Musculoskeletal MRI

Goals What types of MR studies are available for evaluation of the musculoskeletal system? Considerations when ordering a study Remember one of the roles of the radiologist is as consultant to work with you in determining the best study for the patient’s needs (it’s in the job description)… talk to them! Most common pathologies for which MSK MRI is performed

Exam Types MRI without contrast MRI with contrast MR Arthrogram Most common Evaluation of ligaments, tendons, occult fracture, cartilage MRI with contrast Evaluation of bone or soft tissue tumor, osteomyelitis, abscess MR Arthrogram Evaluation of labrum, intercarpal ligaments

Body Part When ordering any study must have a ddx in mind, particularly with MRI (not a screening tool) Cannot perform an MRI of a whole extremity (time, pt motion, protocol issues) Must identify part to be imaged – be specific A joint, a bone (prox, mid, distal), a muscle (origin, belly, insertion) Must have plain radiograph FOV about 25cm.

Most Common Indications Occult fx or stress fx Early osteonecrosis – in pt with risk factors & pain, known AVN of one hip Osteomyelitis – plain film is insensitive (30-50% loss of bone density) BUT necessary for MRI interpretation, nucs has poor resolution Osteochondral lesion – evaluate stability Ligament/tendon injury – knee, shoulder, ankle > other jts Bone tumor – MUST HAVE X-RAY 1st, imperative in providing ddx on MRI (dx on x-ray, determine extent on MR) Soft tissue mass/muscle injury

Considerations when ordering an MRI Joint replacement in joint of interest – don’t do it Pacemaker – don’t do it Claustrophobia - sedation Unable to hold still/follow instructions – sedation Metal in area of interest (susceptibility artifact) – consult radiologist, may vary technique or recommend another study Metal not in area of interest ie. orbits (motion, overheating) If you only remember one thing, remember this: cannot do a PE protocol chest CT without contrast

Metal Artifact Small metal foreign body results in large area of signal void. Metal or gas = black hole.

General Principles Fluid, edema, inflammation is bright on T2 Fat is bright on T1 & T2 (can have fat sat) Blood is often bright on T1 Tendons & ligaments are black on all sequences Cartilage is bright on T2 Muscle is intermediate in signal Do not order an MRI for necrotizing fasciitis.

Pelvis & Hip – Normal Anatomy Joints – sacroiliac, pubic symphysis, hips Tendons – iliopsoas, gluteal, hamstrings, rectus femoris Bursa – trochanteric, iliopsoas Bones – evaluate for bone marrow replacing process (MM, mets), AVN, occult or stress fx Acetabular labrum – need intra-articular gadolinium

Femoral Head Osteonecrosis Groin pain Many predisposing factors: trauma (fem neck fx, dislocation), steroids, SLE, sickle cell dz, pancreatitis, alcohol abuse, Gaucher’s dz Increased risk of contralateral AVN, must evaluate other side, most sensitive study is MRI MRI: Early – bone marrow edema Later – geographic area of abnormal signal in the anterosuperior femoral head; double line sign on T2 Even later – subchondral collapse, femoral head collapse, degenerative joint dz Double line sign – indicates ischemic necrosis, inner line of high signal surrounded by a line of low signal, interface of dead and living bone, may be chemical shift artifact

Femoral Head Osteonecrosis

the other hip – 40% bilateral Anterior and superior femoral head

More examples of AVN

and more… Triple line sign?

Labral Tear Clicking, locking, pain with pivoting/twisting Traumatic (young), degenerative (older) or assoc. with femoroacetabular impingement (middle-aged) MRI: Anterosuperior or posterosuperior Linear high T2 signal Loss of triangular morphology Paralabral cyst MR arthrogram most sensitive study – contrast fills tear Femoroacetabular impingement – repetitive microtrauma from impingement of femoral head against acetabulum, associated with labral tears and cartilage defects, focal acetabular chondral lesions, focal underlying subchondral sclerosis, edema, cystic change

Knee – Normal Anatomy Anterior & posterior cruciate ligaments Medial & lateral menisci Medial collateral ligament Lateral ligamentous complex (lateral collateral, iliotibial band, biceps femoris) Extensor mechanism Normal variant (discoid meniscus)

Knee – Normal Anatomy

ACL Tear Sports injury, rapid stopping/starting/pivoting (skiing, soccor, football, basketball etc), anterior drawer sign on PE MRI: Disruption of fibers, high signal on T2 Pivot-shift contusions Anterior translation of tibia relative to femur Associated with MCL and medial meniscus injury – O’Donahue’s unhappy triad Associated with Segond fx (avulsion of mid third lateral capsular ligament from lateral tibial plateau)

ACL Tear

ACL Tear – Pivot shift contusion

PCL Tear Dashboard injury of flexed knee, posterior drawer sign on PE MRI: Disruption of fibers/thickened fibers Abnormal high T2 signal Avulsion at insertion on posterior tibia

PCL Tear

Meniscal Tear Joint line tenderness, clicking, locking MRI: High T2 signal in the meniscus extending to the articular surface longitudinal, radial, flap (flipped), oblique, bucket-handle Parameniscal cyst

