Musculoskeletal, skin, and connective tissue Flashcards
Anterior drawer sign
With the patient supine, bend the knee at a 90 degree angle. If there is an increase in anterior gliding of tibia, there is an ACL injury. Anterior refers to ACL
Posterior drawer sign
With the patient supine, bend the knee at a 90 degree angle. If there is an increase in posterior gliding of tibia, there is an PCL injury. Posterior refers to PCL
Abnormal passive abduction
with the patient supine and knee either extended or at 30 degree angle, if a lateral (valgus) force leads to a medial space widening of tibia, than there is a MCL injury
Abnormal passive adduction
with the patient supine and knee either extended or at 30 degree angle, if a medial (varus) force leads to a lateral space widening of tibia, than there is a LCL injury
McMurray test
With patient supine and knee internally and externally rotated during range of motion: pain and popping on external rotation is indicative of a medial meniscal tear, pain and popping on internal rotation is indicative of a lateral meniscal tear.
Knee injuries due to lateral force to planted leg
A common injury in contact sports is due to lateral force applied to a planted leg. Classically, damage consists of ACL, MCL, and medial meniscus (attached to MCL). However, the lateral meniscus injury is more common. It presents with acute knee pain and sign of joint injury/ instability.
Prepatellar bursitis
Also called housemaid’s knee. It can be caused by repeated trauma or pressure from extensive kneeling. On x-ray, there is prepatellar bursitis and Baker cyst.
Baker cyst
A popliteal fluid collection commonly related to chronic joint disease.
Rotator cuff muscles
Shoulder muscles that form the rotator cuff from most anterior to posterior the subscapularis, supraspinatus, infraspinatus, and teres minor. They are innervated by primarily C5-C6. SItS (small t is for teres minor)
Subscapularis
It is innervated by the upper and lower subscapular nerves. It medially rotates and adducts arm.
Supraspinatus
It is innervated by the suprascapular nerve. It abducts the arm initially (before action from the deltoid) and is the most commonly injured rotator cuff muscle. It is assesed by the empty/ full can test.
Infraspinatus
It is innervated by the suprascapular nerve. It laterally rotates arm and is often injured due to pitching.
Medial epicondylitis (golfer’s elbow)
It occurs due to repetitive flexion (forehand shots) or idiopathic. It causes pain near the medial epicondyle.
Lateral epicondylitis (tennis elbow)
It occurs due to repetitive extension (backhand shots) or idiopathic, causing pain near the lateral epicondyle.
Wrist bones
Starting from proximal radial side. Some Lovers Try Positions That They Cannot Handle: Scaphoid, Lunate, Triquetrum , Pisiform, Trapezium, Trapezoid, Capitate, and Hamate.
Scaphoid injury
It can be palpated in the anatomical snuff box and is the most commonly fractured carpal bone and is prone to avascular necrosis owing to retrograde blood supply.
Lunate injury
Dislocation of the lunate may cause acute carpal tunnel syndrome.
Hamate injury
Fall on an outstretched hand can damage the hook of the hamate can cause ulnar nerve injury.
Carpal tunnel syndrome
Due to entrapment of median nerve in carpal tunnel; nerve compression leads to paresthesia, pain, and numbness in the distribution of the median nerve. It is associated with pregnancy, rheumatoid arthritis, hypothyroidism, and may be associated with repetitive use.
Guyon canal syndrome
It occurs due to compression of the ulnar nerve at wrist or hand. It is classically seen in cyclists due to pressure from handlebars. Symptoms usually begin with a feeling of pins and needles in the ring and little fingers before progressing to a loss of sensation and/or impaired motor function of the intrinsic muscles of the hand.
Axillary nerve
C5-C6. It is derived from the posterior cord. It innervates the teres minor and deltoid muscles. It can get injured with fracture of the surgical neck of the humerus and anterior dislocation of the humerus. Injury presents with a flattened deltoid, loss of arm abduction at shoulder greater than 15 degrees, and loss of sensation over deltoid muscle and lateral arm.
Musculocutaneous nerve
C5-C7. It is derived from the lateral cord. It innervates the anterior compartment of the arm. Cause of injury includes upper trunk compression. It presents as loss of forearm flexion and supination and loss of sensation over the lateral forearm.
