C1-C2 fusion joins the top two bones of your neck so they heal together as one solid piece. It is done when these bones have become loose or unstable and could put the spinal cord at risk. If done at the right time and for the right reasons it can be a rewarding surgery.
Reviewed by Dr. Kshitij Chaudhary — Last reviewed October 2026
What is C1-C2 fusion?
The top two bones of your neck are called C1 and C2. They sit just below your skull.
C1 is a ring. C2 has a small peg (the odontoid) that rises up inside that ring. This joint is where about half of the turning in your neck happens. The spinal cord, the brainstem and the arteries that feed the back of the brain (the vertebral arteries) all pass through this area.
In a C1-C2 fusion, the surgeon locks C1 to C2 with screws and rods (or screws and a wire) and adds bone graft. Over the next few months, the two bones grow together into one.
Who needs this surgery?
You may need it when the joint between C1 and C2 is loose, broken or badly worn, and there is a risk to the spinal cord. Common reasons:
- A broken (fractured) odontoid peg, especially one that has not healed
- A slipped or twisted C1-C2 joint (rotatory subluxation)
- Rheumatoid arthritis that has loosened the ligaments around the joint
- Os odontoideum, where the peg never joined the rest of C2 (a variation from birth)
- Other birth defects, such as Klippel-Feil syndrome
- A tumour or infection (tuberculosis) in these bones
- Arthritis of the C1-C2 joint causing severe pain
- A previous fusion that did not heal
Not everyone with a problem here needs an operation. If you have been told you need this surgery and want to be sure, you can send your MRI for a second opinion.
Are there options other than surgery?
Sometimes. A stable fracture of the peg can heal in a firm collar or a halo vest over about 10 to 12 weeks. Surgery is usually advised when the joint is unstable, when the spinal cord is under pressure, when a fracture has not healed, or when a collar alone is not enough. Dr. Chaudhary will go through which of these applies to you.
What are the two main techniques?
Both operations do the same job. Both are done through a single cut at the back of your neck, and both lock C1 to C2. They differ in where the screws go.
The Harms technique (screws and rods). One screw goes into the solid side block of bone on each side of C1. Another goes into C2 on each side. A rod links the two screws on each side. This method lets the surgeon realign the bones using the screws before locking them. The Harms technique builds on the plate-and-screw method first described in Mumbai in 1994 by Dr. Goel and Dr. Laheri. Dr. Chaudhary learnt the technique directly from them. C1-C2 and craniovertebral junction surgery is one of his main areas of expertise.
The Magerl technique (transarticular screws). One long screw passes on each side straight through the C1-C2 joint, from C2 up into C1. It is sometimes combined with a wire and a bone graft at the back for extra strength. It gives a very strong hold, but it needs the bones to be well aligned first, and the artery on each side to be in a safe position.
Which one is right for me?
The choice depends on your scans: the path of your vertebral arteries, the quality of your bone, whether the bones can be realigned. In some people, the artery or bone shape makes one screw position unsafe. When that happens on one side, there are other safe anchor points, such as a screw in C3 or a screw through the C2 lamina.
This is why careful planning on CT scans comes first.
What tests do I need first?
- X-rays. Bending forward and back shows whether the joint can be realigned.
- A thin-slice CT scan to see the bones in detail and measure the screws. it is combined with an angiogram to map your vertebral arteries
- An MRI to see the spinal cord and ligaments.
What happens on the day of surgery?
- Anaesthesia. You have a general anaesthetic. The anaesthetist with the surgical team decide together how best to place the breathing tube so your neck stays protected.
- Position. You lie face down. Your head is held steady in a head holder, with your neck in a neutral position.
- Monitoring. Nerve monitoring may be used during surgery, and live X-ray guides every step.
- The cut. One cut in the middle of the back of the neck just inside the hairline at the base of your skull. The muscles are gently lifted off the bone.
- Screws and rods (or Magerl screws). The screws are placed with X-ray guidance or using computer navigation. If the bones are out of line, they are realigned before the rods are locked.
- Bone graft. Graft is laid over roughened bone so the bones grow together. It is usually taken through a small cut over your hip bone (the iliac crest).
- Closing. The wound is closed in layers and a firm collar is fitted.
What are the risks?
All surgery carries risks, and this one is delicate because of what lies close by. Your CT angiogram and careful planning are there to keep these low.
- Injury to the vertebral artery. This is uncommon but the most serious risk, and the main reason for scanning the arteries beforehand.
- Pain or numbness at the back of the head from irritation of a nerve (the C2 nerve) near the screw.
- Bleeding from the veins around that nerve. This is usually easy to control.
- Infection, or a leak of spinal fluid (which can be repaired).
- A screw sitting in a less than ideal position, or the bones not fusing fully.
- Rarely, injury to the spinal cord or nerves.
Dr. Chaudhary will explain how these apply to you before you decide.
How long will I stay in hospital?
Most people walk within a day and stay in hospital for 2 to 3 days, provided there was no weakness or other nerve problem before surgery. If the operation is done because the spinal cord is under pressure (myelopathy), the stay is sometimes longer. You will have X-rays before you leave the hospital. A CT scan is done only if there is any doubt about screw position.
What is recovery like?
- You will wear a firm neck collar for about 4 to 6 weeks.
- You will have regular X-rays to check stability and healing. Bending and straightening X-rays may be done once the bones have settled.
- A CT scan a few months after surgery confirms that the bones have fused.
- Recovery can take longer if you had weakness or other nerve symptoms before surgery.
Will I lose neck movement?
Yes, some. Because about half of your head-turning happens at C1-C2, turning your head to each side will be reduced. The rest of your neck takes up some of the work over time.
Questions to ask your surgeon
- Why do I need a fusion rather than a collar?
- Which technique is best for me, and why?
- What do my scans show about my arteries?
- Where will the bone graft come from?
- How long will I need the collar?
- How much neck movement will I lose?