Quadrangular/Quadrilateral space syndrome
– Posteroinferior paralabral cyst (arrow) extending into the quadrangular space
– Teres minor mild fatty infiltration – atrophy (circle)
– Neurovascular compression syndrome of the posterior humeral circumflex artery (PHCA) and/or the axillary nerve or one of its major branches in the quadrangular space
– Multiple causes of compression: fibrotic bands, ganglion/cysts, aneurysms, tumours
– MRI may demonstrate atrophy and/or denervation edema of the teres minor and/or deltoid muscles
– Differential diagnosis: Parsonage-Turner sd, disuse atrophy

Features

There are three cardinal features:
– Bilateral undescended testicles
– Dilated urinary tract
– Deficient abdominal wall musculature.

These manifestations place patients with prune belly syndrome at risk for testicular malignancy, infertility, urinary tract infections, and renal failure.

The Prune Belly syndrome is also known as:
– Eagle-Barrett syndrome
– Abdominal musculation syndrome

X-Ray: No obvious fracture.

MRI:
– Bone marrow heterogeneous oedema within the third metatarsal diaphysis (hypointense on T1W image, hyperintense on Proton Density (PD) FatSat image).
– Linear low signal intensity fracture identified in all sequences.
– Periosteal reaction due to callus formation. Periosteal thickening and enhancement (contrast administration is not necessary for diagnosis).
– Surrounding soft-tissue oedema (adjacent fat and interosseous muscles).

Metatarsal stress fracture (“march fracture”)

– Stress fractures are caused by overuse and repetitive activity.
– Everyday activities may result in a stress fracture if there is any disease or therapy that weakens the bone such as osteoporosis or long-term use of steroids (bone insufficiency: long-term treatment with steroids in this case).
– Classically affects the 2nd or 3rd metatarsal of the foot “march fracture”: named after its prevalence in soldiers who often undertake repeated and prolonged periods of walking as part of their training or work.
– Bone changes are usually not evident on X-rays before 10 to 21 days following the injury. May not be visible for several weeks later, until callus bone formation (the sensitivity range, for detecting stress fractures on initial examinations, is 15-35%; it increases to 30-70% at follow-up studies due to bone reaction).

MRI findings:
– The fluid-sensitive sequences (T2-weighted images with chemically selective fat suppression or STIR sequences) are very useful for the detection of the earliest changes of stress reaction, such as periosteal reaction, muscle, or bone marrow oedema.
– T1-weighted sequences depict the anatomy and more advanced stress-related findings.

Grading based on MRI (Arendt and Griffiths)🙂
1: Mild – moderate periosteal oedema on STIR, no marrow changes.
2: Moderate – severe periosteal oedema on STIR + marrow changes on T2-weighted.
3: Grade 2+ marrow changes on T1-weighted.
4: Fracture line visible.

Findings

CT: Low attenuation area involving the posterior aspect of the deltoid muscle and the lateral aspect of the pectoralis major muscle. Superficial and deep fascia edema. No enhancing walls neither gas is seen.

MRI: Postcontrast T1FS images show hypointense unenhancing central muscle fibers surrounded by thick rim enhancement involving the posterior deltoid, teres minor, and pectoralis major muscles . Thickened and hyperenhancing adjacent fascia and reactive muscle edema are also noted.