Hallux valgus

Synonyms: hallux abductovalgus, bunion

What is a bunion (hallux valgus)?

Hallux valgus describes lateral deviation of the great toe so as to put a valgus deformity on the first metatarsophalangeal (MTP) joint; it is commonly known as a bunion. A deviation of greater than 15° is considered abnormal. This deviation upsets the biomechanics of the foot. It may cause subluxation of the first MTP joint and the great toe may even overlap the second toe.

Lateral subluxation produces a prominence on the metatarsal head (bunion) often followed by the development of a fluid-filled bursa. This becomes painful as it rubs against the shoe.

Pathophysiology

It is helpful to consider this, as correction of the biomechanical factors may prevent excessive pronation and progression of the deformity:

• When walking, the hallux and digits stay parallel to the long axis of the foot. This is true generally regardless of how pronated or abducted the forefoot is.

• The pull of the conjoined adductor tendon, extensor hallucis longus and flexor hallucis longus tendons ensures that the hallux and digits remain parallel.

• Displacement of the joint gives the tendons mechanical advantage and this displaces the joint further. As this occurs, tension is created on the medial aspect of the joint (with compression laterally).

• Medial tension causes ligaments to pull and cause the bone to proliferate on the dorsomedial aspect of the first metatarsal head.

• Lateral tension causes the sesamoid apparatus to stick in a dislocated position laterally.

• Remodelling occurs laterally and medially and this affects joint cartilage.

How common are bunions?¹

The exact prevalence is unknown, but it increases with age. One systematic review and meta-analysis found a prevalence estimate of 23% in adults aged 18-65 years, and 35.7% in people aged 65 years and older. There was a higher prevalence of bunions in women (30%) compared with men (13%).

Because the risk factors affect both feet, the condition is usually bilateral, although it may be more marked on one side than the other.

Risk factors^{2 3 4}

It is likely that the cause is multi-factorial. A number of risk factors have been noted to be associated with hallux valgus:

• Footwear. There is a significant association with wearing tight-fitting or high-heeled shoes.⁵ However, the condition can develop in people who have never worn such footwear and footwear is not usually a factor in juvenile hallux valgus. Equally not all people who wear high heels develop hallux valgus.

• Genetic predisposition.

• Gender. There is higher incidence of hallux valgus in women. Footwear may account for this.

• Abnormalities of the foot:

  • Pes planus (flat feet).

  • Hypermobility.

  • Achilles tendon contracture.

• Positional change due to neuromuscular conditions such as:

  • Stroke.

  • Cerebral palsy.

  • Multiple sclerosis.

  • Charcot-Marie-Tooth syndrome.

• Systemic conditions causing ligament laxity:

  • Marfan's syndrome.

  • Ehlers-Danlos syndrome.

  • Rheumatoid arthritis.

  • Gout.

  • Psoriatic arthropathy.

• Certain activities which may put greater force on the forefoot:

  • Ballet dancing. There is a weak association with ballet dancing. Dancers put a great deal of stress through the first MTP joint but it is unlikely that dancing causes bunions.⁶

  • Rock climbing.⁷

Bunion (hallux valgus) symptoms

Presentation is usually as a result of pain, although the condition is also unsightly. Pain is usually progressive and may have been present for many years. The frequency or duration of pain may have recently started to increase and activity may exacerbate the pain.

History

• A patient may present with a deep or sharp pain in the hallux MTP joint on walking and have exacerbation during particular activities. This suggests degeneration of the intra-articular cartilage.

• There may be an aching pain in the metatarsal head due to irritation by shoes. There may be a recent increase in the size of the deformity or medial bump.

• Ask about limitation of physical or daily living activities to understand the severity of the pain. Ask what relieves the pain. It may be simply removing shoes.

• There may be a history of trauma or inflammatory arthritis.

• A rarer presentation is burning pain or tingling in the dorsal aspect of the bunion, which indicates entrapment neuritis of the medial dorsal cutaneous nerve.

• The patient may also describe symptoms caused by the deformity, such as a painful overlapping second toe, interdigital keratosis, or ulceration to the medial metatarsal head, without complaint of the bunion deformity.

• Enquire about a medical history of diabetes, vascular disease or neuropathy, as these conditions will increase the risk of complications,

Examination

Examine the foot whilst bearing weight, although much of the examination will have to be performed whilst not weight bearing. Watch the patient walk. This will indicate the degree of pain and difficulty that the problem causes and abnormal gait may point to a contributory factor or be the result of the condition.

• Note the position of the hallux relative to the other toes. It may be overriding, under-riding or abutting the next toe. Distortion of the joint may occur in more than one plane.

• Note the medial prominence of the joint. Erythema or bursa indicates pressure from shoes and irritation.

• Note the range of movement of the hallux MTP joint. Normal dorsiflexion is 65-75° with plantar flexion less than 15°. Note if pain, crepitation, or both are present. Pain without crepitation suggests synovitis.

• Note any keratosis that suggests abnormal friction from abnormal gait.

• Associated deformities may include second digit hammer toes and flexible or rigid flat foot. Instability of the second digit may allow a more rapid progression of hallux valgus, as it is unable to act as an adequate lateral buttress.

• With the patient standing note any:
  

  • Increase of hallux abduction in the transverse and frontal planes.

  • Increase in medial prominence.

  • Change in dorsiflexion of the joint.

