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 thelesion in the adults suggests that spontaneous healing occurs.
  3. 3. PathogenesisHypothesized that the cyst forms as a response to venousocclusion in the intramedullary spaceConsidered them to be intraosseous synovial cystsDysplastic areas, which they believed developed in responseto trauma
  4. 4. PathologyAn area of fusiform expansionPeriosteum lifts away easily and underlying bone is egg-shellthin, semitranslucent,bluish and easily penetrated.
  5. 5. Histologic examinationThe cyst walls arelined with a fibrousmembrane, withoccasional giantcells
  6. 6. The fluid within the cyst has beenanalyzed and shown to contain highlevels of oxygen-free-radicalscavengers, prostaglandins(prostaglandin E2), interleukin-1, andproteolytic enzymes
  7. 7. These substances, which cause bone resorption, may play a rolein the formation and growth of cysts.The cyst fluid has a lower total protein content than serum buthigher levels of protein-bound hydroxyproline, lactate, andalkaline phosphatase.
  8. 8. Vascular occlusion theoryThe pressures within a cyst are elevated above venouspressuresif radiopaque dye is injected into the cyst with enoughpressure, the dye can be extruded into the venous system ofthe limb. Reestablishing these outflow channels may assist inthe involution of the cyst
  9. 9. simply lowering the interstitial pressure by multipleperforations 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 proximalhumerus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 oftenbrought on by traumaWhen fractures do become evident, they rarely involve thegrowth plate itself
  12. 12. Cysts progress from active to quiescent to an involutionalstage in the course of their natural historyThe difficulty for the clinician is to assess the current stage ofthe cyst at the time of diagnosis
  13. 13. RadiographsRadiographs usually reveal a nondisplaced or minimallydisplaced fracture through an area of very thin, expandedcortical bone
  14. 14. Fallen leaf signOccasionally, a fragment of the cyst wall has fractured andfallen into the fluid cavity
  15. 15. The corticalfragment becomesdislodged from themargin at the timeof fracture andliterally floats to thebottom of the cystic structure.
  16. 16. MRIMagnetic resonance imaging most accurately delineates thecentral 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, orinvolutional StageUnless there is a tremendous amount of cortical thinning,there may not be a comparable decrease in strength as a cystexpands the cortical margins
  19. 19. It may be reasonable to choose close observation rather thana surgical procedureIf the cyst is active and obviously enlarging duringobservation (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 fluoroscopiccontrol 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 ofmethylprednisolone
  22. 22. Advantageous by decreasing the morbidity due to a majorsurgical procedureRecurrence rates of 15% to 88% after an average of threeinjections
  23. 23. Surgical TechniquesResection or curettage plus bone grafting has been employedas the definitive treatment for unicameral bone cysts
  24. 24. TechniqueA cortical window is made, which allows access to the entirecontents of the cavityThe clear fluid should be removed, and the fibrous membranecuretted from the cyst wall
  25. 25. Autologous bone marrow, allograft, demineralized bone matrix(DBM), and other bone substitute materials have been usedsuccessfullyThus sparing the patient the morbidity of an autograft harvestingsiteAllograft bone chips have proved effective in the treatment ofcysts
  26. 26. Calcium sulfate in the form of plaster of paris has been usedwith 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 10years,When the lesion is in the upper humerus and closely adjacentto the growth plate

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