ASSESSMENT OF BONY UNION

The actual determination of bony union is more a clinical than a radiologic judgment. The ratio of cancellous to cortical bone is of prime importance: cortical midshaft fractures take longer to heal than those of the cancellous metaphyseal type. For hand fractures, the healing cancellous fracture is generally stable in 3 weeks and the midshaft cortical fracture in 4 weeks. This varies with the type of injury, the degree of ischemia, the adequacy of bony contact, and the presence of extensive soft tissue injury or infection. Clinical unity is shown by a lack of motion or tenderness with stress at the fracture site. At this point, implants such as Kirschner wires can be removed. A reduction in therapy is sometimes made for 7 days, and the fracture reassessed at 1 week. If the injury includes more extensive soft and hard tissue damage, there is an anticipated delay in healing, and the fracture is then stabilized for an additional 1 to 2 weeks.

Radiologic signs of early bone healing show only loss of definition of the fracture edges because of resorption of dead bone. If callus formation is required, it begins to appear at 3 to 4 weeks with calcification beyond the cortical margins. Within 6 to 8 weeks, the bone is undergoing reorganization, and x ray shows a loss of the fracture line. Failure of the x ray to demonstrate these sequential changes, or the appearance of increased callus or translucency at the fracture zone, indicates an implant failure with motion at the fracture site. Corrective steps should be taken to reduce the external stresses by either adding external splints or reinforcing the internal splinting of the implant.

COMPLICATIONS

Complications from bony fixation may influence the overall success of replantation in the postoperative period. Rough, hasty application of the implant increases the possibility of damage to the adjacent soft tissue and underlying periosteum. The poorly reduced bone and the fixation implant are subject to unbalanced micro and macro stresses in the postoperative period, and unnecessary motion may compound a poor reduction, leading to further problems and pain. Once vascular homeostasis has been achieved, the bone-implant interface may be well on its way to failure. Collapse of the reduction removes any ability of the bone to share the stress load, causing further stress on the implant and the bone-implant interface. Additional external splinting must be applied, blocking therapy and placing the entire extremity at risk for further stiffness. At best, a delayed union occurs, with significant callus formation impinging on surrounding soft tissues. Non-union or osteomyelitis may require reoperation.

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