Bone Preservation in Femoral Intercondylar Box Cut - A Comparative Study between Older and Newer Generation Implants

Introduction: This study was conducted to compare the quantity of intercondylar bone removed during femoral box osteotomy for implantation of three contemporary newer generation posterior stabilized (PS) total knee arthroplasty designs Attune PS (DePuy), Anthem (Smith and Nephews), and NexGen Legacy (Zimmer) with the older version from the same manufacturers.

Materials and methods: We compared the maximum volumetric bone resection required for the housing of the PS mechanism of these six designs. Bone removal by each PS box cutting jig was three-dimensionally measured. The differences between the three designs were analyzed by the Kruskal-Wallis test. The Mann-Whitney U-test was used for pairwise comparisons. The level of significance was set at P < 0.05.

Results: The newer generation implants save approximately 33% of bone that was resected from the box cut as compared to the older versions. DePuys Attune PS saved 27.1% bone as compared to Sigma PS resecting 6.96 cm3 of bone, and Zimmers Persona saved 40.57% bone as compared to NexGen from the intercondylar box cut resecting 6.18 cm3. Smith and Nephew s Anthem and Genesis have no difference in their box volume with both resecting 7.8 cm3 of bone.

Conclusion: Irrespective of implant size, the Attune PS (DePuy) and Nexgen Legacy (Zimmer) cutting jigs always resected significantly less bone than did the jigs of older generations. There was no significant difference in the bone removed during femoral box osteotomy in the newer and older generations of Smith and Nephew.