High Revision Rates | Glenoid Loosening | Instability Risk | Infection Management
- Glenoid loosening is the leading cause of failure in anatomic TSA (20-30% radiolucency at 10 years)
- Instability is the most common complication of RSA (5-10%), often requiring revision
- Axillary nerve at highest risk during deltopectoral approach - check function preop and postop
- Infection requires minimum 6 weeks IV antibiotics; single-stage revision controversial
- Subscapularis failure leads to anterior instability - repair integrity critical in anatomic TSA
- “Glenoid baseplate failure in RSA often related to poor bone stock or scapular notching
- “Periprosthetic fractures classified by Vancouver system (adapted for shoulder)
- “Staphylococcus epidermidis most common organism in shoulder PJI
- “Notching occurs in up to 70% of RSA but clinically significant in less than 10%
Leading cause of TSA failure. Radiolucent lines in Lazarus zones, eccentric glenoid wear, rocking horse phenomenon. Revision requires bone grafting in 30-50% of cases.
RSA: posterior (60%), anterior (30%). TSA: anterior from subscapularis failure. Risk factors: poor component positioning, tissue deficiency, trauma. May require constraint or revision.
2-6% incidence, higher in revision. Propionibacterium acnes (indolent), S. epidermidis (acute). Hold sonication cultures 14 days. Biofilm on components requires removal.
Axillary nerve most common (1-4%). Also musculocutaneous, suprascapular. Most are neurapraxias recovering in 3-6 months. EMG at 3-4 weeks if no recovery. Document preop function.
- Timing
- Less than 4 weeks postop
- Key Features
- Wound drainage, fever, elevated CRP
- Management
- Debridement, polyethylene exchange, long-term antibiotics
- Timing
- Early (less than 3 months)
- Key Features
- Posterior in 60%, traumatic or atraumatic
- Management
- Closed reduction, assess component position, revise if malpositioned
- Timing
- Late (over 5 years)
- Key Features
- Pain, crepitus, radiolucent lines
- Management
- Revision TSA or convert to RSA depending on rotator cuff
- Timing
- Immediate postop
- Key Features
- Deltoid weakness (axillary), sensory loss
- Management
- Observation for 3-6 months, EMG at 3-4 weeks, exploration if no recovery
Overview and Epidemiology
Shoulder arthroplasty has the highest revision rate of all joint replacements (approximately 10% at 10 years for TSA, 15% for RSA). Understanding complication patterns, recognition, and management is critical for exam success and patient care. Registry data shows complication rates increasing with time, making long-term surveillance essential.
- Early (less than 3 months): Infection, nerve injury, instability, fracture
- Intermediate (3 months - 2 years): Periprosthetic fracture, component loosening
- Late (over 2 years): Glenoid wear, osteolysis, subscapularis failure, cuff tear
- Any time: Instability can occur early or late
- Revision surgery: 2-3x higher complication rate than primary
- Functional loss: 20-30 point drop in outcome scores after complication
- Patient satisfaction: Drops from 90% to under 60% with major complication
- Healthcare costs: Revision procedures cost 2-3x primary arthroplasty
Pathophysiology of Complications
Shoulder arthroplasty complications arise from three main pathophysiologic mechanisms: biological (infection, bone resorption, soft tissue failure), mechanical (instability, component loosening, wear), and technical (malposition, sizing errors, nerve injury). Understanding these mechanisms guides both prevention and treatment strategies.
- Infection: Biofilm formation on implant surfaces (S. epidermidis, P. acnes)
- Osteolysis: Polyethylene wear debris triggers macrophage activation
- Bone resorption: Stress shielding from humeral stem, glenoid bone loss
- Soft tissue failure: Subscapularis repair failure, rotator cuff progression
- Instability: Insufficient soft tissue tension, component malposition
- Glenoid loosening: Eccentric loading (rocking horse), poor fixation
- Impingement: Scapular notching in RSA, subacromial in TSA
- Wear: Metal-on-polyethylene articulation over time
- Primary Mechanism
- Bacterial contamination and biofilm
- Contributing Factors
- S. aureus most common, surgical factors, patient comorbidities
- Time Course
- Less than 4 weeks postoperative
- Primary Mechanism
- Indolent bacterial colonization
- Contributing Factors
- P. acnes biofilm, male patients, low virulence organisms
- Time Course
- Over 3 months, often years
- Primary Mechanism
- Loss of soft tissue tension
- Contributing Factors
- Insufficient lateralization, component malposition, subscapularis deficiency
- Time Course
- Early (less than 3 months) or late (after trauma)
- Primary Mechanism
- Eccentric loading and micromotion
- Contributing Factors
- Rocking horse phenomenon, poor cement technique, young active patient
- Time Course
- Progressive over 5-10 years
- Primary Mechanism
- Traction or direct trauma
- Contributing Factors
- Retractor pressure, arm positioning, anatomic proximity
- Time Course
- Immediate intraoperative
Eccentric glenoid loading in anatomic TSA creates asymmetric forces on the glenoid component with arm elevation. Superior loading during elevation causes the humeral head to act as a fulcrum, rocking the glenoid component. This micromotion disrupts the cement-bone interface, leading to radiolucent lines and progressive loosening. Prevention requires optimal component positioning, cement pressurization, and patient selection.
Classification of Complications
Temporal Classification
- Complications
- Nerve injury, acute infection, dislocation
- Incidence
- 5-8% combined
- Key Management
- Early recognition, urgent intervention for infection
- Complications
- Instability, periprosthetic fracture, wound issues
- Incidence
- 3-5%
- Key Management
- Component assessment, revision if malpositioning
- Complications
- Aseptic loosening, late infection, subscapularis failure
- Incidence
- 5-10%
- Key Management
- Imaging surveillance, functional assessment
- Complications
- Component wear, osteolysis, cuff tears, scapular notching
- Incidence
- 15-20% by 10 years
- Key Management
- Monitor, revise when symptomatic or progressive
Acute pain and fever within first month = infection until proven otherwise. Sudden loss of function after minor trauma = consider instability or periprosthetic fracture. Progressive pain over months = consider component loosening. Timing is key to differential diagnosis.
