Muscle, bone, and fractures

Question 1

Define muscle proprioreceptors

Answer 1

specialized sensory receptors that relay info about muscle dynamics

Question 2

Describe the neuronal pathway in muscle stretch receptors

Answer 2

1. Increased length & speed of stretch
2. Afferent pathway via dorsal root ganglion
3. Activation of inhibitory interneuron and alpha motor neuron
4. Simultaneous inhibition of antagonist muscle (prevents overstretching) & activation of agonist muscle (contraction)

Question 3

Type of innervation of muscle stretch receptors + location

Answer 3

Type Ia and II sensory axons
Located in the body of muscle

Question 4

What activates muscle stretch receptors

Answer 4

Increased muscle stretch
Responsible for deep tendon reflexes

Question 5

Describe the nerve pathway for Golgi tendon organ

Answer 5

1. Increased tension
2. Afferent pathway via DRG
3. Activation of inhibitory interneuron
4. Inhibition of agonist muscle (reduced tension within muscle and tendon

Question 6

Type of innervation of Golgi tendon organ + location

Answer 6

Type Ib sensory axons
Tendons

Question 7

What activates Golgi tendon organ

Answer 7

Increased muscle tension

Question 8

Location of endochondral ossification

Answer 8

Bones of axial & appendicular skeleton, base of skull

Question 9

Describe the process of endochondral ossification

Answer 9

1. Cartilagenous model of bone is made by chondrocytes
2. Osteoblasts/clasts later replace woven bone and remodel to lamellar bone

Question 10

When does woven bone occur in adults

Answer 10

After fractures and in Paget disease

Question 11

In what disease is endochondral ossification defective

Answer 11

Achondroplasia

Question 12

Where does membranous ossification occur

Answer 12

Bones of calvarium, facial bones, clavicle

Question 13

Describe the process of membranous ossification

Answer 13

Woven bone formed directly wo cartilage, then remodeled to lamellar

Question 14

Describe the function of osteoblasts

Answer 14

Builds bone by secreting collagen & catalyzing mineralization in alkaline environments via ALP

Question 15

Differentiation of osteoblasts

Answer 15

From mesenchymal stem cells in periosteum

Question 16

What factors regulate osteoblast activity

Answer 16

Bone ALP, osteocalcin, propeptides of type I collagen

Question 17

Describe the function of osteoclasts

Answer 17

Dissolves bone by secreting protons and collagenases

Question 18

Differentiation of osteoclasts

Answer 18

Fusion of monocyte/macrophage lineage precursors

Question 19

How is osteoclast activity regulated

Answer 19

RANK receptors on osteoclasts are stimulated by RANKL (RANK ligand, expressed on osteoblasts)
OPG (osteoprotegerin, a RANKL decoy receptor) binds RANKL to prevent RANK-RANKL interaction = reduction in activity

Question 20

Describe the function of PTH in bone formation

Answer 20

At low, intermittent levels, exerts anabolic effects (building bone) on osteoblasts and osteoclasts (indirect)

Question 21

What are the chronic effects of high PTH levels

Answer 21

Primary hyperparathyroidism
cause catabolic effects (osteitis fibrosa cystica)

Question 22

Function of estrogen in bone formation

Answer 22

Inhibits apoptosis in osteoblasts and induces apoptosis in osteoclasts
Causes closure of epiphyseal plate during puberty

Question 23

What does estrogen deficiency cause to bones

Answer 23

(Surgical/postmenopausal)
Increases cycles of remodeling and bone resorption = risk of osteoporosis

Question 24

Describe medial epicondylitis

Answer 24

Golfer’s elbow
due to repetitive flexion or idiopathic = pain near medial epicondyle

Question 25

Describe lateral epicondylitis

Answer 25

Tennis elbow
Repetitive extension (backhand shots) or idiopathic = pain near lateral epicondyle

Question 26

Who are found to commonly have clavicle fractures

Answer 26

Children and as birth trauma

Question 27

Causes of clavicle fractures

Answer 27

fall on outstretched hand or by direct trauma to shoulder

Question 28

Weakest point of clavicle

Answer 28

at the junction of middle and lateral thirds

Question 29

Common location of clavicle fracture

Answer 29

middle third segment

Question 30

Presentation of clavicle fracture

Answer 30

Presents as shoulder drop, shortened clavicle (lateral fragment is depressed due to arm weight and medially rotated by arm adductors [eg, pectoralis major])

Question 31

Define Guyon canal syndrome and who are they seen in

Answer 31

Compression of ulnar nerve at wrist
Classically seen in cyclists due to pressure from handlebars
May also be seen with fracture/dislocation of the hook of hamate

Question 32

Define carpal tunnel syndrome

Answer 32

Entrapment of median nerve in carpal tunnel (between transverse carpal ligament and carpal bones) = nerve compression causing paresthesia, pain, and numbness in distribution of median nerve

Question 33

Clinical findings of carpal tunnel syndrome

Answer 33

Thenar eminence atrophies but sensation spared (bc palmar cutaneous branch enters hand external to carpal tunnel)

Question 34

Tests for carpal tunnel syndrome

Answer 34

Tinel sign (percussion of wrist causes tingling) and Phalen maneuver (90° flexion of wrist causes tingling)

Question 35

Associations of carpal tunnel syndrome

Answer 35

Pregnancy (due to edema), RA, hypothyroidism, diabetes, acromegaly, dialysis-related amyloidosis
May be associated with repetitive use

Question 36

Define metacarpal neck fracture, seen commonly in which metacarpal

Answer 36

Also called boxer’s fracture
Common fracture caused by direct blow with a closed fist (eg, from punching a wall). Most commonly seen in the 5th metacarpal

Question 37

Define iliopsoas abscess and pathology

Answer 37

Collection of pus in iliopsoas compartment
May spread from blood (hematogenous) or from adjacent structures (eg, vertebral osteomyelitis, tuberculous spondylitis/Pott disease, pyelonephritis)

Question 38

What is iliopsoas abscess associated with

Answer 38

Crohn disease, diabetes, and immunocompromised states

Question 39

Microbiological cause of iliopsoas abscess

Answer 39

Staphylococcus aureus most commonly isolated, but may also occur 2° to tuberculosis

Question 40

Clinical (physical) findings of iliopsoas abscess

Answer 40

flank pain and bulge, fever, inguinal mass
Positive psoas sign (hip extension exacerbates lower abdominal pain)

Question 41

Lab findings of iliopsoas abscess

Answer 41

Imaging (CT/MRI) will show focal hypodense lesion within the muscle plane

Question 42

Tx of iliopsoas abscess

Answer 42

Antibiotics based on culture, CT-guided percutaneous drainage (PCD), or surgical drainage