Hallux valgus DMAA

With incline of the articular surface

Assessing the incline of the articular surface is of utmost importance. In this type of Hallux Valgus, the joint’s angle has become lateral. One should not perform any surgery before having a good look at the x-ray taken with the patient standing and look specifically for it. For many years, this joint is just fine and does not seem to need scrutiny. But if the surgeon is not aware of this particular type of Hallux Valgus, the results will be terrible: The toe will be aligned correctly, but the joint will not work.

DMAA (Distal Metatarsal Articular Angle) is also called MAO (Metatarsal Articular Orientation) and podiatrists call this PASA (Proximal Articular Set Angle). The normal range is 0º to 10º.
With the passing of years, however, even this type of Hallux Valgus can become incompatible (a source of trouble) and one needs to adapt all these procedures according to this feature.

Minor to Moderate Types

In these metatarsal distal osteotomies, the procedure is simply altered somewhat.

Modified Chevron:

Resecting a small bone bevel at the superior area of the metatarsal so as to correct the incline of the metatarsal head.

Modified Mitchell Osteotomy:
This is a less common procedure, but it adjusts the two saw lines so they are at variance. The first distal line is incomplete and parallel to the articular surface whereas the other proximal line is perpendicular to the foot alignment.

Moderate to Acute Types

In such cases, the surgeon needs to perform either a proximal or diaphyseal osteotomy, because the inter-metatarsal angle is too important (14º or more). The reason is that even if a distal osteotomy could correctly rectify a big 1-2 angle, the toe will stay laterally deviated when the DMAA is great,. The first adjustment is to add an Akin phalangeal osteotomy. In some exceptional cases where this would not be enough, it is necessary to add Mann’s crescent osteotomy proximally and a modified Ludloff procedure, ending with a double metatarsal distal osteotomy . (Scarf osteotomy is more versatile in that it can correct a DMAA up to 10º without having to perform a distal osteotomy.)

Example of DMAA corrected by the Akin phalangeal osteotomy

Note: I now correct the exaggerated space between the 1st and 2nd metatarsals by performing a closed-bevel osteotomy at the proximal base of the 2nd metatarsal, so as to reduce this rather unattractive space between the toes. If there also happens to be a dislocation of the 2nd MTP, with a longer 2nd metatarsal, I perform a modified Weil osteotomy, which, on top of reducing the dislocation of the 2nd MTP, can also correct the divergence of the toe. Sometimes, a Girdlestone tendon transfer can fine-tune some medial or lateral divergence.
The most difficult problem associated with Hallux Valgus is the associated collapse of the other metatarsals: When should the 2nd, or 2nd and 3rd, or the 2nd, 3rd and 4th metatarsals be treated as well? You are invited to read the Powerpoint presentation located in the Chapter “Other Issues”: “Metatarsal Problems in Hallux valgus Surgery” (which was shown at the Winniped Conference of the Canadian Orthopaedic Association in October 2003).

[Haut de la page]