Shoulder arthroplasty

1. High-Yield Summary

Shoulder arthroplasty encompasses anatomic total shoulder arthroplasty (aTSA) and reverse total shoulder arthroplasty (rTSA). Successful joint reconstruction requires rigorous patient selection, accurate component positioning, balanced soft-tissue tensioning, and vigilant protection of adjacent neurovascular structures.

• Primary Clinical Indications: Anatomic total shoulder arthroplasty (aTSA) is indicated for concentric primary glenohumeral osteoarthritis with an intact, functional rotator cuff and adequate glenoid bone stock. Reverse total shoulder arthroplasty (rTSA) is indicated for rotator cuff tear arthropathy, massive irreparable posterosuperior rotator cuff tears with pseudoparalysis, complex proximal humeral fractures (3- and 4-part fracture-dislocations in older adults), severe glenoid retroversion or bone loss (Walch B2, B3, C, or Favard E3), and revision arthroplasty.
• Single Critical Move: In rTSA, placement of the metaglene/baseplate flush with or slightly overhanging the inferior glenoid rim with 0° to 10° of inferior tilt, preventing superior tilting and mechanical impingement. In aTSA, executing an anatomic humeral neck osteotomy matching native retroversion (20° to 30°) and inclination (130° to 135°) combined with a 360-degree capsular release to achieve concentric, low-friction glenohumeral articulation without eccentric loading.
• Catastrophic Errors to Avoid: Axillary nerve traction or laceration during inferior capsular release from the humeral neck; superior positioning or superior tilt of the rTSA baseplate, creating destructive shear vectors that cause early aseptic loosening and severe inferior scapular notching; uncontained eccentric glenoid reaming in aTSA violating the thin subchondral bone vault; and unrecognized Cutibacterium acnes periprosthetic infection presenting as low-grade indolent joint stiffness and premature component failure.

2. Indications

Clinical decision-making between aTSA, rTSA, and nonoperative management is governed by rotator cuff functional competence, glenoid bone morphology, patient physiologic age, and physical functional demands.

Explicit clinical, functional, and radiographic criteria include:

• Absolute Indications – aTSA: Severe, end-stage primary glenohumeral osteoarthritis (Kellgren-Lawrence grade IV) with a complete, fully functioning rotator cuff and concentric glenoid bone stock, refractory to a minimum of 3 to 6 months of comprehensive nonoperative management (physical therapy, activity modification, NSAIDs, and intra-articular injections) presenting with debilitating joint pain and loss of independent daily function.
• Absolute Indications – rTSA: Symptomatic cuff tear arthropathy (Seebauer stages IA, IB, IIA, IIB); massive irreparable posterosuperior rotator cuff tears accompanied by pseudoparalysis (active forward elevation <90° with preserved passive elevation and no primary neurologic deficit); advanced primary osteoarthritis with severe posterior or superior glenoid bone erosion (Walch B2, B3, C, or Favard E3) precluding stable anatomical glenoid component fixation; complex 3-part or 4-part proximal humeral fractures and fracture-dislocations in older adults (>65 to 70 years); and failed previous shoulder arthroplasty with secondary rotator cuff disruption or glenoid loosening.
• Relative Indications: Advanced humeral head osteonecrosis / avascular necrosis (Cruess stage IV to V; Ficat and Arlet stage III to IV) with secondary acetabularized or eroded glenoid cartilage; post-traumatic osteoarthritis with proximal humeral malunion; and systemic inflammatory arthritides (rheumatoid arthritis) with intact cuff (aTSA) or documented cuff erosion (rTSA).
• Absolute Contraindications: Active systemic sepsis or active local glenohumeral joint infection; complete axillary nerve paralysis or non-functional deltoid musculature (an absolute contraindication for rTSA, as active arm elevation relies entirely on deltoid recruitment); neuropathic arthropathy (Charcot shoulder); and severe medical comorbidities precluding major surgery under general anesthesia.
• Relative Contraindications: Irreparable anterior deltoid deficiency; severe noncompliance with postoperative immobilization and rehabilitation protocols; active intravenous substance abuse; and severe uncontained glenoid vault bone loss precluding baseplate fixation without extensive structural bone grafting.

