Bone and Joint
Biomechanics Lab

University of Wisconsin-Madison

1513 University Ave.
Madison, WI 53706

(608) 263-6692

last update: 6/5/12

Determination of the dynamic load required to promote bone consolidation during limb lengthening and/or fracture repair


Thousands of children are born each year in the United States, and many more worldwide with limb length inequalities.  Many more suffer injuries or infections which affect future growth and leave them with similar limb deformities.  Correction for such leg length discrepancies, as well as congenital and trauma-induced angular deformities, is frequently accomplished via a technique known as distraction osteogenesis (DO). DO is characterized by a primary osteotomy followed by slow separation of the cut ends of the bone, allowing the bone to lengthen (and/or straighten) as it heals. 

During the reparative phase of fracture healing, development and maintenance of the provisional callus, a malleable cartilaginous network splicing the broken bone fragments together, is vital to the success of DO procedures. Resorption or premature calcification of the callus during DO significantly affects the healing time as the callus would either need to redevelop prior to further lengthening or be recreated from a second osteotomy, depending on the degree of ossification.

However, consolidation of the provisional callus to bony callus, promoted by mechanical loading, is required prior to end-stage fracture healing. This remodeling phase results in restoration of the original contour and internal structure of the bone, prior to fracture. Studies have shown that regulating either strain rate or loading frequency results in a more effective application of the mechanical load necessary to promote bone growth, ultimately yielding a greater and more rapid amount of bone formation.

The primary purpose of this research is to determine the optimal magnitude and rate of an applied dynamic load in order promote the conversion of the provisional callus to bony callus during the reparative phase of fracture healing.  Further, a more extensive understanding of bone’s response to dynamic load will facilitate the development of limb lengthening devices that can reduce healing time. 

 

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