Morse-type tapers: factors that may influence taper strength during total hip arthroplasty

We studied the effect of varying impaction force, repeated impactions, and fluid contamination on the disassembly strength of Morse-type tapers in 4 commercially available, modular femoral total hip components. The effect of varying techniques of taper assembly on the distraction force was studied. Our results show a reproducible and linear relationship between the taper impaction force and the disassembly force. The force necessary to separate the taper for a given impaction force varied, however, among manufacturers. Repeated impactions added little strength, and we found that when multiple impactions of varying force are used, the strength is roughly equivalent to the expected strength from the single strongest blow. Fluid contamination at the taper interface had unpredictable effects on taper strength.