Rotator cuff interval - Anatomy

Rotator cuff interval
Triangular shape. Bordered by:
1. Coracoid process
2. Subscapularis muscle/tendon (SSc)
3. Supraspinatus muscle/tendon (SSp)

Houses:
1. (Intra-articular portion of) Long head of biceps tendon (LHBT)
2. Coracohumeral ligament (CHL) (superficial)
     - Variants: absent CHL
     - Originate from postero-lateral of coracoid process
3. Superior glenohumeral ligament (SGHL) (deep)
     - Variants: absent SGHL

Important structures:
1. Medial-pulley-complex (MPC)
     - Medial bundle of CHL + SSc + SGHL
     - Medial to the LHBT
     *Disruption causes subluxation of the LHBT medially

2. Lateral-pulley-complex (LPC)
     - Lateral bundle of CHL + SSp
     - Lateral to the LHBT

3. Rotator cable (part of lateral-pulley-complex)
     - Suspense and stabilise the shoulder joint
     - Thin fibrous band extension from CHL and some of SGHL
     - Traverse deep to SSp and ISp, superficial to joint capsule

4. Capsulo-ligamentous biceps pulley / Superior-complex layer (SCL)
     - CHL + SGHL + Capsule
     - Forms the roof of intra-articular portion of LHBT (proximal to the transverse humeral ligament)

5. Rotator crescent
     - An area between rotator cable and the SSp insertion
     - Poorly vascularised area
     - Gets thinner with age




Reference: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5568533/

Pulled elbow ultrasound

Pulled elbow

aka Nursemaid's elbow
Most common in 1-4 years old

Patho-mechanism
- Traction along the long axis of forearm resulting in subluxation / slippage of annular ligament in between radial head and humerus (capitellum)
- Supinator muscle and annular ligament is slipped over the radial head
- Supinator muscle entraps the radio-humeral joint

Ultrasound examination
Absence of annular ligament in normal position (Most useful sign)
Displaced annular ligament into the radio-humeral joint with enlarged synovial fringe
Abormal shape of the supinator muscle
"J-sign" : supinator muscle and annular ligament trapped in the radio-humeral joint
Look out for fractures as a DDx.


Reference:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5052830/#!po=32.1429
Minagawa H. Diagnostic and interventional musculoskeletal ultrasound. J Jpn Orthop Assoc 2012; 86(11): 1057-64.

Elbow PosteroLateral Rotatory Instability Stages

Postero-lateral Rotatory Instability (PLRI) of the elbow

The most common pattern of recurrent elbow instability.
Three stages:

Stage 1:
- Tear / Insufficiency of LUCL
- Postero-lateral subluxation of the radius/ulna on humerus

Stage 2:
- "Perched" dislocation of radius/ulna on humerus
- Coronoid process perched under the tochlea
- Disruption of anterior and posterior joint capsule
- Disruption of the LUCL

Stage 3:
- Complete dislocation of elbow radius/ulna on humerus
- Coronoid process dislocated, positioned behind humerus.
- LUCL, RCL, joint capsule disruption
- MCL disruption
     - Stage 3A: Posterior bundle disrupted ; Anterior bundle intact
     - Stage 3B: Posterior and Anterior bundles disrupted
     - Stage 3C: Disrupted ligaments and tendons on both medial and lateral aspects


Reference:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6447645/#!po=73.8636
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5443138/