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  • 1. HANDOUTS FOR PRACTICAL SESSIONS MODULE AN220.II 2009-2010 PART 2 PRACTICAL SESSIONS 7 AND 8: “LOWER LIMB OSTEOLOGY, GLUTEAL REGION, PELVIC GIRDLE, LUMBOSACRAL PLEXUS, MUSCULOSKELETAL ANAT. OF THIGH, KNEE, LEG AND FOOT” OBJECTIVES: INTRODUCTION: Note: In this and subsequent practical sessions please use the atlas provided to locate and identify different anatomical landmarks and relations. The practicals are mainly directed self- learning so you will not be “taught” what you need to know and identify, you will accomplish this by yourself. Contents extracted from Anatomy Notes from UCC by Prof. J.P. Fraher LOWER LIMB OSTEOLOGY 1. PELVIS The pelvis is the lower part of the trunk. It has a poorly defined boundary with the abdomen above it. Its skeleton is a major element of the lower body wall. This forms a bony ring circumscribing the lower part of the body cavity. It consists of three bones: the median sacrum dorsally and the two innominate bones laterally and anteriorly. The sacrum, has been mentioned previously in more detail when studying the vertebral column, consists of five vertebrae fused together. This has a concave surface facing the pelvic cavity. It is relatively smooth, but possesses transverse ridges where the intervertebral discs were previously located, before the sacral vertebrae fused together in development. The innominate or hip bone consists of three parts, originally three separate bones, but which fuse together during development: the ilium, the ischium and the pubis. The ilium forms the upper component and has an extensive, flattened blade for muscle attachment. Its upper margin includes the iliac crest, which stands out on the lateral body wall 76
  • 2. and marks the upper limit of the pelvis. The ischium forms the lower, posterior component. It has a prominent body, with a heavily developed lower part (the ischial tuberosity0, which transmits much of the body weight during sitting. The pubis forms the anterior component. This has a body and two rami [or branches], which are continuous with the ischium. The three bones come together at the acetabulum [see below]. The ilium articulates with the sacrum at the sacroiliac joint. This is a synovial joint between two L-shaped [auricular] surfaces, one on each bone. It has a very strong posterior ligament, which stabilises it. Stability is also enhanced by the fact that the articular surfaces are somewhat irregular. Being reciprocally curved, they fit into one another. This is advantageous in weight transmission, preventing the wedge-shaped sacrum from moving downwards and driving the two innominate bones apart. The part of the ilium between the sacroiliac joint and the acetabulum is thick and heavy, an adaptation for weight transmission between the vertebral column and the lower limb, bilaterally. The two pubic bones are apposed in the midline anteriorly, where the pubic symphysis, a secondary cartilaginous joint, intervenes between them. There is little movement between the bones forming the pelvis. What little there is, is enhanced in later pregnancy, and allows for some adaptation of the pelvis to the foetal head traversing it. 2.a Pelvic details 1. Pelvis 2.b 2.i a. Acetabulum b. Obturator foramen 2. Ilium 2.f 2.c a. Iliac crest b. Iliac fossa c. Articular surface 2.d d. Greater sciatic notch 2.f e. Lesser sciatic notch f. Anterior superior and inferior iliac spines 3.b g. Posterior superior iliac spine h. Anterior, posterior, inferior gluteal lines 1.a i. Iliac tuberosity 3. Ischium a. Ischial tuberosity 1.b 4.b 3.a 77
  • 3. 2.a b. Spine of ischium 2.i c. Ramus of ischium d. Body 2.b 4. Pubis 2.g a. Body of pubis b. Pubic tubercle 2.c c. Pubic rami d. Pubic crest e. Symphyseal surface eal 2.d 4.a 3.b 4.c 3.d 3 2.e 4.e 4.c 1.b 3.c 3.a 16 2. FEMUR 5 The femur is the thigh bone and is the longest bone in the body. The shaft makes up the greater part of its length. At its upper end lies the neck. This extends upwards and medially . 6 at an angle to the shaft and ends above in the head. This makes up approximately . two thirds of a sphere. The lower end of the femur takes part in forming the knee o joint. This consists of two femoral condyles. Each of these projects distally from the . 7 lower end of the shaft, one medial and one lateral. They are fused together anteriorly. Each condyle carries a spiral articular surface for the tibia distally. These ach surfaces are continuous anteriorly with the surface for the patella [knee cap] anteriorly, on the lower end of the shaft. There are two prominent projections for muscle attachment at its upper end: the trochanters – the greater is lateral and the lesser is below and medial. 8 Features to identify in the femur:15 15 9 1) Head 10 12 2) Neck 15 13 11 3) Greater trochanter 78
