Hallux Valgus
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Direct answer
Hallux valgus is lateral deviation of the great toe at the first metatarsophalangeal joint, with medial drift of the first metatarsal, which produces a painful bunion. It is graded by the hallux valgus angle, commonly quoted as above about 15 degrees, and by the intermetatarsal angle, commonly above about 9 degrees. Most patients are managed with footwear changes, and surgery is reserved for persistent pain.
What you must remember
- Bunion: the prominent medial eminence of the first metatarsal head, which becomes painful from pressure against footwear and often develops a bursa.
- Hallux valgus angle: the angle between the proximal phalanx and the first metatarsal axis, commonly quoted as abnormal above about 15 degrees.
- Intermetatarsal angle: the angle between the first and second metatarsal axes, which is increased in first ray deformity and is the main guide to the choice of osteotomy.
- Sesamoid position: lateral subluxation of the sesamoids on the anteroposterior view indicates a more severe deformity.
- Risk factors: female sex, narrow footwear, family history, ligamentous laxity and flat foot.
- Chevron osteotomy: a V-shaped distal metatarsal osteotomy used for mild to moderate deformity.
- Lapidus procedure: fusion of the first tarsometatarsal joint, used for a hypermobile first ray with a large intermetatarsal angle.
Choosing between the common procedures
Bunion surgery is a choice between osteotomies of the metatarsal and fusion of the first ray, and the deciding factors are the severity of the deformity and the stability of the first ray. The table below sets out the procedures most often compared in the exam.
| Procedure | Usual indication | What it does |
|---|---|---|
| Chevron | Mild to moderate deformity, modest intermetatarsal angle | Distal V osteotomy realigns the head |
| Scarf | Moderate to severe deformity | Z-shaped osteotomy allows larger correction and stable fixation |
| Lapidus | Hypermobile first ray with large intermetatarsal angle | Arthrodesis of the first tarsometatarsal joint |
| Keller | Low-demand elderly patients, now rarely chosen | Resection of the base of the proximal phalanx |
The procedure is chosen by measuring the angles on a weight-bearing radiograph, not by the appearance of the bunion. Keller excision is now rarely chosen for active patients, because it can shorten the first ray and weaken push-off. Books differ on the exact angle cut-offs for each osteotomy, so the examiner usually rewards the logic of matching the correction to the deformity rather than a single number.
Where the exam tries to catch you
Hallux valgus questions usually test the link between the angle and the procedure, and examiners look for that reasoning.
- Trap: believing the bunion itself must be removed to cure the pain. Correct: the bunion results from metatarsal drift, and surgery realigns the bone, while footwear modification is the first step.
- Trap: choosing a Chevron osteotomy for a severe deformity with a large intermetatarsal angle. Correct: a Scarf osteotomy or a Lapidus procedure is preferred, because the Chevron cannot correct a large angle adequately.
- Trap: fusing the first tarsometatarsal joint for every case. Correct: the Lapidus procedure is reserved for a hypermobile first ray, usually with a large intermetatarsal angle.
Frequently asked questions
What is the normal intermetatarsal angle in hallux valgus?
The intermetatarsal angle is commonly quoted as below about 9 degrees in the normal foot. A larger angle indicates first ray deformity and guides the choice of osteotomy. Textbooks differ slightly on the exact cut-off values.
Which osteotomy is used for a severe hallux valgus with a large intermetatarsal angle?
A Scarf osteotomy is commonly used for a severe hallux valgus with a large intermetatarsal angle. It is a Z-shaped metatarsal osteotomy that allows substantial correction and stable fixation. A Lapidus procedure is used when the first ray itself is hypermobile.
When is a Lapidus procedure indicated in hallux valgus?
A Lapidus procedure is indicated in hallux valgus when the first ray is hypermobile and the intermetatarsal angle is large. It fuses the first tarsometatarsal joint to stabilise the ray. It is not a routine first choice for mild deformity.
Is conservative management effective for hallux valgus?
Conservative management, with wide shoes, toe spacers, padding and orthoses, relieves symptoms in many patients with hallux valgus. It does not correct the deformity, so it is used before surgery and in patients who decline it. Persistent pain despite these measures is the usual indication for an osteotomy.