“Trunionitis”: A Cause for Concern?

Large diameter heads (LDH) are connected to the stem by means of a Morse taper. An adapter sleeve may be also used to adjust the head offset intraoperatively and/or to change the bearing couple and size. This paper explains the effect of head diameter and friction coefficient on the frictional torque acting on the tapers. A greater frictional torque tends to increase the micromotion occurring with in the tapered junction. Other crucial parameters are those that determine the distance between the center of the head and the tapered junction engagement level (e.g. head offset, adapter sleeve). Caution must be paid in using LDH coupled to small tapered junction, with or without an adapter sleeve. [Copyright &y& Elsevier]