  • 4. 4) Lesser trochanter 5) Intertrochanteric line and crest 6) Gluteal tuberosity 7) Linea aspera 3 8) Popliteal surface 9) Adductor tubercle 10)Medial epicondyle 2 1 11)Medial condyle 4 12)Lateral epicondyle, 13)Lateral condyle 14)Patellar surface 15)Intercondylar fossa 16)Fovea 14 3. TIBIA The tibia is the stronger of the two bones in the leg. [The other is the fibula.] The tibia is a long bone, which has a shaft which is triangular in cross section over much of its length. The sharp anterior margin is the shin. The upper end of the bone is broadened to form a plateau. This has . two articular surfaces, a medial and a lateral, each of which lies on the upper surface of a tibial condyle. Between the surfaces is the rough intercondylar area. The lower end of the tibia is . broadened and a thick, strong projection extends downwards on the medial side of the ankle – projection the medial malleolus. Features to identify: 1. Upper end, lower end 2. Medial condyle 3. Lateral condyle 4. Intercondylar eminence – tubercles 5. Articular facet for fibula 6. Tibial tuberosity 7. Surfaces – Lateral, medial, posterior 8. Borders – Anterior (shin), interosseous, medial 9. Soleal line 79
  • 5. 10. Medial malleolus 11. Grooves for flexor hallucis longus, tibilais posterior 12. Fibular notch 80
  • 6. 4. FIBULA The fibula is a long, slender bone, lying lateral to the tibia. It articulates with the tibia below the level of the knee joint and also at its lower end, where it projects below the tibia to form the lateral malleolus. It takes only a very minor part in the formation of the knee joint: The lateral collateral ligament of the knee joint is attached to it. 81
  • 7. Features to identify: 1. Head a. Styloid process b. Articular facet 2. Neck 3. Borders – anterior, interosseous, posterior 4. Surfaces – medial, lateral, posterior 5. Medial crest 6. Lateral malleolus 7. Malleolar fossa 8. Articular surface of lateral malleolus 82
  • 8. 5. HIP JOINT The hip joint is between the head of the femur and the acetabulum. The fit is deep and so the hip joint is stable, being rarely dislocated. The acetabulum is the socket on the innominate bone for the femur and so forms the superior part of the hip joint. It is concave and has an articulating surface, which comprises a crescent-shaped strip of bone [the lunate surface], forming its superior part. Its lower, central portion is rough and non- articular, being covered by fat and synovial membrane. The lunate surface of the acetabulum and almost the entire surface of the head of the femur are covered with articular 1 cartilage. The free edge of the acetabulum is deepened by a ring of fibrous cartilage – the labrum of the acetabulum. The capsule of the joint is attached to the two bones a little beyond the margin of the acetabulum and to the lower end of the femoral neck. Much of the femoral neck is therefore within the hip joint cavity. This tends to compromise its blood supply. If the neck is fractured, the viability of the head of the femur is threatened because the blood vessels to the head may be interrupted. If this is cut off, the head may die – avascular necrosis [necrosis = death] – if the supply through the delicate ligament of the head of the femur (1) is inadequate. The capsule is strengthened by three major ligaments - the iliofemoral (2), ischiofemoral(3) and pubofemoral (4), from the corresponding part of the innominate bone to the femoral neck and the bone just distal to it. The first of these is particularly strong and protects the joint against over-extension. 83
  • 9. Anterior View: Posterior View: 2 4 3 2 The hip joint has three degrees of freedom of movement. It possesses flexion and extension in the parasagittal plane, abduction and adduction in the coronal plane, and rotation can take place around longitudinal axes. Flexion is produced by the iliopsoas muscle and the rectus femoris part of the quadriceps femoris muscle; Extension is produced by the gluteus maximus and hamstring muscles; Adduction is produced by the adductor muscles; Abduction is produced by the gluteus medius and minimus, as well as the tensor fasciae latae. Abduction is important is setting up the conditions for other movements, particularly flexion and extension. Because the two feet are on the ground while standing, the pelvis must tilt up to 84
  • 10. lift the lower limb and therefore the foot off the ground to facilitate the forward swing in walking. Accordingly, the abductors on the left side are active in enabling the forward swing of the right lower limb. Despite being stable, the hip joint may be dislocated when strong forces are exerted in particular directions. This frequently happens in car accidents. The force may be great enough to fracture the head of the femur, a factor in causing osteoarthritis. The acetabulum may not develop to be as deep as normal, when congenital dislocation of the hip may result. The articular cartilage on the surfaces is initially over 0.5cm thick, but is eroded during life and so becomes progressively thinner with time. The result of this ageing process is osteoarthritis, when the underlying bone is exposed and