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THE STRUCTURE PROXIMAL R. S. From The familiar outline slightly flattened head, ridge (Fig. 1 Frontal ). and fragile medulla reversed, and a thin forms the internal the AND FUNCTION OF END OF THE FEMUR GARDEN, Orthopaedic Departmnemit, ofthe proximal neck and two end ofthe trochanters section uppermost of the cortical of the shaft (Fig. 2). shell clothes weight-bearing system INTERNAL The a calcar vertical femorale, plate ofbone PRESTON, lying deep third of the neck (1900) to the lesser margin group, of the head. The lateral arrangement arises from the lateral femoral cortex area Royal and Infirmary femur head WEIGHT-BEARING medial as the trabeculae Preston the of trabeculae group, which junction of of lessened density This interpretation neck and it trochanter. in the streams three-dimensional features descriptions of the calcar of the femorale powerful cortex 3). the “ The true calcar neck forms of the femur,” the distal is anchorage internal weight-bearing system, sometimes upwards to end fan-wise at the articular of trabeculae, sometimes and curves upwards and shaft. appearance However, the SYSTEM described Enclosed these system known medially of trabeculae to decussate within known as Ward’s triangle. of the internal weight-bearing and from the radiographic so well foresaw (Fig. 4). shows (Fig. group in the femoral head. A third group of the cortex at the level of the lesser trochanter at by its almost spherical intertrochanteric Above the lesser trochanter this arrangement is the dense arrangement of cancellous bone which of the known the compression medial aspect arrangement compression ENGLAND femur is characterised with their communicating in the or as Bigelow THE springs with trabecular derives from the the lateral systems largely from of the femora! neck and head which both diagram and radiograph fail to proximal end of the femur, and internal weight-bearing as the tension to merge with is the Ward (1838) Ward’s diagram demonstrate the and for this reason the system are inadequate. above The femoral neck inclines upon the shaft at an angle of about 127 degrees, ranging normally between I 13 and 136 degrees (Humphry 1888). The neck is also set upon the shaft at an angle varying from 38 degrees anteversion to 20 degrees retroversion, but which is usually in the region of 10 degrees anteversion (Kingsley and Olmsted 1948). In the opposite direction the neck itself shows a slight curvature with its convexity directed forwards (Walmsley 19 1 5). This twisting the upright to a vertical is striving and turning position direction. towards presumably which demands It also suggests that, It is hoped a spiral/ornz. a better understanding By stereo-radiography represents conversion of the internal the calcar system are seen to be an upward shaft, and the lateral trabeculae lateral cortex. The medial conformation 576 of the group the response stresses in basic to show weight-bearing femorale and bearing of the group an antero-superior the following experiment former to represent the which the radiological developmental of the weight-bearing and spiral an expanded of trabeculae outline, that the this proximal observation occupies end of the femur of the the internal and femur key to weight- of the postero-medial continuation of the a postero-inferior to an oblique provides system. media! trabeculae continuation and rotated of the from the cortex anterolateral position in the femoral neck. This description may be clarified by in which a tube of multiple parallel wires is mounted on a wax radio-opaque Haversian systems with their concentric lamellae on appearance of the femoral shaft depends (Fig. 5). The spiral proximal end of the femur suggests THE that JOURNAL its peculiar OF BONE angulation AND JOINT has SURGERY TIlE AND FUNCTION OF THE PROXIMAL FIG. 1 posterior aspect of the proximal end of the femur. Figure 1-The of the femur STRUCTURE to show preponderance FIG. 3 of cortical bone END OF FIG. Figure 2-Frontal in the shaft and of cancellous THE FEMUR 2 section of the upper bone in the neck and FIG. 577 third head. 4 weight-bearing system in the femoral neck. M-medial system of lamellae; L-lateral system of lamellac; W-Ward’s triangle; and 1-intertrochanteric arch. Figure 4-Diagram from Outlines of Human Osteology, F. 0. Ward, 1838, for comparison with radiographic appearances. (Reproduced by permission of the Editor, Journal of Bone and Joint