Total and intercondylar notch bone resection in posterior stabilized knee arthroplasty: analysis of five manufacturer designs.

PURPOSE: The study aimed to volumetrically measure and compare the bone amount removed through the intercondylar femoral notch and the total bone amount removed through five different brands of implant design in order to provide orthopaedic surgeons with opinions in respect of implant selection.

METHODS: Ten implants from five different total knee arthroplasty implant manufacturers, namely Nex-Gen Legacy, Genesis 2 PS, Vanguard, Sigma PS and Scorpio NRG PS, were applied to a total of 50 sawbone models. Equal or the closest sizes of each brand on the anteroposterior plane were selected, and cuts were made following the standard technique. The removed bone pieces were measured in terms of volume and length in three planes, and were statistically analysed.

RESULTS: The comparison made by excluding femoral notch cuts did not produce any statistically significant difference between the amounts of bone removed. The following data were volumetrically obtained from the intercondylar femoral notch cut: Vanguard (3.6 ± 0.4 cm3 ), Nex-Gen (3.7 ± 0.5 cm3 ), Sigma (5.7 ± 0.4 cm3 ), Genesis 2 (6.3 ± 0.3 cm3 ) and Scorpio NRG (6.7 ± 0.7 cm3 ). There was no statistical difference between Genesis 2 and Scorpio NRG (n.s.), or between Nex-Gen and Vanguard (n.s.). The smallest volumetric value measured in the removed intercondylar femoral notch cut was obtained using Vanguard.

CONCLUSION: There are significant differences between implant designs in terms of preserving bone stock, and a large proportion of the difference arises from the intercondylar femoral notch cut.