The Lower Extremity

Chapter 5 The Lower Extremity



I. Skeleton of Lower Extremity

A. Pelvic Girdle

1. Overview


a. Transmits weight of upper body from axial skeleton to lower extremities

b. Fusion of pubis, ilium, and ischium at acetabulum to form coxal or hip bone

c. Joins sacrum and coccyx to form bony pelvis

2. Pubis


a. Body articulates with opposite pubic bone at pubic symphysis

b. Superior ramus articulates laterally with ilium and ischium at acetabulum

c. Inferior ramus fuses posteroinferiorly with ramus of ischium

3. Ilium


a. Body forms superior portion of acetabulum

b. Wing (ala) gives origin to gluteal and iliacus muscles and articulates with sacrum


Because of its subcutaneous location, the iliac crest is particularly susceptible to injury in contact sports. A hip pointer is a contusion of the iliac crest usually caused by a direct blow or a fall on the hip.



A hip pointer is a contusion of the iliac crest.


4. Ischium


a. Ischial tuberosity gives origin to hamstring muscles and provides attachment for the sacrotuberous ligament.

b. Ischial spine provides attachment for the sacrospinous ligament.


The origin of the hamstrings may be avulsed from the ischial tuberosity in skeletally immature athletes. When sitting, the ischial tuberosity is not covered by the gluteus maximus muscle; therefore, one sits on the ischial tuberosities, not the gluteus maximus. Repetitive movement against a bicycle seat may inflame the ischial bursa (ischial bursitis), which covers the ischial tuberosity. In debilitated or sensory-impaired individuals (e.g., spinal cord injury patients), compression and ischemia in skin and subcutaneous tissues overlying the ischial tuberosities caused by unrelieved sitting or lying down in one position may result in pressure sores, or decubitus ulcers.



The hamstring origin from the ischial tuberosity is often avulsed before skeletal maturity.


Pressure ulcers may develop over ischial tuberosities from unrelieved pressure.


5. Acetabulum


a. Cup-shaped depression that articulates with head of femur to form hip joint

b. Articular lunate surface around central nonarticular acetabular fossa

c. Margin is deficient inferiorly, forming the acetabular notch.

B. Femur (Figure 5-1)

image

5-1 Anteroposterior radiograph of the right hip.



The main blood supply to the femoral head in adults is the medial femoral circumflex artery.


1. Head


a. Articulates with acetabulum

b. Covered by hyaline cartilage except at fovea capitis for attachment of ligament of the head


Traumatic injury or systemic conditions such as sickle cell disease may cause avascular necrosis of bone. In children, the avascular necrosis is often idiopathic and involves epiphyseal ossification centers (osteochondrosis) of the lower extremity. The most common and serious example is osteochondrosis of the femoral head (Legg-Calvé-Perthes disease). The condition is painful and causes an antalgic (protective) limp but usually is self-limiting and may heal completely. Pain may be felt in the hip or referred to the knee. In adults, osteonecrosis of the femoral head is a form of avascular necrosis frequently seen in alcoholics or following long-term use of corticosteroids. The adult form doesn’t heal spontaneously, and severe pain may accompany collapse of the femoral head.



Legg-Calvé-Perthes disease is idiopathic avascular necrosis of a child’s femoral head.



Fractures involving the epiphyseal plate may cause growth disturbance (e.g., causing a discrepancy in leg length) and/or bony deformity. Prognosis is based on the relationship of the fracture line to the epiphyseal plate (Salter-Harris classification).


2. Neck



• Typically forms angle of inclination of about 125° with shaft


A common fracture in elderly women with osteoporosis is the fracture of the femoral neck. Femoral neck fractures in younger individuals are usually due to high-energy trauma but can be stress fractures from unaccustomed strenuous activity (e.g., in military recruits). The angle of inclination is decreased in coxa vara (e.g., femoral neck fracture) and increased in coxa valga (e.g., developmental dysplasia of the hip) (Figure 5-2). Both may congenital or acquired conditions.


