Humeral nonunion: causes, diagnosis and treatment

What is humeral nonunion?

A humeral nonunion is a complication in which a humerus fracture fails to heal properly despite the passage of the time normally required for bone union. In practical terms, the bone fragments fail to unite in a stable manner and abnormal movement may persist at the fracture site, associated with pain, weakness and functional limitation of the upper limb.

Nonunion can affect different areas of the humerus: the proximal region, the humeral shaft or the distal region. Humeral shaft nonunion is one of the forms most frequently treated in reconstructive surgery, particularly after complex fractures, previous operations or failure of fixation devices.

When a humeral fracture has developed a true nonunion and the healing process has stopped, spontaneous union is unlikely. To achieve bone healing, it is generally necessary to identify and correct the mechanical, biological or infectious problem that prevented the fracture from healing. Depending on the case, treatment may involve plate and screws, intramedullary nailing, autologous bone grafting, external fixation or more complex reconstructive procedures.

Why can a humerus fracture fail to heal?

Healing of a humerus fracture requires a combination of mechanical stability and an adequate biological capacity to form new bone. When one of these elements is insufficient, healing may progressively slow down and eventually stop.

In some patients, the problem is mainly mechanical: the fracture remains excessively mobile, the fixation device does not provide sufficient stability, or deformity, a gap or inadequate contact between the bone fragments is present.

In other cases, the main problem is biological and may be related, for example, to high-energy trauma, open fractures, soft-tissue damage, reduced blood supply, previous surgical procedures or bone loss.

Another factor that must always be excluded is the presence of infection, which may be obvious or relatively subtle and may present mainly as failure of the fracture to heal.

What are the main causes and contributing factors of humeral nonunion?

high-energy trauma;
open fractures;
fracture instability;
insufficient stability of fixation devices;
loss of contact between the fragments;
infection;
reduced blood supply;
bone loss;
previous surgical procedures;
smoking;
diabetes and other conditions that may interfere with bone healing.

Symptoms of humeral nonunion

persistent pain at the fracture site;
pain when using the arm;
weakness of the upper limb;
difficulty with everyday activities;
abnormal movement at the fracture site;
deformity of the humerus;
a feeling of instability;
possible loosening or breakage of fixation devices.

In some cases, the patient may still be able to use the arm partially, but persistent pain, weakness or instability after several months should raise suspicion of failure of the humerus to unite.

Diagnosis

specialist orthopaedic assessment;
X-rays of the humerus;
CT scan when a more detailed assessment of bone union is required;
blood tests when infection is suspected;
microbiological samples in suspected cases or during revision surgery.

Diagnosis does not simply consist of confirming that the bone has failed to heal. It is necessary to understand why the fracture has not united: insufficient stability, biological impairment, deformity, bone loss, infection or a combination of these factors.

Types of humeral nonunion

Type	Characteristics	Main treatment
Hypertrophic	Biologically active but unstable bone	Improved stability and compression
Atrophic	Reduced biological healing capacity	Stabilisation + bone graft
Infected	Presence or suspicion of infection	Debridement + stabilisation + reconstruction
With bone loss	Bone defect	Individualised bone reconstruction

How is humeral nonunion treated?

Treatment of humeral nonunion depends on the cause of the failed healing, the location of the fracture, bone quality, the presence of deformity, the condition of the soft tissues and the possible presence of infection.

There is therefore no single technique suitable for every patient. The aim is to achieve both adequate mechanical stability and a biological environment favourable to new bone formation.

Treatment of humeral nonunion with plate and screws

A plate and screws is one of the most commonly used techniques for treating humeral nonunion, particularly shaft nonunions.

A plate can provide high stability and controlled compression at the nonunion site, while also allowing correction of any humeral deformity.

During surgery, it may be necessary to remove fibrous tissue between the bone ends, prepare the bone surfaces until viable tissue is reached and restore good contact between the fragments.

In atrophic nonunions or cases with reduced biological healing potential, plate fixation is frequently combined with an autologous bone graft.

Autologous bone graft

An autologous bone graft can be used when the biological healing potential of the nonunion needs to be improved.

The bone is harvested from the patient’s own body, commonly from the iliac crest or using other techniques, and is placed around the nonunion site after appropriate preparation of the area.

A bone graft does not replace proper stabilisation: biology and stability must be addressed together to achieve reliable union.

Intramedullary nail

An intramedullary nail may represent a treatment option for certain types of humeral nonunion, particularly when the location and fracture morphology make its use appropriate.

In patients previously treated with a nail, revision of the fixation may need to be considered, but simply replacing the device without identifying the cause of failed healing is not sufficient.

In some situations, a plate provides more direct control of the nonunion site, better compression and more precise correction of alignment.

Ilizarov surgery

Surgery based on the principles of Ilizarov is an established option for treating humeral nonunion, particularly in complex cases such as infected nonunions, those associated with deformity or shortening, or cases that have already undergone previous surgery without achieving union. The method uses a circular or semicircular external fixator that provides effective stabilisation of the humerus and allows controlled compression at the nonunion site, promoting the mechanical and biological conditions required for healing.

One of the main advantages of the technique is the ability to progressively modify the correction during treatment, addressing instability, deformity and, when necessary, limb-length differences or bone defects at the same time. In infected nonunion, it also allows debridement of compromised tissue and stabilisation without necessarily placing internal fixation material within the infected area.

The scientific literature reports high union rates even in patients who have already undergone previous surgical procedures, although outcomes depend on the complexity of the nonunion, the presence of infection and the characteristics of the individual case. The technique requires specific expertise and careful follow-up during treatment, particularly for pin- and wire-site management and protection of neurovascular structures, especially the radial nerve.

