A novel study reports that white men and women of European descent inherit common foot disorders, such as bunions (hallux valgus) and lesser toe deformities, including hammer or claw toe. Findings from the Framingham Foot Study - the first to estimate the heritability of foot disorders in humans - appear in Arthritis Care & Research, a journal published by Wiley on behalf of the American College of Rheumatology (ACR).
Previous studies show that as many as 60% of older adults have foot disorders which may limit mobility and reduce their quality of life. In fact, bunions affect 23% of individuals 18 to 65 years of age and 36% of those over 65 years according to a study by Nix et al. While experts suggest that women, older adults and those with a higher body mass index (BMI) are at greater risk for foot disorders, there is little understanding of the genetics involved in their development.
The study, led by Arthritis Care & Research Editor-in-Chief, Dr. Marian Hannan from Hebrew SeniorLife and Harvard Medical School in Boston, Mass, included 1,370 participants enrolled in the Framingham Foot Study. Participants had a mean age of 66 years and 57% were female. Foot exams to identify hallux valgus, lesser toe deformities and plantar soft tissue atrophy were conducted between 2002 and 2008. The team estimated heritability using software that performs genetic analyses of familial data (pedigree structures).
Results show the prevalence of bunions, lesser toe deformities and plantar soft tissue atrophy was 31%, 30% and 28%, respectively. Hallux valgus and lesser toe deformity, two of the most common structural foot disorders that affect up to half of older adults in the U.S. and Europe, were found to be highly heritable depending on age and sex. The team reports that plantar soft tissue atrophy did not demonstrate significant heritability in the study cohort.
“Our study is the largest investigation of the heritability of common foot disorders in older adults, confirming that bunions and lesser toe deformities are highly inheritable in Caucasian men and women of European descent,” concludes Dr. Hannan. “These new findings highlight the importance of furthering our understanding of what causes greater susceptibility to these foot conditions, as knowing more about the pathway may ultimately lead to early prevention or early treatment.”
The Framingham Foot Study was funded in part by grants from the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS R01AR047853) and supported by the National Heart, Lung and Blood Institute’s Framingham Heart Study.
Common Foot Disorders
Evaluation begins by taking a thorough history which includes questions regarding the quality, location, radiation, severity, duration, and exacerbating and/or relieving factors related to the pain. A family history of congenital or acquired disorders of the foot should be sought. Additional information should include a history of previous injuries, occupational and recreational activities, and any recent changes in the type or amount of activity. The physician should also inquire about the effectiveness of current or previous treatment(s). Observation of the patient’s gait and foot position and inspection of his/her footwear should be performed since tight fitting shoes may exacerbate the foot condition, and modifications may prevent further injury.
Bunion is derived from the Latin word meaning turnip. It is a bursa sac that develops over the first metatarsophalangeal (MTP) joint as a result of a hallux valgus deformity of this joint. Hallux valgus refers to the lateral deviation of the first toe. However, in common parlance, “bunion” has come to denote any bump or associated deformity of the first MTP joint with deviation of the lateral great toe. Bunions can be primary in the absence of any known underlying diseases or secondary to a variety of metabolic, structural or inflammatory disorders.
The pathophysiology of bunions is poorly understood, but is thought to be secondary to both hereditary and environmental factors. The fact that bunions occur commonly in families suggests a genetic predisposition from ligamentous laxity and hyperpronation of the foot. The higher incidence in women compared to men is believed to be due to tightly fitting women’s footwear. However, footwear alone is not sufficient to explain this condition. The complex relationship of the first ray biomechanics and hindfoot mechanics influence bunion development. Additionally, any disorder resulting in first MTP joint inflammation may weaken MTP soft tissue restraints, predisposing to bunion formation.
The pain associated with a bunion is caused by pressure and frictional force exerted on the skin, soft tissue, and bursa at the medial prominence of the first MTP joint. Over time, callous formation and progression of the foot deformity cause internal subluxation with abnormal mechanics resulting in articular deterioration. A painful callous may also occur under the lateral subluxed medial sesamoid. Additionally, changes in the biomechanics of the foot result in an imbalance which causes the patient to shift his/her weight laterally and, in turn, increases pressure and pain at the head of the metatarsals (metatarsalgia). Progressive lateral great toe deviation produces a retrograde load on the first metatarsal, which deviates medially allowing for great toe shifting, and begins a vicious cycle. Subsequently, the great toe may either override the second toe or, more commonly, go beneath the second toe. Elevation of the second toe may result in significant second MTP joint pain and a hammer toe deformity of the second toe. Frequently, the hammer toe may be the greater source of discomfort. Relief of hammer toe pain may require addressing an associated bunion deformity simultaneously.
Asad Ayub, MD, Steven H. Yale, MD, and Christopher Bibbo, DO
Full citation: “Hallux Valgus and Lesser Toe Deformities are Highly Heritable in Adult Men and Women: the Framingham Foot Study.” Marian T. Hannan, Hylton B. Menz, Joanne M. Jordan, L. Adrienne Cupples, Chia-Ho Cheng and Yi-Hsiang Hsu. Arthritis Care and Research; Published Online: May 20, 2013 (DOI: 10.1002/acr.22040).
What is a bunion?
People think of a bunion as being as a bump on the side of the foot near the big toe. However, bunions go deeper than what we can see. Although the skin might be red, a bunion actually reflects a change in the anatomy of the foot.
Bunions happen over time. What begins as the big toe pointing toward the second toe ends up as changes in the actual alignment of the bones in the foot.
There is also a condition called tailor’s bunion or bunionette. This type of bump differs from a bunion in terms of the location. A tailor’s bunion is found near the base of the little toe on the outside of the foot.
What are the symptoms of bunions?
Many people do not experience symptoms in the early stages of bunion formation. Symptoms are often most noticeable when the bunion gets worse and with certain types of footwear. These include shoes that crowd the toes and/or high-heeled shoes. When symptoms do occur, they may include:
Physical discomfort or pain
A burning feeling
Redness and swelling
What causes bunions?
Bunions may be hereditary, as they often run in families. This suggests that people may inherit a faulty foot shape. In addition, footwear that does not fit properly may cause bunions. Bunions are made worse by tight, poorly-fitting, or too-small shoes. Bunions may also happen due to inflammatory conditions such as arthritis.
Who gets bunions?
Anyone can get bunions, but they are more common in women. People with flat feet are also more likely to get bunions due to the changes in the foot caused by bunions.
There is also a condition called adolescent bunion, which tends to occur in 10-to-15-year old girls.
How are bunions diagnosed?
Generally, observation is adequate to diagnose a bunion, as the bump is obvious on the side of the foot or base of the big toe. However, your physician may order X-rays that will show the extent of the deformity of the foot.
About the Journal
Arthritis Care & Research is an official journal of the American College of Rheumatology (ACR), and the Association of Rheumatology Health Professionals (ARHP), a division of the College. Arthritis Care & Research is a peer-reviewed journal that publishes both original research and review articles that promote excellence in the clinical practice of rheumatology. Relevant to the care of individuals with arthritis and related disorders, major topics are evidence-based practice studies, clinical problems, practice guidelines, health care economics, health care policy, educational, social, and public health issues, and future trends in rheumatology practice. The journal is published by Wiley on behalf of the ACR.
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