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5-2 Angle of inclination is formed by line drawn longitudinally through center of femoral shaft and line bisecting femoral head and neck. Angle is decreased in coxa vara and increased in coxa valga.


(From Chung, S M K: Hip Disorders in Infants and Children. Philadelphia, Lea & Febiger, 1981, p 85.)


3. Junction of neck and shaft


a. Greater trochanter

• Insertions for hip abductors and rotators

b. Lesser trochanter

• Insertion for iliopsoas muscle


A fall or direct blow can easily fracture the greater trochanter because it is relatively superficial, being covered only by skin, fascia, and tendinous fibers of the gluteus maximus. Trochanteric bursitis, which affects the bursa separating the greater trochanter from the gluteus maximus at its insertion into the iliotibial tract, causes tenderness over the greater trochanter and pain that may radiate along the iliotibial tract to the tibia. It is a type of friction bursitis that frequently follows episodes of repeatedly carrying heavy objects up stairs or a steep incline.


The lesser trochanter is unlikely to fracture after a fall or direct blow because it is well protected by muscles. In contrast, avulsion fractures of the lesser trochanter from the pull of the iliopsoas are common in adolescents. Lesser trochanteric avulsions may occur in adults due to metastatic or, less commonly, primary carcinoma.



Traumatic lesser trochanter avulsion in adults requires screening for metastatic carcinoma.


4. Linea aspera



• Prominent longitudinal ridge on posterior surface of shaft for attachment of thigh muscles and intermuscular septa

5. Medial and lateral condyles


a. Covered on articular surface by hyaline cartilage for articulation with tibial condyles at knee joint

b. Have roughened convex prominences called medial and lateral epicondyles, respectively

6. Popliteal surface



• Floor of popliteal fossa, against which popliteal artery lies


Although less common than those of the clavicle or humerus, birth fractures of the femur may occur during the difficult delivery of a large infant, especially during a breech presentation. Multiple birth fractures, including the femur, usually occur in osteogenesis imperfecta (brittle bone disease) caused by mutations of type I collagen genes. Patients often also have a blue sclera (reflection of underlying choroidal veins) and develop deafness. Type II osteogenesis imperfecta is fatal in the prenatal or early postnatal period. Transmission is autosomal dominant.



Osteogenesis imperfecta is a defect in type I collagen synthesis resulting in multiple fractures.



Fracture of the femoral shaft causes substantial shortening of the femur from contraction of the powerful longitudinally oriented muscles (Figure 5-3, A).


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5-3 Femoral fractures. A, Proximal fragment is flexed by the iliopsoas and abducted by the gluteus medius and minimus muscles; adductor muscles pull the distal fragment proximally and medially. B, In supracondylar fracture, the gastrocnemius muscle can rotate the distal fragment posteriorly, damaging the popliteal artery. Arrows, direction of force.



When a long bone fractures, fatal fat emboli may travel to the lungs and/or brain.


C. Patella

1. Sesamoid bone in quadriceps femoris tendon

2. Covered by hyaline cartilage on its posterior surface for articulation with patellar surface of femur


A patellar fracture from a direct blow often leaves small undisplaced fragments. Transverse fractures caused by sudden quadriceps contraction usually result in the fragments being pulled apart. The articular cartilage on the patella is frequently the initial site of degenerative joint disease (osteoarthritis) of the knee. It involves softening (malacia), fissuring, and uneven erosion of the cartilage (chondromalacia patellae) with retropatellar pain that is worse walking up or down stairs and running. Patellectomy may be required if conservative treatment fails.



The patellar articular cartilage is often the initial site of knee osteoarthritis.


D. Tibia

1. Overview


The tibia is the medial weight-bearing bone of the leg, and the fibula is the lateral non-weight-bearing bone.


