Neck fusion is one of the surgical options commonly recommended when neck pain symptoms become chronic and severe—such as when radiating arm pain or weakness makes it difficult to get dressed, lift objects, or type.
This surgery typically involves reducing pressure on the affected spinal nerve(s) and stabilizing at least part of the cervical spine by fusing vertebral bones together at one or more cervical levels. It is almost always done in combination with a discectomy, so it is most commonly referred to as an anterior cervical discectomy and fusion, or ACDF for short.
While neck fusion has a good record of eliminating or reducing neck-related arm pain, tingling, and weakness, many patients want to know how much neck mobility might be lost when one or more mobile joints in the neck are fused solid—and whether that can impact quality of life. This article examines those concerns and highlights realistic expectations for neck mobility after various types of neck fusion surgeries.
The Neck’s Normal Range of Motion
The cervical spine consists of a stack of seven vertebral bones (labeled C1 through C7) that are connected from the base of the skull all the way down to the chest. Neck mobility, also referred to as the cervical spine’s range of motion, varies somewhat from person to person and depends on several factors, including:
- Shape and structure of vertebral bones and their facet joints
- Cushioning provided by discs between the vertebral bones
- Flexibility of surrounding muscles and ligaments
Cervical range of motion is typically measured in three planes: sagittal (forward/backward), coronal (side to side), and transverse (rotation). Studies do not perfectly agree on what is an average range of cervical motion, but the following is an estimate for point of reference:
- 60 degrees of flexion (moving the head forward)
- 75 degrees of extension (moving the head backward)
- 45 degrees of lateral flexion (bending ear toward the shoulder)
- 80 degrees of rotation (turning to the side)1
Watch: Cervical Spine Anatomy Video
Due to aging, neck mobility naturally reduces over time, with the first significant drop typically happening between ages 30 and 39.1
Fusion Surgery’s Effect on Normal Neck Movements
Depending on how the measurements are done, between one-third and one-half of the neck’s forward/backward and rotational motions occur at the top two levels (between the base of the skull and C1, and between C1 and C2).2,3
However, most fusion surgeries in the cervical spine occur in one or more of the lower levels (C4 through C7). As such, a one- or two-level fusion in the lower cervical spine has little impact on the neck’s overall range of motion because the most mobile joints in the neck are not the ones fused.
Furthermore, most routine activities throughout the day only involve a fraction of the neck’s total range of motion. Even in rare cases where three or four levels of the lower cervical spine are fused, less than 25% of the neck’s overall mobility would be lost and this would not affect a person’s ability to perform most daily tasks.4 For any daily task that might be somewhat affected, adjustments could be made for getting them done. For example, instead of bending all the way down to tie shoes, the foot could be lifted further up.
Complexities of Measuring Cervical Range of Motion
There are many reasons that cervical range of motion measurements vary in the medical literature—both for healthy and fused cervical spines. Some examples include:
- Different measuring instruments. A wide variety of ways have been used to measure cervical range of motion, including inclinometers/goniometers, X-ray image measurements, and tape measures to name a few.1 Using a different measuring instrument will likely yield significantly different results, even when measuring the same person.
- Passive vs. active range of motion. Passive cervical range of motion is measured when someone else, such as a therapist, gently moves the head as far as it will go. Active range of motion, however, involves measuring the cervical spine’s mobility when a person moves the head on their own. Some studies indicate that fusion surgery has less impact on active range of motion, which is the range of motion that is actually experienced in everyday life.5
- Neck movements are complex. Cervical range of motion cannot simply be measured by adding up the sum of movements at each cervical level. Some movements are coupled, such as rotation that automatically happens when a person bends the head to the side.6 Plus, the movements do not necessarily follow a linear path. For example, the lower cervical spine is responsible for much of the initial movement that takes place when the head starts to flex forward, then movement transfers to the mid and upper cervical spine before finally transferring much of the final movements for maximum flexion back to the lower cervical spine.7
- Fusing one cervical segment alters the others. While fusing two vertebrae together stops motion at that cervical level, adjacent levels are likely to experience increased loads and increased mobility. Some of the motion lost at one fused level could be gained back at other levels.4
While the specifics of cervical range of motion can be complicated, most fusion surgery patients can safely ignore those details and focus on regaining enough neck mobility to return to a high quality of life.