import { OnePagerSummary, ContentSection, ExamWarning, InfoCardGrid, InfoCard, EvidenceCard, ComparisonTable, VivaScenario, MnemonicCard, ExamCheatSheet, Tab, Tabs } from '@/components/mdx' {/* SECTION 1: ONE-PAGER SUMMARY */} {/* SECTION 2: EXAM WARNING */} **THE SINGLE MOST IMPORTANT CONCEPT.** The axillary nerve runs in the **quadrangular space** (bordered by teres minor superiorly, teres major inferiorly, long head triceps medially, surgical neck humerus laterally). It emerges **5-6cm inferior to the lateral acromion** (Burkhead 1992 study: mean 5.4cm, range 4.5-7cm). **NEVER split deltoid more than 5cm distal to acromion.** Axillary nerve injury (3-5% incidence) causes **deltoid paralysis** (inability to abduct shoulder) and **sensory loss** over lateral shoulder (badge area). Prevention: strict adherence to 5cm rule, blunt dissection in deltoid-splitting interval, mark 5cm distance on skin before incision. Common exam mistake. The posterior and middle deltoid fibers are BOTH innervated by the **axillary nerve** (terminal branches). This is **NOT a true internervous plane.** The split is safe because: (1) Axillary nerve enters deltoid deep (from quadrangular space), (2) Terminal branches run horizontally in muscle belly, (3) Split is parallel to fibers and nerve branches. However, the **5cm rule MUST be respected** to stay proximal to main nerve trunk. After deltoid split, the next layer is the **infraspinatus-teres minor interval.** This IS a true internervous plane: **infraspinatus** (suprascapular nerve) superiorly, **teres minor** (axillary nerve) inferiorly. Develop this interval by blunt dissection between the two muscles to access the posterior capsule and glenohumeral joint. The interval is identified by palpating the **spine of scapula** (infraspinatus above, teres minor below). This interval is safe - no nerve crosses it. Adequate glenoid exposure is critical for reverse TSA component positioning. After capsulotomy, use **Fukuda retractor** (humeral head retractor) to displace humeral head posteriorly and inferiorly. **Release inferior capsule** and **release conjoint tendon from coracoid** (if needed) to improve exposure. **Lateral positioning** provides better glenoid visualization than beach chair (gravity helps retract humeral head), but conversion to anterior approach is difficult if needed. {/* SECTION 3: DECISION GUIDE */} {/* SECTION 4: SURGICAL ANATOMY */} ### Surface Landmarks **Acromion:** The **posterolateral corner of the acromion** is the primary landmark for the posterior approach. It is palpable as a bony prominence at the superior aspect of the shoulder. The **5cm rule** is measured from this point distally along the posterior deltoid. **Spine of scapula:** The **spine of scapula** is palpable as a bony ridge running from the vertebral border of scapula laterally to the acromion. It separates the supraspinous fossa (above) from the infraspinous fossa (below). The spine of scapula guides the surgeon to the **infraspinatus-teres minor interval** (infraspinatus above the spine, teres minor below). **Posterior axillary fold:** The **posterior axillary fold** is formed by the **teres major** muscle and **latissimus dorsi** tendon. This is the inferior border of the posterior shoulder and marks the approximate level of the **axillary nerve** in the quadrangular space. ### Skin and Subcutaneous Tissue **Skin incision:** The incision is centered over the **posterolateral corner of the acromion** and extends distally along the **posterior deltoid fibers** for 6-8cm (depending on patient size and planned procedure). For reverse TSA, a **8-10cm incision** provides adequate exposure. **Subcutaneous tissue:** Relatively thin over the posterior shoulder (compared to anterior shoulder which has thicker subcutaneous fat). The **cutaneous nerves** (supraclavicular nerves from cervical plexus) cross the superior aspect of incision - these are small sensory nerves and can be sacrificed or retracted. ### Deltoid Muscle **Anatomy:** The deltoid has three functional parts: 1. **Anterior deltoid** (clavicular origin) - flexion and internal rotation 2. **Middle deltoid** (acromial origin) - primary abductor (most important function) 3. **Posterior deltoid** (scapular spine origin) - extension and external rotation **Innervation:** The **axillary nerve** (C5-6) innervates the ENTIRE deltoid muscle. The nerve enters the deltoid from its **deep surface** after exiting the quadrangular space. It divides into **anterior and posterior branches** that run horizontally in the muscle belly, innervating anterior/middle deltoid and posterior deltoid respectively. **Deltoid-splitting interval:** The posterior approach splits deltoid **between posterior and middle fibers** (in line with posterior