import { OnePagerSummary, ExamWarning, InfoCardGrid, InfoCard, MnemonicCard, EvidenceCard, VivaScenarioSection, VivaScenario, ExamCheatSheet, ContentSection, ExamPearl, SafetyAlert, NumberHighlightRow, NumberHighlight, Tabs, Tab, ComparisonTable } from '@/components/mdx' **Deltoid Origin**. Arises from lateral clavicle, acromion, and scapular spine. Excessive anterior or lateral bone resection causes detachment. Stay 5mm from acromion edge. Preserve 8mm acromion thickness. **Axillary Nerve**. Exits quadrangular space, wraps around surgical neck of humerus. Located 5cm distal to acromion. Lateral portal must be less than 4cm from acromion edge. Use outside-in technique for safety. **Coracoacromial (CA) Ligament**. Attaches to anterolateral undersurface of acromion, runs to lateral coracoid. Part of superior constraint. PRESERVE in massive irreparable cuff tears. **Acromioclavicular Joint**. Medial to lateral acromion. Do not violate during acromioplasty unless performing concurrent distal clavicle excision. Assess for AC joint arthritis preoperatively. **Absolute Indications:** - Subacromial impingement refractory to conservative treatment for more than 6 months - Positive impingement signs (Neer, Hawkins) with more than 50% relief from diagnostic subacromial injection - Type II/III acromion morphology with mechanical impingement - Concurrent with rotator cuff repair to optimize subacromial space **Relative Indications:** - Subacromial bursitis with failed conservative management - AC joint osteophyte impingement (with distal clavicle excision) - Os acromiale causing impingement (with stabilization) **Evidence Note:** CSAW trial (Lancet 2018) showed no benefit of isolated SAD over arthroscopy-only or observation for subacromial pain without full-thickness cuff tear. Modern practice increasingly performs SAD concurrently with cuff repair rather than as isolated procedure. **Absolute Contraindications:** - Inadequate trial of conservative management (less than 6 months) - Massive irreparable cuff tear with superior migration (CA arch release would worsen instability) - Active infection - Alternative pain generator not addressed (cervical radiculopathy, AC arthritis) **Relative Contraindications:** - Stiff shoulder (capsulitis - may need MUA first) - Workers' compensation/litigation (poor outcomes documented) - Unclear diagnosis (no improvement with diagnostic injection) - Elderly patient with massive cuff tear (may need reverse TSA not SAD) **Clinical Assessment:** - Positive impingement signs: Neer (forward flexion), Hawkins (internal rotation at 90 degrees) - Diagnostic subacromial injection: More than 50% pain relief for duration of local anaesthetic confirms subacromial source - Exclude alternative sources: AC joint, biceps, cervical spine **Imaging:** - AP, axillary lateral, supraspinatus outlet (Y-view) radiographs - Outlet view assesses acromion morphology (Bigliani type) - MRI to assess rotator cuff, exclude full-thickness tear requiring repair - Consider CT if os acromiale suspected **Planning Points:** - Bigliani acromion type (I flat, II curved, III hooked) - AC joint arthritis - need concurrent distal clavicle excision? - Rotator cuff status - repair concurrently? - Patient expectations - counsel regarding CSAW trial outcomes **Arthroscopy Equipment:** - 30-degree arthroscope (4mm) - Fluid pump (pressure 40-60 mmHg) - Arthroscopic shaver (4.0-5.5mm aggressive cutter) - Arthroscopic burr (5.5mm acromionizer) - Electrocautery (radiofrequency device) - Cannulas for working portals **Positioning:** - Beach chair position (65-80 degrees) - more common in Australia - OR lateral decubitus with traction - Pneumatic arm holder or traction system - Head ring for beach chair **Instruments:** - Spinal needle for portal localization - Switching sticks - Basket forceps for CA ligament if releasing ### Subacromial Space Anatomy The subacromial space is the potential space between: - **Superiorly**: Undersurface of acromion, coracoacromial ligament, AC joint - **Inferiorly**: Superior surface of rotator cuff (supraspinatus, infraspinatus) - **Contents**: Subacromial bursa (largest bursa in body) **Normal dimensions**: - Acromiohumeral interval: 9-10mm (reduced to less than 7mm = impingement) - Acromion thickness: 8-10mm (minimum 8mm must be preserved) ### Bigliani Classification of Acromion Morphology | Type | Morphology | Impingement Risk | |------|------------|------------------| | I | Flat undersurface | Lowest | | II | Curved undersurface | Moderate | | III | Hooked anterior undersurface | Highest | Type III hooked acromion is found in 40% of patients with rotator cuff tears versus 3% of normal shoulders. ### Coracoacromial (CA) Arch - **Coracoid process** - medial attachment of CA ligament - **CA ligament** - thick fibrous band running from coracoid to anterolateral acromion undersurface - **Acromion** - lateral attachment of CA ligament **Function**: Provides superior constraint to humeral head. In massive cuff tear, CA arch is the only remaining superior stabilizer - preventing anterosuperior escape. ### Key Distances - **Axillary nerve**: 5cm distal to acromion (lateral portal must be less than 4cm) - **Deltoid origin**: Anterior and lateral acromion edges (preserve 5mm from edges) - **Safe acromion thickness**: Minimum 8mm must remain after acromioplasty **Patient Position Options:** **Beach Chair Position (Preferred in Australia):** - Patient 65-80 degrees upright - Head secured in padded head ring - Arm in pneumatic arm holder allowing full ROM - Advantages: Easier conversion to open if needed, familiar orientation - Disadvantages: Risk of hypotensive events (cerebral hypoperfusion) **Lateral Decubitus Position:** - Patient 90 degrees lateral - Axillary roll placed under dependent axilla - Arm in traction (5-10 pounds) with abduction 45 degrees, forward flexion 15 degrees - Advantages: Better distraction for cuff repair - Disadvantages: Unfamiliar orientation, difficult to convert to open **Examination Under Anaesthesia:** - Document ROM (may reveal stiffness not apparent when awake) - Assess stability (instability may change diagnosis) **Anatomic Landmark Marking:** - Acromion borders (anterior, lateral, posterior) - Clavicle and AC joint - Coracoid process - Portal sites (posterior, lateral, anterior if needed) **Preparation:** - Confirm arthroscopy equipment functional - Ensure fluid pump, shaver, burr available - Check epinephrine in irrigation (1:1,000,000 for haemostasis) ### Step 1: Portal Establishment - Posterior Portal Establish posterior viewing portal first: **Technique:** - Mark posterior portal site: "Soft spot" 2cm inferior and 2cm medial to posterolateral acromion corner - Make 5mm skin incision with #11 blade - Blunt dissect through deltoid with artery forceps - Insert trocar aimed toward coracoid (neurovascular structures are medial) - Feel "pop" as capsule penetrated - Insert 30-degree arthroscope - Inflate joint with fluid (pump pressure 40-60 mmHg) **Technical Tip**: EXAM KEY - Posterior portal is primary viewing portal. "Soft spot" is palpable depression posterior to acromion. Aim toward coracoid to stay safe from neurovascular structures. Glenohumeral inspection first rules out other pathology. - Aim too medial = glenoid or labral injury - Aim too lateral = articular cartilage damage ### Step 2: Systematic Glenohumeral Arthroscopy Perform systematic glenohumeral joint inspection before subacromial work: **Inspection Checklist:** 1. Biceps tendon - tendinitis, subluxation, tears (consider tenotomy if more than 50% torn) 2. Rotator interval and coracohumeral ligament 3. Subscapularis - tears especially upper portion (hidden lesions) 4. Labrum (anterior, superior, posterior) - instability, SLAP tears 5. Glenoid and humeral head articular surfaces 6. Inferior recess - adhesive capsulitis, loose bodies 7. Articular side of rotator