Development of an atrophic nonunion model and comparison to a closed healing fracture in rat femur

Abstract

Although most fractures heal, some fail to heal and become nonunions. Many animal models have been developed to study problems of fracture healing. The majority of nonunion models have involved segmental bone defects, but this may not adequately represent the biologic condition in which nonunions clinically develop. The objective of the present study is to develop a nonunion model that better simulates the clinical situation in which there is soft tissue damage including periosteal disruption and to compare this model to a standard closed fracture model utilizing identical fracture stabilization, providing a similar mechanical environment. A total of 96 three month old Long Evans rats were utilized. A 1.25 mm diameter K-wire was inserted into the femur in a retrograde fashion, and a mid-diaphyseal closed transverse fracture was created using a standard three-point bending device. To create a nonunion, 48 of the rats received additional surgery to the fractured femur. The fracture site was exposed and 2 mm of the periosteum was cauterized on each side of the fracture. Fracture healing was evaluated with serial radiographs every two weeks. Animals were maintained for intervals of two, four, six or eight weeks after surgery. Specimens from each time interval were subjected to bioniechanical and histological evaluation. None of the cauterized fractures healed throughout the eight weeks experimental duration. The radiographical appearance of nonunion models was atrophic. This investigation showed pronounced differences between the experimental nonunions and standard closed fractures both histologically and biomechanically. In conclusion, we have developed a reproducible atrophic nonunion model in the rat femur that simulates the clinical condition in which there is periosteal disruption but no bone defect.

Osteogenic Protein-1 Overcomes Inhibition of Fracture Healing in the Diabetic Rat: A Pilot Study

“…The percentage increase in area of reparative callus with OP-1, compared with treatment groups without OP-1, did not necessarily translate into an equivalent percentage increase in torque to failure. Although our choices of the 25-lg dose of OP-1 and 4-week point initially seemed justified by the literature [4,15,18,21], our torsion failure testing results indicated the diabetic challenge in this model may have required a higher dose of OP-1 and longer followup to observe a difference in failure parameters. A time greater than 4 weeks may have allowed the callus to further remodel and become stronger.…”

“…Six rats from each of the four treatment groups were euthanized 2 and 4 weeks after creation of the closed fracture using inhalant anesthesia (glass-covered tank with a sponge soaked with 1 mL of halothane) and an overdose of euthanasia solution (intraperitoneal administration of 100 mg/kg Beuthanasia-D [Schering-Plough Animal Health Corp, Kenilworth, NJ]). The 2-and 4-week times were chosen because extracellular matrix proteins are maximally expressed in the hard callus by 15 days and maximum torque to failure peaks at 4 weeks and remained at the same level to 8 weeks [18,21]. The fractured femurs from these animals were harvested and fixed in 10% formalin (Fischer Scientific, Pittsburgh, PA), a formaldehyde/ methanol solution buffered with phosphate-buffered saline.…”

Local transplantation of human multipotent adipose-derived stem cells accelerates fracture healing via enhanced osteogenesis and angiogenesis

“…Non-healing femoral fractures were induced in all animals by cauterizing periosteum around the fracture site with a modification of the original method 24 as described previously. 25,26 Immediately after fracture induction, rats received local transplantation of hMADS cells (1 Â 10 5 ) or hFB (1 Â 10 5 ) suspended in 100 ml of PBS with atelocollagen gel (KOKEN, Tokyo, Japan), which is bovinederived bioscaffold (hMADS group, n ¼ 20; hFB group, n ¼ 20). The same amount of PBS with atelocollagen gel (PBS group, n ¼ 20) and the contra-lateral side with an unfractured femur were used as controls for histological and functional analyses, respectively.…”

Characterization of pseudarthrosis with ultrasound backscattered signals in rats

“…Many methods have been used in the treatment of pseudarthrosis, such as: osteoperiostal decortication, spongy autograph, BMP (bone morphogenetic protein), stem cell from bone marrow, platelet growth factors, vascularized bone graft, internal stabilization with different materials (compression plate, locked, unreamed intramedullary nail), external stabilizers (external fixators or orthoses), besides ultrasound, shock waves and electromagnetic fields 14,15 . This wide range of options just reflects the absence of a consensus about the best approach for this disease; which may bring about serious conditions like disabilities and deformities with great social and economical burden for the families and the public health services.…”

“…Several animal species have been used to create a pseudarthrosis 14,[17][18][19][20] , but the authors usually converge their attention to the relevance of vascularization or to the extension of the bone segment injured.…”