[ 94 ] MOVEMENTS OF THE FIRST By R. WHEELER HAINES, Department of , St Thomas's Hospital Medical School

INTRODUCTION though less so than those of the succeeding . The most varied opinions as to the movements of Henke (1863, p. 79) described the as passing the first ribs have been held by various workers, and outwards and at the same time upwards and back- are still to be found in modern text-books. In the wards, but Landerer (1881) could not confirm this, cadaver the first rib undoubtedly moves with the for he found the axis directed horizontally outwards rest when the lungs are inflated or the and backwards, with no upward component. drawn upwards, and Magendie (1831,. p. 378) Estimations of the degree of obliquity of the axis described this rib as moving more than other (the angle between the axis and a line drawn hori- members of the series. Sibson (1846) in a careful zontally outwards) are also inconsistent. Henke study of the dissected cadaver found that when the and Meissner gave high figures (42 and 360, tables was artificially inflated the first rib moved of Fick, 1911, p. 143), Trendelenburg, Volkmann with the others, keeping parallel to them, towards (same tables), Landerer and Fick low figures (9-16'). a more horizontal position, and Thane's (1892, Later authors have followed Braune (1888) in fig. 187) figure shows the sternum rising as a whole stating that the axis of the first rib is nearly trans- and the first rib moving with the others. But verse. Further, the shortness of the first costal Haller (1758) had found that for a moderate in- cartilages seems to preclude any movement similar spiration the lower end of the sternum moved to the lateral displacement of the lower ribs, so that forwards more than the upper end, and this was even those authors who, like Weber (1936), are taken by later writers to indicate that the manu- prepared to allow the first rib a considerable range brium, and so the ribs attached to it, could move of movement usually restrict that movement to a very little under any circumstances. Reid (1852, simple lid-like raising and lowering of the thoracic p. 834), for instance, mentions Magendie's conclusion inlet as a whole. Thane's (1892, p. 161) statement only to contradict it, and Allen Thomson (1876, that 'in the first rib the axis is nearly transverse, p. 812), though he admitted that 'on the prepared and thus while a considerable degree of elevation is skeleton, by raising and depressing the sternum the permitted the eversion is but slight', and Blair's ribs may be moved upwards and downwards nearly (1943, p. 341) that 'in the upper ribs, where the parallel to one another; the first rib moving as axis is almost transverse, the lateral movement is freely as the others', suggested that 'during life slight or absent' are fair samples of anatomical several causes combine to make the first rib more opinion. fixed than those that follow: as for example, the Yet a cursory examination of a preparation of the weight of the upper extremity, and the strain of the first rib in situ is sufficient to show that the move- intercostal muscles and the ribs beneath'. ment is not lid-like and the axis is not transverse. This uncertainty as to the amount of movement Each rib is seen to move round an oblique axis, in of the first rib has persisted in spite of the demon- inspiration the lateral border moves further from stration of considerable movement of the manu- the midline, and the directions in which the surfaces brium sterni in deep inspiration by outline tracings of the rib face are remarkably altered. This paper is (Hutchinson, 1852), photographic records (Hasse, concerned with a detailed study of the mechanisms 1901), radiographs (Macklin, 1925), and kymo- involved in the cadaver and in the living subject. graphs (Weber, 1936) and figures illustrating the movement (Keith, 1909, fig. 2), and is reflected for instance in Blair's (1943, p. 341) statement that in ANATOMICAL PREPARATIONS inspiration 'the upper border of the sternum is only Axis of movement. In a wet preparation of the slightly raised and is carried forward hardly at all'. first costal ring, from a man about 60 years of age, The mechanism of the first rib is still less under- a steel knitting needle was fixed to the rib by plasti- stood. Sibson's (1846) figures, made with the aid of cine and its position adjusted till it pointed the same a drawing machine, showed it quite clearly rising way whether the rib was raised or lowered (method from a more oblique to a more horizontal position of Henke, 1863 and Landerer, 1881). The fact that during inflation of the lungs, and at the same time this was possible showed that the rib was turning turning so that its outer border came to look more about a stationary axis and the movement was a laterally and less downwards. Several authors simple rotation. The axis was found to pass through whose results have been tabulated by Fick (1911, the head, along the neck and through the tubercle, p. 143) have published measurements showing that outwards, backwards and somewhat upwards, as the axis about which the first rib moves is oblique, stated by Henke (1863). It was very far from the Movements oJf the first rib 95 simple horizontal axis so often described, and the by 9 mm., but the distance between the costo- axes of opposite ribs met in the fore part of the body chondral junctions of the two sides, 85 mm., was of the first thoracic at an angle of 1100, so unchanged. that the obliquity, as defined above, was 35'. In Comparing the first rib with the others the actual the other ribs the axes pointed downwards rather displacement of its anterior end was less, for the than upwards, except for the second where the axis anterior end of the 7th rib of the same individual, was directed nearly horizontally. for example, moved through 45 mm., but owing to Range of movement. The preparation with needles the great length of the rib this displacement was fixed in the positions of the two axes could now be brought about by an angular movement of 140 mounted in a drawing frame in convenient positions, only, so that so far as angular movement was con- and accurate orthoscopic projections made with the cerned the first rib moved more than the others, ribs raised and lowered. For purposes of measure- and Magendie's (1831) statement on this point was ment direct vertical (Fig. 2), anterior (Fig. 4) and confirmed. lateral views are the most convenient, for the Trajectory. Since the axis of movement, if we vertical, lateral and anterior displacements of the ignore small displacements, remains stationary, it ribs can be read off from them directly, while a follows that each point on the rib must describe an view taken directly along the line of the axis arc of a circle about the axis as the rib turns, and a

