Musculoskeletal7-11

Question 1

Which ligament within the articular capsule of the kenee joint attaches the posterior part of the intercondlar area of the tibia and thea anterior lateral surface of the medial epicondyle of the femur?

Answer 1

Posterior cruciate ligmaent

Question 2

What is the function of the posterior cruciate ligament?

Answer 2

It prevents anterior displacement of the femur (relative to the tibia) when the knee is flexed.

Question 3

What muscle tendon is vulnerable to injury due to impingement between the acromion and the head of the humerus?

Answer 3

supraspinatus muscle

Question 4

Prior to passing crossing the wrist within the carpal tunnel, which muscles does the median nerve pass between?

Answer 4

flexor digitorum superificialis and the flexor digitorum profundus muscles

Question 5

Which sarcolemma structure is responsible for coordinating the contraction of all myofibrils?

Answer 5

T-tubules

These are envaginations of the sarcolemma that (1) transmit depolarization signals to the sarcoplasmic reticulum and (2) trigger the release of calcium

Question 6

What serum marker is indicative of osteoblastic activity?

Answer 6

Bone-specific alkaline phosphatase

Total alkaline phosphatase includes that produced in the liver, AND the bone. You can differentiate the two using (1) electrophoreisis and (2) specific monoclonal antibodies. Also, bone-specific alkaline phosphatse can be denatured by heat.

Question 7

What serum marker is the most reliable indication of osteoclastic activity?

Answer 7

urinary deoxypyridinoline

less reliable, but usable markers are (1) tartate-resistance acid phosphatase (2) urinary hydroxyproline

Question 8

Function:

Supraspinatus muscle

Answer 8

1. Abduction of the arm
2. Stabilization of the glenohumeral joint

Question 9

Why is it important to monitor chest expansion in a patient with ankylosing spondylitis?

Answer 9

Ankylosing spondylitis is associated with enthesopathies of the costovertebral and costosternal junctions. The pain from enthesopathy can limit chest wall expansion and lead to hypoventilation.

Question 10

What is the safest gluteal quadrant for a intragluteal injection?

Answer 10

The absolute safest space is in the anterolateral gluteal area (von Hoschstetter triangle) however, the superolateral quadrant may also be used.

You are “safe” from the sciatic nerve and the superior gluteal nerve.

Question 11

Most common cause of Trendelenburg gait?

Answer 11

1. injury to the contralateral superior gluteal nerve in the superomedial gluteal quadrant
2. injury to the gluteus medius

Question 12

What is another name for Trendelenburg gait?

Answer 12

gluteus medius gait

Question 13

Diagnosis:

Patients hip drops downward when the ipsilateral foot is lifted from the ground

Answer 13

Trendelenberg (gluteus medius) gait

Question 14

Which gluteus muscle is injured in a patient with Trendelenberg gait?

Answer 14

The gluteus medius muscle on the sign opposite to, or “contralateral” from the hip drop.

Question 15

Clinical Manifestation:

Femoral nerve injury

Answer 15

1. Weakness of the quadriceps muscle
2. Decreased sensation over the anterior and medial thigh
3. Decreased sensation over the medial leg
4. Diminished patellar reflex

Question 16

You have a 5-year-old male patient who has joint laxity, loose skin and easy bruisability. You diagnose him with Ehlers-Danlos syndrome. Upon biochemical evaluation you note the presence of disulfide-rich globular domains. What stage of collagen synthesis is impaired in this patient?

Answer 16

Extracellular cleavage of collagen is impaired in this patient.

Procollagen has two disulfide-rich terminal extensions that increase its solubility. Normally, it is cleaved extracellularly into tropocollagen which is insoluble and crosslinked to form strong collagen.

Question 17

What section of the forearm recieves sensory stimulation from the musculocutaneous nerve (C5-7)?

Answer 17

lateral forearm

After innervating the major forearm flexors (biceps brachii, brachialis) and coracobrachialis, the remaining nerves from the musculocutaneous nerve become the lateral cutaneous nerve of the forearm.

Question 18

Which region of the sarcomere contains only myosin thick filaments?

Answer 18

H band

Question 19

Diagnosis:

Your pt presents with (1) symmetric proximal muscle weakness. Muscle biopsy indicates inflammation, necrosis and regeneration of muscle fibers.

Answer 19

Polymyositis

Question 20

Pathogenesis:

Polymyositis

Answer 20

1. Myocytes become damaged
2. Sarcolemma over-expresses MHC class I proteins
3. Infiltration of CD8+ lymphocytes damage the myocyte

Question 21

Clinical Manifestation:

Axillary nerve injury

Answer 21

1. Flattened/paralysis of the deltoid muscle
2. loss of sensation over the lateral arm

Question 22

What is the most commonly dislocated joint in the body? Why?

Answer 22

Glenohumeral joint because of the shallow articulation between the humeral head and the glenoid fossa of the scapula.

Question 23

What type of dislocation might result from a blow to an externally rotated and abducted arm?

Answer 23

anterior dislocation of the humerus

Think of a football player throwing a football.

Question 24

Which nerve would be injured in an anterior dislocation of the humerus?

Answer 24

Axillary nerve

Question 25

Function:

Motor and sensory function of the axillary nerve

Answer 25

Motor= innervation of the (1) teres minor and (2) deltoid
Sensory=innervation of the skin overlaying the lateral shoulder

Question 26

What nerve is responsible for:

(1) dorsiflexion the lower leg
(2) flexion of the toes
(3) sensation for the sole of the foot

Answer 26

tibial nerve

Patients with tibial nerve injury usually present with often hold their foot in the dorsiflexed position and everted. They also lack sensation on the plantar surface of the foot.

Question 27

Your patient has (1) nongonococcal urethritis (2) conjunctivitis & (3) arthritis. You tell him 20% of patients with this diagnosis develop sacroilitis. What is the diagnosis?

Answer 27

Reactive arthritis

This is a HLA-B27, seronegative spondyloarthropathy.

Question 28

Damage to this nerve results in foot drop (i.e. inability to dorsiflex)

Answer 28

Common peroneal nerve

The common peroneal nerve is most commonly damaged as it traces the lateral aspect of the fibular neck. Injury is often due to bony fracture or compression.

Question 29

Differentiate the histological appearance of muscle fibers in (1) early and (2) late Duchenne muscular dystrophy.

Answer 29

Early: hypertrophy of distal muscles, because they are compensating for atrophied proximal muscles
Late: Fibrofatty (fat and connective tissue) muscle replacement of the distal muscles and continued atrophy of proximal muscles

Question 30

Diagnosis:

Your patient has pain/paresthesia in (1) the first 3 digits (2) the radial half of the 4th digit (3) weakness in the thumb & (4) thenar atrophy

Answer 30

carpal tunnel syndrome

Question 31

Diagnosis:

Positive Tinel sign

Answer 31

carpal tunnel syndrome

Question 32

Diagnosis:

Positive Phalen test

Answer 32

carpal tunnel syndrome

Question 33

Diagnosis:

1. decreased sensation over the fifth finger
2. flattened hypothenar eminence

Answer 33

“claw hand” deformity (ulnar nerve injury)

Question 34

What are the two main sites that result in injury the ulnar nerve?

Answer 34

1. Hook of hamate and pisiform bone in wrist (Guyon’s canal)
2. medial epicondyle of the humerus

Question 35

Mechanism of Action:

Colchicine

Answer 35

affects tubulin polymerization into microtubules

Question 36

Side effects of colchicine

Answer 36

(1) nausea (2) abdominal pain (3) diarrhea