Clinical Presentation
Clinical Features by Complication Type
- Pain Pattern
- Constant, severe, worse at night
- Functional Loss
- Significant loss of function, unwilling to move
- Physical Findings
- Fever, wound drainage, erythema, warmth, tenderness
- Pain Pattern
- Persistent ache, not severe
- Functional Loss
- Moderate limitation, gradual decline
- Physical Findings
- Minimal external signs, may have normal exam
- Pain Pattern
- Sudden onset after trauma or motion
- Functional Loss
- Complete loss of function, arm held protectively
- Physical Findings
- Visible deformity, positive apprehension, neurovascular deficit possible
- Pain Pattern
- Progressive pain with activity, clicking
- Functional Loss
- Gradual loss of ROM and strength
- Physical Findings
- Crepitus, reduced ROM, mechanical symptoms
- Pain Pattern
- Variable - may be painless
- Functional Loss
- Deltoid weakness, inability to abduct
- Physical Findings
- Loss of deltoid contraction, lateral shoulder numbness
- Pain Pattern
- Acute pain after fall or trauma
- Functional Loss
- Sudden functional loss, unable to lift arm
- Physical Findings
- Deformity, crepitus, ecchymosis, pain with movement
Immediate evaluation needed: (1) Fever with wound drainage within 4 weeks = acute infection, (2) Sudden loss of function after trauma = instability or fracture, (3) Complete deltoid paralysis postop = axillary nerve injury requiring EMG, (4) Persistent pain with elevated CRP over 10 mg/L beyond 3 months = chronic infection, (5) Progressive mechanical symptoms = component loosening requiring imaging.
Differential Diagnosis of the Painful Shoulder Arthroplasty
The painful or poorly functioning replaced shoulder is a common exam scenario. The key discriminator is to exclude infection first in every case, then separate mechanical, neurological and extrinsic causes using timing, examination and targeted imaging.
- Discriminating features
- Rest/night pain, indolent in males, stiffness; may have normal CRP
- First-line test
- ESR/CRP then image-guided aspiration with prolonged culture
- Confirms / excludes
- Synovial cell count, alpha-defensin, multiple deep cultures (14-day hold)
- Discriminating features
- Progressive activity-related pain, mechanical clicking
- First-line test
- Serial radiographs (lucent lines, migration); CT
- Confirms / excludes
- Progressive radiolucency / component shift on CT
- Discriminating features
- Sudden loss of function, apprehension, often post-trauma (RSA posterior)
- First-line test
- AP and axillary radiographs; CT for version
- Confirms / excludes
- Dislocation/subluxation; component malposition
- Discriminating features
- Loss of internal rotation, anterior instability, pseudoparalysis
- First-line test
- Ultrasound or MARS MRI
- Confirms / excludes
- Cuff/subscapularis tear; intact tendon excludes
- Discriminating features
- Acute pain and deformity after fall
- First-line test
- AP and lateral radiographs
- Confirms / excludes
- Fracture line; assess component stability
- Discriminating features
- Focal weakness/numbness, often painless
- First-line test
- Clinical exam then EMG/NCS at 3-4 weeks
- Confirms / excludes
- Denervation on EMG; normal study excludes
- Discriminating features
- Adduction pain, deltoid-region tenderness, loss of elevation
- First-line test
- Radiographs (notch grade); CT or bone scan for stress fracture
- Confirms / excludes
- Notch grade 3-4; occult fracture on CT/bone scan
- Discriminating features
- Pain out of proportion, dermatomal or diffuse, normal implant imaging
- First-line test
- Cervical spine assessment, examination for CRPS features
- Confirms / excludes
- Cervical pathology or CRPS; normal arthroplasty workup
Investigations
- Radiographs: AP, scapular Y, axillary lateral - assess component position, lucent lines, fracture
- Inflammatory markers: CRP, ESR - trending values more useful than absolute
- Complete blood count: WBC, differential - elevated in acute infection
- Comparison to previous: Serial radiographs essential for detecting progression
- CT scan: Component version, bone defects, fracture characterization
- MRI: Rotator cuff integrity, soft tissue assessment (artifact from metal)
- Ultrasound: Aspiration guidance, fluid collection, subscapularis integrity
- Nuclear medicine: Tc-99 bone scan or WBC scan if infection suspected
Investigation Protocols
- Essential Tests
- CRP, ESR, radiographs, joint aspiration
- Advanced Tests
- WBC scan, synovial markers (alpha-defensin), sonication
- Diagnostic Threshold
- Synovial WBC greater than 3000 or 2 positive cultures
- Essential Tests
- AP, scapular Y, axillary radiographs, neurovascular exam
- Advanced Tests
- CT scan for component version and position
- Diagnostic Threshold
- Dislocation on imaging, component malposition on CT
- Essential Tests
- Serial radiographs (Lazarus zones), CRP to rule out infection
- Advanced Tests
- CT for bone defects, MRI for rotator cuff
- Diagnostic Threshold
- Progressive radiolucent lines over 2mm, symptoms
- Essential Tests
- Clinical exam (deltoid, biceps strength), sensory testing
- Advanced Tests
- EMG/NCS at 3-4 weeks, follow-up at 3 months
- Diagnostic Threshold
- Absent motor units on EMG, denervation potentials
- Essential Tests
- AP and lateral radiographs, component stability assessment
- Advanced Tests
- CT scan for fracture classification and surgical planning
- Diagnostic Threshold
- Fracture visible on radiographs, classify by Vancouver
Prosthesis Imaging
Management
Management of shoulder arthroplasty complications follows key principles: (1) Exclude infection in any complication (aspiration if any doubt), (2) Assess component position with CT if instability or unexplained pain, (3) Document neurovascular status before and after any intervention, (4) Optimize patient factors (nutrition, diabetes control, smoking cessation), (5) Consider salvage options early (resection arthroplasty, fusion, amputation in severe cases).
