Skeletal Radiology

, Volume 24, Issue 2, pp 111–115 | Cite as

Bone island (enostosis): current concept — a review

  • Adam Greenspan


An enostosis or bone island represents a focus of mature compact (cortical) bone within the cancellous bone (spongiosa). Thought by some to be a tumor-like condition and by others a hamartoma, this benign lesion is probably congenital or developmental in origin and reflects failure of resorption during endochondral ossification. A bone island can be virtually diagnosed based on its characteristic clinical and radiologic features. Typically asymptomatic, the lesion is usually an incidental finding, with a preference for the pelvis, femur, and other long bones, although it may be found anywhere in the skeleton, including the spine. Plain radiography reveals a homogeneously dense, sclerotic focus in the cancellous bone with distinctive radiating bony streaks (“thorny radiation”) that blend with the trabeculae of the host bone, creating a feathered or brush-like border. On CT scan, a bone island appears as a low-attenuation focus, and on MRI sequences it shows low signal intensity like cortical bone. A distinguishing feature of bone islands is that they are usually “cold” on skeletal scintigraphy. Thus, bone scan has been and continues to be the means of differentiating bone islands from the more aggressive entities. However, reports of histologically confirmed bone islands that were scintigraphically active have raised a note of caution about relying on this modality in the differential consideration of lesions otherwise characteristic of bone islands. Guides to the correct diagnosis should be looked for in the individual clinical situation and in the morphologic features of the lesion on plain radiography, CT, and MRI, without regard to the lesion's activity on bone scan. If such a lesion, however, is symptomatic and “hot” on scintigraphy, it demands close observation with follow-up imaging studies.

Key words

Developmental anomalies Bone, sclerosis Bone island Enostosis Scintigraphy 


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  1. 1.
    Stieda A. Ueber umschriebene Knochenverdichtungen in Bereich der Substantia spongiosa in Roentgenbildern. Bruns Beitr Klin Chir Tuebing 1905; 45: 700.Google Scholar
  2. 2.
    Fischer H. Contributions to information concerning variations of the skeleton. Fortschr Geb Roentgenstr 1912; 19: 43.Google Scholar
  3. 3.
    Steel HH. Calcified islands in medullary bone. J Bone Joint Surg [Am] 1950; 32-A: 405.Google Scholar
  4. 4.
    Meschan I. Normal variant sclerotic bone island. In: Mechan I, ed. Roentgen signs in clinical diagnosis. Philadelphia; Saunders, 1957: 256.Google Scholar
  5. 5.
    Caffey J. Focal sclerosis of spongiosa. In: Caffey J, ed. Pediatric X-ray diagnosis. Chicago: Year Book Medical, 1961: 842.Google Scholar
  6. 6.
    Schmorl G, Junghanns H. The human spine in health and disease, 2nd edn. New York: Grune and Stratton 1971: 327.Google Scholar
  7. 7.
    Hudson TM. Radiologic-pathologic correlation of musculoskeletal lesions. Baltimore: Williams & Wilkins, 1987: 31–33.Google Scholar
  8. 8.
    Resnick D, Kyriakos M, Greenway GD. Tumors and tumorlike lesions of bone: imaging and pathology of specific lesions. In: Resnick D, ed. Bone and joint imaging. Philadelphia: Saunders 1989: 1107.Google Scholar
  9. 9.
    Schajowicz F, Ackerman LV, Sissons HA. Histological typing of bone tumors. International histological classification of tumors. Geneva: World Health Organization, 1972.Google Scholar
  10. 10.
    Mirra JM, Picci P, Gold RH. Bone tumors: clinical, radiologic and pathologic correlations. Philadelphia: Lea & Febiger 1989: 182.Google Scholar
  11. 11.
    Greenspan A. Sclerosing bone dysplasias — a target-site approach. Skeletal Radiol 1991; 20: 561.Google Scholar
  12. 12.
    Greenspan A, Steiner G, Knutzon R. Bone island (enostosis): clinical significance and radiologic and pathologic correlations. Skeletal Radiol 1991; 20: 85.Google Scholar
  13. 13.
    Greenspan A. Sclerosing bone dysplasias. In: Taveras JM, Ferrucci JT, eds. Radiology — diagnosis, imaging, intervention, vol 5. Philadelphia; Lippincott 1993: 1–18.Google Scholar
  14. 14.
    Smith J. Giant bone islands. Radiology 1973; 107: 35.Google Scholar
  15. 15.
    Ngan H. Growing bone islands. Clin Radiol 1972; 23: 199.Google Scholar
  16. 16.
    Broderick TW, Resnick D, Georgen TG, Alazraki N. Enostosis of the spine. Spine 1978; 3: 167.Google Scholar
  17. 17.
    Epstein BS. The spine: a radiological text and atlas, 3rd edn. Philadelphia: Lea & Febiger, 1969.Google Scholar
  18. 18.
    Resnick D, Nemcek AA Jr, Haghighi P. Spinal enostoses (bone islands). Radiology 1983; 147: 373.PubMedGoogle Scholar
  19. 19.
    Onitsuka H. Roentgenologic aspects of bone islands. Radiology 1977; 123: 607.Google Scholar
  20. 20.
    Kim SK, Barry WF. Bone islands. Radiology 1968; 99: 77.Google Scholar
  21. 21.
    Kim SK, Barry WF. Bone island. AJR 1964; 92: 1301.Google Scholar
  22. 22.
    Gold RH, Mirra JM, Remotti F, Pignatti G. Case report 527. Skeletal Radiol 1989; 18: 129.Google Scholar
  23. 23.
    Sickles EA, Genant HK, Hoffer PB. Increased localization of 99mTc-pyrophosphate in a bone island: case report. J Nucl Med 1976; 17: 113.Google Scholar
  24. 24.
    Blank N, Lieber A. The significance of growing bone islands. Radiology 1985; 85: 508.Google Scholar
  25. 25.
    Go RT, El-Khoury GY, Wehbe MA. Radionuclide bone image in growing and stable bone island. Skeletal Radiol 1980; 5: 15.Google Scholar
  26. 26.
    Hoffman RR Jr, Campbell RE. Roentgenologic bone island instability in hyperparathyroidism. Radiology 1972; 103: 307.Google Scholar
  27. 27.
    Scheel W, Strauss B, Eger H. Kostale Kompaktainseln in der Differentialdiagnostik kleiner Rundherde of Thoraxübersichtsaufnahmen. Z Erkrank Atm Org 1985; 164: 299.Google Scholar
  28. 28.
    Davies JAK, Hall FM, Goldberg RP, Kasdon EJ. Positive bone scan in a bone island. J Bone Joint Surg [Am] 1979; 61-A: 943.Google Scholar
  29. 29.
    Hall FM, Goldberg RP, Davies JAK, Fainsinger MH. Scintigraphic assessment of bone islands. Radiology 1980; 135: 737.Google Scholar
  30. 30.
    Lagier R, Nussle D. Anatomy and radiology of a bone island. Fortschr Roentgenstr 1978; 128: 261.Google Scholar

Copyright information

© International Skeletal Society 1995

Authors and Affiliations

  • Adam Greenspan
    • 1
  1. 1.Department of RadiologyUniversity of California, Davis School of MedicineSacramentoUSA

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