Surgert’, American volume.) Figure 3-Internal VOL. 43 B, NO. 3, AUGUST 1961 578 P. S. GARDEN FIG. S FIG. 6 Figure 5-Radiograph of tube of parallel wires. Note appearance of “cortex” where wires are superimposed. Figure 6-Disposition of wires after twisting tube to show their similarity to the pattern of the medial and lateral lamellae in the internal weight-bearing system. FIG.7 FIG.8 Wire model bisected in the line of its spiral. Figure 7-Horizontally arching disposition of the wires in the antero-lateral half. Figure Vertical disposition of the wires in the postero-rnedial half. THE JOURNAL OF 8- BONE AND JOINT SURGERY THE been STRUCTURE achieved and then produce weight-bearing FUNCTION developmentally backward antero-lateral and Similar (Fig. shadow 6). -, THE PROXIMAL twisting twisting closely Bisection postero-medial - OF by simple direction. a radiographic system to AND ofthe END of the original tube ofparalle! OF THE shaft FEMUR 579 in an inward, wires forward is found, in practice, resembling the trabecular pattern of the internal of the wire mode! in the line of its spiral into halves is then found to present a horizontally arching .. 44 A FIG. Removal of anterior to show antero-medial outwards as expanded trochanteric line. tubercle of the neck 9 wall of upper end of femur group oflamellaeextending continuation of interArrow indicates inferior and direction of intertro- chanteric disposition medial in the half their (Figs. (Benninghoff American line. antero-lateral 7 and use is strictly half 8). are and Parallel incorrect, 1925) FIG. 10 Appearance of the calcar femorale on posterior dissection. Removal of the posterior cortical shell results in partial removal of the calcar itself, and creates the illusion of a spur projecting into the femoral metaphysis. F-calcar femorale; L.T.lesser trochanter. (From M. Harty (1957): The Calcar Femorale and the Femoral Neck. Reproduced by courtesy of Dr Harty, and by permission of the Editor, Journal of Bone and Joint Surgery, since diagonally a near-vertical wires the have Haversian disposed disposition been chosen systems to the long volume.) ofthe for the orientated axis of the wires in the postero- sake ofclarity along the femur (Harris although lines of stress and Cohen 1957). Further examination shows that the third lateral group in the intertrochanteric region thickened ridge in the femoral cortex known A small area in the anterior wall of the trochanters with their communicating Ward’s triangle therefore represents in the medulla The upper femoral then appears of the VOL. and calcar NO. tissue 3, AUGUST and 1961 posterior displayed This dissection plate or spur in the neck, the posterior wall ridge are seen to be devoid a central area where trabecular anterior is usually metaphysis. as an isolated cancellous 43 B, in both femorale group of trabecu!ae which decussates is centred upon a lamellar expansion as the anterior intertrochanteric line femoral walls of the by removal results projecting neck after of the neck of specialised reinforcement with of (Fig. and the the the 9). two trabeculae. is absent neck. of the posterior cortical shell of the in partial removal of the calcar itself which into the metaphysis (Fig. 10). Removal bisection of the femur through the lesser 580 R. S. GARDEN II Bisection femorale of the femur through as the uninterrupted FIG. Serial radiographs of level of lesser trochanter to illustrate continuation of the postero-medial lesser trochanter is based. 12 the FIG. calcar femorale Figure showing 13-Oblique its view. laminar Figure true nature of calcar cortex on which the 13 structure. 14-Lateral THE FIG. Figure 12-Antero-posterior 14 view. view. JOURNAL OF BONE AND JOINT SURGERY THE trochanter, however, hardness lying AND reveals in FUNCTION the continuity calcar with OF THE as an the in different 14), displaced and to by every subcapital radiograph fracture (Fig. 15). The weight-bearing therefore the required in the obviously amount femoral be no ofthe and of the closely Brodetti combined ill packed (Figs. shaft in (1956) cortical both the for lamellae 16 and have and superior femoral 50 per 17). and neck cent inferior calcar sheet and of almost overlain is demonstrated 58! FEMUR by by serial cortical the lesser radiography the of Hirsch shown cancellous laminar cortex THE need than diaphysis. Expansion of the upper end of the femur has thus been achieved simply by a splitting-off or lamination of OF I bone metaphysis greater