A Bunion deformity refers to the enlargement of the first MPJ or metatarsophalangeal joint. This occurs when the big toe or hallux moves out of alignment in relation to the 1st Metatarsal. Podiatrists call this an HAV or Hallux Abducto Valgus, which refers to the anatomical position of the hallux, ie;- the hallux becomes abducted and externally rotated.

Initially the bunion represents the bony prominence of the 1st Met head as the hallux is abducted towards the second toe.

Over time bony changes or osteophytic growths occur at the margins of the joint and at the medial prominence of the 1st Met head, due to constant irritation.

The hallux becomes increasingly abducted, sometimes forcing the 2nd toe to over-ride the hallux.

Progressive degeneration or osteoarthritis occurs at the 1st MPJ, joint margins, and medial or dorsomedial bony prominence of the 1st Met head.

Tendons, ligaments, and sesamoid bones also become laterally deviated. The 3rd, 4th, and 5th toes become clawed and deviate laterally. The medial prominence of the 1st Met head can also develop a bursa or fluid sac under the skin of the bony prominence when subject to friction or shoe pressure.

Causes:

1/- Tight Footwear that squeeze the toes together can be a contributing factor, (as seen by the photo above showing a pointed fashion shoe versus the width of the owner’s foot)

2/- Hereditary…..although bunions are not directly inherited, foot shape, biomechanics, ligamentous laxity, are definitely inherited.

3/- Foot Structure. If the angle between the 1st and 2nd Metatarsals is greater than 10 – 15 degrees, the chance of developing HAV is far greater.

4/- Biomechanics of the Feet Instability of the hallux at the 1st MPJ can be a result of foot pronation. Pronation is a word that describes the position and motion that occurs at the heel joint and midfoot joints resulting in the overall effect of;- – internal leg rotation – collapse of the arch (eversion) – and abduction of the forefoot. Pronation also causes loss of function of the peroneus longus muscle that stabilizes the 1st metatarsal and 1st MPJ joint, thus adding to the instability of the hallux during gait, particularly toe-off.

5/- Ligamentous Laxity is a term that describes the flexibility or the strength of the ligaments that support the bones of the feet. If ligaments are generally loose then gravitational and mechanical forces will easily over come mechanisms that support the foot and alignment of bones in relation to joint position, thus resulting in foot pronation.

6/- Tight Calf Muscles, ie; Gastrocnemius muscle, causes pronation during gait resulting excess pressure at the 1st Metatarsalphangeal joint.

Treatments;

  • 1/ Padding to cushion areas
  • 2/ Corns and Callus debridement
  • 3/ Footwear for support and width
  • 4/ Stretching shoe over site of pressure on bunion
  • 5/ Orthotic devices to limit pronation
  • 6/ Massage and mobilization
  • 7/ Exercises for feet to strengthen muscles
  • 8/ Calf stretching particularly gastrocnemius
  • 9/ Night splint to adduct hallux
  • 10/ Surgery to realign the 1st Met and hallux, remove bunion

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