Complication-Specific Management
- Conservative Options
- None - surgical urgency
- Surgical Management
- Debridement, polyethylene exchange, component retention if stable, 6+ weeks antibiotics
- Salvage Options
- Two-stage revision, resection arthroplasty if failed
- Conservative Options
- Suppressive antibiotics only if non-surgical candidate
- Surgical Management
- Two-stage revision (remove, spacer, 6-12 weeks antibiotics, reimplant)
- Salvage Options
- Permanent spacer, resection arthroplasty, fusion
- Conservative Options
- Closed reduction, immobilization 4-6 weeks, physical therapy
- Surgical Management
- Open reduction, soft tissue repair, constrained liner if needed
- Salvage Options
- Revision with position correction, larger glenosphere
- Conservative Options
- None effective
- Surgical Management
- Revision surgery: correct version/tilt, increase lateralization, constrained components
- Salvage Options
- Fusion if multiple failed revisions
- Conservative Options
- Observation, activity modification, serial radiographs
- Surgical Management
- None required
- Salvage Options
- N/A
- Conservative Options
- Activity modification, analgesics (temporary only)
- Surgical Management
- Revision TSA (if cuff intact) or conversion to RSA (if cuff deficient), bone grafting 30-50%
- Salvage Options
- Resection arthroplasty if poor bone stock
- Conservative Options
- Observation, physical therapy, brace for protection, reassurance (80-90% recover)
- Surgical Management
- Exploration if no recovery by 6 months, neurolysis or grafting
- Salvage Options
- Tendon transfers, functional bracing if permanent
- Conservative Options
- Conservative if non-displaced, or ORIF with plate/cables
- Surgical Management
- ORIF preserving components
- Salvage Options
- Revision if fixation fails
- Conservative Options
- None
- Surgical Management
- Revision to long-stem prosthesis, bypass fracture by 2 cortical diameters
- Salvage Options
- Structural allograft if severe bone loss (Type B3)
Major Complications: Recognition and Management
1. Instability
Instability occurs in 5-10% of RSA cases and 1-3% of anatomic TSA. In RSA, posterior instability accounts for 60% of cases and is often related to insufficient lateralization, excessive humeral retroversion, or subscapularis deficiency. Early recognition and assessment of component positioning is critical.
Instability Assessment and Management
Clinical: Sudden loss of function, pain, visible deformity, arm held in protective position.
Imaging: AP and axillary lateral radiographs confirm direction of dislocation.
Neurovascular: Document axillary nerve and radial pulse before and after reduction.
RSA posterior: Traction, adduction, gentle internal rotation.
TSA anterior: Traction, abduction, external rotation.
Post-reduction: Confirm concentricity on axillary view, assess stability arc of motion.
CT scan: Assess glenoid component version (target 10 degrees retroversion for RSA, 5 degrees for TSA).
Humeral version: Check humeral component retroversion (target 20-30 degrees).
Lateralization: Measure glenosphere offset in RSA (minimum 25mm from glenoid face).
First-time, well-positioned components: Trial of immobilization 4-6 weeks.
Recurrent or malpositioned: Revision surgery to correct component positioning.
Soft tissue deficiency: Consider constrained liner or augmented glenosphere.
- Mechanism
- Reduced deltoid tension, loss of stability arc
- Prevention Strategy
- Use lateralized glenosphere or BIO-RSA design
- Mechanism
- Posterior subluxation in neutral rotation
- Prevention Strategy
- Target 20-30 degrees retroversion, check with CT
- Mechanism
- Loss of anterior restraint, posterior instability
- Prevention Strategy
- Repair subscapularis if possible, consider anterior augment
- Mechanism
- Inferior subluxation or anterior instability
- Prevention Strategy
- Correct tilt with reaming or augmented baseplate
2. Infection (Periprosthetic Joint Infection)
- Propionibacterium acnes: 30-40% of cases, indolent, male patients
- Staphylococcus epidermidis: 25-30%, biofilm former
- S. aureus: 15-20%, more acute presentation
- Culture-negative: 10-15%, consider P. acnes with extended culture
- Major criteria: 2 positive cultures of same organism
- Minor criteria: Elevated ESR/CRP, positive histology, purulence
- Hold cultures: 14 days for P. acnes (slow growing)
- Sonication: Increases culture yield by 15-20%
Infection Management Algorithm
Acute (less than 4 weeks): Wound drainage, erythema, fever, elevated WBC.
Chronic (over 4 weeks): Persistent pain, elevated CRP (over 10 mg/L), mechanical symptoms.
Baseline labs: CBC, ESR, CRP before antibiotics if possible.
Aspiration: Under ultrasound or fluoroscopy, send for cell count, cultures, Gram stain.
Cell count: Greater than 3000 WBC with greater than 70% PMNs suggestive of infection.
Hold cultures: Request 14-day hold for P. acnes.
Debridement: Remove all infected tissue, obtain 5-6 tissue cultures.
Component retention: Only if acute (less than 4 weeks), stable components, known organism.
Polyethylene exchange: Remove and replace polyethylene liner if retaining components.
Sonication: Send removed components for sonication culture.
Initial empiric: Vancomycin plus ceftriaxone until cultures available.
P. acnes: Penicillin G 4 weeks IV, then amoxicillin 2-6 months oral.
S. aureus (MSSA): Cefazolin or nafcillin 6 weeks.
Biofilm coverage: Rifampin often added for Staph species.
Single-stage: Remove components, debride, reimplant same setting (controversial).
Two-stage: Remove components, antibiotic spacer, 6-12 weeks antibiotics, then reimplant.
Resection arthroplasty: If bone stock insufficient or patient not surgical candidate.
Propionibacterium acnes causes indolent infections that can be easily missed. Symptoms may be limited to pain alone without systemic signs. Always hold cultures for 14 days and consider P. acnes in any male patient with persistent pain after shoulder arthroplasty, even with normal inflammatory markers.
3. Glenoid Component Loosening
Glenoid component loosening accounts for 30-40% of all TSA revisions. Radiolucent lines develop in 20-30% of patients by 10 years, but only 5-10% become symptomatic and require revision. The rocking horse phenomenon (eccentric loading with arm elevation) drives progressive loosening.
