Radiographic interpretation of bone healing complication

Malunion                                          

• Fracture malunion is not an unusual radiographic diagnosis. Unfortunately, it provides little objectivity to the clinical report. Malunion may be described as side to side, end to end, end to side, rotated or crossed union with adjacent bones. With adequate time and remodeling, a reasonable anatomical configuration may be achieved. 

• Malunion fractures that result in mechanical interference or functional impairment may require additional orthopedic correction (e.g., corrective ostectomy). (Figs. 1, 2 ) .

Delayed union

• A fracture that has delayed healing has the same radiographic description as one with secondary bone healing, but the healing is not progressing as rapidly as the orthopedist would like. There are multiple complication that may delay fracture healing, of which motion of apposing fragment is the most determinant, poor alignment of fragment require excessive callus which delay healing and remodeling, separated fragments may entrap other nonosteogenic tissue (eg., fat, muscle and connective tissues).

• Excessive gaps between fragment may result in fibrous nonunion. Bacterial contamination and inflammation may interfere with normal bone healing and may be so sever as to cause nonunion. The delay in healing is directly related to the severity of the factors involved. The most sever circumstance is nonunion.

•  The method for early detection of delayed union in lower leg fractures using a computerized analysis of mechanical vibration reactions of bone for assessing the state of fracture healing. The principle of a non-invasive method is based on evaluation of changes in mechanical vibration reactions.

• The assessment of 150 healthy individuals as well as an initial measuring series after treatment of tibial fractures with an external fixator system revealed highly significant differences between intact and fractured tibias. Thus, computerized sonometry is capable of supplying quantitatively recordable information about the stability of a fractured bone at any time in the healing process. Furthermore, this non-invasive technique allows early diagnosis of disorders in the repair process by the absence of change in the parameters.

Nonunion

• Regardless of the cause of fracture nonunion, the radiographic description may define the underlying problem.

• Apposed nonunion is usually the result of an unstable fracture environment or an extrinsic mechanical factor (e.g., a loose cerclage). The Fracture margins become well defined, and the medullary cavity may " plug" with sclerotic bone.

• The callus becomes smooth and nonreactive and is usually described as excessive or exuberant and flared or mushroomed profile at the fragment ends which may appear to articulate as complementary surface develop. The radiogic appearance is now typical for hypertrophic nonunion.

• Distracted or atrophic nonunions result from excessive space between fragment ends leads to interposition of soft tissue (cartilage or fibrous tissues).

• That can physically inhibit the development of the bridging calls or a marked disruption of the available blood supply. In this case little or no callus is present radiographically, fragment ends are diminished and reabsorbed becoming tapered and looking like a stylus.

• Infected non-union fractures may occur when there is reduced or deficient blood supply to the fracture site complicated by bacterial contamination.

• Radiographic signs are variable but usually include areas of callus and other areas of non reactive bone and absence of callus periosteal reactivity may be variable. Infected nonunion may be preceded by the presence of squestra, stoma or soft tissue tracts and cloaca.

• The surgical technique for treatment of biologically inactive nonunions using en bloc ostectomy and compression plate fixation with autogenous cancellous bone graft.

• A transverse ostectomy was performed adjacent and parallel to the nonunion to eliminate nonviable tissue and provide a new, viable fracture surface. Resection of bone was limited so that bone shortening was less than 20% of the overall bone length. With most of the bony column anatomically reconstructed, compression plate fixation was used to stabilize the fracture with grafting resulted in rapid bone healing without complication. (Figs.3, 4, 5, 6, 7) .

Osteomyelitis

• Wound infections in or thopedic surgery usually result from contamination of open fractures or from open fracture repair resulting in osteomyelitis and soft tissue infection.

•  The majority of infections are caused by bacteria; fungi are occasicnally involved, and parasite and virus rarely.

• Chonic osteomyelitis may result from sequestra or contamimation of implant. Radiography of acute osteomyelitis demonstrates proliferative new bone and occasionally gas in soft tissue sequestra may be suspected, but they do not become visible radiographically for several weeks or months. In chronic osteomyelitis.radiographic signs include new bone production with areas of lysis and often the presence of sequestrum.

• Poor surgical technique has been implicated as being the primary cause for posttraumatic infection. This includes gross contamination of the surgical wound, prolonged wound exposure, and improper treatment of wounds contamination from

• outside sources.

• Osteomyelitis can be expected where there has been overwhelming bacterial contamination in combination with sever trauma, presence of dead bone or where metallic implants are used especially if bone or implants are unstable. They added that. Haematogenous osteomyelitis account for approximately 19% of diagnosed cases in humans. While indogs is estimated at a prevalence of less than 10% .

• Posttraumatic osteomyelitis can occur in any breed of dog or cat and at any age. There appears to be slight predilection for young male animals due to the increased incidence of trauma in this subset and for long bones over bones of the axial skeleton, probably as a result of the increased incidence of the fracture in long bones.

• Consistent clinical manifestations of sever orthopedic infection include pain, erythema soft tissues swelling with or without drainge pain

• Traditional therapy for posttraumatic wound infections involves improvement of the wound environment and appropriate antibacterial therapy based on culturing and sensitivity. Appropriate drainage of site, removal of necrotic debris, purulent material and avascular bone segments through debridement is essential.

• Successful treatment of sever orthopedic infections in humans and other animals has been augmented by the use of antibiotic-impregnated polymethylmethacrylate (PMMA) bead implantation at the site of infection. High local wound concentrations of antimicrobials can be achieved without resulting in toxic levels systemically.(Figs. 8, 9, 10,11, 12) .

Complications of Fracture Repair

• Four complications of fracture repair will be discussed. These are: delayed union nonunion, malunion, and osteomyelitis. I delayed Union. Delayed union is difficult assess radiographically. It is a healing time longer than that considered normal the reviewer.

• Since opinions of healing time vary among veterinarians and others, the definition of delayed union must also vary. No specific radiographic changes are associated with delayed union, only a persistence of the fracture line and failure of the to bridge the gap. There may be an excessive periosteal component to the callus due to movement at the fracture site.

Nonunion

•  Nonunion of a fracture may be the result of any one or more of many specific circumstances. These include: improper reduction, the presence of foreign material at the fracture site, and excessive movement of the limb following reduction. radiographically, the attempts of the bone to heal may appear normal; however, as time progresses, it will be seen that callus is.

• Clinically, there may be much less movement at the fracture site than was anticipated from the radiographic appearance. This is usually due to fibrous proliferation surrounding the fracture with partial stabilization.

• Metallic fragments in the immediate area of the fracture frequently produce an extreme delay in union of a fracture.

• This chapter is devoted to miscellaneous lesions that can be radiographically demonstrated in large animals. In most instances such lesions require no discussion other than that contained in the captions for the illustrations.