Control Femurs Research Articles

Derby intramedullary nail — A biomechanical comparison

This paper describes the design and function of the Derby intramedullary nail and its biomechanical testing, comparing it with the k nail and reamed unfractured femurs. The Derby nail is designed to transmit torsional loads and apply compression to the fracture site using a sliding proximal collar and distal extendable ‘wings’. Femurs fixed with Derby, K and Zickel nails and AO plates were tested in torsion and the rotation and torsional load at failure recorded and compared with unfractured control femurs. The results show that the strength of the Derby nail in torsion is ≈4 times and the energy to failure 2.3 times that of the k nail.

Pathologic Effects of Vaccinia Virus on Rabbit Bone and Marrow

Although viruses have recently been implicated in the pathogenesis of Paget's disease and Perthes' disease, little information is available regarding bone and marrow response to the presence of a noncarcinogenic virus. Vaccinia virus was introduced into the medullary cavity of the femoral shaft of 30 New Zealand White rabbits, and an appropriate control inoculation was performed. Virus was recovered from the inoculation site in 50% of the animals at intervals to one month after inoculation. Histologic abnormalities were observed in 69% of the test femora; similar abnormalities were not observed in the control femora. These abnormalities consisted of bone and marrow necrosis, lymphocyte and plasma cell infiltration, and new bone formation. Some of the newly formed bone was also necrotic. The latter observation suggests an alternative mechanism for the death of new bone, which, in Perthes' disease, has customarily been attributed to repeated ischemic insults.

The Effects of Cerclage Wiring on the Immature Canine Diaphysis A Biomechanical Analysis

When cerclage wiring is used in skeletally immature dogs, the wires become imbedded in the cortical bone due to radial appositional bone growth.Six groups of five dogs each received one or two extraperiosteal cerclage wires at the mid‐diaphysis of the left femur at the age of five months. Ten dogs were killed immediately, ten dogs were killed at eight weeks postoperatively, and ten at twelve weeks. Both femora from each animal were collected and subjected to torsional loading to failure within.5 seconds. The maximum torque, shear stress, energy absorption, angular deformation, and torsional stiffness were determined and subjected to í test analysis.Application of the wires predictably caused an increase in weight and cortical bone thickening at the implant site, which was primarily due to endosteal bone deposition in the 8‐and 12‐week groups. The 8‐and 12‐week wired bones were stiffer and failed at a lower angular deformation than did their corresponding control femurs, but the zero‐time bones did not show this tendency. Significantly less shear stress accumulation and energy absorption at failure were present In the 8‐and 12‐week implants, but no difference was seen in the zero‐time femora. The 8‐week groups showed a greater difference between the wired and control femurs than did the 12‐week groups. No significant difference was found between one‐and two‐wire implants in the study.The results indicate that confinement of dogs with clinically wired fractures of immature canine femurs should extend past eight weeks.

Absence of response of chick embryonic limb to the growth stimulatory effect of parathyroid hormone in vitro after exposure to 6-aminonicotinamide in ovo.

The biochemical effect of a nicotinamide analogue, 6-aminonicotinamide (6-AN), on developing chick embryonic femur was studied. Growth of femur from 9-day-old embryos that had been exposed to 6-AN for 5 days in ovo was not stimulated by PTH in an in vitro culture system. PTH caused a much smaller increase in the cyclic-AMP content in 6-AN-treated femur than in control femur. However, dibutyryl cyclic-AMP stimulated growth of 6-AN-treated femur. A defect in response of 6-AN-treated femur to the growth stimulating action of PTH may explain the production of micromelia by 6-AN.

The marrow fat cell: Response to X-ray induced aplasia

Adipose tissue is an integral structural component of normal rabbit marrow and is believed to behave primarily as a cushion in response to hemopoietic proliferation, accomodating to changes in hemopoiesis by change in either size or number or both of the fat cells in order to maintain constancy of the marrow volume. To test this hypothesis, aplasia of the right femur of New Zealand white rabbits was induced by x-irradiation with 8000 rads; the left unirradiated limb served as control. Twenty-four hours before sacrifice 50 μCi of palmitate-114C was administered intravenously and the marrow of both femurs removed. Samples of perinephric fat were taken for comparison. Fat cell volume, C14 palmitate turnover and fatty acid composition were determined. The total number of fat cells in the entire marrow of both femurs was calculated. The measurements showed no difference in size or fatty acid turnover of the fat cells in the irradiated aplastic marrow from the cells of the control marrow. The number of fat cells in both the irradiated and the unirradiated control femurs was essentially the same. These findings do not support the view that marrow fat cells respond to diminished hematopoiesis by either increase in their volume or number. In addition, the findings suggest that both marrow and subcutaneous fat cells are fairly resistant to high doses of x-ray irradiation.

Cellular Response to Fracture Studied with Tritiated Thymidine

An autoradiographic study of femoral-fracture repair using tritiated thymidine was made on forty-two female mice, five weeks of age. Assessment of the periosteal labeling index was obtained from one hour to fourteen days after fracture. Results showed that the initial proliferative response is seen in the periosteum and adjacent soft tissues sixteen hours after fracture. No increase in proliferation was observed at eight hours. The reaction was not limited to the fracture site but extended along the entire femoral diaphysis. The maximum increase of the labeled periosteal population (25.4 per cent) was observed at thirty-two hours after fracture. After thirty-two hours, the size of the labeled population decreased with increasing time. The decrease was more apparent away from the fracture site, so that within five days of fracture the proliferative potential was similar to that of the non-fractured control femur. Fourteen days after fracture, the labeled population of periosteal cells at the fracture site was still above the value of the controls. The course of fracture repair was followed autoradiographically.