uninterrupted END of a the of capacity total PROXIMAL postero-media! (Fig. I I). The laminar structure degrees of rotation (Figs. 12 trochanter femur STRUCTURE I the and that the layers aspects of are each responsible of its weight-bearing capacity, and Tobin (1955) pointed out that, weight for weight, cancellous bone is as strong as cortical bone. Above the level of the lesser trochanter, therefore, compact and cancellous made a compromise-each share of time, preserving long the bones load the neck (1 900) character is partly suggested, Removal of the little the attachment radiological ofthese and whilst, at the same tubular nature of tubular skinned where of the the concealed, as by the developmental trochanteric system is seen greater both the medial and fuse and with arching lamellae VOL. each other for evenly from 43 B, NO. the the description does little the internal first time opposite 3, Au(;usT of the to clarify dissection, separated from cortex 1961 the superior in a series zone in a series Furthermore, Bigelow’s the calcar aspect of the other affects the views. neck (Fig. but mode of A double- femorale shows it to be the (Fig. 18) 2). of Gothic intertrochanteric of the diaphysis arches arch, also meeting which (Fig. system to represent by trabecular of lamellar domes place here 19). the cross-section of approach A similar and the circumferential terminate in this metaphysial lamellae refers only to their the true nature of their arching disposition. however, each epiphyses. certainly meets weight-bearing ofthe aspect traction specimen ZONE sub-epiphysial is found at the apex the entire internal by microscopic plates, of with trochanter SUB-EPIPHYSIAL of the elements The above section, and be shown fellows lateral arrangement throughout (Fig. 20). in frontal bony examination lesser merges TIlE Microscopic of the trochanteric the anatomical weight-bearing trabeculae. is much in accordance with where trochanter addition from en bloc pattern of the bulbous trochanters appearance the 15 Displaced subcapital fracture of the femur to demonstrate laminar nature of the calcar femorale. With lateral rotation of the distal fragment the calcar “disappears” and is replaced by a series of longitudinal trabeculations which are, in effect, the laminae of the calcar itself presented in 90 degrees rotation. FIG. elsewhere. This femoral Bigelow r bone have accepting a way appearance This may of widely curved tie-beams and merging with (Triepel 1922). This observation their 582 R. at once provides be explained and a geometric understood The cancellous bony plates wide structures. The then patterns or term interpretation (Fig. 21). of the which, patterns lamellae of these internal on “trabecula” becomes S. GARDEN end which misleading since by which weight-bearing section, create has this lamellae been term their system are the illusion freely used denotes therefore of narrow in describing a small beam. FIG. 16 FIG. Figure 16-Microphotograph of the medial lamellae in the internal weight-bearing mode of origin from the postero-inferior cervical cortex. The expansion of the bone the extremity of all long bones-has been achieved by a splitting-off or lamination layers of the cortex. Figure 17-The appearance of the lamellae shown in Figure with that of the ruffled leaves of a book. applied, however, to the the femoral head and has likewise been used innumerable neck (Fig. freely, of cancellous bone peculiar way to describe the twisted are visualised radiologically tie-beams 22). ought The not to be held to the femoral and expanded of the the years weight-bearing of growth lamellae epiphysial that the plate is demarcated specialised lamellae through this that this media! defined and larnellae breach the scar is not lateral the to reach so. Neither are certainly in continuity group connect to imply support formed by beam-like these cancel!ous justly of the the lamellae system,” ofisolated arrangements be regarded rather as a convenient proximal end of the femur as they SCAR plate forms femoral neck. In medial confined of the margin nor projected into may be discerned is likewise in which section. EPIPHYSIAL articular be to show their region-as at the compact be compared a barrier a young to the adult upward femur extension the site by a clearly defined epiphysial scar. It is generally the internal weight-bearing system are then continued the may It may 17 system in this of 16 can weight-bearing the existence should