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Bunion (hallux valgus)

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What is Hallux Valgus (Bunion)?

Hallux Valgus (from Latin: *hallux* = big toe, *valgus* = turned outward) is a common foot deformity characterized by a lateral deviation (angling outward, toward the second toe) of the great toe (hallux) relative to the first metatarsal bone (1, 2). This deviation occurs at the first metatarsophalangeal joint (MTPJ), the joint at the base of the big toe.

As the big toe angles outward, the head of the first metatarsal bone becomes more prominent on the inner (medial) side of the foot. This prominent bump is commonly referred to as a bunion (1). The bunion itself can involve enlargement of the bone (exostosis) and/or inflammation of the overlying bursa (a fluid-filled sac), leading to pain, redness, and swelling (2, 3).

Therefore, hallux valgus refers to the angular deformity of the toe, while the bunion is the resulting prominence at the base of the toe.

The foot comprises tarsal bones, metatarsals, and phalanges. Hallux valgus involves the first metatarsal and the phalanges of the big toe (1).

Causes and Risk Factors

The development of hallux valgus is often multifactorial, involving a combination of intrinsic and extrinsic factors (1, 2, 4):

  • Genetics/Heredity: A family history is common, suggesting a genetic predisposition related to foot structure, ligamentous laxity, or biomechanics (1, 4).
  • Footwear: Wearing narrow, pointed-toe, and/or high-heeled shoes is strongly associated with the development and progression of hallux valgus, particularly in women. These shoes crowd the toes and increase pressure on the forefoot (1, 2, 4).
  • Foot Structure and Biomechanics: Certain foot types, such as flat feet (pes planus) or excessive pronation (rolling inward of the foot), can alter forces across the first MTPJ and contribute to the deformity (1). A short or elevated first metatarsal can also play a role.
  • Ligamentous Laxity: Generalized looseness of ligaments can make the foot more susceptible to deformation under stress.
  • Arthritic Conditions: Inflammatory conditions like rheumatoid arthritis can damage the joint and lead to deformity (1).
  • Age: The prevalence increases with age.
  • Gender: Hallux valgus is significantly more common in women than men, likely due in large part to footwear choices (1, 4).

Note: The complex biomechanical descriptions involving pronation, supination, specific joint actions (Lisfranc, etc.), and muscle tensions (abductor hallucis, extensors) are detailed theories about how factors like flat feet might contribute, but the exact sequence and importance of each element can be debated and difficult to simplify accurately. The core issue involves abnormal forces leading to medial deviation of the first metatarsal and lateral deviation of the hallux.

Clinical Manifestations and Symptoms

Patients typically present with one or more of the following (1, 3):

  • Visible Bunion: A bump on the medial side of the first MTPJ.
  • Pain: Often localized over the bunion bump, aggravated by shoe pressure or activity. Pain can also occur within the joint itself.
  • Redness and Swelling: Due to bursitis or inflammation over the bunion.
  • Big Toe Deviation: The hallux points laterally towards the second toe, sometimes overlapping or underlapping it.
  • Limited Range of Motion: Stiffness or reduced movement at the first MTPJ (Hallux Limitus or Rigidus can sometimes coexist or develop) (1).
  • Difficulty with Footwear: Problems finding shoes that fit comfortably without irritating the bunion.
  • Skin Changes: Calluses or corns may develop over the bunion, under the second metatarsal head (due to altered weight-bearing), or between overlapping toes.
  • Nerve Irritation: Numbness or tingling may occur if the medial cutaneous nerve is compressed by the bunion or tight shoes.

Associated Foot Disorders

Hallux valgus often occurs alongside or contributes to other foot problems (1, 3):

  • Lesser Toe Deformities: Hammertoes, claw toes, or mallet toes, especially of the second toe due to pressure from the deviated hallux.
  • Metatarsalgia: Pain under the ball of the foot (metatarsal heads), often under the second metatarsal head, due to altered weight distribution (transfer metatarsalgia). Plantar calluses may form here.
  • Bunionette (Tailor's Bunion): A similar prominence on the outer side of the foot at the base of the fifth toe (fifth MTPJ).
  • Midfoot Arthritis: Changes in forefoot mechanics can contribute to arthritis in the midfoot joints over time.
  • Ingrown Toenails: Increased pressure between toes can contribute.

