S1: introduction to concepts in MSK

Question 1

What are the functions of bone?

Answer 1

Support 
Protection
Metabolic 
Storage 
Movement
Haematopoiesis

Question 2

What are the functions of skeletal muscle?

Answer 2

Locomotion
Posture
Metabolic
Venous return
Heat production
Continence

Question 3

What are the different types of connective tissue? What are their functions?

Answer 3

Tendon = force transmission muscle-bone
Ligament = support bone-bone
Fascia = compartmentalisation + protection
Articular cartilage = decrease friction
Fibrocartilage = shock absorption + increase bone congruity
Synovial membrane = secretes synovial fluid for joint and tendon lubrication
Bursa = synovial fluid-filled sacs to protect tendons, ligaments from friction

Question 4

What are the five different types of bone? Give two examples for each

Answer 4

Long = femur + humerus
Short = carpals + tarsals 
Flat = sternum + ilium
Sesamoid = patella + tendons of the hands
Irregular = vertebrae + sacrum

Question 5

What are processes? What two categories can they be split into?

Answer 5

Processes are prominent projections of a bone
Articulating
Non-articulating = usually the result of traction on the developing bone by muscles, ligaments etc

Question 6

What are depressions? What are openings?

Answer 6

Depressions = on the surface of bones provide for the passage of blood vessels and other soft tissues
Openings = occur primarily where blood nerves and vessels pass into or through the bone

Question 7

What is avascular necrosis? What are the causes?

Answer 7

Avascular necrosis is the death of bone due to loss of its blood supply
Causes include fractures, alcoholism, thrombosis and radiation

Question 8

What are joints? What three categories are there of joints?

Answer 8

A joint is an articulation between two or more bones
Trade off between range of movement and stability
Fibrous, cartilaginous + synovial

Question 9

What are fibrous joints and where are they found?

Answer 9

Collagen fibres joining bones
Very limited mobility
Found where great strength/stability are required eg. sutures of the skull + inferior tibiofibular joint

Question 10

What are cartilaginous joints and where are they found? What two categories are there?

Answer 10

Cartilaginous joints use cartilage to unite bones
Primary cartilaginous = united by hyaline cartilage and are completely immobile eg. first sternocoastal joint + the epiphyseal growth plates of long bones
Secondary cartilaginous = (also known as symphses) articulating bones are convered with hyaline cartilage with a pad of fibrocartilage between them eg. symphysis pubis + intervertebral discs

Question 11

What are synovial joints?

Answer 11

Separate bones are capped by smooth articular cartilage with a thin film of synovial fluid separating them
Found all over the skeleton

Question 12

What are the six categories of synovial joints and where are they found?

Answer 12

Plane eg. carpal bones of the wrist + facet joints of the spine
Conyloid eg. atlanto-occiptal joint + radiocarpal joint
Saddle eg. 1st carpometacarpal joint at base of thumb
Hinge eg. elbow joint between humerus and ulna
Pivot eg. atlanto-axial joint
Ball and socket eg. hip + shoulder joints

Question 13

What factors affect the range of movement of joints?

Answer 13

Structure or shape of articulating bones
Strength and tensions of the joint ligaments
Arrangement and tone of muscles around the joints
Disuse of a joint
Effect of hormones
Apposition of neighbouring soft tissues

Question 14

Describe the embryological development of synovial joints

Answer 14

Cells at the centre of the interzone region undergo apoptosis (programmed cell death) to form the joint cavity, while surrounding mesenchyme cells from the perichondrium will form the periosteum where they lie in contact with bone, and the joint capsule and supporting ligaments where they lie in contact with the developing joint
(in the knee joint, some of the cartilage within the joint is preserved and develops into intra-articular ligaments: the anterior and posterior cruciate ligaments of the knee)

Question 15

What are the three different types of levers? Name an example for each.

Answer 15

First-class = fulcrum between effort and load eg. head balanced on neck
Second-class = load between effort and fulcrum eg. standing on tip toes 
Third-class = effort between load and fulcrum eg. extending the elbow

Question 16

Define origin and insertion

Answer 16

The origin is the stationary anchor point and is usually sited proximally in the limb.
The insertion is the mobile attachment point and is usually sited distally in the limb.

Question 17

What do muscles do?

Answer 17

Muscles can only pull. They CANNOT push

Muscles can only act on the joints they (+their tendons) cross

Question 18

What are the three different types of muscle contraction?