deltoid muscle fibers). This split is **parallel to neurovascular bundles** (terminal nerve branches run horizontally in muscle), making it safe provided the **5cm rule** is observed. **Deltoid reattachment:** At closure, the deltoid split is repaired with **interrupted No. 2 Ethibond or FiberWire sutures** (strong, non-absorbable). Side-to-side repair of deltoid fibers with mattress sutures. The repair is robust if split less than 5cm - no need for bone tunnels or suture anchors (unlike deltoid detachment approaches). ### Axillary Nerve - Critical Anatomy **Course:** The axillary nerve originates from the **posterior cord of brachial plexus** (C5-6 roots). It exits the axilla via the **quadrangular space** along with the **posterior humeral circumflex artery (PHCA)**. **Quadrangular space borders:** 1. **Superior:** Teres minor muscle (and sometimes inferior border of subscapularis) 2. **Inferior:** Teres major muscle 3. **Medial:** Long head of triceps 4. **Lateral:** Surgical neck of humerus (bone) **Distance from acromion:** The axillary nerve exits the quadrangular space at a mean distance of **5.4cm inferior to the lateral acromion** (Burkhead 1992 cadaveric study: range 4.5-7cm in 200 shoulders). In clinical practice, the **5cm rule** provides a margin of safety. **Nerve branches:** After exiting quadrangular space, the axillary nerve divides into: 1. **Anterior (superior) branch:** Innervates anterior and middle deltoid (motor), provides articular branches to glenohumeral joint 2. **Posterior (inferior) branch:** Innervates posterior deltoid and teres minor (motor), gives off superior lateral brachial cutaneous nerve (sensation over lateral shoulder - "badge area") **Clinical significance:** Axillary nerve injury causes: 1. **Motor deficit:** Deltoid paralysis (inability to abduct shoulder beyond initial 15° from supraspinatus, profound disability) 2. **Sensory deficit:** Numbness over lateral shoulder ("badge area") 3. **Functional loss:** Cannot lift arm away from body, severe limitation in ADLs **Quadrangular space syndrome:** Rare condition (compression of axillary nerve and PHCA in quadrangular space). Causes: fibrous bands, teres minor hypertrophy (overhead athletes), trauma. Symptoms: vague shoulder pain, paresthesias in axillary nerve distribution, exacerbated by shoulder abduction and external rotation. ### Rotator Cuff Muscles - Posterior Layer **Infraspinatus:** - **Origin:** Infraspinous fossa of scapula (below spine of scapula) - **Insertion:** Greater tuberosity of humerus (middle facet of GT, posterior to supraspinatus insertion) - **Function:** External rotation of shoulder (primary external rotator), stabilizes humeral head - **Innervation:** Suprascapular nerve (C5-6 from superior trunk of brachial plexus) **Teres minor:** - **Origin:** Lateral border of scapula (upper two-thirds) - **Insertion:** Greater tuberosity of humerus (inferior facet of GT, inferior to infraspinatus) - **Function:** External rotation and adduction of shoulder - **Innervation:** Axillary nerve (C5-6) - **teres minor is the ONLY rotator cuff muscle NOT innervated by suprascapular nerve** **Infraspinatus-teres minor interval:** The interval between infraspinatus (superior) and teres minor (inferior) is a **TRUE internervous plane** (suprascapular nerve vs axillary nerve). This interval is safe for dissection and provides access to the posterior glenohumeral joint capsule. Develop the interval by blunt dissection (finger or Cobb elevator) parallel to muscle fibers. **Teres major (NOT a rotator cuff muscle):** - **Origin:** Inferior angle of scapula - **Insertion:** Medial lip of bicipital groove (humerus) - **Function:** Adduction, internal rotation, extension of shoulder - **Innervation:** Lower subscapular nerve (C5-7) - **Clinical significance:** Forms inferior border of quadrangular space (below teres minor) ### Posterior Glenohumeral Joint Capsule **Anatomy:** The **posterior capsule** attaches to the glenoid rim posteriorly and to the anatomic neck of humerus medially (just lateral to articular surface). The capsule is reinforced by rotator cuff tendons (infraspinatus and teres minor) superiorly and inferiorly. **Capsular thickening:** Unlike the anterior capsule (which has distinct glenohumeral ligaments - superior, middle, inferior), the **posterior capsule is relatively THIN** and has less distinct ligamentous reinforcement. The posterior band of the **inferior glenohumeral ligament** (IGHL) runs posteroinferiorly but is less developed than the anterior band. **Capsulotomy:** For arthroplasty or posterior instability surgery, a **posterior capsulotomy** is performed. The capsule is incised vertically just lateral to the glenoid rim (leaves a cuff of capsule on glenoid for later repair). The