ENHANCEMENT OF FRACTURE-HEALING BY MECHANICAL AND SURGICAL INTERVENTION

Mechanical modulation of bone fracture repair and restoration to its s tructural strength must rely on the fundamental physical concept of re modeling according to the type of stress applied to immature or undiff erentiated tissue. This article proposes the possible mechanisms of in teraction between physical factors and cellular responses in healing l ong bone fractures and speculates on the advantages and limitations of different experimental models in evaluating these interactions. A rev ised classification system of fracture union types based on histomorph ologic characteristics is introduced here as a reference standard in t he studies of possible accelerating factors. Bone fracture union can f ollow more than one or two pathways, with various combinations of bone formation mechanisms, whereas there may be only one bone remodeling p rinciple. There are definite mechanical and operative interventions th at can provide effective enhancement to fracture healing. However, dif ferent intervention may limit its association to a specific healing me chanism. The key element in establishing these interactions is definin g the precise cellular and molecular mechanisms in a quantitative mann er. This can be achieved best by interdisciplinary research collaborat ions working on a higher level of expertise in each related field usin g standardized experimental models. Not only a basic understanding of the associated cellular reactions is necessary, but also the specific forms of mechanical stimulation, the dose effect, and its application timing must be determined and validated. Without this basic research e ffort, it would be difficult to transform such an augmentational modal ity into effective and reliable therapeutic regimens for clinical appl ication. Furthermore, successful fracture repair enhancement must have proper new bone formation maintenance and remodeling through physiolo gic loading, or the initial stimulation process may be short lived and unable to reestablish the required biomechanical strength of the long bone. Finally, there is no substitute for a well organized and carefu lly controlled prospective clinical trial in establishing the validity of any bone fracture healing enhancement modality, regardless of its nature and form of application.