3. Preoperative Planning

Preoperative templating and radiographic analysis establish bone stock, glenoid version, inclination, and soft-tissue contractures to prevent component malposition.

Imaging Review

Standard radiographic evaluation includes a complete three-view shoulder series and advanced three-dimensional imaging:

• True Anteroposterior (Grashey) View: Taken with the patient rotated 35° to 45° toward the affected side, placing the beam perpendicular to the scapular blade. Evaluates true glenohumeral joint space narrowing, subchondral sclerosis, and inferior humeral osteophytes (“goat’s beard”).
• Axillary Lateral View: Essential for determining static posterior humeral head subluxation, posterior glenoid wear, and anterior or posterior rim osteophytes.
• Scapular Y (Transscapular) View: Assesses acromial morphology, superior humeral migration (acromiohumeral interval <7 mm signifies chronic full-thickness tears), and anterior/posterior joint alignment.
• High-Resolution Thin-Cut CT (≤1 mm Slices): Mandatory from the superior acromion to the inferior scapular angle with 3D multiplanar reconstructions. Automated 3D planning software measures glenoid version (Friedman angle relative to the scapular blade axis) and glenoid inclination (Betts angle relative to the supraspinatus fossa floor). Pathologic retroversion >10° to 15° increases shear stresses at the glenoid bone-cement interface in aTSA, causing the “rocking horse” failure mode. Superior inclination >10° predisposes to early superior shear failure of rTSA baseplates.
• Glenoid Vault Depth and Bone Loss Assessment: Quantifies remaining subchondral bone and vault containment for central peg or central screw purchase, identifying the need for bone grafting or augmented baseplates.

Equipment Checklist

• Specialty Retractors: Fukuda humeral head and glenoid retractor, modified curved Darrach/humeral head retractors, Kolbel self-retaining retractor, Gelpi retractors, narrow and broad Bankart/pectoralis retractors, and a two-prong posterior glenoid retractor.
• Bone Preparation Instrumentation: Bone-preserving spherical glenoid reamers, stepped/half-wedge reamers for augmented glenoids, cannulated 0° and 10° inferior-tilt baseplate drill guides, cannulated drill bits, and low-profile humeral head cutting blocks.
• Implant Hardware & Fixation: Sized humeral broaches and stems (press-fit hydroxyapatite and cemented options), trial humeral heads and eccentric adapters, baseplate/metaglene trials (25 mm, 29 mm), glenospheres (36 mm, 38 mm, 40 mm, 42 mm with lateralized and eccentric offsets), peripheral locking and compression screws with dedicated screwdrivers.
• Sutures & Soft-Tissue Anchors: Heavy braided non-absorbable sutures (#2 and #5 FiberWire or Ethibond) for subscapularis peel or lesser tuberosity osteotomy transosseous fixation, tuberosity reconstruction, and biceps tenodesis.

Examination Under Anesthesia (EUA)

Immediately following general endotracheal anesthesia and prior to surgical preparation, perform a bilateral shoulder examination under anesthesia:

• Range of Motion Mapping: Document passive forward elevation in the scapular plane, external rotation at 0° abduction (arm at the side), external rotation at 90° abduction, and internal rotation behind the back.
• Capsular Contracture Identification: Passive external rotation <0° indicates severe anterior capsular and subscapularis shortening, requiring extensive anterior release. Restricted forward flexion and internal rotation indicate inferior and posterior capsular contractures.
• Dynamic Translation & Stability: Load-and-shift testing evaluates anterior, posterior, and inferior humeral head translation to distinguish flexible contractures from fixed, unyielding subluxation.

