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Unicameral bone cysts

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Unicameral Bone Cysts are fluid-filled bone lesions most common in children under 20. They form due to venous occlusion in the bone marrow and contain substances that cause bone resorption. Clinically, they present as swelling and pain after trauma in the femur or humerus. Radiographs show expanded thin bone with fractures. Treatment involves injections or surgery to curette the cyst membrane and fill the cavity to prevent fractures and recurrence.

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Unicameral Bone Cysts

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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

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

Pathology An area of fusiform expansion Periosteum lifts away easily and underlying bone is egg-shell thin, semitranslucent,bluish and easily penetrated.

5

Histologic examination The 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 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

simply lowering the interstitial pressure by multiple perforations may cause cyst involution

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

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

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

Radiographs Radiographs usually reveal a nondisplaced or minimally displaced fracture through an area of very thin, expanded cortical bone

14

Fallen leaf sign Occasionally, a fragment of the cyst wall has fractured and fallen into the fluid cavity

15

The cortical fragment becomes dislodged from the margin at the time of fracture and literally floats to the bottom of the cystic structure.

16

MRI Magnetic resonance imaging most accurately delineates the central fluid collection

17

D.D. Aneurysmal bone cyst Fibrous dysplasia Enchondroma Eosinophilic granuloma GCT

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

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

Exception large cyst involves the subtrochanteric region of the femur Early treatment may be needed to avoid fracture

21

Unicameral bone cysts

22

Unicameral bone cysts

23

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

24

Advantageous by decreasing the morbidity due to a major surgical procedure Recurrence rates of 15% to 88% after an average of three injections

25

Surgical Techniques Resection or curettage plus bone grafting has been employed as the definitive treatment for unicameral bone cysts

26

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

27

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

28

Calcium sulfate in the form of plaster of paris has been used with a good success rate and a low recurrence rate

29

Demineralized bone matrix,Bone marrow

30

Complications Recurrence of the lesion after treatment Development of a subsequent fracture

31

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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Unicameral bone cysts

  • 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. 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. Pathology An area of fusiform expansion Periosteum lifts away easily and underlying bone is egg-shell thin, semitranslucent,bluish and easily penetrated.
  • 5. Histologic examination The 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 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. simply lowering the interstitial pressure by multiple perforations may cause cyst involution
  • 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. 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. 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. Radiographs Radiographs usually reveal a nondisplaced or minimally displaced fracture through an area of very thin, expanded cortical bone
  • 14. Fallen leaf sign Occasionally, a fragment of the cyst wall has fractured and fallen into the fluid cavity
  • 15. The cortical fragment becomes dislodged from the margin at the time of fracture and literally floats to the bottom of the cystic structure.
  • 16. MRI Magnetic resonance imaging most accurately delineates the central fluid collection
  • 17. D.D. Aneurysmal bone cyst Fibrous dysplasia Enchondroma Eosinophilic granuloma GCT
  • 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. 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. Exception large cyst involves the subtrochanteric region of the femur Early treatment may be needed to avoid fracture
  • 23. 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
  • 24. Advantageous by decreasing the morbidity due to a major surgical procedure Recurrence rates of 15% to 88% after an average of three injections
  • 25. Surgical Techniques Resection or curettage plus bone grafting has been employed as the definitive treatment for unicameral bone cysts
  • 26. 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
  • 27. 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
  • 28. Calcium sulfate in the form of plaster of paris has been used with a good success rate and a low recurrence rate
  • 30. Complications Recurrence of the lesion after treatment Development of a subsequent fracture
  • 31. 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