Musculoskeletal Skin and Connective Tissue F.A

Supraspinatus, infraspinatus, teres minor and subscapularis.

Rotator cuff muscles

Innervated by suprascapular nerve, abducts arm initially. Most common rotator cuff injury, assessed by “empty/full can” test.

Supraspinatus muscle

Innervated by suprascapular nerve, externally rotation the arm. “Pitching injury.”

Infraspinatus muscle

Innervated by axillary nerve, adducts and externally rotates arm.

Teres minor muscle

Internally rotates and adducts arm.

Subscapularis muscle

Flattened deltoid, loss of arm abduction at shoulder (>15 grades) and loss of sensation over deltoid and lateral arm. Causes: fractured surgical neck of humerus, anterior dislocation of humerus.

Axillary nerve injury (C5-C6)

Decrease biceps reflex, loss of forearm flexion and supination, and loss of sensation over radial and dorsal forearm. Causes: upper trunk compression.

Musculocutaneous nerve injury (C5-C7)

“Ape hand” and “hand of benediction”, loss of wrist flexion and function of the lateral two lumbricals, opponens pollicis, abductor pollicis brevis, and flexor pollicis brevis, loss of sensation over thenar eminence and dorsal and palmar aspects of lateral 3 ½ fingers (proximal lesion). Causes: supracondylar fracture of humerus → proximas lesion, carpal tunnel syndrome and wrist laceration → distal lesion.

Median nerve injury (C6-T1)

“Claw” on digit extension, radial deviation of wrist upon flexion (proximal lesion), decrease flexion of 3er and 4th fingers, decrease abduction and adduction of fingers (interossei), decrease thumb adduction (pollicis), decrease actions of ulnar 2 lumbrical muscles, and loss of sensation over ulnar 1 ½ fingers including hypothenar eminence. Causes: Fracture of medial epicondyle of humerus (proximal lesion), fracture hook of hamate (distal lesion, from fall on outstretched hand), comnpression of nerve against hamate as the wrist rests on handlebar during cycling.

Ulnar nerve injury (C8-T1)

Injury of traction/tear of upper brachial trunk (C5-6 roots). Causes: lateral traction on neck during delivery (infants), trauma leading to neck traction like falling on head and shoulder in motorcycle accidents (adults).

Erb palsy

Injury of traction or tear of lower brachial thrunk (C8-T1 roots), resulting in claw hand. Muscle defecit: lumbricals, interossei, thenar, hypothenar. Causes: upward force on arm during delivery (infants), trauma (eg, grabbing a tree branch to break a fall) (adults).

Klumpke palsy

Injury to the long thoracic nerve (root C5-7), resulting in the inability to anchor the scapula to the thoracic cage → cannot abduct arm above horizontal position. Muscle deficit: Serratus anterior. Causes: axillary node dissection after mastectomy, stab wounds.

Winged scapula

Compression of the lower brachial trunk and subclavian vessels (commonly within the scalene triangle), resulting in ischemia, pain, edema, atrophy of intrinsic hand muscles (lumbricals, interossei, thenar, hypothenar). Causes: cervical/anomaulous first ribs, pancoast tumor.

Thoracic outlet syndrome

Most commonly fracture, typically due to a fall on an outstretched hand presents with radial wrist pain and tenderness in the anatomic snuff-box. Complication include avascular necrosis and nonunion due to retrograde blood supply from a branch of the radial artery.

Scaphoid fracture

Impinge median nerve (​​​​​​​ weakness of thumb abduction, flexion, and opposition) and cause carpal tunnel syndrome.

Lunate discolation

Can cause ulnar nerve compression (Guyon canal syndrome).

Hamate fracture

Carpal bones

Scaphoid, lunate, triquetrum, pisiform, hamate, capitate, trapezoid, trapezium.

