Sabertooth Cat: Bone size does matter

Fig.1. A representation of Smilodon from the year 1903, example of the pioneering work of Charles R. Knight, figure from CHORLTON 1985.

Few extinct predators are as well-known as the sabertooth cats, which are touted for their prowess as ultimate mammalian predators.
But the structure of their fangs revealed that the oval cross-section is inadequate to handle the forces of a struggling prey. To prevent a fracture of the canines it was necessary for the animal to handle and immobilize the prey.

Comparing radiographs of the sabertooth cat, Smilodon fatalis, 28 extant felid species, and the larger, extinct American lion Panthera atrox a recent published research concluded that indeed the humeri of the forelimbs of S. fatalis were much thicker in relation to their length, and the bone cortex was more developed then in the other felids.
Based on these observations, the study deduces that Smilodon was a powerful predator that differed from extant felids in its greater ability to subdue prey using the forelimbs. This enhanced forelimb strength was part of an adaptive complex driven by the need to minimize the struggles of prey in order to protect the elongate canines from fracture and position the bite for a quick kill.

References:

CHORLTON, W. (ed) (1985): Ice Ages (Planet Earth). Time-Life Books: 176
MEACHEN-SAMUELS, J.A. & VALKENBURGH, B. van (2010): Radiographs Reveal Exceptional Forelimb Strength in the Sabertooth Cat, Smilodon fatalis. PLOS One 5(7): e11412. doi:10.1371/journal.pone.0011412
McHENRY, C.R.; WROE, S.; CLAUSEN, P.D:; MORENO, K. & CUNNINGHAM, E. (2007): Supermodeled sabercat, predatory behavior in Smilodon fatalis revealed by high-resolution 3D computer simulation. PNAS Vol. 104(41): 16010-16015