Instrument for removal of a bone cement tube in an artificial femur head reimplantation

Claim 1

An instrument for removing a hollow bone cement tube from a cavity in a bone, said bone cement tube having a generally annular tubular configuration with a radially innermost diameter and a radially outermost diameter, said instrument comprising: a hollow tube having an open operating end and an open insertion end adapted to be placed within said bone cement tube, said hollow tube having a radially outermost diameter which is smaller than said radially innermost diameter of said bone cement tube to enable passage of said hollow tube within and through said bone cement tube; male thread means in said hollow tube adapted for engagement with female thread means in said bone cement tube for affixing said hollow tube with said bone cement tube; a mandrel extending through the interior of said hollow tube from said operating end to beyond said insertion end and freely rotatable relative to said hollow tube; collet means attached to said mandrel at an end thereof extending beyond said insertion end of said hollow tube, said collet means being adapted to normally extend radially no further than the outside diameter of said hollow tube during insertion of said hollow tube into said bone cement tube; said collet means being formed with a frustoconical configuration having a larger diameter portion adjacent said insertion end of said hollow tube which in the insertion position of said collet means extends no further than the outer diameter of said hollow tube; longitudinal slots formed in said collet means for enabling said collet means to be radially spread to have said larger diameter portion extend radially beyond beyond the outer diameter of said hollow tube; internal thread means in said collet means and external thread means on said mandrel for engagement with said internal thread means; tapered peripheral surface means formed on said larger diameter portion of said collet means adapted to engage complementary tapered peripheral surface means formed on said insertion end of said hollow tube to facilitate spreading action of said collet means when said collet means is urged against said insertion end by operation of said mandrel through interengagement of said external thread means and said internal thread means; said mandrel being operable to urge said collet means against said insertion end of said hollow tube to radially spread said collet means beyond the outer diameter of said hollow tube in order that said collet means may be brought into abutment with the inner end of said hollow bone cement tube to facilitate removal thereof by manipulation of said mandrel after said collet means has been inserted together with said hollow tube through said bone cement tube to be located on an inner end thereof; and means for applying to the inner end of said bone cement tube through the engagement of said spread collet means with said bone cement tube an outwardly directed force for facilitating removal of said bone cement tube.