this is associated with pain. 6. KNEE JOINT The articular surfaces on the tibial condyles articulate with the corresponding surfaces on the two condyles of the femur. Each is covered by a layer of articular cartilage. The capsule connects the bones all around the perimeter of the joint. This is complicated in several ways, however: For example, the broad tendon of the quadriceps femoris fuses with it superiorly. Also, there is an opening in it posteriorly through which the tendon of the popliteus muscle emerges from the point cavity. This arises within the joint from the lateral femoral condyle and is attached to the upper end of the tibia. [For its function, see below.] The degree of congruity between the femur and tibia is low. The concave tibial surfaces are much less curved than the spiral surfaces of the femur. Accordingly, the knee joint has complex mechanisms for stabilisation. It has several strong ligaments: Being a hinge joint, it has two collateral ligaments, one on its medial and one on its lateral side. These prevent abduction and adduction, respectively. Within the joint are two cruciate ligaments, connecting the bones, lying in approximately parasagittal planes and crossing one another. These are attached to the intercondylar area of the tibia and to the femoral condyles. They bind the bones together, forcing them towards one another in the several positions which the joint may adopt. 85
  • 11. Congruity of the articulating Posterior View surfaces is enhanced by the presence of two menisci. Each of . these projects into the joint cavity from the capsule around most of its perimeter. They are attached at their anterior and posterior ends to the tibia. They have the advantage of being flexible and of adapting their form to the varying [spiral] outline of the femoral condyles. Because of this spiral profile, the congruity of the knee joint surfaces varies considerably at differing stages of flexion – extension. Anterior View 86
  • 12. The patella glides up and down on the groove on the patellar surface on the lower end of the femoral shaft. Both surfaces are covered with hyaline cartilage. The lower end of the patella is connected to the tibial tuberosity on the anterior surface of the upper end of the shaft, by the patellar tendon. This is the true insertion of the quadriceps femoris. This muscle is attached to the upper end of the patella, which is therefore a sesamoid bone in its tendon. The knee joint has two degrees of freedom of movement. The principal movements are flexion and extension. It also undergoes rotation – thus the tibia can be rotated voluntarily on the femur - especially evident when the joint is flexed through 90º. During walking, towards the end of extension of the femur on the tibia, the femur rotates medially, thus locking the joint by bringing it into the close packed position. On commencing the next stage of the walking cycle, the joint is unlocked – by the action of the popliteus muscle. Muscles producing extension: the powerful quadriceps [femoris]; sartorius, especially when combined flexion of hip and knee take place; flexion: the hamstrings: biceps femoris, semimembranosus, semitendinosus. 87
  • 13. The collateral ligaments may be injured in impacts on the joint from the sides, such as from automobiles; or in accidents such as skiing injuries which entail powerful laterally or medially directed forces acting on the joint. MUSCLES AND MOVEMENTS OF THE LOWER LIMB Unlike that of the upper limb, the lower limb girdle is part of the body wall. Thus, the bone of the proximal segment of the lower limb, the femur, articulates directly with the trunk skeleton. MUSCLES AND MOVEMENTS OF THE THIGH 1) Anterior Muscles a) Sartorius This long strap muscle runs from the anterior superior iliac spine to the upper part of the medial surface of the tibia. It runs in front of the hip joint and behind the axis of the knee joint, therefore it flexes both hip and knee. It is supplied by the femoral nerve. b) Quadriceps Femoris This composite muscle consists of four parts. Of these, the most anterior, the rectus femoris, arises from the hip bone and passes in front of the hip joint. The other three parts of the muscle, the vastus lateralis, the vastus medialis and the vastus intermedius arise from the posterolateral, posteromedial and anterior aspects of the shaft of the femur, respectively. All four are inserted into the upper, anterior part of the shaft of the tibia through a common tendon, and thence to the patella. The patella is in turn attached to the tibia through the ligamentum patellae. The patella is therefore a sesamoid bone in the quadriceps tendon. The quadriceps is supplied by the femoral nerve. All four parts of the muscle extend the knee. Since the rectus, in addition, passes in front of the hip joint, it flexes this joint. 88