Hands muscles

Thenar (median - opponens pollicis, abductor pollicis brevis, flexor pollicis brevis superficial head), hypothenar (ulnar - opponen digiti minimi, abductor digiti minimi, flexor digiti minimi brevis), dorsal interossei (ulnar), palmar interossei (ulnar), and lumbricals (1st/2nd - median, 3rd/4th - ulnar).

Oppose, abduct and flex the hand/wrist.

Function of thenar and hypothenar muscles

Abduct the fingers.

Function of dorsal interossei muscles

Adduct the fingers.

Function of palmar interossei muscles

Flex at the MCP joint, extend PIP and DIP joints.

Function of lumbricals muscles

Rupture in any flexor digitorum profundus tendon (most common ring finger), resulting in pain, swelling and impaired flexion (absent if complete rupture).

Jersey finger

Hand deformity characterized by extension of the MCP joints and flexion of the DIP and PIP joints, often seen with distal lesions of the median or ulnar nerves. On proximal lesions deficit present during voluntary flexion of the digits.

Hand “clawing”

Hand deformity caused by a distal ulnar nerve lesion, characterized by extension of the MCP joints and flexion of the DIP and PIP joints at rest.

Ulnar claw

Hand deformity caused by a proximal median nerve lesion, characterized by extension of the MCP joints and flexion of the DIP and PIP joints when trying to flex them (making a fist).

Hand of benediction

Hand deformity caused by a distal median nerve lesion, characterized by extension of the MCP joints and flexion of the DIP and PIP joints at rest.

Median claw

Hand deformity caused by a proximal ulnar nerve lesion, characterized by extension of the MCP joints and flexion of the DIP and PIP joints when closing the hand.

OK gesture

Gluteus medius, gluteus minimus.

Abductors hip muscles

Adductor magnus, adductor longus, adductor brevis.

Adductors hip muscles

Gluteus maximus, semitendinosus, semimembranosus, long head of biceps femoris.

Extensors hip muscles

Iliopsoas (iliacus and psoas), rectus femoris, tensor fascia lata, pectineus, sartorius.

Flexors hip muscles

Gluteus medius, gluteous minimus, tensor fascia latae.

Internal rotation hip muscles

Ilipsoas, gluteus maximus, piriformis, obturator internus, obturator externus. .

External rotation hip muscles

Nerve that provides sensory innervation to the suprapubic region and motor innervation to the transversus abdominis and internal oblique muscles.

Iliohypogastric nerve (T12-l1)

Nerve that provides sensory innervation to the scrotum/labia majora and medial thigh, and motor innervation to the cremaster muscle.

Genitofemoral nerve (L1-L2)

Nerve that provides sensory innervation to the anterior and lateral thigh.

Lateral femoral cutaneous nerve (L2-L3)

Cause by pelvic trauma, tumors (bladder cancer), or during pelvic surgery, presents with decrease thigh medial sensation and impaired adduction.

Obturator nerve (L2-L4) injury

Nerve that descends through obturator canal that provides sensory innervation to the medial thigh and motor innervation to obturator externus, adductor longus, adductor brevis, gracilis, pectineus and adductor magnus muscles.

Obturator nerve (L2-L4)

Nerve that provides sensory innervation to the anterior thigh and medial leg, and motor innervation to the quadriceps, iliacus, pectineus, sartorius muscles.

Femoral nerve (L2-L5)

Nerve that provides motor innervation to the semitendinosus, semimembranosus, biceps femoris and addcutor magnus muscles, and splits into the common peroneal and tibial nerves.

Sciatic nerve (L4-S3)

Nerve that provides sensory innervation to the dorsum of the foot and motor innervation to peroneus longus and brevis muscles.

Superficial peroneal nerve

Nerve that provides sensory innervation to the webspace between the hallux and 2nd digit and motor innervetion to tibialis anterior muscle.

Deep peroneal nerve

Nerve that provides sensory innervation to the sole of the foot and motor innervation to biceps femoris (long head), triceps surae, plantaris, popliteus, flexor muscles of foot.

