McPherson Staging (Periprosthetic Joint Infection)
Stages a periprosthetic joint infection by the McPherson system from its timing and the host and limb factors present.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Infection type
- Type III: late chronic, more than 4 weeks of symptoms
- Intravenous drug abuse
- Yes
- Synovial cutaneous fistula
- Yes
- Subcutaneous abscess greater than 8 square cm
- Yes
- Active infection present more than 3 to 4 months
- Yes
Result: McPherson stage III/C/3: late chronic infection in a significantly compromised host with a significantly compromised limb.
The tool opens with these values already filled in. Replace them with your own.
What you enter
- Infection type
- Age 80 years or older
- Alcoholism
- Chronic active dermatitis or cellulitis
- Chronic indwelling catheter
- Chronic malnutrition (albumin 3.0 g/dL or less)
- Current nicotine use (inhaled or oral)
- Diabetes needing an oral agent or insulin
The other 20 fields
- Hepatic insufficiency (cirrhosis)
- Immunosuppressive drugs (such as methotrexate, prednisone, cyclosporine)
- Malignancy, past or active
- Pulmonary insufficiency (room-air arterial blood gas oxygen less than 60%)
- Renal failure requiring dialysis
- Systemic inflammatory disease (such as rheumatoid arthritis or lupus)
- Systemic immune compromise from infection or disease (such as HIV or AIDS)
- Absolute neutrophil count less than 1000
- CD4 T-cell count less than 100
- Intravenous drug abuse
- Chronic active infection at another site
- Dysplasia or neoplasm of the immune system
- Active infection present more than 3 to 4 months
- Multiple incisions (creating skin bridges)
- Soft-tissue loss from prior trauma
- Subcutaneous abscess greater than 8 square cm
- Synovial cutaneous fistula
- Prior periarticular fracture or trauma about the joint (especially crush injury)
- Prior local irradiation to the wound area
- Vascular insufficiency to the extremity (absent pulses, chronic venous stasis disease, significant calcific arterial disease)
How this is calculated
Citation
McPherson EJ et al. Am J Orthop. 1999;28:161-165; Clin Orthop Relat Res. 2002;403:8-15. Coughlan A, Taylor F. Classifications in Brief: the McPherson classification of periprosthetic infection. Clin Orthop Relat Res. 2020;478(4):903-908. Read the sources: McPherson 1999 ↗, McPherson 2002 ↗, Coughlan 2020 ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.