Pseudarthrosis (False Joint)

What is pseudarthrosis?

Normally, a broken bone or a spinal fusion heals by bridging the gap with new bone. In pseudarthrosis, the gap fills instead with fibrous tissue or cartilage. Sometimes a fluid-filled space with a lining forms, resembling a real joint capsule, which is where the name comes from.

The term overlaps with nonunion. Many surgeons use the two interchangeably for fractures, while "pseudarthrosis" is the standard term for failed spinal fusion and for the congenital form. For a detailed look at fractures that fail to heal, see nonunion.

Types of pseudarthrosis

Fracture pseudarthrosis

A fracture is usually considered to have failed to heal when there are no signs of progress on X-rays for 3 months, or no healing by 6 to 9 months.

Risk factors:

• Unstable fixation that lets the bone ends move
• Poor blood supply, as in the scaphoid in the wrist and the lower tibia
• Open fractures with bone loss or soft tissue damage
• Infection of the fracture site (osteomyelitis)
• Smoking and nicotine, which slow bone healing significantly
• Diabetes, poor nutrition, low vitamin D, obesity and older age
• Some medicines, such as long-term steroids and possibly NSAIDs early in healing

Hypertrophic pseudarthrosis has plenty of bone formation but too much movement ("elephant's foot" appearance). It usually heals once the bone is held rigidly. Atrophic pseudarthrosis has little biological activity and needs bone grafting.

Spinal fusion pseudarthrosis

Spinal fusion joins two or more vertebrae with bone graft, often held by screws and rods while fusion takes place. A fusion fails in a minority of patients, with rates varying widely with the number of levels, technique and patient factors. Smoking is one of the strongest risk factors.

Symptoms:

• Back or neck pain that never improved, or that returned after an initial period of relief
• Pain worse with activity
• Leg or arm symptoms from loosening hardware
• Sometimes no symptoms at all, found on a scan

It is one cause of failed back surgery syndrome.

Congenital pseudarthrosis of the tibia

This rare condition affects about 1 in 140,000 to 250,000 births. More than half of affected children have NF1.

• It begins as an outward-and-forward bowing of the lower leg in infancy.
• The weak area of bone then breaks, often with minor trauma, and fails to heal, forming a false joint.
• It is one of the hardest problems in children's orthopedics. Treatment uses bracing to prevent fracture before it occurs, and surgery with rods, bone grafts, sometimes bone from the other leg, or circular external frames once a fracture happens. Several operations may be needed, and a few children ultimately benefit from amputation and a prosthesis for the best function.

Any bowing of the lower leg in a baby, especially with café-au-lait spots, should be seen by a pediatric orthopedic surgeon.

Diagnosis

• History and examination: pain on stressing the site, abnormal motion, deformity
• X-rays: a persistent gap, rounded or sclerotic (dense) bone ends, broken or loose screws, a lucent halo around screws
• CT scan: the most reliable way to see whether bone has bridged, especially in the spine
• Flexion-extension X-rays: movement between fused vertebrae suggests a failed fusion
• Infection tests: blood tests (white count, CRP, ESR), and biopsy or cultures at surgery
• Metabolic tests: vitamin D, calcium, thyroid and blood sugar when healing is unexpectedly poor

Treatment

Non-surgical options

• Stopping smoking and nicotine
• Correcting vitamin D deficiency, nutrition and diabetes control
• Bracing or reduced loading
• Bone growth stimulators (low-intensity pulsed ultrasound or electromagnetic devices) for some fracture nonunions and as an add-on after spinal revision

Surgery

• Revision fixation: a stronger plate, a nail inside the bone or new spinal instrumentation to stop movement
• Bone grafting: the patient's own bone, usually from the pelvis, to stimulate healing, sometimes with substitutes or growth proteins
• Removing infected bone and treating with antibiotics before reconstruction
• Revision spinal fusion, often using a different approach, such as adding fusion from the front of the spine

Success rates after revision for fracture nonunion are generally high. Revision spinal fusion success is lower and depends on correcting the cause.

Frequently asked questions

What is the difference between pseudarthrosis and nonunion?

They overlap. Nonunion means a fracture has failed to heal. Pseudarthrosis means a false joint has formed at that site, sometimes with a lining like a real joint. Many doctors use the words interchangeably for fractures. Pseudarthrosis is also the usual term for a failed spinal fusion and for the congenital form.

What are the symptoms of pseudarthrosis after spinal fusion?

The most common symptom is back or neck pain that never improved after surgery, or that returned months later. Pain is often worse with activity. Some people develop leg or arm pain if screws loosen. Others have no symptoms. A CT scan is the best test to confirm it.

Can pseudarthrosis heal on its own?

Rarely. Once a false joint has formed, the body usually cannot bridge the gap without help. Stopping smoking, correcting vitamin D and stabilizing the bone can help some cases, but most need surgery with stronger fixation and bone graft.

What is congenital pseudarthrosis of the tibia?

It is a rare condition in which a weak, bowed shinbone breaks in early childhood and fails to heal, forming a false joint. More than half of affected children have neurofibromatosis type 1. It needs specialist pediatric orthopedic care, often including bracing and several operations.

Does smoking cause pseudarthrosis?

Smoking is one of the strongest risk factors. Nicotine and other chemicals in smoke narrow blood vessels and impair bone-forming cells, increasing the risk of fracture nonunion and failed spinal fusion. Most surgeons advise stopping all nicotine, including vapes and patches, before and after surgery.