4. Patient Positioning & Setup

Precise patient positioning facilitates circumferential glenohumeral exposure while minimizing cervical spine stretch and hemodynamic compromise.

• Table Setup & Torso Orientation: The patient is positioned in a modified beach-chair position with the torso elevated between 30° and 45°. The medial border of the operative scapula must sit exactly at the lateral edge of the table, allowing the operative arm to extend, hyperextend, and adduct freely off the side of the table for unimpeded humeral canal reaming and broaching.
• Cervical Spine Protection: The head and cervical spine are secured in a specialized padded operative head positioner in neutral alignment (0° rotation, neutral flexion/extension). Avoid hyperextension or lateral flexion toward the contralateral side, which places the ipsilateral brachial plexus on stretch and increases risk of postoperative traction neuropraxia.
• Pressure Point Padding: Place a silicone axillary roll under the contralateral thorax to decompress the dependent brachial plexus. Pad the contralateral ulnar nerve at the cubital tunnel. Position gel pads beneath the knees and heels to prevent common peroneal nerve compression. Bilateral pneumatic sequential compression devices (SCDs) are placed on the calves.
• Sterile Draping & Limb Mobility: The entire upper extremity from the base of the neck, clavicle, and midline scapula to the hand is prepped and draped free using a sterile stockinette and cohesive wrap. An articulated mechanical limb positioner may be mounted to the operative table to hold the arm during glenoid preparation.

Safety Check

• Arm Extension Arc: Prior to surgical incision, verify that the operative arm can achieve 45° of hyperextension, 30° of adduction, and 90° of external rotation off the table without abutment against table rails or unsterile equipment.
• Fluoroscopy Corridors: When C-arm fluoroscopy is planned (e.g., verifying rTSA central screw trajectory or complex fracture reconstruction), confirm unobstructed AP and axillary radiographic corridors before sterile incision.
• Cerebral Perfusion Pressure: Coordinate with the anesthesia team to maintain mean arterial pressure (MAP) ≥65 to 70 mmHg (or monitor cerebral oximetry) throughout upright beach-chair positioning to eliminate watershed cerebral hypoperfusion events.

5. Approach

The deltopectoral approach is the gold-standard workhorse surgical approach for both anatomic and reverse shoulder arthroplasty, exploiting anatomical intermuscular and internervous planes.

• Named Surgical Approach: Deltopectoral approach.
• Superficial Internervous Plane: Formed between the deltoid muscle (innervated by the axillary nerve, C5–C6) and the pectoralis major muscle (innervated by the lateral and medial pectoral nerves, C5–T1).
• Deep Surgical Plane: Formed between the subscapularis muscle (innervated by the upper and lower subscapular nerves, C5–C6) and the conjoined tendon / coracobrachialis (innervated by the musculocutaneous nerve, C5–C7).
• Skin Incision & Deltopectoral Interval: Make a 10 to 12 cm linear incision beginning at the mid-clavicle, crossing just lateral to the coracoid process, and extending distally along the anterior deltoid border toward the deltoid tuberosity. Deepen the dissection through subcutaneous tissue. Identify the deltopectoral interval, marked by a distinct yellow fat stripe surrounding the cephalic vein.
• Cephalic Vein Mobilization: Meticulously mobilize the cephalic vein and retract it laterally with the deltoid muscle. Retracting laterally preserves the large tributary veins draining the deltoid muscle, preventing venous hemorrhage and reducing postoperative anterior shoulder edema.
• Conjoined Tendon Retraction & Musculocutaneous Nerve Safety: Incise the clavipectoral fascia along the lateral border of the conjoined tendon from the coracoacromial ligament down to the superior border of the pectoralis major tendon. Gently retract the conjoined tendon medially using a smooth retractor. The musculocutaneous nerve enters the posterior surface of the conjoined tendon 3 to 8 cm (mean 5 cm) distal to the coracoid tip. To avoid traction neuropraxia, never place aggressive self-retaining retractors beneath the conjoined tendon, and keep the arm in slight forward flexion and adduction during medial retraction.
• Anatomic Landmark (“Three Sisters”): Identify the anterior humeral circumflex artery and its two venae comitantes (“Three Sisters”) running transversely across the inferior muscular border of the subscapularis tendon. Meticulously coagulate with bipolar electrocautery or ligate these vessels. Ligation marks the safe inferior border of the subscapularis and prevents vessel retraction into the axilla with subsequent deep hematoma formation.

