Chiropractic neck adjustment, formally known as cervical spine manipulation, is a common concern for individuals considering this treatment. This procedure involves a practitioner applying a specific, controlled force to the joints of the neck. The primary goal is to improve the movement and function of the spinal joints, typically to address pain and stiffness. This article explores the mechanics of the adjustment, examines the evidence regarding adverse events, and details the measures professionals take to reduce potential risks.
How Cervical Adjustments Work
Chiropractic neck adjustments are typically performed using a technique known as High-Velocity Low-Amplitude (HVLA) thrust. This involves the clinician applying a quick, shallow thrust to a specific joint in the cervical spine. The force is delivered rapidly but only moves the joint a short distance, staying within the joint’s anatomical limit.
The mechanical action is designed to restore normal motion to a joint that has become restricted or “fixed.” The application of the HVLA thrust can lead to an audible popping sound, which is called cavitation. This sound occurs when a sudden pressure change in the joint fluid causes tiny gas bubbles, primarily nitrogen and carbon dioxide, to be released.
This physical intervention is thought to provide therapeutic benefits through several means. Biomechanically, the adjustment can increase the joint’s range of motion and reduce muscular tension surrounding the joint. The effects also involve a neurological component, as the rapid stimulus can influence the nervous system’s perception of pain and muscle tone.
Understanding the Rare Severe Risks
The most serious, though highly uncommon, risk associated with cervical manipulation is a vertebral artery dissection (VAD). The vertebral arteries run through the bony tunnels of the cervical vertebrae and supply blood to the brainstem and cerebellum. A dissection occurs when a tear forms in the inner lining of the artery wall.
This tear allows blood to enter the wall, which can lead to the formation of a blood clot. The clot may either block the artery at the site of injury or break free and travel to the brain, causing an ischemic stroke. Symptoms of a dissection can include severe, sudden onset neck pain or headache, often described as the “worst ever,” and may precede a stroke by hours or days.
While the possibility of VAD following a neck adjustment prompts public concern, VAD can occur spontaneously or follow common, non-chiropractic activities like coughing, sudden head movements, or minor trauma. Minor and transient side effects are significantly more common after a cervical adjustment. These mild reactions often include localized stiffness, temporary soreness, or a headache, which typically resolve within 24 to 48 hours.
Patient Screening and Risk Reduction
A thorough patient history and physical examination are the primary tools used to identify individuals at elevated risk of an adverse event. Chiropractors must inquire about recent trauma, pre-existing vascular conditions, or symptoms like unusual dizziness or vision changes. These symptoms could be subtle indicators of a pre-existing arterial dissection, making the patient unsuitable for certain procedures.
The physical exam includes specific neurological and vascular testing to look for signs of compromised blood flow or nerve function. Conditions like severe osteoporosis, certain types of spinal cancer, or a known increased risk of stroke are considered contraindications for cervical adjustments. These identified risks would lead the clinician to modify the treatment plan or refer the patient to another specialist.
Before any procedure, the concept of informed consent requires the practitioner to discuss the potential risks and benefits clearly with the patient. This discussion is designed to ensure the patient understands the rare possibility of serious adverse events, such as VAD and stroke, before choosing to proceed with the treatment. The goal of this careful screening process is to reduce the risk of an iatrogenic event by avoiding manipulation in an already compromised artery.
What the Research Says About Safety Rates
Scientific literature consistently suggests that the risk of a serious adverse event, such as stroke following a cervical adjustment, is extremely low. Estimates of this rare complication vary but are often cited as being on the order of greater than one in a million manipulations. The low incidence rate makes it challenging for researchers to definitively establish a precise risk for a healthy person.
The most significant finding in large-scale population studies concerns the distinction between association and causality. Studies have shown a statistical association between a visit to a chiropractor or a primary care physician and a subsequent VAD diagnosis. However, researchers propose that this association is likely due to patients with an already developing arterial dissection seeking care for the resulting neck pain and headache that are early symptoms of the condition.
This means the adjustment is often temporal to the stroke, not the direct cause of the arterial tear. A systematic review and meta-analysis found a small statistical association between chiropractic care and cervical artery dissection, but ultimately concluded there is no convincing evidence to support a causal link. The evidence indicates that while the risk is real and must be discussed, the vast majority of patients experience no serious complications.