humeral-sided capsule is preserved when possible for stability. **Posterior labrum:** The **glenoid labrum** (fibrocartilaginous ring around glenoid rim) is less robust posteriorly than anteriorly. **Posterior labral tears** occur in posterior instability (associated with reverse Hill-Sachs lesion). The posterior labrum is visible after capsulotomy and can be repaired with suture anchors if torn. ### Vascular Anatomy **Posterior humeral circumflex artery (PHCA):** The PHCA is a branch of the **axillary artery** (third part, distal to pectoralis minor). It travels with the **axillary nerve** through the **quadrangular space** to supply the deltoid, teres minor, and long head of triceps. **Circumflex scapular artery:** Branch of the **subscapular artery** (which comes off axillary artery). The circumflex scapular artery passes posteriorly around the lateral scapular border (through the triangular space, inferior to teres minor, NOT the quadrangular space). It supplies the infraspinatus and posterior scapular muscles. **Bleeding points:** The posterior approach has **moderate bleeding** from muscular branches of PHCA and circumflex scapular artery. Control with **bipolar cautery** during deltoid split and muscle dissection. The main trunks of these vessels are NOT directly encountered (they are deep to the muscles) unless dissection extends too far medially or inferiorly. ### Glenohumeral Joint Anatomy **Glenoid:** The glenoid is the **shallow socket** of the glenohumeral joint (pear-shaped, wider inferiorly than superiorly). The glenoid **version** (orientation in axial plane) is normally **7-10° retroverted** (posterior tilt). Excessive retroversion (greater than 15°) increases posterior instability risk. **Humeral head:** The humeral head is **spherical** (30-35° arc in both coronal and sagittal planes) in anatomic shoulder. The humeral head has **130-135° inclination** (neck-shaft angle) and **20-30° retroversion** relative to the transepicondylar axis of the elbow. **Rotator cuff tear arthropathy:** Chronic massive rotator cuff tear (involving supraspinatus and infraspinatus) leads to **superior migration** of humeral head (loss of cuff depressor function), causing **contact between humeral head and acromion** (abrasion, erosion of humeral head and glenoid). This is the primary indication for reverse TSA. **Reverse TSA biomechanics:** Reverse TSA inverts the ball-socket relationship (glenosphere on glenoid, humeral socket on humerus). This **medializes and distalizes the center of rotation**, increasing the **deltoid moment arm** (allows deltoid alone to abduct shoulder without functional rotator cuff). The design compensates for rotator cuff deficiency. {/* SECTION 5: INDICATIONS */} ### Indications **1. Reverse total shoulder arthroplasty (70% of posterior approach cases):** **Primary indication:** **Cuff tear arthropathy** (Hamada grade 3-5: massive rotator cuff tear with glenohumeral arthritis and superior humeral head migration). Patients are typically elderly (70+ years) with chronic cuff tears, severe pain, and functional disability (pseudoparalysis - cannot actively elevate arm). **Other indications for reverse TSA:** - **Massive irreparable rotator cuff tear** with pseudoparalysis (no arthritis, but profound functional loss) - **Failed rotator cuff repair** with re-tear and pseudoparalysis - **Proximal humerus fracture sequelae** in elderly (malunion, nonunion, avascular necrosis) - **Revision arthroplasty** with rotator cuff deficiency (failed anatomic TSA with cuff tear) - **Inflammatory arthritis** (rheumatoid arthritis) with rotator cuff insufficiency **AOANJRR data (Australia):** Reverse TSA now accounts for **70% of all shoulder arthroplasties** (vs 30% anatomic TSA). This reflects aging population and expanded indications for reverse TSA. Outcomes: 92-95% good-excellent at 5 years, 10-year implant survival 90%. **2. Massive posterosuperior rotator cuff tears (20% of cases):** **Open or arthroscopic-assisted rotator cuff repair** for massive tears involving **infraspinatus and teres minor**. The posterior approach provides excellent visualization of posterior cuff (unlike anterior deltopectoral approach which has poor posterior cuff access). **Indications for open repair:** - **Retracted tears** (greater than 5cm retraction, Patte stage III) - **Revision cuff repair** (after failed arthroscopic repair) - **Poor tissue quality** (elderly, chronic tear) **Arthroscopic cuff repair** is now preferred for most tears, but posterior open approach is still used for complex cases or when arthroscopic repair not feasible. **3. Posterior shoulder instability (5% of cases):** **Recurrent posterior dislocation** or **posterior subluxation**. Causes: - **Atraumatic:** Generalized ligamentous