Wolff’s law

Research based on Wolff s law of bone transformation has resulted in some other important observations. Fluctuating loads, such as those that occur in walking, are better for bone than consistentiy appUed loads, such as weight gain. However, if the effective appUed load becomes extreme, pressure necrosis, ie, bone death, occurs. Pressure necrosis is a significant concern in hip arthroplasty. Necrosis means the localized death of living tissue. Undue pressure on living cells causes death. Some total hip replacement failures are the direct result of pressure necrosis. 

Wolff s Law Bone develops or adapts its structure to that most suited to resist the forces acting upon it. 

Kaplan, D. G., "Bone Response to Mechanical Forces, (A Proposed Explanation for Wolff s Law)", presented at the 198th American Chemical Society Meeting, Miami Beach, Florida, Sept. 1989. 

Thus the amount of the stress reduction in bone when an implant is included depends on the modulus and cross-sectional area of the implant. Implants with a higher modulus and a larger cross-sectional area will shield the bone from a greater proportion of its normal physiological stress, resulting in bone loss according to Wolff s law. 

As the growth plate is subjected to forces, the sacrum will deform. It will round off and dome and L5 will become trapezoidal because of Heuter Volkman and Wolff s laws. The pars interarticularis will become elongated through repeated stress fractures [7]. If the posterior tether is weak L5 slips off. We can understand the entire event of spondylolisthesis from birth to spondyloptosis with this thinking. We can also understand the various spinal pathoanatomies that are seen at various times with x-rays. 

It is clear that severe spondylolisthesis is seen in growing children. The developmental type of spondylolisthesis with high dysplasia is the problem (a poor bony hook). For whatever reason the pelvis rotates and lordosis increases. This now causes stress on the growth of the plates of L5 and SI. These deform because of Heuter Volkman Rule and Wolff s law. The dys-plastic bony hook may stretch or separate or both. The sacrum may bend. The disc may fail. Eventually in the worst case scenario the spondylolisth-... 

HC1 is efficiently absorbed into H2S04-H20 and into HN03-H2S04-H20 solutions, which as discussed earlier, are found in the stratosphere in the form of aerosol particles and Type I PSCs under some conditions (Wolff and Mulvaney, 1991). The solubility of HC1 in these liquid solutions can be expressed in terms of the usual Henry s law constant (Elrod et al., 1995 Abbatt, 1995 Luo et al., 1995 Hanson, 1998). Table 12.4 shows some typical measurements of the Henry s law constants for HC1 in several typical binary and ternary solutions, respectively. Hanson (1998) has shown that the solubility data for HC1 in binary mixtures of H2S04 and water in these and other studies can be fit by the form... 

Brunner, S., Hornung, E., Santl, H., Wolff, E., Piringer, O.G., Altschuh, J., and Bruggemann, R. 1990. Henry s law constants for polychlorinated biphenyls Experimental determination and structure-property relationships. Environ. Sci. Technol. 24, 1751-1754. 

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