  • 14. c) Ilipsoas This composite muscle is in two parts; the psoas major and the iliacus. The psoas arises from the lumbar part of the vertebral column. It runs caudally and laterally along the brim of the lesser pelvis. Here it is joined on its lateral side by the fibres of the iliacus coming from the iliac fossa. The composite muscle then runs into the thigh behind the inguinal ligament. It is attached to the lesser trochanter of the femur. The composite muscle flexes the hip joint. 89
  • 15. Acting from their lower attachments, both iliopsoas muscles bend the lumbar part of the vertebral column forwards (as in sitting up from the supine position). The psoas, acting on its own, flexes the lumbar spine laterally. The lumbar plexus lies in the substance of the psoas major. It supplies this muscle as well as the iliacus. 2) Muscles of the Buttock a) Gluteus Maximus This powerful muscle arises from the dorsal aspects of the sacrum, sacrotuberous ligament and ilium. Its fibres run downwards and laterally. It is inserted into the gluteal tuberosity of the femur. It is also inserted beyond this into the tibia and the head of the fibula via the iliotibial tract of the fascia lata, a very thick and powerful sheet of deep fascia. It is supplied by the inferior gluteal nerve from the sacral plexus. It extends and laterally rotates the thigh at the hip joint. Thus, it swings the lower limb backwards when the foot is off the ground. When the foot is on the ground it extends the trunk on the lower limb, as in standing up from the sitting position or in climbing stairs. It is also important in stabilising the knee joint. 90
  • 16. b) Tensor Fasciae Latae This muscle arises from the iliac crest and is inserted into the iliotibial tract. It is supplied by the superior gluteal nerve. It abducts the hip joint and stabilises the knee joint. c) Gluteus Medius and Minimus These muscles lie deep to the gluteus maximus. They arise from the ilium. They run laterally above the hip joint to be attached to the greater trochanter of the femur. They are supplied by the superior gluteal nerve. Both abduct the hip. They are especially important in walking. While the more mobile limb is raised from the ground and is being swung forwards, the gluteus medius and minimus on the opposite side are active, thus preventing the pelvis from sagging on the side of the unsupported mobile limb. If they are paralysed it sags: Trendelenburg’s sign. d) Small Muscles Like the shoulder joint, the hip joint possesses a cuff of short muscles surrounding it, running from the pelvis to the femur. These function primarily as ligaments of variable length and tension, stabilising the hip during the powerful movements brought about by the much stronger muscles crossing the joint. These include: 91
  • 17. 1. Piriformis runs laterally behind the hip joint from the sacrum to the greater trochanter. It is supplied from the sacral plexus. 2. Obturator Externus and Internus come from the outer and inner surfaces, respectively, of the obturator membrane. The internus runs backwards to emerge from the pelvis through the lesser sciatic foramen and run laterally behind the joint. The externus spirals backwards and laterally around the neck of the femur. Both are attached to the greater trochanter. The externus is supplied by the obturator nerve, the internus from the sacral plexus. 3. The rectangular Quadratus Femoris muscle runs laterally behind the hip joint from the ischial tuberosity to the upper part of the shaft of the femur. It is supplied from the sacral plexus. e) Adductor Group The adductor muscles run from the pubis and ischium downwards and laterally to the linea aspera on the back of the shaft of the femur. There are three main adductors. Their nerve of supply is the obturator. 1. The adductor magnus is the largest of the group. It is attached to the whole length of the linea aspera and the medial supracondylar line. It separates the anterior from the posterior compartments of the thigh. The part which arises most posteriorly (i.e. from the ischial tuberosity) is morphologically part of the hamstring (extensor) muscle group. The lower attachment of this part is to the medial femoral condyle. The adductor magnus is supplied by two nerves: the adductor part by the obturator, the hamstring part by the sciatic. The femoral artery passes backwards from the anterior compartment of the thigh into the popliteal fossa by passing through an opening bounded by the femur and the two parts of the adductor magnus. 2. The Adductor Brevis arises from the pubis and is attached to the upper part of the linea aspera. It lies immediately in front of the adductor magnus. 92
