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Fracture Fixation
by Tim B Hunter, MD, MSc
Introduction
Bone fractures can be complete or incomplete, simple or comminuted, closed or open. Comminuted fractures comprise more than two bone fragments, and open fractures are associated with an open skin wound (Ruedi, 2007). Many fractures are treated non-operatively.
However, a large number of fractures require operative
treatment. If a fracture that requires operative
treatment is not treated, nature tries to stabilize
the mobile fragments by pain-induced contraction
of the surrounding muscles, which may lead
to bone shortening. The end result of this process
frequently is the lack of proper bone alignment
and impaired function, malunion or nonunion (Ruedi, 2007; Benjamin, 1994; Wiss, 2013; Berquist, 1995; Freiberg, 2001; Hunter, 2001).
Stability (stiffness) represents the displacement between fixed fracture fragments when a physiologic load is applied. A stable fracture does not displace under a physiological load. Stability is a principal determinant of whether a fracture is treated conservatively or operatively (Bartolotta, 2019).
The basic goals of fracture fixation are to stabilize
the fractured bone, enable fast healing of the
injured bone, and return early mobility and full
function to the injured extremity. For lower extremity
fractures, stability for weight bearing is
the main goal. In the upper extremity, restoration
of functional hand and arm motion is most important.
For diaphyseal fractures, proper alignment
of the fracture fragments is all that is needed
for adequate function and prompt healing of the
fracture, whereas intra-articular fractures require
precise anatomic reduction with articular congruency
being paramount.
Direct or primary bone (fracture) healing occurs when absolute stability is maintained after an anatomic reduction is achieved, and the fracture ends are compressed together. Direct bone healing requires there be no gap or motion at the fracture site. In this mode of bone healing, the standard bone turnover process continues as if no fracture is present. The fracture heals directly with new bone formation. The hallmark of this type of healing is the fracture line disappears without the formation of callus.
Indirect or secondary bone (fracture) healing occurs through a cartilage intermediate. Motion at the fracture site creates a micro-environment which causes healing to proceed through several phases: a) inflammation, b) soft callus formation which is predominated by cartilage that helps reduce the motion/strain at the fracture allowing for bone deposition with c) transition to hard callus formation, and finally d) bony remodeling.
There are two main types of fracture fixation:
internal and external. All internal and external
fixation methods that allow appreciable interfragmentary
movement under functional weight bearing
are considered flexible fixation. Techniques
that use compression are considered rigid fixation
(Ruedi, 2007; Benjamin, 1994; Wiss, 2013).
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