Cervical vertebrae

Key points

The neck has seven cervical vertebrae (the bones stacked to form the spine, here in the neck), and their small bodies carry the least body weight of any vertebrae^1,2.
The atlas (C1, the top neck vertebra, which carries the skull) is a ring with no body, and the axis (C2) carries a peg of bone called the dens². In CT scans (detailed X-ray pictures) of 20 healthy volunteers, C1–C2 supplied 54% of neck rotation³.
A review reports that in cadaver specimens (from bodies donated for study) hit along their length, the neck buckled and was injured within milliseconds, before the head moved visibly⁴.
After US football banned spearing and first contact with the top of the helmet in 1976, a national registry documented a dramatic fall in neck injuries⁵.
In X-rays of football players and controls, a canal ratio of 0.80 or less flagged 93% of players with cord neurapraxia (the mildest grade of nerve injury), but predicted too poorly for screening⁶.

Function

Seven bones, three of them unusual

The adult spine has 24 vertebrae: seven cervical ones in the neck, twelve thoracic ones below them and five lumbar ones in the lower back². C3 to C6 are described as typical cervical vertebrae, and C1, C2 and C7 as atypical¹. Their small bodies reflect that they carry the least body weight². The cervical spine holds the upper spinal cord and the vertebral arteries, which help supply blood to the back of the brain⁷.

The parts of a typical neck vertebra

Engraving of a single neck vertebra seen from above, with the front at the top. A small, oblong body sits at the front. Behind it, two pedicles and two laminae form a large triangular opening for the spinal cord, closed at the back by a short spinous process that splits into two tips. On each side a transverse process holds a small round hole, the foramen transversarium, between front and back tubercles. Flat superior articular processes sit behind the transverse processes. The body, pedicle, lamina, spinous process, transverse process, its tubercles, the foramen transversarium and the articular processes are labelled. — A typical cervical vertebra seen from aboveHenry Vandyke Carter, in Henry Gray, Anatomy of the Human Body (1918), Fig. 84. Public domain, via Wikimedia Commons. (source, Public domain)

A typical neck vertebra has four notable features^1,2:

The spinous process (the bony point at the back) usually splits in two at its tip². It is short on C3 to C6, but C7’s is much longer and forms the bump at the base of the neck².
The transverse processes (the spurs to each side) are sharply curved, in a U shape, so the cervical spinal nerves can pass². Each holds an opening, the transverse foramen, through which an important artery supplying the brain rises up the neck².
The uncinate process is a raised lip of bone at the back edges of the top of the body, on C3 to C7¹. It meets the vertebra above to form the uncovertebral, or Luschka, joint¹.
The articular processes (the parts that form joints with the next vertebra) are flattened and face mostly up or down². This gives the neck wide bending in each direction and wide rotation².

In a cadaver study of 14 neck segments, the uncovertebral joints mainly controlled extension (bending backward) and side bending, then twisting⁸.

The atlas and the axis

The atlas, or C1, supports the skull². It has no body and no spinous process, and is a ring made of a front arch and a back arch².

Engraving of the atlas, the first neck vertebra, seen from above with the front at the top. It is a ring with no body, made of a short anterior arch at the front and a longer posterior arch at the back, each with a small tubercle. Two thick lateral masses on the sides carry large oval, cupped superior articular surfaces. Dotted outlines inside the front of the ring mark where the odontoid process of the axis and the transverse atlantal ligament sit. Transverse processes with a foramen transversarium project to each side, and a groove for the vertebral artery and first cervical nerve runs across the posterior arch. These parts are labelled. — The atlas (first cervical vertebra) seen from aboveHenry Vandyke Carter, in Henry Gray, Anatomy of the Human Body (1918), Fig. 86. Public domain, via Wikimedia Commons. (source, Public domain)

The axis, or C2, carries the dens (also called the odontoid process), a peg of bone rising from its body². The dens meets the inside of the atlas’s front arch, and the transverse ligament holds it there². The joint between the atlas and the skull lets the skull rock forward and back, as in nodding “yes”². The joint between the atlas and the axis includes a pivot around the dens, letting the head turn right or left².