Fig. 1. Orthoscopic tracings of the first rib in inspiration and expiration in a wet preparation, taken looking directly along the axis, showing the true angular movement of the rib about the axis.

(Fig. 1) gives the total movement at the costo- view along the axis will show the anterior end chondral junction and the angular movement of the moving along such an arc (Fig. 1). Other views rib about the axis. The mechanism is however show the circular trajectory projected as an ellipse, better understood from oblique views (Fig. 3), for and it is convenient to draw in the ellipse before these bring out the peculiar movements about the considering the mechanism of the rib as a whole. two axes very clearly. A wire AB (Fig. 2) is fixed so that it lies along the In the specimen illustrated the right rib turned straight line from the costo-chondral junction B to through an angle of 240. The distance from the axis the axis OAX, and meets the axis at a right angle of movement to the centre of the costo-chondral OAB. In practice since the point A is embedded in junction was 75 mm., so that the anterior end of the of the first thoracic vertebra the wire the rib was displaced through 31 mm., and the cannot actually reach the axis, though it can point sternum was displaced through a corresponding in its direction. A second wire AC is fixed so as to distance. When the specimen was mounted as pass from the axis at the same point as the first, and nearly as could be judged in the position it occupied again at a right angle OAC to the axis, but in the in life, the 31 mm. of total displacement was found plane in which the drawing is being made, i.e. the to be made up of 28 mm. of vertical and 14 mm. of plane of the paper. A third wire AD stands at right anterior movement. The maximum distance be- angles both to AC and to the axis, so that AO, AC tween the lateral borders of the two ribs increased and AD might lie along adjacent margins of a cube 96 R. WHEELER HAINES

Fig. 2. Orthoscopic tracings taken from below looking vertically upwards, showing movement of the first ribs round the oblique axes, the forward movement of the cartilages and sternum, and the lateral displacements of the shafts of the ribs. AB, AC, AD indicate the positions of wires used in the construction of 'the theoretical trajectory of the.costo-chondral junction.

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Fig. 3. Oblique view of the . Movements oJf the first rib 97 whose corner was at A. The lengths of the wires AC culty stands in the way of the acceptance of the and AD are now adjusted so that each is equal to oblique axis. If the axes were directed horizontally the distance AB, and their positions are traced on outwards the costo-chondral junctions would to the projection drawing. AB, AC and AD always be at the same distance from each other, but represent three radii of the circle which would be with the axes placed obliquely they must tend to traced by the costo-chondral junction if it turned move relatively to each other as the ribs are raised round the axis AOX, and if they have been cor- and lowered, and the short horizontally placed first rectly placed the wires will all lie in the same postal cartilages would prevent any appreciable oblique plane, the plane of the circle. Further, AD movement. This difficulty has probably caused the will, in the drawing, be superposed to AOX. rejection of the hypothesis of the oblique axis by On a separate sheet of paper a family of ellipses, workers who have considered it; certainly Weber the projections of a circle of radius equal to the (1936) in his monograph on kymography of the length of AB, are drawn by ordinary geometrical chest says that the shortness and rigidity of the procedure. The particular curve whose centre is at cartilages restricts the movement of the thoracic A, whose long axis lies along AC, and which passes inlet to a simple raising and lowering of the inlet as through the point D is now traced through on to a whole.

