This study was to evaluate the stability of a delta keel tibial tray using a block prosthesis and to determine whether a long intramedullary stem is a necessary adjunct to augment construct stability. An experimental technique was used employing strain gauges and deflection transducers to assess the stiffness and principle strains conferred to human cadaveric tibiae under various axial loading conditions.

As a control measure, tests were conducted in the absence of any bone loss, and repeated in a simulated bone defect treated with a metal block. The latter was analysed with and without augmentation of the tibial tray with an intramedullary stem. With axial loading of 2000N, the tray and block configuration resulted in 21% less proximal bone strain than the tray alone. The combined tray, block and stem resulted in 35% less proximal bone strain than the tray alone. Using the tray and block produced 1.06 times more deflection of the tibial tray and using the tray, block and stem 1.03 times more deflection of the tibial tray than the tray alone in the absence of a bony defect.

There was no statistical difference in overall construct stability (p < 0.05) despite the large strain-offsetting effect recorded using the tibial tray in conjunction with the block and stem

These results suggest that isolated bone defects that can be dealt with using a single block and modern standard tibial tray may not require additional supplementation with a long intramedullary stem.