06: MSK Flashcards
List two common pediatric bone fractures.
- Greenstick (bending stress; incomplete extension through bone width)
- Torus (axial force; simple buckle fracture of cortex)
Knee: Unhappy triad involves damage to which structures?
- MCL
- ACL
- Medial meniscus
Nerve supply to “SITS” muscles
- Supraspinatus (suprascapular n)
- Infraspinatus (suprascapular n)
- Teres minor (axillary n)
- Subscapularis (upper and lower subscap nn)
Which muscles play pivotal roles in arm abduction below 90 degrees?
Supraspinatus (0-15o) then deltoid (15-100o)
Which muscles play pivotal roles in arm abduction above 90 degrees?
- Deltoid (15-100o)
- Traps
- Serratus anterior
Most commonly fractured carpal bone
Scaphoid (typically due to fall of outstretched hand)
Acute carpal tunnel syndrome may be a result of (X) carpal bone dislocation
X = lunate
Which carpal bone is palpable in anatomical snuff box?
Scaphoid
Humerus surgical neck fracture: (X) muscle will become flattened and (Y) movements will be compromised.
X = deltoid Y = abduction over 15o
(Axillary n injury)
Humerus surgical neck fracture: sensation is lost in which areas?
Over deltoid and lateral aspect of upper arm (axillary n injury)
Pitcher presents with shoulder pain and loss of sensation over lateral forearm. What movements would you expect to be compromised?
Forearm flexion and supination (musculocutaneous n injury)
Humerus fractures: surgical neck injures (X) n, midshaft injures (Y) nerve, supracondylar injures (Z) n.
X = Axillary Y = Radial Z = Median (if anteromedial displacement of proximal humerus)
(“ARM” from proximal to distal fractures); if humerus displaced anterolateral in supracodylar fracture, RADIAL N injured
67 yo M presents with finger drop on R hand. He denies history of trauma, is a retired police officer, and spends his days doing work around the house/yard. Sensation intact, and both elbow and wrist flexion/extension intact. Likely diagnosis/mechanism of injury?
Injury to posterior interosseous nerve (deep branch of radial) in supinator canal
(potentially due to repetitive pronation/supination such as excessive screwdriver use)
Use of crutches may compress (X) nerve.
X = radial
Which nerve travels with brachial artery between (X) upper arm muscles?
X = biceps and brachialis
Median n
Median nerve enters forearm and travels between which muscles?
- Two heads of pronator teres
2. Then between FDS and FDP
(X) nerve passes in Guyon’s canal, between which bones?
X = ulnar
Hook of hamate and pisiform
A superficial palm laceration will likely compromise which sensation/muscle movements?
Recurrent branch of median nerve damage most likely;
Sensation intact
“OAF” (from 1/2 LOAF) will be compromised (loss of thenar muscle group - opposition, abduction, flexion of thumb; ape hand)
“Waiter’s tip”, aka (X) palsy, is due to which injury?
X = Erb's Upper trunk (C5-6) of brachial plexus
“Total claw hand”, aka (X) palsy, is due to which injury?
X = Klumpke Lower trunk (C8-T1) of brachial plexus
Lumbricals have which actions and which joints?
Flex at MCP
Extend at PIP, DIP
Clawing of hand (median or ulnar claws) is more prominent with (proximal/distal) nerve lesions.
Distal (clawing of fingers evident at rest)
Housemaid’s knee: (X) is affected
X = pre-patellar bursa (bursitis due to repetitive kneeling)
Carpal tunnel: excision of (X) improves symptoms.
X = transverse carpal ligament (aka flexor retinaculum)
Aside from median nerve, which structures travel in carpal tunnel?
Tendons of FDP, FDS, and FPL
Thoracic outlet syndrome most commonly occurs in (X) triangle.
X = Scalene
Formed by anterior and middle scalenes and the first rib
A patient with a cervical rib experiences exertional arm pain due to:
Compression of Subclavian artery
Scaphoid fractures are at risk for which key complication?
