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Table 1. Ficat stages of necrosis
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Stage                    Clinial Features   Radiographic Signs      Bone Scan              Abnormal      Diagnosis Without
                                                                                         Hemodynamics       Core Biopsy

Early
O, Preclinial            O                  O                       Decreased uptake?         +             Impossible

I, Preradiographic       O or +             O                       Increased uptake          ++            Impossible

II, Before flattening    +                  Diffuse porosis,        +                         ++             Probable
  of head or                                  sclerosis or cysts
  sequestrum

Transition                                  Flattening crescent
                                              signs

Late
III, Collapse            ++                 Broken contour of       +                    + or normal         Certain
                                              head
                                            Sequestrum
                                            Normal joint space

IV, Osteoarthritis       +++                Collapse of head        +                         +              Arthritis
                                            Decreased joint
                                              space
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(Reproduced with permission from Ficat RP: Idiopathic bone necrosis of the femoral head. J Bone
Joint Surg (1985;67B:3-9.)
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Beaty, JH (ed): Orthopaedic Knowledge Update 6. Rosemont, IL. American Academy of Orthopaedic Surgeons. 1999 Ch. 38, pp. 455-492.