Summary Reverse Shoulder Arthroplasty is a type of shoulder arthroplasty that uses a convex glenoid hemispheric ball and a concave humerus articulating cup to reconstruct the glenohumeral joint. The center of rotation is moved inferiorly and medialized which allows the deltoid muscle to act on a longer fulcrum and have more mechanical advantage. Reverse Shoulder Arthroplasty is indicated for conditions such as rotator cuff tear arthropathy, comminuted 4-part proximal humerus fractures and prior failed shoulder arthroplasty. Epidemiology Epidemiology popularized in Europe and now increasingly used in North America since 1990 Biomechanics The advantage of a reverse shoulder arthroplasty is that the center of rotation (COR) is moved inferiorly and medialized allows the deltoid muscle to act on a longer fulcrum and have more mechanical advantage to substitute for the deficient rotator cuff muscles to provide shoulder abduction allows increased (but not normal) shoulder abduction does not significantly help shoulder internal or external rotation Reverse shoulder arthroplasty can be combined with latissimus dorsi transfer to assist with external rotation Indications Clinical conditions cuff-tear arthropathy severe glenohumeral joint arthritis with superior escape in the setting of a massive rotator cuff tear pseudoparalysis an inability to actively elevate the arm in the presence of free passive ROM and in the absence of a neurologic lesion occurs secondary to irreparable rotator cuff tear in setting of glenohumeral arthritis antero-superior escape incompetent coracoacromial arch humeral "escape" in subcutaneous tissue with hemiarthroplasty proximal humerus fractures in the elderly 3 or 4-part fractures in patients age > 70 head-splitting fractures significant osteopenia or poor bone quality where GT has poor potential for healing rotator cuff insufficiency 'equivalent' non-union or mal-union of the tuberosity following trauma or prior arthroplasty failed arthroplasty in setting of prior HA or aTSA with cuff insufficiency when all other options have been exhausted rheumatoid arthritis only if glenoid bone stock is sufficient Patient characteristics (in clinical conditions above) low functional demand patients physiological age >70 sufficient glenoid bone stock working deltoid muscle intact axillary nerve Contraindications Axillary nerve dysfunction important to separate permanent from temporary Deltoid deficiency global deficiency is a contraindication partial deltoid deficiency is a relative contraindication but RSA may give reasonable results Acromion deficiency Glenoid osteoporosis Active infection Operative Planning Radiographs recommended views true AP (Grashey) determine extent of arthritis and look for superior migration of humerus axillary lateral look for posterior glenoid wear scapular-Y CT scan indications If unable to obtain an adequate axillary lateral, CT can be useful to determine glenoid version and glenoid bone stock estimate degree of osteopenia MRI indications evaluate rotator cuff integrity and fatty infiltration Approach Deltopectoral advantages: preserves deltoid muscle exposure of the lower pole of the glenoid to facilitate glenoid implant positioning can extend inferiorly for increase exposure to proximal humerus if needed can perform a simutlatenous latissimus dorsi transfer if needed decreased risk of axillary nerve palsy disadvantages need to take-down subscapularis for adequate exposure need for extensive capsular release which may lead to instability lack of exposure to posterior glenoid potential for stiffness given immobilization required for subscapularis healing Anterosuperior method the anterior deltoid is divided from the anterior edge of the acromioclavicular arch, allowing increased glenoid exposure. advantages increased glenoid exposure able to preserve subscapularis decreased post-operative instability due to preservation of anterior stabilizers ease of axial preparation of the humerus easier fixation of greater tuberosity for fractures disadvantages increased risk of injury to distal branches of axillary nerve violates anterior deltoid muscle risk of excess height or superior tilt of glenoid Techniques Humeral preparation humeral head typically osteotomized anywhere between 0 and 30 degrees of retroversion (typically 20) more retroversion is gaining popularity as it may improve post-op external rotation humeral head can be saved for autograft if needed osteotomy generally not needed in setting of fracture long head of biceps is tenotomized or tenodesed ream and broach humerus similar to conventional TSA the humeral height and version