Abstract: A pin alignment guide may be placed on an end of a bone for guiding a pin along a central axis of the bone. The bone has a length extending away from the end of the bone. A body may be configured to overlie the end of the bone. The body may have a contact surface configured to contact the bone and a guide surface configured to guide a pin into the bone. A rod portion may be configured to extend along the length of the bone away from the end of the bone. An extension may be configured to attach to the body and extend away from the body, the extension further configured to couple to the rod portion, such that the rod portion may be aligned along the length of the bone thereby positioning the guide surface of the body to guide the pin.

Abstract: Safety helmets, totally encasing the wearer's head and incorporate breathing apparatus supplying air to and exhausting air from an isolated volume within the helmet, are well known. The isolated volume is defined by a viewing panel, an annular seal and the face of the wearer.There is a problem in fitting and removing such a helmet which has been solved in prior art constructions by making the helmet from two shell halves, hinged together at the crown of the helmet.The invention proposes a one-piece helmet shell, which has a front to rear dimension more the one and a half times that of the wearer's head, and providing a pad so supported that it can be displaced to the rear regions of the helmet, to facilitate fitting and removal of the helmet, and with the helmet fitted pushes the head of the wearer into pressure contact with the annular seal.