  • 18. 3. The Adductor Longus arises from the pubis and is attached to the linea aspera behind and somewhat lower down than the brevis. All three adductors flex the femur from the extended position and also adduct it. They are therefore very important in kicking movements. 4. The Gracilis runs from the pubis to the upper part of the medial surface of the tibia. Supplied by the obturator nerve, it adducts the thigh, flexes the knee joint and, especially when the knee is flexed, rotates the tibia medially on the femur. 5. The Pectineus is a small muscle and arises from the superior ramus of the pubis. It passes downwards to the shaft of the femur behind the lesser trochanter. It is usually supplied by the femoral nerve. It adducts and flexes the femur. The femoral sheath and canal The femoral sheath is a tapering cone of fascia which extends along the femoral vessels. It is continuous with the fasciae lining the abdominal wall (transversalis and iliolumbar fasciae). Traced distally, it tapers and blends with the perivascular tissue surrounding the femoral vessels. The fascial cone is larger than the vessels so that a redundant space is left medial to them. This is the femoral canal, which is about 2 cm long. Its proximal opening, the femoral ring, is bounded medially by the lacunar ligament, anteriorly by the inguinal ligament, posteriorly by the pectineus muscle and laterally by the femoral vein. The femoral canal contains loose connective tissue and, commonly, a lymph node. Femoral Hernia In femoral hernia, the hernial sac protrudes down through the femoral canal, then forwards through the relatively weak cribriform fascia which closes the semilunar hiatus in the upper anteromedial part of the fascia lata. It then projects forwards below and lateral to the pubic tubercle. This helps to distinguish it from inguinal herniae. However, as it enlarges further it tends to project upwards and medially towards the pubic tubercle. 93
  • 19. Femoral herniae are commoner in females than in males because females have relatively large femoral canals, due to greater breadth of the pelvis and the smaller size of the femoral vessels. Femoral herniae tend to become obstructed and to strangulate more readily than inguinal because of the smallness and relative rigidity of the femoral ring. The Femoral Triangle and Adductor Canal The femoral triangle is bounded laterally by the sartorius, above by the inguinal ligament and medially by the medial border of the adductor longus. On the muscles of the femoral triangle lie the femoral artery, vein and nerve. The femoral artery leaves the lower part of the triangle through the adductor canal. This canal is bounded anterolaterally by the vastus medialis, posteromedially by the adductor longus and magnus and anteriorly by the sartorius. The artery then leaves the front of the thigh and the adductor canal by passing backwards through the opening in the adductor magnus. Once it has passed through this opening it is called the popliteal artery. f) Hamstring Group Each of the three hamstring muscles is attached above to the ischial tuberosity, runs distally along the back of the thigh and passes behind the knee joint to be attached to one of the bones of the leg. The lateral hamstring is the biceps femoris. This muscle has an additional head arising from the back of the femur. It is attached to the head of the fibula. The two remaining hamstrings lie medially. Of these, the semitendinosus is superficial and the semimembranosus is deep. Both are attached to the tibia, the semitendinosus is superficial and semimembranosus deep. Both are attached to the tibia, the semimembranosus to the back of the medial tibial condyle, the semitendinosus to the upper medial part of the shaft close to the attachments of sartorius and gracilis. All three hamstrings are supplied by the sciatic nerve. Since all three cross both hip and knee joints posteriorly, they have a combined action; they extend the hip and flex the knee. (The femoral head of the biceps acts only on the knee). Using 94
  • 20. the lower attachments as the origin, the hamstrings extend the trunk on the femur, as in straightening up from the bent position. They also rotate the leg at the knee especially when the joint is flexed. The biceps rotates it laterally, the other two rotate it medially. MUSCLES AND MOVEMENTS OF THE LEG AND FOOT The muscles of the leg lie in three compartments – anterior, posterior and peroneal (lateral). Muscles of the Anterior Compartment Each of these muscles passes distally into the dorsum of the foot by passing deep to the extensor retinacula. The upper extensor retinaculum runs from the tibia to the fibula just above the ankle, the lower from the calcaneus to the medial malleolus and the fascia on the medial side of the foot. As they pass deep to these retinacula, the tendons are contained in synovial sheaths. Each of these muscles is supplied by the deep peroneal nerve. 1. The Tibialis Anterior arises from the upper part of the tibia and is inserted into the medial cuneiform and first metatarsal bones. It dorsiflexes the ankle joint and inverts the foot. 2. The Extensor Digitorum Longus arises from the fibula. It divides into four tendons, one to each of the lateral four toes. The attachment of these is exactly similar to that of the corresponding muscle is the hand (q.v.). This muscle dorsiflexes the ankle and extends the lateral four toes at the metatarsophalangeal joints. 3. The Extensor Hallucis Longus arises deep to the previous two, from the fibula. It is inserted into the dorsal surface of the distal phalanx of the great toe. It dorsiflexes the ankle and extends the great toe. Acting from below, all of the three above muscles prevent the body from overbalancing backwards at the ankle joint. 95