Tibial nerve (L4-S3)

Nerve that provides motor innervation to the gluteus medius, gluteus minimus, and tensor fascia latae muscles.

Superior gluteal nerve (L4-S1)

Nerve that provides motor innervation to the gluteus maximus muscle.

Inferior gluteal nerve (L5-S2)

Nerve that provides sensory innervation to the perineum and motor innervation to external urethral and anal sphincters muscles. Can be blocked with local anesthetic during childbirth using schial spinal as landmark.

Pudendal nerve (S2-S4)

Connects the lateral femoral condyle to the anterior tibia. Injury can be detected through the anterior drawer sign or the Lachman test.

Anterior Cruciate Ligament (ACL)

Connects the medial femoral condyle to the posterior tibia. Injury can be detected through the posterior drawer sign.

Posterior Cruciate Ligament (PCL)

Connects the medial condyle of the femur to the medial tibia. Injury can be detected through the valgus stress test.

Medial Collateral Ligament (MCL)

Connects the lateral condyle of the femur to the lateral tibia. Injury can be detected through the varus stress test.

Lateral Collateral Ligament (LCL)

Anterior talofibular ligament, anterior inferior tibiofibular ligament, posterior inferior tibiofibular ligament, posterior talofibular ligament, and calcaneofibular ligament.

Ankle ligaments

Paresthesia and weakness related to specific lumbosacral spinal nerves. It is often caused by herniation of the intervertebral disc. Positive straight leg raise, contralateral straight leg raise and reverse traight leg raise (femoral stretch).

Lumbosacral radiculopathy signs

Weakness of knee extension, hip flexion and decrease patellar reflex.

L3-L4 disc herniation

Weakness of dorsiflexion, foot inversion-eversion, difficulty in heel walking, and great toe extension.

L4-L5 disc herniation

Weakness of plantar flexion, difficulty in toe walking, decrease achilles reflex.

L5-S1 disc herniation

Transmit depolarization signals to the saroplasmatic reticulum to trigger the release of Ca and induce muscle contraction.

T-tubules

Specialized area of the muscle fiber membrane where the motor neuron releases acetylcholine to initiate muscle contraction.

Motor end plate

Basic unit of muscle contraction, extending from one Z line to the next Z line.

Sarcomere

Thick filament protein in muscle fibers that interacts with actin to generate muscle contraction.

Myosin

Thin filament protein in muscle fibers that interacts with myosin to generate muscle contraction.

Actin

Calcium release in muscle contraction

Binds to troponin C, shifting tropomyosin to expose the myosin-binding sites.

Sarco(endo)plasmic reticulum Ca2+ ATPase function

Reuptake of calcium into the sarcoplasmic reticulum, leading to muscle relaxation.

Red muscle fibers rich in myoglobin (mitochondra) that contract slow and uses oxidative phosphorylation metabolism (sustained contraction). Use on endurance training.

Type I muscle fibers

White muscle fibers poor in myoglobin (mitochondra) that contract fast and uses anaerobic glycolysis metabolism. Use on weight/resistance training (sprinting).

Type II muscle fibers

Process of bone formation where a cartilaginous model (made by chondrocytes) is first made and then osteclasts and osteoblast replace with woven bone and then remodel to lamellar bone. Bones of axial skeleton, appendicular skeleton and base of skull. In adults woven bone occurs after fractures and in Paget disease.

Endochondral ossification

Process of bone formation where woven bone is formed directly without a cartilague, later remodeled to lamellar bone. Bones of calvarium, facial bone and clavicle.

Membranous ossification

Bone cell responsible for building bone by secreting collagen and catalyzing mineralization in alkaline enviromment via ALP. Differentiates from mesenchymal stem cells in periosteum. Activity measured by bone ALP, osteocalcin, propeptides of type I procollagen.

Osteoblast

Bone cell responsible for dissolving bone by secreting H+ and collagenases. Differemtiastes from a fusion of monocyte/macrophage lineage precursors. RANK receports are stimulated by RANKL on osteoblast. Osteoprotegerin (OPG, RANKL decoy receptor) binds RANKL, to prevente RANK-RANKL interaction and decrease activity.

