Metaphyseal fracture healing follows similar biomechanical rules as diaphyseal healing

Abstract

ABSTRACT:It is generally supposed that the pattern of fracture healing in trabecular metaphyseal bone differs from that of diaphyseal fractures. However, few experimental studies to date have been performed, even though clinically many fractures occur in metaphyseal bone. Particularly, the influence of biomechanical factors has not yet been investigated under standardized conditions. Our aim was to correlate the interfragmentary strain (IFS) with the bone-healing outcome in a controlled metaphyseal fracture model in sheep. Twelve sheep received a partial osteotomy in the distal femoral condyle close to the trochlea. The determination of the IFS by in vivo X-ray analyses and a finite element model revealed that the deflection of the osteotomy gap by the patello-femoral force during walking provoked increasing strains of up to 40%. Bone healing was evaluated after 8 weeks by the assessment of the bone mineral density and by histomorphometry in regions of interest that displayed differing magnitudes of IFS. In areas with strains below 5% significantly less bone formation occurred compared to areas with higher strains (6-20%). For strains larger than 20% fibrocartilage layers were observed. Low IFS (<5%) led to intramembranous bone formation, whereas higher strains additionally provoked endochondral ossification or fibrocartilage formation. It is therefore proposed that metaphyseal bone healing follows similar biomechanical principles as diaphyseal healing.

Internal fixation of fragility fracturesof the femoral neck

“…Nonunions remain a considerable complication following femoral neck fracture treatment (Parker et al 2007). From animal experiments we know that magnitude of interfragmentary motion is important for the course of fracture healing (Perren 2002, Augat et al 2005, Claes et al 2011. Our experiment revealed that micromotions about the femoral neck (z-axis) were significantly reduced in the locking plate group, representing an improved resistance to shear forces.…”

“…The epiphyseal plate itself is considered part of the metaphysis which follows the same principles of fracture healing as diaphyseal bone (Claes et al 2011). Fracture healing is a complex process dependent on numerous local and systemic factors and only a brief description will be given in this thesis.…”

Metaphyseal Fracture Healing

“…Cartilage formation might be related to low oxygen tension. Instability, or rather micromotion, will induce cartilage formation in both cancellous and cortical healing [17][18][19][20][21][22][23][24]. However, cancellous fractures are generally stable in the sense that repeated cyclic deformation of a considerable magnitude is unlikely to occur.…”

“…A slight cyclic deformation has been showed to be beneficial for optimal bone formation in traumatized cancellous bone both in humans and animals [17,25,26].…”

Special Review: Accelerating fracture repair in humans: a reading of old experiments and recent clinical trials

“…There is a myriad of papers on the biology of shaft fracture healing, but only a very sparse literature on the biology of cancellous bone fractures. 6 This might be due to the paucity of animal models for cancellous bone healing, especially for mechanical evaluation.…”