  • 21. 4. Peroneal Muscles The peroneus longus and brevis arise from the lateral aspect of the fibula. They run distally behind the lateral malleolus, being bound down by retinacula attached to the lateral malleolus and the lateral side of the calcaneus. The brevis is attached to the base of the fifth metatarsal. 96
  • 22. The longus hooks medially around the cuboid bone and runs across the plantar surface of the foot to be inserted into the medial cuneiform and first metatarsal bones. Both muscles lie in a synovial sheath as they pass behind the lateral malleolus. The longus lies in a synovial sheath as it crosses the sole of the foot. Where it bends around the cuboid, it contains a sesamoid fibrocartilage or bone. Both peronei are supplied by the superficial peroneal nerve. Both evert the foot and help to prevent medial overbalancing. They help to maintain the arched form of the foot. Muscles of the Posterior Compartment 1. Gastrocnemius. Each of the two bellies of the gastrocnemius arises from the posterior part of the corresponding condyle of the femur and from the capsule of the knee joint. Both are attached through a common tendon, the tendo calcaneus, to the posterior surface of the calcaneus. The gastrocnemius is supplied by the tibial nerve. It flexes the knee joint and powerfully plantarflexes the ankle. It is of major importance in providing propelling force in walking and running. In fracture of the shaft of the femur it pulls the lower fragment backwards out of alignment with the upper fragment. 2. The Soleus arises from the upper parts of the tibia and fibula and from a tendinous arch between the bones. It is attached to the deep surface of the tendo calcaneus. It is supplied by the tibial nerve. It plantar flexes the ankle joint. The soleus mainly functions as a postural 97
  • 23. muscle, preventing the body from falling forwards at the ankle during upright standing. (A vertical line through the centre of gravity of the body passes in front of the ankle joint). 3. The Popliteus arises from the lateral surface of the lateral femoral condyle within the knee joint capsule. Its fibres emerge from the joint to be inserted into the upper part of the dorsal surface of the tibia. It is supplied by the tibial nerve. It rotates the femur laterally on the tibia when the foot is on the ground. When the knee is fully extended and bearing weight, the femur is in a position of medial rotation on the tibia, the joint being locked and close-packed. In the first stage of flexion, the popliteus undoes the rotation of the femur by laterally rotating it on the tibia. 4. The Flexor Digitorum Longus lies deep to the soleus. It arises from the tibia. Its tendon enters the foot by passing behind the medial malleolus. It then divides into four digitations which are inserted into the distal phalanges of each of the four lateral toes, in a manner exactly similar to those of the flexor digitorum profundus in the hand. The four digitations run obliquely distally and laterally through the foot. When the muscle contracts, the line of pull, which would be oblique, is rendered longitudinal by the action of a short muscle of the foot. This is the flexor accessorius which run from the calcaneus to each of the digitations of the long muscle, so as to make its line of pull parallel to the long axis of the foot. The longus is supplied from the tibial nerve. It flexes all the joints of the lateral four toes, helping them to grip the ground firmly. It also plantar flexes the ankle. Acting from below it prevents forward overbalancing. 5. The Flexor Hallucis Longus also lies deep to the soleus. It arises from the fibula. It enters the foot behind the medial malleolus and is inserted into the plantar surface of the distal phalanx of the great toe. It is supplied by the tibial nerve. It flexes all the joints of the great toe and also the ankle joint. 98
  • 24. 6. The Tibialis Posterior is the deepest muscle of the leg. It arises from the tibia, the fibula and the interosseous membrane between them. Its tendon enters the foot behind the medial malleolus. It is inserted into most of the tarsal bones. It is supplied by the tibial nerve. It plantar flexes the ankle joint and inverts the foot. Acting from its lower attachment, it prevents lateral overbalancing. The tendons of the three previous muscles are each surrounded by a synovial sheath and pass through an osseofibrous tunnel as they enter the foot. This tunnel lies deep to the flexor retinaculum which runs between the medial malleolus and the calcaneus. 99
  • 25. 100
