Halo-gravity traction is a medical technique that uses a lightweight metal ring attached to the skull, connected to a weighted pulley system, to gradually straighten a severely curved or compressed spine. It is most commonly used in children with large spinal deformities before surgery, reducing the amount of correction the surgeon needs to achieve during the operation itself. The process typically takes weeks to months, and while it sounds intimidating, patients can move around, do physical therapy, and go about many daily activities while in traction.
How the Traction System Works
A surgeon attaches a metal ring, called a halo, around the patient’s head using 6 to 8 small pins secured into the outer layer of the skull. The ring is sized to sit about 2 centimeters larger than the circumference of the skull, and the pins are tightened according to age-specific guidelines. Once the halo is in place, it connects to a pulley system mounted above the patient. Weight is added to the pulley, pulling upward on the skull while gravity pulls the body downward. This opposing force slowly stretches the spine along its length.
The spine is surrounded by discs, ligaments, joint capsules, and muscles, all of which are somewhat elastic. When steady traction is applied over weeks, these tissues gradually lengthen and release, similar to how a slow, sustained stretch loosens tight connective tissue. This process corrects the curve in multiple directions: side to side, front to back, and rotationally. Because the correction happens slowly rather than all at once during surgery, the spinal cord and surrounding nerves have time to adapt, which significantly lowers the risk of neurological damage.
Who Needs It
Halo-gravity traction is reserved for severe spinal deformities, particularly scoliosis and kyphoscoliosis, where the curve is too large or too rigid to safely correct in a single surgery. It is used most often in pediatric patients. Candidates typically have curves that would put them at high risk for nerve injury or breathing complications if a surgeon tried to straighten the spine all at once during a fusion procedure. Patients with significantly reduced lung function are also strong candidates, since the traction can help expand the chest cavity before surgery.
What the Weight Schedule Looks Like
Traction starts light and builds gradually. A typical starting weight is around 4 kilograms (about 9 pounds). If the patient tolerates it without symptoms, the weight increases by roughly 2 kilograms per day until reaching a target of approximately 50% of the patient’s body weight, depending on individual tolerance. So a child weighing 40 kilograms might eventually have 20 kilograms of traction pulling on the halo.
The pulley system is set up on the patient’s bed, wheelchair, and walker, so traction can continue during different positions and activities throughout the day. Over the course of treatment, the spine progressively straightens. The average duration is roughly 125 days, though it ranges widely, from about 10 weeks to over 8 months, depending on the severity of the curve, the patient’s age, and how the spine responds.
Improvements in Breathing
One of the most important benefits beyond spinal correction is improved lung function. Severe spinal curves compress the chest, restricting how much the lungs can expand. As traction straightens the spine, the rib cage opens up. In one study of patients with an average lung capacity of just 42% of what’s normal for their age and size, traction improved that figure by about 7 percentage points on average. For the subset of patients whose lung function started below 40%, the improvement was even greater, averaging 9 percentage points. More than half of patients showed a measurable lung function response, and most of the improvement happened within the first phase of traction.
This matters because better lung function before surgery means the patient can tolerate anesthesia more safely and recover more smoothly afterward.
How Much Correction Traction Achieves
Traction alone does not fully correct the spinal curve. It serves as a first phase, reducing the curve enough that surgery can finish the job with less risk. In studies of severe kyphoscoliosis, halo-gravity traction alone corrected the main curve by roughly 19% on average. After the subsequent surgical fusion, total correction reached about 39%. The traction essentially does the safe, slow portion of the work so the surgeon can do less aggressive correction on the operating table.
Daily Life During Traction
Patients in halo-gravity traction are not confined to bed. The pulley system attaches to a wheelchair and a walker, allowing movement around the hospital or facility. Physical therapy continues throughout the traction period. Sleep happens with the traction connected to a bed-mounted frame. Daily pin care is an important part of the routine: patients or caregivers clean around each pin site with saline and antiseptic solutions to prevent infection. Patients are also taught to report any new symptoms, including pin pain, headaches, dizziness, or numbness in the arms.
Pin tension is checked at 48 hours, 72 hours after the halo is applied, and then weekly throughout traction. Neurological exams, including motor, sensory, and cranial nerve checks, are performed at least once daily by a physician.
Risks and Complications
Halo-gravity traction is generally well tolerated, but minor complications are common. In one study, nearly all patients experienced some neck pain during treatment, and about 37% reported back pain. Pin site infections and pin pain each occurred in roughly 26% of patients. About 26% experienced mild neurological symptoms such as temporary numbness or weakness in the arms. Vertigo and pin displacement were uncommon, affecting around 5% of patients.
When neurological symptoms do appear, the standard response is to reduce the traction weight by at least 2 kilograms and monitor closely. These symptoms are typically transient and resolve with the weight adjustment. Serious neurological complications are rare, which is one of the key advantages of the gradual approach: problems can be caught and reversed before they become permanent, unlike corrections made all at once during surgery.