Analysis of Nonweightbearing MRI Fat Pad Thickness Under Central Metatarsals in Patients With and Without Metatarsalgia

Background: Metatarsalgia is a common diagnosis for patients with forefoot pain. Many have proposed metatarsal fat pad atrophy is a cause of metatarsalgia and therefore have suggested fat grafting instead of distal metatarsal osteotomies to treat metatarsalgia. For fat grafting to be a viable treatment, fat pad atrophy should correlate with metatarsalgia. This study looked to determine the relationship between metatarsal fat pad thickness and metatarsalgia and the correlation between metatarsal fat pad thickness and patient-reported outcomes. Methods: We conducted a retrospective review of patients with metatarsalgia and those with foot or ankle osteoarthritis who had a nonweightbearing MRI performed between February 1, 2021, and March 1, 2023. Data collected included demographics, PROMIS scores, metatarsal fat pad thickness in the second and third rays of the affected foot, and thinnest area on coronal section, measured on MRI. Student t test was used to compare continuous variables, whereas the χ2 test was used to compare categorical variables. Multivariable linear regression models were used to control for potential confounding factors. Results: A total of 112 patients were included in this study. Patients with metatarsalgia were significantly more likely to have a lower body mass index (29.3 vs 32.0, P = .03) than patients with osteoarthritis, but this finding was not present when controlling for confounding variables. We found no significant difference in fat pad thickness between patients with metatarsalgia vs patients with foot or ankle osteoarthritis (P = .43). We found no correlation between metatarsal fat pad thickness and pain interference (P = .59), physical function (P = .64), or mobility (P = .94) PROMIS scores. Conclusion: In this retrospective comparative study of a relatively small cohort we found no significant difference in metatarsal fat pad thickness for patients with metatarsalgia vs patients with foot and ankle osteoarthritis based on nonweightbearing MRI, and no association between metatarsal fat pad thickness and patient-reported outcomes. Level of Evidence: Level III, case control study.