Victor H. Frankel

The elastic modulus for bone

Abstract The elastic moduli for human and bovine bone specimens were determined by compression and tension tests and compared. No statistically significant difference was found between the moduli determined in the two loading modes.

The ultimate properties of bone tissue: the effects of yielding.

Abstract An elastic perfectly plastic mathematical model for the behavior of bone tissue is presented in an attempt to reconcile previous discrepancies in the literature in the calculated ultimate tensile strength from bending and tensile tests. Specimens of round and square crosssections were tested in bending to demonstrate the effect of cross-sectional shape on initiation of plastic flow and consequent increase in moment carrying capacity. Tensile tests on specimens with circular cross-section were made to show that the bone tissue can indeed demonstrate considerable plastic deformation.

The Biomechanics of Torsional Fractures: The Stress Concentration Effect Of A Drill Hole

To determine the effect of a drill hole on the strength of long bones and on the fracture resulting from rapidly applied torsional loads, paired canine femora were tested, and the following results were obtained:nn1. The presence of a 2.8-millimeter or a 3.6-millimeter drill hole in the femoral mid-shaft significantly weakens the bone as measured by a mean reduction in energy-absorbing capacity of 55.2 per cent.nn2. The drill hole produces a significant increase in local stresses as demonstrated by a calculated stress concentration factor of 1.6.nn3. Changes in the ratio of drill hole area to bone area from .12 to .28 are not accompanied by significant changes in the bone strength or in the stress concentration factor.nn4. The resulting spiral fractures occur along planes of maximum tensile stress, and the drill hole does not alter their orientation.nn5. In drilled specimens the fracture is localized to the region of the drill hole and is less comminuted.

Biomechanics of Internal Derangement of the Knee: Pathomechanics As Determined By Analysis Of The Instant Centers Of Motion

The kinematic technique of instant center analysis of the knee is described. Determination of the instant center or centrode permits identification of the type of motion of the joint surfaces.Twenty-five normal knees were studied and the centrodes were located for the range of motion between full ex

The biomechanics of torsional fractures: The effect of loading on ultimate properties

Abstract Mechanical properties of bone tissue have been studied to determine the viscoelastic behavioral characteristics. Whole bones, however, have not been examined to determine the effect of loading rate on ultimate properties. This paper presents results obtained from torsional tests of fresh dog tibiae and femora tested at both high and low loading rates. The data which is presented includes energy absorption required for failure, maximum torque, and maximum angular deformation before failure. A comparison of these properties is made between paired specimens tested at high rates of loading and at low rates of loading. The findings indicate increased energy absorption, increased maximum torque, and slightly increased angular deformation under rapid loads. In addition there is a strong suggestion of a different fracture pattern.

THE VISCOELASTIC PROPERTIES OF SOME BIOLOGICAL MATERIALS

Implant devices, as a general rule, are used to replace the mechanical function of defective biological material. It is therefore of significant interest to know the mechanical properties of biological tissue. These properties have been studied in many of the classical ways proposed by the concepts of linear elastic materials. Such properties as modulus of elasticity and poisons ratio have been the object of these studies. The findings of these investigations warrant careful scrutiny, in the line of current findings. It should be realized that the properties of elastic modulus and poisons ratio are experimentally derived quantities, and are descriptive of elastic behavior only when based upon the assumption of linear response. They are not sufficiently descriptive when the properties of the material are time dependent. Many biological tissues have been shown to possess time-dependent properties. Therefore it is desirable to shift the emphasis in experimentation from a linear approach to a nonlinear approach. The importance of including time as an independent parameter can be seen in the following example. Consider the time-deformation curve as is obtained from the Hookean model. This behavior is significantly different from the behavior of biological tissue (FIGURE 1 ) . If cartilage is loaded in compression and the load is allowed to remain constant, the characteristic behavior is as shown in FIGURE 2. The figure is actually a composite of several tests, each of increased loading duration. It will be noted that the percentage of recovery decreases with increasing time duration. A similar test using bone under tension produces similar results (FIGURE 3 ) . In this case the loading intensity was increased from 10 kg in Graph A to 20 kg in Graph B to 30 kg in Graph C. Again a decrease in recovery is noted with increasing load. A viscoelastic model may be constructed which will display the deflection-time characteristics for that phase of loading which producesfull recoil (FIGURE 4). This is the simplest model which will display the characteristic delayed deformation and recoil (FIGURE 5). The load-deflection characteristics of this model are dependent upon both loading method and loading rate. If a constant strain-rate method of loading is chosen, where r is the deflection rate, then the following load deflection curves will result (FIGURE 6). The initial slope of all curves is given by k, and the asymptotic value is given by k, k, /(kl + k,) . These curves can be compared with the results obtained by McElhaney and Byars for loaddeflection curves of cortical bone (FIGURE 7) . It is seen that there exists a basic agreement between the model and the test results. The test curves however, do not exhibit the parallel asymptotic behavior of the the theoritical curves.This may be due to the onset of failure before sufficient deformation occurs. While this rheological model seems to fit the basic characteristics necessary for the description of bone tissue behavior within the limits of total elastic recoil, if we wish to describe the behavior of tissue which has suffered permanent deformation, then we must increase the complexity of the model. Such a model was proposed by Sedlin (FIGURE 8 ) . The deformation and characteristics of this

