A Philadelphia collar is a special orthosis for protecting the cervical spine. This type of orthosis consists of two parts, which are usually connected to each other with a hook-and-loop fastener. The cervical collar is made of very rigid foam, which severely restricts mobility of the head and neck. The foam has the advantage of being easy to wash and permeable to X-rays. There are also models with a so-called tracheal opening, which allows palpation of the carotid pulse and, if necessary, a tracheotomy.
The Philadelphia collar, like almost all types of cervical collars, is used in conservative treatment following a fracture in the cervical spine. One example is a dens fracture.