Musculoskeletal: Anatomy - Bones of lower limb Flashcards
Components of the pelvic girdle
Sacrum
Right and left hip bones
Joined anteriorly at pubic symphysis
Function of the pelvic girdle
Attaches free lower limb to axial skeleton
Protective and supportive function for abdomen, pelvis, perineum and lower limbs
How are the femurs directed? What is the purpose?
Oblique orientation directed inferomedially
Returns centre of gravity following transfer of body weight from pelvic girdle to femurs
Two roles of the fibula
Muscle attachment
Formation of ankle joint
Does not bear or transfer weight (as it does not articulate with the femur)
Three primary bones which fuse to make the hip bone
- Ilium
- Ischium
- Pubis
When do the ilium, ischium and pubis fuse to create the hip bone?
End of teenage years
Describe the ossification and fusion of the hip bone
At birth: three primary bones joined by hyaline cartilage
Children: incomplete ossification
By age 9: ischiopubic rami fuses
By puberty: three bones separated by triradiate cartilage
Between 15-17yo: bones begin to fuse
Between 20-25yo: fusion complete
Describe the components of the acetabulum
Ilium forms superior part
Pubic forms anterior part
Ischium forms posteroinferior part
Where does a person’s body weight rest when sitting?
Ischial tuberosity
What makes up the boundaries of the obturator foramen?
Pubis and ischium and their rami
What closes the obturator foramen? Is this closure complete?
Obturator membrane
Not complete: small passageway (obturator canal)
What structures are carried within the obturator canal?
Obturator nerve and vessels
What is the name of the articular surface of the hip that receives the femoral head?
Lunate surface of the acetabulum
What is the longest and heaviest bone in the body?
Femur
What is the length of the femur in relation to a person’s height?
~1/4
What is the significance of the fovea?
Medially placed depression for the ligament of the head
In early life, the ligament gives passage to an artery supplying the epiphysis of the femoral head
Is the angle of inclination greater or smaller in females? Why?
Smaller
Increased distance between acetabula (due to the wider lesser pelvis) and greater obliquity of the femoral shaft
What is the effect of age on the angle of inclination?
Decreases
What is the normal angle of inclination in an adult?
126 degrees
What is the normal angle of torsion (or declination) in males and females?
Males: 7°
Females: 12°
Describe the normal pattern of bowing in the femur. How is this changed in rickets?
Slight convexity anteriorly
In rickets this may increase and proceed laterally as well as anteriorly due to weaking of the shaft
What vertebral level does the iliac tubercle correspond to?
L5
What muscular landmark does the gluteal fold correspond with?
Fat pad associated with the inferior border of gluteus maximus
What type of bone is the patella? How does it form?
Sesamoid
Forms within the tendon of quadriceps femoris
What two factors keep the patella centred in the intercondylar groove of the femur during extension at the knee?
Vertical ridge of posterior articular surface of patella
Balanced pull of vastus muscles
What is the second largest bone in the body?
Tibia
What are the three surfaces of the tibia?
Medial
Lateral-interosseous
Posterior
What makes up the shin?
Anterior border and medial surface of the tibia
Where does the patellar ligament attach distally?
Tibial tuberosity
Where is the tibial shaft thinnest?
Junction between middle and distal thirds
What replaces the interosseous border of the tibia inferiorly? What is this landmark’s purpose?
Fibular notch which accommodates and provides fibrous attachment to the distal fibula
What is the nutrient foramen?
Obliquely directed vascular groove immediately distal to the soleal line leads to the nutrient foramen
From it the nutrient canal runs inferiorly in the tibia before opening into the medullary cavity
What attaches the fibula to the tibia?
Tibiofibular syndesmosis (including the interosseous membrane)
Which is more prominent: lateral or medial malleolus?
Lateral
Which is more posterior: lateral or medial malleolus?
Lateral
Which extends more distally: lateral or medial malleolus?
Lateral extends ~1cm more distally
What does the apex of the fibular head articulate with?
Fibular facet on the posterolateral inferior aspect of the lateral tibial condyle
What are the three borders and surfaces of the fibula?
Borders: anterior, interosseous, posterior
Surfaces: medial, lateral, posterior
Where is the tibial tuberosity palpated?
~5cm distal to the apex of the patella
Where is the pubic tubercle palpable?
2cm from the pubic symphysis at the anterior extremity of the pubic crest
Where is PSIS palpable?
4cm lateral to midline at the bottom of a skin dimple
Where is the greater trochanter palpable?
~10cm inferior to the iliac crest on the lateral thigh
How many tarsal bones are in the foot?
7
List the 7 tarsal bones. Which articulates with the leg bones?