6. Technique

The procedural sequence requires systematic soft-tissue release, accurate osseous cuts, conservative bone preservation, and stable component fixation.

Step 1: Exposure and Soft-Tissue Mobilization

• Tenotomy / Tenodesis of the Long Head of the Biceps (LHB): Identify the bicipital groove. Transect the LHB tendon sharply at its supraglenoid tubercle origin. Tag the distal stump for subpectoral tenodesis to the superior margin of the pectoralis major tendon insertion, or perform tenotomy in low-demand patients. Biceps release clears visualization of the superior glenoid rim and eliminates a primary anterior pain generator.
• Subscapularis Mobilization in aTSA: Manage the subscapularis using one of three validated methods: (1) Subscapularis Peel: Sharply elevate the subscapularis tendon and underlying anterior capsule directly off their lesser tuberosity footprint using electrocautery, maintaining continuous periosteal sleeves for transosseous repair. (2) Lesser Tuberosity Osteotomy (LTO): Use an osteotome or saw to excise a 2 to 3 mm thick wafer of bone containing the entire lesser tuberosity and subscapularis insertion, enabling bone-to-bone healing. (3) Subscapularis Tenotomy: Incise the tendon vertically 1 cm medial to the bicipital groove, leaving a lateral cuff for subsequent end-to-end suture repair. In all methods, tag the subscapularis tendon with 3 or 4 heavy (#2 or #5) braided non-absorbable stay sutures for subsequent mobilization and anatomical repair.
• Subscapularis Management in rTSA: In rTSA, subscapularis management depends on prosthesis lateralization; with medialized designs, repair is prioritized to prevent anterior instability, whereas with lateralized designs, subscapularis repair is optional if soft tissues are contracted, avoiding restriction of external rotation.
• 360-Degree Capsular Release: With the arm externally rotated and slightly abducted, perform a circumferential capsular release. Release the anterior capsule from the glenoid rim. Carry the capsular release inferiorly directly along the humeral neck down to the 6 o’clock position. Protect the axillary nerve (which courses 3 to 5 mm inferior to the joint capsule) by placing a blunt Darrach or narrow Hohmann retractor inside the capsule directly against bone during release.

Step 2: Bone Preparation / Debridement

• Humeral Osteotomy in aTSA: Deliver the proximal humerus into the surgical field by extending, adducting, and externally rotating the arm. Resect peripheral humeral head osteophytes, particularly the inferior osteophyte (“goat’s beard”), to expose the true anatomical neck. Replicate native patient anatomy using an intramedullary or extramedullary cutting guide set to 20° to 30° retroversion (referencing the forearm axis) and 130° to 135° neck-shaft inclination. Cut precisely along the anatomical neck.
• Humeral Osteotomy in rTSA: Execute the humeral cut based on implant geometry (135°, 145°, or 155° inclination) and 20° to 30° retroversion. Ensure the cut does not remove excessive metaphyseal bone, which would compromise press-fit stability.
• Humeral Canal Preparation: Sequentially broach the humeral canal along the longitudinal diaphyseal axis. Increase broach sizes until rotational and axial cortical stability is achieved. Place a protective humeral cut-surface plate over the broach to protect host bone during subsequent glenoid exposure.
• Glenoid Exposure & Debridement: Place a Fukuda retractor deep to the posterior humeral neck, retracting the humerus posteriorly. Place a sharp two-prong retractor on the posterior glenoid rim, an anterior retractor medially retracting the subscapularis and conjoined tendon, and a superior retractor beneath the acromion. Excise the glenoid labrum circumferentially (360°). Release the posterior and inferior capsule from the glenoid rim to allow full delivery of the glenoid face.
• Glenoid Reaming in aTSA: Place a central guide pin perpendicular to the glenoid face. Conservatively ream the glenoid surface to create a spherical bleeding bone bed matching the component curvature. Avoid excessive asymmetric reaming (>10° correction) in retroverted Walch B2 glenoids to prevent penetrating the subchondral bone vault. Drill peripheral peg holes or prepare the central keel slot using a cannulated drill guide.
• Glenoid Reaming in rTSA: Insert the cannulated baseplate guide pin at the inferior third of the glenoid face, aiming for 0° to 10° of inferior tilt and neutral version relative to the scapular blade. Ream the glenoid conservatively until the inferior cortical bone rim is exposed. The baseplate must be positioned flush with or with a 1 to 2 mm inferior overhang beyond the inferior glenoid margin to eliminate superior tilt and prevent inferior scapular notching.

