Rotator Cuff Tears

Rotator Cuff Mechanics

Supraspinatus

• Lies in plane of scapula
• Initiator of abduction but also fires throughout abduction

Infraspinatus & Teres Minor

• External rotators
• Infra acts mainly when arm in neutral
• Teres when arm in ER and Abduction

Subscapularis

• 50% of cuffs total power
• Superior 60% tendinous, inferior 40% muscular
• Passive restraint in neutral but not when arm abducted

Deltoid

• Elevates shoulder in FF and Abd
• Anterior, middle and posterior parts separated by raphe

Force Couples

• SS & deltoid create a medial force vector to press head against glenoid
• IF/TM & SSc are 2nd force couple keeping head centred in AP plane
• Disruption of these couples results in altered cuff mechanics

Pathoanatomy

Cuff Ultrastructure

• 5 Layer structure
  • Layer 2 is the main cuff tendinous portion
  • Layer 4 is the rotator cable
    • Thick bands of collagen running perpendicular to the line of the cuff tendons
    • The cable distributes the forces the cuff tendons exert unifying them
    • This is why despite a tear the shoulder can still be functional
  • Layer 5 is the deepest layer analogous with the capsule

Collagen content

• Musculotendinous part - type 1 collagen
• At the footprint - type 2 collagen – fibrocartilaginous cuff
• When tears occur type 3 collagen increases (reparative type collagen)

Vascularity

• Cuff blood supply
  • Ascending branch anterior circumflex
  • Posterior circumflex humeral
  • Acromial branch of thoracohumeral
  • Suprascapular artery
• Critical zone of the SS is 8-10mm from the insertion
  • It is the area where most tears occur
  • Previously thought to be a hypovascular zone
  • Actually may be hypervascular (neo-vascularisation)

Cuff Tear Aetiology

Intrinsic

• Related to critical zone vascularity
• Age related degeneration:
  • Decreased proteoglycan & water content & altered collagen type

Extrinsic

• Mechanical problems contributing to cuff attrition:
  • Acromial Morphology (type 2/3 acromium – Bigliani)
  • Traction spurs in CAL/ACJ
  • Internal Impingement (PS cuff against PS glenoid)
  • Varus malunion – change in resting length of cuff
  • Trapezius Palsy – greater GH ROM required to compensate for scapula weakness

Epidemiology

• 50% 80 year olds have an asymptomatic cuff tear
• Partial tears 50% more common
• Cuff tears progress over time in 50%

Mechanism of Cuff Tear

• Traumatic if <40 years
• Likely atraumatic if >60 years
• Likely to be overlap – some trauma in a susceptible tendon

Clinical Features

• Night pain – loss of gravity allows cuff impingement
• Functional deficit – overhead activities – reaching

Examination

• Impingement
• Restricted ROM
• Pain
• Passive vs active ROM

Cuff Power

• Internal Rotation lag test
  • Maximally ER arm
  • If slowly moves back into IR passively indicates Infra weakness
• Hornblower’s sign
  • Maximally ER and Abduct to 90 deg
  • If unable to hold ER indicates mainly Teres minor weakness
• Belly press – tests lower fibres sub scap more
• Lift off or pull of shoulder test upper fibres more

Imaging

XR

• GHJ degeneration
• Superior migration (narrowed acromiohumeral disance – normal = >7mm)
• Cystic, sclerotic and flattening of GT footbrint area

Ultrasound

• Non-invasive
• Very accurate
• Allows dynamic screening of cuff
• Operator dependent

MRI – preferably with arthogram

• Identifies partial tears
• Bursal or Articular side
• Cuff retraction (past glenoid edge is bad sign)
• Fatty infiltration
• Muscle bulk – look at how much SS fills SS fossa (<50% bad sign)

Classification of Cuff Tears

Time

• Acute = < 3months old, Chronic = >3months old
• Acute on chronic = progression in size or symptoms of a previous tear

Mechanistic

• Traumatic or insidious

Size

• According to Neer <1cm = small tear, >5cm = massive tear
• Massive tears tend to include at least 3 of the tendons: usually SS, IS, TM

Partial or Full Thickness

• Location (for partial thickness)
• Articular or bursal (3:1)

Management

• Need to treat the patient not the tear
• Patient demands and current functional state

Non-operative

• PT for Anterior deltoid and periscapular strengthening

Corticosteroid Injection

• No proven long term benefit
• May reduce acute inflammation and allow restoration of ROM
• Risk is further tendon degeneration & infection

Operative

• Acute repair
  • Acute traumatic FT tear
  • Young active person with FT tear
  • Sudden weakness or loss of function with a cuff tear at any age
• Pre-requisites for cuff repair
  • Repairable tendon
  • Tear not too big
  • Tear mobile and not retracted
  • Biology amenable to healing – no fatty infiltration, non-smoker

Repair Techniques

• Open, mini open or arthroscopic
• Arthroscopic has faster recovery and less pain but more failures
  • Especially in larger tears. Equal in smaller tears.
  • Open allows repair of any tear size
• Gold standard results
  • Risk of deltoid pull off & more painful – longer rehab
• Mini-open
  • Allows most tears to be addressed
  • Deltoid split – best of both?

Partial Thickness Tears

• Guidelines are to repair tears >50% thickness
• Either trans tendinous repair in situ or
• Complete tear and repair as for FT tear
• Controvertial and no evidence either way
• Main thing to consider on PT tears is if the cuff is balanced & functional
• Clinical judgement allows one to decide if it can be treated non-operatively
• Surgical treatment may be advocated in order to pre-empt progression

Double Row Repairs

• Coming into vogue
• Mechanically stronger in the lab
• Dissipate tension of repair across wider area – create larger footprint
• May cause ischaemia to tendon

Management of Massive Irreparable Tears

Elderly Low Demand

• Tuberoplasty, cuff debridement and ASAD
• Inferior results but reasonable pain relief and patient satisfaction at 5 years

Elderly Active Patient

• Reverse Geometry replacement
• No real bail out option if complications

Young Active Patient

• Tendon Transfer
• Latissmus Dorsi for Posterior Superior tears (needs intact Subscap)
• Can also use Teres Major transfer instead
• Pec Major for Subscap tears that are irreparable or Anterior-inferior tear

Complications

• Infection
  • Rare
  • Typical bacteria is Propionibactrium acnes
• Recurrent tear or failure of repair to heal (ore often)
• Anchor pull out
• Stiffness
• Deltoid failure (open technique)