Davis's law is used in anatomy and physiology to describe how

soft tissue Soft tissue is all the tissue in the body that is not hardened by the processes of ossification or calcification such as bones and teeth. Soft tissue connects, surrounds or supports internal organs and bones, and includes muscle, tendons, ligam ...

models along imposed demands. It is the

corollary In mathematics and logic, a corollary ( , ) is a theorem of less importance which can be readily deduced from a previous, more notable statement. A corollary could, for instance, be a proposition which is incidentally proved while proving another ...

Wolff's law Wolff's law, developed by the German anatomist and surgeon Julius Wolff (surgeon), Julius Wolff (1836–1902) in the 19th century, states that bone in a healthy animal will adapt to the loads under which it is placed. If loading on a particular ...

, which applies to

osseous tissue A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, an ...

. It is a physiological principle stating that soft tissue heal according to the manner in which they are mechanically stressed. It is also an application of the

Mechanostat The Mechanostat is a term describing the way in which mechanical loading influences bone structure by changing the mass (amount of bone) and architecture (its arrangement) to provide a structure that resists habitual loads with an economical amount ...

model of

Harold Frost Harold M. Frost (1921 – 19 June 2004) was an American orthopedist and surgeon considered to be one of the most important researchers and theorists in the field of bone biology and bone medicine of his time.Turner C, Burr D, Jee WS, Smith S, Re ...

which was originally developed to describe the adaptational response of bones; however – as outlined by Harold Frost himself – it also applies to fibrous collagenous connective tissues, such as ligaments, tendons and fascia.Frost, Harold "The physiology of cartilagenous, fibrous, and bony tissue. C.C. Thomas, 1972 The "stretch-hypertrophy rule" of that model states: "Intermittent stretch causes collagenous tissues to hypertrophy until the resulting increase in strength reduces elongation in tension to some minimum level". Similar to the behavior of bony tissues this adaptational response occurs only if the mechanical strain exceeds a certain threshold value. Harold Frost proposed that for dense collagenous connective tissues the related threshold values are around 23 Newton/mm2 or 4% strain elongation.

Origin

The term ''Davis's law'' is named after Henry Gassett Davis, an American orthopedic surgeon known for his work in developing traction methods. Its earliest known appearance is in John Joseph Nutt's 1913 book ''Diseases and Deformities of the Foot'', where Nutt outlines the law by quoting a passage from Davis's 1867 book, ''Conservative Surgery'': :"Ligaments, or any soft tissue, when put under even a moderate degree of tension, if that tension is unremitting, will elongate by the addition of new material; on the contrary, when ligaments, or rather soft tissues, remain uninterruptedly in a loose or lax state, they will gradually shorten, as the effete material is removed, until they come to maintain the same relation to the bony structures with which they are united that they did before their shortening. Nature never wastes her time and material in maintaining a muscle or ligament at its original length when the distance between their points of origin and insertion is for any considerable time, without interruption, shortened." Davis's writing on the subject exposes a long chain of competing theories on the subject of soft tissue

contracture In pathology, a contracture is a permanent shortening of a muscle or joint. It is usually in response to prolonged hypertonic spasticity in a concentrated muscle area, such as is seen in the tightest muscles of people with conditions like spasti ...

and the causes of

scoliosis Scoliosis is a condition in which a person's spine has a sideways curve. The curve is usually "S"- or "C"-shaped over three dimensions. In some, the degree of curve is stable, while in others, it increases over time. Mild scoliosis does not t ...

. Davis's comments in ''Conservative Surgery'' were in the form of a sharp rebuke of lectures published by Louis Bauer of the Brooklyn Medical and Surgical Institute in 1862. In his writing, Bauer claimed that "a contraction of ligaments is a physiological impossibility". Bauer sided with work published in 1851 by Julius Konrad Werner, director of the Orthopedic Institute of Konigsberg, Prussia. Bauer and Werner, in turn, were contradicting research published by

Jacques Mathieu Delpech Jacques Mathieu Delpech (1777 – 28 October 1832) was a French surgeon born in Toulouse. He earned his doctorate from the University of Paris in 1801 and spent the next several years as a teacher of anatomy in Toulouse. In 1812 he became a surgeo ...

in 1823.

Soft tissue examples

Tendon A tendon or sinew is a tough, high-tensile-strength band of dense fibrous connective tissue that connects muscle to bone. It is able to transmit the mechanical forces of muscle contraction to the skeletal system without sacrificing its ability ...

s are

structures that respond to changes in mechanical loading. Bulk mechanical properties, such as modulus, failure

strain Strain may refer to: Science and technology * Strain (biology), variants of plants, viruses or bacteria; or an inbred animal used for experimental purposes * Strain (chemistry), a chemical stress of a molecule * Strain (injury), an injury to a mu ...

, and

ultimate tensile strength Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or F_\text within equations, is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials t ...

, decrease over long periods of disuse as a result of micro-structural changes on the

collagen fiber Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whol ...

level. In

micro-gravity The term micro-g environment (also μg, often referred to by the term microgravity) is more or less synonymous with the terms ''weightlessness'' and ''zero-g'', but emphasising that g-forces are never exactly zero—just very small (on the ...

simulations, human test subjects can experience gastrocnemius tendon strength loss of up to 58% over a 90-day period. Test subjects who were allowed to engage in resistance training displayed a smaller magnitude of tendon strength loss in the same micro-gravity environment, but modulus strength decrease was still significant. Conversely, tendons that have lost their original strength due to extended periods of inactivity can regain most of their mechanical properties through gradual re-loading of the tendon, due to the tendon's response to mechanical loading. Biological signaling events initiate re-growth at the site, while mechanical stimuli further promote rebuilding. This 6-8 week process results in an increase of the tendon's mechanical properties until it recovers its original strength. However, excessive loading during the recovery process may lead to material failure, i.e. partial tears or complete rupture. Additionally, studies show that tendons have a maximum modulus of approximately 800 MPa; thus, any additional loading will not result in a significant increase in modulus strength. These results may change current physical therapy practices, since aggressive training of the tendon does not strengthen the structure beyond its baseline mechanical properties; therefore, patients are still as susceptible to tendon overuse and injuries.

References

*Davis, Henry Gassett
''Conservative Surgery'' New York: D. Appleton & Co.; 1867
*Nutt, John Joseph
''Diseases and deformities of the foot.'' New York: E. B. Treat & Co.; 1915, pp. 157–158
(Out of copyright
Available as a pdf in total via Google books
. *Spencer AM, ''Practical podiatric orthopedic procedures.'' Cleveland: Ohio College of Podiatric Medicine; 1978. *Tippett, Steven R. and Michael L. Voight, ''Functional Progression for Sport Rehabilitation.'' Champaigne IL: Human Kinetics; 1995, {{ISBN, 0-87322-660-7, p. 4. Musculoskeletal system Anatomy articles about gross anatomy Physiology

Origin

Soft tissue examples

See also

References