Assess the biomechanical function and functional impairment of the foot by clinical and, as far as necessary, radiological examinations.
Treatment depends on symptoms (pain and functional impairment), not clinical or radiological findings alone.
Orthoses or physiotherapy can be used to alleviate the pain in the short term, at least, but surgical treatment is probably effective also in the long term.
Patients with symptoms should be referred to a foot orthopaedist for the assessment of treatment options.
Definition
A bony prominence or soft tissue lump at the base of the big toe is commonly known as a bunion.
The most common cause of a bunion is hallux valgus, a valgus malposition of the joint at the base of the big toe (first metatarsophalangeal [MTP] joint), causing the big toe to turn towards the other toes. The lump actually represents prominence of the end of the metatarsal bone due to the malposition, not excess bone.
A bunion may also be due to osteoarthritis of the first MTP joint (hallux rigidus), in which actual bony osteophytes grow at the joint margins.
The radiologically measured hallux valgus angle (first metatarsophalangeal angle) is normal if it is below 15° and the intermetatarsal angle (angle between the first and second metatarsal bones) is normal if it is below 10°.
The malposition often involves increased rotation of the first metatarsal bone and is typically emphasized during weight-bearing.
The condition progresses with time.
Epidemiology and aetiology
Hallux valgus is a common ailment reported in about 23% of the adult population and even in more than 35% of the elderly.
It is clearly more common in women than in men (15:1). In men, in particular, it shows a strong maternal inheritance.
Its aetiology remains unknown and is probably multifactorial.
Wearing high-heeled shoes, a certain type of structure of the forefoot, first metatarsal bone and medial cuneiform bone, and pronation may predispose to the condition.
There is no certainty about any association between overpronation, i.e. adult flatfoot, and instability of the first ray (first tarsometatarsal [TMT] joint) and development of the condition.
There may be underlying inflammatory arthropathies, such as rheumatoid arthritis, very often affecting the metatarsophalangeal joints and, through their destruction, causing hallux valgus malposition.
As there are no muscles attached to the distal end of the first metatarsal bone, it is biomechanically unstable by nature. With developing malposition, the distal end of the metatarsal bone shifts medially and, as the distance increases, all tendons crossing the first MTP joint begin to act as forces shifting the big toe laterally (Picture 1). In addition, the metatarsal bone rotates (Picture 2). As a result of the malposition of the first ray, the function of the medial side of the front of the foot is impaired and weight shifts to a more lateral position.
Symptoms
The most common symptoms leading the patient to seek treatment are pain and shoe problems.
Biomechanically, the problem is impaired loading of the whole forefoot, leading to faulty gait, functional impairment, balance problems and, in older patients, in particular, falling.
The pain may occur in the area of the hallux valgus itself but often also at the ball of the foot (so-called transfer metatarsalgia), as the load shifts from the first ray with poor capacity for weight bearing more laterally to the ball of the foot. This causes pain and swelling particularly in the second MTP joint, stress-induced osteopathy of the second metatarsal bone and hammer toe malformation. Occasionally, there may also be symptoms resembling nerve entrapment, called Morton's disease.
A large bunion and spreading of the forefoot make it difficult to find suitable, sufficiently spacious shoes, and cause friction.
The condition significantly affects the quality of life assessed by both general and foot-specific metrics.
Patients rarely complain of cosmetic problems, and surgical treatment is never used on cosmetic grounds alone.
Clinical examination
The diagnosis is based on good clinical examination and x-ray examination of the foot (standing AP, oblique and lateral projections; see also Picture 3). In some cases, x-ray examination of the ankle is also needed to define the alignment of the hindfoot in more detail.
The patient should be examined with the lower limbs bare from the shin downwards in a standing and sitting or supine position.
Observe particularly the alignment of the ankle, foot and toes, stability of the first ray, mobility of joints and any tightness in the calf.
Calluses or the absence of pressure signs on the skin give a good picture of the pressure conditions in the foot. For example, skin below the first MTP joint may be perfectly soft, whereas there may be marked pressure-induced callus formation below the second MTP joint.
Examining passive dorsiflexion of the ankle with the lower ankle joint supported in a neutral position, the knee flexed and straight, while the patient keeps the limb relaxed (Silfverskiöld test) gives an idea of whether the calf is tight.
Treatment
The aim of treatment is primarily to alleviate pain and, additionally, to correct malpositions and the foot malfunction.
Conservative treatment
There is very little high-quality research available on the effectiveness of conservative treatment of hallux valgus.
Exercise, manual therapy, taping and nocturnal splinting may have positive effects on pain, functional ability and the hallux valgus angle in 1-3-month follow-up 181213.
Depending on the type of malfunction, physiotherapy is based on supporting muscle function and increasing joint mobility.
Shoes must be sufficiently spacious and low-heeled. Rocker sole shoes may help to alleviate the symptoms.
Orthoses and supports can be tried if they alleviate the symptoms.
Calf muscle stretching may alleviate pain at the ball of the foot if the pain is associated with calf tightness.
Surgical treatment
The main indications for surgical treatment are symptoms and functional impairment experienced despite conservative treatment and which can be considered to be due to the hallux valgus malposition.
Regardless of the technique used, the idea behind surgical treatment is to restore the alignment and stability of the first ray, restoring the muscle balance in the whole foot and correcting inappropriate loading. Technically, this can be done either by cutting and realigning the first metatarsal bone (osteotomy), or by fusion correcting the alignment of the first TMT joint (modified Lapidus procedure) (Picture 3).
Arthrodesis of the first MTP joint is only rarely used for primary surgical treatment.
Bunionectomy alone or resection of the proximal end of the first proximal phalanx (Keller's procedure) is not acceptable today.
Recovery from surgery
Recovery from surgery is slow, taking 3 to 6 months. The foot often remains swollen for a long time restricting the use of shoes and movement. Change of job description or part-time sick leave are often needed to facilitate return to work.
Further treatment depends on the procedure performed. Depending on the surgical technique, immediate mobilization wearing a therapeutic shoe may be possible or restricted weight bearing may be needed for about 6 weeks. To minimize limitation of motion, moving the first MTP joint should be started no later than 2 weeks after the procedure.
Rehabilitation provided by a physiotherapist plays a key role in obtaining good results of surgery.
References
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