202 KUWAIT MEDICAL JOURNAL September 2008

Original Article Management of Unicameral Bone Cyst of Proximal Femur: Experience of 14 Cases and Review of Literature

Magdy M Abdel-Mota’al, Abdul Salam Othman Mohamad, Kenneth Chukwuka Katchy, Amarnath A Mallur, Fawzy Hamido Ahmad, Barakat El-Alfy

Kuwait Medical Journal 2008, 40 (3): 202-210 ABSTRACT Objective: To assess the results of surgical treatment Main Outcome Measures: Patients were followed up of unicameral bone cyst (UBC) involving the proximal post-operatively for an average period of 42 months (range femur = 9–120 months). They were observed for recurrence, Design: Retrospective study of 14 cases of UBC of complications and fracture healing. proximal femur Results: Recurrence was observed in one case while other Setting: Al-Razi Orthopedic Hospital, Kuwait cases showed healing of the cyst with consolidation and Subjects and Methods: Fourteen cases of UBC seen and varying degrees of remodeling in one years time. A case treated at Al-Razi hospital were included in the study. developed mal-union and growth arrest with subsequent Their presentation and the method of treatment were shortening. Avascular necrosis and coxa vara was recorded. detected in another case. All the fractures healed in the Intervention: Thirteen cases were treated surgically using usual expected time according to age. intra-lesional excision (ILE). The cavity was filled with Conclusion: UBC of the proximal femur exhibits unique autogenous bone graft in three cases, hydroxyapatite characters and complications. Hydroxyapatite matrix matrix (HA) in eight cases, and combined autogenous is a useful and effective bone substitute. Post-excision graft and hydroxyapatite matrix in two cases. Internal stabilization of the cyst is recommended to avoid mal- fixation was carried out in six cases. External fixator was union and to facilitate post-operative rehabilitation and applied in one case from iliac bone to femur crossing the earlier return to normal activities. hip joint.

KEYWORDS: pathologic fracture, proximal femur, UBC

INTRODUCTION necrosis (AVN) of proximal femoral epiphysis and Unicameral bone cyst (UBC) is defined as collapse of the articular surface was reported as a an atrophic degenerative osteolytic process complication of UBC involving proximal femur[9-11]. consisting of a cavity filled with fluid and lined Among the wide range of different modalities [1] by a membrane . The membrane is composed of described for treatment of UBC are: radical excision cells staining positively with CD68,SDF-1,STRO- in form of subperiosteal partial diaphysectomy 1,RANKL and express RUNX2.UBC cells show and allograft[12], subtotal resection with[13] and 24.2% of apoptosis significantly higher than 17.2% without bone graft[14], curettage and bone graft[6], [2] of trabecular bone cells . Biochemical analysis multiple drill holes[15,16], intra-cystic prednisolone of the cyst fluid showed bone-resorptive factors, injection[5,7,9] and recently, intra-medullary flexible i.e., prostaglandins, interleukin 1 and proteolytic nails[17,18]. Some authors focused their interest on enzymes[3]. UBC and other benign lesions located at proximal UBC has highest incidence between 5 and 15 femur as this area exhibits unique characters and years[1] and 50% of upper femoral lesion are over complications[8,19-23]. The aim of this study is to 17 and their age as high as 54 years[4]. It usually describe our experience with the results of surgical arises in the metaphysis of long bones immediately treatment of UBC involving proximal femur in beneath the growth plate and the most common location is proximal humerus followed by proximal Kuwait. femur[1,4-7] which accounts for 27% of cases[5]. UBC was the underlying lesion in 40% of pathological SUBJECTS AND METHODS femoral neck fractures in children[8]. Avascular The current study represents a retrospective

Address correspondence to: Magdy M. Abdel-Mota’al, MD (Egypt), Senior registrar, Department of Orthopaedic Surgery, Al-Razi Hospital, Kuwait. P.O.Box # 43402, Postal Code 32049, Hawalli, Kuwait. Tel : +965-5324185, E-mail: [email protected] September 2008 KUWAIT MEDICAL JOURNAL 203

Table 1: Summary of the cases, presentation, treatment and their results

Age at Follow Case presen- Sex Side presentation Work up Location of the lesion Location of the fracture Displacement Treatment complications up No. tation months

Pathological. ILE + local adjuvant + HA + 1 14 F Lt C.T Inter –subtrochanteric Basotrochanteric Displaced 47 fracture DHS + Screw + Spica Nil

Pathological. ILE + local adjuvant + HA + 2 14 M Lt Intertrochanteric Inter-trochanteric Undisplaced Nil 24 fracture DHS

Pathological. 3 8 M Lt Neck Transcervical Undisplaced ILE + HA +KW’S + spica Nil 36 fracture

Pain, limp, wasting CT+ 4 24 M Rt Head & neck - - ILE+ Auto grafts + Ext fixator Nil 24 of quadriceps Bone scan

