INFLAMMATORY ARTHRITIS (SHOULDER)
Systemic Disease | Central Erosion | Cuff Status Critical
NEER CLASSIFICATION
Critical Must-Knows
- Cuff Status is King: Intact cuff = Anatomic TSA; Torn/Dysfunctional cuff = Reverse TSA or Hemi
- Glenoid Bone Stock: Central erosion (acetabularization) is hallmark; differs from posterior wear in OA
- Medical Management First: DMARDs and Biologics have revolutionized care; surgery is for failed medical management
- Perioperative Risks: Infection risk increased (immunosuppression), skin fragility, osteopenia
- Cervical Spine: Always clear the C-spine (instability) before airway manipulation
Examiner's Pearls
- "Always check C-spine flexion/extension views before surgery (Atlanto-axial instability)
- "Hemiarthroplasty historically preferred to avoid glenoid loosening ('rocking horse'), but TKA now standard if bone stock allows
- "Reverse TSA is the workhorse for Rotator Cuff Deficient RA shoulders
- "Deltoid function is the last line of defense - protect it!
RA vs OA Differentiation
In Rheumatoid (RA)
Central Erosion: The humeral head migrates centrally into the glenoid ("acetabularization"). Bone is osteopenic. Osteophytes are rare. Rotator cuff often torn or thinned.
In Osteoarthritis (OA)
Posterior Erosion: The head migrates posteriorly (retroversion). Bone is sclerotic. Large osteophytes (Goat's beard). Rotator cuff usually intact.
Surgical Decision Matrix
| Scenario | Cuff Status | Glenoid Bone | Key Treatment |
|---|---|---|---|
| Early RA, synovitis | Intact | Preserved | Arthroscopic Synovectomy |
| End-stage RA | Intact | Adequate | Total Shoulder Arthroplasty (TSA) |
| End-stage RA | Torn/Thin | Adequate/Eroded | Reverse TSA |
| Severe bone loss | Any | Severe Erosion | Hemiarthroplasty or Augmented Glenoid |
EROSIONRA Shoulder Features
Memory Hook:EROSION reminds you of the destructive nature of RA on both bone and soft tissue.
DRUGSSurgical Risks in RA
Memory Hook:DRUGS reminds you of the perioperative medical optimization required.
WDRNeer Classification (RA)
Memory Hook:Wet (active), Dry (burned out), Resorptive (severe) - guides synovectomy vs arthroplasty.
Overview and Epidemiology
Inflammatory arthritis of the shoulder encompasses a group of systemic conditions (Rheumatoid Arthritis, Psoriatic Arthritis, Ankylosing Spondylitis) causing synovial inflammation, cartilage destruction, and periarticular bone erosions. The hallmark is concentric or central glenoid wear and concurrent soft tissue (rotator cuff) destruction.
Epidemiology:
- Prevalence: 90% of RA patients develop shoulder symptoms.
- Gender: Female > Male (3:1).
- Trend: Surgical incidence declining due to effective biologic therapies.
- Bilateral: Commonly bilateral involvement.
Pathophysiology:
- Synovitis: Hypertrophic inflamed synovium (pannus).
- Marginal Erosions: Occurs at "bare area" where cartilage doesn't protect bone.
- Cartilage Destruction: Proteolytic enzymes released by pannus.
- Cuff Attrition: Pannus invades rotator cuff tendons leading to thinning and rupture.
- Central Migration: Humeral head erodes centrally into glenoid vault.
Anatomy and Biomechanics
The Target Organ
In RA, the synovium is the primary site of pathology.
- Normal: Thin, few cell layers.
- RA: Massive hypertrophy, angiogenesis, pannus formation.
- Bare Area: The area of bone within the capsule but not covered by cartilage (e.g., surgical neck, glenoid neck) is the site of initial marginal erosions.
This contrasts with OA, where cartilage wear is the primary event.
Classification Systems
Classic description of RA stages:
| Stage | Name | Features | Treatment |
|---|---|---|---|
| I | Wet | Active synovitis, marginal erosions, osteopenia | Medical / Synovectomy |
| II | Dry | Sclerosis, cysts, loss of joint space (burned out) | Arthroplasty (TSA) |
| III | Resorptive | Severe bone loss, pencil-in-cup deformity | Augmentation / Reverse |
This guides the decision between soft tissue procedures (synovectomy) and reconstruction.
Clinical Assessment
History
- Morning Stiffness: Lasting over 1 hour typical.
- Systemic Symptoms: Fatigue, malaise, other joints (hands/feet).
- Pain: Nocturnal pain common.