The tibia helps to form the knee and ankle joints, and the fibula helps to form the ankle but not the knee joint.



a. Medial weight-bearing bone of leg

b. Articulates with femur at knee joint, with talus at ankle joint, and with head and distal end of fibula at superior and inferior tibiofibular joints

2. Medial and lateral tibial condyles


a. Form expanded proximal end of tibia, each with slightly concave superior articular surface for corresponding femoral condyle

b. Separated by anterior intercondylar area, intercondylar eminence, and posterior intercondylar area

3. Tibial tuberosity



• Attachment of quadriceps femoris tendon (patellar ligament)

4. Shaft



• Thinnest and most likely to fracture at junction of middle and inferior thirds


Osgood-Schlatter disease is the partial avulsion of the tibial tuberosity from the epiphyseal plate at the insertion of the patellar tendon. The resulting inflammation (apophysitis), knee pain, and enlargement of the tibial tubercle are frequent in male athletes 11-15 years of age. Alternatively, the tibial tubercle may be completely avulsed by forceful quadriceps contraction before closure of the epiphyseal plate.



Osgood-Schlatter disease is adolescent knee pain and tibial tubercle enlargement (“knobby knees”) from partial avulsion.



Tibial shaft fractures are frequent and are often open (compound fractures) because of the tibia’s extensive subcutaneous surface. Infection of the bone (osteomyelitis) is a serious complication. In adults, delayed union and nonunion are common in severely displaced fractures.



Tibial shaft fractures often compound fractures and result in osteomyelitis.



If inflammation or bleeding causes increased pressure within an osseofibrous compartment of the leg (compartment syndrome), a fasciotomy can prevent necrosis from ischemia of the muscles (Volkmann ischemic contracture) and nerves (see clinical correlation under VI.C.1. following).


Anterior or medial leg pain (shin splints) is frequent in athletes who run on hard surfaces. The condition is probably a stress reaction of the tibial periosteum (or perhaps muscle attachments) to repetitive use. Shin splints must be distinguished from stress (fatigue) fractures of the tibia resulting from sudden increases in strenuous activity (e.g., daily marching in previously sedentary military recruits). These microscopic cracks in bone usually are not apparent in initial radiographs. Stress fractures can progress to complete fractures if overuse continues.



Tibial shaft fractures frequently cause compartment syndrome.


5. Medial malleolus


a. Subcutaneous prominence at medial side of ankle

b. Proximal attachment of medial (deltoid) ligament of ankle

E. Fibula

1. Overview


a. Lateral non-weight-bearing bone serving mainly for muscle attachments

b. Articulates proximally with lateral condyle of tibia and distally with tibia and talus, participating in ankle joint but not knee joint

c. Often used for bone grafts

2. Head


a. Forms synovial joint with lateral condyle of tibia and provides attachment to fibular collateral (lateral collateral) ligament at pointed apex

b. Connected to shaft by slender neck, against which common fibular nerve lies in vulnerable subcutaneous position

3. Shaft


a. Nonpalpable except distally where it continues as lateral malleolus

b. Interosseous border connected to tibia by interosseous membrane


The fibula is often used for vascularized bone grafts.


4. Lateral malleolus


a. Palpable subcutaneous prominence at lateral side of ankle that articulates medially with trochlea of talus

b. Gives attachment to lateral ligaments of ankle joint

F. Skeleton of Foot (Figure 5-4)


• Formed by 7 tarsals, 5 metatarsals, and 14 phalanges

1. Tarsals


a. Talus


(1) Transmits weight of body from leg to foot

(2) Articulates with tibia, fibula, calcaneus, and navicular bones

(3) Head is supported by plantar calcaneonavicular (spring) ligament in medial longitudinal arch of foot

image

5-4 Radiograph of the right foot and ankle, lateral projection.



Falling or jumping from a height may fracture the body of the talus and calcaneus. Violent dorsiflexion of the ankle joint (e.g., in motor vehicle accidents) may fracture the neck of the talus (Figure 5-5), which can interrupt the blood supply and lead to avascular necrosis of the body of the talus.


image

5-5 Radiograph of the proximal foot showing a fracture of the talar neck (arrows), which may interrupt the blood supply to the body of the talus to cause avascular necrosis.


(From Mettler, F A: Essentials of Radiology, 2nd ed. Philadelphia, Saunders, 2004, Figure 8-153.)



