Nonunion and Malunion- Causes and Treatment

Last Updated on February 7, 2025

Malunion and nonunion are complications of fracture treatment. Nonunion of fracture is a delayed complication of fracture. Literally, it means the absence of a union. But by definition, a bone can be labeled as in nonunion only when the union has not occurred in the bone even after a passage of sufficient time [in which the bone normally would have united].

Fractures of the shaft of long bone should not be considered nonunion until at least 6 months post-injury but in contrast, a central fracture even after 3 months.

After the fracture has occurred, the body initiates a complex overlapping sequence of events, including inflammation, repair, and remodeling.

This sequence can restore the normal bone structure, biologic function, and mechanical strength in patients of any age.

Despite the potential for a successful hearing through regeneration of normal bone, certain types of bone injury and, in some instances, the treatment of bone or soft tissue injury, lead to complications such as delayed union, nonunion, malunion, or bone necrosis that prevent the timely healing.

These complications of fractures and their treatment are inevitable in some patients, but it is possible to avoid or minimize complications, and becomes important to diagnose and treat them.

Definitions

[More about fracture healing and factors affecting it]

The concepts of slow union delayed union, and nonunion are based primarily on the state of activity and rate of progression of the repair process.

Slow Union

This term basically implies that fracture union is present but slow.

A slow union does not result necessarily in a delayed union or nonunion. Such fractures often unite if immobilization is maintained long enough.

Delayed Union

The term delayed union refers to a fracture in which repair is not complete within the interval expected for that specific fracture.

A delayed union, if given a proper milieu, has the potential to unite.

Nonunion

A nonunion exists when repair is not complete within the period expected for a specific fracture, and cellular repair activity at the fracture site ceases.

Clinically, it is diagnosed when a repair process has stopped completely and the union will not occur without therapeutic intervention.

This cessation of activity is the most important feature that differentiates between non and slow/delayed union.

In an established nonunion, sclerosis develops around the bone ends and the medullary canals are sealed off. The bone ends are joined by dense fibrous tissue.

For a fracture of the shaft of a long bone in an adult, at least 6 months must elapse after the injury before this diagnosis can be made.

Once nonunion has occurred, the fracture would not unite without intervention.

How Important are Time Frames?

The terms slow union, delayed union, and nonunion all imply a time frame. This time frame depends on the factors that influence the rate of fracture healing, including the location of the fracture and the amount of soft tissue injury.

However, time elapsed since the injury was used in classical definitions and was important for defining surgical indications.

In the past, surgery was done only in cases where all possibility of healing without intervention was nil.

But with changing times,  a more aggressive approach to obtaining fracture union often is taken, and the time frames are less important.

For example, surgery may be contemplated after 4 months of conservative treatment, although technically this does not meet the criteria for a nonunion.

Similarly, fractures that carry a high risk for nonunion may be grafted primarily. This is mainly done in open fractures and comminuted fractures.

From hereon, the main topic of discussion will be nonunion

What Causes Nonunion?

There are multiple factors responsible for the development of nonunion and all the factors responsible for the event may not be known.

Following adverse mechanical factors influence the development of nonunion

• Excess motion
  • Inappropriate stabilization
• Large interfragmentary gap
  • dIstraction by internal fixation or traction
  • The interposition of soft tissues
  • Loss of bone
• Loss of blood supply.
  • High-energy causes loss of the bony soft tissue envelope
  • Damage to nutrient vessels
  • Segmental or comminuted free fragments
  • Excessive periosteal stripping during hardware insertion.

Some bones like the scaphoid, distal tibia, and the base of the 5th metatarsal are at higher risk for nonunion due to the precarious blood supply in these areas.

Fracture patterns like segmental fractures and those with butterfly fragments are at increased risk of nonunion as the blood supply is compromised to the broken fragment.

There is a long list of causes. Few of them are modifiable and others are not.

