When the bony structure is located at a distance of less than 3 mm, there is normally a fibrotic attachment to the navicular tuberosity, and thus represents a true accessory ossicle. They demonstrated that when this structure is separated 3 mm or more from the tuberosity, there is no fibrotic connection to the navicular tuberosity and therefore the finding can be considered a sesamoid. The distinction between the cases in which this represents a true accessory ossicle versus a sesamoid has been made in the literature, in a cadaveric study by Bareither et al. Interestingly, the os tibiale externum has been commonly described as a sesamoid in the literature, which represents a different concept from an accessory ossicle. Type I accessory navicular are usually asymptomatic (Fig. Its prevalence is approximately 30% and represents the classically known os tibiale externum. They may be seen separated to up to 5 mm from the navicular tuberosity. In some cases, there are several of them (multiple configuration). The type I is an oval or round small ossified structure, located within the tibialis posterior tendon. The accessory navicular is located adjacent to the postero-medial tuberosity of the bone, and three different configurations exist. The accessory navicular is also known as the os tibiale, os tibiale externum, or naviculare secundarium.Įstimated prevalence has been set in between 4 and 21%. Our aim with this review is to illustrate the imaging findings related to the presence of accessory ossicles and muscles in the ankle and foot through different techniques, with special attention to those variants that associate factors of clinical relevance or, in the case of the ossicles, would pose a challenge in the differential with fractures.īone coalitions, given their complexity and frequent clinical implications, deserve separate analysis and will not be the object of this review. However, they may also eventually represent a source of pathology, giving rise to painful syndromes, degenerative changes, be the subject of overuse and trauma, or appear as masses and cause compression syndromes or impingement. Īccessory ossicles and muscles are also generally asymptomatic, and discovered incidentally on imaging studies. Regarding accessory sesamoid bones, the os peroneum is the most frequently found.

The most common accessory ossicles in the ankle and foot are the os trigonum, the accessory navicular (among the different three types, type II is the most common), and the os intermetatarseum, in this order. They functionally represent components of a gliding mechanism and are at least partially embedded in tendons, reducing friction and protecting the tendon structure. Sesamoid bones have a different anatomical nature. They are seen as subdivisions of existing bones or free elements in vicinity of the normal bone structures. Īccessory ossicles in most cases are a result of unfused ossification centers. Most of them represent developmental abnormalities that constitute incidental radiographic findings. These findings are subject to a lot of variation. These include accessory ossicles, additional sesamoid bones, variations in number and configuration of sesamoid bones, coalitions, bipartitions, and variants in the soft tissues, such as accessory muscles. Eponymythology of foot injuries.A number of anatomical variations can be found in the ankle and foot. Ahmed AA, Kandil MI, Tabl EA, Elgazzar AS.Management of Müller-Weiss Disease In: Avascular necrosis of the foot and ankle. Earliest Probable Case of Mueller-Weiss Disease From Ancient Egypt. Chiavegatti R, Canales P, Saldias E, Isidro A.Mueller-Weiss syndrome: imaging and implications. Müller-Weiss disease – review of current knowledge. Müller-Weiss disease: clinical and biomechanical features. Fortschritte auf dem Gebiete der Röntgenstrahlen, 1929 40: 63-67. Über die “Malazie” des Os naviculare pedis. Fortschritte auf dem Gebiete der Röntgenstrahlen 1928 37: 38–42. Über eine typische Gestaltsveränderung beim Os naviculare pedis und ihre klinische Bedeutung. Deutsche Zeitschrift für Chirurgie, 1927 201: 84-87. Über eine eigenartige doppelseitige Veränderung des Os naviculare pedis beim Erwachsenen. Köhler’sche Krankheit des Kahnbeins beider Füße in Verbindung mit pluriglandulärer Insuffizienz und als Ursache von Pes adducts.

Dorsal navicular