A fracture of the talar neck may cause avascular necrosis of the talar body.


b. Calcaneus


(1) Largest and strongest bone of foot

(2) Tuberosity gives attachment to calcaneal tendon and forms posterior end of longitudinal arch of foot, where it transmits 50% of weight on that extremity to ground


Avulsion or rupture of the calcaneal (Achilles) tendon disables the gastrocnemius-soleus so that the patient cannot plantar flex the foot. The calcaneus is the most frequently fractured tarsal bone, with the usual mechanism being a fall onto one or both heels from a height. There is a high incidence of associated vertebral compression fractures with that mechanism of injury, so the thoracolumbar spine should always be examined in these patients.



Calcaneal fracture from a fall is often accompanied by vertebral compression fractures.


c. Navicular

• Palpable medial tuberosity for tibialis posterior tendon


An accessory navicular bone may develop from a secondary ossification center in the navicular tuberosity at the attachment site of the tibialis posterior tendon. It may be a source of pain that is activity related or caused by pressure from a shoe. An accessory navicular often is associated with flatfoot (pes planus) (see II.K.4 following).



An accessory navicular bone may be a source of pain and is associated with flatfoot.


d. Cuboid

• Grooved on plantar surface by sulcus for fibularis longus tendon

e. Cuneiforms

• Medial, intermediate, and lateral

2. Metatarsals


a. Overview


The toes are numbered 1 to 5 starting with the great toe.



(1) Numbered from one to five from great toe to small toe

(2) Proximal base, curved shaft (convex dorsally), and distal head

(3) Heads collectively form anterior end of longitudinal arch of foot, transmitting 50% of weight on that extremity to ground

b. First metatarsal


(1) Shorter and stouter than other metatarsals because its head bears twice the weight of any other metatarsal bone

(2) Tuberosity on plantar surface of base for attachment of fibularis longus tendon

c. Fifth metatarsal

• Prominent tuberosity for attachment of fibularis brevis


Fibularis brevis may avulse tuberosity of the fifth metatarsal in forced inversion.



The metatarsal bones are frequently fractured either by dropping a heavy object on the forefoot or by the foot being run over. Stress fractures in the distal third of the second to fourth metatarsal bones are common in joggers and hikers. The tuberosity of the fifth metatarsal may be avulsed by the tendon of the fibularis brevis during forced inversion of the foot.


3. Phalanges


a. Miniature long bones with proximal base, shaft, and distal head

b. Number two in great toe and three each in toes 2-5


Foot skeleton: 7 tarsal, 5 metatarsal, and 14 phalangeal bones


II. Joints of Lower Extremity

A. Sacroiliac Joint

1. Paired joint between axial skeleton and pelvic girdle, transferring weight of upper body to lower extremity


Sacroiliac joints transfer weight from the upper body to the lower extremities.


2. Synovial joint (at least early in life) between auricular surfaces of sacrum and ilium, allowing little movement

3. Stabilized by interosseous sacroiliac, ventral and dorsal sacroiliac, iliolumbar, sacrospinous, and sacrotuberous ligaments


Pain resulting from an inflamed sacroiliac joint is often referred to the inferior part of the buttock and to the thigh. The sacroiliac joint is often the initial source of pain in young men with ankylosing spondylitis, a seronegative (rheumatoid factor) spondyloarthropathy. This chronic inflammatory disease subsequently involves the vertebral column, causing fusion of vertebrae (“bamboo spine”) and kyphosis. Aortitis with a diastolic murmur from aortic regurgitation may be present. Approximately 90% of patients possess the HLA-B27 antigen.



Sacroiliac joints are involved first in ankylosing spondylitis—the “bamboo spine” disease.


B. Pubic Symphysis


• Anterior midline joint with fibrocartilaginous interpubic disc between bodies of two pubic bones


The pubic symphysis is relatively immovable except in the latter stages of pregnancy, when hormones cause ligaments to loosen.


