Hallux varus is most commonly due to over-correction of hallux valgus (Skalley 1994, Tourne 1995). The following technical errors predispose to over-correction:
- over-release of the lateral capsule of the 1st MTP joint
- over-resection of the medial eminence of the 1st MT head
- fibular sesamoidectomy (especially in the traditional McBride procedure)
Hallux varus may also be congenital, often in association with metatarsus varus, and occasionally occurs as a neuromuscular deformity.
Mild hallux varus is usually well tolerated (Trnka 1997) provided the toe is not too stiff.
The deformity may be noted incidentally, during assessment of a more complex deformity, or at follow-up after bunion surgery. The commonest complaints are of pressure on the shoe or pain in the 1st MTP joint. Cosmetic complaints seem quite uncommon. Ask the patient about diabetes, generalised arthritis, circulation and sensation.
Examination may show no other abnormality. However,the patient may have evidence of a generalised neurological or deformity syndrome. There may be a skewfoot deformity - valgus heel, adducted forefoot - which is often quite stiff, or a generalised adduction of the forefoot, sometimes with mobile or stiff supination. Check how stiff the 1st MTP joint is, as this will affect how much trouble the patient. Look for blistering, infection or skin breakdown which suggest this is a high-risk deformity, and check sensation and circulation. The patient may have scars from previous hallux valgus surgery.
Some patients need only explanation and reassurance, simple advice on choice of shoes or help in finding shoes to accommodate the foot comfortably. Pain in the MTP joint may be controlled with simple analgesics and appropriate shoes.
Surgery is aimed at realigning the toe, reducing the risk of skin breakdown and treating pain. It is appropriate for patients in whom these goals cannot be achieved by non-surgical measures. It is important to remember that any realignment of the 1st MTP joint may make it stiffer - a partly realigned toe with a stiff MTP may be less acceptable to the patient than the original deformity.
- Medial release and lateral capsular plication, possibly with reinforcement with extensor hallucis brevis tendon - suitable if the deformity is flexible and fully passively correctable (Skalley 1994, Juliano 1996, Myerson 1996)
- reconstruction of the lateral ligament with one-third of the abductor hallucis, transferred through drill holes in the proximal phalanx and MT head, was described by Leemrijse (2008). In seven patients followed for an average of 30 months, the mean alignment of the toe was corrected from 15 deg varus to 15 deg valgus and there were no significant complications, radiographic OA or need for fusion.
- Arthrodesis - suitable when there is a very stiff deformity or degenerative change in the 1st MTP joint (Skalley 1994)