Step 3: Trialing and Provisional Fixation

• Trial Component Seating: Insert the trial glenoid component (aTSA trial polyethylene glenoid or rTSA metaglene with trial glenosphere). Verify circumferential seating against host subchondral bone and confirm absent toggle, liftoff, or rocking.
• Humeral Trialing & Joint Reduction: Assemble the trial humeral stem, trial neck adapter, and trial humeral head (aTSA) or trial polyethylene liner/spacer (rTSA). Reduce the joint with gentle traction, forward flexion, and internal rotation.
• Stability & Tension Assessment in aTSA: Check anterior and posterior translation: the humeral head should translate 50% across the glenoid rim and spontaneously recenter upon release. Passive external rotation should achieve ≥30° to 40° without tension on the subscapularis repair. Full adduction and forward elevation should proceed without bony impingement.
• Stability & Tension Assessment in rTSA: Perform the “shuck test”: apply longitudinal axial traction on the extended arm. Translation should demonstrate 1 to 2 mm of joint distraction, confirming optimal deltoid tension. Palpate the anterior and lateral deltoid muscle bands to confirm firm, resilient tension. Confirm stable range of motion without posterior or anterior impingement in full adduction, extension, and external rotation.

Step 4: Final Implant Placement or Suture Fixation

• Definitive Glenoid Fixation – aTSA: Thoroughly pulsatile-lavage and dry the glenoid vault. Pack the drill holes with dry sponge packing. Inject pressurized polymethylmethacrylate (PMMA) bone cement in a low-viscosity doughy state using a pressurization syringe. Insert the highly cross-linked polyethylene pegged or keeled glenoid component. Maintain continuous manual pressurization with a glenoid pusher until PMMA polymerization is complete.
• Definitive Glenoid Fixation – rTSA: Impact the definitive porous-coated titanium metaglene/baseplate flush with the inferior glenoid rim. Secure the central post or lag screw. Place peripheral locking and compression screws: aim the superior screw into the base of the coracoid process (providing dense cortical purchase) and the inferior screw into the thick scapular pillar. Impact the definitive cobalt-chrome glenosphere onto the baseplate taper and engage the central locking safety screw to manufacturer torque specifications.
• Definitive Humeral Stem Implantation: For press-fit stems, impact the definitive hydroxyapatite-coated prosthesis into the prepared canal. For cemented stems, insert a distal canal cement restrictor, pulsatile-lavage and dry the canal, retrograde-inject PMMA cement using a cement gun, pressurize the cement mantle, and introduce the polished humeral stem in 20° to 30° of retroversion. Mount and engage the definitive modular humeral head (aTSA) or humeral polyethylene liner (rTSA).
• Subscapularis Reconstruction: In aTSA, perform an anatomical transosseous repair of the subscapularis peel or LTO using #5 braided non-absorbable sutures passed through drill holes placed in the bicipital groove and lesser tuberosity. Tie sutures securely with the arm in 20° to 30° of external rotation to prevent overtightening. In rTSA with lateralized designs, repair the subscapularis if mobility allows without restricting external rotation.
• Wound Closure: Irrigate the joint copiously with normal saline. Perform layered closure: close the clavipectoral fascia, re-approximate the deltopectoral interval over a deep closed-suction drain (optional), and close subcutaneous tissues and subcuticular skin.