in the epiphysial in the and internal “ neck, but lamellae or on coronal THE During which expression behaviour lateral head, lamel!ae but careful cross the the epiphysial segment in each lamella at the to the sub-epiphysial THE of the shows scar. The of the head, but a well level of the scar (Fig. 23), zone. JOURNAL examination line of the believed upwards The OF BONE epiphysia! AND JOINT scar SURGERY of THE early STRUCTURE maturity but does becomes years seldom to arteries run bone in tunnels until, be seen. may THE (Fig. The manner the subject (1838) likened lamp bracket, be the femoral Culmann that of appearance femur in frontal section, ation compressive weight-bearing movement unyielding the trunk is base, upon for the of the to (1866) a These the tensile system. stresses They theories, of the existence in the ignore in wall- static forces strains joint pattern posture. securely and its function the lower limb street- neck presume hip femur compared of the dynamic or not neck structure has been many years. Ward a crane. the unlike the through the changing crane, femur of must with r weight form every a alter- Furthermore, anchored to as a member is far . in The junction of the calcar femorale with the inferior cortical buttress of the neck to show double-skinned appearance where the calcar, or” true neck of the femur,” has been overlain by the developmental addition of the lesser trochanter. an the movable linkage from that of a crane. of removed FIG. supporting and 19 Microphotograph of the decussation of the medial and lateral lamellae of the internal weight-bearing system in the proximal end of the femur to show the manner of their meeting in a series of Gothic arches in the subepiphysial zone of the head. 43 B, VOL. L NO. 3, 583 FEMUR OF neck and that, in the the and the bearing OF THE NECK in which to perpetually mistaken FEMORAL upon or END of laminar and these ASPECTS based the fact bracket with PROXIMAL 24). its function of both internal life distinct tunnels region, as a weight-bearing of conjecture for functions THE in the aged, its remnants The lateral epiphysial MECHANICAL THE OF throughout less sometimes scar FUNCTION persist within protective juxta-epiphysial the epiphysial not progressively advancing are AND AUGUST 1961 balancing 584 R. The the presence of compression co-existence (1948) arise point in could valga of tension the out hardly Some (Fig. exceeding that upper if tensile fernoral withstand confusion 25), and that of the forces stresses such stresses an compression neck of the universally enormous to two group normally displacing force. (Fig. is easy This Wilson hundred occur of the they may 26). to understand, Farkas, or three would by the disappearance in coxa vara when “ femur accepted. amounting slipping has been caused by their increase “ in the is not epiphysis S. GARDEN “ Hayner pounds since were the epiphysial tensile assume variation, but and “ to line !ame!lae in coxa an intensity even however, is not the result of an actual increase or decrease in the number of these lamellae, but depends upon whether they are seen in full-face or profile. In coxa valga they remain in their original position as the circumferential lamel!ae of the antero-lateral cortex where they are poorly visualised. In coxa vara they expand and rotate to present in profile as clearly defined individual structures. The numerical depends provided or Spy variation of these lamellae is therefore The tensile action of the muscles which fix the head must be resisted by an equal and opposite compressive It is difficult, therefore, to accept the presence of two other, tensile and illusory, and upon the degree of rotation in the femoral neck. Further by the fact that these so-called tensile lamel!ae are poorly men, and are completely absent in primates or quadrupeds and if the lateral lamel!ae in nature they would surely argument have been expended of the internal buckle as soon by many radiological evidence developed (Walkhoff intensity for this belief in Neanderthal 1904). is of the femur firmly in the acetabulum force in the femoral neck as a whole. tensile systems in opposition to each weight-bearing as weight bearing writers their in attempting THE JOURNAL system were indeed to be was begun. Much thought to clarify OF BONE this AND provoking JOINT SURGERY THE STRUCTURE Microphotograph separate and AND to show support OF FUNCTION the the trabecular lamellae in FIG. VOL. 43 B, NO. 3, AUGUST 1961 