Bunion

A bunion is hallux valgus: lateral deviation of the great toe at the first metatarsophalangeal joint, with medial deviation (varus) of the first metatarsal and a painful medial bony prominence. The sesamoids subluxate laterally and the extensor and flexor tendons bowstring across the joint.

• Prevalence is about 23% in adults aged 18 to 65 and about 35% over 65. Women are affected 2 to 3 times more than men.
• Causes and risk factors: inherited foot shape (a family history in about 70%), narrow pointed shoes and high heels, pes planus, first ray hypermobility, generalised ligamentous laxity, a long first metatarsal, tight Achilles tendon, rheumatoid arthritis, neuromuscular disease and previous trauma.
• Severity on weight bearing X-ray: hallux valgus angle 15 to 20 degrees (mild), 20 to 40 degrees (moderate), above 40 degrees (severe). Intermetatarsal angle up to 11 degrees (mild), 11 to 16 degrees (moderate), above 16 degrees (severe). A normal hallux valgus angle is below 15 degrees and a normal intermetatarsal angle is below 9 degrees.
• Juvenile bunions occur in adolescents, often familial, with a high recurrence after surgery.

• A medial prominence at the first metatarsal head that is red, tender or inflamed (overlying bursitis), pain in tight shoes, and a great toe that angles toward or overlaps the second toe.
• Associated problems: callus under the second metatarsal head (transfer metatarsalgia), second toe hammertoe or crossover deformity, corns between the toes, pronation of the hallux, numbness from compression of the dorsomedial cutaneous nerve, and a flat or pronated foot.
• Pain on movement or limited dorsiflexion suggests arthritis of the joint (hallux rigidus). Pain on the plantar side under the first metatarsal head suggests sesamoid disease.
• Differential diagnosis: gout, hallux rigidus, sesamoiditis, rheumatoid arthritis, septic bursitis, septic arthritis, bunionette (fifth toe), ganglion and tumour.
• Red flags: hot, red, swollen joint with fever (infection or crystal arthritis), ulceration, poor perfusion, diabetic neuropathy and rapid change.
• Complications: chronic pain, bursitis, ulceration over the prominence, transfer metatarsalgia, hammertoe, osteoarthritis of the joint, and difficulty with footwear.

• Clinical examination standing and walking, with assessment of first ray mobility, joint range, hindfoot alignment, calf tightness, perfusion and sensation.
• Weight bearing X-rays of the foot (anteroposterior, lateral and sesamoid axial views) to measure the hallux valgus angle, intermetatarsal angle and distal metatarsal articular angle, and to assess sesamoid position and arthritis.
• Blood tests (urate, CRP, ESR, rheumatoid factor, anti-CCP antibodies, HbA1c) when gout, inflammatory arthritis or diabetes is suspected. Aspirate a hot joint for culture and crystals.

• Conservative treatment, for symptomatic patients and as first line:
  • Shoes with a wide, deep toe box, a low heel (below 3 cm) and soft uppers, preferably stretched or modified over the prominence.
  • Silicone or gel bunion pads over the prominence, toe spacers between the first and second toes, and custom or prefabricated orthoses for flat feet and first ray instability.
  • Paracetamol 1 g orally 6 hourly, ibuprofen 400 mg orally 8 hourly with food for 1 to 2 weeks, or topical diclofenac 1% gel 2 to 4 g 3 to 4 times daily. Ice for 10 to 15 minutes after activity.
  • Calf stretching and foot intrinsic strengthening. These measures reduce pain but do not correct the deformity. Night splints and toe separators do not reduce the angle in adults.
  • Treat bursitis with padding and a short course of NSAID. Corticosteroid injection into the bursa (methylprednisolone 10 to 20 mg with lidocaine 1% 0.5 mL) is occasionally used for a refractory inflamed bursa, with a risk of skin atrophy and infection.
• Surgery, for persistent pain and functional limitation after 3 to 6 months of correct conservative care (not for cosmetic reasons alone). Many operations exist, and the choice depends on angles, joint congruence, arthritis and first ray stability:
  • Mild to moderate deformity: distal first metatarsal osteotomy (chevron type) with soft tissue release, or a diaphyseal (scarf type) osteotomy.
  • Moderate to severe deformity: proximal metatarsal osteotomy, or first tarsometatarsal joint fusion for a hypermobile first ray.
  • Arthritis of the first metatarsophalangeal joint: joint fusion or, less often, arthroplasty.
  • Minimally invasive percutaneous osteotomies give similar results to open surgery in selected patients.
  • Prophylaxis: cefazolin 2 g IV once at induction (3 g if weight is above 120 kg). Give low molecular weight heparin only if there are additional thrombosis risk factors.
  • Recovery: protected weight bearing in a stiff soled shoe or boot for 4 to 6 weeks, return to normal shoes at 8 to 12 weeks, and swelling may last 6 months. About 80 to 90% are satisfied, with recurrence in about 5 to 15% and complications of stiffness, nerve injury, malunion and avascular necrosis of the metatarsal head.
• Special groups:
  • Adolescents: delay surgery until skeletal maturity unless pain is severe, because recurrence is high.
  • Diabetes and peripheral arterial disease: assess perfusion and sensation, use conservative care, and delay surgery until glucose is controlled and perfusion is adequate.
  • Rheumatoid arthritis: treat the disease, and prefer fusion procedures when surgery is needed.
  • Pregnancy: supportive footwear, padding and paracetamol. Avoid NSAIDs after 20 weeks.
  • Renal impairment and gastrointestinal disease: use topical agents instead of oral NSAIDs.
• Follow up: review every 6 to 12 months to monitor progression. Refer to foot and ankle surgery for pain not controlled by 3 to 6 months of conservative care, ulceration, or marked deformity.