August 2021, Volume 71, Issue 8

IMAGING CORNER

Symptomatic Os Navicular on 99mTc-MDP SPECT/CT

Sharjeel Usmani  ( Department of Nuclear Medicine, Kuwait Cancer Control Center (KCCC), Khaitan, Kuwait. )
Raghda Awad Al-khaldi  ( Department of Nuclear Medicine, Kuwait Cancer Control Centre (KCCC), Khaitan Kuwait. )
Anwar al Banna  ( Department of Nuclear Medicine, Kuwait Cancer Control Centre (KCCC), Khaitan Kuwait. )
Fareeda Al-Kandari  ( Department of Nuclear Medicine, Kuwait Cancer Control Centre (KCCC), Khaitan, Kuwait. )

Abstract

Os navicular bone is an accessory bone of the foot, which is mainly found on the medial side of the proximal navicular bone. Os navicular bone may be symptomatic and cause medial foot pain. We report a case of a 42-year-old athlete male having right foot pain diagnosed with os navicular syndrome on 99mTc-MDP bone scintigraphy SPECT/CT. We emphasize on the use of SPECT/CT in not only allocating the ossicle anatomically, but also for the purpose of evaluating an active source of pain in a region of multiple complex small bones.

Key Words: 99mTc-MDP SPECT-CT · Os navicular · foot pain.

 

Case Discussion

 

A 43-year-old athlete underwent whole body 99mTc-HDP bone scan for right foot pain. SPECT-CT images showed focal increased radiotracer uptake in articular surface between the right navicular bone and a Type-II accessary os naviculare. Correlation of clinical and scan findings suggested right painful accessory os syndrome.

Os navicular bone is an accessory bone of the foot, usually located on the medial side of the proximal navicular bone and in continuity with tibialis posterior tendon. Its incidence is 6-12%. There are three reported types. Type-I, small sesamoid bone located within posterior tibial tendon. Type-II, a triangular unfused accessory ossification center which is separated from the tuberosity by a narrow synchondrosis. Type-III, a prominent tuberosity, likely a fused type-II accessory navicular bone.1 Type-II and III are mostly symptomatic and associated with pain. The mechanism of pain in accessory navicular has been attributed to traumatic or degenerative changes at the synchondrosis or to soft-tissue inflammation.

Type-II accessory navicular bone can be symptomatic causing medial foot pain. Plain radiographs are usually not helpful in diagnosis. MRI scan findings include persistent oedema pattern in the accessory navicular bone and within the synchondrosis.2 Three-phase bone scan is indicated to see if the accessory navicular bone is the cause of symptoms. SPECT-CT is reportedly useful for localizing active disease in foot and ankle pathology.3 Few studies also highlight the significance of SPECT/CT in symptomatic accessory bones.4 This case highlights the importance of hybrid imaging in the evaluation of symptomatic accessory navicular bone.

 

References

 

1.      Miller TT. Painful accessory bones of the foot. Semin Musculoskelet Radiol. 2002;6:153–161.

2.      Choi YS, Lee KT, Kang HS, Kim EK. MR imaging findings of painful type II accessory navicular bone: Correlation with surgical and pathologic studies. Korean J Radiol. 2004;5:274–9.

3.      Mohan HK, Gnanasegaran G, Vijayanathan S, et al. SPECT/CT in imaging foot and ankle pathology-the demise of other coregistration techniques. Semin Nucl Med. 2010; 40:41–51.

4       Usmani S, Essa NB, Marafi F, Rasheed R, Al Kandari F. The Utility of Tc-99m Hydroxymethylene Diphosphonate Single-photon Emission Computed Tomography/Computed Tomography in Symptomatic Os Trigonum. Indian J Nucl Med. 2018;33:177-179.

 

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