Non union is a delayed complication of fracture. Literally it means absence of union. But by definition a bone can be labeled as in non union only when the union has not occured in the bone even after passage of sufficient time [in which the bone normally would have united]. Fractures of shaft of long bone should not be considered nonunion until at least 6 months post injury but in contrast, a central fracture of the femoral neck can sometimes be defined as a non union after only 3 months
Causes of Non Union
There is a long list of causes of non union. These are patient related like age, injury related like open fractures and treatment related. Few of them are modifiable and others are not.
Patient Related Factors
- Older age
- Poor nutrition
- Steroid therapy
- Radiation therapy
- Anticoagulant therapy
- High alcohol intake
Injury Related Factors
- Open injuries
- Soft tissue interposition
- Bone loss resulting in gap
- Compromised blood supply following injury to nutrient artery
- Stripping injury to muscle and periosteum
- Severe comminution
Treatment Related Factors
- Inadeuqate immobilisation
- Distraction of fragments from traction or internal fixation
- Malposition of fragments
- Implant failure
Callus is formed, but the bone fractures have not joined. This can be due to inadequate fixation of the fracture or inadequate mobilisation. Fracture is capable of a healing response to injury.There is increased uptake on radionuclide scans.
Oligotrophic non unions
The callus is absent and occur after major displacement of fractures, distraction of fragments, or internal fixation without accurate apposition of fragments. Blood supply is usually good. They demonstrates uptake on radionuclide scans but the healing response is inadequate.
No callus is formed. This is often doe to impaired bony healing due to decreases blood supply. They show radionuclide uptake failure.
Gap non union
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. Occur after open fractures, sequestration in osteomyelitis, and resection of tumors;
Diagnosis is made on clinical examination and xrays. On clinical examination, the fracture fragments would show relative mobilitya and there would be absence of tenderness on the fracture site. Absense of tenderness differentiates non union from delayed union and denotes absence of any biological activity.
Xrays would show
- Absence of bone crossing the fracture site (bridging trabeculae)
- Sclerotic fracture edges
- Persistent fracture lines
- No changes toward union on serial xray
Presence or absence of callus is not a very reliable finding especially in cases of rigid fixation.
Nonunion is a failure of healing process. The treatment principle is to augment the healing process by freshening the ends of bone and one grafting and provide adequate immobilisation.
Typical treatment of non union is surgical. Following are the essential steps
- Exposure of fracture site
- Freshening of sclerotic edges to get a bleeding surface.
- Opening of intramedullary cavities of fragments to facilitate flow of blood circulation
- Rigid fixation
- Bone grafting to augment bone healing
- External splinatge if required.