• Older age
• Poor nutrition
• Steroid therapy
• Radiation therapy
• Anticoagulant therapy
• Smoking
• High alcohol intake
• Open injuries
• Soft tissue interposition
• Bone loss resulting in a gap
• Compromised blood supply following an injury to the nutrient artery
• Stripping injury to muscle and periosteum
• Severe comminution
• Infection
• Inadequate immobilization
• The distraction of fragments  from traction or internal fixation
• Malposition of fragments
• Implant failure

Types of Nonunion

Hypertrophic nonunion

A callus is formed, but the bone fractures have not joined. This can be due to inadequate fixation of the fracture or inadequate mobilization is capable of a healing response to injury.

A radionuclide will show an increased uptake signifying healing activity.

A hypertrophic callus is a sign of motion and the union will occur rapidly when motion is stopped by stable internal or external fixation devices. A bone graft usually is unnecessary.

Oligotrophic nonunion

The callus is absent. It occurs after major displacement of fractures, a distraction of fragments, or internal fixation without correct apposition of fragments.

Blood supply is usually good.

They demonstrate uptake on radionuclide scans but the healing response is inadequate.

Atrophic nonunion

No callus is formed. This is often due to impaired bony healing due to decreased blood supply. They show radionuclide uptake failure.

The bone remains avascular or is revascularized very slowly or poorly.

If alignment is good and there is no gap, then stabilization under compression, with shingling and bone grafting, will stimulate the fracture healing process.

If there is malalignment or a gap, resection of the scar tissue is essential followed by eduction, shingling and stabilization and bone grafting.

Gap nonunion

There is a  loss of a fragment of the diaphysis of a bone. The ends of the fragments are viable but as time passes the ends of the fragments become atrophic. Occurs after open fractures, sequestration in osteomyelitis, and resection of tumors.

Pseudarthrosis

The term pseudarthrosis implies a nonunion with false joint formation in which the medullary canal is sealed off, with new cartilaginous surfaces covering the bone ends and the nonunion surrounded by a fibrous capsule having a synovial lining.

Pseudarthrosis means a false joint.

Diagnosis

Diagnosis is made on clinical examination and x-rays. On clinical examination, the fracture fragments would show relative mobility and there would be an absence of tenderness on the fracture site.

The absence of tenderness differentiates nonunion from a delayed union and denotes the absence of any biological activity.

Xrays would show

• The absence of bone crossing the fracture site (bridging trabeculae)
• Sclerotic fracture edges
• Persistent fracture lines
• No changes toward union on serial x-ray

The presence or absence of callus is not a very reliable finding, especially in cases of rigid fixation.

Treatment

The treatment principle is to augment the healing process by freshening the ends of the bone and bone grafting and providing adequate immobilization.

Some superficial fractures may respond to bone stimulation which may be tried as part of nonoperative treatment. Few selected nonunions may be tried with fracture brace immobilization

Contraindications to non-operative treatments are

• synovial pseudoarthroses
• Nonunions that move
• Greater than 1 cm gap between fracture ends.

Operative Treatment

Typical treatment of nonunion is surgical. Following are the essential steps

1. Exposure of the fracture site
2. Freshening of sclerotic edges to get a bleeding surface.
3. The opening of intramedullary cavities of fragments to facilitate the flow of blood circulation
4. Rigid fixation
5. Bone grafting to augment bone healing
6. External splintage if required.

The approach to different nonunion treatments is as below

• Hypertrophic
  • biologically viable bone ends
  • It May be treated with internal fixation to provide mechanical stability
  • Bone grafting may not be required.
• Oligotrophic/ Atrophic
  • It May require biological stimulation along with internal fixation
  • Bone graft taken from the autologous iliac crest is the gold standard.
• Infected
  • The first step is to control infection
  •  A staged approach required
  • It May require external fixation and debridement till the infection heals
  • Usually followed by internal fixation and bone grafting
• Pseudoarthrosis
  • Removal of atrophic, non-viable bone ends
  • Internal fixation with mechanical stability. Soft tissue coverage procedures may be needed.

