Is aseptic loosening truly aseptic?

Area of Science:

• Orthopaedic Surgery
• Infectious Diseases
• Biomaterials Science

Background:

• Microorganisms can persist on and within orthopaedic implants and bone without obvious signs of infection.
• Traditional culture methods often fail to detect bacteria in biofilms or intracellularly, leading to misdiagnosis of aseptic loosening.
• Biofilms, small colony variants, and intracellular bacterial presence are increasingly recognized as causes of persistent musculoskeletal infections.

Purpose of the Study:

• To highlight the limitations of standard diagnostic techniques in detecting occult infections in orthopaedic implants and bone.
• To emphasize the role of biofilms and intracellular bacteria in the pathogenesis of osteomyelitis and implant failure.
• To suggest that some cases of aseptic loosening may have an infectious etiology.

Main Methods:

• Review of seminal and subsequent studies on bacterial persistence in orthopaedic infections.
• Discussion of advanced techniques like sonication and microscopy for detecting adherent and intracellular bacteria.
• Exploration of concepts such as biofilms and small colony variants (SCVs).

Main Results:

• Specialized techniques confirm bacterial presence in many culture-negative orthopaedic cases.
• Biofilms, SCVs, and intracellular bacteria contribute to false-negative culture results.
• These persistent bacterial forms may explain recurrent musculoskeletal infections and implant failures.

Conclusions:

• A significant number of orthopaedic implant failures previously attributed to aseptic loosening may stem from undetected infections.
• Understanding bacterial persistence mechanisms like biofilms and intracellular colonization is crucial for accurate diagnosis and treatment.
• Further research into advanced detection methods is warranted to improve patient outcomes in musculoskeletal infections.