It’s one thing to get in great physical shape to play a boxer in a movie. It’s quite another to be forced to spend much of the film in an awkward, uncomfortable brace that is secured, vice-like, to your skull. That’s exactly what Miles Teller did, though, in his most recent film.

In the new film "Bleed for This," Teller portrays Vinny “The Pazmanian Devil” Pazienza, a world champion boxer who fractured his neck in a head-on car accident. After the accident, one thing immediately grabs the viewer’s attention: the large ring brace that encircles Pazienza’s head and rests on four metal struts on his shoulders and chest. The device is called a halo fixator (or, more simply, a halo) and it is often used to immobilize the neck after certain types of cervical spine (neck) fractures.

The halo device is composed of several different parts: the ring that encircles the head, four struts that anchor the ring to the shoulders and chest, the chest vest where the inferior portion of the struts attach, and the cranial pins, or, the screws that anchor the struts to the cranium (skull).

The purpose of the halo is to provide as much immobilization as possible for the vertebral fracture in the neck as it is healing. Since it is impossible to cast the neck in a way that would sufficiently limit individual vertebral motion while still allowing a patient to eat, breathe and sleep, the halo serves that function. Other external braces are unable to restrict neck motion beyond approximately 40 percent, while the halo can limit up to 90-plus percent of movement. When the potential consequences of just a few millimeters of movement include paralysis as a result of spinal cord injury, it becomes clear why the rigidity of the halo is so critical.

If it sounds unpleasant, it is. The consequences of the injuries that lead to wearing a halo are far worse, however, making wearing of the brace for periods of up to three months tolerable by comparison. Still, there are aspects of wearing a halo that no one would likely think about.

• For starters, the titanium cranial pins are screwed into the skull. How else to keep the head from moving the neck? Typically, a local numbing agent is applied and then a small drill is used to create holes for the pins. Pin loosening over time is possible, so the screws may need to be tightened every couple of weeks. There can be some discomfort from pressure at the pin site, and there is approximately a 20 percent rate of infection around the pin site.

• Once in the halo, the head, neck and shoulders are forced to move as a unit, making things as basic as sleeping and eating challenging. For instance, there is no sleeping on one’s side. The only way to drink is out of a straw. Getting in and out of a car, or other movements that typically require ducking the head, are tricky, and until the individual gets used to the extra space the halo demands, bumping into things becomes a regular occurrence.

• The chest vest is made of rigid plastic but is typically lined with something, such as sheepskin, to help protect the skin. The lining can get hot and itchy … and smelly.

• While wearing the halo, the neck muscles will atrophy to some degree because they are no longer working to hold the head up. When the halo is removed, patients can have a hard time simply holding their heads up. Consequently, the typical progression is from a halo to a hard plastic collar to a soft collar, and then eventually to no brace at all.

To his credit, Teller went to great lengths to appreciate the experience of wearing a halo. Although he didn’t have the pins screwed directly into his skull, he did wear a legitimate brace with small rubber grips placed on the pins, and they were tightened like a vice around his head to keep the brace still. Teller said he knew the brace was secure because at the end of a day of filming he would have grooves in his forehead due to the pressure from the rubber grips.

Pazienza’s story is remarkable in that he defied medical expectations and returned to fight again. Teller’s willingness to so closely approximate Pazienza’s experience in the halo only adds to the authenticity of the film.