Oblique Undersurface Tear w/ Parameniscal Cyst

Bucket-handle Tear Medial > lateral Diminutive meniscus Inner edge of meniscus is displaced medially into notch Double PCL sign

Bucket-handle Tear

Discoid Meniscus Predisposes to early degeneration and tear of meniscus Lateral >> medial MRI: Large meniscus, no longer C-shaped Bowtie should not be seen on ≥3 consecutive sagittal images (4mm)

Discoid Meniscus

Medial Collateral Ligament Tear Valgus stress Complete or partial tears affecting superficial and/or deep fibers MRI: Disruption of fibers with thickening & abnormal high signal Associated with ACL & medial meniscal tears Pellegrini-Stieda lesion – ossification at origin of MCL indicative of old tear Superficial fibers – medial collateral ligament proper Deep fibers – meniscofemoral & meniscotibial attachemnts

Medial Collateral Ligament Tear Pellegrini-Stieda lesion Indicates old MCL tear Ossification at origin of MCL from medial femoral condyle

Acute on chronic MCL tear

Patellar Tendon Tear Partial or complete Most commonly in proximal third of tendon at inferior pole of patella Plain film: patella alta MRI: Disruption of fibers, thickening & abn signal Fluid-filled gap, hemorrage or granulation tissue

Patellar Tendon Tear

Patellar Tendon Tear different patient

Jumper’s Knee (Patellar Tendinosis) Repetitive trauma MRI: Proximal third of patellar tendon (posterior fibers) Early – edema in peritenon Later - thickening & edema (inc T2) Even later – partial or complete tear +/- reactive osteitis in lower pole patella (edema) Reactive edema in adjacent fat pad

Jumper’s Knee Suprapatellar effusion. Normal lucency of Hoffa’s fat pad is obscured.

Jumper’s Knee

Osteochondral Lesion Young male, 50% have h/o trauma Lateral aspect of medial femoral condyle, talar dome, capitellum Plain film: area of sclerosis or bone/cartilage fragment in situ or defect with loose body in joint MRI necessary to determine stability and guide treatment (stable-heal spontaneously, unstable-surgery) MRI: Fragment composed of hyaline articular cartilage and underlying subchondral bone Unstable if fluid between fragment and donor site on T2

OCD

OCD

Ankle – Normal Anatomy Joints – tibiotalar, distal tibiofibular, subtalar (ant, middle, post), intertarsal Tendons – flexor (tibialis posterior, digitorum longus, hallucis longus), extensor (tibialis anterior, hallucis longus, digitorum), peroneus (longus, brevis), Achilles Ligaments – medial (deltoid), lateral (talofibular, talocalcaneal), syndesmotic, Lis-Franc Muscles, bones, plantar fascia Normal Variants – plantaris, accessory soleus Tom Dick & Harry Tom Hates Dick Plantaris muscle tendon runs along side the achilles in 90% of people, can be mistaken for achilles tendon tear.

Tarsal Coalition Lack of segmentation of two tarsal bones Most commonly calcaneonavicular or talocalcaneal (middle subtalar joint) 20% bilateral; pain, flat foot Cartilaginous, fibrous, osseous Plain film: anteater sign, continuous C sign, talar beak, pes planus MRI: Cartilaginous, fibrous or bony bridge between 2 tarsal bones Fibrous/cartilaginous - JSN, irregularity, sclerosis, bone marrow edema Bony – continuity of bone marrow and cortex

Talocalcaneal Coalition

Calcaneonavicular Coalition

Calcaneonavicular Coalition

Accessory Soleus Muscle

Accessory Soleus

… and OCD Stable or unstable?

Peroneus Brevis Split Tear Peroneus brevis is normally round and anterior to longus Tear most commonly at level of lateral malleolus MRI: C-shaped tendon Longitudinal split, peroneus longus may be interposed between two subtendons +/- fluid in tendon sheath (tenosynovitis)

Peroneus Brevis Split Tear Tom Talar dome Dick Harry Peroneus tendons Achilles

Stress Fracture 2 types of stress fractures: Fatigue fx – normal bone under abnormal stress (young marathon runner, military recruit etc…) Insufficiency fx – abnormal bone under normal stress (elderly osteopenic female, steroids etc…) Characteristic locations: 3rd metatarsal, tibial diaphysis, calcaneus, medial aspect femoral neck, sacrum Plain film: Cortical bone – periosteal rxn and/or endosteal thickening Cancellous bone - ill-defined sclerosis MRI: Low signal line on T1 High signal bone marrow edema on T2 Calcaneus – trabecular fractures perpendicular to long axis

Stress Fracture Hx: 28 yo female training for marathon. Pain with running, stopped with rest. Note normal residua of growth plate.

Stress Fracture

Stress Fracture Compare to normal physeal line.