Critical Move

The irreversible procedural step (“point of no return”) differs between configurations:

• In Reverse TSA: The single most critical move is positioning the glenoid baseplate flush to or slightly overhanging (1 to 2 mm) the inferior glenoid margin with 0° to 10° of inferior tilt. Superior baseplate placement or superior inclination alters joint contact mechanics, converting stabilizing compressive joint reaction forces into destructive upward shear vectors during active deltoid contraction. This guarantees early aseptic glenoid loosening, premature baseplate failure, and severe inferior scapular notching.
• In Anatomic TSA: The critical move is avoiding aggressive asymmetric posterior glenoid reaming (>10° correction) in retroverted Walch B2 glenoids. Over-reaming breaches the thin cortical bone of the posterior glenoid vault, leaving inadequate osseous containment for component pegs and medializing the joint line. Medialization slackens the rotator cuff moment arm, inducing persistent anterior-posterior instability and early “rocking horse” glenoid loosening.

7. Pearls and Pitfalls

Adherence to reproducible intraoperative pearls protects neurovascular structures and ensures durable biomechanical outcomes.

Pearls

• 360-Degree Capsular Release for Humeral Delivery: Rather than prying against the posterior glenoid rim with a retractor, systematically release the anterior, inferior, and posterior capsule from the anatomical neck. The proximal humerus will effortlessly dislocate anteriorly without forceful manipulation.
• Digital Axillary Nerve Palpation: Introduce the index finger through the deltopectoral interval along the anterior belly of the subscapularis muscle, curling beneath the inferior humeral neck. Palpate the axillary nerve as a cord-like structure; keeping a blunt retractor between the nerve and capsule protects it during release.
• Pre-Placing Transosseous Subscapularis Sutures: Drill transosseous drill holes through the bicipital groove and lesser tuberosity before final humeral stem cementation or impaction. Pre-threading heavy #5 non-absorbable sutures prevents struggle with suture passers in a crowded joint space.
• Lateralization Nuance in rTSA: Using a lateralized glenosphere (2 to 4 mm metallic lateralization) or a bony increased-offset autograft (BIO-RSA) tensions the residual infraspinatus and teres minor, restoring functional active external rotation and dramatically reducing scapular notching.

Pitfalls

• Musculocutaneous Nerve Traction Neuropraxia: Forceful medial retraction of the conjoined tendon with the arm extended can stretch the musculocutaneous nerve. Rescue maneuver: Immediately release medial retraction, reposition the arm in forward flexion and adduction, and check for nerve relaxation.
• Superior Tilt of the rTSA Baseplate: Inserting the central guide pin perpendicular to a superiorly worn glenoid face creates superior tilt. Rescue maneuver: Fully debride the inferior glenoid rim to expose the true 6 o’clock margin, and use a guide with 10° inferior inclination or perform eccentric inferior reaming.
• Subchondral Vault Perforation in aTSA: Over-reaming the posterior glenoid wall breaches the vaulted shell. Rescue maneuver: Stop reaming immediately, palpate the vault wall with a blunt probe, and switch to an augmented stepped glenoid or convert to rTSA.
• Missed Cutibacterium acnes Colonization: Discarding cultures after 5 days leads to false-negative results in low-grade infections. Rescue maneuver: Maintain all deep surgical specimens in anaerobic culture broth for a full 14 days and treat suspicious loosening with targeted antimicrobial regimens.

