UW Shoulder and Elbow Academy: Loose glenoid components, Propionibacterium, and their management

A lady in her 70s taking insulin for her diabetes with a high BMI who uses a wheelchair presented with pain in her shoulder after a prior arthroplasty. These x-rays were taken. Showing a well fixed humeral component and a loose polyethylene and metal glenoid.

She desired surgical revision with removal of her loose glenoid. She had no clinical or laboratory evidence of infection.

At surgery cloudy joint fluid was encountered and a frozen section showed > 5 WBC/HPF. The humeral component was well fixed. The loose glenoid was easily removed and the glenoid vault curetted to remove the reactive tissue. The wound was thoroughly irrigated and a new humeral head prosthesis with a larger diameter of curvature inserted. The well fixed ingrowth stem was not changed. She was started on Ceftriaxone and Vancomycin via a PICC line.

The gram stain and culture results were:

*Right shoulder humeral head explant
GS: Rare PMNs, no organisms seen
C: 1+ Propionibacterium

*Right shoulder glenoid explant
GS: 2+ PMNs, 3+GPCs and 2+GPRs on gram stain
C: 1+ Propionibacterium, Dermacoccus

*Right shoulder joint fluid #1

GS: 3+ PMNs,1+ GPCs
C: 1+ Propionibacterium type 1, 1+ Propionibacterium type 2

*Right shoulder joint fluid #2
GS: 3+ PMNs, no organisms seen
C: 1+ Propionibacterium type 1, 1+ Propionibacterium type 2

* Right shoulder glenoid membrane #1
GS: 1+ PMNs, no organisms seen
C: 1+ Propionibacterium type 1, 1+ Propionibacterium type 2

*Right shoulder glenoid membrane #2
GS: 1+ PMNs, no organisms seen
C: 1+ Propionibacterium type 1, 1+ Propionibacterium type 2, Coag neg staph (2 types)

*Right shoulder collar membrane
GS: 2+ PMNs, no organisms seen
C: 1+ Propionibacterium type 1, 1+ Propionibacterium type 2, 1+ Propionibacterium type 3

*Right shoulder capsule
GS: 2+ PMNs, no organisms seen
C: 1+ Propionibacterium type 1, 1+ Propionibacterium type 2, 1+ Propionibacterium type 3

She continues on supressive Augmentin with an improved, but imperfect shoulder.

Comment: Again it surprising how heavy a bacterial load existed in this shoulder without clinical manifestations of infection. We never know. In this case - in contrast to a prior one - we retained the humeral stem (rather than splitting the humerus to remove an ingrowth prosthesis) because of the patient's compromised health and dependency on the arm for transfers and ambulation, recognizing the risk of persistence of organisms.

This is, again, an argument against ingrowth or cemented humeral components: it is much safer to revise a humeral component fixed with impaction grafting.

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