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Haematogenous PJI — SCE Infectious Diseases MCQ

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ModerateBone & Joint InfectionHaematogenous PJISCE Infectious Diseases

A 55-year-old man with a prosthetic knee joint develops an acute flare of knee pain 2 years after implantation. He had dental extraction 3 weeks ago without antibiotic prophylaxis. Blood cultures grow Streptococcus mutans. The knee is hot and swollen. What is the most likely route of infection?

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Correct answer: C — Haematogenous seeding of the prosthetic joint from transient bacteraemia during dental extraction

Late acute prosthetic joint infection (>3 months post-implantation with acute onset <3 weeks) is typically haematogenous — bacteraemia from a distant source seeds the prosthetic joint surface. Dental procedures cause transient Streptococcal bacteraemia. While antibiotic prophylaxis before dental procedures in prosthetic joint patients is debated (ADA/AAOS no longer routinely recommend it; UK practice varies), this case illustrates the mechanism. DAIR is appropriate for acute haematogenous PJI if the prosthesis is well-fixed and the organism is susceptible.

Reference: BSAC 2023 – PJI guidelines; NICE NG157 2024; ADA 2015 – Dental prophylaxis