Osteoclast

Hormone that regulates calcium and phosphate levels in the blood and depending on levels has anabolic (building) and/or catabolic effects (osteitis fibrosa cystica) on bone.

Parathyroid hormone

Hormone that inhibits apoptosis in bone-forming osteoblasts and induces apoptosis in bone-resorbing osteoclasts. Causes closure of the epiphyseal plate during puberty. Deficiency increases cycles of remodeling and bone resorption increasing the risk of osteoporosis.

Estrogen

Condition characterized by pain near the medial epicondyle due to repetitive wrist flexion or idiopathic causes.

Medial (golfer’s) elbow tendinopathy

Condition characterized by pain near the lateral epicondyle due to repetitive wrist extension (backhand shots) or idiopathic causes.

Lateral (tennis) elbow tendinopathy

Usually caused by a fall on an outstretched hand or direct trauma to shoulder. Weakest point at the junction of the middle and lateral thirds (middle segment most common). Presents as shoulder drop, shortened clavicle (lateral fragment is depressed due to arm weight and medially rotaded by arm adductors).

Clavicle fractures

Compression of ulnar nerve at the wrist, often seen in cyclists due to pressure from handlebars, may also be seen with fracture/dislocation of the hook of hamate.

Guyon canal syndrome

Entrapment of the median nerve in the carpal tunnel, causing nerve compression → paresthesia, pain, and numbness in the distribution of the median nerve. Thenar eminence athophies but sensation spared (due to palmar cutaneous). Positive tinel sign and phalen maneuver. Associated with pregnancy, RA, hypothytoidism, diabtetes, acromegaly, dialysis-related amyloidosis, repetitive use.

Carpal tunnel syndrome

Also known as a boxer's fracture, common fracture caused by a direct blow with a closed fist. Most common in the 5th metacarpal.

Metacarpal neck fracture

Collection of pus in the iliopsoas compartment, may spread from adjacent structures or through the bloodstream. Associated with Crohn disease, diabetes, immunocompromised states. Presents as flank pain, fever, inguinal mas, positive psoas sign. Labs: leukocytosis. CT/MRI: focal hypodense lesion within muscle plane. Treatment: drainage and antibiotics.

Psoas abscess

"Unhappy triad"

Common knee injury in contact sports involving damage to the ACL, MCL, and medial meniscus. Involvement of lateral meniscus is more common. Presents with acute pain and signs of joint instability.

Inflammation of the prepatellar bursa in front of the kneecap. Caused by repeated trauma or pressure from excessive keeking (mechanics, carpet layers, plumbers, gardener).

Prepatellar bursitis

Collection of synovial fluid between the gastrocnemius-semimembranosus bursa commonly communicating with synovial space and related to chronic joint disease (eg, osteoarthritis, rheumatoid arthritis). Mass that disappears on flexion of the knee.

Popliteal cyst (Baker cyst)

Inflammation of the costochondral or costosternal junctions, presents with sharp, positional chest pain and focal tenderness to palpation. More common in younger females.

Costochondritis

Noninflammatory thickening of abductor pollicis longus and extensor pollicis brevis causing pain and tenderness at radial styloid. Positive finkelstein test. Increase risk in new mothers, golfers, racquet sport players, “thumb” texters.

De Quervain tenosynovitis

Caused by fibroblastic proliferation, disordered type III collagen and thickening of superficial palmar fascia, due to overstimulation of the Wnt-signaling pathway, which helps regulate cellular proliferation, polarity, and differentiation. Commonly involves the fascia at the base of the ring and little fingers. Unknown etiology, most frequently seen in males >50 of Northern European descent.

Dupuytren contracture

Overuse injury of lateral knee that occurs primarily in runners. Pain develops due to friction of iliotibial band against lateral femoral epicondyle.

