Shoulder Hemiarthroplasty - Shoulder & Elbow

Introduction

Humeral articular surface replaced with stemmed humeral component coupled with either
- standard humeral head
- extended-coverage head

Indications

Indications
- primary arthritis, if:
  - rotator cuff is deficient
  - glenoid bone stock is inadequate
  - risk of glenoid loosening is high
    - young patients
    - active laborers
- rotator cuff arthropathy
  - hemiarthroplasty > rTSA if able to achieve forward flexion > 90 degrees
- osteonecrosis without glenoid involvement
- proximal humerus fractures
  - three-part fractures with poor bone quality
  - four-part fractures
  - head-splitting fractures
  - fracture with significant destruction of the articular surface
Contraindications
- infection
- neuropathic joint
- unmotivated patient
- coracoacromial ligament deficiency
  - provides a barrier to humeral head proximal migration in the case of a rotator cuff tear
  - superior escape will occur if coracoacromial ligament and rotator cuff are deficient

Outcomes

Rotator cuff deficiency
- status of the rotator cuff is the most influential factor affecting postoperative function in shoulder hemiarthroplasty
Proximal humerus fractures
- provides excellent pain relief in a majority of patients
- outcome scores inversely proportional to
  - patient age
  - time from injury to operation

Preoperative Imaging

Radiographs
- true (Grashey) AP of shoulder
  - taken 30-40 degrees oblique to the coronal plane of the body
  - findings
    - helps determine extent of DJD
    - delineation of fracture pattern
- axillary view
  - findings
    - look for posterior wear of glenoid
    - helps quantify displacement in cases of fracture
CT scan
- obtain CT scan to determine glenoid version and glenoid bone stock
- useful if fracture pattern is poorly understood after radiographic evaluation
MRI
- useful for evaluation of rotator cuff

Surgical Techniques

Approach
- deltopectoral approach
Shaft preparation and prosthesis placement
- humeral head resection
  - start osteotomy at medial insertion line of supraspinatus
- determine retroversion, implant height and head size
  - retroversion
    - 30° of retroversion is ideal
    - lateral fin should be slightly posterior to biceps groove
    - excessive anteversion leads to risk of anterior dislocation
    - excessive retroversion leads to risk of posterior dislocation
  - implant height
    - greater tuberosity should be
      - 5 to 8 mm below the top of the prosthetic humeral head
        
        functions to
        
        maintain cuff and biceps tension
        
        recreate normal contour of medial calcar
        
        technique to achieve
        
        cement prosthesis proud
        
        distance from top of prosthesis head to upper border of pectoralis major should be 56mm.
  - head size
    - determine size by using
      - radiograph of contralateral shoulder or
      - measuring size of native head removed earlier in procedure
      - using too large of a head may "overstuff" joint
Fixation
- cemented prosthesis
  - standard of care
  - provides better quality of life, range of motion, and strength compared to uncemented humeral component
Tuberosity reduction
- introduction
  - tuberosity migration is one of the most common causes of failure for fractures treated with hemiarthroplasty
- technique
  - strict attention to securing the tuberosities to each other and to the shaft
  - autogenous bone grafting from the excised humeral head will decrease the incidence of pull-off and improve healing rates
  - tuberosity reduction must be anatomic or it may lead to a deficit in rotation

Rehab

Early passive motion until fracture has healed
- duration usually 6-8 weeks
Strengthening exercises begin once tuberosity has fully healed

Complications

Progressive glenoid arthrosis
- increased risk with
  - young patients
  - active patient
- treatment
  - conversion to total shoulder arthroplasty
Tuberosity displacement/malunion
- one of the most common complications of shoulder hemiarthroplasty when used to treat fracture
- treatment
  - repositioning of the tuberosity with bone grafting
Joint overstuffing
- may lead to
  - stiffness
  - accelerated arthritis of glenoid
Subcutaneous (anterosuperior) escape
- occurs when both rotator cuff and coracoacromial arch are deficient
- better outcomes with conversion to reverse shoulder arthroplasty compared to anatomic TSA