# Cones Calipers

## Overview

This module describes how to apply cones calipers to reduce cervical dislocation.

## Indications

1. Cervical facet dislocation

## Contraindications

1. Unconscious or uncooperative patient
2. Basal skull fractures
3. Weigh up the risks and benefits in patients with severe degloving or septic scalp wounds

## Patient information and consent

Always verify your patient’s identity and obtain informed consent before proceeding.

### How do I explain this procedure?

“You have dislocated a neck bone, which puts pressure on your spinal cord. I need to correct the dislocation immediately using a device called Cones calipers.”

### What can my patient expect?

“I’m going to put you on a bed with two mattresses and some folded towels so that your neck can move freely. I’m going to give you injections so that your head will be numb, and I’m going to make a small cut above each ear. Then I’ll attach these calipers, and I’ll hang weights from a pulley to gradually pull your neck straight. Each time I add weights, I’ll take an X-ray to check if I’ve fixed the dislocation. This process is uncomfortable, and it might feel scary, but is essential to protect your spinal cord.”

### What is my patient’s role?

“You need to communicate with me while I add weights. Tell me if any of your limbs become numb or you can’t move anymore.”

## Preparation

Prepare a trolley with equipment. An assistant is useful for this procedure.

### Documentation

1. Patient notes

### Equipment

## Site & Positioning

The patient should be supine on a reduction bed with a double mattress. Place a folded towel or sheet under the patient’s head to maintain neutral alignment. Place the patient in reverse Trendelenburg at 10-20°. The patient should be wearing a cervical collar.

## Procedure

Follow medical asepsis with sterile gloves.

## Troubleshooting

I have reached 40 kg and there is still no reduction on X-rays.

Reduction is usually only achieved at 30-40 kg, and failed reduction occurs 20% of the time. This is often due to inadequate flexion. Start the reduction process again from 5 kg, flex the neck to 20-30°, then incrementally increase the weight by 5 kg every 5 minutes as previously described. Administering 2 mg midazolam can help the patient relax and aid reduction. Do not oversedate, as the patient needs to be awake for the procedure.

My patient has deteriorated neurologically during traction.

Remove all weights, apply a cervical collar, give oxygen, keep mean blood pressure over 85 mmHg and arrange for an urgent MRI scan. Refer the patient to a specialist facility.

The pins are slipping on the skull.

The pins need to penetrate 3-5 mm into the skull, and the barrel of the Cones needs to be flush on the skull. Use the spanner to rotate the pin to and fro to allow it to self-drill into the hard skull, while the Cones calipers are tightened. Pull as hard as you can on the calipers once applied, to check the pins are secure. They should not be movable by forceful pulling if applied correctly. If pin slippage occurs during reduction, remove all the weight, place the neck in neutral position and reapply the pins correctly.

## Risks

## References

1. Biyela N, Paterson A, Hendricks A. Application of Cones Calipers for cervical spine injuries. 2017. Available from: https://open.uct.ac.za/handle/11427/27610.