Shoulder Arthroplasty

Indications

  • Major indication is pain from incongruous GHJ which is unresponsive to non surgical treatment
  • Operation is less often performed for loss of motion as return of movement less predictable than pain relief with TSR
  • Neer et al 1982 – four considerations at time of unconstrained TSR to limit complications
    • 1. Osseous deficiency of glenoid or humeral head
    • 2. Defective rotator cuff
    • 3. Deficient deltoid muscle due to axillary n palsy
    • 4. Chronic instability
  • Indications for TSR
    • RA
    • Osteoarthritis
      • Primary Osteoarthritis
      • Post traumatic Osteoarthritis
    • Cuff arthropathy
    • AVN with secondary glenoid changes
  • Indications for Hemiarthroplasty
    • Fracture
      • Four-part NOH fracture
      • Head splitting fracture
      • Elderly patients with NOH non-union (esp. anatomical NOH fracture with AVN)
    • Dislocation
      • Locked dislocation
      • Recurrent dislocation with Hill-Sachs lesion > 50%
  • Contraindications
    • Acute or persistent infection
    • Flail joint
      • Deltoid or Rotator Cuff paralysis
    • Charcot joint
    • Severe loss of bone stock
    • Non compliant patient

Design

  • Unconstrained
    • Good / Excellent > 90%
    • ± Glenoid resurfacing
    • Rely on intact rotator cuff & deltoid
    • Humeral component designed to
      • Stable proximal humeral fixation
      • Preserve cuff attachment
    • Glenoid component designed to
      • Stable glenoid fixation
      • Preserve subchondral bone
    • Types
      • Neer prosthesis & Rockwood’s Global (De Puy) prosthesis
      • Bigliani-Flatow (Zimmer) & Randelli (Lima) are modern modular variants
  • Semiconstrained
    • Hooded glenoid component
  • Constrained
    • Ball in socket
    • High loosening & failure rates
    • Periarticular fracture
    • Loose glenoid
    • Salvage procedure only for
      • Tumours
      • Irreparable massive cuff tears
      • Flail shoulders
    • Arthrodesis probably better option

Fixation techniques

  • Cement
  • Cementless
    • HA coated
  • Most common is the cemented humeral & glenoid components

Humerus

  • Low rate of loosening (0.5-1%)
  • Cement should be “thumbed in” without need for cement plug
  • Pressurised cement ↑ risk of humeral fracture

Glenoid

  • 1/3-1/2 will see lucent lines around the glenoid component
  • But true clinical loosening only 2% (Cofield 1993)
  • Significance of lucent lines uncertain
  • Lucent lines are often present immediately post-op & can represent poor cementing technique
  • Lucent line > 2mm deemed significant
  • Lucency about keel more significant than around flanges
  • May be association with clinical glenoid loosening & instability or cuff tears
  • use of metal-backed HA coated glenoid seems to have reduced lucency but problems with
    • Poly may separate from backing
    • Asymmetric wear on posterior glenoid can lead to metallic debris
  • Tried to overcome problem of loosening by mismatch of glenoid & humeral head with head being smaller than glenoid
    • attempt to reduce rim contact during humeroglenoid translation
  • addition of modularity allows
    • Ease of revision
    • Tensioning of soft tissues – lateralise the stem & so improve fulcrum for cuff
    • Fracture treatment

Preoperative Assessment

  • Need to exclude
  • Cervical spine disease
  • ACJ disease
  • Neuromuscular causes

Require

  • Functioning/ Repairable Cuff
  • Maintain stability
  • Maintain centre of joint rotation
  • Intact Deltoid
  • No joint instability

Investigations

Xray

  • AP, Lateral & Axillary views
  • AP GHJ view with IR & ER
    • Assess humeral head & wear
    • Superior head migration
    • Osteophyte formation
    • ACJ
    • Thickness & diameter of humeral canal
    • Humeral shaft deformity
  • Axillary view
    • Assess amount & position of glenoid wear
    • Posterior bone deficient in Osteoarthritis
    • Medial bone deficient in RA
    • Extent of medial migration
    • Position of humeral head
  • Lateral view
    • Anterior or Posterior translation seen
    • Position of tuberosities

CT Scan

  • assess bone deficiency
  • help to plan bone graft requirements

Surgical Technique

Preop

  • Evaluation & planning as above
  • antibiotics

Positioning

  • Beach chair position
  • Mayfield head rest
  • Fasten head with tape to it
  • Close to edge of table to allow hyperextension of arm when humeral component inserted
  • Arm board to support it
  • Sand bag (500mL) under scapula
  • Arm draped free