Humeral nonunion after failure of previous surgery

Some patients present after one or more surgical procedures that failed to achieve bone union.

In these cases, it is particularly important to reassess the problem completely and determine whether there is residual instability, deformity, bone loss, infection or biological impairment at the nonunion site.

Revision surgery may require removal of previous fixation devices, new stabilisation and the use of bone grafts or other reconstructive techniques.

The radial nerve in humeral nonunion surgery

One of the most delicate aspects of humeral surgery is the relationship with the radial nerve, which runs in close proximity to the humeral shaft.

Previous operations, scar tissue, deformity or fixation devices may alter normal anatomical relationships and make revision surgery more complex.

For this reason, during revision surgery for humeral nonunion, particular attention must be paid to the identification and protection of the radial nerve.

Infected humeral nonunion

Infected humeral nonunion requires a different strategy from aseptic forms.

Treatment may involve thorough surgical debridement, removal of non-viable tissue, collection of several deep microbiological samples and, when necessary, removal of contaminated fixation material.

At the same time, adequate stability of the humerus must be ensured because infection control and mechanical stability must be addressed together.

In the most complex cases, treatment may require several surgical stages and specific reconstructive techniques.

When is an external fixator used for humeral nonunion?

External fixation is particularly useful in the most complex humeral nonunions, especially when there is infection, deformity, bone loss, severe soft-tissue compromise or failure of previous surgical procedures. In these situations, it may be preferable to avoid placing new internal fixation devices in the nonunion site and to use an external fixator to achieve both stability and progressive control of correction.

In aseptic humeral nonunions without major bone defects or deformity, however, internal fixation with plate and screws, potentially combined with bone grafting, is frequently an effective solution. The choice between internal and external fixation must therefore be based on the characteristics of the nonunion and any previous treatments.

Humeral nonunion with bone loss

When nonunion is associated with bone loss, treatment becomes more complex because stabilising the fracture alone is not sufficient: the missing bone segment must also be reconstructed.

The strategy depends on the size of the defect, the presence of infection, tissue quality and previous surgical procedures.

Possible options include bone grafts, the Masquelet induced membrane technique, external fixation and other reconstructive procedures, selected according to the characteristics of the individual case.

Induced membrane: Masquelet technique

The induced membrane technique, or Masquelet technique, can be used in selected patients with humeral nonunion associated with bone loss.

Treatment is generally performed in two stages. During the first procedure, the nonunion site is debrided and the defect is temporarily filled with a cement spacer. Over the following weeks, a biologically active membrane forms around the spacer.

During the second procedure, the cement is removed while preserving the membrane, and the defect is filled with bone graft with the aim of promoting reconstruction of the missing segment.

How long does recovery take after treatment of humeral nonunion?

Recovery time depends on the complexity of the nonunion, the technique used, the presence of infection, any associated bone loss and the number of previous surgical procedures.

In relatively straightforward cases, union may be achieved within a few months. Infected nonunions, large bone defects or cases that have already undergone multiple previous procedures may require a considerably longer treatment pathway.

During treatment, regular radiographic follow-up and a rehabilitation programme aimed at maintaining mobility of the shoulder, elbow and upper limb are essential.

Can full arm function be recovered?

Yes, in many cases. The goal of treatment is not only to achieve radiographic union of the humerus, but also to restore a stable, pain-free and functional limb.

The functional outcome also depends on the condition of the shoulder and elbow, the duration of the nonunion, the presence of neurological injuries, the severity of the original trauma and the number of previous procedures.

Appropriate physiotherapy is particularly important for progressively restoring strength and mobility after union.

What complications can occur?

As with any surgical procedure, treatment of humeral nonunion may be associated with complications.

Possible complications include persistent nonunion, infection, loosening or breakage of fixation devices, stiffness of the shoulder or elbow and neurological complications.

Particular attention must be paid to the radial nerve, especially during revision surgery, where scar tissue and altered anatomy may increase surgical complexity.

Proper surgical planning and identification of the cause of the nonunion help reduce the risk of another failure.

When should you see a specialist?

A specialist assessment is advisable when a humerus fracture shows no radiographic progression towards union, continues to cause pain after several months, or is associated with deformity, instability, breakage of fixation devices or suspected infection.

Assessment is particularly important in patients who have already undergone one or more surgical procedures without achieving healing.

In these situations, simply replacing the fixation device is not sufficient: it is necessary to understand which mechanical, biological or infectious factor caused the previous treatment to fail.

FAQ about humeral nonunion

Can humeral nonunion heal?

Yes. In many cases, union of the humerus can be achieved through appropriate stabilisation combined, when necessary, with bone grafting or other reconstructive techniques.

What is the most commonly used treatment?

In aseptic humeral shaft nonunions, one of the most commonly used strategies is plate fixation combined, when indicated, with autologous bone grafting. However, the choice depends on the characteristics of the individual case.

Is bone grafting always necessary?

No. The need for bone grafting mainly depends on the biological characteristics of the nonunion, bone quality and the presence of any bone defects. It is particularly useful in atrophic nonunions.

Can humeral nonunion be infected even without drainage?

Yes. Some infections may be relatively subtle. For this reason, specific investigations and deep microbiological samples during surgery may be required in suspected cases.

Can the radial nerve be involved?

Yes. The radial nerve runs close to the humeral shaft and is an especially important anatomical structure in humeral surgery. During revision procedures it must be identified and protected with particular care.

How long does healing take?

Healing time varies depending on the complexity of the case. Straightforward nonunions may unite within a few months, while infected nonunions, large bone defects or cases that have already undergone multiple procedures may require a longer treatment course.

Can arm mobility be restored?

In most cases, the goal is to restore good upper-limb function. The final outcome also depends on the condition of the shoulder, elbow, muscles and nerves.