- Location
- Superior quadrant of glenoid
- Significance
- High stress area, early indicator of loosening
- Action
- Monitor closely if greater than 1mm width
- Location
- Anterior half of glenoid
- Significance
- Common with anterior eccentric wear
- Action
- Consider revision if progressive and symptomatic
- Location
- Inferior quadrant
- Significance
- Associated with inferior tilt or subsidence
- Action
- High concern if complete lucency around pegs
- Location
- Posterior half of glenoid
- Significance
- May indicate posterior glenoid wear
- Action
- Assess glenoid version on CT
- Location
- Complete lucency around component
- Significance
- Gross loosening, likely symptomatic
- Action
- Revision surgery indicated
- Pain: Progressive, worse with activity and loading
- Mechanical symptoms: Clicking, clunking, catching sensation
- Reduced ROM: Especially forward elevation and rotation
- Weakness: Secondary to pain and mechanical block
- CT scan: Assess bone defects (cavitary vs segmental)
- Rotator cuff: Check integrity - if torn, consider RSA
- Bone graft: Required in 30-50% of revisions for defects
- Component choice: Revision TSA vs conversion to RSA
4. Nerve Injuries
- Incidence
- 1-4% (highest risk)
- Mechanism
- Traction during exposure, retractor pressure, direct injury
- Recovery
- 80-90% recover by 6 months
- Incidence
- 0.5-1%
- Mechanism
- Traction, especially with excessive arm abduction
- Recovery
- 85-95% recover by 6 months
- Incidence
- 0.5-2%
- Mechanism
- Stretch during glenoid exposure, baseplate screw penetration
- Recovery
- Variable - 60-80% recovery
- Incidence
- Less than 0.5%
- Mechanism
- Excessive arm extension or inferior retraction
- Recovery
- Good recovery in over 90%
- Incidence
- Less than 0.1%
- Mechanism
- Excessive traction, positioning injury, direct trauma
- Recovery
- Poor recovery - permanent deficit common
Nerve Injury Management Protocol
Document preop function: Essential for medicolegal protection and baseline.
Gentle retraction: Avoid excessive force on retractors near neurovascular structures.
Positioning: Avoid arm hyperextension or excessive abduction under anesthesia.
Axillary: Loss of deltoid contraction, numbness over lateral shoulder.
Musculocutaneous: Weak biceps, numbness lateral forearm.
Suprascapular: Weakness in external rotation (infraspinatus).
Observation: Most are neurapraxias recovering spontaneously.
Physical therapy: Maintain ROM, prevent contractures.
Patient education: Reassure about high recovery rate.
Baseline study: Establish severity and localization of injury.
Axonotmesis vs neurapraxia: Distinguish based on recruitment and amplitudes.
Follow-up EMG: At 3 months to assess for reinnervation.
Indications: Complete paralysis with no EMG recovery at 6 months.
Technique: Identify nerve, assess continuity, consider neurolysis or grafting.
Prognosis: Late exploration (over 6 months) has poor outcomes.
5. Periprosthetic Fractures
Type A: Apophysis (greater/lesser tuberosity) - usually managed conservatively unless displaced over 5mm. Type B: Around or just below stem - most common, requires assessment of component stability (B1 stable, B2 loose, B3 poor bone stock). Type C: Well below stem - treat as native fracture, ORIF if displaced.
- Patient: Osteoporosis, age over 70, rheumatoid arthritis
- Surgical: Excessive reaming, press-fit stems, cuff tear revision
- Component: Uncemented stems (3x risk vs cemented)
- Trauma: Falls, especially in RSA with altered biomechanics
- Type A: Sling immobilization unless over 5mm displacement
- Type B1: ORIF with cables/plates, preserve component
- Type B2: Revision to long-stem prosthesis
- Type B3: Structural allograft plus revision long-stem
- Type C: Standard fracture fixation techniques
6. Humeral Stress Shielding and Bone Resorption
The mnemonic and component tables note "stress shielding from the humeral stem" and humeral-side bone resorption without developing the concept.
- Mechanism: a stiff, well-fixed humeral stem carries load down the diaphysis and unloads the proximal humerus (Wolff's law), so the bypassed proximal bone resorbs - calcar/medial-metaphyseal resorption, greater-tuberosity osteopenia, and cortical thinning, often with distal cortical hypertrophy and condensation lines around the stem tip.
- Risk factors: longer, larger-diameter, well-fixed stems (especially cemented or extensively coated); it is less marked with short-stem and stemless humeral designs, which load the metaphysis more physiologically - a major driver of the trend toward shorter humeral fixation.
- Distinguish from loosening: stress shielding is adaptive remodelling (proximal resorption with the stem still well-fixed), whereas loosening shows a progressive, circumferential lucent line at the bone-implant interface with component migration or subsidence.
- Clinical relevance: usually asymptomatic, but it erodes the bone stock needed at any future revision and may predispose to periprosthetic fracture; it rarely itself mandates revision.
Humeral stress shielding is proximal bone resorption when a stiff, well-fixed stem unloads the metaphysis (Wolff's law) - calcar resorption, tuberosity osteopenia and cortical thinning, more with long/large cemented stems and reduced by short-stem/stemless designs. It is usually asymptomatic adaptive remodelling, NOT loosening (which shows a progressive interface lucency and component migration), but it depletes the bone stock needed for future revision.