  • 26. Intrinsic Muscles of the Foot The Extensor Digitorum Brevis muscle forms the fleshy mass on the dorsum of the foot. It arises from the calcaneus. It has four digitations, each of which fuses with a tendon of the long extensor of the medial four toes. It is supplied by the deep peroneal nerve. The remaining intrinsic muscles lie on the plantar aspect of the foot. Their main importance lies in their mass action during walking; fine control of individual toes is of little importance, though it can be learned. A further important function of the intrinsic muscles is to support the arches of the foot. In this function, they aid the ligaments, the plantar aponeurosis and the long muscles which run on the undersurface of the skeleton. Those intrinsic muscles of the foot which lie on its plantar aspect are arranged in four layers. First Layer (superficial or plantar) 1. The Abductor Hallucis runs from the calcaneus to the base of the proximal phalanx of the great toe, which it helps to flex at the metatarsophalangeal joint. 2. The Flexor Digitorum Brevis corresponds to the flexor digitorum superficialis in the upper limb. It arises from the plantar aspect of the calcaneus. It gives rise to four tendons, through which the tendons of the flexor digitorum longus pass. Each of its tendons is attached to the middle phalanx of one of the lateral four toes. It flexes the proximal interphalangeal and metatarsophalangeal joints. 3. The Abductor Digiti Minimi runs from the calcaneus to the proximal phalanx of the little toe. It helps to flex the metatarsophalangeal joint. Second Layer 1. The Flexor Accessorius (see above) 101
  • 27. 2. The four Lumbrical muscles correspond to those in the hand. Third Layer This consists of three muscles, the short flexors of the great and little toes, and the adductor of the great toe. Each of these arises from the plantar aspect of the tarsus and/or metatarsus. Each is inserted into the proximal phalanx of the appropriate toe. The movement brought about by each is that indicated by its name. Fourth Layer (deepest) This consists of the Interossei, which are similar to the corresponding muscles in the hand in their attachments and actions. However, the imaginary line in relation to which they move the toes passes through the second toe. Thus the longitudinal axis of the foot differs from that of the hand in that it passes through the second, not the third, digit. Nerve supply All of the intrinsic muscles on the plantar aspect of the foot are supplied by the lateral plantar nerve, except the following: abductor hallucis, flexor hallucis brevis, flexor digitorum brevis and the first (most medial) lumbrical. These are supplied by the medial plantar nerve. NERVES OF THE LOWER LIMB Lumbosacral Plexus The lumbosacral plexus is made up by ventral rami. It supplies the muscles of the lower limb. The upper lumbar nerves also supply part of the trunk and the lower sacral and coccygeal nerves also supply the perineum. The plexus is derived from the five lumbar, five sacral and 102
  • 28. first coccygeal nerves. The lumbar plexus lies in the substance of the psoas major muscle and the branches emerge from this. The sacral plexus lies on the dorsal wall of the pelvis. Each of the ventral rami contributing to the plexuses receives a grey ramus communicans from the sympathetic chain. Through these, autonomic fibres are distributed to the tissues of the lower limb. Each of the first two lumbar ventral rami sends a white ramus communicans to the sympathetic trunk. The ventral rami of S2 and 3 send fine branches to the autonomic plexuses in the pelvis. These are preganglionic parasympathetic fibres which are concerned in the innervation of the pelvic viscera and part of the colon. Lumbar Plexus 1. Iliohypogastric and Ilioinguinal nerves run laterally anterior to the quadratus lumborum and pierce the transversus abdominis to run forwards in the abdominal wall between this muscle and the internal oblique. They give cutaneous supply to a strip of skin running above the inguinal ligament, the upper medial part of the thigh, the scrotum and the penis or labium majus. 2. The Genitofemoral nerve emerges onto the anterior surface of the psoas, descends along it and supplies the scrotum or labium majus and the upper medial part of the thigh. 3. The Lateral Cutaneous Nerve of Thigh runs laterally on the iliacus and enters the thigh by passing behind the lateral part of the inguinal ligament. It supplies the skin on the lateral aspect of the thigh. 4. The Obturator Nerve is the nerve to the adductor group of muscles. It emerges from the medial border of the psoas, runs forwards along the lateral wall of the lesser pelvis and enters the thigh through the obturator canal. Here it divides into two branches, anterior and posterior, which run downwards in planes anterior and posterior to the adductor brevis. In 103
