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Updated: Sep 29 2024

Total Shoulder Arthroplasty

Images
https://upload.orthobullets.com/topic/3075/images/total shoulder arthroplasty.jpg
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  • Introduction
    • Replacement of humeral head and glenoid resurfacing
      • cemented all-polyethylene glenoid resurfacing is standard of care
    • Total shoulder arthroplasty unique from THA and TKA in that
      • greater range of motion in the shoulder
      • success depends on proper functioning of the soft tissues
      • glenoid is less constrained
        • leads to greater shear stresses and is more susceptible to mechanical loosening
    • Factors required for success of TSA
      • rotator cuff intact and functional
        • if rotator cuff is deficient and proximal migration of humerus is seen on x-rays (rotator cuff arthropathy) then glenoid resurfacing is contraindicated
        • if there is an irreparable rotator cuff deficiency then proceed with hemiarthroplasty or a reverse ball prosthesis
        • an isolated supraspinatus tear without retraction can proceed with TSA
          • incidence of full thickness rotator cuff tears in patients getting a TSA is 5% to 10%
          • if positive impingement signs on exam, order a pre-operative MRI
      • glenoid bone stock and version
        • if glenoid is eroded down to coracoid process then glenoid resurfacing is contraindicated
        • see Walch classification below
    • Outcomes
      • pain relief most predictive benefit (more predictable than hemiarthroplasty)
      • reliable range of motion
      • good survival at 10 years (93%)
      • good longevity with cemented and press-fit humeral components
      • worse results for post-capsulorrhaphy arthropathy
  • Classification
      • Walch Classification of Glenoid Wear
      • Type A
      • Concentric wear, no subluxation of HH, well centered
      • A1: no or minor central erosion
      • A2: deeper central erosion, line connects anterior/posterior glenoid rims and transects humeral head (HH)
      • Type B
      • Biconcave glenoid, asymmetric glenoid wear and head subluxated posteriorly
      • B0: pre-osteoarthritic posterior subluxation of HH
      • B1: posterior joint narrowing (no posterior bone loss), osteophytes, subchondral sclerosis
      • B2: posterior rim erosion, retroverted glenoid
      • The highest degrees of glenoid erosion in B2 glenoids is typically seen between the 7- and 8-o'clock positions (posteroinferior)
      • B3: mono-concave, posterior wear, at least HH subluxation >70% OR retroversion >15%
      • Type C
      •  C1: Glenoid retroversion >25 degrees, regardless of erosion
      • C2: Biconcave, posterior bone loss, posterior translation of HH
      • Type D
      • Glenoid anteversion or anterior HH subluxation (HH subluxation <40%)
  • Indications
    • Indications
      • pain (anterior to posterior), especially at night, and inability to perform activities of daily living
      • glenoid chondral wear to bone
        • preferred over hemiarthroplasty for osteoarthritis and inflammatory arthritis
      • posterior humeral head subluxation
    • Contraindications
      • insufficient glenoid bone stock
      • rotator cuff arthropathy
      • deltoid dysfunction
      • irreparable rotator cuff (hemiarthroplasty or reverse total shoulder are preferable)
        • risk of loosening of the glenoid prosthesis is high ("rocking horse" phenomenon)
      • active infection
      • brachial plexus palsy
  • Preoperative Imaging
    • Radiographs
      • true AP
        • determine extent of arthritis and look for superior migration of humerus
      • axillary view
        • look for posterior wear of glenoid
    • CT scan
      • obtain CT scan to determine glenoid version and glenoid bone stock
    • MRI
      • evaluate rotator cuff condition
  • Approach
    • Deltopectoral
      • detach the subscapularis and capsule from anterior humerus
      • dislocate shoulder anteriorly
      • tight shoulders may require release of the upper half of the pectoralis tendon to increase exposure and dislocation
        • pectoralis major tendon passes on top of the biceps tendon to attach to the humerus
    • Complications
      • axillary nerve damage is the most common complication
        • axillary nerve and posterior humeral circumflex artery pass beneath the glenohumeral joint in the quadrilateral space
  • Technical considerations
    • Capsule
      • anterior capsule contracture (passive ER < 40°)
        • treatment
          • anterior release and Z-lengthening
      • posterior capsule stretching
        • treatment
          • volume-reducing procedure (plication of posterior capsule)
    • Subscapularis
      • no differences in outcomes between subscapularis peel, lesser tuberosity osteotomy, subscapularis tenotomy, partial tenotomy 
    • Glenoid deficiency and retroversion
      • glenoid deficiency
        • treatment
          • build up with iliac crest autograft or part of the resected humerus
          • do not use cement to build up the deficiency
      • retroverted glenoid
        • degree of retroversion determines treatment type
        • treatment
          • for retroversion > 15 degrees
            • build up posterior glenoid with allograft
          • for retroversion < 15 degrees
            • eccentrically ream anterior glenoid
    • Glenoid component
      • convex backside superior to flat
      • recreate neutral version
      • peg design is biomechanically superior to keel design
      • polyethylene-backed components superior to metal-backed components
        • glenoid not large enough to accommodate both metal and PE
      • cemented glenoid has a lower rate of loosening
      • conforming vs. nonconforming
        • both have advantages and neither is superior
        • conforming is more stable but leads to rim stress and radiolucencies
        • nonconforming leads to increased polyethylene wear
    • Humeral stem fixation
      • cemented stem or uncemented porous-coated implants
      • position of humeral stem should be 25-45° of retroversion
        • if position of glenoid retroversion is required, then the humeral stem should be less retroverted to avoid posterior dislocation
      • avoid valgus positioning of humeral stem
      • avoid overstuffing the humeral head
        • increases joint reaction forces and tension on the rotator cuff
        • the top of the humeral head should be 5 to 8 mm superior to the top of the greater tuberosity