PROXIMAL tie-beams the femoral Microphotograph of A breach in continuity weight-bearing system THE internal neck. END or “distance weight-bearing OF THE pieces” system FEMUR which of the 23 the epiphysial scar in the proximal end of the femur. may be seen between the medial lamellae of the internal and their fellows in the epiphysial segment of the head. 585 586 R. S. GARDEN FIG. 24 Microphotograph of laminar tunnel which protects and contains the lateral epiphysial blood vessels at the junction of the epiphysial segment of the femoral head with its underlying subepiphysial zone, and which may be mistaken for the epiphysial scar. 26 lamellae of the” FIG. Figure 25-Antero-posterior Figure 26-Antero-posterior radiograph showing the absence of “tensile” radiograph showing the relative increase in intensity in coxa vara. THE JOURNAL OF BONE in coxa valga. tensile” Iamellae AND JOINT SURGERY THE problem, and an attractive stresses that compression is reversed. stresses the FUNCTION when applied and tension whether the to OF THE of Scott (1957), although Scott believes that artificial compression according tension AND the work compromise. is somewhat the and STRUCTURE PROXIMAL END OF THE in a different context, the subdivision into comes at first sight as tension and pressure “ to an elastic lamellae are bone is under substance such both subjected compression as bone.” of evidence indicates that this is mainly He suggests to alternating pressure or or not, and states that when is removed a process ofrecoil takes place and the compression-tension This, of course, is true of steel or any other elastic body subjected within the limits of its elasticity. The point at issue concerns the weight 587 FEMUR compressive in both relationship to strains and initiating force, medial and lateral patterns of the system under discussion. However this may be, the undistorted head and neck of the femur can certainly continue to function as a weight-bearing unit when decalcification has removed a!! but the medial system of !amellae. The principal thrust of weight bearing is undoubtedly directed through this almost vertical system which retains its integrity long after the lateral lamellae have been sacrificed to age or to disease. Although it would be presumptuous to oversimplify this intricate mechanical problem by denying the presence of all tensile forces in the neck of the femur, the predominance of compressive forces can safely be assumed. THE The simple mechanics lever, clinical but involve every major hip fails utterly has a most with led joint function fallacious the knee, on the tibia as the knee screws JOINT diagrammatically complexity of hip conclusions. not only the ankle function and home The of the foot. the muscles which bind pelvis, femur and tibia together purpose of supporting and balancing the trunk upon It is well established that in the final stage of medially HIP depicted the In particular, of THE usually co-ordination in the body. the are OF to indicate to many delicate muscle concerned of the this application must MECHANICS in full in the joint act of balancing muscles of the Any function, around hip joint of a and in its on the must interpretation form one hip, leg but of be intimately of the action of should thus be related to their primary the movable linkage of the lower limb. knee joint extension the femur rotates extension. This movement will also be reflected at the hip, and simple observation shows that in weight bearing the hip joint also screws home in medial rotation. Just as the neck of the femur has come to acquire a spiral conformity in the upright position, so also have the soft tissues which surround the hip joint acquired application with the plane a spiral disposition, and contraction It is well ischio-femoral and stability effort. congruity 1928). known the hip must will therefore femoral neck. joint actually movement locks in these the hip joint is locked are tightened is in this way by the ilio-femoral, or wound up by media! achieved with the utmost head as 43 B, NO. 3, fresh anatomical specimen, from which confirms Walms!ey’s (1928) observation in extension directions a rotational AUGUST and only ellipsoid, 1961 the axis with its condyles lying in a horizontal articular surface of the head, the bone will pubo-femora! rotation economy at media! rotation, and can the expense of subluxation. but it may more accurately all muscles that this be made Aeby and of the femur, of muscular