Cranial tongs, calipers, and stereotactic frames are medical devices that aid in the diagnosis and/or treatment of a variety of medical concerns, such as diseases and injuries to the brain and cervical spine.
Cranial tongs and calipers are used mainly in skull or spinal traction procedures. Such procedures are essential in the treatment of injuries and diseases of the spinal column.
The spinal column is made up of a series of vertebrae (irregular bones) that starts at the bottom of the skull to the bottom of the lower back. Most people have 33 vertebrae, but there are some with 32 or 34. The spinal column houses the spinal cord, which is the main pathway of signals from the brain to the rest of the body. Any injury or damage to the spinal column must be treated and treatment may require applying traction to the spine.
Traction is achieved by stretching the spinal column while the patient is in a lying position. This can be done several ways, but the most common is using the skull traction method that involves attaching a cranial tong or caliper to the skull. A certain amount of weight is used to create a pulling action on the cranial tong, thus creating traction in the spinal column.
Stereotactic frames are devices that are also attached to the skull but are primarily used in brain surgeries, such as the implantation of deep brain stimulators and performing a stereotactic brain biopsy or cranial radiosurgery, among others.
Patients who require placement of a cranial tong, caliper, or stereotactic frame are those with an injury to the cervical spine or a disease that is affecting the brain, such as Parkinson’s disease.
Spinal traction is usually required for patients who need to regain mobility of the cervical spine after being diagnosed with pinched nerve roots or herniated intervertebral disc (slipped disc).
The use of stereotactic frames is common in neurosurgery. One such procedure is called stereotactic surgery, which is a minimally invasive surgical method for locating and treating small targets within the brain. Treatment can include radiosurgery, implantation of devices, removing tissue (ablation), biopsy, or stimulation of a specific area.
There are four basic types of stereotactic frames: burr hole mounted, arc-quadrant, arc-phantom, and simple orthogonal. The use of a particular type will depend on the procedure and objectives.
Even though spinal traction and stereotactic surgeries have been proven to be highly effective procedures, positive outcomes cannot always be expected. Some procedures have excellent rates of success while others do not. One of the procedures that is associated with a higher success rate is called thalatomy. The procedure makes use of a stereotactic frame to stimulate electrodes in the thalamus. Studies show that 90% of patients who underwent the procedure experienced an immediate relief of tremors associated with Parkinson’s disease. Spinal traction is considered to be a safe and effective procedure, but there are associated risks and possibilities of complications that can affect up to 37% of patients.
Although skull traction devices and stereotactic frames have different purposes, they do have one thing in common: they need to be attached to the skull using metal pins. Skull traction devices usually have at least 2 pins, while stereotactic frames have at least 4 pins depending on the device.
Prior to attaching the devices, a local anaesthetic is usually injected into the area where the pins are installed. The area is then sterilised and the devices are positioned. The pins are then screwed into the skull using a specific amount of pressure, which is about 4-inch pounds of torque. This is to avoid penetrating the skull.
For skull traction procedures, weight is added progressively to the device. The amount of weight added to the end of the device will depend on the vertebra being treated, which is usually about .5 kg per vertebra. The initial weight is 2.5 kg, which can go up to about 20 kg. The weight will need to be reduced once the required neck extension has been achieved.
The application of cranial tongs, calipers, and stereotactic frames does have risks and some complications may develop.
Due to the nature of the devices, there is a risk of the pins penetrating the skull, especially for patients with bone degenerative diseases or minute skull fractures.
Common complications associated with spinal traction include bleeding of the temporal artery, pressure sores on the skull, sepsis, and development of sixth nerve palsy.
Infection is a major cause of concern in skull traction procedures. Several case studies proved that infection is sometimes not detected until after a patient’s death or a few days before death.
Michael Safee, John Burke, Michael W. McDermott;”Techniques for the application of stereotactic head frames based on a 25-year experience”; http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4846396/
EO Uche, OE Nwankwo, E. Okorie, A. Muobike;”Skull Traction for Cervical Spine Injury in Enugu: A 5-year retrospective multicenter analysis of the clinical outcomes of patients treated with two common devices”; http://www.njcponline.com/article.asp?issn=1119-3077;year=2016;volume=19;issue=5;spage=580;epage=584;aulast=Uche