2. IntroductionInitially described by Jaffe and Lichtenstein in
1942Common in first two decades of the life, the rarity of the
lesion in the adults suggests that spontaneous healing occurs.
3. PathogenesisHypothesized that the cyst forms as a response
to venous occlusion in the intramedullary spaceConsidered them to
be intraosseous synovial cystsDysplastic areas, which they believed
developed in response to trauma
4. PathologyAn area of fusiform expansionPeriosteum lifts away
easily and underlying bone is egg-shell thin,
semitranslucent,bluish and easily penetrated.
5. Histologic examinationThe cyst walls are lined with a
fibrous membrane, with occasional giant cells
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. 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. Vascular occlusion theoryThe pressures within a cyst are
elevated above venous pressuresif 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. simply lowering the interstitial pressure by multiple
perforations may cause cyst involution
10. Clinical FeaturesAge- younger patientsSex- M:F 2:1Most
common site-the proximal femur, followed by the proximal
humerusMany cysts are immediately adjacent to, and appear to
involve, the epiphyseal growth plate
11. The area is slightly warm and swollenThe symptoms of
unicameral bone cysts are most often brought on by traumaWhen
fractures do become evident, they rarely involve the growth plate
itself
12. Cysts progress from active to quiescent to an involutional
stage in the course of their natural historyThe difficulty for the
clinician is to assess the current stage of the cyst at the time of
diagnosis
13. RadiographsRadiographs usually reveal a nondisplaced or
minimally displaced fracture through an area of very thin, expanded
cortical bone
14. Fallen leaf signOccasionally, a fragment of the cyst wall
has fractured and fallen into the fluid cavity
15. The corticalfragment becomes dislodged from themargin at
the timeof fracture andliterally floats to thebottom of the cystic
structure.
16. MRIMagnetic resonance imaging most accurately delineates
the central fluid collection
17. D.D.Aneurysmal bone cystFibrous
dysplasiaEnchondromaEosinophilic granulomaGCT
18. TreatmentDifficult to decide whether the cyst is in the
active, latent, or involutional StageUnless 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. It may be reasonable to choose close observation rather
than a surgical procedureIf the cyst is active and obviously
enlarging during observation (3 to 6 months), treatment may be
appropriate
20. Exceptionlarge cyst involves the subtrochanteric region of
the femurEarly treatment may be needed to avoid fracture
21. Injection TechniquesInjecting methylprednisolone into the
cyst under fluoroscopic control while using radiopaque dye to
confirm entry into the cystAspiration of the cyst is done prior to
injectionThe level of PGE2 in cyst fluid is reduced after injection
of methylprednisolone
22. Advantageous by decreasing the morbidity due to a major
surgical procedureRecurrence rates of 15% to 88% after an average
of three injections
23. Surgical TechniquesResection or curettage plus bone
grafting has been employed as the definitive treatment for
unicameral bone cysts
24. TechniqueA cortical window is made, which allows access to
the entire contents of the cavityThe clear fluid should be removed,
and the fibrous membrane curetted from the cyst wall
25. Autologous bone marrow, allograft, demineralized bone
matrix (DBM), and other bone substitute materials have been used
successfullyThus sparing the patient the morbidity of an autograft
harvesting siteAllograft bone chips have proved effective in the
treatment of cysts
26. Calcium sulfate in the form of plaster of paris has been
used with a good success rate and a low recurrence rate
27. Demineralizedbone matrix,Bone marrow
28. ComplicationsRecurrence of the lesion after
treatmentDevelopment of a subsequent fracture
29. RecurrenceRecurrence 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
