CRL Quiz 3 2009

1

A patient with an inactivating mutation in RANKL would present with the following bone defect:


  osteoporosis.

  osteosclerosis.

  osteopetrosis.

  osteomalacia.

  osteogenesis imperfecta.


Since RANKL is needed for osteoclast formation, a genetic defect that leads to production of inactive RANKL would lead to a deficiency in osteoclasts, and the subsequent increase in bone mass caused by a lack of bone resorption is called osteopetrosis.

2

High serum calcium levels, detected during routine clinical testing would NOT be caused by


  primary hyperparathyroidism.

  vitamin D deficiency.

  secondary hyperparathyroidism.

  high circulating PTHrP levels.

  breast cancer within the bone marrow space.


Vitamin D is a factor that increases serum calcium, so a lack of vitamin D would lead to lower, not higher serum calcium levels. All of the other conditions listed are associated with high serum calcium levels due to increased bone resorption.

3

Which one of the following is NOT a potential complication of a long bone fracture?


  Pseudoarthrosis.

  Deep venous thrombosis.

  Osteoporosis.

  Avascular necrosis.

  Persistent immobility.


Osteoporosis, the reduction of bone mass due to the loss of calcium and bone protein, is often a predisposing factor in the development of a fracture, however is not a complication of a previous fracture. The other listed answers are all potential complications of fracture.

4

Following a fall onto an outstretched hand a patient complains of pain and tenderness in the floor of the anatomical snuff box. Which one of the following structures is MOST likely to have been injured?


  Distal end of radius.

  Lunate bone of the wrist.

  Capitate bone of the wrist.

  Triangular fibrocartilaginous complex of the wrist.

  Scaphoid bone.


All structures are susceptible to injury however it is scaphoid which lies in the snuffbox, which produces the pain and tenderness and is MOAT likely to be injured.

5

A group of cyclists pedalling along Beach Road were suddenly confronted by a dog running across the road in front of them. The leading riders applied their brakes but unfortunately one of the cyclists fell off his bike, landed awkwardly on the tip of his shoulder, injuring the acromioclavicular joint. The acromioclavicular joint:


  is a synovial ball and socket joint.

  communicates with the shoulder joint via the subacromial bursa.

  is primarily stabilised by the coracoclavicular ligament.

  has a strong capsule reinforced on its sides by collateral ligaments.

  is rarely subluxed.


The A-C joint is not a ball & socket joint, does not communicate with the subacromial bursa, has a weak capsule and is commonly subluxed in this type of accident. It is however primarily stabilised by the coracoclavicular ligament.

6

A football player injures his knee during the final quarter of a game. Assessment of the knee by the club doctor reveals anterior instability of the tibia with respect to the femur (positive anterior drawer sign). Which one of the following structures is MOST likely to have been damaged?


  Medial meniscus.

  Patellar tendon.

  Anterior cruciate ligament.

  Posterior cruciate ligament.

  Lateral collateral ligament.


The anterior cruciate ligament resists anterior displacement of the tibia with respect to the femur. While the other structures may also be injured the anterior drawer sign specifically singles out the ACL.

7

The combination of movements occurring at the ankle joint are


  plantar flexion and dorsi flexion.

  inversion and eversion.

  adduction and abduction.

  medial rotation and lateral rotation.

  supination and pronation.


The ankle is a hinge joint therefore the movements occurring there are in the sagittal plane only: plantar and dorsi-flexion. The other movements are multi-planar and occur at joints of the foot.

8

When diagnosing a rare condition like osteosarcoma there are several mimics that must be considered. Which one of the following is LEAST likely to be confused with osteosarcoma in a 20 year old man?


  Osteomyelitis.

  Giant cell tumour.

  Paget's disease of bone.

  Bone cyst.

  Fracture repair.


Wrong age group. Not really a mimic of osteosarcoma.

9

A 30 year old woman has painful swollen proximal interphalyngeal joints on both hands. What is the MOST likely diagnosis?


  Osteoarthritis.

  Septic arthritis.

  Fibrous dysplasia.

  Rheumatoid arthritis.

  Gout.