Fixation Methods

• Internal Fixation
  • Screw Fixation
    • May be used as interfragmentary screws along with neutralization plate
• Plate Fixation
  • Plate fixation may be used with or without cancellous bone grafting
• Intramedullary Nailing
  • Intramedullary nailing is mainly used for nonunions of the lower limb.
  • In open nailing, bone grafting is added.
• External Fixation
  • The use depends on the type of nonunion.
  • Treatment of bone losses of 3 cm or more may require bone transport with the Ilizarov ring fixator.
• Combined Internal and External Fixation

Bone Grafting 

Autogenous bone remains, even to­day, the best bone grafting material. Bone grafting can be nonvascularized or vascularized.

Bone grafting can be used as an isolated pro­cedure, associated with internal or external fixation.

Depending on the indi­vidual case, packing cancellous bone chips in and around the nonunion may suffice, or it may be combined with a structural corticocancellous graft. A nonvascularized segment of the fibula may be used as a graft to fill a large bone defect in the radius or ulna.

Vascularized autografts are effective but require microvascular techniques.

Biophysical Stimulation

• Electrical Bone Stimulators
• Orthobiologics
  • Biological substances that are used to help injuries to heal more quickly.
  • Autogenous Bone Marrow
  • Platelet extract

Infected Nonunions

Infected nonunions become a special case because infection needs to be controlled before the union could occur. Infected non-union is characterized by

• Atrophic radiographic appearance
• Poor fracture vascularisation
• Inadequate soft tissue coverage
• Loose fixation

These require aggressive patient management.

The treatment includes antibiotics, local debridement, stabilization [often external first, followed by internal],  repair of the defect to control the infection, soft tissues and bone reconstruction surgeries when needed.

When active drainage is ongoing, healing will be longer and more difficult.

If drainage has not occurred for 3 or more months and the wound is quiescent, the infected may be treated as atrophic .

Clavicle

Symptomatic nonunions of the middle third of the clavicle should be treated by the application of a plate and iliac bone graft. When the nonunion is within 4 or 5 cm of either end, the short fragment may be resected.

Humerus

In young Nonunited fractures of fracture-dislocation of the proximal humerus should be treated by fixing the proximal fragment with a proximal humeral plate. Liberal use of methylmethacrylate cement if needed may be done.

Cancellous bone grafting, best obtained from the iliac crest may be used for grafting.

Successful treatment for these nonunions is difficult.

Prosthetic replacement of the head of the humerus may be considered primarily in old patients or after failed surgery in young patients.

For humeral shaft fractures, the recommended treatment is plate and screw fixation with bone grafting. But in older patients, the physical condition of the patient should be considered and diminished function because of a nonunion may be pref­erable to the risks of ORIF in some cases.

In such cases, orthosis may help.

For atrophic ununited diaphyseal fractures of the humerus with a bony defect

Nonunions of the distal humerus should be treated by means of two contoured 3.5-mm reconstruction plates, one placed medially, and the other placed posterolaterally.

Total elbow arthroplasty may be con­sidered only as a salvage procedure.

For nonunion of the capitellum, excision may be done.

Radial neck

Radial neck fracture nonunion is rare. Observation, radial head, and neck excision, or ORIF with bone graft may be considered, depending on the level of pain, deformity, and functional restriction.

Radius and ulna

In proximal and midshaft nonunions, a compression plate and cortical screws should be used for fixa­tion.

Distal radius nonunions should be treated by a volar or dorsal small T plate as a buttress.

Carpal scaphoid

Nonunion of the carpal scaphoid may be treated by trap­ezoidal bone grafting and internal fixation. K wires, AO cannulated screw, Herbert screw has been used successfully.

Femur

For femoral neck fracture nonunions, prosthetic replacement is the best treatment, especially in elderly persons.

In younger people, an attempt should be made to achieve union. Valgus intertrochanteric osteotomy is the best method for that. A dynamic hip screw should be used for fixation, as well as a bone graft at the non­union site.

Nonunion of intertrochanteric fractures is tackled by a medial displacement and valgus osteotomy.

Subtrochanteric fractures nonunions are difficult to treat and treated by intramedullary locked device or dynamic hip screw or dynamic compression screw.

Fractures of the femoral shaft can be treated by intramedullary nailing or plating and bone grafting.

Supracondylar fracture nonunions may be treated by intramedullary nails or a 95° dynamic condylar screw.

