If you don’t work with feet, have not had the problem yourself or you don’t own a racehorse you may not know much about some little bones that we all have, called sesamoid bones. They are bones that lie within tendons, the largest being the patella(knee cap).
Under the big toe, there are two sesamoids which normally sit happily in the Flexor hallucis brevis (FHB) tendon and never let you know that they even exist. Sesamoid bones are said to resemble sesame seeds but actually look more like a pistachio nut split down the middle.
These bones can break as a result of trauma and can break as a result of repetitive impact and present as a stress fracture. They also have a nasty habit of spontaneously dying (avascular necrosis) and sometimes they are congenitally in two or three pieces (bi or tri-partite sesamoids).
All of these conditions can cause pain which feels like walking on a small piece of gravel, which can be extremely unpleasant, particularly as it happens with each and every step.
This month’s case relates to a thirty-year-old male who presented in 2020 with a 17-year history of intermittent pain under the first MTP (big toe) joint of his left foot. In the past year the pain had become intrusive and was preventing this man from working as a furniture restorer.
He had exquisite tenderness under the medial sesamoid and no other pain elsewhere. An X-ray of both feet showed bilateral bipartite medial sesamoids, the left being symptomatic whilst the right was completely pain-free.
A SPECT scan revealed intense activity in the medial sesamoid (Photo 1) and the lateral sesamoid was found to be bipartite but not associated with abnormal uptake (Photo 2).
It was decided to remove the medial sesamoid bone under a general anaesthetic. This was performed in August 2020 once the operating theatres had re-opened after the first pandemic lockdown.
This was uneventful surgery and by September he was more comfortable walking than he had been for years. At eight months he re-appeared, after another lockdown, with a return of his symptoms. This time the lateral sesamoid was painful.
A repeat SPECT scan showed that his lateral sesamoid had become metabolically active acting much in the same way that the medial one had done for so many years (photo 3).
Despite off-loading and rest the pain persisted. He was told that the lateral sesamoid needed to be removed to rid him of his pain. He was suspicious that something had been incorrectly done at the first operation and sought two further opinions.
The consensus was that the lateral sesamoid had spontaneously become very inflamed and that his only option, other than to live with the pain, was to have it excised. Removing both sesamoids can lead to a painful claw toe deformity so meticulous care was taken to preserve the FHB tendon and the lateral sesamoid was excised in November 2021.
At the final follow-up almost five months after surgery he has not developed a claw toe and his foot is finally pain-free.
This case highlights my saying that “there is no part of the human body that is so small that it can’t cause you a lot of pain”. If you don’t believe me, think about the misery that a small gallstone or kidney stone can produce. If someone complains of pain like “walking on a small stone under the big toe”, the diagnosis will involve sesamoid pathology 99% of the time. This case highlights that sesamoids reserve the right to make their presence felt at any time they choose to do so. In view of the fact that this patient had very tight calves, and tight calves increase the pressure under the sesamoids, I also carried out bilateral calf releases to reduce the risk of further over-load problems on the left but also to reduce the risk of the same problem developing on the right.
I very much hope he does not develop problems with the right foot but it would not surprise me if he ends up having further sesamoid problems in the future.