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)
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