Human Locomotion

Cakar et al. Validity and reliability of hallux valgus angle measurement on smartphone digital photographs. J Foot Ankle Research (2023) 16:70.

Monthly Research Articles

I like this article because it shows that downloading the Anglemeter app onto your iPhone allows you to take photographs of your patients’ bunions and measure their hallux valgus angle. This is important as it allows you to monitor progress for specific interventions when attempting to reduce the size of bunions. The authors evaluated reliability of 2 specific smart phone measurements and determined that they had excellent inter- and intrarater reliability, with ICC values over .9. The only downside was that the Apple iPhone measurements, although reliable, tended to underestimate the hallux valgus angle. Interestingly, the authors attributed to mismeasurement to a possible methodological flaw in their study: they took the photo with the camera angled 20° from the front of the foot, and they suggest that they might have had better outcomes if they took the measurements directly over the top of the foot. They also point out that compared to actual bony anatomy, conventional x-rays mismeasure the degree of hallux valgus by as much as 6.5°, which is a big deal since this measurement is used to determine whether or not someone gets surgery. When you consider that one in 6 people who get surgery for bunions have bad outcomes (1), the large measurement error associated with x-rays is unacceptable, not to mention that X-rays are expensive. I’ve used the Anglemeter app for other measurements, such as monitoring progress for the restoration of knee flexion following total knee replacement. Additionally, some great research came out of Thailand showing that when people with bunions wear silicone toe separators between their first and second toe while they sleep, they significantly reduced the size of their bunions (2). This Anglemeter app allows you to measure progress, because it’s been proven to be reliable, you can trust subsequent measurements.

  1. Okuda R, et al. Hallux valgus angle as a predictor of recurrence following proximal metatarsal osteotomy. J Orthop Sci. 2011 Nov;16:760-4.
  2. Chadchavalpanichaya N, et al. Effectiveness of the custom-mold room temperature vulcanizing silicone toe separator on hallux valgus: a prospective, randomized single-blinded controlled trial. Prosthetics Orthotics Int. 2018 Apr;42:163-70.