SURGICAL TREATMENT OF CHRONIC DISLOCATION OF THE STERNO-CLAVICULAR JOINT

The costo-clavicular ligament is always ruptured in dislocation at the sterno-clavicular joint. Anterior, superior or posterior displacement of the medial end of the clavicle may occur. Acute dislocation usually responds to conservative treatment and operation is seldom required. Chronic, or recurrent, dislocation may cause pain and disability on strenuous activity and necessitate surgical treatment. The operation of tenodesis of the subclavius tendon with capsulorrhaphy described by Burrows (1951) has been adopted. The intraarticular meniscus is often damaged and displaced, and may block reduction; its removal is then necessary. In addition, a threaded Stinmann pin transfixing the joint has been found useful to maintain the stability of reduction. The operation has been performed on five patients, four of whom had excellent results. The fifth patient disrupted the repair in a drinking bout shortly after the operation.

LOAD CAPACITY OF TUBULAR BONE

Publisher Summary This chapter discusses the load capacity of tubular bone. Long tubular bones act as structural machine members; as such, they carry applied loads and participate in kinematic function. The chapter presents an investigation concerned with the ability of long bones to resist these loads. In fulfilling this function, the bones must resist both static or slowly applied loads and dynamic loads. It was noted that the amount of torsional load necessary to produce a fracture of a fresh human tibia was 768 kgcm. From examination of published data and application of engineering fundamentals, it is evident that the distribution of bony tissue represents an economic compromise. This condition must exist because of to the variety of loads to which the bone is subjected. Hollow circular sections of constant dimension are best suited to carry torsional loads. Representative bones were sectioned at the point of initial failure. The contiguous surfaces were photographed. The section properties were obtained by means of graphical integration. The torsional moments of inertia and section moduli and the bending moments of inertia and section moduli were calculated. Removal of cortical bone converts a portion of the bone from the closed section to the open section state. This markedly reduces its torsional load-bearing capacity and its torsional energy absorbing capacity. While not significantly reducing the torsional stiffness of the whole bone, it does greatly reduce the maximum allowable angular deflection.

Failure Characteristics of Bone and Bone Tissue

The failure characteristics of the structural elements of the human body have interested men for centuries. During the last several decades the question ‘how strong?’ has been asked and answered repeatedly. As in other areas of mechanics the answers to the questions have varied, depending both upon the technique that the observer has used and the astuteness of the observer.

Bicycle spoke injuries of the foot and ankle in children: An underestimated “minor” injury☆

Abstract Bicycle spoke injuries to the lower extremeties, especially the malleoli, of children present a significant problem in management because of the minor appearance of the initial injury. Treatment is frequently casual because the extent of the injury is not recognized and its potential harm not appreciated. Injury usually results from the sudden, forceful trapping of the foot between the spokes and frame of a bicycle. It is probably a common injury, since more than 150,000 pedal bicycle injuries occur in the United States of America each year. 1 Our experience in the past 4 years with 60 cases under 14 years of age prompts us to call attention to this entity as injury that requires special consideration.