C. Hip Joint

1. Overview


a. Synovial ball-and-socket joint between head of femur and acetabulum of hip bone

b. Stable, while still allowing substantial movement, including flexion and extension, abduction and adduction, and medial and lateral rotation

c. Receives blood supply from medial and lateral femoral circumflex, superior and inferior gluteal, and obturator arteries

d. Innervated by femoral and obturator nerves, superior gluteal nerve, and nerve to quadratus femoris


Pain may be referred to the hip from the lumbar spine.


2. Acetabular labrum

• Fibrocartilaginous rim that deepens acetabulum and continues across acetabular notch as transverse acetabular ligament

3. Articular capsule



• Extends from acetabulum and transverse acetabular ligament to intertrochanteric line anteriorly and distal neck of femur posteriorly

4. Iliofemoral ligament


a. Inverted Y-shaped ligament, strongest of hip joint, reinforcing capsule anteriorly

b. Limits extension of hip joint and allows standing without muscular fatigue

5. Ischiofemoral ligament


a. Supports hip joint capsule posteriorly

b. Limits extension and medial rotation of hip joint

6. Pubofemoral ligament


a. Reinforces anterior, inferior part of capsule

b. Limits excessive abduction and helps limit extension of hip joint


Hip joint ligaments: iliofemoral, ischiofemoral, and pubofemoral


7. Ligament of head of femur



• Transmits artery to head of femur (from obturator artery), an important source of blood to femoral head in children but usually small or absent in adults

8. Movements at hip joint


a. Flexion: iliopsoas, rectus femoris, tensor fasciae latae, sartorius, pectineus, adductor longus, adductor brevis

b. Extension: gluteus maximus, hamstrings

c. Abduction: gluteus medius, gluteus minimus, tensor fasciae latae, sartorius

d. Adduction: adductor magnus, adductor longus, adductor brevis, pectineus, gracilis

e. Medial rotation: gluteus minimus, gluteus medius, tensor fasciae latae

f. Lateral rotation: obturator internus, obturator externus, piriformis, quadratus femoris, superior and inferior gemelli


“Developmental dysplasia of the hip” is the new term for “congenital dislocation of the hip.”



Osteoarthritis is the most common disease of the hip in adults. Severe joint degeneration may necessitate total hip replacement.


The hip frequently fractures at the femoral neck adjacent to the femoral head (subcapital fracture) and less frequently between the trochanters (pertrochanteric/intertrochanteric fracture). Intracapsular fractures of the femoral neck may interrupt the blood supply to the femoral head, resulting in avascular necrosis (Figures 5-6 and 5-7). Fractures are more common in elderly females than males because the incidence of osteoporosis is increased after menopause.


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5-6 Blood supply to head and neck of femur in anterior view and coronal section. In adults the blood supply to the head of the femur is mainly from the medial femoral circumflex artery. The artery to the head of the femur is usually small or absent in adults but is an important source of blood in children.


(From Netter, F H: Atlas of Human Anatomy, 4th ed. Philadelphia, Saunders, 2006, Plate 504.)


image

5-7 Fractures of proximal femur. Intracapsular fracture of femoral neck, especially if displaced, may disrupt blood supply to femoral head via retinacular branches of medial femoral circumflex artery and cause avascular necrosis. Intertrochanteric fracture is extracapsular and does not compromise blood supply to femoral head (see Figure 5-6).


(From Greene, W B: Netter’s Orthopaedics. Philadelphia, Saunders, 2006, Figure 17-21.)



Femoral neck fractures are common in postmenopausal women due to osteoporosis.



Traumatic hip dislocations are associated with automobile accidents and usually occur posteriorly from a blow to the knee while the hip is flexed and adducted (as when sitting in an automobile). The affected extremity will be shortened and will assume a characteristic position of flexion, adduction, and internal rotation in most cases. The posterior margin of the acetabulum may fracture, with damage to the sciatic nerve. Delayed reduction increases the risk of avascular necrosis of the femoral head.



Most traumatic hip dislocations are posterior with possible damage to the sciatic nerve.



