An exercise program improves foot alignment in people with flexible flat foot
An exercise program to correct a flatfoot for 6 weeks was able to improve navicular drop height
The intervention performed short foot musculature and gluteal exercises and improved more than the group not performing these
The medial longitudinal arch angle equally improved, leading to “an improved cosmetic appearance of the foot and reduced progression towards more severe flat foot”
Introduction
The foot has to bear a lot of weight in everyday life. Therefore, the structure and dynamics of the foot arches are essential for a properly functioning foot. Consider shock absorption, body weight transfer, forward propulsion, and providing a base of support. When the medial longitudinal arch flattens, the medial edge of the foot is (almost completely) in contact with the ground. There are many causes, beyond the scope of this review. But importantly, the presence of a flatfoot can be reversible or fixed. A reversible flatfoot loses the medial longitudinal arch during closed-chain, but this arch is retained in non-weight-bearing conditions. Because of the foot’s close relationship through the kinematic chain to the knee and hip, a flatfoot can lead to other problems higher up the kinetic chain. Orthopedic soles can provide relief, but can an active exercise program to correct a flatfoot help?
Methods
To examine the extent to which an exercise program can correct a reversible flatfoot, this trial was conducted. The randomized controlled trial was conducted in the Orthopaedic Physiotherapy Department of the Pravara Institute of Medical Sciences. A flexible flat foot was defined as a foot with a navicular drop height of more than 10mm and a medial longitudinal arch angle of less than 130°. This angle was calculated by centering the goniometer at the navicular tuberosity and the ends of the goniometer following the head of the first metatarsal and the medial malleolus. To perform the navicular drop test, the following video can help you out:
The experimental group performed 6 weeks of active exercises 3 times per week. The exercises consisted of active plantar and dorsiflexion, 4 short foot muscle exercises, gluteal strengthening, and calf stretches. The exercises progressed after 2 weeks by varying the position in which the exercises were performed and/or by increasing the number of repetitions or the duration of the hold times.
The control group equally participated in a 6-week with 3 sessions per week program but only performed active plantar and dorsiflexion exercises and a calf stretch in long sitting.
The outcomes were assessed by measuring the height of the medial longitudinal arch using the navicular drop test. Also, the medial longitudinal arch angle was measured.
Results
So, can an exercise program correct a reversible flatfoot? To answer this question 52 adults between 18 and 21 years with a flexible flat foot were included. The groups were comparable at baseline, as can be seen in the table hereunder.
The results indicated that in both groups the navicular drop height improved. The mean between-group difference however favored the intervention by showing a 0.4 cm greater reduction in navicular drop height. The authors reported that this difference was a very precise estimate as the confidence interval only ranged from 0.4 to 0.5. The same was seen for the medial longitudinal arch angle. In the intervention group it increased (and thus improved) by 16 degrees more compared to the control group. Here also, the estimate was precise as the confidence interval ranged from 13-19.
Questions and thoughts
The authors stated that “it was difficult to nominate the smallest worthwhile effect for the two outcome measures in this study because they were purely biomechanical rather than symptomatic or functional measures about which patients might have been able to give an opinion on the clinical worth of improvement of various magnitudes.
Furthermore, Nielsen et al. in 2009 examined the relation of drop height with BMI, gender, and foot length. They found that foot length had a significant influence on the navicular drop in both men and women. Per 10 mm increase in foot length, the navicular drop increased by 0.40 mm for males and 0.31 mm for females. This led to a proposed cut-off value of 8.5 mm to distinguish between a normal navicular drop and an abnormal navicular drop as 97.5% of this study’s sample had a dynamic navicular drop of less than 8.5mm. But as the foot length influenced the drop, the upper limits of the confidence interval increased from 7.25mm to 9.50mm for males and from 7.8mm to 10mm for females. Therefore we have to consider the length of the foot in the judgment of the extent of the navicular drop. For short feet (around 22 cm), we could use the cut-off of 8.5, but longer feet may still have a normal navicular drop at around 10mm. Unfortunately, foot length was not measured in this study. However, the participants are the same, so this could not have influenced the findings.
Talk nerdy to me
The primary outcome of this study was not specified. Furthermore, no sample size was calculated and the trial was not recorded. This constitutes an important limitation. Without a registered trial, we cannot say whether all predefined outcomes were reported in this publication or whether this paper selectively represented some outcomes. Since the sample size was not pre-calculated, we do not know whether the included population was sufficient to detect true differences. Nevertheless, the authors point to the finding of very accurate treatment effect estimates. There was no mention of patients’ adherence to their exercise program. Thus, we cannot know with certainty whether the improvements were truly attributable to the intervention itself. Perhaps those in the control intervention were not very compliant. The authors did not report the results based on statistical significance, which is good. But other than stating that the results were analyzed on an intention-to-treat basis, very little information was provided about the statistical analysis plan.
Take home messages
This trial indicated an improvement in navicular drop height in both groups. As such, an exercise program to correct a flatfoot can be established. The mean between-group difference however favored the intervention by showing a 0.4 cm greater reduction in navicular drop height. The same was seen for the medial longitudinal arch angle. The authors reported that these differences were very precise estimates. However, the trial hadn’t been registered and no sample size calculation was performed, so this could have influenced the results reported here.
Reference
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