A broken arm that heals in an unsatisfactory position is medically known as a malunion. This condition occurs when the bone fragments fuse together, but the overall structure of the limb is left crooked or misaligned. While many fractures heal without issue, a malunion is a recognized complication that affects both the appearance and the function of the arm.
Understanding Malunion: Why Fractures Heal Crookedly
Malunion is defined by a bone healing with an abnormal angle, twist, or length compared to its original anatomy. The primary cause often relates to the complexity of the initial injury, such as a comminuted fracture where the bone breaks into multiple pieces. Severe injuries are inherently difficult to reduce and stabilize perfectly, increasing the risk of misalignment.
A common mechanism for malunion is inadequate initial fracture reduction, meaning the broken bone ends were not set correctly. Even if the bones are initially aligned, instability during healing can allow the fragments to shift. This instability can result from a loose cast, insufficient surgical fixation, or the patient moving the limb too much before solid bone callus forms.
Visual Signs of a Malunited Arm
The most immediate sign of a malunion is a visible deformity when comparing the affected arm to the uninjured one. This difference typically falls into three categories: angulation, rotation, and shortening.
Angulation
Angulation describes a noticeable bend or bowing in the arm, often creating a palpable lump at the fracture site. This is a clear deviation from the limb’s normal straight axis.
Rotation
Rotational malunion is a subtle but functionally significant deformity where the bone heals with a twist along its long axis. This twist causes the lower parts of the arm, such as the wrist or elbow, to point in an incorrect direction. For example, the palm might face inward when the arm hangs naturally.
Shortening
Limb shortening occurs when the affected arm is measurably shorter than the healthy arm. This discrepancy results from the bone ends overlapping during healing, which compresses the overall length of the limb.
Functional Limitations and Secondary Symptoms
A malunited arm severely limits functional capabilities and generates chronic discomfort. The abnormal shape of the healed bone directly impacts joint mechanics above and below the fracture site, leading to a reduced range of motion. Patients often experience difficulty with forearm rotation, necessary for actions like turning a doorknob.
The misalignment causes chronic pain because it forces joints, particularly the elbow and wrist, to bear weight unevenly. This altered biomechanics leads to premature wear on the joint cartilage, increasing the risk of developing early-onset arthritis.
The crooked bone position can physically impinge upon adjacent soft tissues. If angulation or rotation affects the space through which nerves travel, it can lead to secondary symptoms such as tingling, numbness, or muscle weakness in the hand or fingers.
Options for Correcting a Crookedly Healed Arm
The decision to correct a malunited arm depends on the severity of the deformity and the degree of functional impairment. For minor malunions that do not limit movement or cause persistent pain, non-surgical management is often recommended. This approach involves focused physical therapy to maximize the existing range of motion and pain management strategies.
When the malunion results in substantial functional limitations or severe cosmetic deformity, surgical intervention is the standard treatment. The most common procedure is a corrective osteotomy, which involves surgically re-breaking the healed bone at the site of the deformity. The surgeon then realigns the bone fragments to restore the arm’s correct anatomical position, often using the uninjured arm as a template.
Once realigned, the bone is fixed in place with plates, screws, or other internal hardware to ensure stability while it heals straight. Modern techniques may use pre-operative three-dimensional imaging and patient-specific cutting guides to achieve precise corrections. This procedure aims to restore both the appearance of the limb and its normal function.