Surgical Technique
Revision Surgical Techniques for Complications
General Principles of Revision Surgery
- Extended deltopectoral approach for adequate exposure
- Identify and protect neurovascular structures (axillary nerve often scarred)
- Careful subscapularis mobilization - may require extensive release
- Systematic component removal - humeral component first, then glenoid
Component Removal Techniques
- Technique
- Extended osteotomy or cement splitting osteotome
- Pitfalls to Avoid
- Spiral fracture, perforation, excessive bone loss
- Technique
- Metal cutting instruments, flexible osteotomes
- Pitfalls to Avoid
- Proximal bone destruction, shaft perforation
- Technique
- High-speed burr for cement, curettes for bone interface
- Pitfalls to Avoid
- Anterior perforation, excessive medial reaming
- Technique
- Remove screws first, peripheral release with osteotomes
- Pitfalls to Avoid
- Central screw damage to vault, fracture
Bone Defect Management
- Cavitary defects: Impaction bone grafting with cancellous allograft
- Contained segmental (less than 25%): Cement filling or augments
- Large segmental (greater than 25%): Structural allograft or custom implants
- Glenoid vault deficiency: Consider metal augmented baseplate
Complications Specific to Implant Type
Reverse Shoulder Arthroplasty-Specific Issues
- Incidence
- 5-10%
- Mechanism
- Insufficient lateralization, malpositioning, tissue deficiency
- Management
- Revision with corrected positioning or constrained liner
- Incidence
- 44-96% (radiographic)
- Mechanism
- Inferior glenosphere impingement on scapular neck
- Management
- Usually asymptomatic - monitor for baseplate loosening
- Incidence
- 2-4%
- Mechanism
- Poor bone stock, insufficient screws, notching
- Management
- Revision with bone graft and larger baseplate
- Incidence
- 1-4%
- Mechanism
- Deltoid overstretching, stress fracture from altered loading
- Management
- Usually conservative - rest and immobilization
- Incidence
- 3-5%
- Mechanism
- Increased dead space from lateralization
- Management
- Drain use controversial - evacuate if symptomatic
Scapular notching occurs when the inferior glenosphere impinges on the scapular neck during adduction. While common (up to 70% of cases), it is clinically significant in less than 10%. Worry when: notching progresses to Grade 3-4 (Nerot-Sirveaux), there is baseplate screw loosening, or patient develops pain and loss of adduction. Prevention: inferior glenosphere tilt, lateralization, or inferior eccentric glenosphere.
Acromial and Scapular-Spine Stress Fractures (Levy Classification)
The table lists acromial fracture as an RSA complication but does not develop it, despite its being a leading cause of unexplained pain and loss of elevation after a previously successful reverse arthroplasty.
- Mechanism: reverse arthroplasty lengthens and tensions the deltoid (by lowering and medialising the centre of rotation); the repetitive deltoid pull then fatigues the acromion or scapular spine, producing an insufficiency/stress fracture, most often in osteoporotic or rheumatoid bone.
- Presentation: new superior or posterior shoulder pain with loss of previously gained active elevation and focal tenderness over the acromion or scapular spine, typically weeks to months after a satisfactory result.
- Levy (Crosby) classification by location: Type I = anterior acromion (anterior to the acromioclavicular joint / anterior deltoid origin); Type II = mid-acromion, posterior to the acromioclavicular joint and over the glenoid (middle deltoid origin); Type III = scapular spine. Type II and especially Type III (scapular spine) cause the greatest functional loss.
- Diagnosis: frequently occult on plain radiographs - a high index of suspicion with CT or bone scan is often required.
- Management: predominantly non-operative (sling or brace, activity restriction); internal fixation of the thin osteoporotic acromion or spine is technically difficult and unreliable, and outcomes after these fractures are often disappointing even when they unite.
New pain with loss of active elevation after a previously successful reverse arthroplasty should raise an acromial or scapular-spine stress (insufficiency) fracture from deltoid over-tensioning. Classify by Levy/Crosby site (Type I anterior acromion, Type II mid-acromion over the glenoid, Type III scapular spine). It is often radiographically occult (obtain CT or bone scan), is usually managed non-operatively, and is a recognised cause of a poor RSA outcome.
Understanding RSA-specific complications is essential given the increasing utilization of this prosthesis.
Postoperative Care
Postoperative Care Following Complication Management
Immediate Postoperative Period (0-6 weeks)
- Immobilization in sling - extended to 6 weeks for revision (vs 2-4 weeks primary)
- DVT prophylaxis: Mechanical and chemical (aspirin or LMWH)
- Pain management: Multimodal - regional block, paracetamol, NSAIDs, opioids PRN
- Wound monitoring: Daily inspection for drainage, erythema, dehiscence
Rehabilitation Protocol After Revision
- Timeframe
- 0-6 weeks
- Goals
- Protect repair, control pain, prevent stiffness
- Precautions
- Sling at all times, no active motion
- Timeframe
- 6-12 weeks
- Goals
- Restore passive motion
- Precautions
- Therapist-assisted only, respect tissue healing
- Timeframe
- 12-16 weeks
- Goals
- Active motion, begin isometrics
- Precautions
- No resisted exercises
- Timeframe
- 16-24 weeks
- Goals
- Progressive resistance, functional activities
- Precautions
- Avoid heavy lifting greater than 5kg
Specific Considerations
- Post-instability revision: May need prolonged immobilization (8 weeks) in position of stability
- Post-infection revision: Continue IV antibiotics per infectious disease guidance (typically 6-12 weeks)
- Post-fracture revision: Restrict activity until radiographic union confirmed
Revision Surgery: Principles and Outcomes
Revision Planning and Execution
CT scan: Essential for bone stock assessment, component position, version.
Infection workup: ESR, CRP, aspiration if any concern for infection.
Rotator cuff: MRI to assess integrity - determines RSA vs TSA revision.
Implant identification: Know the existing implant for extraction planning.
Glenoid: Preferential removal of cement, preserve bone stock.
Humeral: Flexible osteotomes, avoid perforation or fracture.
Bone defects: Assess size and location - cavitary vs segmental.
Cavitary defects: Impaction bone grafting with cancellous allograft.
Segmental defects (less than 25% surface): Augments or eccentric reaming.
Large segmental (over 25%): Structural allograft or custom components.
Glenoid: May use RSA baseplate for better fixation vs TSA re-glenoid.
Humeral: Long-stem component if bone loss or fracture risk.
Fixation: Cemented preferred in revision setting for immediate stability.
Slower protocol: 6 weeks immobilization common vs 2-4 weeks for primary.
ROM first: Passive ROM weeks 6-12, active ROM weeks 12-16.
Strengthening: Delayed until 4-6 months to allow bone/soft tissue healing.
Converting failed anatomic TSA to RSA is now the most common revision scenario. Indications: glenoid loosening with rotator cuff deficiency, subscapularis failure, or irreparable cuff tear. Challenges include glenoid bone loss (30-50% need grafting), humeral version mismatch (may need osteotomy), and deltoid scarring. Outcomes are 70-80% satisfactory vs 85-90% for primary RSA.
