Tibia vara in Asians: Myth or fact? Verification with three-dimensional computed tomography

Area of Science:

• Orthopedic surgery
• Biomechanical analysis
• Anatomical morphology

Background:

• Common surgical perception suggests Asian tibiae are more varus than non-Asian tibiae.
• This perceived varus is attributed to both acute medial tibial proximal angle (MPTA) and diaphyseal bowing.
• Understanding normative tibial morphology is key for disease process insights and surgical planning.

Purpose of the Study:

• To investigate the normative morphology of the Asian tibia.
• To quantify the medial tibial proximal angle (MPTA) and diaphyseal bowing in an Asian population.
• To provide data for improved surgical planning and prosthesis design.

Main Methods:

• Computed tomography (CT) scans of 100 adult knees were analyzed using 3D software.
• Tibiae were aligned to a standard frame, tibial centroid axis (TCAx), and transmalleolar axis (tmAx).
• Medial tibial proximal angle (MPTA) and diaphyseal bowing were measured using specific protocols.

Main Results:

• Mean MPTA was 87.0° ± 2.2° (TCAx) and 91.6° ± 2.7° (tmAx).
• Mean diaphyseal bowing was 0.1° ± 1.9° varus (TCAx) and 0.3° ± 1.6° valgus (tmAx).
• Significant differences in MPTA were found between ethnic subgroups, but not between sexes.

Conclusions:

• The Asian proximal tibia has an inherent varus morphology, mainly from the MPTA, with minimal diaphyseal bowing.
• This morphological characteristic is not more pronounced than in other populations.
• Findings are relevant for surgical planning and the design of orthopedic implants.