Nonunion

Nonunion is failure of fracture fragments to unite or heal. Generally it occurs when the fracture site has failed to heal completely by approximately 6 to 9 months after an injury. There are several causes of fracture nonunion: infection; insufficient immobilization; interposition of soft tissues between the fracture fragments; poor blood supply; poor nutritional status; open, comminuted, segmental, or pathologic fractures and many others. A false joint which is termed as pseudarthrosis develops. It has a motion like a joint. And due this persistent motion, it creates a synovium-lined cavity and soon filled with synovial fluid. For simplicity purposes we divide them into two major types: Infected and Non-infected nonunions. Congenital pseudarthrosis or nonunion is a special kind of pseudarthrosis which occurs in children without trauma in which the bone fractures spontaneously. It occurs mostly in the tibia and forearm. This subject is different from the subject of nonunion related to fractures or surgery.

Treatment options :

Nonunion Secondary to Infection
Open fractures which result to bone infection will eventually lead to nonunion. This remains a challenge to Orthopaedic surgeons. Because aside from the problem of eradicating the infection per se, nonunion has to be addressed as well. The treatment requires removing the dead infected bone which results to a bone defect or gap. If infection is not controlled and affected bone is large, amputation is likely considered as treatment. For limb salvage, the Ilizarov method is utilized. It can correct the bone defect or gap whatever size it may be and is therefore preferable than amputation. This consists of removing all the necrotic debris of the affected bone up to its healthy borders and application of Ilizarov ring construct for limb lengthening. This is accomplished by two different ways. One is by acute (immediate) shortening of the limb. This way it eliminates the bone defect immediately. A second surgery is necessary for lengthening of the bone. This is performed when infection is already controlled and is done with corticotomy (cutting the bone) at a site far from the previous infection. With gradual distraction of the bone ends using the Ilizarov construct, bone is lengthened to its desired length and the bone gap is filled with bone regenerate or new bone. An alternative option is called bone transport by which after removing the infected part of the bone, corticotomy is done at a different site. The free fragment then is being transported to meet the other end of the bone without changing the length of the limb at all. It is usually necessary to place bone grafts at the final docking stage which is a separate operation to expedite union. Both immediate shortening and bone transport result in equal limb length and normal alignment and most importantly a solidly united bone which is functional.

Non infected Nonunion
If nonunion occurs without infection, it is called aseptic nonunion. There two primary types of aseptic nonunion based on radiographic appearance, atrophic (avascular) and hypertrophic (hypervascular). The management is different for each type. In the hypertrophic type of nonunion, stability of the fracture is what is only needed because the osteogenic stimulus is present. Whereas in the atrophic or avascular nonunion, there is no osteogenic stimulus and therefore aside from stability of the fracture, bone grafting is necessary as well. A clinical classification of nonunion into stiff and mobile is also useful. Clinical assessment of the nonunion is done by gentle manipulation of the nonunion area. If no motion is elicited then it is called stiff, whereas when motion occurs it is called mobile. Usually, hypertrophic non unions are stiff and atrophic non unions are mobile.
Treatment for hypertrophic (hypervascular) or stiff nonunion entails only obtaining stability by either internal or external fixation. Internal fixation with use of plates and screws affords stability at the cost of stripping or devascularizing the nonunion site. With internal fixation, bone grafting is almost always necessary. The Ilizarov method does not require opening up the nonunion site. And it does not only afford the needed stability but also accomplishes compression which expedites the union process. For atrophic nonunion, osteogenic stimulus is provided by doing corticotomy (cutting the bone) above or below the nonunion area. With subsequent distraction, the blood flow to the nonunion area is increased and therefore healing is being initiated. About ninety percent achieve union without bone grafting.