cuff - partial thickness tears **Technical Tip**: EXAM KEY - Isolated subacromial impingement is increasingly rare. Most patients have concurrent pathology. Finding alternative pain generator (labral tear, biceps pathology, arthritis) may change surgical plan. ### Step 3: Enter Subacromial Space Redirect arthroscope from glenohumeral joint to subacromial space: **Technique:** - Withdraw scope slightly from GH joint (do not exit skin) - Angle scope posteriorly and superiorly - Enter subacromial bursa (space between acromion and cuff) - Inflate space with fluid - Expect thickened inflamed bursa in chronic impingement (versus thin filmy normal bursa) **Technical Tip**: EXAM KEY - Same posterior portal, just redirected. Normal bursa is thin and filmy (less than 1mm). Chronic impingement bursa is thick (5-10mm) and inflamed. ### Step 4: Lateral Working Portal Establishment Establish lateral working portal using outside-in technique: **Technique:** - Visualize lateral acromion edge from inside - Use spinal needle to localize portal position under direct vision - Optimal position: 3-4cm distal to lateral acromion edge (NEVER more than 4cm = axillary nerve risk) - Make skin incision, blunt dissect through deltoid - Insert cannula under direct vision **Technical Tip**: EXAM KEY - Outside-in technique with spinal needle prevents neurovascular injury. Axillary nerve is 5cm from acromion - lateral portal must be less than 4cm from acromion edge. Cannula maintains portal patency and prevents fluid extravasation. - Portal more than 4cm from acromion = axillary nerve at risk - Portal too anterior = impingement with instruments on acromion ### Step 5: Subacromial Bursectomy Thorough bursectomy is essential for visualization: **Technique:** - Insert shaver (4.0-5.5mm aggressive cutter) through lateral portal - Systematically resect inflamed bursa starting posteriorly - Work from posterior to anterior, medial to lateral - Continue until clearly visualizing: - Undersurface of acromion (entire surface) - Bursal surface of rotator cuff - CA ligament anteriorly - AC joint medially - All acromion borders **Technical Tip**: EXAM KEY - Thorough bursectomy takes 10-20 minutes in chronic bursitis but is CRITICAL for adequate visualization. Inadequate bursectomy leads to poor visualization, incomplete decompression, and bleeding obscuring view. ### Step 6: Identify Anatomic Landmarks Before bone work, clearly identify acromion boundaries: **Technique:** - Use spinal needle from outside to localize borders - Mark borders with electrocautery on bone surface - Identify: - Anterior edge (CA ligament attaches here) - Lateral edge (deltoid origin) - Posterior edge (at posterior portal level) - Medial edge (AC joint - do not violate) **Acromion morphology assessment:** - Type I flat: Minimal resection needed - Type II curved: Remove curved undersurface - Type III hooked: Remove anterior hook (most bone work) **Technical Tip**: EXAM KEY - Mark borders BEFORE burring. Most errors are over-resection anteriorly (deltoid detachment) or laterally (deltoid detachment). Use spinal needle to correlate external palpation with internal visualization. ### Step 7: Acromioplasty - Bone Resection Flatten undersurface of acromion to Type I morphology: **Technique:** - Insert arthroscopic burr (5.5mm acromionizer) through lateral portal - Work from POSTERIOR (safe) to ANTERIOR (danger zone) - Use lateral edge as reference plane - resect undersurface to this level - Remove: - Curved undersurface (Type II) - Anterior hook (Type III) - Anterior/anterolateral osteophytes - Extend medially to AC joint (do not violate) **Typical bone removal:** - Anterior: 5-8mm - Lateral: 2-5mm - Posterior: Minimal **Critical safety margins:** - Stay 5mm from anterior edge (deltoid origin) - Preserve 8mm minimum acromion thickness (prevents fracture) **Technical Tip**: EXAM KEY - Goal is flat Type I acromion, not excessive resection. "Cutting block