Evaluation and Diagnosis

Diagnosis is typically made through clinical examination and confirmed with imaging (1, 5):

  • Clinical Examination:
    • Inspection: Assessing the degree of hallux deviation, bunion prominence, skin condition, and presence of associated deformities (lesser toes).
    • Palpation: Identifying areas of tenderness (over the bunion, within the joint, under metatarsal heads), assessing joint flexibility/stiffness (range of motion of the first MTPJ), and checking for crepitus.
    • Gait Analysis: Observing how the deformity affects walking.
    • Footwear Evaluation: Assessing shoe fit and wear patterns.
  • Radiographs (X-rays): Weight-bearing Anteroposterior (AP), Lateral, and sometimes Oblique views of the foot are essential (1, 5). They allow measurement of key angles to assess deformity severity and guide treatment planning:
    • Hallux Valgus Angle (HVA): Angle between the long axes of the first metatarsal and the proximal phalanx of the hallux. Normal <15°.
    • Intermetatarsal Angle (IMA): Angle between the long axes of the first and second metatarsals. Normal <9°. Indicates the degree of splaying (metatarsus primus varus).
    • Distal Metatarsal Articular Angle (DMAA) or PASA: Angle of the articular surface of the first metatarsal head relative to its long axis. Indicates joint orientation.
    • Assessment of joint congruency, arthritis, sesamoid position, and lesser toe deformities.
Weight-bearing X-rays are crucial for evaluating hallux valgus deformity and measuring angles like HVA and IMA (1, 5).

Severity Grading (Commonly Used): Based primarily on HVA and IMA angles (definitions can vary slightly) (5):

  • Mild: HVA 15-20°, IMA 9-11°
  • Moderate: HVA 21-39°, IMA 12-17°
  • Severe: HVA ≥40°, IMA ≥18°

Mild Hallux Valgus

Moderate Hallux Valgus

Severe Hallux Valgus

 

Conservative Treatment

Non-surgical treatment aims to relieve symptoms and potentially slow progression, but does not correct the underlying bone deformity (1, 6). It is often the first line of approach, especially for mild/moderate symptoms.

  • Footwear Modification: Wearing shoes with a wide, deep toe box, soft upper materials, and low heels to reduce pressure on the bunion and forefoot. Avoiding narrow, pointed, or high-heeled shoes (1, 6).
  • Padding and Shielding: Using gel or moleskin pads over the bunion to reduce friction and pressure from shoes.
  • Orthotics: Custom or over-the-counter arch supports or insoles can help control abnormal foot mechanics (like pronation) and improve foot function, potentially reducing stress on the MTPJ (1, 6).
  • Toe Spacers/Splints: Devices worn between the big toe and second toe, or night splints aiming to realign the toe. Evidence for long-term correction is limited, but they might provide temporary symptom relief for some (1).
  • Activity Modification: Avoiding activities that exacerbate pain.
  • Ice Application: Can reduce inflammation and pain after activity.
  • Medications: Oral NSAIDs (e.g., ibuprofen) or topical anti-inflammatories for pain and inflammation (1). Corticosteroid injections into the bursa or sometimes the joint may provide temporary relief for acute inflammation but are used cautiously (1).
  • Physical Therapy: Stretching exercises (e.g., for tight calf muscles) and strengthening exercises for intrinsic foot muscles may be beneficial as part of overall foot care, though limited direct effect on the deformity itself.

Surgical Treatment

Surgery is considered when conservative measures fail to provide adequate pain relief and the deformity significantly impacts quality of life or function (1, 7). The goals are to relieve pain, correct the deformity, and restore normal foot mechanics.

