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/

Dallas classification for discography

Dallas classification

A classification system to assess the degree of annular tear/fissuring
*The term "tear" is not recommended in imaging reporting according to 2014 consensus of the North American Spine Society, American Society of Spine Radiology & American Society of Neuroradiology

Assess via CT Discogram following Discography.
Dallas classification evolves from the initial 4 grades up to 7 grades over time
*Grade 5 annular fissure can be determined during Discography

Grade 0:
- Normal contained nucleus pulposus

Grade 1:
- Contrast leak into the inner 1/3 of annulus

Grade 2:
- Contrast leak into the inner 1/3 & middle 1/3 of annulus

Grade 3:
- Contrast leak into the inner, middle and outer 1/3 of annulus (ie entire thickness of annulus), less than 30% circumference

Grade 4:
- Contrast leak to circumferentially more than 30% of the annulus

Grade 5:
- Contrast leak into epidural space

Grade 6:
- Disc sequestration

Grade 7:
- Diffuse annular tear in disc degeneration


Reference:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3097593/#!po=45.0000

Ramsay-Hunt Syndrome

AKA Herpes zoster oticus

Aetiology agent:
- Herpes zoster virus
Latent (Reactivation) infection at geniculate ganglion of virus from past infection (chicken pox)

Structure affected: 
- Facial nerve (CN VII)
- +/- Vestibulocochlear nerve (CN VIII)

MRI:
- Contrast enhancement of the CN VII canalicular segment. Normally do not enhance in this area.
- Asymmetric contrast enhancement of the geniculate ganglia labyrinthine, tympanic and/or mastoid.
- +/- Vestibular & Cochlear nerve contrast enhancement.
- +/- Pontine colliculus facials contrast enhancement.

Symptoms:
Classic triad
- Vesicles along the facial nerve distribution (ear, EAC, face, palate, tongue) AND/OR
- Ipsilateral hemi-facial weakness / paralysis AND/OR
- Ear (otic) pain
Others:
- Tinnitus, sensorineural hearing loss, vertigo (vestibulocochlear nerve CNVIII involvement)
- Unable to close eye (ipsilateral)
- Altered / Loss of taste perception
- Dry mouth & eyes

Complication:
- Facial paralysis (can be permanent)
- Hearing loss (can be permanent)
- Post-herpetic neuralgia
- Meningo-encephalitis

Rx: EARLY TREATMENT!!
- Antiviral medications
- Short term high dose Steroids
- Benzodiazepine
- Analgesia
- Eye-moisturiser

Hallux valgus

Angle between longitudinal axis of 1st metatarsal bone and 1st proximal phalanx >15 degrees deviated laterally.

Associated with
- Foot pronation
- Flat foot

Atrophy of the intrinsic plantar muscles:
- Abductor hallucis (AbdH)
- Flexor hallucis brevis (FHB)
* Not observed in Flexor digitorum brevis (FDB)

Thickening of Plantar fascia:
- Anterior / Middle / Posterior Plantar fascia

Complication:
- Bunion formation
- Progress to Hallux rigidus

Mayfield classification

Mayfield classification

Classification for carpal bone instability (peri-lunate injuries)

Mechanism of injury:
- Fall on out-stretched hand (FOOSH)
- Injuries always start from Radial side to Ulnar side, therefore Type 1 -> 4 = injuries progressively from Radial to Ulnar side
- A combination of 3 pressure load (listed below), causes rotatory force around the waist of capitate.

1. Carpus extension (the principal load)
2. Wrist ulnar deviation
3. Intercarpal supination

Important ligaments in perilunate injuries
Purple: Radio-scapho-capitate ligament
Blue: Radio-triquetral ligament
Yellow: Ulno-triquetral ligament

Imaging:
Radiographs are insensitive except for frank perilunate dislocation / lunate dislocation
Clues:

1. Scapho-lunate dissociation 
1. Scapho-lunate interval 2-4mm: Suspicious ; >4mm: Definite on AP view
2. Scapho-lunate angle >63 degree on Lateral view
2. Scaphoid bone fracture
3. Radial styloid fracture
4. Luno-triquetral dissociation
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5. Triquetrum fracture
6. Capitate fracture
7. Gilula's arch disruption / step deformity
8. "Piece of pie" sign for perilunate dislocation / lunate dislocation
9. "Spilt tea-cup" sign for lunate dislocation

CT better at depicting avulsion injury, step deformity

MRI / MR Arthrography better at depicting bone marrow oedema (trabecula fracture in instance of trauma), ligamentous integrity

Type 1:

*Area of disruption: Scapho-lunate articulation
- Extension + Ulnar deviation => Radio-scapho-capitate ligament tear/avulsion
- Further force causes => Scaphoid  fracture / Scapho-lunate ligament tear

Mayfield type 1: Scapho-lunate articulation disruption

Type 2:

*Area of disruption: Scapho-lunate + Capito-lunate articulations
- Type 1 injuries plus:
- Capito-lunate ligament tear/avulsion OR Capitate fracture

Mayfield type 2: Scapholunate & Capitolunate articulation disruptions

Type 3:

*Area of disruption: Scapho-lunate + Capito-lunate + Luno-triquetral articulations
- Type 1 + Type2 plus:
- Lunotriquetral ligament tear/avulsion OR Triquetrum fracture
- Resulting in peri-lunate dissociation ie Dissociation of lunate from (1) Scaphoid (radial side) ; (2) Capitate (distal articulation) ; (3) Triquetrum (Ulnar side).
- +/- Peri-lunate dislocation ensues ie Lunate is still articulating normally with radius, whereas the rest of the carpal bones are dislocated dorsally.

Mayfield type 3: Scapholunate, Capitolunate & Lunotriquetral articulation disruptions

Type 4:

*Area of disruption: Scapho-lunate + Capito-lunate + Luno-triquetral + Radio-lunate articulations
- Radio-lunate ligament tear AND
- Relocation of the carpal bones (except Lunate) back to normal position AND
- Lunate is tilted and displaced to volar aspect, through the space of Poirier.

Mayfield type 4: All 4 articulations of the lunate bone disrupted

Reference: https://doi.org/10.1016/j.crad.2019.10.0160009-9260/