technique": Use lateral edge as guide for resection level. Most errors: Under-resection anteriorly (residual hook) or over-resection laterally (deltoid detachment). - Over-resection anterior = deltoid detachment - Over-resection lateral = deltoid detachment - Excessive thinning = acromial fracture - Under-resection = persistent impingement ### Step 8: CA Ligament Management CA ligament release versus preservation is controversial: **Option 1: Release (Traditional)** - Release CA ligament from anterior acromion using electrocautery or basket forceps - Allows more aggressive anterior decompression - Most published studies used this approach **Option 2: Preservation (Modern Trend)** - Stop acromioplasty 5-8mm from anterior edge - Preserves CA ligament attachment - Maintains superior constraint - Recommended if massive cuff tear present **CONTRAINDICATION to release:** - Known massive irreparable cuff tear - Significant cuff tear with superior migration - Would lead to anterosuperior escape (loss of superior stability) **Technical Tip**: EXAM KEY - No consensus on CA ligament management. Key point: NEVER release in massive irreparable cuff tear. If concurrent cuff repair, consider preservation. Be able to state your preference and rationale in exam. ### Step 9: Assess Adequacy of Decompression Verify adequate decompression before finishing: **Adequacy Tests:** 1. **Visual assessment**: Smooth flat undersurface, no residual hook/osteophytes 2. **Arthroscope rotation test**: Rotate scope 360 degrees from lateral portal - should not contact acromion 3. **Instrument passage**: Shaver/burr should pass freely under acromion 4. **Fluoroscopy** (if available): Lateral outlet view shows flat profile **Common areas of incomplete decompression:** - Anterolateral corner (difficult to reach) - Extreme anterior hook (fear of deltoid detachment) - Medial near AC joint **Technical Tip**: EXAM KEY - If instruments still impinge during passage, decompression is inadequate. Smooth all rough bone edges - rough bone causes postoperative crepitus and pain. Consider viewing from anterior portal to assess lateral adequacy. ### Step 10: AC Joint Assessment Assess AC joint and treat if contributing to impingement: **Assessment:** - Visualize AC joint from posterior or anterior portal - Look for inferior osteophytes impinging on cuff - AC joint arthritis with synovitis - AC joint instability **If AC pathology present:** Perform concurrent distal clavicle excision (Mumford procedure): - Resect 1.0-1.5cm of distal clavicle from inferior - Preserve superior AC capsule and ligaments (stability) - 1.0cm minimum (prevent bone healing across joint) - 1.5cm maximum (prevent instability) **Technical Tip**: EXAM KEY - AC joint pathology common in patients over 50 years. May be primary pain generator rather than subacromial impingement. Preoperative AC joint injection test helps differentiate. ### Step 11: Rotator Cuff Assessment After decompression, thoroughly inspect rotator cuff: **Assessment:** - Bursal surface of supraspinatus, infraspinatus - Identify tears (partial or full thickness) - Assess tear pattern: Crescent, L-shaped, U-shaped, massive - Determine reparability: Can edges reach footprint without tension? **If repairable tear found:** - Proceed with arthroscopic cuff repair (separate procedure) - SAD provides optimal environment for cuff healing **If irreparable tear:** - Document and counsel patient - Options: Debridement, superior capsular reconstruction, patch, reverse TSA for massive with pseudoparalysis **Technical Tip**: EXAM KEY - Isolated SAD (no cuff tear) is uncommon (10-20%). Most patients have concurrent cuff pathology. CSAW trial questions efficacy of isolated SAD. Modern practice: SAD usually performed with cuff repair, rarely in isolation. ### Step 12: Haemostasis and Final Inspection Achieve haemostasis before closure: **Technique:** - Reduce pump pressure to 40mmHg (identify bleeding