Imaging Annular Ligament of the elbow

It is a ring surrounding radial head, attached to anterior and posterior margins of radial notch of ulna
Complex formed from capsule, lateral collateral ligament complex (LCLC) and supinator muscle
Tight superiorly, loose inferiorly
Best shown on axial and sagittal MRA
Anterior attachment: single band, broader
Posterior attachemnt: single to 4 bands (hence should not be mistaken for pathology)
On sagittal: funnel shaped, wider proximally, and narrow distally at radial neck

Nursemaid's elbow:
Transverse tear of the distal attachment of annular ligament is likely to be the first step.

Reference:
1. Sanal HT et al. Annular Ligament of the Elbow: MR Arthrography Appearance With Anatomic and Histologic Correlation. AJR 2009; 193:W122-W126

Trochanteric bursitis (greater tuberosity pain syndrome)

Anatomy:
Facets on greater trochanter: anterior (gluteus minimus), lateral , posterior and postrosuperior
Gluteus minimus attaches to anterior facet
Gluteus medius attaches to lateral and posterosuperior facets
Bursae: trochanteric bursa, subglutues minimus bursa, sub gluteus medius bursa

Pathology:
Tear in the abductor tendon
Abductor tendinopathy
Bursitis

MRI:
Increased T2 signal within the tendon
Partial or full thickness tear
Muscle atrophy in chronic tears
GLuteus medius is more frequently involved


Link:
http://www.radsource.us/rf/RADS/Internal.aspx?PID=486

Internal impingement of the shoulder

Also called posterosuperior impingement
Impingement of posterior supraspinatus or anterior infraspinatus or both between humeral head and posterior glenoid during extreme abduction and external rotation (overhead movement)
Secondary to abnormality in the supraspinatus, infraspinatus, posterosuperior labrum or humeral head or combination of above

Arthroscopic criteria:
Posterosuperior labral fraying or tear
Articular irregularity of supraspinatus or infraspinatus or both
Contact of cuff tendons on posterosuperior glenoid in abduction and external rotation

MRI:
Irregularity of undersurface of rotator cuff - abnormal signal, tears or both
Capsular laxity with anterior translation of humeral head
Fraying or tear or both of posterosuperior labrum
Cyst like change posterolateral humeral head at attachment of infraspinatus tendon and posterior fibers of supraspinatus (may be secondary to impaction or traction).

References:
1. Giaroli EL et al. MRI of Internal Impingement of the Shoulder. AJR 2005; 185:925-929

iliopsoas bursal injection

Done in supine position under ultrasound guidance.
3.5 curvilinear probe or up to 7.5 MHz linear probe. Higher frequency probes are unlikely to be useful.
Visualize femoral vessels and iliopsoas tendon.
Lateral approach
Long blue needle, or black spinal needle deep to iliopsoas tendon at iliopectineal eminence.
Inject 1% lidocaine +/- % Bupivicaine and 1 ml Kenalog/triamcinolone.
Risk of transient femoral nerve palsy

Reference:
http://www.ajronline.org/cgi/content/full/185/4/940. Diagnostic and Therapeutic Use of Sonography-Guided Iliopsoas Peritendinous Injections AJR 2005; 185:940-943

Pelvis

Image 1:
Findings: Right anterior inferior iliac spine avulsion fracture
Lesson: Even in frog leg views, look at all the bones other than femoral head. In all adolescents, look for avulsion injuries

Medial epicondylitis

= golfer's elbow, pitcher's elbow, medial tennis elbow
Middle age
Far less common than lateral epicondylitis
Pain in the anterior aspect of the medial epicondyle - flexor-pronator tendon group
Most commonly involved tendons: pronator teres and flexor carpi radialis
May be associated with ulnar neuropathy

MR:
Coronal FS T2 is best sequence
Increased signal and thickening of the flexor-pronator group
Complete/ incomplete tendon tear
Tendinosis/ tendinopathy: Int signal on T1, no increased signal on T2
Pronator teres muscle strain
Increased signal in anconeus
Epicondylar edema

Associated findings:
Partial MCL tear
Synovitis
Lateral impaction injury - subchondral cyst, subchondral sclerosis, loose bodies
Ulnar neuritis - increased signal and thickening on FS PD in cubital tunnel

Management:
Conservative
Surgical release
Transposition and decompression of ulnar nerve

Pitfalls:
Beware of previous infections

Causes of groin pain (sports)

Hernia
FAI
Labral tear
iliopsoas tendinitis
iliotibial band syndrome
rectus abdominis strain
adductor muscle-tendon dysfunction
rectus abdominis - adductor longus aponeurosis tear
stress fracture
apophysisits

Reference:
Omar I M et al. Athletic Pubalgia and "Sports Hernia": Optimal MR Imaging Technique and Findings. RadioGraphics 2008;28:1415-1438

Imaging labrum

Clinical features:
Anterior inguinal pain, Painful clicking, Transient locking, Giving away
Pain on flexion and internal rotation, Audible click
No history of significant trauma
High association with developmental dysplasia

MR normal labrum:
Uniform low signal on T1, slightly higher on GE
Intermediate signal may be seen at junction of labrum and cartilage
Intermediate intralabral signal on T1 may be seen in aymtomatic labra (58%)

Pathology:
Most common in anterosuperior labrum
Posterosuperior tears are more common in young
Seen as contrast interposed at labral-acetabular junction
Displacement of labrum may be seen
Associated with chondral defects inn 30%

Signs of labral pathology on MR:
Contrast interposed between labrum and acetabulum
Blunting of inner margin
Deformation
Distortion
Detatchment
Displacement
Perilabral cysts

References:
Cheryl A. Petersilge. Chronic Adult Hip Pain: MR Arthrography of the Hip. Radiographics. 2000;20:S43-S52

Q angle

Line 1: from ASIS to central patella
Line 2: from central patella to tibial tubercle
Normal: 14 degree in male, 17 in female
Increased in femoral antecversion, external tibial torsion, genu valgum, tight lateral retinaculum

Sitting Q angle: more than 8 degree is abnormal

Osteochondritis Dissecans of the Capitellum

Adolescents and young adults
Common in male baseball pitchers or female gymnasts
Lateral elbow pain
Most in anterolateral aspect of capitellum
50% heal conservatively

References:
Kijowski R et al. MRI Findings of Osteochondritis Dissecans of the Capitellum with Surgical Correlation. AJR 2005; 185:1453-1459