Bursae of the Shoulder

Anatomical Diagram (THIEME Atlas of Anatomy)

The Major Bursae

1. Subacromial Bursa (Most Clinically Important)

• Located between the coracoacromial arch (above) and the rotator cuff / supraspinatus tendon (below)
• Roof: adherent to undersurface of deltoid, acromion, and coracoacromial ligament
• Floor: adherent to the rotator cuff (especially supraspinatus)
• Lubricated by synovial fluid; surrounded by a layer of peribursal fat
• Its role is to reduce friction on the supraspinatus tendon during abduction/elevation
• Does not normally communicate with the glenohumeral joint - but communication develops in full-thickness rotator cuff tears

2. Subdeltoid Bursa

• Located between the deltoid muscle and the rotator cuff
• Consistently communicates with the subacromial bursa - together they are often referred to as the subacromial-subdeltoid (SASD) bursa, one large continuous structure
• Functions together with the subacromial bursa to allow frictionless gliding of the humeral head and rotator cuff tendons beneath the coracoacromial arch

3. Subcutaneous Acromial Bursa

• Located superficially over the acromion, just beneath the skin
• Smaller and less clinically relevant

4. Subcoracoid Bursa (Coracoid Bursa)

• Located between the subscapularis muscle and the coracoid process
• Does not normally communicate with the glenohumeral joint
• Separated from the subscapular recess by an identifiable fibrous septum
• May communicate with the subacromial-subdeltoid bursa in about 10% of patients
• Not normally visible on MRI unless distended by fluid

5. Subtendinous Bursa of Subscapularis (Subscapular / Superior Subscapular Recess)

• Located between the anterior surface of the scapula and the subscapularis muscle
• Also called the subscapular bursa or superior subscapular recess
• Frequently communicates with the glenohumeral joint (through the subscapularis recess, which is a normal variant)

6-8. Smaller Bursae (Minor, Not Routinely Seen on MRI)

• Infraspinatus bursa - near the infraspinatus tendon insertion
• Teres major bursa - near the teres major tendon
• Pectoralis major bursa - near the pectoralis major tendon

Summary Table

Key Clinical Points

• The subacromial bursa is the target of steroid injections for subacromial impingement syndrome and bursitis
• In rotator cuff tears (especially full-thickness), fluid communicates between the glenohumeral joint and the subacromial-subdeltoid bursa - this is detectable on MRI/ultrasound
• Subacromial impingement syndrome encompasses subacromial bursitis, rotator cuff tendinitis, supraspinatus tendinitis, and painful arc syndrome

3 Main Reasons:

1. 🧲 Powerful Magnetic Field (Projectile Effect)

• MRI machine 1.5 Tesla ya 3 Tesla ka magnetic field generate karti hai — ye Earth ke magnetic field se 30,000 - 60,000 guna zyada strong hota hai
• Mobile phone mein iron/steel/metal components hote hain (camera lens, battery casing, screws)
• Ye phone ko ek missile ki tarah machine ki taraf khich leta hai — isse patient ko serious injury ho sakti hai
• Isse "projectile effect" kehte hain

2. 📱 Electronic Interference

• MRI machine radio frequency (RF) waves use karti hai images banane ke liye
• Mobile phone ke electronic circuits in RF waves ko disturb kar dete hain
• Isse MRI image mein artifacts (distortions/errors) aa jaate hain — diagnosis galat ho sakti hai
• Phone khud bhi damage ho sakta hai permanently

3. 🔥 Heating Effect

• RF energy se phone ke metal parts aur circuits garam ho jaate hain
• Isse patient ko burns ho sakte hain agar phone paas mein ho
• Battery overheat ya explode bhi kar sakti hai

Kitna Powerful Hota Hai Magnetic Field?

Simple Samajh ke liye:

MRI machine ko "always-on magnet" samjho. Jaise ek industrial electromagnet crane hoti hai jo cars uthati hai - waise hi ye chhoti chhoti metal cheezein apni taraf khich leti hai, chahe current band ho ya on ho - kyunki MRI ka magnet superconducting hota hai jo kabhi band nahi hota.

Sar/Head par Direct Effects:

1. 🔥 RF Heating (Radio Frequency Heating)

• MRI ke dauran RF waves continuously emit hoti hain
• Ye waves brain tissue aur skull mein heat generate karti hain
• Agar phone paas mein ho toh localized heating badh jaati hai
• Result: Headache, tissue damage, burns possible hain

2. ⚡ Induced Current

• Strong magnetic field metal components mein electric current induce karta hai
• Agar phone sar ke paas ho toh ye induced current brain tissue tak transfer ho sakta hai
• Ye seizures ya nerve stimulation cause kar sakta hai (rare but possible)

3. 💥 Projectile Injury (Sabse Dangerous)

• Agar phone haath mein hai aur magnetic field khichti hai -
• Phone bullet ki speed se machine ki taraf jaata hai
• Beech mein jo bhi aaye - sar, face, aankhein - serious fracture, laceration, internal bleeding ho sakti hai
• Ye sabse bada danger hai

4. 📡 Image Artifact

• Sar ki MRI le rahe hain toh phone ki wajah se brain images distort ho jaayengi
• Tumor, bleed, ya koi bhi pathology miss ho sakti hai
• Diagnosis completely wrong ho sakti hai

Real Incidents jo ho chuke hain:

• 2001, New York: Ek bachche ki MRI ke dauran oxygen cylinder room mein ghus gayi - wo missile ban gayi, bachche ki death ho gayi
• Multiple cases mein phones, keys, scissors se patient ko serious injuries hui hain

Short Answer:

SAR Kya Hota Hai?

SAR = Wo rate jis par human body electromagnetic radiation (RF energy) ko absorb karti hai

Unit:

SAR ke 2 Contexts Hain:

📱 1. Mobile Phone SAR

• Har mobile phone RF radiation emit karta hai
• SAR batata hai ki 1 kg body tissue kitni RF energy absorb karta hai per second
• Ye head aur body dono ke liye measure hota hai

Safe Limits (International Standards):

✅ Jitna kam SAR, utna better - less radiation absorbed by body

Phone ka SAR kahan dekhein:

• Phone Settings > About Phone > SAR value
• Phone ke box par likha hota hai
• Ya *#07# dial karo - India mein SAR value show hoti hai

🏥 2. MRI SAR (Sabse Important in Medical Context)

• MRI ke dauran machine RF pulses use karti hai
• Ye RF energy patient ke body mein heat generate karti hai
• SAR monitor karna mandatory hai MRI mein - patient safety ke liye

MRI SAR Limits (IEC 60601-2-33):

MRI mein SAR badhane ke factors:

• Higher field strength (3T > 1.5T - zyada SAR)
• More RF pulses (fast sequences)
• Patient ka weight (bada patient = zyada SAR)
• Implants ya metal paas mein hona

MRI mein high SAR ke effects:

• Body temperature increase hona
• Burns (especially implants ke paas)
• Tissue damage

Simple Comparison:

Key Point:

MRI mein agar phone andar ho - toh phone ka khud ka SAR + MRI ka SAR dono combine ho jaate hain - double radiation absorption hoti hai head mein - isliye aur bhi dangerous hai! ☢️