Musculoskeletal7-11 Flashcards
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?
Posterior cruciate ligmaent
What is the function of the posterior cruciate ligament?
It prevents anterior displacement of the femur (relative to the tibia) when the knee is flexed.
What muscle tendon is vulnerable to injury due to impingement between the acromion and the head of the humerus?
supraspinatus muscle
Prior to passing crossing the wrist within the carpal tunnel, which muscles does the median nerve pass between?
flexor digitorum superificialis and the flexor digitorum profundus muscles
Which sarcolemma structure is responsible for coordinating the contraction of all myofibrils?
T-tubules
These are envaginations of the sarcolemma that (1) transmit depolarization signals to the sarcoplasmic reticulum and (2) trigger the release of calcium
What serum marker is indicative of osteoblastic activity?
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.
What serum marker is the most reliable indication of osteoclastic activity?
urinary deoxypyridinoline
less reliable, but usable markers are (1) tartate-resistance acid phosphatase (2) urinary hydroxyproline
Function:
Supraspinatus muscle
- Abduction of the arm
- Stabilization of the glenohumeral joint
Why is it important to monitor chest expansion in a patient with ankylosing spondylitis?
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.
What is the safest gluteal quadrant for a intragluteal injection?
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.
Most common cause of Trendelenburg gait?
- injury to the contralateral superior gluteal nerve in the superomedial gluteal quadrant
- injury to the gluteus medius
What is another name for Trendelenburg gait?
gluteus medius gait
Diagnosis:
Patients hip drops downward when the ipsilateral foot is lifted from the ground
Trendelenberg (gluteus medius) gait
Which gluteus muscle is injured in a patient with Trendelenberg gait?
The gluteus medius muscle on the sign opposite to, or “contralateral” from the hip drop.
Clinical Manifestation:
Femoral nerve injury
- Weakness of the quadriceps muscle
- Decreased sensation over the anterior and medial thigh
- Decreased sensation over the medial leg
- Diminished patellar reflex
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?
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.
What section of the forearm recieves sensory stimulation from the musculocutaneous nerve (C5-7)?
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.
Which region of the sarcomere contains only myosin thick filaments?
H band
Diagnosis:
Your pt presents with (1) symmetric proximal muscle weakness. Muscle biopsy indicates inflammation, necrosis and regeneration of muscle fibers.
Polymyositis
Pathogenesis:
Polymyositis
- Myocytes become damaged
- Sarcolemma over-expresses MHC class I proteins
- Infiltration of CD8+ lymphocytes damage the myocyte
Clinical Manifestation:
Axillary nerve injury
- Flattened/paralysis of the deltoid muscle
- loss of sensation over the lateral arm
What is the most commonly dislocated joint in the body? Why?
Glenohumeral joint because of the shallow articulation between the humeral head and the glenoid fossa of the scapula.
What type of dislocation might result from a blow to an externally rotated and abducted arm?
anterior dislocation of the humerus
Think of a football player throwing a football.
Which nerve would be injured in an anterior dislocation of the humerus?
Axillary nerve
Function:
Motor and sensory function of the axillary nerve
Motor= innervation of the (1) teres minor and (2) deltoid
Sensory=innervation of the skin overlaying the lateral shoulder
What nerve is responsible for:
(1) dorsiflexion the lower leg
(2) flexion of the toes
(3) sensation for the sole of the foot
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.
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?
Reactive arthritis
This is a HLA-B27, seronegative spondyloarthropathy.
Damage to this nerve results in foot drop (i.e. inability to dorsiflex)
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.
Differentiate the histological appearance of muscle fibers in (1) early and (2) late Duchenne muscular dystrophy.
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
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
carpal tunnel syndrome
Diagnosis:
Positive Tinel sign
carpal tunnel syndrome
Diagnosis:
Positive Phalen test
carpal tunnel syndrome
Diagnosis:
- decreased sensation over the fifth finger
- flattened hypothenar eminence
“claw hand” deformity (ulnar nerve injury)
What are the two main sites that result in injury the ulnar nerve?
- Hook of hamate and pisiform bone in wrist (Guyon’s canal)
- medial epicondyle of the humerus
Mechanism of Action:
Colchicine
affects tubulin polymerization into microtubules
Side effects of colchicine
(1) nausea (2) abdominal pain (3) diarrhea
