Tibial hemimelia is an uncommon congenital limb deficiency that causes babies to lack either part or all of their larger tibial bone. Type 4 is unique because patients maintain a knee joint, unlike other severe cases. This condition prevents children from reaching normal posture during walking and movement.
The tibia of Type 4 tibial hemimelia patients is either partly absent or partly developed, yet their fibula leg bone maintains normal size. An equino-varus deformity affecting the foot occurs frequently in this condition, causing the foot to be positioned towards the inside and downward. The medical approach for this condition concentrates on helping the child regain leg movement alongside correcting alignment to achieve regular walking patterns.
This article provides information about Type 4 tibial hemimelia, including its causes, symptoms, and surgical treatments, which we strongly advise you to read thoroughly.
What Is Type 4A Tibial Hemimelia?
In patients with Type 4A tibial hemimelia, both the knee joint functions properly, and the tibia exhibits either missing or abnormal structure. The fibula bone of the lower leg typically exceeds normal length while existing in an improper position. Due to the absence of a lower tibial segment near the ankle, the ankles will develop abnormally instead of forming a normal joint structure—The absence of a normal distal tibia leads to severe foot and mobility issues.
Causes of Type 4A Tibial Hemimelia
Tibial hemimelia is a congenital condition that develops within the foetus. Scientists have not yet discovered the origin of this condition, but genetics and environmental factors of pregnancy might contribute to its development. A genetic background of this condition rarely exists, as most patients do not inherit it from their parents.
Common Symptoms of Type 4A Tibial Hemimelia
Shortened Leg: The affected leg is noticeably shorter than the other.
Foot Deformity: In case of leg deformities, the foot is turned downward and inward, resulting in a severe equino-varus condition.
Knee Joint Present: Unlike more severe types, the knee joint is present and functional.
Abnormal Fibula Position: The fibula is longer than usual and not in its correct position.
Possible Knee Instability: Some children may have weak or missing ligaments around the knee, leading to instability.
Challenges Due to the Condition
- Walking is difficult because of the missing tibia and abnormal ankle structure.
- The foot cannot bear weight properly due to its deformed position.
- The leg length difference causes imbalance while standing or moving.
Treatment for Type 4A Tibial Hemimelia
The surgical tibial hemimelia treatment for Type 4A tibial hemimelia requires multiple stages. Doctors plan to use the fibula to build a functional limb that enables walking after tibial removal.
How Is Surgery Performed?
The treatment is divided into two major stages:
Stage 1: Preparing the Fibula for Transport
- Achilles Tendon Release
Doctors cut the Achilles tendon for anatomized correction of foot deformities.
- Temporary Wires in the Fibula
Two wires are inserted into the fibula to prevent it from breaking during the next steps.
These wires hold the fibula in place while it is moved downward to replace the missing tibia.
- External Fixator Placement
A circular external fixator (a metal frame) is applied to the leg.
It consists of rings attached to the femur (thigh bone) and the tibia to provide stability.
The knee is locked in a straight position using a special wire.
- Gradual Distraction (Bone Movement)
The fibula is slowly moved down over 6 to 12 weeks.
This process corrects the deformity and brings the fibula closer to the tibia.
The wires inside the fibula prevent damage while it is being moved.
Stage 2: Correcting the Foot Position
- Realigning the Foot
A second round of gradual adjustments is made to correct the foot deformity.
The foot is repositioned to be flat (plantigrade) and aligned properly with the leg.
- Stabilizing the Fibula
The fibula is held in its new position while the foot is corrected.
The goal is to place the fibula in a position where it can support the body’s weight like a normal tibia.
Final Surgery: Fusion and Bone Transfer
Once the fibula is in the correct position, a final surgery is performed:
- Ankle Fusion Surgery
The lower part of the fibula is fused with the talus (ankle bone).
This creates a stable connection between the leg and the foot.
- Fibula Transfer to the Tibia
A portion of the fibula is moved to the tibia’s location and fixed using plates and screws.
This process creates a strong bone structure that functions like a tibia.
- External Fixator and Healing Process
The external fixator remains in place for about 3 months to ensure proper healing.
A final wire is inserted to compress the fusion site for extra stability.
Post-Surgery Recovery and Rehabilitation
Healing Time: The bones take around 3 months to fuse completely.
Physical Therapy: The child undergoes cp child physiotherapy to restore knee movement.
Leg Lengthening (If Needed): Additional procedures can be performed later for limb lengthening.
Type 4B: A Slightly Different Approach
In Type 4B, the upper part of the tibia is present, but its growth plate is missing. The main difference in treatment is that:
- The small tibial bone is fixed to prevent it from moving downward during fibula transport.
- The fibula can be moved below the tibial epiphysis, preserving growth potential.
- Special wires or bone growth stimulators (BMP2) may be used if the tibia is too weak.
Conclusion
Type 4 tibial hemimelia is challenging, but modern surgical techniques offer effective solutions. The doctor achieves a stable, functional leg by replacing missing tibia bones using fibula bone transfers. The procedure demands several surgeries with extensive postoperative follow-up, yet it enables children to regain their movement and improve their overall quality of life. The correct medical care allows affected children to develop walking skills and lead active lives.
