# 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 & 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

1. Non-sterile & sterile gloves

2. Alcohol-based hand rub

3. Sharps container
   Sharps container

   If a sharps container is not within arm's length, use a kidney dish or other hard container to temporarily hold used sharps and to carry them to the sharps container for disposal.

4. Skin disinfectant
   Skin disinfectant

   Commonly used preparations include 0.5-2% chlorhexidine in 70% alcohol (Steriprep), or 10% povidone iodine. There is no consensus on the superiority of one agent above another. Caution: chlorhexidine solutions may be associated with burns and skin breakdown in infants < 2 months old.

5. Reduction bed with double mattress and folded towels

6. Equipment to perform IV cannulation

7. Analgesia & light sedation (consider morphine 5 mg IV, midazolam 2 mg IV & prochlorperazine 12,5 mg IM)

8. Cones calipers

9. Swan neck & S-hook
   Swan neck & S-hook

10. Orthopaedic rope

11. Orthopaedic weights or bags of saline (40kg needed)

12. Alcohol swab

13. 10 ml syringe, aspiration needle (ideally blunt fill), injection needle & lignocaine vial

14. Scalpel blade

15. Suture kit

16. Razor/extra scalpel blade

## 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.

1. Perform hand hygiene.

2. Attach swan neck to bed. Hang a 5 kg orthopedic weight over the swan neck pulley, attached to the S-hook.

3. Attach cardiac and sats monitors to patient.

4. Don non-sterile gloves. Obtain IV access and administer analgesia.

5. Locate
   Locate

   an area 1 cm above the pinna and aligned with the external auditory meatus on either side of the patient’s head. Palpate to exclude blood vessels, and shave the area.

6. Draw up and inject ± 3 ml local anaesthetic in each area, starting with raising a bleb on the skin surface, and ending with injecting the periosteum.

7. Open the suture kit and create a sterile field. Pour disinfectant into the bowl, and open the scalpel onto the field. Open the Cones calipers in a sterile manner.

8. Don sterile gloves.

9. Clean the identified areas with skin disinfectant.

10. Make a 1 cm incision above each ear. Dissect bluntly down to the periosteum on each side using curved artery forceps.

11. First insert the pins into the caliper ends. Hold the calipers over the patient’s head. Use the spanner to

    screw
    screw

    Tightening the calipers:

    Screwing in the pins:

    the bolt at the top of the calipers until the caliper ends are firmly against the skull. Use the back of the spanner to screw the pins into the skull with a back and forth motion until they are embedded in the periosteum. Give a firm tug to check that they are secure.

12. Tie a rope to the top of the calipers and attach it to the S-hook. The patient is now in 5kg traction.

13. Remove the cervical collar. Flex the neck 20-30° by raising the swan neck and supporting the head with folded towels. Wait 5 minutes. Check for any clinical deterioration and take X-rays of the neck.

14. Every 5 minutes, add 5 kg, take an X-ray and do a neurological examination. Repeat this process to a maximum of 40 kg weight.

15. When the facet joints are aligned ‘’tip to tip’’ on X-ray, then the neck can be extended by 10° by lowering the swan neck and removing the towels behind the head.

16. Reduce the weight down to 5 kg and repeat neurological examination and X-rays to confirm reduction.

17. Record completion of the procedure in patient notes.

## 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

1. Failed reduction

2. Neurological deterioration during the procedure

3. Temporal artery haemorrhage
   Temporal artery haemorrhage

   If the incision is in line with the auditory meatus, this is unlikely to happen. Direct pressure will control the bleeding and if not, a haemostatic stitch can be used.

4. Septic pin sites
   Septic pin sites

   This usually occurs when patients are kept in traction for many days. Local cleaning and dry gauze dressings with oral antibiotics (flucloxacillin) will usually resolve this.

5. Sharps injury to healthcare personnel

## 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.