🔍 Key Findings

• Median BFX stem subsidence was only 0.4 mm, but values ranged from −4.1 to 9.8 mm across 177 THRs.
• Subsidence was significantly associated with stem complications (p = .005), but not with non-stem complications (p = .76) or prosthetic luxation (p = .07).
• Most stem complications were intraoperative femoral fissures (8/11), and only one fissure progressed to postoperative femoral fracture.
• Traditional subsidence thresholds of 3 mm and 5 mm poorly predicted complications; most stems exceeding these values remained complication-free.
• Large subsidence can be clinically inconsequential, with two stems demonstrating 8.8 mm and 9.8 mm of subsidence without complications.
• Canal flare index, canal fill, and stem orientation were not associated with subsidence, suggesting limited predictive value of these radiographic measurements.
• Subsidence may reflect consequences of intraoperative fissures rather than cause complications, supporting a possible reverse-causality relationship.
• Clinical interpretation of subsidence should be contextual, considering fissures, implant sizing, femoral morphology, and patient factors rather than relying on numeric cutoffs alone.