A cervical fusion, or arthrodesis, stabilizes the neck by permanently joining two or more vertebrae into a single, solid bone mass. The procedure involves removing the intervertebral disc and inserting a bone graft or spacer, often reinforced with hardware, to eliminate motion at that segment. The goal is to stop painful movement and allow the bone to grow across the space. Fusion failure, known as pseudarthrosis or a “false joint,” occurs when the bones fail to fully unite. This lack of a bony bridge allows for micro-motion at the surgical site, undermining stability and often requiring further medical evaluation.
Persistent Pain and Stiffness After Recovery
The most common sign of fusion failure is the return or persistence of neck pain after the initial post-operative healing period. While patients usually feel immediate relief, pain that returns or worsens after three to six months may suggest a non-union. This discomfort is often described as severe, centralized axial neck pain, meaning it is centered in the neck rather than radiating down the arm.
This localized pain is frequently exacerbated by neck movement because the pseudarthrosis site cannot bear the load effectively. The abnormal movement leads to inflammation and muscle spasms in the surrounding soft tissues, contributing to chronic stiffness and a deep, aching sensation. Patients may also report mechanical instability, such as the neck “giving way” or a grinding sensation when moving their head.
The recurrence of severe neck pain, mirroring the pre-operative condition, strongly indicates a potential problem. The micro-motion at the failed fusion site irritates local nerves and muscles, creating a cycle of pain that often does not respond well to conservative treatments. This persistent discomfort is usually the first noticeable symptom prompting re-evaluation.
Urgent Neurological Symptoms
While persistent neck pain is the most frequent symptom, the development of new or worsening neurological symptoms indicates a more serious issue requiring immediate attention. These symptoms arise when instability from the non-union irritates or compresses the spinal cord or nerve roots.
A significant sign is the onset or return of radiculopathy, involving pain, tingling, numbness, or weakness that radiates down one or both arms and into the hands. Abnormal movement or loosening hardware can narrow the space around the nerves, directly impinging upon neural structures. Loss of fine motor skills or dexterity, such as difficulty buttoning a shirt, is another concerning symptom.
More severe neurological deficits, such as a change in gait, problems with balance, or an unsteady way of walking, signal irritation or compression of the spinal cord. In rare but urgent cases, the sudden onset of bladder or bowel dysfunction can indicate significant spinal cord compromise. Any progressive neurological changes suggest active damage to neural tissue and require an emergency medical evaluation.
How Doctors Confirm Fusion Failure
Confirming pseudarthrosis requires a methodical approach using clinical examination and specialized diagnostic imaging, as symptoms alone are insufficient for a definitive diagnosis. The physician conducts a physical examination to check reflexes, muscle strength, and sensation, looking for objective signs of nerve root or spinal cord involvement. Understanding the pain pattern and its relationship to movement helps localize the suspected area of non-union.
Initial imaging typically involves plain X-rays, but flexion and extension views are often employed to check for abnormal motion. These dynamic X-rays capture the neck while the patient gently bends forward and backward, allowing the doctor to visualize if movement, such as abnormal translation or angulation, is still occurring at the intended fusion site. Hardware loosening or breakage can also be detected on these films.
The most definitive diagnostic tool for confirming bony fusion is the Computed Tomography (CT) scan. A CT scan provides high-resolution images superior to X-rays for visualizing bone formation and bridging. In pseudarthrosis, the CT scan shows a clear gap or lucency—a dark space where bone should be—between the vertebrae, rather than solid bone growth. Magnetic Resonance Imaging (MRI) may also be used to assess soft tissue structures, such as the spinal cord and nerve roots, to determine if they are being compressed due to instability.
Treatment Options for Non-Union
Once fusion failure is confirmed, the treatment depends on the severity of the patient’s symptoms and the degree of instability. For patients with mild symptoms or those who are not surgical candidates, non-surgical management is the initial approach. This involves focused physical therapy to strengthen neck muscles, targeted pain management, and sometimes the use of external bone growth stimulators.
If the patient experiences persistent, debilitating pain or progressive neurological decline, revision surgery is generally recommended. This procedure involves re-operating on the failed segment to remove failed hardware and fibrous tissue, prepare the bony surfaces, and attempt a second fusion. The surgeon often uses new bone graft material, sometimes enhanced with biological agents, and may use different fixation hardware to ensure greater stability.
Revision procedures can involve accessing the spine from the front (anterior), the back (posterior), or both, depending on the non-union’s location. In specialized cases, a surgeon may replace the failed fusion construct with a cervical disc replacement device to restore some motion and avoid another fusion. The overall aim of revision treatment is to achieve a solid bony union and eliminate the instability causing the symptoms.