  • Indications: Persistent pain, difficulty finding shoes, progressive deformity, associated lesser toe problems, functional limitations (1). Surgery is generally not recommended for cosmetic reasons alone.
  • Procedure Choice: There are over 100 different surgical procedures described. The choice depends on the severity of the deformity (angles on X-ray), joint congruency, presence of arthritis, patient age, activity level, and surgeon's preference (1, 7). Common principles involve:
    • Removing the bony prominence (bunionectomy).
    • Realigning the first metatarsal bone relative to the other metatarsals (osteotomy). Common types include distal osteotomies (e.g., Chevron, Mitchell) for mild/moderate deformities, and proximal osteotomies (e.g., Scarf, base wedge, Lapidus arthrodesis) for moderate/severe deformities with larger IMAs (7).
    • Realigning the great toe relative to the metatarsal (may involve phalangeal osteotomy - Akin).
    • Releasing tight soft tissues (lateral release) and tightening loose ones (medial capsulorrhaphy).
    • Arthrodesis (joint fusion): Fusing the first MTPJ or the first tarsometatarsal joint (Lapidus) may be indicated for severe deformity, arthritis, or instability (7).
  • Fixation: Osteotomies and fusions are typically fixed internally with screws, plates, or pins.
  • Minimally Invasive Surgery (MIS): Techniques using smaller incisions are becoming more common for certain deformities, potentially offering faster recovery, but require specific training and instrumentation (1).
  • Postoperative Care: Varies depending on the procedure but usually involves a period of protected weight-bearing (often in a special shoe or boot), elevation, ice, pain management, and eventually physical therapy. Full recovery can take several months (1, 7). Potential complications exist, including recurrence, stiffness, infection, nerve injury, and nonunion/malunion of osteotomies.

Choosing the right surgical procedure and meticulous execution are crucial for successful outcomes.

Differential Diagnosis

Pain around the first MTPJ can also be caused by (1, 8):

Condition Key Differentiating Features
Gout Acute, severe onset of intense pain, redness, swelling, often affecting the first MTPJ (podagra). Associated with hyperuricemia. Diagnosis confirmed by finding urate crystals in joint fluid.
Hallux Rigidus/Limitus Osteoarthritis primarily affecting the first MTPJ, leading to stiffness (especially limited dorsiflexion) and pain. May have dorsal bunion (bump on top). Hallux valgus deformity may be minimal or absent.
Sesamoiditis Inflammation or fracture of the small sesamoid bones under the first metatarsal head. Pain localized directly beneath the MTPJ, worse with push-off or toe extension.
Septic Arthritis Infection within the joint. Acute onset of severe pain, swelling, redness, warmth, inability to bear weight, often with fever. Requires urgent joint fluid aspiration.
Turf Toe Sprain of the ligaments around the first MTPJ, usually due to hyperextension injury. Acute pain, swelling, limited motion.
Adventitial Bursitis Inflammation of the bursa over the medial eminence (bunion) without significant underlying joint deformity initially. Pain and swelling localized to the bump.

References

  1. Coughlin MJ, Jones CP. Hallux valgus: demographics, etiology, and radiographic assessment. Foot Ankle Int. 2007;28(7):759-777. doi:10.3113/FAI.2007.0759
  2. Dayton P (Ed). Evidence-Based Bunion Surgery: A Critical Examination of Current and Emerging Concepts and Techniques. Springer; 2018. (Comprehensive overview)
  3. Ferrari J, Higgins JP, Prior TD. Interventions for treating hallux valgus (bunions) and simple bunions. Cochrane Database Syst Rev. 2004;(1):CD000964. doi:10.1002/14651858.CD000964.pub2 (Older review, context)
  4. Cho NH, Kim S, Kwon DJ, Kim HA. The prevalence of hallux valgus and its association with foot pain and function in a rural Korean community. J Bone Joint Surg Br. 2009;91(4):494-498. doi:10.1302/0301-620X.91B4.21920
  5. Smith RW, Reynolds JC, Stewart MJ. Hallux valgus assessment: report of research committee of American Orthopaedic Foot and Ankle Society. Foot Ankle. 1984;5(2):92-103. doi:10.1177/107110078400500209 (Classic reference for angles)
  6. Torkki M, Malmivaara A, Seitsalo S, Hoikka V, Laippala P, Paavolainen P. Surgery vs orthosis vs watchful waiting for hallux valgus: a randomized controlled trial. JAMA. 2001;285(19):2474-2480. doi:10.1001/jama.285.19.2474
  7. Robinson AH, Limbers JP. Modern concepts in the treatment of hallux valgus. J Bone Joint Surg Br. 2005;87(8):1038-1045. doi:10.1302/0301-620X.87B8.16467
  8. Shurnas PS. Hallux rigidus: etiology, biomechanics, and nonoperative treatment. Foot Ankle Clin. 2009;14(1):1-8. doi:10.1016/j.fcl.2008.11.001 (Differential diagnosis context)