An instrument kit for reaming a cavity within a resected head of a bone is provided. The kit includes a reaming guide, at least two adaptor sleeves and a reamer. The reaming guide includes an elongate stem portion insertable into a cavity extending into the bone from a resection surface at the head of the bone and a neck portion. The at least two adapter sleeves are mountable upon the reaming guide. Each adapter sleeve has a longitudinal axis, being generally cylindrical and a bore configured to receive part of the neck portion of the reaming guide. When the adapter sleeve is mounted upon the neck portion of a reaming guide inserted into a cavity in a bone the reamer is arranged to ream a cavity into the resection surface of the bone around the neck portion.
