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Methyl Prednisolone Injection Therapy For Unicameral Bone Cysts: A Comparative Study Between Upper And Lower Limb Cysts

 Sarrafan  Nasser *, Mehdinasab Seyed abdolhossein* ,Pipelzadeh Mohammad Reza**

* Assistant Professor of Orthopaedic Surgery
** Associated professor of Anesthesiology
Imam Khomeini Hospital . Jondishapur University of Medical Sciences. Ahwaz . Iran .

Address for Correspondence:  

Dr. Seyed Abdolhossein Mehdinasab
Imam Khomeini Hospital . Jondishapur University of Medical Sciences. Ahwaz . Iran .
E – mail:
Mobile phone : 0098 916 111 1052 
Fax: 0098 611 2216504
Tel:  0098 9161111052
Fax: 0098 611-2216504 


Background:Unicameral bone cysts (UBC) are treated by several methods including curettage and bone graft, multiple drilling, autogenous bone marrow or corticosteroid injection into the bone cyst.UBC in lower extremity due to weight bearing can be complicated by pathologic fracture.
The aim of this study was to assess and comparison the results of methyl prednisone injection in the UBC of the upper and lower limbs bone cyst. And compare outcome.
Material and methods: 30  patients (12 girls 18 boys) with age group of 4.5-19 years old (mean 11.9) were treated by methylprednisolone injection into the bone cyst and were followed for 26-48 months (Average 32 months). Patients where evaluated by serial radiographs (AP & lateral) at 2-3 months intervals.
Findings: UBC was located in humerus (n=18), in proximal of femur (n=9) and proximal of tibia (n=3). After methyl prednisolone injection into the lesion between 1-3 times, in 83 % of  humerus cases and 44% femoral and 100% tibia bone  cysts subsided and shrunk with increased bone density within 32 month.
Injection of methylprednisolon into UBC is a simple therapeutic method with a low rate of morbidity. The favorable results were seen mostly in the UBC of the humerus and tibia a compared to the femoral bone.

J.Orthopaedics 2008;5(1)e15


Unicameral bone cyst, methyl .prednisolone


The unicameral bone cyst is not a real neoplasm .It has been described first by Virchow (1) and Bloodgood differentiated it from other lytic bone lesions. (2) Jaffe and Lichtenstein gave more detailed information about UBC. (3) UBC involves 30% of all initial biopsies in bone tumors and is common in the first decades of age especially between 4-10 years. The prevalence in male is two folds that of female. (4)

This lesion is principally related to metaphysic of long bones. The common sites are humerus (50%), femur and distal and proximal tibia. (18-27%)  Rarely this bone lesion is also seen in calcaneus fibula, ulna, radius and talus and in older ages it can also develop within flat bones such as pelvic and vertebra. (5)

This simple cyst is categorized into active and non-active according to distance to growth plate. Active cysts are less than 0.5-1cm distance from growth plate and occur in younger ages.

The definite cause for cyst development is not known. Mirra related the cyst to trauma at the birth causing entrapment of synovial tissue into bone during neonatal period. (5)

Cohen et al believe that the cause is venous bone obstruction with accumulation of serum-like fluid in cyst. (6).This fluid result in cyst formation and may prevent union. Components such as prostaglandin interlokin 1, lysosomal enzymes of cyst fluid play a role in formation and nonamelioration of cyst. (7).

Other possible causes are trauma (8), rapid bone turnover (9), lymphatic blockage (10) or local growth disturbance with fibrotic tissue formation. Patients with UBC often complain of pain and limping. Pathologic fracture is the most common presentation in children.  

Radiographically bone cyst is seen as central lucency in medullary shaft of long bones. Fracture in the cyst is a pathognomonic sign (fallen fragment sign). (11) Unicameral bone cyst fractures easily which heals spontaneously in 5% of cases.

Abrupt treatment of fracture is necessary. More aggressive treatment is required in children under 10 years due to possibility of shortening by growth plate arrest and deformity (12).

Several methods of treatment have been suggested with age being the principal determining factor .Older patients have a better outcome. Other factors include size and location of cyst.

The final goal of treatment is bone formation in cyst to bear imposed stress and halting bone destruction documented by radiography. Esthetic look of bone is less important compared to formation of a stable and functional bone structure.