- Talus*
- Calcaneus
- Cuboid
- Navicular
- Medial cuneiform
- Intermediate cuneiform
- Lateral cuneiform
*articulates with the leg bones
How does the talus transmit body weight?
Receives from tibia
Distributes between calcaneus and the forefoot via the spring ligament suspended across a gap between sustentaculum tali and the navicular bone
What is the only tarsal bone that lacks any muscular or tendinous attachments?
Talus
What is the largest bone in the foot?
Calcaneus
Which part of the calcaneus contacts the ground when standing?
The medial tubercle of the calcaneal tuberosity
Which bones does the calcaneus articulate with?
Talus and cuboid
Which bones do the cuneiforms articulate with?
All articulate with the navicular posteriorly and their respective metatarsals anteriorly
Lateral cuneiform also articulates with the cuboid
What defines the borders of the forefoot and hindfoot?
Tarsometatarsal line
Which is the longest metatarsal?
2nd
Where are the medial and lateral sesamoid bones of the foot located?
Plantar surface of the head of the 1st metatarsal
Describe the proximal articulations of the metatarsals
1st MT: medial cuneiform
2nd MT: intermediate cuneiform
3rd MT: lateral cuneiform
4-5th MTs: cuboid
What type of ossification do the lower limb bones undergo?
Endochondral
What is osteochondrosis?
Irritation and injury of epiphysial plates and developing bone as a result of physical activity and rapid growth
Four common sites of avulsion fracture of the hip
ASIS
AIIS
Ischial tuberosity
Ischiopubic rami
What is the typical mechanism of avulsion fractures of the hip?
Sudden acceleration or deceleration (e.g. sprinting, kicking)
Define apophyses
Bony projections that lack secondary ossification centres
Coxa vara vs coxa valga
Coxa vara: decreased angle of inclination
Coxa valga: increased angle of inclination
Varus vs valgus
Varus: distal element of bone/joint deviates towards midline
Valgus: distal element of bone/joint deviates away from midline
What is the effect of coxa vara?
Mild shortening of lower limb
Limits passive abduction
What is the cause and typical presentation of SCFE?
Slipped capital femoral epiphysis
Occurs due to acute trauma or repetitive microtraumas that place increased shearing stress on epiphysis (i.e. particularly abduction and lateral rotation of thigh)
Presents with hip discomfort which may be referred to the knee
What is the most frequently fractured part of the femur?
Neck
Typical mechanism of fractures of the greater trochanter and femoral shaft
Direct trauma
What is the most frequently fractured part of the tibia?
Junction of middle and inferior thirds (narrowest part)
What is a possible complication of tibial fracture involving the nutrient canal?
Nonunion of bone fragments due to damage to the nutrient artery
What is the typical mechanism of transverse march fractures of the tibia?
People who take long hikes without conditioning
Describe the pathophysiology of Osgood-Schlatter disease
Tibial tuberosity usually forms by inferior bone growth from the superior epiphysial centre at age 10, but separate centre for tibial tuberosity may appear at age 12
Disruption of epiphysial plate at tibial tuberosity may cause inflammation of tuberosity and chronic recurring pain during adolescence
When does the primary ossification centre for the superior end of the tibia appear? When does it join the shaft of the tibia?
Appears shortly after birth, joins shaft of tibia at age 16-18
What is the common site of fracture in the fibula? What are they often associated with?
2-6cm proximal to the distal end of the lateral malleolus
Often associated with fracture-dislocation of the ankle
Which part of the fibula is used during bone grafting and why?
Middle third as this is where the nutrient foramen with nutrient artery is located
What is the typical mechanism and pattern of calcaneal fracture?
Hard fall onto heel
Often comminuted
What is the typical mechanism of talar fracture? What is a possible complication?
Severe dorsiflexion of ankle
May result in posterior dislocation of the body of the talus
What is the typical mechanism of metatarsal fracture?
Heavy weight dropped on foot
What is a dancer’s fracture?
Fracture of metatarsal occurring when dancer loses balance and falls whilst en pointe (full body weight through metatarsal)
What is the typical mechanism of avulsion fracture of the 5th metatarsal tuberosity?
Sudden violent inversion of ankle (may be associated with severe ankle sprain)
Common in basketball and tennis
What is os trigonum? What causes it and how common is it?
Accessory bone formed when secondary ossification centre for lateral tubercle of talus fails to unite with the body, fractures and progresses to nonunion
May be caused by applied stress (forceful plantarflexion) during adolescence
Occurs in 14-25% of adults, with increased prevalence in soccer players and ballet dancers
What is the purpose of the sesamoid bones of the great toe?
Bear weight during latter part of stance phase of walking
What is the typical mechanism of fracture of the sesamoid bones?
Crush injury