It is less well known that the head of the femur is not perfectly spherical, with the acetabulum only in the functional position of weight bearing The hip joint is generally supposed to resemble the artificial ball and of the clearly imply be combined suggests that the shape of the femur has been so perfectly of ligamentous or muscular control its inherent response to in medial rotation, the rise and fall of its spiral compensating ligaments as they of the extended hip but examination been removed, femoral that about An element oftorsion to bear upon the If a femur he freely mounted on a vertical and downward pressure be applied to the rotate medially (Fig. 27). This evolved that even in the absence weight bearing is to screw home for the tilting axis of the knee. VOL. muscular of a rotatory thrust to the femur. compressive forces which are brought and lies in (Walmsley socket joint, and ligaments have allegedly universal to unlock by further (1863) described the be visualised as a hemisphere R. S. GARDEN 588 twisted it is slightly congruous stated, It out of truth articulating only in the position the hip is a screw joint. thus appears that the spirally regarded disposed as ligamentous turn and lock a with a similarly of extension and femur serves as an twisted medial independently and muscular sleeve, and mechanism which depends Experiment to illustrate the response of the femur, in the “screw home” in medial rotation when downward pressure femur to vertical conformity about the pelvis, loading by rotating of the articular hip, and 4) the femur and medially, acetabular rotation. runway with As Walmsley acting weight upon member bearing at 1) the natural 2) the locking of media! rotation rotation muscular within the hip response shape of a vertically mounted is applied on the medial aspect surfaces, 3) the restriction of medial overall control of this rotation by the which (1928) its may be of the spiral, to of its axis. by the peculiar by the interplay ligaments between tibia. SUMMARY Many analyses femur have accepted Meyer (1867), and embodies mechanical departure from and an attempt but little from the has the of the geometric arrangement and perpetuated have contributed principles which normal been norma! pattern made of skeletal to show anatomy of trabecu!ae the theories of to the belief that are foreign to bony that of the behaviour the structure long in the proximal Ward (1838), Culmann the structure of the formations elsewhere. is considered to be of the femoral end of the (1866) and femoral neck This isolated most unlikely, head and neck departs BONE AND JOiNT SURGERY bone. THE JOURNAL OF THE STRUCTURE a developmental interpretation, From in its simplest has undergone bearing system neck AND FUNCTION OF THE PROXIMAL END rotation and are likewise in nature, The rejected. spiral expansion. believed and both The cancellous to represent the crane conformity I wish to thank Dr A. A. Miller Laboratory M.S.R., and investigations and at Preston and of the spiral disposition of the soft-tissue ofhipjoint mechanics the principle Pathological 589 FEMUR point of view, the proximal end of the human femur to represent an upward continuation of the original arrangements expanded and as they are presented radiologically or on coronal section. The forces acting upon the proximal end of the femur compressive OF THE street-lamp proximal are bracket end of the his technical staff Infirmary her team of radiographers which this study has entailed. who for their at my have many femur I am so willingly has weightof the to mainly be have therefore been related been to the hip, and in the interpretation to the principle ofthe lever. courtesies disposal. internal lamellae considered theories structures that surround the ofthe screw has been preferred Royal of the rotated is believed, shaft which in placing also undertaken indebted the resources to Miss M. the innumerable of the G. 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Bergmann. 0. (1904): Das Femur des Menschen und der Anthropomorphen Wiesbaden: C. W. Kreidel. WALMSLEY, T. (1915): Observations on Certain Structural Details of the Neck and Physiology, 49, 305. WALMSLEY, T. (1928): The Articular Mechanism of the Diarthroses. Journal WARD, F. 0. (1838): Outlines of Human Osteology, p. 370. London: Henry WALKHOFF, VOL. 43 B, NO. 3, AUGUST 1961 in seiner functionellen of the Femur. Journal of Bone and Joint Renshaw. Gestaltung. of Anatomy Surgery, 10, 40.