Tibial Hemimelia

Tibial hemimelia also belongs to the congenital longitudinal defects. Characteristic is here the complete absence of the shin bone (tibia) or a part of the shin bone.

Tibial hypoplasia: incomplete development of the tibia

Tibial aplasia: complete absence of the tibia

The cause for tibial hemimelia also remains unclear to date. Other than for the fibular defect, there are numerous inherited cases of the deformity. The hereditary form is frequently accompanied by further malformations. Therefore, genetic testing for further family planning is recommended.

Classification

Among the different classifications of the tibial defect, the one by Kalamchi and Dawe (1985) proves to be understandable and simple in everyday use. Aside from the radiological characteristics, also functional characteristics (knee flexion contracture and quadriceps function) are considered.

Actual therapy planning, however, frequently has to fall back on a substantially more complex classification (MRI!).

Classification of the congenital tibial aplasia after Kalamchi and Dawe 1985:

Type
Radiological characteristics
Knee flexion contracture
Quadriceps activity
I
>45°
none
II
25°- 45°
reduced
III
none
normal

Type I
Type II
Type III

 

The decision which therapeutic procedure should be undertaken depends in particular on the function of the knee with its extensor system, an existing flexion contracture and knee instability.

Clinical picture

Just as in other longitudinal defects of the extremities, tibial hemimelia is accompanied by other malformations of the leg. Frequently, there are additional deformities of the upper extremities. The foot deformity depends on the severity of the shin bone defect: usually, the affected foot is massively tilted inward (varus position), the number of toes varies strongly, and also a surplus of toes (polydactyly) is not uncommon. Since a support for the foot is missing, due to the tibial  defect, the foot is usually unstable and cannot bear weight initially.

Aside from the decrease in length of the affected lower leg, also the knee is frequently not normal. Depending upon severity level, the knee is  unstable, due to the malformation, and is often fixed in flexion, so that it is not possible to bear weight here either. If the shin bone is missing completely, then the calf bone is located laterally and above the actual knee level.

Unfortunately, with tibial hemimelia, further physical damage cannot be completely excluded. In the vast majority of cases, however, the small patients are otherwise in good health and show normal mental and physical development.