typically judged by humeral calcar or tuberosity fragment if calcar missing in the setting of fracture, height can be judged by pectoralis insertion which resides 5.6 cm from top of fractured humeral head Glenoid preparation labrum is excised and capsule is released circumferentially important to expose inferior glenoid by subperiosteally elevating tissue to ensure proper baseplate positioning accurate central guidewire placement is dictated by availability of the best bone stock for baseplate screw fixation place baseplate as inferiorly as possible with an inferior tilt shown to decrease implant loosening and scapular notching navigation systems increasingly used for accurate baseplate placement superior screw is generally aimed toward coracoid base and inferior screw aimed towards scapular body mount glenosphere onto baseplate size chosen based on patient size, motion and preservation of stability females/smaller pateints typically recieve a 36 mm and large men recieve a 40 mm. Tuberosity repair anatomic repair of the greater tuberosity is associated with improved shoulder external rotation, function and patient satisfaction compared to tuberosity resection or malunion Rehabilitiation Immediate patient placed in sling post-op Early rehab passive or active-assisted motion only during early rehab Sling discontinued at 3 weeks if subscapularis is NOT repaired, and 6 weeks if subscapularis is repaired limit passive ER or active IR during this time avoid pushing out of chair during acute rehab subscapularis re-tear would lead to anterior shoulder instability treatment early exploration and repair Complications Scapular notching incidence occurs in 44%-96% of grammont style prosthesis due to 155º humeral component neck-shaft angle that effectively medializes humeral component decreased incidence with lateralization of baseplate related to impingement by the medial rim of the humeral cup during adduction risk factors superiorly placed glenoid component superior tilt of glenoid component medialization of center of rotation high BMI Dislocation incidence reported rate between 2% - 3.4% position of dislocation most commonly extension, internal rotation, and adduction most common cause of early failure risk factors irreparable subscapularis (strongest risk) proximal humeral bone loss failed prior arthroplasty proximal humeral nonunion fixed pre-operative glenohumeral dislocation Glenoid Loosening incidence glenoid prosthetic loosening is most common mechanism of failure incidence significantly increases (~25% at 5-year followup) after revision RSA treatment treat using staged procedure to fill glenoid cavity with autogenous bone and await incorporation with a hemiarthroplasty prior to reimplantation of a new glenosphere Deep Infection incidence 1-2% risk of deep surgical cite infection following shoulder arthroplasty susceptible to infection due to large subacromial dead space created by reverse prosthesis most common organisms include c.acnes and staphylococci Risk Factors Younger age (less than 65) and male are the greatest risk factors Arthroplasty for traumatic reasons History of failed arthroplasty treatment 2-stage revision is considered gold standard most common antibiotic treatment of choice for c.acnes is vancomycin and clindamycin Acromial or scapular spine fractures incidence 4% after RSA risk factors female sex osteoporosis medialized preoperative center of rotation treatment conservative management leads to 40-50% union rate operative management with ORIF or tension band wiring of acromial fractures has increased union rates Levy Classification for Post-operative Acromial fractures after Reverse Shoulder Arthroplasty Type 1 Acromion anterior to posterolateral acromial corner Type 2 Mid acromion between base and posterolateral corner Type 3 Acromial base Neurapraxia of axillary nerve incidence 0.5-1% rate after RSA risk factors anterosuperior approach humerus lengthening treatment usually transient Sirveaux Classification of Scapular Notching Grade 1 Limited to scapular pillar Grade 2 In contact with inferior screw of baseplate Grade 3 Beyond the inferior screw Grade 4 Extends under baseplate approaching central peg Outcomes Overview results are dependent on indication, with cuff tear arthropathy (CTA) having the best results Radiographic radiographic results deteriorate after 6 years and clinical results after 8 years Survivability some cases series' have noted 10 year survivability is approximately 90% for implant retention Complications various studies have shown that complication rate amongst surgeons decrease after a surgeon has performed at least 18-45 cases