- Function: Often poor due to stiffness + weakness (cuff).
Physical Exam
- Inspection: Muscle wasting (spinati), swelling (boggy anteriorly).
- Palpation: Warmth, effusion, tenderness.
- Cuff Strength: Often weak (pain or tear). Lag signs indicate massive tears.
Cervical Spine
Always examine the neck. 25-80% of RA patients have C-spine involvement. Subluxation can cause radiculopathy mimicking shoulder pain, or myelopathy.
Thorough neck exam is mandatory.
Investigations
Diagnostic Workup
ESR, CRP: Markers of active inflammation. RF, anti-CCP: specific for RA. CBC: Check for anemia of chronic disease or leukopenia (Felty's).
CT Scan: define glenoid version and bone stock. MRI: define cuff status.
C-Spine Flex/Ext X-rays: Rule out AAI. Cardiac: risk stratification. Meds: Review DMARDs schedule with Rheumatologist.
Synovial Fluid Analysis:
- If diagnosis unclear or infection suspected (septic arthritis).
- RA Fluid: WBC 2,000-50,000 (inflammatory), Cloudy, Low viscosity, Glucose low.
Management Algorithm
Medical Management
- Pharmacotherapy: NSAIDs, DMARDs (Methotrexate), Biologics (TNF-alpha inhibitors).
- Physical Therapy: Gentle ROM, avoid aggressive strengthening if cuff fragile.
- Injections: Corticosteroid (limited use - risk of infection/cuff atrophy).
Preop Meds
Methotrexate can typically be continued perioperatively. Biologics are usually held for 1 dosing cycle before surgery to reduce infection risk. Check local guidelines.
Regular monitoring required.
Surgical Technique (Key Points)
Anatomic TSA in RA
- Exposure: Deltopectoral approach. Handle soft tissues gently (fragile).
- Subscapularis: Often thin/friable. careful takedown and repair.
- Glenoid:
- Central wear: May need to ream eccentrically or use augmented component.
- Fixation: Pegged ingrowth components preferred over cemented (better bone preservation).
Careful soft tissue handling.
Complications
| Complication | Risk in RA | Reason | Management |
|---|---|---|---|
| Infection | High | Immunosuppression, skin fragility | Debridement, antibiotics, explant |
| Glenoid Loosening | Moderate | Osteopenia, eccentric reaming | Revision to Reverse / Bone graft |
| Periprosthetic # | High | Cortical thinning (disuse/steroids) | ORIF vs Stem revision |
| Cuff Failure | High | Progressive disease | Revision to Reverse |
The 'Rocking Horse' Glenoid
In anatomic TSA, if the rotator cuff is unbalanced or fails, the humeral head migrates superiorly and eccentrically loads the superior rim of the glenoid component. This cyclic "rocking" leads to early loosening.
Postoperative Care
Rehabilitation Protocol:
- Phase 1 (0-6 weeks): Sling. Passive ROM only (protect Subscap repair). Pendulums.
- Phase 2 (6-12 weeks): Active assistive ROM. AAROM pulleys.
- Phase 3 (3-6 months): Active ROM. Gentle strengthening.
- Phase 4 (6+ months): Full activity.
Specific Considerations in RA:
- Slower healing: Soft tissue repairs (subscap) take longer.
- Osteopenia: Avoid aggressive passive stretching (fracture risk).
- Skin: Care with dressings/tape (tears).
Outcomes and Prognosis
Pain Relief:
- Arthroplasty (TSA or Reverse) provides excellent pain relief (over 90%) in RA.
- Function is less predictable than in OA, due to muscles/cuff.
Implant Survival:
- Anatomic TSA: 90% at 10 years, but accelerated glenoid loosening (radiographic lucency common).
- Reverse TSA: 85-90% at 10 years. Complication rate slightly higher.
- Hemi: Lower satisfaction, ongoing glenoid pain.
Summary: Surgery significantly improves Quality of Life, but complication rates (infection, fracture) are higher than in OA.
Evidence Base
Outcomes of TSA in RA
- Long term follow up of TSA in RA
- 93% pain relief
- High rate of glenoid lucency (loosening) over time
- Cuff integrity was key predictor of survival
Reverse TSA for RA
- Study of Reverse TSA in RA patients
- Excellent functional outcomes regardless of cuff status
- Lower revision rate compared to Hemi in cuff-deficient shoulders
- Infection rate slightly higher than OA
Hemi vs TSA in RA
- Prospective comparison
- TSA had significantly better pain relief and ROM than Hemi
- Hemiarthroplasty led to progressive glenoid erosion
Central Migration Pattern
- Described 'acetabularization' of the glenoid
- Contrast with 'posterior wear' of OA
- Implications for reaming: Central reaming requires care not to breach medial wall
Biologics and Surgery
- Risk of infection with TNF inhibitors
- recommend stopping 1-2 dosing cycles pre-op
- Restart after wound healing (14 days)
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Early Disease
"A 45-year-old female with known RA presents with increasing shoulder pain. She is on Methotrexate. X-rays show symmetric joint space narrowing but spherical head. Cuff is 5/5 strength. Management?"
