Arthroplasty of the shoulder

indications

Indications

· rheumatoid arthritis

· osteoarthritis

· avascular necrosis

· massive rotator cuff tear

· cuff arthropathy

· locked dislocation with humeral head defect

Contraindications

· active or recent infection

· Charcot joint

· paralysis of both deltoid and rotator cuff

· severe loss of bone stock

Hemiarthroplasty

· indicated in acute 4-part fracture

· consider in younger patient with

· posttraumatic condition without glenoid involvement

· osteonecrosis

· rotator cuff arthropathy

Total arthroplasty

· better pain relief with

· osteoarthritis

· rheumatoid arthritis

· glenoid loosening higher with cuff arthropathy than osteoarthritis

technique

Design

· initially were constrained designs

· problems with high failure rates

· periarticular fractures

· glenoid loosening

· more recently

· unconstrained proximal humeral component

· with or without glenoid resurfacing

· characterised by

· near anatomic design

· intact or repairable rotator cuff to maintain stability and centre of joint rotation

· intact deltoid

· humeral component designed to

· preserve metaphyseal bone stock for adequate fixation

· maintain integrity of rotator cuff attachment

· glenoid component designed to

· preserve subchondral bone

· achieve fixation in glenoid metaphysis

· metal backing of glenoid may improve stress transfer

· all-polyethylene may transfer stress in more physiological manner

Planning

· AP x-rays in internal and external rotation

· to assess humeral head

· axillary view

· to assess glenoid

· posterior bone loss common in osteoarthritis

· medial bone loss common in rheumatoid arthritis

Procedure

Position

· beach-chair position

· Mayfield head rest

· patient to side of table so shoulder can be extended

· three assistants

· opposite

· to one side of surgeon (at head)

· to other side of surgeon (at waist)

Incision

· deltopectoral approach

· from origin to insertion of deltoid

· from clavicle above coracoid process

· over apex of axilla

· to proximal third of humerus

Approach

· separate deltoid and pectoralis major

· retract cephalic v medially with pectoralis major

· slip finger under conjoined tendon to palpate musculocutaneous nerve

· minimum 17 mm, average 31 mm

· upper 50% of tendinous insertion of pectoralis major divided

· slip finger down anterior surface of subscapularis to palpate axillary nerve

· finger passes under axillary nerve

· hook finger anteriorly and laterally to identify nerve

· identify and ligate anterior circumflex humeral artery and vein

· along inferior surface of subscapularis tendon

· divide subscapularis vertically right on insertion

· off lesser tuberosity

· dissect subscapularis off capsule

· release capsule from attachment on humerus

· begin superiorly

· extend anteriorly

· continue inferiorly to beyond 6 o’clock

· excise anteroinferior capsule

· extend and externally rotate humerus to dislocate and deliver head out of wound

Arthroplasty

· reduce head into joint

· place arm in 30-35^o of external rotation

· flex elbow and use forearm as protractor

· use less retroversion with

· recurrent posterior dislocation

· posterior glenoid bone loss

· use template or trial to mark angle of cut

· usually 130^o

· use oscillating saw to cut humeral head

· perpendicular to floor

· along marked line

· surprisingly small amount of bone removed

· prosthetic head should be above tuberosities

· deliver proximal humerus

· insert small stem, thin head (15 mm) trial

· ensure correct rotation before fins engage

· try medium stem and then large stem if indicated

· perform trial reduction to decide

· 15 mm (thin) or 22 mm* (thick) head

· use press-fit unless

· poor bone quality

· metaphyseal defects

· prepare glenoid if indicated

· use humeral head retractor to displace proximal humerus posteriorly

· use burr to make vertical slot in glenoid

· enlarge trough to accept keel of prosthesis

· flatten glenoid so that trial sits flat

· if severe glenoid bone deficiency, consider

· angled component

· bone graft

· cement glenoid in position

· insert stem

Closure

· reattach subscapularis to proximal humerus

· ensure there is 30-40^o external rotation

· close wound

Postoperative

· hospital

· passive flexion and external rotation

· pendulum exercises

· use of arm for gentle ADLs

· home

· continue exercises

· use normal arm, pulley and stick

· sling for 1-2 weeks

· start active resisted exercises at 6 weeks

results

· pain relief good (90%)

· range of motion variable

· osteoarthritis and intact rotator cuff - 120^o elevation

· post-trauma or massive rotator cuff tear - 40^o elevation

· survival comparable to other joints

· 10% revision rate at 10 yrs

Complications

· post-operative rotator cuff failure

· instability

· fracture of humerus

· infection

· neurovascular injury

· axillary nerve

· musculocutaneous nerve

· loosening

· glenoid lucent lines common but do not correlate with symptoms or need for revision surgery

· proximal migration of humeral head

· common

· not associated with symptoms or glenoid loosening

· not related to preoperative cuff integrity

· may be due to cuff thinning or tearing and imbalance