  • 29. addition to supplying the adductor longus, brevis and part of the adductor magnus, the it supplies the obturator externus and the gracilis. It is sensory to both hip and knee joints. This supply to both joints may result in referred pain from hip disease being misdirected to the knee, giving the patient a false impression of knee disease. The opposite can also occur. 5. The Femoral Nerve supplies the muscles of the front of the thigh, the pectineus, the sartorius and the quadriceps. It also supplies sensory branches to the hip and knee joints and to the skin on the anteromedial surface of the lower limb as far as the medial side of the foot. It emerges from the lateral aspect of the psoas major and runs into the thigh in the grove between the psoas and iliacus. Its sensory branches supply the area of skin already mentioned. One of these, the saphenous nerve, runs downwards through the femoral triangle and adductor canal with the femoral vessels. It becomes superficial in the leg by emerging between the sartorius and gracilis. It then descends on the medial side of the leg where it accompanies the great saphenous vein. This nerve supplies the skin on the front and medial side of the leg and on part of the medial aspect of the foot. 6. Motor branches from the plexus supply the psoas and iliacus muscles. 7. The lumbosacral trunk consists of part of L4 together with L5. The former emerges from the medial aspect of the psoas major and joins the latter. The combined trunk descends into the pelvis to join the sacral plexus. Sacral Plexus 104
  • 30. The ventral rami contributing to the plexus converge to form a large fan-shaped band. This descends on the posterior pelvic wall to emerge from the pelvis into the back of the thigh through the greater sciatic foramen, below the piriformis, as the sciatic nerve. A large number of small nerves arise from the plexus and supply the muscles of the perineum, together with those around the hip joint. Thus they supply the obturator internus, the piriformis and the quadratus femoris. The gluteal nerves, superior and inferior, leave the pelvis above and below the piriformis respectively. They enter the gluteal region to supply the three gluteal muscles and the tensor fasciae latae. Branches from the plexus supply the coccygeus and levator ani muscles. 1. The pudendal nerve is the principal nerve of the perineum. It leaves the pelvis through the lower part of the greater sciatic foramen, descends on the superficial aspect of the sacrospinous ligament and runs forwards into the perineum, together with its accompanying vessels. It runs forwards on the obturator internus muscle, above the level of the ischiopubic rami. Here is lies in the pudendal canal which is bounded by fascia. In this position it may be readily anaesthetised, a procedure termed pudendal block, which is frequently performed during childbirth. Through its inferior rectal branch, the pudendal nerve supplies the sphincter ani externus, part of the levator ani, the skin of the anal canal and that surrounding the anus. Other branches of the pudendal nerve supply the muscles of the urogenital triangle of the perineum, the skin of the scrotum or labium majus, the skin of the penis or clitoris and the erectile tissue of both male and female external genitals. 2. The posterior cutaneous nerve of the thigh arises from the sacral plexus, leaves with the sciatic nerve and descends along the back of the thigh and popliteal fossa. It runs down to supply the skin over the back of the thigh, the popliteal fossa and the upper half of the back of the leg. It also supplies the skin of the perineum and the lower part of the buttock. 105
  • 31. 3. The Sciatic Nerve is the largest nerve in the body. It consists of a medial tibial nerve and a lateral common peroneal nerve bound together. It enters the thigh from under the lower border of the piriformis. It runs downwards on the posterior surface of the short muscles of the hip joint and then on the adductor magnus. It lies deep to the gluteus maximus and the hamstrings. In the thigh, it supplies the latter group of muscles and ends by dividing into tibial and common peroneal branches. This division is usually at the uppermost part of the popliteal fossa, but may occur at a much higher level. 4. The Common Peroneal Nerve nerve is distributed to the skin of the anterolateral surface of the leg and of the dorsum of the foot, as well as to the muscles of the anterior and peroneal compartments of the leg and the extensor digitorum brevis. It also gives sensory supply to the knee, ankle and foot joints. It runs downwards and laterally under the biceps femoris as far as the head of the fibula. It divides into deep and superficial peroneal nerves as it winds round the lateral surface of the neck of the fibula under cover of the peroneus longus. As it lies on the neck of the fibula, it can be rolled against the bone. In this situation it is vulnerable to injury. The deep peroneal nerve runs downwards and medially on the fibula under the extensor digitorum longus to reach the interosseous membrane. Here it is joined by the anterior tibial artery and veins. 106