The nature of bones and joints: a new perspective.
ML Kothari, LA Mehta, M Natrajan
Department of Anatomy, Seth G. S. Medical College, Parel, Bombay, Maharashtra.
M L Kothari
Department of Anatomy, Seth G. S. Medical College, Parel, Bombay, Maharashtra.
In human ontogeny recapitulating phylogeny, bones arrive late on the scene--long after neurogenesis, musculogenesis, organogenesis and so on are over--as islands of ossification in an ocean of collagen. This study confirms this developmental sequence by demonstrating, in cadavers, the rather independent nature of bone, to which nothing--muscle, tendon, ligament or articular cartilage--is attached. Bone is like the air in a tubeless tyre; it gives rigidity and shape to the tyre, and in return takes the shape of the tyre. The tibia, for example, is the bony tissue that is contained in tyre-like casing made of peritibial soft tissues whose inner limit is the periosteum, which continues proximally and distally as capsules of knee/ankle joint, and to which only are the articular cartilages of the knee and ankle attached, being clearly free from the bones. This study also exposes the truer nature of a joint wherein the articular cartilage assumes anatomic and physiologic significance hitherto unthought of.
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Kothari M L, Mehta L A, Natrajan M. The nature of bones and joints: a new perspective. J Postgrad Med 1990;36:143-6
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Kothari M L, Mehta L A, Natrajan M. The nature of bones and joints: a new perspective. J Postgrad Med [serial online] 1990 [cited 2022 May 20 ];36:143-6
Available from: https://www.jpgmonline.com/text.asp?1990/36/3/143/844
Modern physics has it that all the visible stars and planets, galaxies and nebulae constitute a mere 10% of the material universe comprising 10 84 atoms. The remaining 90% is in the form of invisible plasma forming the invisible matrix from which stars are made and into which stars dissipate.
The bones of the human body are comparable to the visible part of the universe; they seem to be the core round which the trunk and limbs are constructed. Muscles, tendons and ligaments are "attached" to them; the brain and the cord are housed or "contained" in the skull and the vertebral canal. Nerves pass through a foramen or a bone.
In reality, the bones - the skeletal system - are nowhere in early embryogenesis, comprising the formation of the entire human being sans the bones. The muscles, tendons, central nervous system and nerves are all there as an oceanic continuum of tissues in which the bones make appearance as an island here, island there, in a staggered fashion. The shoulder muscles, ranging from the massive trapezil to the slender coracobrachialls are all there before the scapula and the humerus appear. This clearly means that, in reality, the humerus is attached to deltoid, the clavicle forms in the path of "supraclavictilar" nerves, and all the bony cases -skull, orbit, vertebral canal-develop round their preformed contents. The same sequence - a soft-tissue organ developing an island of ossification -applies to the formation of os cordis, os penis or os sclerae.
The ontogenic change from softness to hardness is certainly a repetition of the phylogenic change from invertebrateness to vertebrateness. (The largest invertebrate, the squid, is a massive powerful marine animal, 30'-80' in length, many tons in weight, and unmatched in its rapid swimming by jet-propulsion. It is thus larger and more powerful than many a vertebrate animal. The squid eye is considered the most perfect and beautiful eye, measuring 30-40 cms., in diameter. Being an invertebrate does not seem to be a handicap, nor being a vertebrate, an asset). When the soft interior of a newt or a salamander got ossified, the earliest fish was born. This bony fish then evolved further into two main groups-the purely cartilaginous fishes the sharks, and the cartilage-cum-bony fishes, reptiles, and finally birds and mammals. Each vertebrate begins its career as a pure invertebrate.
If the above logic holds water, we may be able to demonstrate the islandish nature of bone, to demonstrate its arrival late in life of a tissue, to divest bone of the myriad of assumed attachments of muscles, tendons and ligaments. All this is possible, as follows.
Cadeveric parts, divested of the skin, were immersed for a period of 34 weeks in a decalcifying solution made up of 10% Nitric or Hydrochloric acid. Sufficient decalcification was indicated by the bendability of tibial or humoral midshaft or the ilium. The parts were then dissected to discover the nature of bones. The following observations are reproducible and bear out the logical preamble above.
1. Bone stands apart:
On inspection of the dissected parts, in longitudinal or transverse sections, the most consistent feature was the continuity of all the soft tissues standing in contrast to the manifest isolatedness of bone. It required the rounded tip of the gloved finger to find the plane between a bone and its ambiant tissues. When the finger was navigated round about the entire bone, the whole bone-cortex and medulla intact - could be levered out, leaving its case intact and flush with the peri-osseous tissues (See [Figure:1]). In the vertebral region, or the foot, the blunt tip of the forceps could lever out the vertebral centrum or the calcancum out of the casing.
II. Articular cartilage, free from the bone, is anchored all around:
In absolute contrast to the "articular" ends of a bone, its articular cartilage, standing clearly separate from the bone and only abutting on it, is continuous with the soft tissue casing.