A is incorrect: Usually distal, usually older, more Heberden's nodes than swelling. B is incorrect: Multiple joints, unlikely site, wrong age group. C is incorrect: Rubbish. E is incorrect: Classically in toes not hand.

10

A 52 year old man with a previous history of diabetes mellitus type 2 and mild hypertension presents to the emergency department with an acutely swollen painful right knee. He does not remember any injury or any previous similar episodes of joint pain. On examination the right knee is hot and swollen and the patient is very reluctant to move the knee as this causes severe pain. Which investigation is MOST likely to determine the correct diagnosis?


  Plain X-ray of the right knee.

  Full blood examination including a white cell count.

  Aspiration of right knee fluid for microscopy and culture.

  Magnetic resonance imaging (MRI) scan.

  Serum uric acid measurement.


The differential diagnosis is sepsis and gout and this can only be determined definitively by aspiration and examination of synovial fluid for uric acid crystals (gout) or an infectious agent (by gram stain and culture)

11

Which one of the following statements regarding non-steroidal anti-inflammatory drugs (NSAIDs) and related agents is NOT CORRECT?


  Aspirin inhibits both COX-1 and COX-2.

  Aspirin has anti-inflammatory and analgesic actions.

  Selective COX-2 inhibitors are generally considered to cause less gastrointestinal adverse effects than non-selective COX inhibitors.

  Paracetamol has potent anti-inflammatory activity.

  Paracetamol is associated with liver toxicity in overdose.


A is TRUE: Aspirin inhibits both of these COX isoforms although it is somewhat COX-1 selective. B is TRUE: Aspirin is used for both these indications, although commonly other more potent NSAIDs are used for more severe inflammation. C is TRUE: These compounds (Coxibs) were developed to limit the sometimes serious GI problems associated with non-selective NSAIDs. D is FALSE: Paracetamol has no anti-inflammatory action- reasons for this are unclear and will no doubt be made clearer when the mechanism (or mechanisms) of action of the drug are fully revealed. E is TRUE: Although there are a number of liver enzymatic pathways that can metabolise paracetamol into non-toxic and well excreted metabolites, when these pathways are saturated (as in overdose) a metabolic pathway is initiated that leads to formation of a reactive matabilite that can cause severe liver toxicity.

12

Regarding the effects of aging on skeletal muscle, which one of the following statements is NOT CORRECT?


  The slower time course of the isometric twitch can be attributed partly to a slower release and reuptake of Ca2+ by the muscle's internal storage sites.

  Muscle atrophy with age is due to a failure of the sarcoplasmic reticulum to synthesise sufficient myosin heavy chain protein.

  "Sarcopenia" is a term used to describe the age-related loss of muscle mass.

  Muscles are more easily injured and repair less successfully in old compared with young animals.

  Slow-to-fast motor unit remodelling contributes to the age-related changes in muscle function.


The sarcoplasmic reticulum (SR) is the muscle's internal storage site for Ca2+ and responsible for the release and reuptake of Ca2+ that helps determine rates of contraction and relaxation. The SR is not where myosin heavy chain is synthesized. E was also deemed 'NOT CORRECT' and awarded a mark as it is possible for a slow muscle fibre to be innervated by a fast nerve during motor unit remodelling although fast muscle fibres being innervated by a slow nerve is a more likely scenario.

13

The common flexor origin (shared point of attachment for the superficial flexor muscles of the anterior compartment of the forearm) is


  the medial epicondyle of the humerus.

  the lateral epicondyle of the humerus.

  the olecranon process of the ulna.

  the coronoid process of the ulna.

  the radial tuberosty.


The superficial flexor muscles of the anterior compartment of the forearm share a common tendon of origin attached to the medial epicondyle of the humerus.

14

The muscles of the superficial posterior compartment of the leg (superficial calf muscles) all insert into the


  femur.

  tibia.

  fibula.

  calcaneus.

  talus.


Gastrocnemius, Soleus and Plantaris all insert via the calcaneal tendon into the posterior surface of the Calcaneus.

15

Quadriceps Femoris is composed of all of the following EXCEPT


  rectus femoris.

  sartorius.

  vastus lateralis.

  vastus medialis.

  vastus intermedius.


Sartorius is not part of the Quadriceps complex.