THE WRIST JOINT by R

A DETAILED STUDY OF MOVEMENT OF THE WRIST JOINT By R. DOUGLAS WRIGHT, M.S.

INTRODUCTION THE most precise and the most differentiated movements of the limbs are those which occur in the hand. It is generally assumed that this refinement is based on the mobility of the thumb and the lengthening of the digits associated with a highly developed neuromuscular mechanism. On closer study there appears a much more stable basis for this free but accurate movement. The range of mobility of the wrist joint is as great as that of the shoulder joint, but added to this range of mobility there is a constant steadiness resulting from the intricate admixture of arthrodial, enarthrodial, and ginglymus types of articulation. The descriptions which are given in text-books of the actual movements of the carpus are very abbreviated, and in most cases inaccurate. Apart from the anatomical exercise of understanding the changes in the axes of the short bones taking part in the most complicated joint in the body, the movements of this joint in the use of the hand and the increasingly accurate recognition of conditions of disease and trauma in the carpal bones and associated joints render a precise knowledge of movements of these essential to accurate clinical diagnosis, treatment and prognosis.

METHOD OF INVESTIGATION The kinematics of the wrist joint have been studied by Fick(l), by in- spection of the moving dead joint and plane X-ray photographs; by Bryce(2) using plane X-ray photographs of the living hand; by Johnston (3) who fixed the dead joint in varying positions and then dissected the bones, and by van Bonin (4) who investigated the movements of a living hand by stereoscopic X-ray films. Most of what is recorded in the present report will be found in those papers, but as these results are widely different from many of the previous statements, the observations on mechanism will be set out without reference to the previous articles. It is an intricate subject for description, and reference to other similar or conflicting observations is confusing. The following methods of investigation were employed: (1) Stereoscopic X-ray films of the movements of the living hand were taken. (2) The implantation of long needles into the several bones of the forearm, of the proximal and of the distal carpal rows, allowed an observation of the 138 R. Douglas Wright axial movement of the bones in a recently dead hand when the wrist was motivated by pulling on appropriate tendons and when the ligaments were still intact. (3) As a check on these observations and to aid visualisation of the movements represented in the two preceding methods, wrist joints, fixed but lax, were dissected and arranged to correspond to the disposition of the living bones seen stereoscopically and the dead ones "seen" by the movements of the needles. This also promoted renewed observation on the anatomy of the joints and joint surfaces. ANATOMICAL CONSIDERATIONS The first anatomical feature studied was that of the curves of bones, collectively and separately. The proximal surfaces of the proximal row of carpal bones, when viewed by an antero-posterior rdntgenogram, form an almost perfect arc of a circle of which the centre is at the middle of the waist of the capitate bone (Plate I, fig. 1). Secondly when the navicular has its long axis parallel to that of the radius, the ulnar surface forms .with the distal surface of the lunate bone about one-third of the circumference of a circle, the centre of which is approximately the centre of the head of the capitate (Plate I, fig. 3). This is necessarily so because it is the curved radial surface of the capitate which fits into this line. The antero-posterior curve on the distal capitellum of the navicular has its axis in line with the axis of the antero- posterior curve of the head of the capitate, i.e. a line passing transversely in the coronal plane through the centre of the head of this bone. The ligaments of the wrist joint are most strongly developed on the volar aspect. The transverse ligament of the carpus needs no detailed mention; its function in maintaining the transverse arch of the carpus, in addition to that of a retinaculum, is not always appreciated. The strong transverse ligament which joins the volar surface of the triquetrum to that of the navicular is concerned with two movements which will be detailed later; it forms the volar surface of the cup in which the head of the capitate moves in the movements of extension, and when the hand is in the straight position with this ligament relaxed, ulnar deviation now produces a widening of the angle between the long axes of the triquetrum and the navicular in the coronal plane. This allows the greater width of the distal part of the hamate to shift proximally in this movement. The two collateral ligaments, between attachments, have axes in different lines, the ulnar ligament is distributed to the ulnar, volar and dorsal surfaces of the triquetrum and hamate; the longitudinal portion of the radial collateral ligament is attached wholly to the volar surface of the styloid process of the radius and to the volar surface of the tubercle of the navicular; this ligament prevents the movement of the navicular past the straight position in dorsi-flexion, i.e. extension, of the wrist. The inter-osseous ligaments of the two carpal rows vary greatly in strength. That uniting the lunate to the navicular is very poorly developed in the middle portion; the volar and dorsal portions are much longer than the distance A Detailed Study of Movement of the Wrist Joint 139 between two bones when they are approximated, this allows the movement of the navicular bone relative to the lunate which occurs in flexion and that of the lunate on the navicular in extension. The relative immobility of the triquetrum on the lunate is due more to the large surface of apposition and the volar and dorsal ligaments than to the inter-osseous ligament. The lunate and capitate bones are firmly united by the massive inter-osseous ligament; the capitate is very feebly joined to the lesser multangular and the greater multangular is weakly joined to this. The freedom of the multangulars will be noticed when the description of the deviations of the hand in a coronal plane are described. Synovial membranes of the wrist joint are mainly studied and reported relative to complexity; this may account for occasional localisation of disease to isolated portions of the membrane. The most noticeable feature of the membranes of the radiocarpal and transverse carpal articulations is the extent of them; when the joint is in the resting position they present as extensive pouching folds especially on the dorsum in the radiocarpal joint and on the volar surface of the transverse articulation. Associated with these more marked folds synovial fringes frequently occur. The facets which appear on the articular cartilages of the bones are usually the result of continuous contact with an opposing facet, but some of those occurring in the wrist joint are the result of occasional contact, e.g. that between the hamate and lunate, that between the neck of the capitate and the anterior edge of the waist of the navicular.