Radial nerve
C5-T1. It is derived from the posterior cord. It innervates the posterior compartment of the forearm (extensor and supinator muscles) and the radial dorsal side of the hand. Injury can occur due to midshaft fracture of the humerus; compression of the axilla, eg due to crutches or sleeping with your arm over the chair (Saturday night palsy). Presentation includes wrist drop (loss of elbow, wrist and finger extension), a decrease in grip strength (wrist extension is necessary for the maximal action of flexors), and loss of sensation over the posterior arm/forearm and dorsal side of the hand.
Median nerve
C5-T1. It is derived from the lateral and medial cords. It innervates flexor and pronator muscles of the forearm, thenar muscles, and the flexor muscle of digits 2 and 3. It innervates the cutaneous aspect of the radial side of the palm and the palmer side of digits 1-4. Injury can occur with a supracondylar fracture of the humerus (proximal lesion) or carpal tunnel syndrome and wrist laceration (distal lesion). Injury presents as ape hand and pope’s blessing (can’t flex fingers 2 and 3); loss of wrist flexion of lateral fingers, thumb opposition, lumbricals (flex the metacarpophalangeal joints and extend the interphalangeal joints) of 2nd and 3rd digits. There is loss of sensation over the thenar eminence and the dorsal and palmar aspects of the lateral 3.5 fingers with a proximal lesion. Tinel sign (tingling on percussion) will be positive with carpal tunnel syndrome.
Ulnar nerve
C8-T1. It is derived from the medial cord. It innervates flexor muscles of the forearm, flexor muscle of metacarpophalangeal and interphalangeal joints of digits 4 and 5, and the intermediate and hypothenar muscles. It also innervates the cutaneous palm of the ulnar side and the palmar side of digits 4 and 5. Injury can occur with a fracture of the medial epicondyle of the humerous “funny bone” or with a fractured hook of hamate (distal lesion). Injury presents with a Ulnar claw (can’t extend fingers 4 and 5), radial deviation of wrist upon flexion (proximal lesion). There is also a loss of wrist flexion, flexion of medial fingers, abduction and adduction of fingers (interossei), action of medial 2 lumbrical (flex the metacarpophalangeal joints and extend the interphalangeal joints) muscles. There is also a loss of sensation over the medial 1.5 fingers including hypothenar eminence.
Recurrent branch of median nerve
C5-T1. It is derived from the median nerve. It innervates the thenar muscles. Injury can occur with superficial laceration of palm. It presents as ape hand. The loss of the thenar muscle group (opposition, abduction, and flexion of thumb). There is no loss of sensation.
Erb palsy
It is also called waiter’s tip. It occurs due to traction or tear of upper (Erb-er) trunk: C5-C6 roots. In infants it occurs due to lateral traction on the neck during delivery. In adults it occurs with trauma. Muscles effected include deltoid and supraspinatus, which abducts the arm so the arm hangs by the side; infraspinatus, which laterally rotates the arm so it is medially rotated, and biceps brachii, which flexes and supinates the forearm so that the arm is extended and pronated.
Brachial plexus lesions
Composed of roots, trunks, divisions, cords, and branches. Randy Travis Drinks Cold Beer.
Klumpke palsy
It occurs to traction or tear of the lower trunk: C8-T1 root. In infants injury can occur with an upward force on the arm during delivery. In adults, it occurs due to trauma (eg grabbing a tree branch to break a fall). Muscle defects include intrinsic hand muscles (lumbricals, interossei, thenar, hypothenar). It presents as a total claw hand; the lumbricals normally flex MCP joints and extend DIP and PIP joints.
Thoracic outlet syndrome
It occurs due to compression of the lower trunk (C8 and T1) and subclavian vessels. Causes include a cervical rib (a supernumerary rib which arises from the seventh cervical vertebra) or a pancoast tumor. Muscle defects include intrinsic hand muscles (lumbricals, interossei, thenar, hypothenar). It presents as atrophy of intrinsic hand muscles; ischemia, pain, and edema due to vascular compression.
Winged scapula
It occurs due to a lesion of the long thoracic nerve (C5-C7). Causes include axillary node dissection after a mastectomy or a stab wound. The muscle defect is in the serratus anterior causing there to be the inability to anchor the scapula to thoracic cage, leading to inability to abduct the arm above the horizontal position.
Upper trunk
C5 and C6. It contributes to the lateral and posterior cords. It is damaged in Erb palsy (waiter’s tip)
Middle trunk
C7. It contributes to the lateral and posterior cords.
Lower trunk
C8 and T1. It contributes to the posterior and medial cords. It is damaged in Klumpke palsy (claw hand)
Lateral cord
Made up of upper and middle trunk (C5-C7). It contributes to the musculocutaneous and median (flexor) nerves.
