Os Acromiale
Definition
- Non-union of one of the acromion ossification centres
Aetiology
- Acromion arises from 4 separate ossification centres
- From anterior to posterior can be remembered as PASTA
- Normally fuse between 18 & 25 years old
- Preacromium
- Mesoacromium
- MetaAcromium
- Basiacromium (at base)
- Type of Os Acromiale
- Described by ossification centre anterior to non-union
- Mesoacromium is the most common
- Failure of fusion between meso & metaacromium
Clinical Features
- Most asymptomatic – incidental findings
- May cause:
- Impingement
- Cuff weakness
- Pain
Diagnosis
History
- Usually insidious and atraumatic
Examination
- Pain over acromion
XR
- Axillary lateral view
- Screen other side – 60% incidence of bilaterality
MRI
- Is non-union ‘active’ – high signal, effusion/fluid etc.
- Other pathology
Management
Non-surgical
- Pain relief
- Injection – diagnostic +/- therapeutic
Surgical
Fragment excision
- Poor results unless for small irreparable os acromiale
ORIF of Fragment & Bone Grafting
- With cannulated screws or tension band wire
- Bone grafting of non-union site
Arthroscopic treatment
- ASAD
- Treat other pathology
- Excision – for small unstable fragments
Outcomes
- Best if proven to be symptomatic and treated with ORIF & bone grafting
Scapula Winging
Definition
- Abnormal posture and motion of the scapula
- Causes pain and dysfunction due to altered kinematics & power
Aetiology
Primary
- Neurologic deficit of one of the three primary scapula stabilisers
- (SA, Trapezius, RMa & RMi)
- Uncommon
Secondary
- Due to other shoulder pathology
- GHJ, Bursal, Cuff, osteochondroma, etc.
- More common
Pathoanatomy
Scapula
- Largest bone of shoulder girdle
- Covers 2nd – 7th ribs
- Inferior, lateral, and superior angles
- Lies 30° anteriorly rotated & 10° flexed at rest
- Gives attachment to 17 muscles
- Scapulothoracic, Scapulohumeral, Rotator cuff muscles
Scapulothoracic Stability
- Muscle attachments
- ACJ & Coracoclavicular ligaments
- Allows huge range of movement with little constraint
- Movements of scapula
- GHJ: ST motion 2:1 during shoulder abduction
- Scapula moves glenoid & acromion to prevent impingement
- Facilitates large ROM
- Elevation: Trapezius, Levator Scapulae
- Protraction: Serratus Anterior, Pec Major & Minor
- Retraction: Rhomboids
Serratus Anterior
- Large flat muscle
- Origin first 9 ribs
- 3 separate groups of fibres – upper, middle, lower
- Inserts on medial border scapula
- Contraction = protraction of scapula
Nerve Supply
- Long Thoracic Nerve
- C5 & C6 contribution early → supplies upper fibres
- C7 contribution below middle scalene → supplies middle & lower fibres
- Courses under clavicle & 1st rib; then on chest wall in mid axillary line
- Length of course is 20 cm and superficial throughout
- Vulnerable to injury
- Usually blunt or stretch injury
- May be from C5-7 root problem
- Chest drain insertion
- Palsy = Medial Winging
- Most common cause of primary winging
Trapezius
- Superficial muscle
- Origin: Occipital protuberance, Ligamentum nuchae & spinous processes of all cervical & thoracic vertebrae
- Attaches to superior and medial border scapula
- Elevates and tilts scapula medially
Nerve Supply
- Spinal Accessory Nerve (Cranial Nerve XI)
- Only cranial nerve to exit and re-enter skull
- Enters Posterior triangle under SCM upper 1/3 & mid 1/3 border
- Superficial and vulnerable to injury
- Usually penetrating iatrogenic injury
- Palsy = Lateral Winging
Rhomboids
- Minor is superior to major
Minor
- Origin: C7 & T1 spinous processes
- Inserts on medial border at level of scapula spine
Major
- Origin: T2-T5 spinous processes
- Inserts on medial border down to inferior angle
Innervation
- Dorsal Scapular Nerve
- Pre-clavicular branch from C5 nerve root
- Most commonly a neuropraxia
- Entrapment under hypertrophic middle scalene muscle
Causes
Primary Neurologic
- Entrapment, stretch, sharp trauma as above
- Brachial Neuritis (Parsonage-Turner Syndrome)
- Guillain-Barré Syndrome
Facioscapulohumeral Dystrophy
- Autosomal Dominant
- Abnormal face
- Weak periscapular muscles
- Relatively normal cuff and deltoid
- Causes severe bilateral winging
- Treatment: Non-operative or scapulothoracic fusion
Secondary Causes
- GHJ, Cuff, Bursa impingement
- Osteochondroma – snapping scapula
- Scapulothoracic bursitis
- Due to periscapular muscle fatigue caused by abnormal compensatory scapula motion for other shoulder pathology
- Deranged muscle firing patterns
Diagnosis
History
- Pain, dysfunction, ache, recent virus, trauma, other problems
- Pain in back when sitting against chair
- Winging causes shoulder weakness and dysfunction
Examination
- Test muscles
- Serratus Anterior
- Press-ups against wall – can’t do or fatigues quickly
- Medial winging
- Trapezius
- Shrug shoulders
- Lateral Winging
- Rhomboids
- Hands on hips – squeeze elbows behind back
- Lateral winging - milder
- Look for secondary causes
- Rule out Facioscapulohumeral dystrophy
Investigation
- NCS & EMG if neurologic problem suspected
- Plain XR
- MRI
- Screening for other pathology
Management
Non-operative
- Primary usually resolves over 18 months
- Appropriate treatment for secondary causes
- Physio
- Periscapular muscle strengthening
Surgical
- If winging is symptomatic and interfering with ADLs or sport
- Serratus Anterior Palsy
- Pec Major Sternal Head Transfer
- Trapezius Palsy
- Eden-Lange Procedure
- Move Levator Scapulae & Rhomboids to where Trapezius inserts
- Rhomboid Palsy
- Winging mild & doesn’t usually need treatment
Scapulothoracic Fusion
- For failed surgical transfer
- Facioscapulohumeral Dystrophy
- Medial & Lateral Scapula Winging