Rotator Cuff Arthropathy

Definition. Cuff tear arthropathy (CTA) is the end-stage of a chronic massive rotator cuff tear: loss of the cuff force couples allows the humeral head to migrate superiorly, eroding the acromion (acetabularization), rounding the greater tuberosity (femoralization) and finally destroying the glenohumeral joint. First characterised by Neer in 1983; the rapidly destructive crystal-driven variant is "Milwaukee shoulder".

• Who: Typically elderly (over 70 years), with a female predominance.
• Frequency: A minority of massive cuff tears progress to true arthropathy; estimated prevalence around 4% in cohorts over 70. Most massive tears remain functional ("suspension-bridge" compensation) without ever developing arthritis.
• Mechanism (two-hit): (1) mechanical loss of the force couple and superior stabiliser, plus (2) a nutritional/inflammatory element (decreased synovial fluid, basic calcium phosphate crystal release) contributing to cartilage loss.
• Natural history: Slow progression over years; pain and pseudoparalysis, not the radiographic grade alone, drive the decision to operate.

Relevant Anatomy

• Coracoacromial Arch: Becomes the new weight-bearing roof of the shoulder. Do NOT violate the CA ligament in CTA surgery (it is the only restraint against escape).
• Glenoid: Can become eroded superiorly ("E2 type wear").
• Subscapularis: Often intact in early stages but if torn, leads to anterior escape.
• Teres Minor: Critical for external rotation. If absent or fatty infiltrated (Hornblower's), a standard Reverse TSA will still result in an arm that cannot externally rotate (Latissimus Dorsi transfer may be added).
• Neurovascular Relations:
  • Axillary Nerve: Runs 5cm distal to the acromion. Travels through the quadrangular space with the posterior circumflex humeral artery.
  • Suprascapular Nerve: Travels through the suprascapular notch (under the transverse ligament) and spinoglenoid notch. Risk of injury during posterior glenoid retraction.
  • Cephalic Vein: The primary landmark for the deltopectoral approach. Preserving it reduces venous congestion.

Imaging Gallery

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Reverse Total Shoulder Arthroplasty (rTSA) The workhorse for CTA.

Biomechanics of Grammont Style Reverse

1. Medialization: Moves center of rotation medially. Increases the lever arm of the deltoid (recruits more fibers).
2. Distalization: Moves center of rotation distally. Retensions the deltoid.
3. Constraint: Semi-constrained design provides stability (replaces the cuff's function).

Indications

• CTA with pseudoparalysis.
• Massive unrepairable cuff tear.
• Failed Hemiarthroplasty/Total Arthroplasty.
• Proximal Humerus Malunion/Nonunion.

Contraindications

• Deltoid Paralysis (Axillary nerve injury).
• Active Infection.
• Glenoid Bone Deficiency (unable to hold baseplate screws).

Scapular Notching (Sirveaux Classification) Notching is a unique complication of Reverse TSA where the humeral cup abrades the inferior scapular neck during adduction.

• Grade 1: Defect involving pillar only.
• Grade 2: Defect contacting lower screw.
• Grade 3: Defect extending over lower screw.
• Grade 4: Defect extending to central peg (Threatening fixation).
• Prevention:
  • Lateralization: This is the most effective method.
    • Glenoid Side: Bony-metallic (BIO-RSA) or Metallic lateralization.
    • Humeral Side: Onlay stems or curved stems.
  • Inferior Overhang: Placing the glenosphere inferiorly prevents impingement in adduction.
  • Neck-Shaft Angle:
    • 155 degrees (Grammont original): High rate of notching.
    • 135 degrees (Modern): Reduces notching but increases shear force on the baseplate.

Acromial Stress Fracture

• Pathology: The deltoid is significantly tensioned. In elderly osteopenic patients, this stress can fracture the acromion or scapular spine.
• Diagnosis: Sudden onset pain after doing well for 3 months. X-ray might miss it (requires scapular views/CT).
• Consequence: Catastrophic. The deltoid origin becomes unstable. The "Reverse" stops working.
• Treatment: Conservative (High rate of non-union). ORIF has high failure rate.

