Musculoskeletal 10 - Arthritis 11 & Fractures Flashcards
1
Q
What is the Heuter-Volkmann principal?
A
- Bones respond to the compression and tension you put on them
- Increased compression (pressing) decreases longitudinal growth, increased tension (pulling) increases longitudinal growth
- Therefore, affects growth of the bone
2
Q
Define varus and valgus
A
- Bow legged (away from the midline) is varus
- Knees pointing towards the midline is valgus (knock-knee)
- Results in uneven distribution of weight on the knee
3
Q
How do varus and valgus deformities affect osteoarthritis risk?
A
- Varus deformities increase pressure on the medial half of the knee joint
- Valgus deformities increase pressure on the lateral half of the knee joint
- Therefore, this erodes the joint and alters the gap between the bones
4
Q
What is an osteotomy?
A
- Cut the tibia to change the shape of the leg
- Used to attempt to delay osteoarthritis
5
Q
What is Wolffs law?
A
- Bone responds to the stresses put on it
- If a bone is used more (increased load), it remodels to become stronger and resists loading
- If a bone is used less (decreased load), it will become less dense and weaker
- Going to space decreases density, sport increases density
6
Q
What is developmental dysplasia of the hip?
A
- Disorder affecting babies
- In utero, ball of the hip is not aligned in the socket, and therefore the hip socket does not become rounded in response (due to Wolffs law)
- More likely in females, babies that are breech, and the right hip (as this hip is pushed towards the spine)
- Affected by in-utero behaviour (baby kicking)
- Increased risk of osteoarthritis even if the joint is loose and not dislocated
7
Q
Describe cam and pincer hips
A
- Cam impingement (in those who do a lot of exercise) causes the femoral neck to become thicker due to Wolffs law. Deep flexion therefore knocks into the labrum.
- Pincer impingement causes formation of a deep socket, In deep flexion, the socket is hit by the femoral neck despite it being normal, and the femoral head on the other side.
8
Q
List main groups who are affected by osteoarthritis
A
- Elderly (use over time)
- Injury (torn labrum)
- Shape of the bone in young people (eg. knees and hip)
9
Q
What is the most effective way of treating arthritis?
A
- Exercise (strengthens muscles to reduce the strain on joints)
- Joint replacement (however, only last 20 years as bone underneath breaks down due to lack of pressure ie. Wolffs law, and once replaced less effective)
10
Q
Describe structure of a synovial joint
A
- Two bones articulating together with cartilage (fibrocartilage or hyaline cartilage)
- Synovial fluid between the bones
11
Q
Describe the structure of articular cartilage
A
- Superficial layer (collagen fibres completely horizontal, as this is the gliding zone)
- Middle transitional zone (oblique fibres, must resist compression and gliding)
- Deep zone (horizontally directed cartilage, main function is resistance to compression)
- Tidemark prevents infections entering the joint (however, the lack of blood supply does not allow repair)
12
Q
Describe the arcade model of benninghoff
A
Collagen fibril changes from horizontal in the superficial layer, to oblique in the middle layer to vertical in the deep layer
13
Q
How do torn ACLs occur and what is the consequence?
A
- Internal rotation upon a straight leg
- Affects the alignment , the femur is further back on the tibia. Results in abnormal loading and therefore possible risk of arthritis, and meniscal tears
- ACL important for pivoting, and protecting the cartilage to ensure it is loading in the correct position
14
Q
Compare Z score and T score from DEXA scans
A
- Z score is a comparison of a persons bone density with that of an average person of the same age and sex
- T score is a comparison of a persons bone density with a healthy 30 year old of the same sex
15
Q
What is the risk of bisphosphonates?
A
- Abnormal fractures as bone is “dead”, and abnormally formed
- Eg. fracture of the body of the femur when just walking
