Locking strength of Morse tapers used for modular segmental bone defect replacement prostheses

Mechanical testing has been performed to characterize the locking strength of Morse taper locks used for reconstruction of large bone defects. Taper joint pairs were locked with a series of compressive loads increasing from 500 to 3500 N. Following each load application the taper locks were distracted with either an axial load or a torsional load. Additional tapers were loaded with 2 million cycles of axial compression or 2 million cycles of cantilever bending combined with axial compression, followed by axial distraction. The torsional and axial distraction loads increased linearly with the compressive load. Compared to a single compressive load application, cyclic axial loading had little influence on the joint strength, while a combination of axial loading and bending increased the joint strength. Based on these results, in vivo loading should increase the locking strength of Morse taper locks used for bone defect reconstruction.