A positive Trendelenburg sign often indicates paralyzed or weak gluteus medius and minimus muscles on the weight-bearing side that cause inability to abduct the hip (i.e., keep the pelvis level) (Figure 5-8).


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5-8 A, Normal right gluteus medius and minimus muscles. Left buttock does not sag when the left foot is raised from floor. B, Positive Trendelenburg sign. Left buttock drops when the left foot is raised as in walking or standing, indicating injury on the right side. Arrows, direction of pelvis movement.



Avascular necrosis of the femoral head is common after a femoral neck fracture.


D. Knee Joint (Figure 5-9)

1. Overview


a. Synovial hinge joint between femoral and tibial condyles, and including patellofemoral joint

b. Permits flexion and extension; last part of extension is accompanied by medial rotation of femur on weight-bearing tibia

c. Supplied by arteries forming genicular anastomosis (see Figure 5-24)

d. Supplied by femoral, obturator, tibial, and common fibular nerves

image

5-9 Magnetic resonance image of the right knee, coronal section.



Osteosarcoma (osteogenic sarcoma) is one of the most common primary malignant tumors of bone. It often occurs in the distal femur or proximal tibia, with 50% of the tumors involving the knee joint. Approximately 75% occur in patients under 20 years of age.



Fifty percent of osteosarcomas involve the knee joint.


2. Articular capsule


a. Attaches to margins of femoral and tibial condyles

b. Replaced anteriorly by quadriceps tendon and embedded patella

3. Tibial collateral ligament (medial collateral ligament)


a. Broad flat band extending from medial epicondyle of femur to medial condyle and shaft of tibia

b. Blends with capsule and firmly attaches to medial meniscus

c. Limits extension and abduction of leg at knee


Because the lateral side of the knee is struck more often (e.g., in a football tackle), the tibial collateral ligament is the most frequently torn ligament at the knee. Attachment to the medial meniscus means that the two structures usually are injured together. The unhappy triad of athletic knee injuries involves the tibial collateral ligament, medial meniscus, and anterior cruciate ligament.



The unhappy triad of knee injuries: tibial collateral ligament, medial meniscus, and ACL


4. Fibular collateral ligament (lateral collateral ligament)


a. Rounded cord between lateral epicondyle of femur and head of fibula

b. Does not blend with joint capsule and does not attach to lateral meniscus

c. Limits extension and adduction of leg at knee

5. Anterior and posterior cruciate ligaments


a. Overview


(1) Located inside articular capsule but outside synovial cavity

(2) Named for attachments to intercondylar area of tibia

(3) Stabilize joint best when knee is fully extended

b. Anterior cruciate ligament (ACL) limits anterior movement of tibia on femur

c. Posterior cruciate ligament (PCL) limits posterior movement of tibia on femur


Ruptured anterior cruciate ligament: anterior drawer sign. Ruptured posterior cruciate ligament: posterior drawer sign



With a rupture of the anterior cruciate ligament, the tibia can be pulled forward excessively on the femur in the flexed knee, exhibiting anterior drawer sign. In the less common rupture of the posterior cruciate ligament, the tibia can be pulled backward excessively on the femur, exhibiting posterior drawer sign.


6. Medial and lateral menisci


a. Fibrocartilage wedges anchored to anterior and posterior intercondylar areas of tibia

b. Medial meniscus C-shaped but lateral meniscus almost circular


The medial meniscus is more frequently injured because it is firmly attached to the fibrous capsule and the tibial collateral ligament, whereas the lateral meniscus is not attached to the fibular collateral ligament. A displaced cartilage fragment from a torn meniscus may lock the knee and prevent full extension. Only the periphery of the meniscus has the potential to heal because it has a vascular supply.



The medial meniscus is frequently injured with the attached tibial collateral ligament.


7. Synovial cavity

Related posts:

  1. The Neck
  2. The Upper Extremity
  3. The Pelvis and the Perineum
  4. The Head

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Jun 16, 2016 | Posted by in ANATOMY | Comments Off on The Lower Extremity

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