Abstract

Lubinus SP II stems are cemented either line-to-line with the largest broach or one-size undersized. The purpose of this study was to compare both implantation techniques. We used 18 polymeric stem replicas cemented line-to-line and undersized in paired cadaveric femora and analyzed them with CT scan images. Cementing Lubinus stems line-to-line resulted in higher medullary canal-filling indices (28.26 ± 4.10%), thinner cement mantles (3.29 ± 0.40 mm), more cement defects (5.12 ± 1.69%) and more areas of thin cement (23.81 ± 7.13%) than undersizing (respectively : 23.61 ± 4.24%, 3.62 ± 0.43 mm, 1.48 ± 2.04%, 15.11 ± 5.93%). In both settings, over 80% of areas of thin or deficient cement were supported by cortex. Using a line-to-line technique, adequate stem alignment was achieved without distal centralizer. Undersizing the stem and using a distal centralizer reduced the incidence of distal cement defects by a factor 10. While stems cemented line-to-line might have mechanical advantages, undersizing and using distal centralizers reduced potential pathways for debris migration to the bone-cement interface.