Several therapies have been used so far for unicameral bone cyst that include bone curettage with cryotherapy (13); multiple drilling of the wall cyst which has been associated with 12 % recurrence (14) autogenic bone marrow injection into cyst (15);cyst curettage and bone graft with or without internal fixation which has been associated with 50 % recurrence. (16) And local corticosteroid injection in bone cyst. (17)

Total or subtotal resection of cyst with or without bone grafting is an old method that is rarely used today. Recurrence has been reported in all above methods. Similar success has been seen with surgical approaches and corticosteroid injection which lead to popularity of the latter method. Steroid injection has been first described by Scaglietti et al in 1979 and claimed good results in 90% of cases (17) while curettage plus Bone graft has 45% recurrence rate. (18) surgery may cause growth disturbances while steroid injection  neutralize destructive factors in the cyst and result in  bone formation and along with low complication rate or scar development and its simplicity makes it a more common method of treatment.

Material and Methods :

30    patients (12 girls and 18 boys) with age group of 4.5-19 years old

(Mean 11.9) were treated with methyl prednisolone injection into cyst and were followed for 6-48 months (average 13.8 months).according to response. Patients where followed up by serial radiographs (AP & lateral) at 2-3 months intervals.

The time delay between previous pathologic fracture and first injection was 1.5- 3 months (average 2.5 months).

8 patients had proximal femur cyst presented with limping and pain. One patient with cyst in tibia presented with pain. Pathologic fracture was the presentation in one femur cyst.  The cysts of the femur less than one half of diameter included in the study. All patients with cyst in the proximal humerus presented with pathologic fracture.

Patients were managed by primary casting. Patients were admitted after union of fracture site under general anesthesia with balanced technique patients were prepped and draped. Using 2 biopsy or size 16 needles under C-Arm control we entered the cyst. If the cortex of cyst was thick we drilled the cortex. The content of cyst was aspirated under pressure which resulted in cutting and separating of internal capsule of bone cyst. Then we measured the volume of fluid after aspiration. We then washed cyst hole by normal saline and injected 40 mg methyl prednisolone acetate for every milliliter aspired fluid into cyst with maximum of 200 mg methyl prednisolone. Finally compression bandage and sling was applied.

For children under 6 years old we used a long leg plaster cast plus pelvic band and for older children we recommended axillary crutch.

Control radiographs were taken at 2-3 months interval. The signs of amelioration included reduction of cyst size, increase thickness of cortex   increasing density within cyst by calcification or new bone trabecular formations. 


In 18 patients with humerus cysts. A 10 year old girl developed pathologic fracture after 2 injections at 6 months follow up. Three patients had no response to treatment. 15 of patients had favorable outcome during 6-18 months follow up.

9 patients (75%) had cyst in femur bone. All three patients had favorable results. Only one patient developed coxa vara with 110 degree angulation. Three patient with upper third of tibia cyst responded well to treatment. (25%) Three patients were well treated in the first 4-6 months post injection. 5 patients of femoral bone cyst had no response to treatment.   


Table 1:  Data summary and response to treatment



18 (60%)


12 (40%)



Age (years)

4.5-19 ( mean 11.7)




Chief complaint on presentation

Pathologic fracture

16 (53%)


5 (16%)


8 (66%)



Proximal humerus

15 (83%)

Mid humerus 3(17%)

Upper third tibia

3 (25%)



9 (75%)

No. of injections


N= 4 (13.3%)


N= 18 (60%)


N= 8(26.6%)


Response to injection


   humerus15 (83%)

           Femur   4 (44%)

     Tibia   3 (100)


  Humerus 3 (19%)

   Femur 5 (56%)





New Pathologic fracture

1 (3%)

Coxa vara

1 (3%)



Discussion :

Our results showed satisfactory response in most of the patients sustained humeral bone cysts, with favorable response to steroid injection in hummers about tow folds of the femoral lesions. We also showed a satisfactory healing rate in all of the tibial cases. Satisfactory results obtained where at least two injections was performed.

Steroid have anti-prostaglandin effect and can neutralise biochemical components in the cyst such as interlokin 1 and proteolytic enzymes which play an important role in cyst recurrence.(19) scaglietti et al reported  success rate are  varied between  90-95% cases. (17) The success rate by Oppenhein was reported in 40% by,Galleon. H in 75% (20) and by Companocci in 50% of the cases. (21) In our Group we had success rate of 44% for femur cyst.wthich is similar to Hashemi Negad W.G.Cole.  (22)

Our results are comparable to others with success rate of 83%.for humeral cyst that confirms the effectiveness of steroid injection in humeus UBC cyst and has a low morbidity. Steroid injection may need several injections and requires long time follow up. 


