Malunion (Bone Healed in a Poor Position)

How malunion happens

A broken bone heals by forming new bone (callus) across the break over 6 to 12 weeks or more. If the bone fragments are not held in the right position during that time, they heal where they are. Causes include:

• fracture displacement that was not fully corrected
• loss of position in a cast as swelling goes down and the cast loosens
• unstable fractures treated without surgery
• early weight-bearing or removal of a splint
• fixation failure after surgery
• untreated fractures, for example when a break was not recognized or care was delayed
• growth plate injuries in children, which can cause progressive deformity as the child grows

Malunion vs nonunion vs delayed union

See nonunion for bones that fail to heal.

Types of malunion

• Angular: the bone heals bent
• Rotational: the bone is twisted, often noticed as fingers that cross or a foot that points in or out
• Shortening: fragments overlap, making a limb shorter
• Translational: fragments are shifted sideways
• Intra-articular: the joint surface heals with a step or gap, which raises the risk of post-traumatic arthritis

Common sites and their effects

• Wrist (distal radius): the most common malunion. Causes a visible bump, reduced wrist and forearm rotation, grip weakness, and pain on the little finger side. See wrist fracture.
• Fingers and metacarpals: rotation causes fingers to overlap when making a fist ("scissoring"), interfering with grip.
• Forearm: limits turning the palm up and down.
• Collarbone (clavicle): shortening can affect shoulder mechanics and appearance.
• Tibia and femur: angulation or rotation alters how weight passes through the knee and ankle, causing pain and early arthritis. Shortening causes a limp and back or hip pain.
• Ankle: a small shift of the ankle bones can greatly increase joint wear.
• Elbow in children: "gunstock" deformity after a supracondylar fracture.

Symptoms

• visible deformity or bump
• pain with use, or at rest in some cases
• stiffness and reduced range of motion
• weakness and reduced grip
• uneven leg length and limping
• clicking or catching in a nearby joint
• pain in other joints from altered mechanics

Many mild malunions cause no symptoms, especially in older or less active people and in the upper limb.

Diagnosis

• Examination: alignment, rotation (checking finger cascade in a fist), movement, strength, and comparison with the other side
• X-rays of both sides for comparison
• CT scan to measure rotation and joint surface steps, and for 3D planning
• Long-leg X-rays to measure leg alignment and length

Treatment

Non-surgical management

Appropriate when symptoms are mild or the person's activity needs are limited:

• physical or hand therapy to improve movement and strength
• pain relief: acetaminophen (paracetamol) or NSAIDs, following the label dose
• shoe lifts for small leg length differences
• braces or splints for support
• in children, observation, because growing bones can remodel and correct some angulation, especially near growth plates and in the direction of joint motion. Rotation does not remodel well.

Surgery

• Corrective osteotomy: the bone is cut at or near the malunion, realigned, and fixed with plates, screws or rods. Bone graft may be added. Computer planning and custom guides improve accuracy.
• Gradual correction: an external frame adjusts alignment and length slowly over weeks, useful for large deformities and leg length differences.
• Joint procedures: for an arthritic joint after an intra-articular malunion, options include joint fusion or replacement.
• Ulnar shortening or other procedures for wrist malunions causing pain on the little finger side.

Recovery after osteotomy is similar to healing a new fracture, with weeks to months of protection and rehabilitation.

Prevention

• follow-up X-rays in the first 1 to 3 weeks after a fracture is set, to catch slipping early
• keep casts and splints on as directed and report looseness
• follow weight-bearing instructions
• seek care promptly for suspected fractures

Frequently asked questions

What is a malunion?

A malunion is a broken bone that has healed in an incorrect position, such as bent, twisted or shortened. It can cause deformity, pain, weakness or limited movement, though mild malunions often cause no problems.

Can a malunion be fixed?

Yes. If a malunion causes significant symptoms, a surgeon can cut the bone and realign it (corrective osteotomy), fixing it with plates, screws or rods. Mild malunions are often managed with therapy instead.

What causes a bone to heal crooked?

A bone heals crooked when fragments are not held in the correct position while healing. This happens with displaced or unstable fractures, slipping in a cast, early weight-bearing, failed fixation, or fractures that were not treated.

What is the difference between malunion and nonunion?

In a malunion the bone has healed, but in the wrong position. In a nonunion the bone has not healed at all and the break remains mobile. Both may need surgery, but for different reasons.

Will a malunion in a child correct itself?

Partly, sometimes. Children's bones can remodel angulation near growth plates, especially in the same plane as joint movement and in younger children. Rotational deformities and fractures through the joint surface do not correct well and may need treatment.