Condylar buttress plate is another choice.

 

Tibia

Proximal tibial fracture nonunions usually are treated by internal fixation using tibial plating and bone grafting.

Nonunions of the tibial shaft fractures are treated best by intra­medullary nailing or plating. While in hypervascular nonunions, the graft is not required,  in avascular nonunions, decortication of the bone ends and bone grafting should be done.

Nonunited pilon fractures of the lower tibia and fibula can be salvaged by intraarticular osteotomy and lag screw fixation with bone grafting. Ankle fusion and stabilization is considered in arthritic joints.

Malunion refers to fracture union in an abnormal position. The abnormal position may be shortened, lengthened, angled, or rotated.  The condition may result in, though not always, insufficient or abnormal function and cosmetically unacceptable limb.

Malunion may cause alteration of normal dynamics of joint motion.

For example, limited pronation-supination after forearm fractures or the development of pelvic obliquity, scoliosis, and back pain secondary to leg-length inequality.

The condition may be the result of inaccurate initial reduction or loss of position because of inadequate immobilization.

In physeal fractures of children, physeal damage or growth disturbances may result in deformities.

The clinical problems presented by malunion of long bones differ

• According to their location
  • Diaphyseal and metaphyseal
  • Articular surface
• Skeletal maturity of the patient
  • Child
  • Adult

Diaphyseal and Metaphyseal Malunion

The abnormal position of a healed fracture alters the biomechanics of a specific joint by shifting the load-transfer axis. The abnormal joint mechanics lead to joint instability and cause local stress overload on the articular cartilage.

Both instability and increased or abnormal loads can increase the probability of post-traumatic arthrosis, especially in weight-bearing joints.

However, the degree of gross deformity is not always related directly to the degree of loss of function or to the long-term development of osteoarthrosis and for the same deformity, the function affected varies among the individuals.

The functional impairment also depends on the bone and its compensation offered by the body.

For example, a malunion of a proximal humeral fracture often results in minimal functional limitation and cosmetic irregularity.

The deformities near joints, especially those that are not in the plane of motion of the joint, may impair function seriously.

Rotational deformities are not apparent on radiographs, and may be disabling.

In lower limbs, shortening of a limb by more than 2.5 cm may present enough of a functional and cosmetic problem Diaphyseal and metaphyseal fractures in children can result in growth stimulation and overgrowth.to warrant shortening of the opposite limb or, in some circumstances, lengthening of the affected segment.

Diaphyseal and metaphyseal fractures in children can result in growth stimulation and overgrowth.

Malunion Involving Articular Surface

There is an established causal relationship between articular surface step off resulting from malunion of an intraarticular fracture and the development of arthrosis though the degree might vary from person to person.

Intraarticular malunions are less acceptable than diaphyseal/metaphyseal malunions. Therefore rigid criteria have been developed for different joints to serve as guidelines for intra-articular fractures.

Physeal and Epiphyseal Fractures

The possible consequences of injury to a physis and epiphysis are

• Progressive angular deformity
• Progressive limb-length discrepancy,
• Joint incongruity with resultant posttraumatic arthrosis

Physeal fractures are known to have the following causes of malunion

• Avascular necrosis of the epiphysis
• Crushing or infection of the physis
• Bony bridge formation
• Hyperemia
• Infection

Evaluation of Malunion

Clinical evaluation takes precedence over imaging and is able to determine degree of malunion and its functional effect.

Imaging requires assessing the degree of the malunion accurately and to plan any corrective measures. X-rays are sufficient in most cases. In physeal and intraarticular malunions, CT is helpful to present a 3-dimensional view for better surgical planning.

Treatment of Malunion

Not all diaphyseal and metaphyseal malunions require correction. Some do not affect the function and thus do not require treatment. In others, any correction may not help.

In epiphyseal and intraarticular malunions the role of surgery in correction is limited.

Each case has to be evaluated differently.

• Angular and rotational malunions are correctable by osteotomies
• Associated joint arthrosis often makes joint-ablating procedures such as arthrodesis or arthroplasty the only option.
• Joint realigning osteotomies sometimes may help.

Save

Save