Pseudarthrosis is a medical term derived from Greek, meaning “false joint,” describing a condition where a fractured bone fails to heal properly, resulting in a nonunion. When a bone does not achieve complete fusion within the expected healing time, typically six to nine months, the site of the break remains mobile. Instead of solid bone bridging the gap, a fibrous or cartilaginous tissue forms, which mimics the structure and movement of an actual joint. This can occur after a simple fracture or following a surgery intended to fuse bones, such as a spinal fusion procedure.
The Failure of Bone Fusion
Bone healing requires a complex biological environment, and nonunion occurs when factors disrupt this process. One significant mechanism for failure is inadequate blood supply, or poor vascularity, at the fracture site. Damage to surrounding blood vessels during the initial injury limits the oxygen and nutrients needed for bone cells to regenerate, often leading to the formation of soft, non-bony tissue instead of a solid union.
Mechanical instability, where excessive motion at the fracture site, prevents cellular structures from forming a sturdy bone matrix. Inadequate stabilization, whether through bracing or internal hardware, allows constant micromovement that irritates the forming tissue, often developing into a non-healing fibrous capsule. Infection at the site of the injury or surgery also introduces inflammation and tissue destruction, actively interfering with the body’s attempts to bridge the gap.
Numerous patient-related factors also increase the risk of developing a false joint. Smoking is a well-documented hindrance to bone healing because nicotine restricts blood flow, impairing the delivery of healing cells and oxygen. Systemic diseases such as diabetes, which compromise circulation and immune response, can also slow or stop the fusion process.
The use of certain medications, including non-steroidal anti-inflammatory drugs (NSAIDs) shortly after a fracture or surgery, may negatively affect the initial stages of bone healing. While most cases of pseudarthrosis are acquired following an injury, a rare form known as congenital pseudarthrosis exists, which is present from birth. This congenital form is often seen in the tibia and is sometimes associated with the genetic disorder neurofibromatosis type 1.
Recognizing the Signs and Confirmation
Patients with pseudarthrosis typically experience persistent pain long after the expected healing period has passed. This chronic discomfort often intensifies with physical activity or weight-bearing, as the unstable site is subjected to mechanical stress. The nonunion site may also exhibit instability or abnormal motion, sometimes described as a clicking or grinding sensation, along with tenderness and swelling.
Because the symptoms of a false joint can sometimes be subtle, medical professionals rely on diagnostic imaging to confirm the failure of fusion. The initial step involves standard X-rays, which may reveal a clear gap between the bone fragments or a lack of bone bridging.
A Computed Tomography (CT) scan is frequently used for definitive confirmation because it provides detailed, cross-sectional images of the bone structure. A CT scan accurately shows the presence of fibrous tissue or a fluid-filled gap, confirming the lack of solid bone union. In certain cases, especially in the spine, dynamic X-rays are taken while the patient moves to visually demonstrate abnormal motion at the nonunion site.
Interventions to Achieve Healing
Treatment for pseudarthrosis focuses on creating a favorable biological and mechanical environment to stimulate new bone growth and achieve successful fusion. The gold standard for treatment is surgical revision, which aims to remove the non-healing tissue and stabilize the bone segments. This procedure often involves removing any previously implanted hardware that may have loosened or failed.
During revision surgery, the surgeon performs a debridement, excising the fibrous tissue, dead bone, and sclerotic bone ends that are biologically inert. This exposes fresh, bleeding bone surfaces receptive to healing. Following debridement, the segments are compressed and held together with new, rigid internal fixation, such as plates, screws, or intramedullary rods, to eliminate motion.
Biological augmentation is often performed simultaneously to introduce components necessary for bone regeneration. The most effective method is the application of an autograft, which is bone tissue harvested from the patient’s own body, typically from the pelvis. Autograft bone is considered the gold standard because it provides all three elements needed for fusion: living bone cells (osteogenic), growth factors (osteoinductive), and a structural scaffold (osteoconductive).
In situations where a large amount of bone is needed or harvesting an autograft is not possible, an allograft—bone from a donor—may be used, though it lacks the patient’s living bone cells. Following surgery, non-surgical adjuncts may be introduced to further encourage bone healing. These external methods include electrical or ultrasonic bone stimulation, which delivers energy to the nonunion site to activate the natural regenerative processes of the bone cells.