For reliable osseointegration of an uncemented press-fit femoral stem, the interface conditions must permit bony ingrowth into the porous coating. What is the approximate upper limit of interfacial micromotion beyond which fibrous tissue rather than bone forms?
- A About 15 micrometres
- B About 150 micrometres ✓
- C About 500 micrometres
- D About 1500 micrometres
Correct answer: B. About 150 micrometres
Explanation
Animal and biomechanical studies established that relative micromotion at the bone-implant interface of more than roughly 150 micrometres leads to fibrous tissue ingrowth rather than bony fixation. Micromotion below this threshold permits osteointegration into pores optimally sized between about 100 and 400 micrometres. This is why intraoperative press-fit stability is essential: a stem that is microscopically mobile will never achieve durable ingrowth regardless of surface porosity.
Reference: Miller's Review of Orthopaedics, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.