Bone remodeling in response to in vivo fatigue microdamage

Response of joints to impact loading, III: relationship between trabecular microfractures and cartilage degeneration

Uniaxial fatigue tests were conducted of devitalized cortical bone specimens machined from human femora. Specimens were tested at strain ranges from 0.005 to 0.010 under physiologic loading rates. The influence of compressive, zero, and tensile mean strains on fatigue life and on the stress/strain histories during fatigue were examined. Results showed that bone fatigue is a gradual damage process accompanied by a progressive increase in hysteresis and a loss of bone stiffness. The total number of cycles to fatigue failure was influenced only by the total strain range and was not affected by mean strain. Bone was shown to have extremely poor fatigue resistance. Fully reversed cyclic loading to one half of the yield strain caused fatigue fracture in 1000 cycles. Biological implications. The bone regions which experience the highest strain ranges in vivo generally have a compressive mean strain. The results of this study indicate that mechanical fatigue damage accumulates more rapidly in these "compressive" areas than in "tensile" areas of bone.

https://www.tandfonline.com/doi/pdf/10.3109/17453678108992136

Fatigue behavior of adult cortical bone: the influence of mean strain and strain range.

Mechanical and morphological effects of strain rate on fatigue of compact bone.

Mechanical properties of articular cartilage.

Rotating cantileverfatigue tests were performed on specimens extracted longitudinally from the cortices of human femora. The usual inverse relationship between stress amplitude and fatigue life was found; the median life was 1·3×104 cycles at a stress amplitude of 12,200 1bf/in2 (84·1 MN/m2) and 4·6×106 cycles at 6750 1bf/in2 (46·6 MN/m2). Arguments are advanced which suggest that these results are compatible with what is known of the stresses applied in life and the clinical occurrence of fatigue fractures.

The fatigue properties of human cortical bone

The hypothesis that bone, either tubular or trabecular, is hydraulically strengthened is examined. (1) Tubular bone. On the basis of information available in the literature, it is concluded that tubular bone is not hydraulically strengthened. (2) Trabecular bone. On the basis of an experimental study reported in this paper, it is concluded also that trabecular bone is not hydraulically strengthened.

Is bone hydraulically strengthened

A prosthetic knee joint device of ''hingeless'' form having femoral and tibial components held in mutual sliding and rolling bearing engagement by natural muscle and ligaments. The femoral component includes a generally U-shaped channel member having an outer surface with a generally convex curvature in the circumferential sense relative to the channel longitudinal axial direction, and a smooth form with a single curvature in the axial sense. This single curvature need not necessarily be convex. The tibial component includes a platform member having one of its major surfaces concavely dished in generally complementary manner to at least the convex curvature of the femoral component. The inner surface and the other major surface of channel and platform members are adapted for fixation with cement to the femur and tibia.

Knee joint prosthesis

A FULL description of load carriage or lubrication in synovial joints requires among other things a knowledge of local pressures between the articular surfaces. Average pressures are easily calculated for joints at which the loads and the contact areas are known. Pressure transducers for use in a prosthetic femoral head are being developed (Carlson et al. 1974), and a method for finding the loads transmitted through up to four regions of acetabular cartilage by successively removing the regions (Day etaL, 1975) has produced some information about pressure distributions in the cadaveric hip joint subjected to physiological loads. This note describes briefly a pressure transducer which has been used to measure the presssures at eleven positions on the bonecartilage junction in cadaveric hips. The results obtained will be described fully elsewhere, particularly with reference to the variations of pressures through a typical walking cycle; the purpose of this note is to show that a technique exists which can give useful results.

Direct measurement of local pressures in the cadaveric human hip joint.

(1)

The strains occurring in the subchondral bone of the cadaver human femoral head were measured when the head was subjected to a load of physiological magnitude and direction.




(2)

The strains were tensile around the circumference of the femoral head and compressive in the plane of the applied load.




(3)

In the intact femoral head the magnitude of the strains was such that fatigue fracture of the subchondral bone would not be expected to occur in life.




(4)

When a cylindrical defect 13 mm in length and 10 mm in diameter was made in the centre of the femoral head, the measured strains in the subchondral bone invariably rose, and in some femoral heads the calculated stresses were high enough to be likely to cause fatigue fracture.




(5)

It is concluded that cysts developing in the femoral head in osteoarthrosis may usually result in a rise in the stresses in the subchondral bone, with a possible consequent revascularization of the overlying cartilage either via a fatigue crack or by reason of the vascular changes accompanying the healing of an incipient fatigue crack. The probability of either of these events cannot be assessed accurately with the information available, but it appears to be low.

S. A. V. Swanson

Papers

The fatigue properties of human cortical bone

Is bone hydraulically strengthened

Knee joint prosthesis

Direct measurement of local pressures in the cadaveric human hip joint.

Fatigue fracture in the subchondral bone of the human cadaver femoral head