Zumba is a dance fitness program that is a modern variant of aerobics. The program combines Latin and international music with dance in an effort to make exercise fun (if that is possible). There is a whole lot of body and foot movement, and generally one leaves a class with endorphins flooding your brain, or so I am told.
Like every activity, though, there is some risk of injury. In this case, a 28-year-old female presented to her podiatrist complaining of one year of great toe pain, recently increased with Zumba dancing. She was referred for an MRI.
An axial T1 image reveals fragmentation of the anterior aspect of the tibial sesamoid of the hallux (red arrows). The bone fragments are abnormally dark (compare with the normal signal intensity of the fibular sesamoid (green arrow):
Here is a magnification view of the same area:
An axial T2FS image reveals that the bone fragments remain dark, and are separated by a small amount of fluid:
A sagittal intermediate image again depicts the abnormally dark anterior half of the sesamoid (red arrow), and also depicts the proximal half of the sesamoid (yellow arrow), which remains normal in signal:
Thus, the anterior portion of the tibial sesamoid is fragmented and devascularized (avascular necrosis).
The sesamoid bones of the hallux (great toe) are embedded within the medial and lateral slips of the flexor hallucis brevis tendon at the level of the first metatarsal head. The sesamoids are usually unipartite, but there is a significant incidence of bipartite or multipartite sesamoids, especially in the case of the tibial sesamoid. Afflictions of the sesamoids include acute trauma and chronic increased stress, which can manifest as sesamoiditis, stress fractures, and osteonecrosis (avascular necrosis). The classic findings of avascular necrosis include pain and tenderness to palpation, with osseous fragmentation or mottling noted on conventional radiographs. On MRI, the marrow will be hypointense on both T1, T2FS and STIR images; in contradistinction, the marrow will be hyperintense on T2FS and STIR images in cases of sesamoiditis and stress fractures.
The great toe is a well-known stress point in ballet dancers, but can also be injured with less intense forms of dancing, such as Zumba.
Vic David MD