MOVEMENTS The changes in arrangement of the carpal bones from the disposition which is present when the hand is in the straight position will be described in ulnar deviation, radial deviation, flexion, extension and forced extension. There are some features of the normal straight position which must be detailed before proceeding with this description (Plate I, figs. 1 and 2). The distal surface of the lunate faces distally and slightly dorsally, the triquetrum is in a straight line with the bones of the forearm, but the navicular lies with its long axis at 300 anteriorly to the coronal plane of the forearm; it is slightly rotated round this long axis so that the anterior portion of the distal extremity comes to lie in front of the head of the capitate. The greater and lesser multangulars ride on the middle portion of the distal capitellum of the navicular. The capitate and the hamate lie in line with the metacarpals, the former inclined slightly dorsally relative to the lunate; the hamate has its axis parallel to that of the capitate. Even when the hand is maintained in the straight position, the position of the radial carpals may be modified by movements of the thumb. In extension of this digit the greater multangular moves radially to the lesser multangular, and in flexion it rotates on the head of the navicular; a portion of it is then in front of the lesser multangular in the antero- posterior view. In abduction of the thumb the slight movement of the greater 140 R. Douglas Wright multangular is accentuated by a 100 increase in the volvar flexion of the navicular. Ulnar deviation (Plate I, fig. 3) is mainly a gliding movement of the proximal row of the carpal bones on the radial and triangular ligament surfaces. The centre of this movement is the centre of the waist of the capitate, the line of movement is a portion of the arc formed by the proximal surfaces of the proximal carpal row. The ulnar edge of the lunate comes to lie "lightly radial to the ulnar border of the radius. The extent of this movement is about 260, but the total deviation of the middle line of the capitate and third metacarpal from the sagittal plane of the supinated forearm is about 320 in the coronal plane. This discrepancy of 60 is found in the movement of the distal carpal row on the proximal row. The axis of this movement is antero-posterior through the centre of the head of the capitate; the axis of the capitate moves in a coronal plane through 60; the hamate, because it is closely bound to the capitate, moves proximally toward and often makes contact with the lunate. The wedge-like action of the hamate splays the proximal row slightly, as previously noticed. The greater and lesser multangulars follow the capitate, and the long axis of the navicular swings into longitudinal axis of the forearm with the multangulars on the most volar portion of the cartilage of the navicular capitellum and moved approximately 5 mm. in the ulnar direction relative to this surface. Throughout this report, the extent of a movement will be referred to as the angle between two planes, two lines or that between a plane and a line in a given plane. The extent of movement at the wrist joint is usually given as so many degrees, but no specified lines are given. The angle recorded between the hand and forearm will vary greatly according to whether the radial or styloid process or the articular surface of the radius is taken as the point of angle and what are the distal points of the line; ranges of movement reported without specification of points of reference are therefore valueless. Radial deviation (Plate I, fig. 4) in the coronal plane is possible to the extent of 220 between the middle line of the third metacarpal and the sagittal plane of the forearm. This movement takes place at the transverse carpal row entirely; no movement of the proximal row as a whole occurs relative to the radius. The axis of the movement is antero-posterior through the centre of the head of the capitate; the hamate is carried distally away from the lunate and allows the triquetrum to more closely approach the capitate: the multangulars move 3-5 mm. radially and dorsally on to the most proximal portion of the facet on the capitellum of the navicular. This bone becomes slightly more volar-flexed and rotated on the long axis than is the case in the resting position. This volar movement of the navicular and the distal movement of the hamate produce about 8 mm. of narrowing of the distance between the tuberosity of the navicular and the lateral border of the triquetrum. Flexion of the wrist (Plate I, fig. 5, and text-fig. 1) is compounded of movement at the radiocarpal and at the intercarpal joints. The lunate and A Detailed Study of Movement of the Wrist Joint 141 triquetrum flex 300, so that the distal surface of the lunate faces distally and slightly volarly. The navicular swings still further volarly on the lunate, so that the proximal surface points almost directly dorsally and the long axis of the bone in the sagittal plane is at right angles to the long axis of the forearm. The distal facet on the proximal portion of the navicular thus forms the dorsum of the socket for the ball of the head of the capitate in this movement. The capitate with the hamate, lesser multangulars and metacarpals rotates 500 around a transverse axis through the middle of the head of the capitate: as the curve of the navicular capitellum is on a circumference relative to this centre, the multangulars move on to the most volar portion of this facet. It is there-

