Os naviculare: the multi-ossicle configuration of a normal variant.
OBJECTIVE
To describe the multi-ossicle appearance of the os naviculare on MRI and CT examinations and to correlate this appearance with the published classification of this well-known skeletal variant.


METHODS
We retrospectively reviewed 148 patients, examined within a 2-year period (170 CT and MRI studies of the foot-ankle), for the presence of os naviculare. This variant was classified according to a widely used system (type I, II, III). In addition, each navicular variant was further reclassified according to the presence of one or more ossicles. The presence of bone marrow edema was also recorded.


RESULTS
Accessory navicular bone was identified in 34 cases (20%) of the 170 exams. It was detected in 14 male and 14 female patients with the following incidence: 11.15% type I (19 cases), 4.11% type II (7 cases) and 4.74% type III (8 cases). In six cases the location was bilateral. Among patients with os naviculare, a multi-ossicle appearance with a total incidence of 14.7% (8.8% two ossicle configuration and 5.9% three ossicle configuration) was observed. In two type II cases studied with MRI, there was bone marrow edema suggesting a painful pseudarthrosis.


CONCLUSIONS
The presence of multiple accessory navicular bone ossicles, not previously described with cross-sectional imaging, is reported herein. The pathogenesis and clinical relevance of this uncommon variant needs to be elucidated with further studies.
Perdikakis
Evangelos
E
Department of Radiology, University Hospital, Heraklion, Greece.
Grigoraki
Eleni
E
Karantanas
Apostolos
A
D005260:Female; D005528:Foot / Q000000981:diagnostic imaging*; D005532:Foot Deformities, Congenital / Q000000981:diagnostic imaging; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed
Foot Ankle Int. 1997 Feb;18(2):85-8
9043880
Clin Rheumatol. 2007 Dec;26(12):2143-2144
17486293
Am J Sports Med. 2005 Apr;33(4):531-5
15722276
Foot Ankle Int. 1995 Aug;16(8):500-3
8520663
Foot Ankle Int. 1999 Jan;20(1):53-4
9921775
AJR Am J Roentgenol. 2000 Sep;175(3):627-35
10954441
Semin Musculoskelet Radiol. 2002 Jun;6(2):153-61
12077704
Eur Radiol. 2003 Dec;13 Suppl 4:L164-77
15018183
Foot Ankle Int. 2004 Jan;25(1):27-30
14768961
Surg Radiol Anat. 2009 Nov;31(9):675-9
19367354
Foot Ankle. 1987 Dec;8(3):156-63
3440558
Skeletal Radiol. 1984;12(4):250-62
6239377
J Bone Joint Surg Am. 1997 Dec;79(12):1791-8
9409792
JBR-BTR. 2004 Sep-Oct;87(5):250-2
15587565
Clin Orthop Relat Res. 1979 Oct;(144):233-7
535230