Implant component assembly

An implant component assembly for a joint replacement, the assembly comprising:

• an implant component, the implant component including an interface part configured for attaching to another implant component and an assembly channel,
• an assembly screw for securing the other implant component to the implant component, the assembly screw having a longitudinal axis, a screw head, and a screw shank and being insertable into the assembly channel,
• a screw retention unit configured for keeping the assembly screw within the assembly channel and allowing rotation of the assembly screw about the longitudinal axis,
• another interface part for attaching a joint member, wherein the another interface part comprises a tapered recess and a concave interface surface, wherein the concave interface surface comprises an array of indexing holes,
• a joint assembly channel that extends from the tapered recess along a longitudinal axis of the tapered recess to a side of the implant component opposite to the side of the implant component where the tapered recess is located, wherein the screw head is between the another interface part and the another implant component,
• wherein the screw retention unit includes a screw seat for supporting the screw head, the screw seat comprising a through hole for accommodating the screw shank,
• wherein the screw shank of the assembly screw comprises a threaded portion and an unthreaded portion, the unthreaded portion being located between the threaded portion and the screw head, and
• wherein the screw seat engages a portion of the screw shank having a reduced diameter in comparison to the threaded portion of the screw shank.