Shoulder Arthritis

Glenohumeral Osteoarthritis

Aetiology

• Primary or secondary to:
  • Trauma
  • Instability
  • Infection
  • AVN
  • Previous surgery – chondral damage, bioabsorbable anchors, LA pumps

Pathoanatomy

Bone

• Typical pattern is posterior glenoid erosion
  • Results in retroverted glenoid
  • 3 Types of glenoid:
    1. Concentric erosion of glenoid & no subluxation
    2. Posterior glenoid erosion, retroversion & subluxation
    3. Primarily Retroverted glenoid – posterior subluxations
• Humeral head flattening
• Humeral head posterior subluxation

Soft tissues

• Contracted anterior structures:
  • Anterior capsule
  • Subscapularis
• Lax posterior capsule from posterior subluxation
• Rotator cuff deficiency is rare in OA (5%)

Rheumatoid Arthritis

Aetiology

• Erosive Pannus & inflammatory cytokines cause bone & soft tissue disease
• 90% patients with RA have shoulder symptoms

Pathoanatomy

Bone

• Erosion is medial and concentric
• Humeral head retains its shape until very late stages
• Concentric joint space reduction
• Osteopenia, marginal erosions, and subchondral cysts

Soft Tissues

• Rotator cuff tears are more common:
  • 75% will develop cuff pathology at some stage
  • 25% full thickness tears at time of surgery
• Synovitis involving capsule, LHB

Classification

Neer – based on XR features

1. Dry - Osteopenia, cyst formation, joint space narrowing
2. Wet - Pointed appearance of humeral head, marginal erosions
3. Resorptive - Severe medial erosion to level of coracoid

Avascular Necrosis

Aetiology

• Humeral head second most commonly affected after femoral head
• Primary: Idiopathic – unknown cause
• Secondary:
  • Trauma
  • Steroids
  • Alcohol
  • Sickle cell
  • Gaucher’s, Caissons, SLE

Pathoanatomy

• AVN of humeral head affects superior middle region first

Blood Supply

• Primarily the Arcuate Artery as it enters bone
  • Branch of Ascending branch of Anterior Circumflex Humeral
  • Lies in lateral aspect LHB groove
• Secondarily from the Posterior Humeral Circumflex
  • Runs over posteromedial aspect of humeral head
• Decreased blood flow causes ischemia > bone resorption > microfracture > subchondral collapse > secondary OA
• AVN may or may not have concurrent cuff pathology

Classification

Creuss

1. No XR features
2. Head Sclerosis
3. Subchondral collapse (crescent sign)
4. Humeral head collapse but no glenoid changes
5. Humeral head & Glenoid OA changes

Crystal Arthropathy

• Gout:
  • Deposition of Sodium Urate crystals
  • Negative birefringence
• Pseudogout:
  • Calcium Pyrophosphate crystals
  • Positive birefringence
• Milwaukee shoulder:
  • Calcium Hydroxyapatite crystal deposition
  • Aspiration is blood-stained with debris
  • Inflammatory cells and monocytes
  • Positive staining with Alizarin red

Clinical Assessment of Shoulder Arthritis

History

• Pain, decreased mobility
• Weakness may be present if there is concurrent cuff tear
• History of other joint diseases
• Medications – DMARDs, Steroids
• Alcohol use
• PMH

Examination

• ROM
• Classically reduced/absent ER with GHJ OA
• Cuff assessment
• Deltoid function
• Concurrent upper limb arthritis (elbow in RA)

Imaging

• True AP of GHJ:
  • Type of arthrosis, evidence of AVN, features of cuff tear
• Axillary lateral:
  • Glenoid version, humeral head shape, subluxation
• CT scan:
  • Pre-requisite pre-operatively
  • Head shape
  • Glenoid erosion pattern
  • Degree of subluxation
• MRI Scan:
  • If AVN suspected is essential
  • If cuff tear suspected – especially for RA

Management Options for Shoulder Arthritis

Non-Operative

• Analgesia
• DMARDs
• GHJ steroid injections – long-term benefit limited – diagnostic value
• Activity Modifications
• Physiotherapy – little proven benefit

Surgical

Joint Sparing Procedures – more appropriate for young patients

• Arthroscopic debridement: Possible for very early arthritis
• Synovectomy: For RA arthroscopic – in early disease with minimal bone changes
• Soft tissue arthroplasty:
  • Interposition of meniscus, fascia lata, etc., into glenoid for pain relief
  • Some good results reported in young patients
  • Unlikely to have any long-term benefit
• Cartilage Procedures:
  • ACI, OATS have been reported for focal cartilage defects with some good results
  • Limited studies in the shoulder
  • Unlikely to work due to greater shear forces in shoulder from large ROM
• Procedures for AVN:
  • Core decompression, vascularised grafting
  • Core decompression does work in early AVN
  • Limited literature for shoulder and even less for vascularised grafts
• Arthrodesis:
  • An option for those with non-functional cuff or deltoid
  • 30 degrees abduction, IR, and flexion is position of choice

Arthroplasty

• Humeral Head Resurfacing:
  • Advantages for young patients – bone preservation
  • Easier revision
  • Less morbidity
  • Feasible for AVN up to 50% involvement of head but safer up to 30%
• Hemiarthroplasty:
  • An option for young patients
  • Can be used if there is an irreparable cuff tear
  • Problems: glenoid erosion and continued pain
• Total Shoulder Arthroplasty:
  • Gold Standard treatment
  • Glenoid Resurfacing contraindications:
    • Inadequate bone stock
    • Severe posterior erosion
    • Severe medial erosion
    • Rotator cuff deficient
  • Outcomes:
    • Superior long-term results to hemiarthroplasty
    • Improved ROM
    • Pain relief
  • Complications:
    • Glenoid loosening, wear, infection, instability, subscapularis failure