Shoulder hemiarthroplasty

Shoulder hemiarthroplasty is a form of partial shoulder joint replacement for the management of pathologies concerning the proximal humerus.

History and etymology

The first shoulder arthroplasty was constructed by Péan in 1893. The current 3^rd generation arthroplasties have been introduced by Neer in the 1950s to the 1970s ¹.

Indications

Indications of shoulder hemiarthroplasty concern more advanced disease processes affecting the humeral side of the joint in younger individuals and include ^1-3:

• complex proximal humeral fractures

  • ≥2 fragments displaced >1 cm (>5 mm greater tuberosity) or angulated >45° 

• avascular necrosis (osteonecrosis) of the humeral head without affecting the glenoid

• osteoarthritis without glenoid involvement and/or poor glenoid bone stock

Additional factors favoring anatomic total shoulder arthroplasty over other forms of shoulder arthroplasty are ^1-4:

• intact rotator cuff with good tendon and muscle quality, in particular, the subscapularis tendon

• tuberosity fractures require reduction and fixation

Contraindications

Contraindications of shoulder hemiarthroplasty are ^1,4:

• high grade or full-thickness rotator cuff tears

• mucoid degeneration of the rotator cuff

• fracture morphology does not allow adequate tuberosity fixation

• patients not likely to adhere to physical therapy and functional rehabilitation

Prosthesis design

A shoulder hemiarthroplasty prosthesis does not have a glenoid component and consists of a stemmed metal humeral component with customizable head neck and stem parts ¹.

Procedure

A coarse overview of the surgical technique includes the following steps ⁵:

• reaming of the humeral shaft

• fitting of neck and cap components adjusting humeral head height and version

• securing tuberosity fixation and subscapularis integrity if necessary (e.g.in case of humeral fractures)

Complications

Complications of shoulder hemiarthroplasty include the following ⁴:

• rotator cuff failure

• fracture sequelae

• glenoid wear / glenoiditis

• component malposition

• overstuffing (shoulder arthroplasty)

• prosthetic implant loosening

• glenoid osteoarthritis

• periprosthetic fracture

• infection

Radiographic features

Plain radiograph

Anteroposterior and lateral views are the initial tests for procedural planning and mainstay in postoperative control and follow-up examinations.

Preprocedural radiographs can aid in the diagnosis and the assessment of the bone stock. Furthermore, radiographs acquired in the erect position can be evaluated for the following features indicating rotator cuff disease ¹:

• static proximal humeral head migration (acromiohumeral distance <7 mm in erect position)

• anterior humeral head subluxation

Post-operative radiographs should show the humeral stem centered within the humeral shaft and the head component centered within the glenoid ⁴.

Follow-up radiographs should be evaluated for signs of glenoid osteoarthritis including the following ⁴:

• joint space narrowing

• subchondral cyst formation

• posterior glenoid wear / glenoid erosions

US

Ultrasound can be used in the evaluation of the rotator cuff and the subscapularis muscle and tendon.

CT

CT is used for characterization for preoperative planning, in particular, the characterization of glenoid morphology and glenoid version measurements.

MRI

Like ultrasound can be used in the evaluation of the rotator cuff morphology and to exclude rotator cuff tears.

Radiological report

The radiological report should include a description of the following features ⁴:

Surgical planning:

• glenoid morphology

• glenoid version

• quality and integrity of the rotator cuff

Postoperative control and follow up:

• glenohumeral implant position/centering (centered/decentred)

• humeral neck-shaft angle

• tuberosity malunion/non-union

• implant loosening (radiolucencies Gruen zones)

• hardware failure

• signs of infection

Outcomes

Shoulder hemiarthroplasty offers an alternative to total shoulder arthroplasty in patients with deficient bone stock on the glenoid side and a treatment option in patients with comminuted proximal humeral fractures, in which adequate tuberosity fixation is feasible, preservation of the rotator cuff function can be accomplished and who adhere to subsequent physical therapy and functional rehabilitation.

Advantages

The main advantage of shoulder hemiarthroplasty over anatomical total shoulder arthroplasty is the preservation of glenoid bone stock.

Disadvantages

Disadvantages of shoulder hemiarthroplasty include the following ^1,4:

• poor functional outcome in the treatment of osteoarthritis and adequate bone stock

• the high failure rate in proximal humerus fractures with inadequate tuberosity fixation and/or rotator cuff disease or insufficient adherence of patients to subsequent physical therapy and functional rehabilitation

• requires meticulous surgical technique

See also

• shoulder arthroplasty (overview)