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Fig. 4. Antero-posterior view showing movement round the oblique (broken line) and transverse (dotted line) axes. A indicates the position of the lung in expiration, B the position it would occupy if the ribs were rotated round the transverse axis, and C the position it does occupy when they rotate round the oblique axes. the drawing, and gives the presumed trajectory of Fig. 5 shows the trajectories of the anterior ends the costo-chondral junction. The curves of Figs. 2 of a pair of isolated ribs mounted so as to turn round and 3 were drawn in this way; they are projections oblique axes. As they are raised from their lowest of circles of different diameters, 150 mm. on the point on the elliptical trajectories at AA' they right, 140 mm. on the left, because the lengths of rapidly draw away from each other so that at BB' the ribs differed on the two sides (quite a common they are much further apart, but as they pass to- condition). We now have in the same drawing wards the horizontal position their rate of separa- tracings showing the actual positions of the ribs as tion falls off, so that at CC' they are separating from they are raised and lowered, and the curves which each other very slowly and at DD' their relative would be traced out by the anterior ends of the ribs movement is zero. Beyond this they move closer if they described perfect circles round fixed axes. together, slowly at EE' and increasingly rapidly The actual and predicted positions are seen to beyond. Now the actual range of movement in life correspond closely, and the proposition that the corresponds to the part of the trajectory between ribs move about axes which are placed obliquely CC' and EE' where the relative movement is at a and not horizontally is confirmed. minimum near the point of reversal. The actual Adjustment of the trajectory. One obvious diffi- trajectories enforced by the attachments to the 98 R. WHEEL]ER HAINES unyielding costal cartilages are represented by the tiop of the anterior ends as the ribs turned during lines (straight in projection) CE and C'E', but the inspiration, and he suggested that they did in fact difference between the curved paths traced by the separate, stretching the costal cartilages as they isolated ribs and the paths enforced by the costal did so. He quoted evidence of the extensibility of cartilages is but 1*5 mm. at the maximum. The cartilaginous tissue, and presented a model in which length of the rib in this specimen is 65 mm., that of the costal cartilages were represented by extensible the neck, 25 mm., so that a movement of about springs. Fick did not, however, quote any measure- 06 mm. at the tubercle or the head is sufficient to ments in support of his views, and in the material adjust the rib to its course. Furthermore, the at my disposal there is no measurable lateral dis- maximum adjustment is required when the rib is placement of the costo-chondral junctions. near the middle of its range of movement, at the Direction of the pleural surfaces. If the right and time when the laxity of the ligaments is greatest. left ribs moved as a single unit around a horizontally So the anterior ends of the ribs turn through just placed transverse axis, they would suffer no relative those parts of the trajectories around the oblique displacement, and there would be no gain in the

Fig. 5. Antero-posterior tracings from dry turning round the oblique axes showing the trajectories of the costo-chondral junctions. In life the range from C to E and C' to E' is the part of the curves utilized.

