A TREATISE

ON

DISEASES OF THE JOINTS.

CHAPTER I.

PHYSIOLOGICAL ANATOMY OF THE JOINTS.

To the full and clear comprehension of the different diseases to which any organ may be subject, a perfect knowledge of its structure is the first and most necessary step; therefore it is desirable, that any work, which aspires to open clear views concerning its diseases, should commence by exposing the histological and physiological conditions of that part; and the more so if that author hold certain views differing from those of previous writers on the subject. The joints of the body are generally of a complicated nature, containing several different sorts of tissue, and capable therefore of several forms of the same disease; and although it is doubtless true, that with some knowledge of descriptive anatomy, and some clinical experience, any one is able to set up an empiric and coarse classification of articular diseases, yet without a clear insight into the physiology of joints it is impossible to have any very correct notions of their pathology.

The subject, to which the ensuing chapters are devoted, is the pathology of moveable joints, and hardly touches upon the immoveable. The diarthrodial or former of these articulations is distinguished from the other not merely by its power of movement, but by the fact that in such movement one surface must glide over the other. The synorthrodial joint is not, strictly speaking, immoveable, for in one of its four classes a certain amount of motion is permitted, namely, in the amphiarthrosis. This joint consists essentially in the juxtaposition (not contact) of two

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bones with a fibrous substance interposed, which acts simultaneously as a bond of union and a means of separation. The motion, whereof this joint is capable, is permitted by the flexibility of the fibro-cartilage, not by any distinct movement of one part over another.

To our idea of a diathrodial joint is necessary, that at least two pieces of cartilage should be interposed between the bones of the articulation; each piece of cartilage lining the end of each bone, and being not continuous, but in contact, with the other. The gliding movement must take place between these cartilaginous surfaces, kept moist by a secreting membrane, which closes in the cavity of the joint. The essential constituents then of a

diathrodial joint are :—

1st. The bones, which are jointed together.

2nd. The cartilage, which lines the ends of these bones.

3rd. The synovial membrane.

But besides these are:

4thly.-Ligaments binding the bones together.

5thly.-Frequently an interarticular fibro-cartilage.

The bones, which enter into the formation of a joint, may be two or more. In the scapulo-humeral articulation is an instance of two bones jointed together; in the elbow of three, but two of these only are essential to the joint as a hinge, the other being added for purposes of its own (if it may be so expressed). In the ankle are three bones essential to the joint, two forming a socket, into which the head of the third is received. The hipjoint is composed in early life of four bones, but later it abrogates this peculiarity, the three, which formed the socket, becoming united into one. The shape of the articulating surfaces of the bones determines the species and form of the joint; descriptive anatomy divides them into four classes:

1st.-Arthrodia, or flat joint.

2nd. Enarthrosis, or ball-and-socket-joint. 3rd.-Ginglymus, or hinge-joint.

4th.-Diarthrosis, or pivot-joint.

The different species of movement, which these forms of articulation permit, have been the subject of more or less elaborate treatises, but the shape of the joint surface has no influence on the action of its diseases.

The bones of the joint may be either long, flat, or irregular, disposed together in any possible commutation; the larger and more important ones have, besides their other centre or centres of ossification, one for each joint extremity. The humerus, radius, femur, tibia, &c., have all this separation into diaphysis or shaft and epiphyses or joint extremities. The clavicle has but one epiphysis at the only end, which forms a diarthrodial joint, the proximal. The metacarpal and metatarsal bones have also but one epiphysis, which is in some instances at the proximal, in others at the distant extremity. The shaft of the bone begins to be ossified long before the epiphysis; about the sixth week of foetal life is the earliest bony deposit; it takes place in the femur, and at the ninth month most of the larger bones have made considerable progress towards the formation of an osseous shaft; but the epiphyses remain cartilaginous for weeks, even months, after birth.

It is not necessary to give here an account of the ossifying process in cartilage, nor is it my desire to append an unnecessary and therefore pedantic description of bone tissue; but, in order that the pathology of certain joint diseases may be regarded from the same point of sight as is taken in this work, it is desirable that the author's views of osseous structure should be clearly expounded. Bone is generally described as a compound of cartilage and phosphate of lime, plentifully supplied with vessels, among which a large number of branched cells are arranged in a more or less definite order. Let us describe the structure in the same language differently placed, and say :Bone consists of a number of branched cells, whose interstices (intercellular spaces) are occupied by a compound of cartilage and phosphate of lime, and among which vessels pass in a certain definite relation. By adopting this method of description the different elements of which bone is composed are reduced to their proper relation-first the cells, then the intercellular substance, and then the vascular supply. The cells of the bone are contained in the lacunæ,* the cell walls line the spaces, and the nuclei may be seen within them. Messrs. Tomes and Campbell de Morgan state that they "have had no difficulty in finding the nuclei in recent bone without the aid of chemical treatment. * Called, by their discoverer Purkinje, bone corpuscles.