Outcomes
Outcomes After Complication Management
Revision Surgery Outcomes by Indication
- Satisfactory Rate
- 70-80%
- Re-revision Rate
- 10-15% at 5 years
- Key Prognostic Factors
- Correct positioning, adequate soft tissue
- Satisfactory Rate
- 75-85%
- Re-revision Rate
- 8-12% at 5 years
- Key Prognostic Factors
- Bone stock, cemented fixation
- Satisfactory Rate
- 80-85%
- Re-revision Rate
- 5-10% at 5 years
- Key Prognostic Factors
- Organism virulence, host factors
- Satisfactory Rate
- 70-75%
- Re-revision Rate
- 12-18% at 5 years
- Key Prognostic Factors
- Bone quality, fracture pattern
- Satisfactory Rate
- 80-85%
- Re-revision Rate
- 8-12% at 5 years
- Key Prognostic Factors
- Deltoid function, glenoid bone stock
Functional Outcomes
- Active forward flexion: Average 100-120 degrees (vs 140-150 primary RSA)
- External rotation: Average 20-30 degrees
- Patient satisfaction: 70-80% (vs 85-90% primary)
- ASES score improvement: Average 30-40 points (less than primary)
Prevention Strategies
- Preoperative: Optimize nutrition, control diabetes (HbA1c less than 7%), treat remote infections
- Antibiotic prophylaxis: Cefazolin 2g (3g if over 120kg) within 60 min of incision
- Skin preparation: Chlorhexidine alcohol superior to povidone-iodine
- P. acnes: Consider benzoyl peroxide wash protocol for male patients
- Drapes: Iodine-impregnated drapes may reduce infection
- Component positioning: Verify version and tilt intraoperatively with fluoroscopy
- Lateralization: Ensure minimum 25mm offset in RSA
- Soft tissue: Repair subscapularis anatomically in TSA
- Trial reduction: Test stability through arc before final components
- Avoid oversizing: Humeral component should not overstuff joint
- Bone preparation: Ream to cancellous bone, avoid anterior perforation
- Version correction: Correct excessive retroversion (target 5-10 degrees)
- Cement technique: Pressurize cement with finger or syringe
- Component choice: All-poly cemented pegged glenoid standard
- Patient selection: Consider RSA for young, high-demand patients
- Positioning: Avoid hyperextension, excessive abduction under anesthesia
- Retraction: Gentle retractor placement, avoid pressure on neurovascular structures
- Axillary nerve: Inferior capsular release under direct vision
- Suprascapular: Avoid superior baseplate screws over 30mm length
- Documentation: Record preoperative nerve function for baseline
Templating and preoperative planning reduce complications by 30-40%. Use CT-based 3D planning to: assess glenoid bone stock and version, plan correction strategy, determine implant size, and identify anatomic variants. In complex cases (revision, massive bone loss, dysplasia), patient-specific instrumentation or guides may be beneficial.
Guidelines, Registries & Global Practice
Global epidemiology
Shoulder arthroplasty is one of the fastest-growing arthroplasty procedures worldwide, driven overwhelmingly by the expansion of reverse total shoulder arthroplasty (RSA) beyond cuff-tear arthropathy into osteoarthritis with cuff insufficiency, proximal humeral fracture, and revision of failed primaries. Population-based and registry analyses from North America, Europe and Australasia consistently show year-on-year increases in volume and a shift in case-mix toward RSA in older patients. Because indications and implant mix differ between regions, reported complication and revision rates must always be interpreted against the underlying population and implant design.
Major guidelines side by side
- Position relevant to complications
- Appropriate-use criteria and clinical practice guidance for glenohumeral OA and cuff arthropathy; emphasises shared decision-making and VTE prophylaxis; perioperative infection prevention per MSIS/ICM consensus
- Typical evidence level
- Mostly moderate/limited evidence; many consensus recommendations
- Position relevant to complications
- Generic surgical-site infection and prosthetic joint infection principles apply; BOAST standards stress prompt recognition and MDT management of infection and periprosthetic fracture; referral of suspected deep infection to a specialist unit
- Typical evidence level
- Consensus standards built on systematic review
- Position relevant to complications
- Periprosthetic and stem-related fracture classification and fixation principles (bridge the stem by adequate cortical diameters; revise loose stems); construct selection driven by component stability
- Typical evidence level
- Expert consensus and technique evidence
- Position relevant to complications
- Aligns with international PJI consensus (ICM) on diagnosis thresholds, prolonged culture for Cutibacterium, and staged versus single-stage revision; supports tailored, organism-led treatment
- Typical evidence level
- Consensus, level varies by question
The biggest international difference is in periprosthetic joint infection management for low-virulence Cutibacterium acnes: several European and shoulder-specialist groups now favour single-stage revision with prolonged targeted antibiotics for suitable cases, whereas much North American practice and classic teaching still defaults to two-stage revision. All major bodies agree on prolonged (14-day) culture incubation and a structured multi-criteria PJI diagnosis (synovial fluid analysis, multiple deep cultures, histology). Antibiotic prophylaxis is near-universal: a first-generation cephalosporin within 60 minutes of incision, with a glycopeptide for proven beta-lactam allergy or known MRSA colonisation.
Registry evidence (global)
- Contribution to complication knowledge
- Large, near-complete capture; reverse arthroplasty revised more than anatomic TSA; instability, infection and loosening lead revision causes; glenoid fixation type affects revision risk
- Contribution to complication knowledge
- Tracks implant-specific survivorship and revision indications for shoulder replacement, supporting outlier detection and implant benchmarking
- Contribution to complication knowledge
- Growing shoulder dataset; documents the dominance of RSA in contemporary US practice and associated revision patterns
- Contribution to complication knowledge
- Long follow-up; early registries highlighted high revision after hemiarthroplasty for OA and the influence of indication on outcome
Global practice variation
- Implant choice: RSA now predominates for cuff-deficient and fracture indications in high-resource settings; anatomic TSA is preferred for OA with an intact cuff and good glenoid bone stock. In limited-resource settings, hemiarthroplasty retains a larger role due to cost and implant availability, accepting a higher rate of glenoid erosion.
- Cutibacterium strategy: Routine prolonged culture and benzoyl-peroxide skin preparation are widely adopted in shoulder-specialist centres but inconsistently applied elsewhere.
