Unicameral bone cysts

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Unicameral bone cysts

  1. 1. Unicameral Bone Cysts
  2. 2. IntroductionInitially described by Jaffe and Lichtenstein in 1942Common in first two decades of the life, the rarity of the lesion in the adults suggests that spontaneous healing occurs.
  3. 3. PathogenesisHypothesized that the cyst forms as a response to venous occlusion in the intramedullary spaceConsidered them to be intraosseous synovial cystsDysplastic areas, which they believed developed in response to trauma
  4. 4. PathologyAn area of fusiform expansionPeriosteum lifts away easily and underlying bone is egg-shell thin, semitranslucent,bluish and easily penetrated.
  5. 5. Histologic examinationThe cyst walls are lined with a fibrous membrane, with occasional giant cells
  6. 6. The fluid within the cyst has been analyzed and shown to contain high levels of oxygen-free-radical scavengers, prostaglandins (prostaglandin E2), interleukin-1, and proteolytic enzymes
  7. 7. These substances, which cause bone resorption, may play a role in the formation and growth of cysts.The cyst fluid has a lower total protein content than serum but higher levels of protein-bound hydroxyproline, lactate, and alkaline phosphatase.
  8. 8. Vascular occlusion theoryThe pressures within a cyst are elevated above venous pressuresif radiopaque dye is injected into the cyst with enough pressure, the dye can be extruded into the venous system of the limb. Reestablishing these outflow channels may assist in the involution of the cyst
  9. 9. simply lowering the interstitial pressure by multiple perforations may cause cyst involution
  10. 10. Clinical FeaturesAge- younger patientsSex- M:F 2:1Most common site-the proximal femur, followed by the proximal humerusMany cysts are immediately adjacent to, and appear to involve, the epiphyseal growth plate
  11. 11. The area is slightly warm and swollenThe symptoms of unicameral bone cysts are most often brought on by traumaWhen fractures do become evident, they rarely involve the growth plate itself
  12. 12. Cysts progress from active to quiescent to an involutional stage in the course of their natural historyThe difficulty for the clinician is to assess the current stage of the cyst at the time of diagnosis
  13. 13. RadiographsRadiographs usually reveal a nondisplaced or minimally displaced fracture through an area of very thin, expanded cortical bone
  14. 14. Fallen leaf signOccasionally, a fragment of the cyst wall has fractured and fallen into the fluid cavity
  15. 15. The corticalfragment becomes dislodged from themargin at the timeof fracture andliterally floats to thebottom of the cystic structure.
  16. 16. MRIMagnetic resonance imaging most accurately delineates the central fluid collection
  17. 17. D.D.Aneurysmal bone cystFibrous dysplasiaEnchondromaEosinophilic granulomaGCT
  18. 18. TreatmentDifficult to decide whether the cyst is in the active, latent, or involutional StageUnless there is a tremendous amount of cortical thinning, there may not be a comparable decrease in strength as a cyst expands the cortical margins
  19. 19. It may be reasonable to choose close observation rather than a surgical procedureIf the cyst is active and obviously enlarging during observation (3 to 6 months), treatment may be appropriate
  20. 20. Exceptionlarge cyst involves the subtrochanteric region of the femurEarly treatment may be needed to avoid fracture
  21. 21. Injection TechniquesInjecting methylprednisolone into the cyst under fluoroscopic control while using radiopaque dye to confirm entry into the cystAspiration of the cyst is done prior to injectionThe level of PGE2 in cyst fluid is reduced after injection of methylprednisolone
  22. 22. Advantageous by decreasing the morbidity due to a major surgical procedureRecurrence rates of 15% to 88% after an average of three injections
  23. 23. Surgical TechniquesResection or curettage plus bone grafting has been employed as the definitive treatment for unicameral bone cysts
  24. 24. TechniqueA cortical window is made, which allows access to the entire contents of the cavityThe clear fluid should be removed, and the fibrous membrane curetted from the cyst wall
  25. 25. Autologous bone marrow, allograft, demineralized bone matrix (DBM), and other bone substitute materials have been used successfullyThus sparing the patient the morbidity of an autograft harvesting siteAllograft bone chips have proved effective in the treatment of cysts
  26. 26. Calcium sulfate in the form of plaster of paris has been used with a good success rate and a low recurrence rate
  27. 27. Demineralizedbone matrix,Bone marrow
  28. 28. ComplicationsRecurrence of the lesion after treatmentDevelopment of a subsequent fracture
  29. 29. RecurrenceRecurrence is more when the patient is younger than 10 years,When the lesion is in the upper humerus and closely adjacent to the growth plate

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