Bunions

Bunions by David Webby

A Bunion deformity refers to the enlargement of the first MPJ or metatarsophalangeal joint. 

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

As the big toe moves towards the 2nd toe, bony changes or osteophytic growths occur at the margins of the joint over time, due to constant irritation. 

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

Tendons, ligaments, and sesamoid bones also become laterally deviated. The 3rd, 4th, and 5th toes can become clawed. 

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. 

Progressive degeneration or osteoarthritis occurs at the 1st MPJ, joint margins, including the 1st Met head. 

Causes:

1/- Tight Footwear that squeeze the toes together can be a contributing factor.

2/- Hereditary: Although bunions are not directly inherited, foot shape, biomechanics, ligamentous strength, 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/- Abnormal biomechanics of the feet / legs can result in abnormal forces and alignment at the big toe joint or 1st MPJ. This can be a result of excessive 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 big toe joint during gait. Jamming of the 1st Metatarsal can cause destruction of the cartilage at this joint, resulting in reduction in joint range of motion.

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 overcome mechanisms that support the foot and alignment of bones in relation to joint position, thus resulting in foot pronation. 

6/- Tight Calf Muscles, The Gastrocnemius muscle, which becomes part of the Achilles tendon, can cause foot pronation if there is insufficient flexibility of the muscles. 

Tight Calf muscles are a common condition. Because the muscles are very strong they cause the foot to pronate at the midfoot during gait in order to get extra dorsi-flexion at the ankle during gait.

If the muscles are tight then the foot is forced to pronate, thus causing pressure on the big toe joint and other structures of the feet.

Treatments:

It is best to get a thorough assessment by the Podiatrist to see if there are any contributing factors that may cause abnormal forces at the big toe joint, or other factors that contribute to the formation of the bunion.

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1/ Corns and Callus debridement 

2/ Orthotic devices to control foot pronation 

3/ Calf stretching to reduce foot pronation forces.

4/ Exercises for feet to strengthen muscles 

5/ Massage and mobilization

6/ Footwear to support foot posture, thus reduce foot pronation.

7/ Stretching shoe over site of pressure on bunion

8/ Padding to cushion areas 

9/ Night splint to adduct hallux 

10/ Surgery to realign the 1st Met and hallux, remove bunion 

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