https://www.youtube.com/watch?v=cYILrhUSjhw
This is a testimonial from David who underwent removal of a damaged/fractured accessory bone behind the ankle known as an "Os Trigonum." David was involved

https://emedicine.medscape.com/article/85311-workup
Georgiannos D, Bisbinas I. Endoscopic Versus Open Excision of Os Trigonum for the Treatment of Posterior Ankle Impingement Syndrome in an Athletic Population: A Randomized Controlled Study With 5-Year Follow-up. ... David T Bernhardt, MD is a member of the following medical societies: American Academy of Pediatrics,

https://pubs.rsna.org/doi/full/10.1148/radiology.215.2.r00ma01497
In all patients, MR imaging demonstrated abnormal bone marrow signal intensity in the os trigonum and/or lateral talar tubercle, consistent with bone contusions. Two patients had a fragmented os trigonum or lateral tubercle, and two had a pseudoarthrosis of the posterolateral talus. ... David W.Kruse, YiannisKoutedakis, Islay M.Mcewan, Matthew

https://drdavidshepherd.com.au/all-conditions/os-trigonum-impingement/
Mr David Shepherd 03 9573 9679 33 The Avenue ... Os-trigonum Impingement. Other Conditions. Ankle Sprains. Painful Ankle inversion injury tearing the Lateral Ligaments of the Ankle. Read more Lateral Ligament Instability. Recurrent instability and pain following an ankle sprain.

https://ro.wikipedia.org/wiki/Osul_trigon
The os trigonum. Journal of Bone & Joint Surgery, British Volume 37.2 (1955): 257-265. ... Karasick, David, and Mark E. Schweitzer. The os trigonum syndrome: imaging features. AJR. American journal of roentgenology 166.1 (1996): 125-129. Armen S Kelikian, Shahan K. Sarrafian. Sarrafian's Anatomy of the Foot and Ankle: Descriptive, Topographic