Posterior cord
Made up of the upper, middle, and lower trunks (C5-T1). It contributes to the axillary and radial nerves (extensor).
Medial cord
Made up of the lower trunk (C8-T1). It contributes to the median (flexor) and ulnar nerve.
Long thoracic
C5-C7. It innervates the serratus anterior and injury results in a winged scapula.
Deltoid paralysis
injury to the axillary nerve
Saturday nigh palsy (wrist drop)
injury to the radial nerve
Difficulty flexing elbow with sensory loss
injury to the musculocutaneous nerve
Decreased thumb function and Pope’s blessing
injury to the median nerve
Injury to the intrinsic muscles of the hand, a claw hand
injury to the ulnar nerve
Distortions of the hand
At rest, a balance exists between the extrinsic flexors and extensors of the hand, as well as the intrinsic muscles of the hand- particularly the lumbrical muscles (flexion of the MCP, extension of DIP and PIP joints). Clawing is best seen with distal lesions of the median or ulnar nerves. The remaining extrinsic flexors of the digits exaggerate the loss of the lumbricals, so that fingers are extended at the MCP and flexion at the DIP and PIP. Deficits are less pronounced in proximal lesions and they present during voluntary flexion of the digits.
Ulnar claw
Digits 4 and 5 remain flexed. occurs due to a distal ulnar nerve lesion and is seen during extension of fingers or at rest
Popes blessing
Digits 1 and 2 remain extended. Occurs due to a proximal lesion of the median nerve and is seen while trying to make a fist.
Median claw
Digits 1 and 2 remain flexed. Occurs due to distal median nerve lesion and is seen while extending fingers or at rest.
OK gesture
5th digit remains extended. Occurs due to a proximal ulnar nerve and is seen while trying to make a fist.
Thenar muscles
Innervated by the median nerve, atrophy will cause an unopposable thumb (ape hand). Muscles include Opponens pollicis, Abductor pollicis brevis, superficial head (deep head is innervated by the ulnar nerve) (Opposem Abduct, Flex: OAF).
Hypothenar muscle
innervated by the ulnar nerve. Muscles include Opponens digiti minimi, Abductor digiti minimi, Flexor digiti minimi brevis. (Opposem Abduct, Flex: OAF).
Dorsal interossei muscles
abduct the fingers DAB= Dorsals ABduct
Palmar interossei
adduct the fingers PAD= Palmars ADDuct.
Lumbricals
Flex at the MCP joint, extend PIP and DIP joints.
Obturator nerve
L2-L4. Injury can occur during pelvic surgery and results in reduced medial thigh sensation and reduced thigh adduction.
Femoral nerve
L2-L4. Injury can occur with a pelvic fracture. Injury results in reduced thigh flexion and leg extension.
Common peroneal nerve
L4-S2. Injury can occur due to trauma or compression of the lateral aspect of the leg, and fibular neck fracture. It presents as foot drop (inverted and plantarflexed at rest), occurs due to loss of eversion and dorsiflexion. Steppage gait (high stepping). Loss of sensation on the dorsum of foot. PED= Peroneal Everts and Dorsiflexes; if injured foot dropPED.
Tibial nerve
L4-S3. Injury may occur due to knee trauma, Baker cyst (proximal lesion); tarsal tunnel syndrome (distal lesion). Results in an inability to curl toes and loss of sensation on the sole of foot. In a proximal lesions, foot everted at rest with a loss of inversion and plantarflexion. TIP=Tibial Inverts and Plantarflexes; if injured, can’t stand on TIPtoes.
Superior gluteal nerve
L4-S1. It innervates the medius and minimus gluteal muscles. Injury can be iatrogenic during an intramuscular injection to upper medial gluteal region. It would present as trendelenburg sign/gait (pelvis tilts because the weight bearing leg cannot maintain alignment of pelvis through hip abduction). Lesion is on the contralateral side to the side of the hip that drops, ipsilateral to the extremity on which the patient stands.
Inferior gluteal nerve
L5-S2. It innervates the gluteal maximus. Injury can occur with a posterior hip dislocation. It will present as difficulty climbing stairs, rising from seated position and loss of hip extension.
Sciatic nerve
L4-S3. It innervates the posterior thing, splits into common peroneal and tibial nerves.
Pudendal nerve
S2-S4. It innervates perineum. It can be blocked with local anesthetic during childbirth using the ischial spin as a landmark for injection.