Avascular necrosis (blood supply from radial a branch easily interrupted by fracture)
Most of the space in greater sciatic foramen is occupied by:
Piriformis (hence potential compression of sciatic nerve in this foramen = piriformis syndrome)
Abdominal surgery (like appendectomy) can cause injury to (X) nerve, which would manifest with which Sx?
X = iliohypogastric (T12-L1)
Burning/tingling pain radiating to inguinal/suprapubic region
Absent cremaster reflex is due to (X) nerve compromise. What other Sx would you expect?
X = genitofemoral (L1-2)
Decreased sensation to scrotum/labia majora and medial thigh
Sciatic nerve roots:
L4-S3
Tibial nerve primarily responsible for which muscle actions?
“TIP” = Tibial Inverts and Plantarflexes (if injured, can’t stand on TIP-toes)
Peroneal nerve primarily responsible for which muscle actions?
“PED” = Peroneal Everts and Dorsiflexes (if injured, foot dropPED)
Baker cyst would most likely compromise which nerve?
Tibial
Patient presents with hip drop on L side (when standing on R leg). Where’s the injury?
R superior gluteal n
Pt presents with hip drop upon walking and tends to lean torso toward L side as she walks. Where’s the injury?
L superior gluteal n (leans toward injured side to compensate for contralateral/R hip drop)
(X) nerve (enters/exits) pelvis via (Y) just to re-(enter/exit) via (Z).
X = pudendal (S2-4) Exits Y = greater sciatic foramen Re-enter Z = lesser sciatic foramen (near ischial spine)
Pudendal nerve muscle innervation:
External urethral and anal sphincters; pelvic floor muscles
Most common elbow injury in kids (usually ages 1-4)
Radial head subluxation (“Nursemaid’s elbow”) - tear of annular ligament from periosteal attachment at radial neck
2 yo brought in by mom due to refusal to move his L arm. You notice it’s held close to his side, extended, and pronated. Kid doesn’t seem distressed until you try to move his arm. Diagnosis/mechanism and treatment?
Nursemaid’s elbow (radial head subluxation) likely due to sharp pull on arm when elbow was pronated and extended;
Can be resolved by supinating and flexing arm
Herniation of L3/L4 disc affects which spinal nerve(s)?
L4 and below (nerves inferior to site of herniation)
Difficulty in toe walking and loss of (X) reflex is due to injury at which disc level?
X = achilles
L5-S1 (weak plantar flexion)
Difficulty in heel walking is due to injury at which disc level?
L4-5 (weak dorsiflexion)
Loss of patellar reflex due to injury at which disc level?
L3-4 (weak knee extension)
(X) artery travels with (Y) nerve around surgical neck of humerus
X = posterior circumflex Y = axillary
(X) artery travels with (Y) nerve around midshaft of humerus
X = deep brachial Y = radial
(X) artery travels with (Y) nerve in popliteal fossa
X = popliteal Y = tibial
Which 3 ions determine electrical potential difference (voltage) across membrane?
Na, K, Cl
Hip drop can occur with intramuscular injection in which location?
Superomedial quadrant of buttock
Pt with back pain that’s worse with walking and relieved with bending forward and walking uphill. Diagnosis?
Spinal stenosis - usually due to degenerative arthritis of spine
Spinal stenosis can eventually lead to which changes/complications?
- Intervertebral disc degeneration and herniation
- Ligamentum flavum hypertrophy
- Osteophyte formation at facet joints
Osteonecrosis of the femoral head most likely due to (X) artery compromise in femoral neck fracture.
X = medial circumflex (off deep femoral a)
Smooth muscle contraction: key initiator is (X), which activates (Y).
X = Ca (which binds calmodulin) Y = Myosin light chain kinase
Smooth muscle relaxation: key initiator is (X), which comes from (Y) cells.
X = NO Y = Endothelial (Ca stimulates NO synthase and NO then diffuses into smooth muscle)