In CT scans of 20 healthy volunteers turning the head fully, neck rotation averaged 69.7 degrees³. C1–C2 supplied 37.9 degrees of that³. In X-rays of 70 healthy people, forward and backward bending was largest at C4/C5 and C5/C6⁹.

Breakdown

How the neck gives way under a head-first blow

A review of neck injury in sport reports calculated compressive load limits of 3,340 to 4,450 newtons (a unit of force)⁴. It describes axial loading (load pressing along the neck’s length) with the head bent forward about 30 degrees, as in a head-first tackle⁴. In that position the neck’s normal curve disappears, and with it the region’s energy-absorbing spring⁴. The review reports that in cadaver specimens hit along their length, the neck buckled and was injured within 2 to 31 milliseconds of impact⁴. The head had not yet visibly moved⁴.

Two rugby union reviews differ on the main mechanism^10,11:

Buckling. A systematic review (a set, checkable search of the research) concluded that most neck injuries more likely come from buckling¹⁰. It judged hyperflexion (bending forward past the normal limit) an unlikely cause of most of them¹⁰.
Hyperflexion. A 2002 review reported hyperflexion as the most commonly reported mechanism¹¹. It linked it to fracture-dislocation (a broken bone with the joint forced out of place) at C4–C5 or C5–C6¹¹.

In a facet dislocation, one of the small joints between vertebrae is forced out of place¹⁰. The systematic review found these most common, often on both sides, and mostly at C4/5 and C5/6¹⁰. In computer simulations of a head-first tackle using a model of a rugby player, starting with the neck extended led to buckling¹². Loads went beyond normal levels, typical of facet dislocations on both sides¹². Starting with the neck flexed raised compression but stayed within normal limits¹².

Football and the 1976 rule change

US college and high school football banned spearing and first contact with the top of the helmet in 1976⁵. A national registry of head and neck injuries in tackle football has gathered data since 1971⁵.

That registry then documented a dramatic fall in neck injuries and quadriplegia (paralysis of all four limbs) from 1976 to 1987⁵. A 2004 position statement (an expert group’s agreed view), co-written by the registry papers’ lead author, says the rules dramatically cut catastrophic neck injuries^5,6,13,14. But it says the rules on helmet contact are seldom enforced, and players still often lead with the head¹³. It names axial loading from head-down contact as the main cause of spinal cord injuries in tackle football¹³.

A 1993 paper on “spear tackler’s spine” shares a lead author with the registry findings above and draws on the same registry^5,6,14. It found 15 cases from 1987 to 1990, using registry data and the senior author’s practice¹⁴. It named four features: a narrow spinal canal, a neck curve that stayed straight or reversed, X-ray signs of past injury, and past spear tackling¹⁴. Four of the 15 players had permanent nerve deficits¹⁴.

One study covered US high school and college football from 1989 to 2002¹⁵:

There were about 15 direct catastrophic neck injuries a year: 1.10 per 100,000 high school and 4.72 per 100,000 college players¹⁵.
76 players had quadriplegia, and spear tackling by defensive players remained the main cause¹⁵.
9 players had an injury at C1 or C2 alone, and 7 had one there plus another lower in the neck¹⁵.

Which sports

From 2005/06 to 2014/15, US high school athletes in 24 sports had these neck injury rates¹⁶. Each is per 100,000 athlete-exposures (one athlete in one practice or game)¹⁶:

Neck injuries per 100,000 athlete-exposures. Bars start at zero; the table below gives each value with its source.

Group	Neck injuries per 100,000 athlete-exposures
Football	10.10¹⁶
Wrestling	7.42¹⁶
Girls’ gymnastics	4.95¹⁶
24 sports overall	3.04¹⁶

One case report (a report on a single patient) describes a C6 spinous process fracture in a 21-year-old cadet¹⁷. He had done several sets of overhead presses, resting the bar across his lower neck and shoulders¹⁷.

The size of the spinal canal

Two studies below compare the spinal canal (the channel holding the spinal cord) with the vertebral body, as a ratio, on side-view X-rays^6,18. Of 124 professional and 100 rookie football players, 32% and 34% had a ratio below 0.80 somewhere from C3 to C6¹⁸. Another study, with the same lead author as the registry papers, compared several groups of football players with a large control group^5,6,14. A ratio at or under 0.80 had 93% sensitivity for short-lived cord neurapraxia⁶. Sensitivity is the share of cases a test flags.

