A malunion fracture occurs when a broken bone heals, but the bone segments are in an incorrect anatomical position. This complication means the bone has achieved solid union, but the healing has resulted in a misalignment that can manifest as angulation, rotation, or shortening of the limb. Malunions can happen in any bone in the body and may affect both the cosmetic appearance and the function of the injured area.
How Malunion Differs from Other Healing Issues
The distinction between a malunion, a nonunion, and a delayed union lies in the status of the healing process. A delayed union is characterized by a fracture that is healing, but at a rate significantly slower than expected. This is considered a transitional state, where the bone may still progress to full recovery without further intervention, often simply requiring more time and continued immobilization.
In contrast, a nonunion represents a complete failure of the fracture to heal, and bony continuity is unlikely to be restored without further medical treatment. Clinically, a nonunion is often diagnosed when there is no progressive sign of healing on X-ray for a period of several months.
The unique aspect of a malunion is that the bone has successfully achieved a stable, solid union, but the resulting structure is anatomically incorrect. This faulty alignment, despite the stability of the union, leads to functional problems and potential long-term complications.
Why Fractures Heal Incorrectly
Fractures heal incorrectly due to several factors, often originating during the initial treatment phase. A primary cause is inadequate reduction, meaning the bone fragments were not properly aligned before immobilization began. Similarly, if the immobilization method is insufficient, such as a cast that is too loose or hardware that fails, the fragments can shift during the healing window.
Highly complex fracture patterns also increase the risk of malunion, particularly comminuted fractures, where the bone shatters into multiple pieces, or spiral fractures involving a twisting motion. These complex injuries make it inherently difficult to maintain perfect alignment throughout the lengthy healing process. Patient-related factors, such as failing to follow activity restrictions or delaying treatment after the injury, can also contribute to the misalignment.
Underlying biological conditions can further complicate the healing environment and predispose a patient to malunion. Traumatic injuries that compromise the blood supply to the fractured bone fragments can hinder proper remodeling and stability. Systemic issues like diabetes, obesity, or the presence of a bone infection, such as osteomyelitis, also negatively impact the body’s ability to create a stable, correctly aligned bone structure.
Recognizing the Signs of Malunion
A malunion often becomes apparent once the initial fracture pain has subsided, and the patient attempts to resume normal activities. The most obvious sign is a visible deformity of the limb, which may appear crooked, twisted, or noticeably shorter than the corresponding limb. This misalignment frequently results in persistent pain in the area, especially with weight-bearing activities.
Functional limitations are also common, including stiffness, a reduced range of motion in the joints adjacent to the healed fracture, and difficulty walking or using the limb. For instance, a malunion in a finger might cause it to “scissor” over an adjacent digit, severely limiting fine motor skills. Diagnosis relies on a thorough clinical examination, assessing the patient’s symptoms and functional deficits.
Malunion is confirmed using imaging studies, most commonly X-rays, to visualize the healed fracture and measure the degree of angulation, rotation, or shortening. For complex fractures, or when a detailed three-dimensional assessment is required, a Computed Tomography (CT) scan is often utilized. The diagnostic process aims to accurately characterize the deformity and determine its impact on the surrounding joints and soft tissues.
Options for Correcting Malunion
Treatment for a malunion depends on the severity of the deformity and its impact on the patient’s function and quality of life. For mild malunions that cause only minor functional deficits, non-operative management may be sufficient. This can involve targeted physical therapy to improve joint mobility and muscle strength, or the use of custom orthotics, such as shoe inserts, to compensate for slight limb length discrepancies.
Surgical intervention is typically necessary when the malunion results in significant pain, functional limitation, or a high risk of developing future joint degeneration. The standard procedure for correction is an osteotomy, which involves surgically cutting the healed bone at or near the site of the original fracture. This controlled break allows the surgeon to realign the bone segments into the correct anatomical position.
Following the realignment, the bone is stabilized using internal fixation hardware to hold the correction securely while the bone heals again. In cases where the correction creates a gap in the bone, a bone graft may be used to fill the space and stimulate new bone growth. The goal of this complex procedure is to restore the limb’s pre-injury mechanical axis, thereby improving function and reducing the strain on adjacent joints.