axes where their lateral displacements will be least. distance between their outer borders during in- The directions of the necks of the ribs, along which spiration,,but in fact there is a considerable gain, the axes of the movement pass, must be adjusted which no doubt plays a part in the expansion of the so that the range of movement corresponds to the lungs. At the same time there is a reorientation of region of minimal lateral displacement. The axes the pleural surface. A in Fig. 4 shows the position must pass upwards as well as outwards, and so the at extreme expiration, B the change in position heads of the ribs must lie at lower levels than their brought about by tilting the thoracic inlet till the tubercles. It is this requirement that necessitates sternum occupies its inspiratory position without the sharp bend at the junction of the neck of the displacing the ribs relatively to each other, that is first rib with the shaft, and the atypical articulation using the supposed horizontal axis. The pleural of the head with but one vertebra. surfaces of the ribs now face more outwards than Fick (1911) suggested quite a different mechanism. before, and would allow the lung to expand to the He described the axes of the ribs as oblique but position indicated. In C, however, the ribs are horizontal, so that they passed from the heads out- shown in the position enforced on them by the true wards and backwards but not at the same time axis. Not only is the vertical and lateral displace- upwards. This would lead to a considerable separa- ment of the middle of the shaft greater than it would Movements of the first rib 99 be if the movement were about a horizontal axis, ribs could be felt as they moved beneath the skin, but the pleural surface faces more downwards and and in one of these subjects, a physiotherapist who less inwards, and the expansion of the lung is had specialized in respiratory movements, the first correspondingly increased. ribs could be seen moving relatively to each Geometrically when a plane surface rotates about other. an axis the change in direction in which the plane In the preparation shown in Figs. 1-4 the faces depends on how the surface is set on the axis. sternum was found to move 28 mm. upwards and The change is zero if the axis is set vertically to the 14 mm. forwards and it was important to check plane, and increases with the angle of obliquity of whether this range of movement could occur in life. the axis to the vertical (very nearly as the sine of The measurement is rather difficult to make, for, the angle for small rotations), and the change is as is well known, most subjects tend to straighten maximal when the axis is parallel to the plane (here the thoracic part of the curvature of the vertebral for each degree of rotation about the axis the column in deep inspiration, and this exaggerates the direction in which the plane faces changes by a full movement of the sternum. Ransome (1873) fixed degree). In the first rib the maximum cannot be the back by seating his subjects on a straight-backed realized for the precise direction of the axis is chair, and recorded the thoracic movements with determined by other mechanical requirements an ingenious machine which automatically analysed already discussed. But the angle of obliquity of the the displacements of a button pressed on to the axis to the pleural surface of the rib is over 600, so thorax into their vertical, antero-posterior and for each degree of rotation the pleural surface turns medio-lateral components. In a healthy male of through about 0.90. If on the other hand the axis 45 he found movements of 84 mm. upwards and were transverse the angle of obliquity would be 22 mm. forwards, and a calculation from his eleven about 450, and the pleural surface would then turn records for males gives an average of 21 and 15 mm. through about 0.70 only for each degree of rota- So the movements in my preparation, though they tion. are above the average, as might be expected from Rather similar movements in other ribs have the size of the first ribs in this individual, are by no been ascribed to a 'bucket handle' movement of means exceptional. the rib about an axis passing through the head of In radiographs the relative displacements of the the rib and costo-chondral junction, forced on the lateral borders of the first ribs can be seen and rib by the 'resistance' of the sternum (Meyer, 1885, measured. In two series from young males taken and many modern writers). In the first rib any such specially for the purpose of measurement, with the movement is absolutely excluded by the rigidity of centre of the cone of radiation passing at the level the vertebral attachments which prevent any of the first rib, the movement was 10 and 11 mm. measurable movement about such an axis. Nor is Allowing 2 mm. for distortion the movements were such a movement at all necessary to account for the about 8 and 9 mm., measurements which agree well lateral displacement of the rib or the reorientation with those made directly on the cadaver. Further, of its pleural surface. Indeed isolated ribs mounted the changing direction of the pleural surface is so as to turn about axes passing along their necks clearly seen in the radiographs. Similar displace- describe the wing-like movements just as well as ments of the lateral borders can be seen in the stock ligamentous preparations with the sternum pre- radiographs used for teaching, and in many of those served (Fig. 5). figured in the literature (e.g. Macklin, 1925), but The observations and deductions have been when the cone of radiation is centred below the repeated on several occasions from dead bodies of level of the first rib the change in direction of the both sexes, including a young man of 22 known to pleural surfaces is not demonstrated so clearly. have been in the best of health up to the time of his Lateral views are disappointing, as the soft tissues death from head injuries. The material includes are too opaque to allow satisfactory films to be specimens with the whole of the thoracic cage obtained. intact, and others with the manubrium sawn Taken alone observations on the living subject through below the attachment of the first costal would tell little of the mechanism, but so far as they cartilages. The detailed measurements vary from go they confirm the conclusion that each rib is one individual to another but the same general turning round its own oblique axis. features are found in all the normal material examined. CALCIFICATION OF THE THE LIVING SUBJECT COSTAL CARTILAGES In life the first rib is difficult to observe, but in two The contradictions in the various accounts of the subjects, both female, the outer borders of the two movements of the thoracic inlet, and the prevalence R. WHEELER HAINES of the statement that the axis of the first rib is SUMMARY transverse or nearly so may be due to the study of 1. The movements of the first ribs have been specimens with reduced mobility of the first costal studied in the cadaver and in the living subject. cartilage. In such a specimen, taken from a 2. The first ribs do not turn round a transverse relatively young woman of 45, in which the carti- axis common to both ribs, b'ut each rib turns round lages were completely calcified and there was no an oblique axis passing outwards, backwards and recognizable movement between the first rib and upwards along its neck. the sternum, the axis was transverse, the displace- 3. The angular movement about the axis is ment of the sternum was limited to 12 mm., and the greater in the first rib than inthe others of the series. ribs, cartilages and sternum moved round the axis 4. The shaft of the rib is displaced upwards and as a single unit. A more detailed study showed that laterally in inspiration and the pleural surface the common axis passed through the two costo- comes to look more directly downwards. transverse , whose ligaments were strong, but 5. The axes are so placed that the costo-chondral fell well behind the costo-vertebral joints, whose junctions can remain at the same distance from ligaments had become very lax, so as to allow the each other as the ribs are raised. The direction of head of the rib to slip upwards and downwards on the neck relative to the shaft and the atypical the body of the vertebra. articulation of the first rib with but one vertebra Other specimens showed conditions intermediate are determined by this requirement. between the extremely oblique type of axis de- 6. The rotation round oblique axes leads to a scribed earlier and the transverse type, with 200 and greater expansion of the lungs than would be 140 of obliquity. Here there was some limitation of brought about by a rotation round transverse axes. movement, particularly of the lateral displacements 7. Calcification of the first costal cartilages leads of the ribs, and the costal cartilages were found to to a limited movement of the ribs and sternum as a be partially calcified. It seems probable that single unit about a transverse axis. similar specimens have been examined by those authors who have described the axes as nearly My thanks are due to Prof. A. B. Appleton for transverse, for they form the bulk of the material the anatomical material, and to Dr J. W. McLaren available to anatomists. for the radiographs.