Answer 18

Concentric contraction = muscle pulls while shortening eg. biceps curl
Eccentric contraction = muscle pulls while lengthening eg. knee extensors walking downhill
Isometric contraction = muscle pulls while staying same length eg. carrying a load

Question 19

What are the different arrangements of skeletal muscle fibres?

Answer 19

Parallel muscles have the fibres run parallel to the forcegenerating axis. Subdivided into strap, fusiform and fan-shaped (triangular or convergent)
Pennate muscles have one or more aponeuroses running through the muscle body from the tendon. Subdivided into unipennate, bipennate and multipennate
Circular muscles are where the fibres form concentric rings around a sphincter or opening

Question 20

What is a fascial compartment?

Answer 20

A fascial compartment is a region of the limb that contains muscles, nerves and blood vessels, surrounded by deep fascia

Question 21

What are aponeuroses?

Answer 21

Aponeuroses are sheet-like structures that are histologically similar to tendons. Their primary function is to join muscles of the body

Question 22

What is Hilton’s law?

Answer 22

Hilton’s law = the nerves supplying the muscles moving the joint also supply the joint capsule and the skin overlying the insertions of these muscles.

Question 23

What is segmentation controlled by?

Answer 23

Segmentation is controlled by Hox genes. These genes are expressed in a segmental pattern in a cranio-caudal (top-to-bottom) axis
The order that the Hox genes are encoded on the chromosome is reflected in the order in whey are expressed in the body

Question 24

What is a homeotic mutation?

Answer 24

A mutation that causes tissues to alter their normal differentiation pattern, producing integrated structures in unusual locations

Question 25

What is serial homology?

Answer 25

The upper and lower limbs have extremely similar development leading to extremely similar anatomy

Question 26

What directions do the developing upper and lower limbs rotate in?

Answer 26

Upper limbs rotate out 90 degrees - future elbows point backwards
Lower limbs rotate in 90 degrees - future knees point forwards

Question 27

What is a radiograph?

Answer 27

A radiograph is a projectional image generated by passage of x-rays through an object?
X-rays are absorbed by dense materials = appear white

Question 28

Advantages and disadvantages of x-rays

Answer 28

Advantages: x-rays are quick, readily available and inexpensive
Disadvantages: involve radiation + poor soft tissue contrast resolution

Question 29

Role of x-rays in MSK imaging

Answer 29

Initial imaging of choice for skeletal trauma/acute bone or joint injury
Also used for initial evaluation of chronic bone or joint pathologies

Question 30

What is a fracture? What are the different types?

Answer 30

Complete or incomplete break in the continuity of the bone

Transverse, linear, oblique displaced, oblique non-displaced, spiral, greenstick and comminuted

Question 31

Phases of fracture healing

Answer 31

Inflammatory phase: haematoma formation, tissue death, inflammation proliferation
Reparative phase: granulation tissue, soft callus formation, hard callus formation
Remodelling phase

Question 32

Advantages and disadvantages of CT scanning

Answer 32

Advantages: soft tissue detail is much better than x-ray
Whole body CT can be performed in a short time
Subtle undisplaced fractures are better visualised
Slices can be reformatted to create multiplanar and 3D images
Disadvantages: radiation does higher than x-ray
Motion artefact if patient moves
Poor soft tissue detail compared with MRI

Question 33

What are the differences between T1, T2 and STIR MRI scans?

Answer 33

T1 = fat is bright, fluid is dark
T2 = fat is bright, fluid is bright 
STIR = fat is dark, fluid is bright

Question 34

Advantages and disadvantages of MRI

Answer 34

Advantages: good soft-tissue imaging, detailed anatomy of joints + excellent for bone marrow imaging
Disadvantages: scan takes a long time, noisy environment, claustrophobic patients can’t tolerate scans + metallic and electronic devices need to be removed

Question 35

Advantages and disadvantages of ultrasound

Answer 35

Advantages: no radiation, excellent soft tissue resolution for superficial soft tissue + excellent imaging modality of tendons and peripheral nerves
Disadvantages: operator development, poor deep tissue resolution + limited bone and intra-articular imaging

Question 36

What is nuclear imaging?

Answer 36

Radioisotope-labelled, biologically active drugs that are administered to the patient serve as a marker of biologic activity
Assess areas of metabolically active bone