Also, note the general condition of skin and peripheral pulses. If there are signs of vascular disease or neuropathy, this will increase the risk of complications. Also if surgery is to be contemplated it is imperative that peripheral blood flow be adequate for healing.

Investigations

Usually diagnosis is clinical, and investigations are not needed. X-ray will show the degree of deformity and may indicate subluxation of the joint.

In an elderly patient in whom an operation is considered, routine investigations are required to assess suitability for operation.

Differential diagnosis¹

• Hallux rigidus (arthritis of the MTP joint).

• Sesamoiditis.

• Fractures.

• Gout.

• Rheumatological disease (eg, rheumatoid arthritis).

• Neuropathic pain (particularly diabetes).

• Infection.

Bunion (hallux valgus) treatment^{1 8}

Non-operative treatment involves patient education, shoe modifications, toe pads and positioning devices, and activity modifications. Surgery is considered in patients who fail non-operative treatment, with the goal of pain relief, correction of the deformity, improved stability, and improved quality of life. More than 100 different procedures have been described to treat hallux valgus.⁹

Conservative management

Patients should be given appropriate information and advice about hallux valgus . Advice should include the following:

• Advise wearing appropriate shoes (low-heeled, soft-soled shoes with avoidance of tight-fitting or high-heeled shoes).

• Shoes with laces or an adjustable strap may be helpful.

• Explain that bunions can be progressive and that non-surgical treatments alleviate symptoms but do not limit progression.

• The most important indication for surgery is pain, not deformity, although there will often be concern about the appearance of the deformed joint and about the shoes which must be worn to accommodate this.

Conservative measures which may be helpful include:

• Analgesics, including non-steroidal anti-inflammatory drugs, may reduce pain and make the condition more bearable.

• Bunion pads can be bought over the counter and may offer symptomatic relief.

• Ice packs, which may relieve pain.

• Podiatry referral for footwear advice and, where appropriate, orthoses. There is no good evidence that orthoses or night splints prevent progression, correct the deformity or improve mobility; also, the effect on pain relief has not been found to be long-lasting.

Refer to a diabetic foot care service if the person has diabetes.

Consider referral for surgery if the above measures do not ease symptoms.

Surgery

The result of conservative management is so poor that surgery may be an attractive option. Surgery may be delayed without an adverse effect on the final outcome.

Indications for surgery

• The bunion is painful, is not responding to conservative measures and is worsening.

• The second toe is affected.

• Pain or difficulty with footwear, inhibition of activity or lifestyle, and associated foot disorders that can be caused by this condition.

Contra-indications to surgery

• Peripheral arterial disease.

• Active infection.

• Active osteoarthropathy.

• Septic arthritis.

• Lack of pain or deformity.

• Other significant medical conditions, especially of the cardiovascular or respiratory system, that put the person at risk during the procedure.

Complications of surgery
These may depend on the procedure but can include:

• Delayed healing of the incision.

• Osseous malunion or non-union.

• Nerve damage.

• Haematoma.

• Failure of a prosthesis.

• Displacement of the osteotomy.

• Delayed suture reaction.

• Cellulitis.

• Osteomyelitis.

• Avascular necrosis.

• Limitation of joint motion.

• Hallux varus.

• Recurrence.

• Risks associated with all surgery, especially if the patient is elderly. This includes venous thromboembolism.

The potential for complications is great enough that surgery should not be considered for cosmetic reasons alone.¹⁰

Operative options¹⁰

There are a number of surgical options and the choice of procedure will depend upon the precise nature of the problem. In general the choice depends on the severity of the deformity.¹¹ It has not yet been determined which operation(s) are superior.

Varying degrees of osteotomy may be used, essentially to excise the bony prominence. In mild deformity, some type of distal metatarsal osteotomy is performed, whereas in more severe deformity, phalangeal osteotomy is also involved. Keller's arthroplasty involves creating a flexible joint by excision of the medial eminence of the metatarsal head together with some of the proximal phalanx. Arthrodesis (fusion) of the joint may be considered, particularly where deformity is severe, there is osteoarthritis, or other procedures have failed.¹² Replacement of the joint may be an option particularly where it is arthritic; however, this is more often the treatment for hallux rigidus.

Minimally invasive surgery is gradually gaining credence in the literature but has not yet become standard practice in the UK.^{13 14} The National Institute for Health and Care Excellence (NICE) guidance on minimal access techniques acknowledges that less invasive techniques may be attractive to patients but need further evaluation.¹⁵

Complications

Complications of bunions include:

• Difficulty finding footwear to fit.

• Osteoarthritis of the first MTP joint.

• Loss of mobility and increased risk of falls in elderly people.

• Neuritis or nerve entrapment.

• Overlapping or underlapping an adjacent toe.

• Hammer toes.

• Hallux metatarsocuneiform joint exostosis.

• Sesamoiditis.

• Ulceration.

• Inflammatory conditions, such as bursitis or tendonitis of the first metatarsal head.

Prognosis

The outlook is highly variable, as is that of the patients who are treated. Hence there is a shortage of adequate trials to compare the outcomes of the various forms of treatment. A Cochrane review in 2004 found very little good evidence on which to assess either conservative or operative treatments and the update in 2009 was withdrawn.¹⁶

Bunion (hallux valgus) prevention

Correction of the biomechanical factors may prevent excessive pronation and progression of the deformity. Judicious footwear may help prevent bunions in some, but not all, cases.