Effects of intramedullary reaming and nailing of rat femur. A mechanical and chemical study

Oral administration of bovine lactoferrin accelerates the healing of fracture in ovariectomized rats

INTRODUCTION

Lactoferrin has recently been reported for its potent bone growth effects. However, the effects of lactoferrin on the healing process of fragility fracture have not yet been studied, so the purpose of this study is to investigate whether oral administration of lactoferrin can promote the fracture healing in an OVX animal model.

MATERIALS AND METHODS

Three months after bilateral ovariectomy, all rats underwent unilateral tibial osteotomy and were then randomly divided into control group and bovine lactoferrin (bLF) group. At 4 and 8 weeks post-fracture, animals were sacrificed, and the fractured tibiae and serum samples were collected for evaluation.

RESULTS

Our results showed that bLF treatment not only accelerated the bone growth at an early stage of OPF healing but also shortened the remolding process of OPF healing. When compared to control group, bLF treatment induced a significant rise in callus BMD (by 35.0% at 4 weeks and by 39.7% at 8 weeks; both p < 0.05) consistent with enhanced biomechanical strength of the callus, with ultimate force increased by 3.39-fold at 4 weeks (p < 0.05) and 1.95-fold at 8 weeks (p < 0.05). Besides, bLF administration resulted in a substantial increase in serum levels of BALP and a significant decrease in serum levels of TRAP 5b and TNF-α. Moreover, both the RANKL/OPG mRNA ratio and the expression of TNF-α in the callus of bLF-treated group were markedly lower than those in the control group.

CONCLUSIONS

At a dose of 85mg/kg/day orally administrated bLF potently promoted the bone healing following tibial fracture in OVX rats.

[Effect of intramedullary reaming and nailing on the production of growth factors in the femur fracture callus in rats]

INTRODUCTION

Many studies have been conducted to determine the different effects that reaming or intramedullary nailing have on fracture healing, but there is no evidence in the literature of the effect of intramedullary reaming on osteogenesis. We performed a prospective study to analyse the effect of intramedullary reaming and nailing on the production of growth factors during the process of fracture healing in the femur of rats.

MATERIAL AND METHODS

A transverse mid-shaft non-comminuted femur fracture was produced in 64 rats; 34 rats did not receive any treatment, and a standardized surgical procedure was performed on 30 rats, by exposing the left knee, reaming the medullary canal from distal to proximal, and then fixing the fracture with a steel pin. The rats were sacrificed at the 24th hour, 4th, 7th and 15th days after the fracture. The amount of growth factors that appeared in the callus fracture was measured using histopathology studies. The primary categorical variables analysed were PDGFA, TGF2 and TGFβ-R2. These variables were analysed in each group at the different sacrifice times.

RESULTS

The results of the primary variables of the study, stratified by the time until sacrifice, showed no statistically significant differences.

DISCUSSION

Even if the presence of an intramedullary wire facilitates the fracture repair and the stabilising the bridge of bone between both edges of the fracture site, no evidence was found that reaming changes the expression of the growth factors studied (PDGFA, TGFβ-R2 and TGFβ2) during the callus formation in rats.

Bone modeling controlled by a nickel-titanium shape memory alloy intramedullary nail

Nitinol (NiTi) shape memory metal alloy makes it possible to prepare functional implants that apply a continuous bending force to the bone. The purpose of this study was to find out if bone modeling can be controlled with a functional intramedullary NiTi nail. Pre-shaped intramedullary NiTi nails (length 26 mm, thickness 1.0-1.4 mm) with a curvature radius of 25-37 mm were implanted in the cooled martensite form in the medullary cavity of the right femur in eight rats, where they restored their austenite form, causing a bending force. After 12 weeks, the operated femurs were compared with their non-operated contralateral counterpairs. Anteroposterior radiographs demonstrated significant bowing, as indicated by the angle between the distal articular surface and the long axis of the femur (p = 0.003). Significant retardation of longitudinal growth and thickening of operated femurs were also seen. Quantitative densitometry showed a significant increase in the average cross-sectional cortical area (p = 0.001) and cortical thickness (p = 0.002), which were most obvious in the mid-diaphyseal area. Cortical bone mineral density increased in the proximal part of the bone and decreased in the distal part. Polarized light microscopy of the histological samples revealed that the new bone induced by the functional intramedullary nail was mainly woven bone. In conclusion, this study showed that bone modeling can be controlled with a functional intramedullary nail made of nickel-titanium shape memory alloy.

Nailing and occlusion of the medullary cavity. Flow and mechanical changes in rat femora

25 rats were bilaterally operated on and the femoral canal nailed, nailed and plugged with silicone or only plugged with silicone after intramedullary nailing. A fourth group was intramedullary reamed without any other intervention. The bones were evaluated after 12 weeks, including flow measurements, mechanical properties and bone dimensions. There were no differences between the groups in total bone or cortical bone blood flow. There were only marginal changes in outer and inner anteroposterior diameters and the area moment of inertia. The maximum bending stress in bones that had been both nailed and silicone-plugged was decreased compared to the other groups, except the nailed bones. In the silicone/nail group, energy absorption was less than in the other groups, except the nailed group. We conclude that modest intramedullary reaming, nailing or plugging of the femoral canal do not change the mechanical properties of the bone, nor do they induce chronic vascular changes in bone. However, when the medullary cavity is filled with both a nail and silicone, mechanical as well as structural changes may ensue.

Effects of graded reaming on fracture healing. Blood flow and healing studied in rat femurs

In 30 rats, closed bilateral fractures of the femur were produced. On the left side intramedullary reaming was performed to 1.6 mm, and the fracture fixed-with a steel pin with a diameter of 1.6 mm. On the right side the femoral canal was reamed to 2.0 mm and a hollow steel tube with a diameter of 2.0 mm was used for fixation. An additional 8 rats were used to obtain mechanical, dimensional and flow data on intact femurs, and another 10 rats were used to study the acute flow changes caused by fracture and different degrees of reaming and fracture. Fracture and reaming reduced total bone and cortical bone blood flows to about one third of normal flow, with no differences between the 1.6-mm and the 2.0-mm reamed bones. At 4 weeks, total bone flow was about double and cortical bone flow about 4 times increased in the 1.6-mm group. In the 2.0-mm reamed bones increases of approximately 5 times in total bone flow and of about 7 times in cortical flow were found. Callus flow was about twice the size of the respective cortical flow in both groups. Both total and cortical flows gradually subsided, without differences between the 2 groups. At 12 weeks, the callus area in the 2.0-mm group was greater than in the 1.6-mm group, while bone dimensions were greater in the 2.0-mm group at 4 and 12 weeks. Bending moment and rigidity were greater in the 1.6-mm group than in the 2.0-mm one at every time interval; no differences were found in fracture energy.(ABSTRACT TRUNCATED AT 250 WORDS)