8. Postoperative Care

Postoperative care balances early passive motion to prevent capsuloligamentous contracture with protection of soft-tissue repairs and implant osseointegration.

Immediate

• Joint Immobilization: Place the operative limb in a padded abduction sling maintaining 15° of abduction and neutral rotation. In aTSA, the sling protects the healing subscapularis repair; in rTSA, it prevents adduction-extension-internal rotation positions that risk posterior dislocation.
• Neurovascular Surveillance: Perform serial neurovascular assessments every 4 hours, focusing on axillary nerve sensory distribution over the lateral deltoid (“sergeant’s patch”) and deltoid isometric tone, as well as radial, median, and ulnar motor and sensory function.
• Multimodal Analgesia: Maintain regional anesthesia via single-shot or continuous interscalene brachial plexus nerve block combined with scheduled oral acetaminophen, NSAIDs (unless contraindicated), and short-acting breakthrough opioids.
• Venous Thromboembolism (VTE) Chemoprophylaxis: Apply mechanical pneumatic compression devices immediately postoperatively. Administer aspirin 81 mg orally twice daily for 4 weeks in standard-risk patients, or low-molecular-weight heparin / direct oral anticoagulants in high-risk patients.

Rehabilitation Protocol

Rehabilitation follows a staged protocol tailored to the biomechanical demands of anatomic versus reverse reconstruction:

9. Outcome

Shoulder arthroplasty provides durable pain relief, functional restoration, and reliable long-term implant survivorship when components are positioned accurately.

• Validated Functional Outcome Scores: American Shoulder and Elbow Surgeons (ASES) scores improve from a preoperative baseline of 30 to 35 points to postoperative scores of 85 to 92 points for both aTSA and rTSA at 2- to 5-year follow-up. Constant-Murley scores increase from a mean of 25 to 30 points preoperatively to 75 to 85 points postoperatively. Simple Shoulder Test (SST) affirmative responses increase from an average of 2 to 3 preoperatively to 10 to 11 at final follow-up.
• Pain Relief (VAS): Visual Analog Scale pain scores demonstrate dramatic improvement, falling from 7 to 9/10 preoperatively to ≤1.0 to 1.5/10 postoperatively, with >90% to 95% of patients reporting satisfactory pain relief.
• Anatomic TSA Motion Gains: Mean active forward elevation improves from 85° to 95° preoperatively to 145° to 160° postoperatively. Active external rotation at the side increases from 10° to 15° to 45° to 55°.
• Reverse TSA Motion Gains: Mean active forward elevation improves from 60° to 80° preoperatively to 130° to 145° postoperatively. Active external rotation recovery depends heavily on teres minor integrity and prosthesis lateralization, typically averaging 20° to 35° with modern lateralized designs.
• Anatomic TSA Long-Term Survivorship: Overall implant survivorship free of revision is 92% to 95% at 10 years and 80% to 85% at 15 to 20 years. Polyethylene glenoid component aseptic loosening represents the predominant late failure mode, driven by eccentric loading and subchondral cement debonding.
• Reverse TSA Long-Term Survivorship: Mid- to long-term survivorship free of revision is 90% to 93% at 10 years. Failure modes in modern cohorts are primarily driven by periprosthetic joint infection, late periprosthetic fractures, and glenoid baseplate loosening.

10. Complications

Shoulder arthroplasty complications encompass infection, mechanical component loosening, soft-tissue failure, neurologic injury, and periprosthetic fractures.