vessels) - Cauterize bleeding points with electrocautery - Final systematic inspection from multiple portals - Ensure no instrument breakage or loose bodies - Document with arthroscopic images - Unrecognized bleeding = postoperative haematoma - Retained fragment = loose body ### Step 13: Portal Closure Close arthroscopic portals: **Technique:** - Remove cannulas under direct vision - Allow fluid to drain (compress gently) - Portal closure: Interrupted absorbable sutures or Steri-strips for small portals - Apply sterile absorbent dressing (significant fluid leakage expected 24-48 hours) - Cold therapy device or ice pack - Sling for comfort (NOT immobilization) ### Step 14: Post-operative Protocol Early ROM is critical for isolated SAD (no healing constraint): **Immediate (Day 1):** - Pendulum exercises - Passive ROM - Sling for comfort only (wean quickly) **Week 1-2:** - Active-assisted ROM all planes - Continue passive stretching - Discontinue sling **Week 4-6:** - Begin strengthening - Resistance exercises **Week 6-12:** - Advance strengthening - Return to normal activities - Sports by 8-12 weeks **Note**: If concurrent cuff repair, protocol modified to protect repair (restricted ROM first 6 weeks). **Technical Tip**: EXAM KEY - Post-op protocol for isolated SAD very different from cuff repair. No healing constraint so immediate full ROM allowed. Sling 24-48 hours maximum. Return to work: 1-2 weeks (sedentary), 4-6 weeks (heavy labour). **Week 1:** - Pendulum exercises, passive ROM - Sling for comfort only (discard by end of week) - Portal wound care (expect significant fluid drainage) - Ice, elevation, analgesia **Weeks 1-4:** - Progress to active-assisted then active ROM - Full ROM target by 4 weeks - Swimming/water exercises excellent **Weeks 4-8:** - Begin resistance exercises - Rotator cuff and periscapular strengthening - Progressive return to activities **Weeks 8-12:** - Advance strengthening - Return to sports and heavy labour - Full recovery expected by 3 months **Follow-up:** - 2 weeks: Wound check, ROM assessment - 6 weeks: Progress check, may discharge if doing well - 3 months: Final outcome assessment **Expected Outcomes:** - 80-90% good-excellent results in appropriately selected patients - CSAW trial data suggests isolated SAD (no cuff tear) may have no benefit over observation - Best outcomes when combined with cuff repair 1. Beard DJ, Rees JL, Cook JA, et al. Arthroscopic subacromial decompression for subacromial shoulder pain (CSAW): a multicentre, pragmatic, parallel group, placebo-controlled, three-group, randomised surgical trial. *Lancet*. 2018;391(10118):329-338. 2. Bigliani LU, Levine WN. Subacromial impingement syndrome. *J Bone Joint Surg Am*. 1997;79(12):1854-1868. 3. Neer CS 2nd. Anterior acromioplasty for the chronic impingement syndrome in the shoulder: a preliminary report. *J Bone Joint Surg Am*. 1972;54(1):41-50. 4. Hawkins RJ, Kennedy JC. Impingement syndrome in athletes. *Am J Sports Med*. 1980;8(3):151-158. 5. Gartsman GM. Arthroscopic acromioplasty for lesions of the rotator cuff. *J Bone Joint Surg Am*. 1990;72(2):169-180. 6. Codman EA. Rupture of the supraspinatus tendon and other lesions in or about the subacromial bursa. In: *The Shoulder*. Boston: Thomas Todd Company; 1934:262-312. 7. Ellman H. Arthroscopic subacromial decompression: analysis of one- to three-year results. *Arthroscopy*. 1987;3(3):173-181. 8. Papadonikolakis A, McKenna M, Warme W, Martin BI, Matsen FA 3rd. Published evidence relevant to the diagnosis of impingement syndrome of the shoulder. *J Bone Joint Surg Am*. 2011;93(19):1827-1832. 9. Burkhart SS, Lo IK, Brady PC. A cowboy's guide to advanced shoulder arthroscopy. *Lippincott Williams & Wilkins*. 2006. 10. Gazielly DF, Gleyze P, Montagnon C. Functional and anatomical results after rotator cuff repair. *Clin Orthop Relat Res*. 1994;(304):43-53.

Subacromial Decompression (Arthroscopic)

Subacromial Decompression (Arthroscopic)