Infection (Periprosthetic Joint Infection - PJI)

• Pathogen: Cutibacterium acnes (C. acnes) is the causative organism in over 60% of shoulder PJIs.
  • Biology: Gram-positive, anaerobic, slow-growing bacillus. Commensal on skin, specifically in sebaceous glands (which are dense in the shoulder region).
• Risk Factors: Male gender (more hair/sebum), younger age, prior surgery, topical steroids.
• Presentation: rarely presents with acute sepsis (fever/redness). Typical presentation is aggressive "stiffness" or unexplained "pain" after a period of doing well.
• Diagnosis:
  • Markers: ESR/CRP are often normal in C. acnes infection.
  • Aspiration: Dry taps are common.
  • Cultures: Must be held for minimum 14 days (up to 21 days).
  • Frozen Section: Over 50 PMNs per HPF is suggestive.
• Management:
  • DAIR (Debridement): Poor success rate for C. acnes. Only considered for acute hematogenous spread.
  • Two-Stage Revision: The Gold Standard.
    • Stage 1: Removal of all implants, thorough debridement, placement of antibiotic spacer (high dose Vancomycin/Gentamicin).
    • Antibiotics: 6 weeks of targeted therapy (often includes Rifampin for biofilm).
    • Stage 2: Reimplantation after antibiotic holiday and negative rescreen.

Neurological Injury

• Axillary Nerve: Most at risk during the inferior capsular release or from traction.
• Presentation: Deltid paralysis.
• Prognosis: Most are neurapraxias that resolve.
• Prevention: Identify the nerve. Keep the arm adducted while releasing inferiorly.

Across landmark series, RTSA reliably converts a painful pseudoparalytic shoulder into a functional, pain-free one, with Constant scores roughly doubling (Sirveaux 22.6 to 65.6; Wall 23 to 60).

• Elevation: Restore active elevation reliably (over 130 degrees).
• Rotation: External rotation is often not restored (0-10 degrees) unless Teres Minor is intact or Lat Dorsi transfer is done.
• Function: Patients can feed themselves and reach top of head, but reaching up back (IR) is limited.

Global registry trends. National joint registries worldwide (AOANJRR in Australia, NJR in England/Wales, the New Zealand Joint Registry, and Nordic registries) document the same shift: reverse TSA has overtaken hemiarthroplasty and anatomic TSA for the cuff-deficient shoulder and now accounts for the majority of all shoulder replacements in most developed health systems. Hemiarthroplasty for cuff deficiency has been largely abandoned because of unreliable pain relief and superior migration.

Revision and survivorship (registry-level).

• Primary reverse TSA shows roughly 90-95% survivorship at 10 years across large registries.
• Leading reasons for revision: infection (often the commonest early cause), instability/dislocation, and periprosthetic/acromial fracture.
• For an elderly primary CTA patient the lifetime risk of revision is low, so the implant typically outlasts the patient.

Implant and fixation notes.

• Metal-backed (screw-fixed) baseplates are standard for the reverse glenoid, in contrast to the cemented all-polyethylene glenoid used in anatomic TSA (where metal-backed designs failed early).
• Registries show no consistent difference between cemented and uncemented humeral stems for reverse TSA; modern uncemented HA-coated stems perform well.

Surgeon volume. A consistent volume-outcome relationship exists across registries: low-volume surgeons (broadly fewer than ~10 shoulder arthroplasties/year) have higher revision rates. Shoulder arthroplasty is increasingly a subspecialty procedure.

High- vs limited-resource practice variation.

• High-resource settings: ready access to reverse implants, CT-based planning, navigation/patient-specific instrumentation (used in a substantial minority of cases to reduce glenoid-placement outliers), and stemless/short-stem options (faster uptake in Europe).
• Limited-resource settings: reverse implants may be unavailable or unaffordable; arthroscopic debridement, biceps tenotomy, partial cuff repair, or even glenohumeral arthrodesis remain pragmatic salvage options for pain in the cuff-deficient arthritic shoulder.