Specific Complication Nuances

• Periprosthetic Joint Infection & Cutibacterium acnes: C. acnes is a slow-growing, aerotolerant anaerobic Gram-positive bacillus that preferentially colonizes the deep sebaceous glands and hair follicles of the axilla and shoulder girdle. Because it produces an indolent, low-grade inflammatory response, standard laboratory markers (ESR, CRP, white blood cell count) are normal in up to 50% of confirmed cases. A minimum of 5 distinct deep intraoperative tissue biopsies must be harvested and incubated in anaerobic cultures for 14 to 21 days. Treatment options include radical debridement, single-stage exchange, or two-stage revision with an articulating antibiotic spacer.
• Scapular Notching Classification (Sirveaux): Mechanical contact of the medial humeral cup against the inferior scapular pillar during arm adduction produces progressive osteolysis. Grade 1: Defect confined to the inferior scapular pillar cortex. Grade 2: Osteolytic notch reaches the inferior peripheral locking screw. Grade 3: Osteolysis extends beyond the inferior screw into the central peg/post. Grade 4: Severe osteolysis extending beneath the entire baseplate, compromising baseplate stability. Modern lateralized implants and inferior baseplate positioning with 1 to 2 mm overhang eliminate or significantly reduce high-grade notching.
• Periprosthetic Humeral Fractures (Wright & Cofield Classification): Type A fractures occur around the tip of the stem extending proximally into the diaphysis, requiring revision to a long-stem prosthesis bypassing the fracture by at least two cortical diameters, supplemented with cerclage cabling. Type B fractures surround the body of the humeral stem; stable implants can be treated with cerclage cables or locking plates, whereas loose implants require long-stem revision arthroplasty. Type C fractures occur completely distal to the tip of the stem and are treated according to standard humeral shaft fracture principles using open reduction and internal fixation with a locking plate, or conservative functional bracing if non-displaced.

11. Evidence-Based Synthesis

Modern clinical decision-making is grounded in high-quality randomized controlled trials and prospective registry analyses, corroborated by seminal biomechanical and anatomical descriptions.

12. References

• Bullock GS, Garrigues GE, Ledbetter L et al. A Systematic Review of Proposed Rehabilitation Guidelines Following Anatomic and Reverse Shoulder Arthroplasty. J Orthop Sports Phys Ther. 2019. doi:10.2519/jospt.2019.8616 [Level I: Systematic Review / Meta-Analysis]
• Liu EY, Kord D, Horner NS et al. Stemless anatomic total shoulder arthroplasty: a systematic review and meta-analysis. J Shoulder Elbow Surg. 2020. doi:10.1016/j.jse.2019.12.022 [Level I: Systematic Review / Meta-Analysis]
• Del Core MA, Cutler HS, Ahn J et al. Systematic review and network meta-analysis of subscapularis management techniques in anatomic total shoulder arthroplasty. J Shoulder Elbow Surg. 2021. doi:10.1016/j.jse.2020.09.027 [Level I: Systematic Review / Meta-Analysis]
• Hawi N, Tauber M, Messina MJ et al. Anatomic stemless shoulder arthroplasty and related outcomes: a systematic review. BMC Musculoskelet Disord. 2016. doi:10.1186/s12891-016-1235-0 [Level I: Systematic Review / Meta-Analysis]
• Puzzitiello RN, Nwachukwu BU, Agarwalla A et al. Patient Satisfaction After Total Shoulder Arthroplasty. Orthopedics. 2020. doi:10.3928/01477447-20200812-03 [Level I: Systematic Review / Meta-Analysis]

13. Master Class Pro-Tip

During glenoid exposure in difficult cases with severe posterior wear or stiff contractures, resist the temptation to aggressively retract the proximal humerus with posterior levering against the glenoid rim. Instead, perform a complete 360-degree capsular release down to the 6 o’clock position directly on bone, meticulously protecting the axillary nerve with an intra-articular blunt Hohmann or Darrach retractor. For reverse arthroplasty, the single most critical technical determinant of longevity is placing the baseplate flush with or slightly inferior to the inferior glenoid rim with 0 to 10 degrees of inferior tilt. Any superior placement or inclination converts stabilizing compressive forces into destabilizing upward shear vectors, guaranteeing early aseptic loosening and severe scapular notching.

Master Class Surgical Pearl: Shoulder Arthroplasty Exposure & Baseplate Placement