laxity, excessive glenoid retroversion (greater than 15°), posterior labral insufficiency - **Traumatic:** Seizure (epilepsy, electroconvulsive therapy), electrical injury (lightning, electrical shock), posterior blow to shoulder **Reverse Hill-Sachs lesion:** Anterior dislocation causes posterolateral humeral head impression fracture (**Hill-Sachs lesion**). Posterior dislocation causes **ANTEROMEDIAL humeral head impression fracture** (reverse Hill-Sachs or McLaughlin lesion). Large reverse Hill-Sachs lesions (greater than 40% of articular surface) engage the posterior glenoid during internal rotation, causing recurrent instability. **Surgical options:** - **Posterior labral repair** (suture anchors) for isolated labral tear - **Posterior capsular plication** for capsular laxity - **Bone block** (posterior glenoid bone graft) for glenoid bone loss or excessive retroversion - **Reverse Hill-Sachs reconstruction** (subscapularis tendon transfer into defect - McLaughlin procedure, OR lesser tuberosity osteotomy transfer) **4. Proximal humerus fracture fixation (5% of cases):** Posterior approach can be used for **posterior plate fixation** of proximal humerus fractures (alternative to lateral or deltopectoral approaches). Less common now with increased use of reverse TSA for complex fractures in elderly. ### Contraindications **Absolute:** 1. **Active infection** (septic arthritis, osteomyelitis) - stage 1: debridement and antibiotics, stage 2: arthroplasty after infection cleared (6+ weeks) 2. **Deltoid paralysis** from prior axillary nerve injury - reverse TSA will NOT work without functional deltoid 3. **Brachial plexus injury** affecting C5-6 (deltoid and rotator cuff paralyzed) - arthroplasty futile **Relative:** 1. **Young age** (less than 60 years) for reverse TSA - consider anatomic TSA if cuff intact, or cuff repair/augmentation if cuff torn. Reverse TSA in young patients has higher failure rate (glenoid loosening, instability, scapular notching) 2. **Good rotator cuff function** - anatomic TSA preferred if cuff intact (reverse TSA is for cuff-deficient shoulders) 3. **Severe glenoid bone loss** (greater than 50% of glenoid) - may need bone grafting before arthroplasty, or custom implants 4. **Prior posterior approach surgery** with extensive scarring - higher risk of axillary nerve injury, consider alternative approach (deltopectoral) 5. **Obesity** (BMI greater than 35) - higher infection risk, poorer functional outcomes ### Australian Context **Medicare coverage:** Reverse TSA covered for: - **Cuff tear arthropathy** (Hamada grade 3-5) - **Massive irreparable cuff tear** with pseudoparalysis (documented loss of active elevation, failed conservative management 6+ months) - **Proximal humerus fracture** in elderly (70+ years) with comminution (3- or 4-part fracture) - **Failed rotator cuff repair** with re-tear and functional loss **AOANJRR registry:** All shoulder arthroplasties in Australia must be reported to **Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR)**. This provides outcome data on implant performance, revision rates, and complications. **Return to function:** - **Light activities** (self-care, dressing): 6-12 weeks - **Driving**: 6-8 weeks (when off opioids and can control steering wheel) - **Recreational activities** (golf, swimming): 3-6 months - **Heavy lifting**: Avoid permanently (reverse TSA is NOT designed for heavy manual labor) **WorkCover:** Reverse TSA for work-related rotator cuff injury is controversial (most patients are elderly and not working). If performed in working-age patient, return to LIGHT work at 3-6 months, but manual labor is contraindicated (risk of glenoid loosening, instability). {/* SECTION 6: PATIENT POSITIONING */} ### Beach Chair Position (Most Common) **Advantages:** 1. **Easier anesthesia access** to airway and monitoring 2. **Conversion to anterior approach** possible if needed (can do deltopectoral approach from same position) 3. **Familiar positioning** for most surgeons 4. **Physiologic blood pressure** (head elevated reduces risk of cerebral hypoperfusion compared to lateral) **Disadvantages:** 1. **Less glenoid exposure** compared to lateral (gravity does not assist with humeral head retraction) 2. **Risk of cerebral hypoperfusion** if head too elevated or blood pressure not maintained (controversial) **Setup:** 1. **Head positioning:** Secure head with padded headrest. Elevate head of bed **30-45°** (semi-sitting position) 2. **Operative shoulder:** Position shoulder at edge of bed (allows extension, adduction, manipulation of arm without bed interference) 3. **Arm positioning:** Arm free and mobile (NOT tucked). Use **arm positioner** (e.g., McConnell arm holder, Spider arm positioner) to hold arm in desired position (abduction, flexion, rotation) during case 4. **Non-operative side:** Tuck arm at side with padding **Blood pressure management:** Maintain **mean arterial pressure (MAP) greater than 70mmHg** during beach chair positioning to prevent cerebral hypoperfusion. Anesthesia should use **arterial line** for continuous BP monitoring and keep patient slightly hypertensive (systolic 120-140mmHg) during case. ### Lateral Decubitus Position (Alternative) **Advantages:** 1. **Better glenoid exposure** (gravity retracts humeral head posteriorly and inferiorly, easier glenoid visualization for reverse TSA) 2. **More stable** positioning (less movement during surgery, body secured in lateral position) 3. **No cerebral hypoperfusion risk** (head not elevated) **Disadvantages:** 1. **Conversion to anterior approach difficult** (would require repositioning patient) 2. **Anesthesia access** more limited (harder to reach airway, monitoring) 3. **Setup time longer** (more padding, stabilization needed) **Setup:** 1. **Patient position:** True lateral decubitus (operative side up) 2. **Stabilization:** Beanbag or lateral positioning supports (secure torso), kidney rest under contralateral chest 3. **Lower extremities:** Flexed at hips and knees, pillow between knees 4. **Operative arm:** Arm suspended in **traction tower** (10-15° abduction, neutral rotation) or arm holder 5. **Traction:** Some surgeons use **7-10 pounds of longitudinal traction** via traction tower to distract glenohumeral joint (improves glenoid exposure) ### Draping and Prep **Skin preparation:** Prep from **base of neck medially to mid-humerus distally**, and from **anterior axillary line to posterior scapula**. Circumferential prep allows arm manipulation during case. **Draping:** Use **extremity drape** (U-drape or split sheets) to create sterile field. The entire upper extremity should be free and mobile (draped into field). Some surgeons use **clear plastic drape** (Ioban) over skin for additional barrier and to secure drapes. ### Fluoroscopy Setup **Intraoperative fluoroscopy** (C-arm) is used for: 1. **Glenoid preparation** (check glenoid guide pin trajectory, ensure correct version) 2. **Baseplate positioning** (ensure inferior tilt of glenosphere, check screw placement) 3. **Humeral component positioning** (check version, height, offset) 4. **Final reduction check** (ensure glenohumeral articulation, no impingement) **C-arm positioning:** Mini C-arm or standard C-arm positioned to obtain **AP and axillary lateral views** of shoulder. For beach chair, C-arm comes from patient's head or contralateral side. For lateral position, C-arm comes from anterior or posterior. {/* SECTION 7: SURGICAL APPROACH */} ### Step 1: Skin Incision **Incision planning:** Mark the **posterolateral corner of the acromion** (palpable bony landmark). Extend incision **distally along posterior deltoid fibers** for 8-10cm (for reverse TSA) or 6-8cm (for rotator cuff repair). **Incision trajectory:** The incision follows the **posterior deltoid muscle fibers** (oriented obliquely from superolateral to inferomedial, roughly parallel to spine of scapula). This direction is parallel to Langer's lines and provides good cosmetic outcome. **Incise skin and subcutaneous tissue:** Use No. 10 blade scalpel. Deepen through subcutaneous tissue with electrocautery. Minimal subcutaneous fat posteriorly (compared to anterior shoulder). ### Step 2: Identify and Split Deltoid **Identify deltoid:** The deltoid muscle is immediately deep to subcutaneous tissue. Identify the interval between **posterior deltoid** and **middle deltoid** fibers. The interval is identified by: 1. **Palpating acromion** (deltoid origin on lateral acromion and scapular spine) 2. **Observing muscle fiber direction** (posterior deltoid runs obliquely inferior-medial, middle deltoid runs vertically inferior) 3. **Small fat stripe** sometimes visible between posterior and middle deltoid fibers **Mark 5cm distance:** Using a ruler or marking pen, mark **5cm distal to the lateral acromion** on the posterior deltoid muscle. **DO NOT SPLIT DELTOID BEYOND THIS MARK** (axillary nerve protection). **Split deltoid:** Use **blunt dissection** (finger, Mayo scissors spread technique, or Cobb elevator) to split the deltoid fibers in line with muscle fiber direction (parallel to posterior deltoid fibers). Start proximally at acromion origin and work distally to the 5cm mark. **Retract deltoid:** Place **self-retaining retractor** (Kolbel or Fukuda retractor) to retract the anterior and posterior flaps of split deltoid. The deltoid is retracted **anteriorly** (exposing posterior shoulder capsule) and **posteriorly** (providing access). ### Step 3: Identify Infraspinatus-Teres Minor Interval **Palpate spine of scapula:** With