- Revision pathway: Single-stage versus two-stage revision for low-virulence PJI varies by region and surgeon, reflecting genuine equipoise rather than a settled standard.
- Surveillance: Countries with mandatory or near-complete registries (Australia, Nordic countries, UK) provide the most reliable revision data; elsewhere, complication estimates rely on single-centre series and are more prone to under-reporting.
Key documentation requirements to reduce litigation risk:
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Preoperative consent: Discuss specific complications (infection 2-6%, instability 1-10% depending on implant, nerve injury 1-4%, loosening requiring revision 10-15% by 10 years, need for future revision surgery). Document alternatives discussed (conservative management, arthroscopy, alternate implants).
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Surgical site marking: Mark correct side with patient awake, verify with timeout before incision.
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Implant tracking: Record implant type, size, lot numbers in medical record and registry. Keep implant stickers in patient chart.
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Nerve function: Document preoperative axillary, musculocutaneous, radial nerve function. Reassess immediately postop and at all follow-ups. If deficit develops, obtain EMG at 3-4 weeks and document management plan.
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Component positioning: Intraoperative fluoroscopy images showing component position. Consider postoperative CT for complex cases or instability.
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Infection prevention: Document prophylactic antibiotic timing, dose, and agent. Note skin preparation technique. Record implant handling protocols.
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Informed consent for revision: Higher complication rates (2-3x primary), lower functional outcomes (10-20 points on outcome scores), possibility of further revision surgery.
Common litigation issues: Nerve injury not documented preoperatively (difficult to prove timing), infection attributed to inadequate prophylaxis or poor technique, component malposition causing instability or loosening, failure to recognize and treat complications promptly, inadequate consent discussion of revision risk.
- Prophylaxis: First-generation cephalosporin (e.g. cefazolin) within 60 minutes of incision; weight-adjusted dosing
- Beta-lactam allergy / MRSA risk: Glycopeptide (vancomycin or teicoplanin), started early enough for adequate tissue levels
- Cutibacterium acnes PJI: Penicillin or amoxicillin-based regimens (high in-vitro susceptibility), prolonged duration for biofilm
- Staphylococcal PJI with retained implant: Add rifampicin-based combination per infection-specialist guidance
- Always confirm agent, dose and duration with local infection guidelines and antimicrobial stewardship
Mnemonic Aids
At a Glance
Shoulder arthroplasty complications have an overall rate of 10-15%. Glenoid loosening is the leading cause of anatomic TSA failure, with radiolucent lines (Lazarus zones) developing in 20-30% at 10 years. Instability is the most common complication of reverse shoulder arthroplasty (RSA) at 5-10%, typically posterior (60%) and often requiring revision. The axillary nerve is the nerve most at risk (1-4% injury rate), with most injuries being neurapraxias that recover in 3-6 months. Infection rates are 2-6%; Propionibacterium acnes (indolent) and Staphylococcus epidermidis (acute) are the most common organisms—hold cultures for 14 days and remove components for biofilm eradication. Scapular notching occurs in up to 70% of RSA but is clinically significant in under 10%.
INGLEMajor Shoulder Arthroplasty Complications
Hook:INGLE = IN GLE-noid we trust, but complications happen: Instability, Nerve, Glenoid, Loosening, infEction!
STORMRisk Factors for Instability After RSA
Hook:STORM = after RSA, these factors create a STORM of instability risk!
LAZARUSGlenoid Radiolucent Line Zones (Lazarus Classification)
Hook:LAZARUS = like Lazarus rising from the dead, glenoid lucent lines signal implant death approaching!
MCQ Practice Points
Q: Which nerve is at highest risk during deltopectoral approach for shoulder arthroplasty?
A: Axillary nerve (1-4% injury rate). The axillary nerve exits the quadrilateral space and travels along the inferior capsule and undersurface of the deltoid. It is at risk during inferior capsular release, deltoid retraction, and placement of inferior retractors. Always document preoperative deltoid function and sensory examination over lateral shoulder for medicolegal protection. Most injuries are neurapraxias recovering within 3-6 months.
Q: What is the Lazarus classification system and why is it important?
A: The Lazarus classification describes radiolucent lines around glenoid components in five zones: superior (Zone 1), anterior (Zones 2-3), inferior (Zone 4), and posterior (Zone 5). Lines less than 1mm are often benign and stable; lines greater than 2mm or progressive lines indicate loosening. Complete lucency in all zones suggests gross loosening requiring revision. This system helps standardize radiographic assessment and predict need for revision surgery.
Q: What is the optimal antibiotic regimen for Propionibacterium acnes shoulder PJI?
A: For P. acnes infection, the recommended regimen is penicillin G 18-24 million units/day IV for 4 weeks, followed by oral amoxicillin 2-6 months (total 6-12 weeks therapy). P. acnes is sensitive to penicillin in over 95% of cases. This indolent organism requires prolonged therapy due to biofilm formation. Cultures must be held 14 days as P. acnes is slow-growing and often missed with standard 5-day protocols.
Q: What is scapular notching in RSA and when is it clinically significant?
A: Scapular notching occurs when the inferior glenosphere impinges on the lateral scapular neck during adduction, causing bone erosion. It is very common (44-96% radiographically) but clinically significant in less than 10%. The Nerot-Sirveaux classification grades notching from Grade 1 (limited to pillar) to Grade 4 (extending to baseplate). Clinical significance occurs with Grade 3-4 notching causing pain, baseplate screw loosening, or loss of adduction. Prevention strategies include inferior glenosphere tilt, lateralization, and inferior eccentric glenosphere positioning.
Q: What do the major joint registries show about shoulder arthroplasty revision rates?
A: Across the large national registries (AOANJRR in Australia, NJR in England and Wales, AJRR in the USA, and the Nordic/Swedish registries), shoulder arthroplasty has among the higher revision burdens of the major joints, and reverse arthroplasty carries a higher cumulative revision rate than anatomic TSA at comparable follow-up. The leading recorded reasons for revision are consistently instability/dislocation, infection, and loosening/lysis. Glenoid fixation matters: registries have linked certain uncemented and metal-backed glenoid constructs to higher revision than cemented all-polyethylene designs. Quote exact percentages from the current annual report, as figures shift between reports.
