Larger stem to bone diameter ratio predicts lower cemented endoprosthesis failure.

Area of Science:

• Orthopedic surgery
• Biomedical engineering
• Oncology

Background:

• Patients with endoprosthetic reconstruction are living longer, increasing reliance on implants.
• Aseptic loosening and mechanical failure are major causes of endoprosthesis failure.
• Tumor resection, bone loss, and radiation therapy elevate complication risks.

Purpose of the Study:

• To determine the overall rate of endoprosthesis failure at 5-year follow-up.
• To investigate if resection length impacts implant failure rates.
• To assess if implant size and stem-to-bone ratio affect endoprosthesis failure.

Main Methods:

• Retrospective analysis of 150 patients undergoing cemented hip or knee endoprosthetic reconstruction (1999-2022).
• Radiographic assessment of 55 patients with >5-year follow-up for resection length, bone diameter, and stem diameter.
• Calculation of resection percentage and stem-to-bone diameter ratios to analyze failure relationships.

Main Results:

• Implant failure was associated with a smaller mean stem-to-bone diameter (36% vs. 44%).
• A stem-to-bone diameter ratio <40% was a critical threshold, with 90% of failures occurring below this ratio.
• A stem-to-bone ratio <40% significantly increased failure risk (OR 0.68, p<0.001).
• Resection length did not impact failure rates.

Conclusions:

• Larger stem diameters are beneficial for cemented hip and knee endoprostheses.
• Stem-to-bone diameter ratios below 40% substantially increase the likelihood of implant failure.