow-Up

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Prognosis

Union can be achieved in most patients when:

Infection, biology, alignment, and mechanical stability are all addressed appropriately.

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Limb Salvage

Even when union is eventually achieved, the functional result depends on:

Joint condition

Muscle function

Nerve function

Soft-tissue quality

Limb alignment

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Amputation

In rare situations, amputation may be appropriate when:

Repeated reconstruction fails

Infection cannot be controlled

The limb remains severely painful

Useful function cannot be restored

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Complications

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Infection

Infection is one of the most important complications.

The risk of infection increases with repeated operative procedures.

Historical teaching suggests that infection risk may approximately double with each additional surgery, although the actual risk varies substantially according to injury and patient factors.

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Persistent Nonunion

Despite appropriate treatment, some fractures may fail to heal again.

Persistent nonunion may require:

Repeat fixation

Further grafting

Soft-tissue reconstruction

Bone transport

or, occasionally,

Amputation.

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Other Complications

Potential complications include:

Hardware failure

Malalignment

Joint stiffness

Limb-length discrepancy

Chronic pain

Refracture

Donor-site morbidity from bone grafting

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Patient Monitoring

Serial radiographs are used to assess progression toward union.

Historically, imaging may be obtained approximately every 4 weeks, although the interval should be individualized according to:

Fracture location

Treatment method

Symptoms

Expected rate of healing

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CT Monitoring

CT may occasionally be required when:

Plain radiographs do not clearly demonstrate whether bridging bone is present.

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Clinical Healing

Progress should be assessed using both imaging and clinical findings.

Important indicators include:

Reduced pain

Improved weight-bearing tolerance

Loss of abnormal motion

Improved limb function

Progressive radiographic bridging

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Key Principle

Successful treatment of fracture nonunion depends on identifying and correcting the underlying cause.

The central questions are:

Is infection present?

Is the biology adequate?

Is the soft-tissue envelope viable?

Is fixation sufficiently stable?

Is bone grafting or vascularized tissue needed?

When these factors are addressed systematically, most nonunions can ultimately be brought to union.