There are disclosed embodiments of screws for use in orthopedic surgery, particularly in pediatric patients. In some embodiments, inner and outer implantable members are provided, with the outer implantable member threadable on the inner implantable member to provide compression on two or more bone parts. In some embodiments, screw members are provided with a threaded shaft, and the thread continues into the head of the screw member to enable the thread to remain in pediatric bone.