deltoid retracted, palpate the **spine of scapula** (bony ridge on posterior scapula). The **infraspinatus muscle** originates from the infraspinous fossa (below the spine), and **teres minor** originates from lateral scapular border (inferior to infraspinatus). **Identify the interval:** The interval between infraspinatus (superior) and teres minor (inferior) is visible as a **fat stripe** or **thin fascial line** between the two muscles. In some patients, the muscles are densely adherent and the interval is not obvious (requires blunt dissection to develop). **Develop the interval:** Use **finger dissection or Cobb elevator** to develop the interval between infraspinatus and teres minor. This is a **TRUE internervous plane** (suprascapular nerve vs axillary nerve), so it is safe to develop. Blunt dissection parallel to muscle fibers separates the muscles and exposes the underlying **posterior capsule**. **Retract muscles:** Place **Fukuda retractor** (or similar bent retractor) superior to infraspinatus (retracts infraspinatus superiorly) and inferior to teres minor (retracts teres minor inferiorly). The posterior glenohumeral joint capsule is now visible. ### Step 4: Capsulotomy and Joint Exposure **Palpate the joint:** Palpate the **posterior glenoid rim** and **humeral head** through the capsule. Rotate the arm (internal and external rotation) to confirm glenohumeral joint location. **Capsular incision:** Make a **vertical capsulotomy** parallel to the glenoid rim, **1-2cm lateral to the glenoid** (leaves a cuff of capsule on glenoid for later repair). Extend capsulotomy superiorly and inferiorly to provide adequate exposure. **Alternative - capsulectomy:** For arthroplasty, many surgeons perform **capsulectomy** (excise posterior capsule entirely) rather than capsulotomy. This improves exposure and is acceptable in elderly patients undergoing reverse TSA (capsular repair not critical for stability in reverse TSA). **Humeral head retraction:** Place **Fukuda humeral head retractor** (bent retractor) to displace humeral head **posteriorly and inferiorly** (out of glenoid socket). This exposes the **glenoid** for arthroplasty. Gentle retraction - excessive force can injure axillary nerve. **Inferior capsular release:** If exposure is inadequate, release the **inferior capsule** from the glenoid (improves humeral head translation). Can also release **conjoint tendon from coracoid** (if needed for extreme anterior exposure). ### Step 5: Glenoid Preparation (For Reverse TSA) **Expose glenoid:** With humeral head retracted, the entire glenoid surface should be visible. Remove any remaining labrum, osteophytes, or soft tissue from glenoid rim (using rongeur or arthroscopic shaver). **Reamers:** Use **glenoid reamers** (sequential sizes, spherical) to remove articular cartilage and subchondral bone down to bleeding cancellous bone. Goal is to create a **flat** glenoid surface perpendicular to scapular body (correct any version abnormalities). **Glenoid guide pin:** Place **central glenoid guide pin** (using guide jig) aimed toward the **base of coracoid** (anterior) and **medial border of scapula** (medial). Check pin position with **fluoroscopy** (AP and axillary views). The pin should be perpendicular to glenoid face in all planes. **Baseplate placement:** Ream over guide pin to create seating surface for glenoid baseplate (metaglene). Impact baseplate onto glenoid (central peg or keel seats in reamed bone). Secure baseplate with **peripheral screws** (typically 4 screws: superior, inferior, anterior, posterior). **Baseplate orientation:** The baseplate should have **10-15° inferior tilt** (inferiorly inclined, prevents scapular notching) and **neutral version** (0-5° retroversion). Check position with fluoroscopy. **Glenosphere:** Attach **glenosphere** (convex ball component) to baseplate via Morse taper or screw fixation (depends on implant design). Typical glenosphere sizes: 36mm, 38mm, or 40mm diameter. ### Step 6: Humeral Preparation (For Reverse TSA) **Humeral head osteotomy:** Perform **humeral head osteotomy** to remove articular surface. The cut is made at the **anatomic neck** (just above greater and lesser tuberosities). Orientation: **0-20° retroversion** (relative to forearm axis with elbow flexed 90°) and **135-145° inclination** (neck-shaft angle). **Humeral canal preparation:** Ream the **humeral canal** with sequential reamers (start small, increase size until good cortical contact). Typical final reamer size: 8-10mm. Some systems use broaches instead of reamers. **Humeral component (socket):** Insert **humeral stem** (press-fit or cemented, depending on bone quality). Elderly patients with osteoporotic bone often require **cement fixation**. Young patients with good