Tibial sesamoid position

Case contributed by Leonardo Lustosa
Annotated image

Tibial sesamoid position is measured by the overlap of the medial sesamoid over the longitudinal line over the 1st metatarsal diaphysis.

The overlap is painted in red.

Case Discussion

The tibial sesamoid position (TBS) is assessed by the position of the medial sesamoid in relation to the mid axis of the 1st metatarsal.

Smith et al1 graded the tibial sesamoid position:

  • Grade 0 - no displacement of sesamoid relative to the reference line
  • Grade 1 - <50% overlap of sesamoid to the reference line
  • Grade 2 - >50% overlap of sesamoid to the reference line
  • Grade 3 - Sesamoid completely displaced beyond reference line

It is a useful radiographic measurement in the assessment of hallux valgus.

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