Tibia vara, also known as medial tibial torsion or Blount's disease, refers to the genu varum deformity caused by dysplasia of the medial tibial condyle cartilage.

bubble_chart Etiology

This disease predominantly affects black children, which significantly distinguishes it from other osteochondroses. The cause is unknown, but some suggest it may be due to black children starting to walk earlier (average 10½ months) compared to white children (15 months). Early walking subjects the medial tibial epiphysis to excessive stress, leading to disordered cartilage development and resulting in deformity. Others propose that the condition arises from the African black community's practice of carrying children on their backs, causing hip abduction and genu varum, which increases pressure on the medial tibial epiphysis.

bubble_chart Clinical Manifestations

It is bowlegs, which are further divided into infantile type and adolescent type (6-13 years old). The latter is rare and is often caused by trauma or infection, with less severe deformity. Due to the fetal position in the uterus, most infants have bowlegs, which naturally correct after the age of 1. Therefore, this condition should not be hastily diagnosed before the age of 2.

X-ray findings: The affected lower leg curves inward, presenting as genu varum deformity. The medial condyle of the tibia is enlarged, and the articular surface above it tilts inward, downward, and backward. The medial part of the metaphysis near the epiphysis also expands inward, and may exhibit patchy, uneven density or irregular calcification. The medial cortex of the tibial shaft thickens. Knee joint arthrography shows the tibial articular surface gradually progressing from horizontal to collapse, with compensatory abnormal thickening of the medial meniscus to maintain joint stability (Figure 1).

Figure 1: X-ray manifestations of tibia vara

(1) Initial stage [first stage], 2 years old (2) Intermediate stage [second stage], 5 years old

(3) Late stage [third stage], 6 years old (4) Fourth stage, 8 years old

(5) Fifth stage, 9 years old (6) Sixth stage, 12 years old

bubble_chart Treatment Measures

For severe genu varum deformity, a proximal tibial osteotomy can be performed. It is advisable to perform the procedure early. In a group of 47 tibiae where correction was achieved with a single osteotomy, only 3 were older than 8 years; among the 21 tibiae requiring multiple osteotomies due to recurrent deformity, only 5 were younger than 8 years. Therefore, Blount suggests that surgery can be performed after the age of 2. The dome-shaped osteotomy of the tibia and fibula is the most commonly used technique. However, some cases may also require additional procedures such as lateral tibial epiphyseal arrest or elevation of the medial joint surface.

bubble_chart Differentiation

Distinguishing between early tibia vara (Blount's disease) and physiological bowlegs is essential. Physiological bowlegs are bilaterally symmetrical, with uniform bending of the entire medial tibial cortex. In contrast, tibia vara can be unilateral and asymmetrical. The angle formed by the medial tibial cortex is sharper, and the apex of the bowing is more proximal compared to physiological cases. The angulation progressively worsens, with the development of osteophytes or lipping on the medial tibia and wedging of the proximal tibial epiphysis.