Taking the knee as an example, its bones, femur and tibia are each housed in respective casing. The upper wall of the femoral casing is the articular cartilage of the femoral head, and the lower wall is the articular cartilage over the femoral condyles, the whole "femur" lying free in between. So for the tibia. The knee joint cavity, thus consists of its capsule as the side walls and the femoral condylar cartilage as its roof and the tibial plateau's cartilage as its floor, (See [Figure:2]).
Microphotographs of the articular cartilage show it to be continuous (See [Figure:3]) with the surrounding soft tissue. The nutrition of an articular cartilage should be little less of a problem given the fact that it is one continuous thing with the entire soft tissue casing.
III. Joint ligaments are attached to cartilage and not to bone:
The cruciate ligaments of the knee and the round ligament of the femoral head are clearly one with the articular cartilage and through it with the soft tissue casing, having NOTHING at all to do with the bone (See [Figure:4], [Figure:5]). The same holds true for all the capsules and the periarticular ligaments.
IV. Vertebral column is not what we thought it to be (See [Figure:6])
The entire vertebral column, through the revised view, turns out to be like a sock filled with carrom-strikers and carrom coins. The strikers, representing the intervertebral disc, are circumferentially attached to, and microscopically also one with the sock. Between two strikers is a coin, albeit, much taller than the striker, that fills in the space in such a way that the sock remains free anteriorly and posteriorly to constitute the so-called anterior and posterior longitudinal ligaments.
V. Tendons terminate nowhere:
The tip of a tendon apparently looks like a point where the tendon fibres have zeroed in onto a specific bony point. No fallacy could be greater. The tendons of the long flexors and extensors of the fingers/toes were attached to no bone, and were imperceptibly merging into the soft tissue. As a very illustrative example, the tendons of tibialis posterior, tibialls anterior and the peroncus longus met one another to become continuous with each other at a point at the base of the first metacarpal (See [Figure:7]).
VI. Cortical bone is condensed spongy bone:
[Figure:8] shows tibia removed from its casing. How interesting that it still looks very much like the tibia. [Figure:9] shows X-ray of the same taken with a beam used for X-raying of soft tissues. The shadow of the decalcified tibia in density- is close to that of the soft tissue of the fingers that are holding it, and quite distinct from the bones of those fingers.
A bare-handed study of this tibial specimen showed that the cortical bone is Just like the spongy bone, save that at the cortex the sponge is closely packed. Much as the spongy bone can be pulverised by fingers, so can be cortical bone be reduced to a fine powder. The external surface of the bone, in this case of the tibia, is but the compacted spongy bone reduced into a flat surface by the pressure of the soft-tissue casing in which the bone is contained.
There are a number of corollaries to the above bone-and-jointperspective.
1. Continuity of all non-osseous tissues:
From head-to-foot, dorsoventrally and side-to-side, there is an uninterrupted continuity of tissues, a reflection of the fact that the entire embryo sprang from a single cell, the zygote. In a coronally or sagittally sectioned head, a tug on the tongue could move the dural folds and vice versa.
2. Nature of a bone:
Take an inflatable toy made of a collapsible, rollable plastic but capable of assuming the shape of a duck, a rabbit or a camel on being pumped in with air. A tubeless tyre of a car is flat without air, but on being filled in with air, it assumes its functional shape. In the body, a bone as such is like the air, being separate and separable from its casing provided by all the soft tissues around. In a way, it is like the air itself that assumes the shape of the plastic toy or the tyre.
Any bone, large or small, flat or long, is a calcified unit of tissue that rigidly, strongly and almost incollapsably fills in a casing provided by the soft tissues around, so that both the casing and bone assume a characteristic shape. The so-called ligaments, muscles and tendons are an integral part of the soft tissues and seem to be attached to the bone, but in fact are in no way so. This would explain why the radiological outline of a bone, despite its myriad attachments is so streamlined and smooth (See [Figure:10]).
As a building material, bone has naturally been compared to steel, having many of its qualities without having its weight or bulk. In the absence of the bone's attachment to any fascia, fibres, muscles, tendon, ligament or cartilage, the bone serves as a single body of cavernous tissue that is a meeting place of solid, liquid and air, a confluence that allows it to obey hydrodynamics and pneumodynamics that render any impact or compression to be transmitted equally in all directions. No wonder that a single femoral head, in an average person, can easily withstand a compression load of as much as 3600 pounds.
3. Nature of a joint:
The true cavity of a synovial joint is forme by its capsule and the two attached cartila ginous plates. Being an enclosed system con taining synovial fluid, it obeys Pascal's La that serves to preserve the integrity of the joint both at the capsular and articular levels.
4. Muscles - no origin or insertion:
A muscle is attached to nothing, bein overlaid over a continuum of collagen. At best a muscle can be said to have two ends - convergent/divergent, upper/lower, proximal/distal, medial/lateral, and so on.