Easing Bunions Without Surgery: The First-of-its-kind Medical Shoe Engineered at KU

bunion
Design project from three KU students promises a non-surgical approach to treating one of the most common foot complaints.

It is estimated that over 48,000 people in the UAE suffer from bunions, a common ailment of the foot. A bunion is a bony prominence from the misalignment of the metatarsal phalangeal joint (the joint at the base of the big toe) causing the toe to point outward and rotate towards the smaller toes, medically known as hallux valgus deformity. While the precise cause is not known, it is believed that bunions are caused by multiple factors including abnormal foot function and mechanics, such as over-pronation, abnormal anatomy at the joint, and genetic factors.

Abdulaziz Alzurahi, Researcher and Lab Manufacturing Assistant at KU and founder of the Bio-Mechanics STAR Online Research Center, guided Aishah Saeed Alzeyoudi and Maitha Mohamed Alhajeri, both Biomedical Engineering graduate students, on a project to investigate the causes of bunions and a non-surgical intervention method as part of the Biomedical Engineering course, supervised by Dr. Kinda Khalaf, Associate Chair in the Department of Biomedical Engineering.

“Hallux valgus is one of the most common deformities of the forefoot, with a prevalence rate of 23 to 35 percent globally,” said Alzurahi. “To determine potential causes, we conducted a survey to estimate the prevalence in the UAE and analyzed gait cycles among volunteers. We found that the survey was inconclusive but the gait analysis found people with bunions did have an abnormal gait compared to control.”

Aside from vanity issues, bunions can be very painful for sufferers. The most common symptom is a hard lump on the side of the foot which often leads to the big toe pointing towards the other toes — or even overlapping them — and hard, red or swollen skin over the lump. People may also have pain along the side or bottom of the foot, which is usually worse when wearing shoes and walking. Most shoes can’t accommodate the protrusion — particularly the high heels and pointed-toe shoes favored by many women — and so put pressure on the misaligned joint, eventually causing inflammation and even arthritis.

To judge how severe a bunion is, clinicians will x-ray and measure the angles between the bones in the foot. The hallux valgus angle is of particular interest as it is the angle between the first metatarsal bone and the big toe, and the intermetatarsal angle between the first and second metatarsals. Bunions range from mild to severe but all need attention: the metatarsal phalangeal joint (MTP) helps bear and distribute weight and a bunion at this joint can seriously impair the foot’s functioning.

In most cases, bunions are treated without surgery to reduce pain and keep the bunion from worsening, but the only way to remove a bunion is surgery.

Surgery is an invasive and drastic course of action, involving an intense and long recovery period. Studies suggest that 85 to 90 percent of patients are satisfied with their results but one review found that about a third of patients were dissatisfied even when their pain and toe alignment improved. This may be due to unrealistic expectations of perfectly straight big toes and underestimating the recovery period.

In most cases, however, it is possible to intervene before surgery is required.

“The non-surgical approach to treating bunions involves several treatments such as toe spacers, well-fitting shoes, walking barefoot, and physiotherapy,” said Alzurahi. “We designed a shoe that can help treat bunions effectively to reduce the need for surgical intervention. Our team met a podiatrist in Abu Dhabi to evaluate our design and I visited an orthopedic surgeon to gain a surgeon’s point of view on design enhancements.”

The result is a medical shoe using toe separators as novel aligners inside the shoe for automatic load generation to the toes — applying an opposite direction force to the toe and bringing it to its normal position over time. The aligners are changed on a bi-weekly basis until normal bone curvature is achieved.

“Our initial design followed the same concept of the invisalign technology used by orthodontists to fix misaligned teeth,” said Alzurahi. “We proposed having curved aligners on the side of the bunion to apply a compressive force until the bone is back in its normal position. However, after consulting the experts, we realized this would make the disorder much worse than we thought, so we changed our approach to apply a dislocation movement to the toe instead.”

The aligners create an opposite force reaction to the toes in contact inside the shoe. The magnitude of the force is related to the width of the aligner: the wider the aligner, the more force is created. The team designed three toe spacer sizes to apply different levels of pressure. They plan to improve their design using sensors to change the width of the aligners automatically according to a predetermined therapy plan. The team also plans to improve the materials used to make the shoes more comfortable for patients and reduce the weight of the shoe to allow patients to wear them for longer.

“This is one of the best research case studies on bunions,” added Alzurahi. “I am so proud and glad to be part of this one-of-a-kind study. It was great to initiate this research in the UAE, with a special visit from my side to an orthopedic surgeon who was very impressed by the concept. Until now, we haven’t seen a shoe like this and having a team comprising engineers and medical doctors allowed us to reach a first-of-its-kind prototype design.”