bone can use press-fit (promotes bone ingrowth). **Humeral socket (liner):** Attach **humeral polyethylene socket** (concave liner) to the humeral stem. The socket articulates with the glenosphere (ball). Socket orientation: **0-20° retroversion** to match native retroversion. **Trial reduction:** Perform **trial reduction** with trial components before final implantation. Check for: 1. **Stability** (no dislocation with arm in all positions) 2. **Range of motion** (adequate elevation, rotation) 3. **Tension** (adequate soft tissue tension without over-tightening) 4. **Impingement** (no bone-on-bone contact in all ranges) If unstable or impingement: adjust humeral component version, height, or offset. Adjust glenosphere size if needed. ### Step 7: Final Implantation and Closure **Final components:** Remove trials and insert **final components** (glenosphere and humeral socket). Reduce shoulder (humeral socket onto glenosphere). **Check fluoroscopy:** Final AP and axillary images to confirm component position, reduction, no hardware issues. **Capsular repair (if capsulotomy performed):** Repair posterior capsule with **No. 2 Ethibond or FiberWire** (non-absorbable suture) using interrupted figure-of-eight sutures. Capsular repair is less critical in reverse TSA (relies on deltoid, not capsule) but may reduce instability risk. **Deltoid repair:** Repair the deltoid split with **interrupted No. 2 Ethibond or FiberWire sutures** (side-to-side mattress sutures). Strong repair (deltoid is the primary motor for reverse TSA - repair is critical). **Subcutaneous and skin closure:** Close subcutaneous layer with **2-0 Vicryl** and skin with **3-0 or 4-0 Monocryl subcuticular** or **skin staples**. **Dressing and immobilization:** Apply **sling immobilization** (shoulder immobilizer or abduction sling with pillow). Immobilization for **6 weeks** (protects deltoid and subscapularis repair, allows soft tissue healing). {/* SECTION 8: POSTOPERATIVE MANAGEMENT */} ### Immediate Postoperative (0-6 Weeks) **Immobilization:** **Sling immobilization for 6 weeks** (24/7 except for hygiene and exercises). The sling protects the deltoid repair and subscapularis (if repaired). Remove sling only for supervised physical therapy. **Pain management:** Multimodal analgesia: acetaminophen 1000mg every 6 hours, NSAIDs (celecoxib 200mg BID or ibuprofen 600mg TID), opioids (oxycodone 5-10mg every 4-6 hours PRN) for breakthrough pain. Many surgeons use **interscalene nerve block** (performed by anesthesia) for first 12-24 hours (excellent pain control, reduces opioid use). **Wound care:** Keep dressing dry for 48 hours. After 48 hours, patient can shower (let water run over incision, pat dry, no soaking in bath). Remove sutures or staples at 10-14 days. **Physical therapy (weeks 0-6):** **Passive range of motion ONLY** (therapist moves arm, patient relaxed). No active elevation or rotation (deltoid and subscapularis healing). Exercises: 1. **Pendulum exercises** (lean forward, let arm hang, gentle circular motions) 2. **Passive forward elevation** (supine, therapist lifts arm) 3. **Passive external rotation** (gentle, do NOT force - reverse TSA has limited external rotation) **NO active elevation, internal rotation, or lifting** during this phase. ### Early Rehabilitation (6-12 Weeks) **Wean from sling:** At 6 weeks, gradually wean from sling (start by removing sling for short periods during day, progress to sling at night only, then discontinue). **Active-assisted range of motion:** Begin **active-assisted exercises** (patient uses opposite arm or pulley to assist operative arm). Goals: 1. **Forward elevation** to 120-140° (reverse TSA typically achieves less elevation than anatomic TSA) 2. **External rotation** to 20-30° (limited by reverse TSA design - medialized center of rotation) 3. **Internal rotation** to buttock or lumbar spine **Strengthening:** Begin **isometric strengthening** (deltoid contraction without motion) at 8 weeks. **Light resistance exercises** (Theraband) at 10-12 weeks. ### Late Rehabilitation (12 Weeks - 6 Months) **Active range of motion:** Progress to **active range of motion** (patient lifts arm without assistance). Reverse TSA relies on **deltoid** (not rotator cuff) for motion - deltoid strengthening is critical. **Strengthening progression:** 1. **Deltoid strengthening** (forward elevation, abduction against resistance) 2. **Scapular stabilization** (rhomboid, serratus anterior exercises) 3. **Functional activities** (reaching overhead, behind back) **Activity goals:** 1. **Self-care** (dressing, grooming): 3 months 2. **Light household activities** (cooking, laundry): 3-4 months 3. **Driving**: 6-8 weeks (when comfortable and off opioids) 4. **Recreational activities** (golf, swimming): 6 months **Avoid:** Heavy lifting (greater than 5kg permanently), contact sports, repetitive overhead manual labor (risk of glenoid loosening, instability). ### Long-Term Outcomes and Complications **Expected outcomes:** - **Pain relief:** 90-95% significant improvement (VAS from 7-8 preop to 1-2 postop) - **Forward elevation:** Mean 120-140° (range 90-160°, depends on deltoid function and rehabilitation) - **External rotation:** Limited (mean 20-30°, reverse TSA has inherent ER deficit) - **Functional scores:** ASES (American Shoulder and Elbow Surgeons) score improves from 30-40 preop to 70-80 postop **Complications:** 1. **Instability/dislocation** (2-4%): Most common complication. Causes: component malposition, inadequate soft tissue tension, deltoid insufficiency. Management: closed reduction, immobilization; revision surgery if recurrent 2. **Infection** (1-2%): Cutibacterium acnes (formerly Propionibacterium) most common organism in shoulder. Management: irrigation and debridement, antibiotics (retain components if well-fixed and infection controlled; remove components if loose or persistent infection) 3. **Scapular notching** (20-40% radiographic, 5-10% symptomatic): Glenosphere impinges on inferior scapular neck with adduction. Caused by inadequate inferior tilt of baseplate. Mild notching (grade 1-2) is common and asymptomatic; severe notching (grade 3-4) can cause glenoid loosening 4. **Glenoid loosening** (2-5% at 5 years): Baseplate loosens from glenoid (lucency around screws, baseplate migration on X-ray). Risk factors: inadequate bone stock, scapular notching, younger age. Requires revision 5. **Periprosthetic fracture** (1-2%): Intraoperative (during impaction of press-fit stem) or postoperative (fall). Management: ORIF if displaced, observe if nondisplaced 6. **Axillary nerve injury** (3-5%): Deltoid paralysis (cannot abduct shoulder - reverse TSA will NOT function). Prevention: strict adherence to 5cm deltoid split rule 7. **Acromial fracture** (1-2%): Stress fracture of acromion from deltoid overload (reverse TSA increases deltoid force). Causes pain, click, ecchymosis over acromion. Management: observation (most heal), consider ORIF if displaced and symptomatic **Anatomy** (Burkhead et al, Clin Orthop 1992): - Axillary nerve exits quadrangular space **5-6cm inferior to lateral acromion** - Mean: 5.4cm, range 4.5-7cm - Bordered by: Teres minor (superior), teres major (inferior), long head triceps (medial), surgical neck humerus (lateral) **Rule**: **NEVER split deltoid more than 5cm distal to acromion** **Consequence of violation**: - Axillary nerve injury: 3-5% incidence - **DELTOID PARALYSIS** (cannot abduct shoulder - profound disability) - Reverse TSA will NOT function without deltoid (relies on deltoid for abduction) - Permanent functional impairment **Prevention strategies**: 1. **Mark 5cm distance** on skin before deltoid split (measure with ruler, mark with surgical marker) 2. **Use blunt dissection** in deltoid (fingers, blunt scissors) - NOT sharp dissection (scalpel, sharp scissors) 3. **If inadequate exposure** with 5cm split: - Extend incision PROXIMALLY (toward acromion) - OR use different approach (deltopectoral if needed) - **DO NOT** extend split distally beyond 5cm (nerve injury) **Exam pearl**: 5cm rule is ABSOLUTE - examiners will test this distance, violation = catastrophic complication **Correct baseplate position is CRITICAL for reverse TSA stability, function, and longevity** **1. INFERIOR TILT** (Simovitch et al, JBJS 2007): - **Target**: 10-15° inferior tilt - **Purpose**: Prevents scapular notching (glenosphere impingement on inferior scapular neck) - **Consequence of neutral/superior tilt**: - Notching in 50-70% of cases - Symptomatic loosening in 10-20% - Polyethylene wear - Component migration **2. VERSION**: - **Target**: 0-10° retroversion (match native glenoid version) - **Excessive anteversion** (>10°): Increases posterior instability risk - **Excessive retroversion** (>15°): Increases anterior instability risk - Check native glenoid version on preop CT (B2/B3 glenoids may have retroversion) **3. SCREW FIXATION**: - Use **4 peripheral screws** (superior, inferior, anterior, posterior) - Check with fluoroscopy: - Screws should be **IN bone** (not extraosseous - baseplate instability) - Screws should NOT penetrate glenohumeral joint (intra-articular screw = component failure) - Supplemental central compression screw (surgeon preference - some systems) **Exam pearl**: Inferior tilt 10-15° is KEY to preventing scapular notching - examiners will ask this parameter {/* SECTION 9: EVIDENCE */} {/* SECTION 10: VIVA SCENARIOS */} {/* SECTION 11: MNEMONICS */} {/* SECTION 12: EXAM CHEAT SHEET */}

Posterior Approach to Shoulder

Posterior Approach to Shoulder