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Infection is one of the most devastating complications of shoulder arthroplasty. The incidence of infection has been recently reported at 1.86% for primary and 4% for revision prostheses.10
Risk factors for infection include oral steroid use, history of malignancy, diabetes mellitus, distant osteomyelitis, infected prostheses at other sites, and history of septic arthritis in the affected shoulder.11
There is a clinical tendency towards misdiagnosis or delay diagnosis of chronic infection. Infected shoulder prostheses are less disabling than an infected hip or knee prosthesis due to lack of weight-bearing status. As well, many patients with an infected shoulder prosthesis complain of stiffness or pain, without clinical signs of infection.10 Similar clinical findings may also be seen in aseptic loosening.
In a series of 30 patients with infected shoulder arthroplasties, Sperling and Kozak11 reported clinical symptoms of:
- Pain 100%
- Stiffness 40%
- Fever 23%
- Night sweats 10%
- Chills 10%
Clinical signs included:
- Draining sinus 50%
- Erythema 40%
- Effusion 28%
Radiographic features of infection included:
- Progressive and extensive widening of interfaces between bone-cement, bone-prosthesis or cement-prosthesis
- Periosteal reaction
- Documentation of a sinus track during arthrography is diagnostic for infection
Acute infections are diagnosed when symptoms occur after a recent recognizable event (i.e. dental surgery) that results in transient bacteremia and seeding of the joint. This is usually managed with open surgical lavage.
Subacute or chronic infections are more common. This is managed with removal of the prosthesis and debridement and lavage of surrounding tissues. The limb may be flail or an antibiotic-impregnated cement spacer may be placed. Revision arthroplasty is performed after adequate intravenous antibiotic therapy.
Chronically infected shoulder hemiarthroplasty resulting in marked widening of bone-cement interfaces, thinning of cortical bone and subsequent pathologic fracture.
Fluoroscopic-guided joint aspiration/arthrography can be performed to obtain cultures. Positive cultures are useful in clinically suspected infection, however there is a high rate of false positive and false negative cultures in patients with joint replacements. Therefore, results must be considered in the appropriate clinical setting.12
Chronically infected shoulder hemiarthroplasty: digitally subtracted arthrogram demonstrates sinus track. EKG lead was used as a marker, placed just inferior to drainage.
Cement spacers are temporary prostheses made of antibiotic-impregnated methylmethacralate. The cement is prepared in the surgical site, mixed with antibiotics, and formed by the surgeon into a patty, cylinder or forms resembling the humeral components of the shoulder arthroplasty. The spacer allows for local dispersal of antibiotics to the infected joint area. Cement spacers have certain advantages because they:
- Provide local dispersal of antibiotics to the infected joint area
- Maintain arm length
- Minimize dead space
- Preserve soft-tissue planes
- Facilitate ease of revision arthroplasty
Right shoulder cement spacer in place in a patient with an infected total hip replacement which seeded both of her native shoulder joints. Both shoulders required debridement and cement spacer placement.