Local tissue properties in bone healing: Influence of size and stability of the osteotomy gap

Abstract

To characterize the site-specific mechanical and histological properties in fracture repair and to relate these properties to the initial mechanical situation, an experimental fracture model was used in the metatarsus of 42 sheep. The mechanical situation of a transverse osteotomy was described by three gap sizes (1, 2, or 6 mm) and two amounts of strain (7 or 31%). An external fixator that allowed a defined axial movement provided control of these settings. Nine weeks following surgery, the healing area was dissected and tensile and compressive properties were measured in subregions of the fracture gap and the periosteal callus. The central, sagittal section was used for quantitative histology. We found the quality of the tissue along the osteotomy line to be most important for regaining mechanical stability. Increasing the size of osteotomy gaps resulted in poorer mechanical and histological qualities, and the repair process was less complete. Interfragmentary strain did not significantly influence the repair process. The smaller strain levels had already stimulated the secondary repair process, and this stimulatory effect could not be further enhanced by increasing the amount of strain. Our finding that large gaps between bone segments were not as well healed as were smaller gaps suggests that it is advantageous to avoid large gaps in fracture treatment.

Fracture healing in mice under controlled rigid and flexible conditions using an adjustable external fixator

“…These results confirm former studies demonstrating that the mechanical stability of the fracture healing zone is determined not only by callus size, but also by the local mechanical properties inside the callus. 20,21 In both cases, secondary healing occurred with a mixture of intramembranous and enchondral ossification, indicating that the rigid fixator was not sufficiently stiff to provoke exclusively direct ossification. Furthermore, a maximum flexible condition with the bone fragments probably coming into contact during the initial postoperative phase did not induce a nonunion, confirming the hypothesis of Gröngröft et al…”

A Comparative Evaluation of Fixation Techniques in Anterior Mandibular Fractures Using 2.0 mm Monocortical Titanium Miniplates Versus 2.4 mm Cortical Titanium Lag Screws

“…Likewise Charnley [21] stated that osteogenesis is actually stimulated by compression of the fragments. It is generally accepted that reduction and fixation of the fracture to align the fragments in contact, promotes bone healing [22]. A direct correlation between the fracture gap width and the healing process is given in the literature; Large fracture gaps more than 2 mm cause a delay in fracture healing, due to large amount of cartilage and external callus formation between the fracture fragments as demonstrated in Graph 3 Post-operative evaluation (Biting Efficiency) experimental [23], and clinical investigations [24].…”

Intact fibula improves fracture healing in a rat tibia osteotomy model

“…The mechanical environment can be characterized by the fracture gap size and by the interfragmentary movement. Several studies have demonstrated that an increasing gap site results in a delay of healing [4,10]. Also excessive motion at the fracture size induces callus formation but retards the consolidation process of the callus [5,20,27].…”