Q: How do you manage a periprosthetic humeral shaft fracture (Vancouver Type B2) after shoulder arthroplasty?
A: Vancouver Type B2 indicates a fracture around or just below the stem with loose component. Management requires revision to a long-stem prosthesis (bypassing fracture by minimum 2 cortical diameters) with or without supplemental fixation (cables, cerclage wires, or plate). The fracture is typically addressed with cerclage cables proximally and a long-stem (150-200mm) cemented component for immediate stability. If bone quality is very poor (Type B3), structural allograft may be needed. Component retention (Type B1, stable component) can be managed with ORIF alone using cables and plate while preserving the stable prosthesis.
Exam Viva Scenarios
Practise clinical reasoning and management decisions out loud
“A 72-year-old woman presents 6 weeks after reverse shoulder arthroplasty for rotator cuff arthropathy. She fell onto her operated shoulder yesterday and now has pain and inability to use her arm. X-rays show posterior dislocation of the RSA. How do you assess and manage this patient?”
“A 58-year-old man presents with persistent shoulder pain 9 months after anatomic total shoulder arthroplasty for primary osteoarthritis. He describes constant aching pain that is worse at night and limits his function. He denies fever or wound issues. Inflammatory markers show CRP 18 mg/L (normal less than 5) and ESR 32 mm/hr (normal less than 20). Walk me through your diagnostic workup and management.”
“A 52-year-old active manual laborer presents 7 years after anatomic TSA for post-traumatic arthritis. He has progressive pain over 18 months, mechanical clicking, and reduced ROM. Radiographs show complete radiolucent lines around the glenoid component in all five Lazarus zones, with 5mm of superior tilt. CT shows cavitary bone loss posteriorly. How do you manage this case?”
Major Complications by Frequency
- Instability: 5-10% RSA (posterior 60%), 1-3% TSA (anterior from subscap failure)
- Glenoid loosening: 20-30% radiolucent lines by 10 years, 5-10% symptomatic revision
- Infection: 2-6% overall, P. acnes 30-40% (males, indolent), S. epi 25-30%
- Nerve injury: Axillary 1-4% (most common), musculocutaneous 0.5-1%, 80-90% recover
Classification and Timing
- Early (less than 3mo): Infection, nerve injury, instability, fracture
- Intermediate (3mo-2yr): Periprosthetic fracture, component loosening
- Late (over 2yr): Glenoid wear, osteolysis, subscapularis failure, cuff tear
- Lazarus zones: Superior (1), anterior (2-3), inferior (4), posterior (5) - assess width and progression
Management Algorithms
- Instability: CT to assess components, closed reduction if well-positioned, revise if malpositioned (insufficient lateralization less than 25mm, excessive retroversion over 30 degrees, superior tilt over 10 degrees)
- Infection: Aspiration with 14-day culture for P. acnes, debridement if acute less than 4wks, two-stage revision if chronic or biofilm
- Glenoid loosening: MRI for cuff integrity, revision TSA if cuff intact, convert to RSA if cuff deficient, bone graft in 30-50%
- Nerve injury: Document preop, EMG at 3-4wks if no recovery, explore if no recovery by 6mo
Surgical Pearls
- RSA instability prevention: Lateralization minimum 25mm, humeral retroversion 20-30 degrees, correct glenoid tilt (less than 10 degrees superior)
- Infection prevention: Cefazolin 2g (3g if over 120kg) within 60min, chlorhexidine alcohol prep, benzoyl peroxide for males (P. acnes)
- Glenoid loosening prevention: Cemented all-poly pegged glenoid, pressurize cement, correct version to 5-10 degrees retroversion
- Nerve protection: Gentle retraction, avoid hyperextension positioning, inferior capsule release under vision
Key Evidence and Registry Data
- Walch 2012 (PMID 22258001): 32% radiographic glenoid loosening in 518 keeled all-poly TSA at over 5 years (superior tilt, subsidence, posterior tilt)
- Zumstein 2011 (PMID 21134666): RSA complication rate ~44%, scapular notching most frequent finding
- Sirveaux 2004 (PMID 15125127): origin of the four-grade scapular notching classification; Constant 22.6 to 65.6
- Registries (AOANJRR/NJR/AJRR/Nordic): RSA revised more than anatomic TSA; instability, infection and loosening lead causes
- Revision outcomes generally inferior to primary with higher complication rates
Global Practice and Governance
- Near-complete registries (Australia, Nordic, UK) give the most reliable revision data; elsewhere rates rely on single-centre series
- Cutibacterium PJI: prolonged 14-day culture universal; single-stage vs two-stage revision varies by region (genuine equipoise)
- Prophylaxis: first-generation cephalosporin within 60 min; glycopeptide for proven allergy or MRSA
- Medicolegal: document preop nerve function, consent for revision risk, and implant tracking
Evidence Base and Key Trials
Complications of Shoulder Arthroplasty
- Comprehensive review updating the classic 2006 complication analysis, framing complications by component and implant type
- Glenoid component loosening remains the most frequently reported complication of anatomic total shoulder arthroplasty
- Instability, glenoid/baseplate problems, infection and neural injury are emphasised as the dominant reverse arthroplasty complications
- Highlights the rising share of reverse arthroplasty and its distinct complication profile compared with anatomic TSA
Problems, complications, reoperations, and revisions in reverse total shoulder arthroplasty: a systematic review
- Systematic review of 782 reverse arthroplasties pooled to define a complication taxonomy (problem, complication, reoperation, revision)
- Overall complication rate approximately 44%, with scapular notching the single most frequent finding
- Instability and infection were among the leading reasons for reoperation and revision
- Established the standard framework now used to report reverse arthroplasty adverse events
Complications in reverse total shoulder arthroplasty
- Narrative review of the complications unique to reverse arthroplasty as indications expanded beyond cuff arthropathy
- Lists the most common complications as neurologic injury, periprosthetic fracture, haematoma, infection, scapular notching, dislocation, baseplate failure and acromial fracture
- Notes the limited published evidence guiding best management of each complication
- Reinforces dislocation/instability as a leading early mode of failure