      • intraoperative humerus fracture
        • greater tuberosity fracture
          • treatment
            • if minimally displaced, insert a standard humeral prosthesis with suture fixation and autogenous cancellous bone grafting of the greater tuberosity fracture
        • humeral shaft fracture
          • treatment
            • remove prosthesis and add longer stem with cement and reinforce with cerclage wiring
  • Rehabilitation
    • Passive or active-assisted motion only during early rehab
      • limiting factor in early postoperative rehabilitation is risk of injury to the subscapularis tendon repair
    • Progress to ER isometrics
    • Limit passive external rotation
      • risk of tear and pull-off of subscapularis tendon from anterior humerus
        • tear leads to anterior shoulder instability (most common form of instability after TSA)
        • treatment of subscapularis pull-off is early exploration and repair of tendon
        • test for pull-off of subscapularis
          • weak belly-press test
          • inability to put hand in back pants pockets or tuck shirt behind the back
        • avoid pushing out of chair during acute rehab
    • IR eccentric and isometric
    • Post-operative pain control
      • Preoperative narcotic associated with increased post-operative narcotic use
      • Increasing age associated with decreased post-operative narcotic use
  • Complications
    • Glenoid loosening
      • common cause of TSA failure and revision
        • historically, more common complication than rotator cuff failure
        • newer evidence suggests rotator cuff tear/failure may be more common than glenoid loosening
      • risk factors
        • insufficient glenoid bone stock (posterior glenoid wear associated with glenoid loosening)
        • rotator cuff deficiency
      • 2.9% reoperation rate for loosening (28% with revision)
      • radiographic lines
        • presence of radiographic lines does not correlate with symptoms
        • progression of a radiographic line does correlate with symptoms
          • progression present in 50% of patients as early as 3 to 4 years after TSA
        • radiolucency around the glenoid does not always correlate with clinical failure
          • at 3- and 7-year follow-up did not correlate with poor functional outcomes or pain
    • Vascular injury
      • Arcuate artery, branch off the anterior humeral circumflex artery, can be damaged during biceps tendon elevation
    • Humeral stem loosening
      • more common in RA and osteonecrosis
      • rule out infection
    • Malposition of components
    • Improper soft tissue balancing
      • failure due to undiagnosed presence of rotator cuff tears
    • Iatrogenic rotator cuff injury/attritional rotator cuff tear
      • common cause of TSA failure (more common than glenoid loosening in some studies)
      • can occur if humeral neck osteotomy is inferior to level of rotator cuff insertion
      • overstuffing glenohumeral joint leading to attritional supraspinatus and subscapularis tears
      • common reason for conversion to reverse total shoulder arthroplasty 
    • Stiffness
    • Infection 
      • may have normal aspiration results
      • culture
        • arthroscopic tissue culture more sensitive (100% sensitive and specific) than fluoroscopically guided aspiration (17% sensitivity, 100% specific)
      • Propionibacterium acnes (P. acnes), 
        • now referred to as Cutibacterium acnes (c. acnes)
        • most common cause of indolent infections and implant failures
          • infection rate 1-2% after primary TSA
        • characteristics
          • gram positive, facultative, aerotolerant, anaerobic rod that ferments lactose to propionic acid
          • has high bacterial burden around the shoulder
          • forms biofilm within 18-90h (found on implant surface and on synovial tissue) >> planktonic (explains why aspiration is only 17% sensitive)
          • P. acnes PJI more common in males
        • presentation
          • initial pain & stiffness
          • later swelling & redness
        • diagnosis
          • use anaerobic culture bottles, keep for 10-14days (mean time to detection 6 days)
          • 16s rRNA PCR
          • imaging (XR, CT, ultrasound) positive for subluxation/loosening in 24% of cases
          • if implant is removed, sonicate implant (to dislodge bacteria from surface) for sonication culture
        • treatment
          • early infection (<6 weeks) can be treated with open irrigation and debridement
          • late infection (>6 weeks) should be treated by explant and 2-stage reimplantation after IV antibiotic (penicillin G, ceftriaxone, clindamycin, vanco) x 6wk, followed by 2-6mths of PO antibiotic
    • Neurologic injury
      • axillary nerve is most commonly injured
        • inferior border of subscapularis tendon can be used as a landmark to identify axillary nerve as it courses from anterior to posterior
      • musculocutaneous nerve can be injured by retractor placement under conjoint tendon
    • Periprosthetic fracture
      • acceptable fragment alignment ≤ 20° flexion/extension, ≤ 30° varus/valgus, ≤ 20° rotation malalignment
      • see table below
      • Wright & Cofield Classification of Periprosthetic fracture
      • Type
      • Characteristics
      • Treatment of Intraoperative Fracture
      • Treatment of Postop Fracture
      • Type A
      • Centered near the tip of the stem and extends proximally
      • Span fracture with standard length prosthesis (2-3 cortical diameters) or long-stem prosthesis.  Transosseous sutures for tuberosity fractures
      • Usually min displaced/angulated (treat nonop).
      • If significant overlap between prox-distal fragments, treat as if stem loose and revise to long stem prosthesis.
      • Type B
      • Centered at the tip of the stem and extends distally.
      • Span fracture with standard length prosthesis (2-3 cortical diameters) or long-stem prosthesis.
      • Cement in distal canal to engage prosthesis (do NOT let cement escape from fracture site).
      • Cortical strut allograft + cerclage.
      • Revise to long-stem prosthesis.
      • Cement in distal canal to engage prosthesis
      • Type C
      • Located distal to the tip of the stem.
      • Long-stem prosthesis, or if close to olecranon fossa, plate+screws± cerclage wire, strut allograft
      • ORIF (plate overlap prosthesis by 2 cortical diameters to avoid stress riser)
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