Hallux Valgus: How to perform

Last updated on July 6 2022

Description

Hallux valgus is a deformity at the base of the big toe. In some very mild cases of bunion formation, surgery may only be required to remove the bump that makes up the bunion.  To perform this surgery, it is needed to know whether or not the metatarsal bone will be cut and realigned as well. To decide this, it is important to measure the angle made between the first metatarsal and the second metatarsal. The normal angle is around 9° or 10° degrees. If the angle is 13° or more, the metatarsal will probably need to be cut and to be realigned.

Measurements

The measurements made by the procedure are displayed in the image:

• Hallux Valgus Angle (HVA - normal value < 15°): the angle between the longitudinal axes of the first metatarsal and the first proximal phalanx;
• Intermetatarsal Angle (IMA - normal value < 9°): the angle between the longitudinal axes of the first and second metatarsals;
• Distal Metatarsal Articular Angle (DMAA - normal value < 10°): the angle between the tangent line to the distal articular surface of the first metatarsal and the perpendicular line to the longitudinal axis of the first metatarsal;
• Proximal Metatarsal Articular Angle (PMAA): the angle between the tangent line to the proximal articular surface of the first metatarsal and the perpendicular line to the longitudinal axis of the first metatarsal;
• Distal Articular Set Angle (DASA - normal value 0° - 5°): the angle between the perpendicular to the proximal articular surface and the longitudinal bisection of the hallux proximal phalanx.

Auxiliary References

To show this procedure, PeekMed® needs additional references:

• The perpendicular line to the longitudinal axis of the first metatarsal;
• The perpendicular line to the proximal articular surface