If a small fragment be taken from the spongy portion of a fresh bone, and freed from adherent fat, the nuclei may be seen as small rounded bodies attached to the walls of the lacunæ."* Other observers, quoted by the above-named authorities, also believe in the persistence of the nuclei; viz., Goodsir, Schwann, Krause, Kohlrausch, Heischmann, Günther, and Donders. I possess many specimens, in which the nuclei are very evident. The lacunæ, and the cells contained in them, have not mere even, round, or oval walls, but branch out into a great number of fine processes, called by Todd and Bowman canaliculi; they are actual spaces in the hard tissue, containing a membranous matter, but whether the membrane itself be actually tubular is, to my mind, extremely doubtful. I am rather inclined to regard them simply as bundles of minute fibres; this structure would have the same effect on the transmission of fluids. A section through the dense structure of a long bone, the humerus for instance, shows the following arrangement of parts. The whole mass of the bone is disposed round an axis, so that the section is ring-shaped in the outer and inner edge of the section the disposition will be shortly described. Between these two parts the cells are seen usually to surround certain vessels in canals called Haversian, that run for the most part parallel with the axis of the bone-the whole arrangement, canal and surrounding cells, is called an Haversian system;-certain parts which fill up the interstices between these circles are named by Kölliker (Mikrospische Anatomie, p. 292) Interstitial Laminæ ; by Queckett they are more happily termed "Haversian Interspaces" (Histological Catalogue of the Museum of the College of Surgeons). In the inner and outer layer of bone, or Circumferential Laminæ, the cells are arranged round the axis of the bone; most of them are of the ordinary size and shape of the lacunæ in the Haversian systems; but there are among them certain longer cells, some of which run round the bone,† others, seen on longitudinal section, parallel to the axis; thus there are in the layer next the medullary cavity, and next the periosteum, two sets of long cells,

Observations on the Structure and Development of Bone. Philosophical Transactions, 1853, p. 117.

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+ Messrs. Tomes and De Morgan On the Development and Structure of Bone.' Philosophical Transactions, 1853.

which run at right angles to each other. I believe these are intended for the rapid absorption and disintegration of both these strata.

Some bones, the irregular ones, as those for instance of the carpus and tarsus, have no hard solid portion, but are composed of spongy texture; the long bones even terminate at their joint end or ends in a spongy portion; this in most of such bones, and certainly in all the larger ones, is formed from the epiphysis. Mr. Toynbee has made careful investigations into the ossification of epiphysal ends. The following account of the formation of vessels, to which act he chiefly directed his attention, is abridged from his admirable paper.* The first step is vascularization of the cartilage, which takes place by penetration of vessels into the epiphysal end from the side; indeed it is important to observe that the vessels do not approach within a line or two either end of the epiphysal cartilage (that towards the joint, nor that towards the shaft). The vessels once formed ramify freely throughout the cartilage; towards the further or joint end they form large loops more dilated than elsewhere. After this vascularity has continued for some time, bony matter begins to be deposited about the centre of the mass; thence spreading outwards in all directions reaches the sides, but stops short at either end, only just covering in the vessels and leaving a line of cartilage, on the one hand between itself and the shaft of the bone, on the other between itself and the joint. The latter is the articular cartilage, of which more hereafter; the former is the epiphysal junction. The value of this arrangement of an epiphysis or additional bone between the shaft and the joint is to permit growth of the bone in length, an object which is accomplished almost entirely by addition to the shaft ends. Hence the epiphyses remain unjoined by osseous matter until the full growth of the particular bone shall have been attained, and this is later in some bones than in others; thus the epiphysal bones of the upper extremity usually become united about the sixteenth to the eighteenth year, those in the lower somewhat later; the junction at the distal extremity of the femur is the latest; it is seldom entirely closed in the male *On the Organization and Nutrition of Non-Vascular Animal Tissues,' Philosophical Transactions, 1841, p. 165.