Scenario 2: Advanced Disease, Intact Cuff
"A 65-year-old RA patient has severe glenohumeral pain. X-rays show destruction of joint space and central erosion. MRI shows the Rotator Cuff is INTACT. Options?"
Scenario 3: Cuff Tear Arthropathy
"A 70-year-old with RA has a painful, pseudoparalyzed shoulder. Unable to lift arm over 45 degrees. X-rays show high riding humeral head and severe arthritis. Plan?"
MCQ Practice Points
Question 1
Q: What is the most common pattern of glenoid wear in Rheumatoid Arthritis? A. Posterior wear (Retroversion) B. Superior wear C. Central wear (Medialization) D. Anterior wear Answer: C. RA causes central erosion/acetabularization. OA causes posterior wear (B2 glenoid).
Question 2
Q: Which medication is typically held for 1-2 dosing cycles prior to arthroplasty? A. Methotrexate B. TNF-alpha inhibitors (e.g., Adalimumab) C. Prednisone D. Sulfasalazine Answer: B. Biologics are held to reduce infection risk. Methotrexate is typically continued.
Question 3
Q: In an RA patient with end-stage arthritis and a massive rotator cuff tear, the best surgical option is: A. Arthroscopic Debridement B. Hemiarthroplasty C. Anatomic TSA D. Reverse TSA Answer: D. Anatomic TSA will loosen (rocking horse). Hemi won't restore function. Reverse TSA addresses both arthritis and cuff deficiency.
Question 4
Q: Pre-operative evaluation of the RA patient for shoulder surgery MUST include: A. EMG B. Cervical Spine X-rays (Flexion/Extension) C. Bone Scan D. Angiogram Answer: B. Atlanto-axial instability is common and poses a lethal risk during intubation/positioning.
Question 5
Q: The presence of a 'High Riding' humeral head on X-ray indicates: A. Deltoid atrophy B. Rotator Cuff Incompetence C. Axillary nerve palsy D. Posterior dislocation Answer: B. Unopposed deltoid pull migrates the head superiorly when the supraspinatus is torn.
Question 6
Q: Which of the following is a contraindication to unconstrained (Anatomic) TSA? A. Advanced age B. Deficient Rotator Cuff C. Central glenoid wear D. Previous synovectomy Answer: B. Anatomic TSA requires an intact cuff to center the head. Without it, the "rocking horse" effect loosens the glenoid.
Australian Context
PBS and Biologics:
- Australia has strict criteria (PBS) for biologic DMARDs.
- Patients failing conventional DMARDs (Methotrexate) are eligible.
- This has significantly reduced the rate of synovectomies and early arthroplasties seen in Australian hospitals compared to historical data.
Joint Registry (AOANJRR):
- Shows Reverse TSA usage is increasing exponentially, including for inflammatory arthritis.
- Revision rates for TSA in RA are slightly higher than for OA, primarily due to infection and soft tissue failure.
Referral Pathways:
- Rheumatology and Orthopaedics often co-manage.
- "Combined Clinics" common in major public hospitals (e.g., Royal Adelaide, Alfred, Royal North Shore).
Inflammatory Arthritis
High-Yield Exam Summary
Key Concepts
- •Pathology is Synovitis leads to Pannus leads to Cartilage/Bone Destruction
- •Central Migration (Acetabularization) is hallmark
- •Rotator Cuff status determines implant choice (TSA vs Reverse)
- •Biologics have revolutionized care (fewer surgeries)
Clinical Pearls
- •Check the Neck! (C-spine instability)
- •Skin is fragile - handle with care
- •Infection risk is higher (immunosuppressed)
- •Bone is osteopenic - avoid aggressive reaming
Surgical Rules
- •Intact Cuff leads to Anatomic TSA
- •Torn Cuff leads to Reverse TSA
- •Active Synovitis (early) leads to Synovectomy
- •Hold Biologics perioperatively
Complications to Quote
- •Infection (higher than OA)
- •Glenoid Loosening (Rocking Horse)
- •Periprosthetic Fracture
- •Cuff Failure (if Anatomic done)