Iliotibial band syndrome

Increased pressure within fascial compartment of a limb → venous outflow obstruction and arteriolar collapse → anoxia, necrosis, rhabdomyolysis → acute tubular necrosis. Causes include significant long bone fractures, reperfusion injury, animal venoms. Presents with severe pain and tense, swollen comparments with passive stretch of muscles in the affected compartment. Increased serum creatine kinase and motor deficits are late signs of irreversible muscle/nerve damage.

Limb compartment syndrome

Also known as shin splints, common cause of shin pain and tenderness in runners and military recruits. Caused by bone resorption that outpaces bone formation in tibial cortex.

Medial tibial stress syndrome

Inflammation of plantar aponeurosis, characterized by heel pain, especially in the morning or after periods of inactivity, and tenderness. Associated with obesity, prolonged standing or jumping, and flat feet. Heel spurs often coexist.

Plantar fasciitis

Presents with dull, constant unilateral facial pain that worsens with jaw movement, otalgia, headache, TMJ dysfunction (eg, limited range of motion). Associated with trauma, poor head and neck posture, abnormal trigeminal nerve pain processing, psychological factors.

Temporomandibular disorders

Common elbow injury in children < 5 years caused by a sudden pull on the arm, where the immature annular ligament slips over the head of the radius. Injury arm held in slightly flexed and pronated position.

Radial head subluxation (nursemaid’s elbow)

Also called traction apophysitis. Overuse injury of quadriceps muscle groups (leg extension at the knee) in adolescents after a growth spurt, caused by repetetive strain and chronic avulsion of the secondary ossification center of the proximal tibial tubercle. Common in running and jumping athletes. Presents with progressive anterior knee pain.

Osgood-Schlatter disease

Overuse injury that commonly presents in young, female athletes as anterior knee pain, exacerbated by prolonged sitting or weight-bearing on a flexed knee.

Patellofemoral syndrome

Developmental dysplasia of the hip

Abnormal acetabulum development in newborns, resulting in hip instability/dislocation, commonly tested with Ortolani and Barlow maneuvers, confirm via ultrasound. Risk factor: Breech presentation.

Idiopathic avascular necrosis of the femoral head, commonly presenting between 5-7 years with insidious onset of hip pain that may cause a child to limp. More common in males (4:1). Initial x-ray often normal.

Legg-Calvé-Perthes disease

Classically presents in an obese young adolescent with hip/knee pain and altered gait. Increased axial force on femoral head → epiphysis displaces relative to the femoral neck. Diagnosed via x-ray.

Slipped capital femoral epiphysis

Incomplete fracture extending partway through width of bone following bending stress, bone fails on tension side, compression side intact.

Greenstick fracture

Axial force applied to immature bone, causing the cortex to buckle on the compression side and fracture while the tension side remains intact.

Torus (buckle) fracture

Failure of longitudinal bone growth resulting in short limbs, trident hand, membranous ossification is not affected (macrocephaly), frontal bossing, midface hypoplasia caused by a mutation of the fibroblast growth factor receptor 3 (FGFR3) gene which constitutive activation result in inhibit chondrocyte proliferation. Autosomal dominant with full penetrance.

Achondroplasia

Trabecular and cortical bone lose mass despite normal bone mineralization and lab values, most commonly due to increase bone resorption related to decreased estrogen levels, old age and cigarette smoking. Can be secondary to drugs (steroids, alcohol, anticonvulsants, anticoagulants, thyroid replacement therapy), or other conditions (hyperparathyroidism, hyperthyroidism, multiple myeloma, malabsorption syndromes, anorexia). Can lead to vertebral compression fractures (acute back pain, loss of height, kyphosis), fracture of femoral neck, and/or distal radius (colles fracture).

Osteoporosis

Treatment: Bisphosphanates, teriparatide, SERMs, denosumab (monoclonal antibody against RANKL). Prophylaxis: weight-bearing exercise and adequate Ca and vitamin D intake throughout adulthood.

Osteoporosis management