REFERENCES BLAIR, D. M. (1943). 'Arthrology.' In Cunningham's MAGENDIE, F. (1831).. An Elementary Compendium of Text-book of Anatomy, 8th ed. Oxford Univ. Press. Physiology for the use of Students. Tr. E. Milligan, 4th ed. BRAUNE, W. (1888). Arch. Anat. Physiol., Lpz., p. 304. Edinburgh: Carfrae. FICK, R. (1911). Handb. Anat. Mensch. Gelenke, Th. III. V. MEYER, H. (1885). Arch. Anat. Physiol., Lpz., p. 253. Jena: Fischer. RANSOME, A. (1873). Med.-chir. Trans. 56, 82. HALLER, A. (1758). Memoire sur plu8ieur8 PhUnomene8 REID, J. (1852). 'Respiration.' In Todd's Cyclop. Anat. Importante8 de la Respiration. Lausanne. Quoted by Phy8iol. 4, 325. London: Longman, Brown, Green, Reid (1852). Longmans and Roberts. HASSE, C. (1901). Arch. Anat. Phy8iol., Lpz., p. 273. SIBSON, F. (1846). Philos. Trans. 136, 501. HENKE, P. J. W. (1863). Handbuch der Anatomie und THANE, G. D. (1892). 'Arthrology.' In Quain's Elements of Mechanik der Gelenke. Leipzig and Heidelberg: Winter. Anatomy, 10th ed., 2, pt. I. London: Longmans, Green HUTCHINSON, J. (1852). 'Thorax.' In Todd's Cyclop. Anat. and Co. Physiol. 4, 1016. London: Longman, Brown, Green, THOMSON, A. (1876). 'Myology.' In Quain's Elements of Longmans and Roberts. Anatomy, 8th ed., 1. London: Longmans, Green and KEITH, A. (1909). 'The mechanism of respiration in man.' Co. In Leonard Hill, Further Advances in Phyiiology, p. 182. WEBER, H. H. (1936). 'Die normal Atmung.' In Stumpf, London: Arnold. Weber & Weltz, Rontgenkymograpische Bewegungs- LANDERER, A. (1881). Arch. Anat. Physiol., Lpz., p. 272. lehre innerer Organe, p. 242. Leipzig: Thieme. MACRKLN, C. C. (1925). Amer. J. Anat. 35, 303.