Text-fig. 1. Composite tracing from rontgenograms of flexion and extension. The bones of the forearm were fixed. The exposures for flexion and extension were made on separate films and later compounded. The result is self-explanatory. fore apparent that the greater part of the flexion movement takes place at the intercarpal joint, and that disease of this joint leads to a greater disability than does a lesion of the radiocarpal joint. Extension is also a compounded movement (Plate I, fig. 6, and text-fig. 1). At the radiocarpal joint the lunate and triquetrum move through 28° and come to face posteriorly and distally. The navicular swings with and on the lunate until its long axis is in line with that of the forearm; it never moves posteriorly to this line. The anterior disposition of the radiocarpal ligament and the association with the tendon of the flexor carpi radialis muscle are responsible for this limitation. The distal carpal row moves 160 on the axis transversely through the centre of the head of the capitate. The volar surface of the socket for the head of the capitate is formed by the strong ligament joining the triquetrum and hamate, and by the distal facet of the dorsally tilted lunate bone. The multangulars slide on to and even beyond the most proximal portion 142 R. Douglas Wright of the capitellar facet. When this movement is completed, the most distal point of the carpus is the capitellum of the navicular with the hook of the hamate slightly proximal to this plane. Forced extension accentuates this position very slightly. In falling on to the extended hand the force is taken directly on to the small head of the navicular. SUMMARY Radial deviation occurs entirely at the transverse carpal joint. Ulnar deviation is almost wholly a sliding movement of the radiocarpal joint. Flexion and extension are compounded of radiocarpal and transverse carpal joint movements with the latter the more extensive. The navicular bone shows a wide range of movement in relation to the other bones of the proximal carpal row. REFERENCES (1) FICK (1901). Verh. anat. Ges. Jena, p. 175. (2) BRYCE, T. H. (1896). "Certain points in the Anatomy and mechanism of the wrist joint reviewed in the light of a series of Roentgen ray photographs of the living hand." J. Anat. and Physiol. vol. xxxi, p. 59. (3) JOHNSTON, H. M. (1907). "Varying positions of the carpal bones in the different movements at the wrist." J. Anat. and Physiol. vol. XLI, Pp. 109, 280. (4) VAN BONIN, G. (1929). "A note on the kinematics of the wrist joint." J. Anat. vol. LXI, p. 259. EXPLANATION OF PLATE I Fig. 1. A lateral rontgenogram of the wrist in the straight (not flat) position. The position of the lunate bone (L) with the navicular (N) inclined at an angle to it are shown. The capitate and hamate are slightly dorsally inclined. The greater multangular is shown on the middle of the capit1ellar facet of the navicular. Fig. 2. Antero-posterior rontgenogram of wrist in straight position. Note relation of the lunate to the radius and that of the long axis of the capitate to the radius. The navicular is foreshortened due to volar flexion; it slightly overlaps the capitate due to rotation on its longitudinal axis. Fig. 3. Antero-posterior rbntgenogram in ulnar deviation. The change of relation between the lunate and radius is evident: the navicular has come into line with the radius. The rotation of the capitate around the axis through the centre of the head is shown. The multangulars have moved in an ulnar direction on the capitellum of the navicular. Approximation of the hamate to the lunate produces splaying of the proximal row of carpals. Fig. 4. Antero-posterior rontgenogram of the wrist in radial deviation. The lunate bone has much the same relation to the radius as in the straight position but the capitate has moved much relative to the lunate carrying the hamate with it. The navicular is shown foreshortened due to further volar flexion and the multangulars have moved radially on the navicular. Fig. 5. Lateral view of wrist joint in full flexion. The edge of the navicular has been drawn in black; full flexion of this bone and the capitate with little change in the position of the lunate (L) is shown. The greater multangular has moved on to the most volar portion of the navicular capitellum. Fig. 6. Lateral rontgenogram of wrist in full extension. The movement of the lunate is seen with the navicular (drawn in white line) approximately in line with the bones of the forearm. The capitate is fully extended and the greater multangular has moved proximally and dorsally on the navicular capitellum. Journal of Anatomy, Vol. LXX. Part 1 Plate I

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