The human body possesses a remarkable ability to repair itself, clearly demonstrated in the healing of a broken bone. Bone healing is a sophisticated biological cascade that typically moves through phases of inflammation, callus formation, and a long phase of remodeling to restore the bone’s original strength and structure. While most fractures successfully complete this regenerative journey, mechanical or biological disruptions can interrupt the process, leading to a failure of the bone to heal correctly. This failure results in chronic pain, functional impairment, and a reduction in the quality of life, often requiring specialized medical intervention.
Defining Failed Fracture Healing
When a fracture does not mend as anticipated, it typically results in one of two distinct complications: nonunion or malunion. Nonunion occurs when the bone healing process completely stalls, and the fracture site fails to bridge with solid bone after a sufficient period, generally considered six to nine months past the expected healing time. This leaves the two bone fragments unattached or only weakly connected by fibrous tissue.
Malunion, by contrast, is a failure to heal in the correct anatomical alignment, not a failure of the bone to unite. The bone successfully unites, but it does so in an improper position, resulting in a visible deformity, limb rotation, or noticeable shortening. While nonunion represents a lack of structural integrity, malunion presents a problem of mechanical dysfunction and altered biomechanics due to the incorrect positioning of the healed bone.
Recognizing the Signs of Improper Healing
The first indication that a fracture is not healing correctly is the persistence of symptoms long after the acute injury phase has passed, including persistent pain, tenderness, and swelling. In cases of nonunion, there may be instability or abnormal movement at the fracture site, sometimes noticeable as a grinding sensation upon attempted weight-bearing or motion.
A malunion may become apparent through a visible deformity, such as a limb that appears bent, twisted, or shortened compared to the uninjured side. Medical professionals confirm these suspicions using diagnostic imaging. Standard X-rays can reveal a persistent fracture line or the misalignment characteristic of a malunion, while CT scans or MRI may be used for a more detailed three-dimensional view.
Factors That Hinder Bone Repair
The biological process of bone repair is sensitive to local and systemic disruptions that increase the risk of failed healing.
Local Factors
Locally, a primary factor is inadequate blood supply (vascularity) to the fracture site, as blood flow delivers the oxygen and nutrients needed for bone-forming cells. Severe soft tissue damage can compromise this blood supply, increasing the likelihood of an atrophic nonunion, characterized by a lack of new bone growth.
Infection, particularly osteomyelitis, is another local obstacle, as pathogenic organisms disrupt the normal healing cascade and promote fibrous tissue formation instead of solid bone. Excessive movement or instability at the fracture gap, often due to inadequate immobilization or failure of surgical hardware, can mechanically prevent the bone ends from bridging. This insufficient stability often results in a hypertrophic nonunion, where callus forms but fails to span the gap.
Systemic Factors
Systemic factors related to the patient’s overall health also play a large role in the body’s ability to heal a fracture. Nicotine from smoking is a powerful vasoconstrictor that significantly reduces blood flow to the injury site and impairs the function of bone-forming cells. Underlying health conditions such as poorly controlled diabetes mellitus can hinder healing by negatively affecting microcirculation and the function of osteoblasts. Certain medications, including long-term use of corticosteroids and some nonsteroidal anti-inflammatory drugs (NSAIDs), are also known to negatively impact callus formation and mineralization.
Treatment Options for Nonunion and Malunion
The treatment strategy for failed fracture healing depends on whether the patient presents with a nonunion or a malunion.
Treating Nonunion
For nonunions, the goal is to restart the stalled biological process, often requiring surgical intervention to create a fresh environment for healing. Surgery typically involves debridement to remove dead or infected tissue, followed by a revision of the internal fixation hardware to ensure optimal stability.
To stimulate new bone growth, bone grafting is frequently employed, using either an autograft (bone tissue harvested from the patient’s own body) or an allograft from a donor. The graft provides a scaffold and sources of growth factors to bridge the gap. Non-surgical options, such as electrical or low-intensity pulsed ultrasound stimulation devices, may also be prescribed to encourage cellular activity.
Treating Malunion
Treating a malunion requires a different approach focused on restoring the correct anatomical shape and function of the limb. This correction is typically achieved through a procedure called a corrective osteotomy, where the bone is surgically cut and realigned to its proper position. After the bone is reset, it is held securely in place using internal fixation, such as plates, screws, or rods, allowing the corrected break to heal in the intended alignment. Both corrective procedures necessitate an extended recovery period with careful monitoring and physical therapy.