But the ratio’s positive predictive value, the share of flagged people who have the condition, was 0.2%, too low for screening⁶. The same study concluded that, when the spine is stable, a canal narrow from development seems not to predispose to permanent catastrophic nerve injury⁶. The stinger page covers a related measure of canal width, the Torg ratio, in players with stingers¹⁹.

Wear over the years

In CT scans of 360 adults aged 21 to 79 at one Chinese hospital, uncovertebral joint wear began in the 20s and grew with age²⁰. It was most marked at C5–6, then C4–5 and C6–7²⁰.

Studies of players found degenerative changes (gradual wear and breakdown) in the neck^21,22:

French rugby. In MRI scans (which show soft tissue in detail) of 206 elite male players without symptoms, the C2 to C7 findings were mainly disc changes²¹. They were seen most often in players over 21²¹.
Front-row rugby. Blinded readers found significantly more wear on X-rays of 14 professional front-row players than of non-players²². The players did not report more symptoms²².

Recovery

What happened after cord injuries

A systematic review on return to play after spinal cord concussion found 16 studies²³. Each was a case-control study, case series or case report²³. Symptoms over 24 hours were more frequent in those with later recurrence or cord injury (36.36%) than in those without (11.11%)²³. In the 1989 to 2002 football study, 43 players had cord neurapraxia¹⁵. Of those, 16 went back to football, and none of the 16 had permanent quadriplegia¹⁵.

After neck surgery

A systematic review of 9 observational series covered 175 athletes²⁴. Of the professional athletes, 75% returned to their sport after neck surgery, mostly for a herniated disc (one whose soft centre pushes out)²⁴. Of recreational athletes aged 10 to 42, 76% returned to play²⁴. The review found little published research on this²⁴. Outcomes were unclear except after single-level fusion (an operation fixing the bones of a joint together) for a herniated disc²⁴.

A 2026 modified Delphi survey, a method that polls a panel of experts in rounds to work toward agreement, asked 34 sports spine surgeons²⁵. The panel reached consensus to recommend return to high-impact, high-frequency sport after a healed C1 fracture²⁵. That fracture had been fixed by open reduction and internal fixation, surgery that sets the bone and holds it with implants²⁵. The panel reached the same consensus after one-level fusion or laminectomy, a surgery removing part of a vertebra’s back arch²⁵. These are the panel’s agreed opinions, not measured outcomes²⁵.

The muscles around the bones

One study put 22 active college students in three groups; its abstract does not say the groups were random²⁶. Some added a head extension exercise to 12 weeks of lifting²⁶. In them, total neck muscle cross-sectional area (slice size) on MRI rose from 19.5 to 22.0 square centimetres²⁶. In students who lifted with no neck exercise, neck muscle area did not change, though quadriceps area rose 7%²⁶.

Connections

Bones and discs

The seven cervical vertebrae form the neck region of the spine, above the thoracic and lumbar vertebrae². Each intervertebral disc keeps neighbouring vertebral bodies from touching bone to bone²⁷.

Nerves and nearby conditions

A 2024 study calls a stinger a short-lived injury of the brachial plexus or of cervical nerve roots (where nerves leave the spinal cord)²⁸. The brachial plexus is the network of nerves, starting at the neck, that serves the arm. A 2022 European consensus says cervical ribs (extra ribs growing from a neck vertebra) occur in 0.5% to 2% of people²⁹. It says 5% to 10% of people with one develop thoracic outlet syndrome²⁹.

Exercise and stretch pages

Related exercise pages: neck isometric hold and overhead press. One professional rugby squad of 27 players was studied looking back over two seasons³⁰. The season with isometric neck strengthening had fewer match injuries, but neck injuries did not differ significantly (6 against 8)³⁰.

Related stretch pages: upper trapezius stretch and upper back stretch. In 15 healthy men, the levator scapulae measured stiffer, read by the authors as more lengthened, in neck positions bending away³¹. In a meta-analysis (pooled studies) of healthy people, four stretching studies of the upper back and neck showed no clear effect on posture³².