Signs of lumbrosacral radiculopathy
There will be paresthesias and weakness in the distribution of specific lumbar or sacral spinal nerves. It is often due to intervertebral disc herniation in which the nerve association with the inferior vertebral body is impinged (eg herniation of L3-L4 disc affects the L4 spinal nerve). Intervertebral discs generally herniate posterolaterally, due to the thin posterior longitudinal ligament and thicker anterior longitudinal ligament along the midline of the vertebral bodies.
Level of vertebral injury with weakness of knee extension, and a decrease in patellar reflex
L3-L4
Level of vertebral injury with weakness of dorsiflexion and difficulty in heel-walking
L4-L5
Level of vertebral injury with weakness of plantarflexion and difficulty in toe walking with a decrease in achilles reflex
L5-S1
Artery traveling with the long thoracic nerve
Lateral thoracic
Artery traveling with the axillary nerve
Posterior circumflex
Artery traveling with the radial nerve
Deep brachial
Artery traveling with the median nerve
brachial
Artery traveling with the tibial nerve
Popliteal, which turns into the posterior tibial.
Striated muscle excitation from nerve
Action potential depolarization opens presynaptic voltage-gated Ca channels, inducing neurotransmitter release. Postsynaptic ligand binding leads to muscle cell depolarization in the motor end plate.
Striated muscle conduction
Depolarization travels along the muscle cell and down the T-tubule. Depolarization of the voltage-sensitive dihydropyridine receptor, with is mechanically coupled to the ryanodine receptor on the sarcoplasmic reticulum, inducing a conformational change and causing Ca release from the sacroplasmic reticulum.
Striated muscle contraction
Released Ca binds to troponin C, causing a conformational change that moves tropomyosin out of the myosin-binding groove on actin filaments. Myosin releases bound ADP and inorganic PO4, leading to displacement of myosin on the actin filament (power stroke). Contraction results in shortening of H and I bands and between Z lines (HIZ shrinkage), but the A band remains the same length (A band is Always the same length). Binding of a new ATP molecule causes the detachment of myosin head from actin filament. Hydrolysis of bound ATP, converting it to ADP, myosin head adopts a high-energy position (cooked) for the next contraction cycle.
T-tubules
It is an extension of plasma membrane juxtaposed with terminal cisternae and are a part of the sarcoplasmic reticulum. In skeleton muscle, there are 1 T-tubule and 2 terminal cisternae= triad. In cardiac muscle, 1 T-tubule and 1 terminal cisternae=diad.
H band
the zone of the thick filaments that is not superimposed by the thin filaments.
Z band
marks the boarders of sacromere
A band
contains the entire length of a single thick filament
Type 1 muscle fiber
A slow twitch; red fibers resulting from an increase in mitochondria and myoglobin concentration (an increase in oxidative phosphorylation), which causes a sustained contraction. Think “1 slow red ox”
Type 2 muscle fiber
A fast twitch; white fibers resulting from a decrease in mitochondria and myoglobin concentration (an increase in anaerobic glycolysis); weight training results in hypertrophy of fast-twitch muscle fibers.
Smooth muscle contraction
With increased intracellular concentrations in the smooth muscle cell, the Ca2+ ions can combine and form a complex with the acidic protein calmodulin. The Ca2+-calmodulin complex activates myosin light chain kinase (MLCK), which allows it to phosphorylate the light chain of myosin. In addition to the Ca2+-dependent activation of myosin light chain kinase, the state of myosin light chain phosphorylation is further regulated by myosin light chain phosphatase. This enzyme removes the high-energy phosphate from the light chain of myosin to promote smooth muscle relaxation.
Smooth muscle relaxation
Smooth muscle relaxation can also occur through nitric oxide-mediated stimulation of guanylate cyclase activity, which leads to increased cGMP-induced smooth muscle relaxation. Increased levels of cGMP promote myosin light chain phosphatase activity. (Remember: “Nitric oXide -> RelaXation”)
Endochondral ossification
bones of the axial and appendicular skeleton and base of the skull. Cartilaginous model for bone is first made by chondrocytes. Osteoclasts and ostesoblasts later replace with woven bone and then remodel to lamellar bone. In adults, woven bone occurs after fractures and in Paget disease.
Membranous ossification
Includes bones of calvarium and facial bones. Woven bone formed directly without cartilage. Later remodeled to lamellar bone.
Osteoblasts
Builds bone by secreting collagen and catalyzing mineralization. Differentiate from mesenchymal stem cells in periosteum.