Incision & Approach

  • Deltopectoral approach
  • From deltoid origin to insertion
    • Start
      • Deltoid origin clavicle above coracoid
    • Over
      • apex of axilla
    • To
      • Deltoid insertion
  • Deltopectoral groove opened with retraction of Cephalic Vein taken medially / laterally
  • Expose Clavipectoral fascia
  • Don’t detach Deltoid
  • Upper 50% of tendinous Pectoralis Major divided
  • Can palpate the Musculocutaneous nerve under conjoint tendon
    • Minimum 17mm below coracoid
    • Average 31mm
  • Divide along lateral border of conjoint tendon
  • Slip finger below the Subscapularis to palpate the Axillary nerve
  • Ligate the Anterior Circumflex Humeral vessels at inferior border of the Subscapularis
  • Subscapularishttp://www.youtube.com/embed/AM1LYQdbcb4?rel=0
    • osteotomy
    • released
      • Off the humerus with 2cm cuff
  • Capsule released off the humerus
  • Anteriorly 12 o’clock to 6 o’clock
  • Anteroinferior capsule excised
  • ER to deliver the humeral head

Osteotomy

  • Put in 35° of ER to obtain correct retroversion
  • Flex elbow
    • Use forearm as protractor
  • Less retroversion in
    • Recurrent posterior dislocation
    • Deficient posterior glenoid
  • Neck Cut
    • 135°
    • Above the tuberosities at articular margin of head

Stem & Head

  • Head size
    • 15mm deep head normally
    • 22mm deep head useful in cuff arthropathy
  • Correct height
    • Head must sit above greater tuberosity 3-5mm
  • Correct size
    • Articulated concentrically with glenoid & CA arch
    • Small enough to close subscapularis
  • Correct tension
    • Descent 1/2 head
    • AP displacement 1/4 head
  • Shaft-neck angle normally 135°
  • Cemented or Press fit

Glenoid

  • Prepare Glenoid if required
  • Humeral head retractor to displace proximal humerus posteriorly
  • Burr vertical slot in glenoid for keel of prosthesis
  • Flatten glenoid so that trial sits flat
  • If severe glenoid bone deficiency consider
    • Angled component
    • Bone graft
  • Cement glenoid in position
  • Insert stem

Closure

  • Reattach Subscapularis
  • Ensure there is 30-40° external rotation
  • Close wound with drain
  • Shoulder immobiliser in neutral

Postoperative

  • Passive flexion & external rotation
  • Pendulum exercises
  • Use arm for gentle ADLs
  • Sling for 1-2/52
  • Start active resisted exercises at 6/52

Results

  • Pain relief
    • good 90%
  • Range of motion
    • variable
    • Osteoarthritis with intact cuff – 120° elevation
    • Posterior fracture or huge cuff tear – 40° elevation
  • Survival
    • comparable to other joints
      • 90% survival (ie 10% revision) at 10 years for Osteoarthritis (Cofield)
        • Ie. good mid-term results
      • Results after trauma are inferior

Special Circumstances

  • Primary Osteoarthritis
    • Recognised on XR as large anteroinferior osteophyte
    • Axillary view reveals asymmetric wear with posterior glenoid deficiency
    • Loose bodies common & sought after at surgery
    • Remember glenoid deficiency may need to be addressed
  • Rheumatoid Arthritis
    • Severe bony & soft tissue destruction the rule
    • Severe superior & medial glenoid wear common
    • Cuff tears 30%
    • Osteoporosis
    • AC joint disease
    • Always cement the humeral component because of the osteoporosis
    • May need to use only large humeral component if glenoid bone stock insufficient
    • Post op rehabilitation altered due to other limb involvement
  • Cuff Tear Arthropathy
  • Arthritis of Recurrent Dislocations
    • Recognised by osteophyte formation on humeral head & Hill-Sach’s lesion on axillary view
    • May require Subscapularis lengthening to allow ER particularly if previous surgery for instability
  • Old Trauma
    • Malunion or nonunion of the tuberosities
    • Associated nerve injuries
    • Shortened subscapularis
    • Humeral head collapse & malalignment
    • Bone loss from neck of humerus

Complications

In order of frequency

  • Loosening of component ~ 5-40%
  • Glenohumeral instability ~ 5-10%
  • Rotator cuff tear ~ 5%
  • Periprosthetic fracture < 2%
  • Infection
  • Failure of implant (incl dissociation of modular prosthesis)
  • Weakness/ dysfunction of deltoid
  • Aseptic loosening
  • Symptomatic loosening responsible for 1/3 of complications
    • 1. Glenoid Component loosening
      • Radiolucent line seen in 30-50% postop of which more than 90% seen on initial postoperative radiographs (Neer 1982)
      • Others have reported high incidence of radiolucent lines (eg 84% at 12 years, Torchia & Cofield)
      • Incidence of clinical loosening (shift in component or radiolucent line >1.5-2mm) lower & varies from 2%-45%
      • New designs include press-fit uncemented implants, plasma-sprayed implants, & tissue-ingrowth implants
      • Current methods to enhance fixation & durability of the glenoid include
        • Preservation of the subchondral plate
        • Spherical reaming to optimise osseous support
        • New glenoid designs & biomaterials
          • Use glenoid component with larger radius of curvature than corresponding humeral head
    • 2. Humeral Component loosening
      • Subsidence & complete radiolucent lines not uncommon
      • Radiolucent lines more common in humeral components inserted without cement
      • Clinical findings associated with loosening rare