Brachial Plexus – Normal Anatomy Ventral nerve roots of C5, C6, C7, C8 & T1 Coarse between anterior & middle scalene muscles, under clavicle, over 1st rib, adjacent to subclavian artery (post & sup) Normal MRI appearance: Fascicles well-defined with intervening fat

Brachial Plexus - Normal Cor T1 Sag T1

Brachial Plexopathy Pain in the shoulder radiating down arm Etiologies: radiation >60 Gy(breast, lung ca), metastatic disease (via axillary lymphatics), direct invasion by tumor (Pancoast’s, lymphoma), direct trauma, stretch injury MRI: Thickened fascicles with obliteration of the intervening fat planes Well-defined mass With diffuse thickening of fascicles favor infiltrative neoplasm or radiation fibrosis. With well defined mass favor mets.

Radiation-induced Brachial Plexopathy Which side is abnormal?

Radiation-induced Brachial Plexopathy Which number corresponds to the brachial plexus? What are the other 2 structures? 1 3 2 Subclavian artery Subclavian vein

Brachial Plexus Metastasis Cor & Sag T1

Brachial Plexus Metastasis Mass Subclavian artery Vein Pre and post-contrast cor T1 with fat sat

Shoulder – Normal Anatomy Rotator cuff Long head of the biceps brachialis tendon – intertubercular and intracapsular portions AC joint/impingement Glenoid labrum – triangular low signal on all sequences, serves to deepen glenoid fossa thereby stabilizing GH joint, attachment site of long head of biceps Myxoid degeneration, labral tear (alphabet soup), Bankart lesion Best evaluated with MR arthrography Shoulder MRI most commonly ordered for the evaluation of these structures. Of course there are other things we see and look at.

Normal Anatomy Normal rotator cuff, intra-articular and intertubercular long head of biceps, biceps anchor point. No contrast in subacromial/subdeltoid bursa. Normal communication of biceps tendon sheath with joint.

Rotator Cuff Tear Supraspinatus, infraspinatus, teres minor, subscapularis Pts > 40 yo, insidious onset of pain Spectrum: tendinopathy, partial and full thickness tear Etiology: degeneration (age, overuse, impingement), trauma, collagen vascular disease MRI: Tendinopathy – thickened tendon, increased signal on PD, intermed on T2 Partial tear – increased signal on T2, defect does not extend through cuff Complete tear – increased signal defect on T2 extending through RC from articular surface to bursal surface; fluid in subacromial/subdeltoid bursa Chronic tear – muscle atrophy Impingement – shape or configuration of acromion, AC joint DJD, mass etc…

Rotator Cuff Tear Supraspinatus

Rotator Cuff Tear Supraspinatus

Supraspinatus Tendinopathy Underlying degenerated tendon as evidenced by thickening and abnormal signal

Labral Tear Young pts <40 yo, pain, instability Best evaluated with MR arthrogram MRI: Linear high T2 signal within substance of labrum Diffuse high signal (crush injury) Absent or small labrum Detached labrum Mimics: Undercutting of articular cartilage between labrum and glenoid Interposed synovial recess (sulcus) Sublabral foramen/hole (detached anterosuperior labrum)

Labral Tear

Labral Tear? NO Undercutting of cartilage between labrum & glenoid Interposed synovial sulcus Contrast follows contour of glenoid (points medially)

Hillsach’s and Bankart Lesions History of anterior shoulder dislocation Hillsach’s – impaction fracture of posterior superior humeral head Bankart – anterior inferior labral avulsion w/ rupture of periosteum, many variants Bony Bankart – fracture of anterior glenoid MRI: Impaction fracture of posterosuperior humeral head (not round on 1st three axial images) Anterior labral tear or variant (best evaluated with arthrography) Many Bankart variants… alphabet soup.

Hillsach’s and ALPSA ALPSA – anterior labroligamentous periosteal sleeve avulsion, medial displacement of labrum with periosteal stripping (intact periosteum), medialized Perthes Perthes – normal position of labrum, periosteum stripped medially, but intact

Elbow – Normal Anatomy Tendons – biceps, brachialis, triceps, common flexor and extensor origins Ligaments – ulnar and radial collateral Joints – elbow, proximal radioulnar Olecranon bursa

Olecranon Bursitis Painless mass following acute direct trauma or recurrent trauma; assoc with systemic dz Distension of olecranon bursa (synovial sac) with fluid MRI: In superficial soft tissues adjacent to olecranon process and triceps insertion mm – cm in size High signal on T2, possible rim enhancement +/- hemorrhagic debris

Olecranon Bursitis

Lateral Epicondylitis Insidious onset of lateral elbow pain with activity Overuse syndrome – repetitive varus stress Chronic tendinopathy at common extensor origin, predominantly involving the extensor carpi radialis brevis tendon Partial avulsion with scar formation Plain film: normal or spur at lateral epicondyle MRI: Thickening of tendon with increased signal on T1 & T2

a.k.a Tennis Elbow Tendinosis with small tear

Lateral Epicondylitis Involves both deep and superficial fibers of extensor carpi radialis longus

Wrist – Normal Anatomy Bones – distal radius & ulna, carpus, MT’s Joints – DRUJ, radiocarpal, intercarpal Tendons – flexor & extensor Nerves – median & ulnar Ligaments – intercarpal (instability) Masses – most common ganglion cyst

Status post trauma Where is the fracture?

Occult Distal Radius Fx