Treatment of UBC by injection of methylprednisolon acetate in the lesion is a simple and effective method with a low rate of complication; we recommend this method for treatment of UBC of humerus, tibial and only for small cysts of femur .because of less favorable results in the UBC of the femur, and other therapeutic options must be considered.

During clinical consultation parents should be informed about success rate possibility of changing treatment plan and that patient may need several injections.


Reference :

  1. Baker DM, Bonign.unicameral one cyst a. study of forty-five cases with long-term follow-up Clinical-Orthop: 1970:71,140-51.
  2. Bloodgood.JC: Benign bone cyst,osteitis fibrosa gaintcell sarcoma and bone aneurysm of long pipe bone.1910; 52:145-82.
  3. Jaffe H: Tumors and Tumorous Conditions of the Bones and joints.Philadephia: Lea & Febiger, 1958.
  4. Abdelwahab IF,Hermann G, Norton KI,Kenan S,Lewis MM,Klein MJ:”Simple” bone cysts of the pelvis in adolesents: a report of four cases, J Bone Joint Surg 73A:1090-1094,1991
  5. Mirra JM,Bone Tumors: Diagnosis and Treatment.Philadelphia:JB Lippincott, 1980
  6. Cohen J:Unicameral bone cysts: a current synthesis of reported cases.Orhop Clin North Am 1977;8:715.
  7. Komiya S,Minamitani K, Sasaguri Y,et al : Simple bone cyst: treatment by trepanation and studiets on bone resorptive factors in cyst fluid with a theory of its pathogenesis .Clin Orthop 1993;287:204.
  8. Jaffe HL.Lichtenshein L: Solitary U.B.C with emphasis on the roent.pathologic appearance and the pathogenesis.Arch sug :1942;44.104-25.
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  10. Oppenheim W.L., Galleno H.Operative treatment versus steroid injection in unicameral bone cysts. J Pediatr Orthop.1984;4,1.1-7
  11. Telfer MR,Jones GM,Pell GM,Eveson JW:Primary bone cyst of the mandibular condyle, Br J Oral Maxillofac Surg 28:340-343,1990.
  12. Ahn JI,Pathological fractures secondary to unicameral bone cysts.Int Orthop 1994;18:20.
  13. Schreuder HW,Conrad EU,3rd.Brukner JD,Howlett AT,Sorensen LS.Treatment of simple bone cysts in children with curettage and cryosurgery.Jor Pediatric Orthopedics 1997;17(6):814-20.
  14. Shinozaki T,Arita S,Watanabe H,et al:Simple bone cyst trated by multiple drill-holes;23 cyst followed 2-10 years(See comments).Acta Orthop Scan 1996;67:288.
  15. Lokiec F,Ezra E,Khermosh O,Wientroub S.Simple bone cysts treated percutaneous autologous marrow grafting.A preliminary report [see comment]Journal of Bone & Joint Surgery-British Volume 1996;78(6):934-7.
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  17. Scaglitti O,Marchetti PG,Bartolozzi P:The effects of methylprednisolone acetata in the treatment of bone cysts: results of three years follow-up Bone Joint Surg 1979;61-B:200.
  18. Scaglietti O,Marchetti PG,Bartolozzi P, et al: Final result obtained in the treatment of bone cysts with methylprednisone acetate (Depo-Medrol) and a discussion of results achieved in other bone lesions: Clin Orthop 165:33-42,1982.
  19. Abdel waheb IF:Herman G.Northon KI,Kenans Lewis MM Klein MJ.Simple bone cysts of the plevis in adolescents: a report of four cases: JBJS 73A:1090-1094.1991
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  21. Campanacci M,Capanna,R,and Picci,P:Unicameral and aneurysmal bone cyst clinical Orthopedic and related research 1986.204.25-36
  22. A. Hashemi.Nejad, W.G.Cole British editorial Society of Bone and Joint Surgery 1997;0301-620X/97/57825

This is a peer reviewed paper 

Please cite as : Mehdinasab Seyed abdolhossein : Methyl Prednisolone Injection Therapy For Unicameral Bone Cysts: A Comparative Study Between Upper And Lower Limb Cysts

J.Orthopaedics 2008;5(1)e15





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