Osteoclasts
Multinucleated cells that dissolve by secreting acid and collagenases. Differentiate from monocytes.
Parathyroid hormone
At low, intermittent levels, exerts anabolic effects (building bone) on osteoblasts and osteoclasts (indirect). Chronically increased PTH levels (due to primary hyperparathyroidism) cause catabolic effects (osteitis fibrosa cystica).
Estrogen and bone biology
Estrogen inhibits apoptosis in bone-forming osteoblasts and induces apoptosis in bone-resorbing osteoclasts. Estrogen deficiency (surgical or postmenopausal), excess cycles of remolding, and bone resorption lead to osteoporosis.
Achondroplasia
Failure of longitudinal bone growth (endochondral ossification), causing shortening of limbs. Membranous ossification is not affected leading to a large head relative to limbs. Constitutive activation of fibroblast growth factor receptor (FGFR3) actually inhibits chondrocyte proliferation. Over 85% of mutations occur sporadically; autosomal dominant with full penetrance (homozygosity is lethal). It is the most common cause of dwarfism.
Primary osteoporosis
Trabecular (spongy) bone loses mass and interconnections despite normal bone mineralization and lab values (serum Ca and PO4). Diagnosed by a bone mineralization and lab values (serum Ca and PO4). Diagnosed by a bone mineral density test (DEXA) with a T-score less than -2.5. Can be caused by long term exogenous steroid use, anticonvulsants, anticoagulants, thyroid replacement therapy. It can lead to vertebral compression fractures, acute back pain, loss of height, kyphosis. Also can present with fractures of femoral neck, distal radius (Colles fracture).
Type I osteoporosis
Post-menopausal. There is a increase in bone resorption due to a decrease in estrogen levels.
Type II osteoporosis
Senile. Affects men and women over 70.
Prevention and treatment of osteoporosis
Prophylaxis includes regular weight bearing exercise and adequate Ca and vitamin D intake throughout adulthood. Treatment includes bisphosphonates, PTH analogs, SERMs, rarely calcitonin; Donosumab (monoclonal antibody against RANKL).
Osteopetrosis
Marble bone disease. Failure of normal bone resorption due to defective osteoblasts, creating thickened, dense bones that are prone to fracture. Bone fills marrow space, creating pancytopenia, extramedullary hematopoiesis. Mutations (eg carbonic anhydrase II) impair ability of osteoclast to generate acidic environment necessary for bone resorption. X-rays show bone in bone appearance (diffusely dense). Can result in cranial nerve impingement and palsies as a result of narrowed foramina. Bone marrow transplant is potentially curative as osteoclasts are derived from monocytes.
Osteomalacia/ rickets
Vitamin D deficiency leads to osteomalacia in adults and rickets in children. Due to defective mineralization/ calcification of osteoid, there are soft bones that bow out. A decrease in vitamin D causes there to be a decrease in serum Ca, increasing PTH secretion, decreasing serum PO4. Hyperactivity of osteoblasts increases ALP (osteoblasts require alkaline environment).
Paget disease of the bone
Also called osteitis dormans. It is a common, localized disorder of bone remodeling caused by an increase in both osteoblastic and osteoclastic activity. Serum Ca, phosphorus and PTH levels are normal. Alkaline phosphatase (ALP) is increased. The bone has a mosaic pattern of woven and lamellar bone. Long bones will have chalk stick fracture. There is an increase in blood flow from an increase is arteriovenous shunts may cause high output heart failure. There is an increase risk of osteogenic sarcoma. Hat size can be increased; hearing loss is common due to auditory foramen narrowing. The stages of Paget disease include: Lytic (osteoclasts), Mixed (osteoclasts plus osteoblasts), Sclerotic (osteoblasts), Quiescent (minimal osteoclasts/ osteoblast activity). H&E stain will show osteocytes within lacunae (scattered small white dots) and chaotic mosaic pattern (lacy purple lines) of bone remodeling.
Osteonecrosis
Avascular necrosis. Infarction of bone and marrow, which is usually very painful. The most common site is the femoral head (due to insufficiency of the medial circumflex femoral artery). Causes include Alcoholism, Sickle cell disease, Storage disorders, Exogenous/ Endogenous corticosteroids, Pancreatitis, Trauma, Idiopathic (Legg-Calve-Perthes disease), Caisson (the bends): ASEPTIC. X-ray will show irregular lucencies with adjacent sclerosis. MRI will show dark serpiginous necrotic bone.