Pain, limp, wasting CT+ ILE + local adjuvant + HA + 5 24 M Rt Intertrochanteric - - Nil 30 of quadriceps Bone scan Auto graft + DHS + Screw

6 30 F Lt Pain C.T Inter –subtrochanteric - - Auto graft + DHS Nil 120

7 18 M Lt Pain C.T Head & neck - - ILE+ Auto grafts + Spica Nil 60

8 5 M Lt Pain - Inter Trochanteric - - ILE + HA +Auto grafts+ spica Recurrence 9

Pathological. 9 7 M Rt - Inter –subtrochanteric Inter-trochanteric Undisplaced ILE + HA + spica Nil 36 fracture

Pathological. 10 8 F Rt - Inter –subtrochanteric Inter-trochanteric Undisplaced ILE + HA + spica Nil 24 fracture

Pathological. Neck + Inter –sub Shortening+ mal 11 7 F Rt - Inter-trochanteric Undisplaced ILE + local adjuvant + HA +Spica 30 fracture trochanteric union +growth arrest

Pain & limitation of 12 10 M Rt - Inter –subtrochanteric - - ILE + local adjuvant + HA +Spica Nil 33 hip movements

Pathological. ILE + local adjuvant + HA + 13 10 M Rt C.T Inter –subtrochanteric Inter-trochanteric Undisplaced Nil 30 fracture DHS

Pathological. Neck + inter –sub AVN, Coxa 14 7 M Rt - Neck Displaced Conservative 85 fracture trochanteric vara,shortening

Rt = Right, Lt = Left, ILE = Intra-lesional excision, HA = Hydroxyapatite, DHS = Dynamic hip screw, AVN = avascular necrosis, KW = Kirschner wire 204 Management of Unicameral Bone Cyst of Proximal Femur: Experience of .... September 2008 analysis of 14 cases of UBC involving proximal three years time in three cases (case # 1, 6 and 13). femur treated at Al-Razi Orthopedic Hospital, Case # 11 developed mal-union and growth arrest Kuwait during the period from 1990 through of greater tuberosity growth plate with subsequent 2003 (Table 1). Analysis was a thorough review of shortening. This required raising the heel and did medical records, including medical history, clinical not need any surgical procedure at the last clinical examination, work-up, operative details and follow- assessment. AVN and coxa vara were detected in up at the clinic. another case (case # 14). She was 14 years old at last Age at presentation ranged from 5 - 30 years follow-up. Clinical evaluation showed fair range of with an average of 13 years. Ten cases were male movement with occasional hip pain. Radiographic and four were female. All cases were symptomatic. examination reported incongruent congruity of the Pathological fractures were the presenting symptoms involved hip joint. She needs long follow-up to detect in five cases. The other cases presented with pain, the onset of disabling degenerative changes which various degrees of limp, limited hip movement and dictate reconstructive procedures. All the fractures quadriceps wasting. The right side was involved healed in the usual expected time according to age. in eight cases. Radiographic examination was the basic imaging technique for all the cases, whereas DISCUSSION CT was done for selected cases (case # 1, 4, 5, 6, 7 The basic surgical technique employed in the and 13) to assess bony destruction and bone scan current study was ILE in the form of curettage for cases with doubtful diagnosis (case # 4 and 5). and cleaning of the wall by power burr. In order In most cases the lesion was located in the inter- to improve the margin and to decrease recurrence trochanteric area with varying degrees of extension rate, local adjuvant therapy was applied earlier toward the neck and subtrochanteric region. The through this study in six cases (case # 1, 2, 5, 11, head and neck were involved in two cases (case # 12, and 13). 40% phenol was applied with a cotton 4 and 7). The neck was affected in one case (case tipped applicator and was removed by lavage with # 3). In one case (case # 14) diagnosis was based alcohol[25]. No recurrence was reported in those [21,24] on typical X-ray appearance and clinical course . cases. Phenol was first applied to UBC by Neer In the other cases histopathological study of the et al in 1966[6]. However, because of lack of recent curetted material confirmed the diagnosis. eviddence supporting the use of phenol in UBC, we Surgical treatment was employed in all cases did not use it in later cases. with exception of one case (case # 14) which was We used autogenic bone graft alone to fill referred from another hospital. The basic surgical resultant cavity in three cases (case # 4, 6, 7). Neer technique in all cases was intra-lesional excision et al reported surgical treatment of 129 cases of UBC (ILE). Local adjuvant therapy was used in six cases by curettage (ILE) and bone graft. They evaluated (case # 1, 2, 5, 11, 12 and 13) which consisted of 24 out of 31 cases located in the proximal femur and painting with phenol 40%, cleaning with alcohol reported recurrence in four cases (17%). The results 90% and irrigation with normal saline. The cavity of allograft were compared to autograft used to was filled with autogenous bone graft in three cases fill the defect after curettage of 93 cysts located in (case # 4, 6, and 7), hydroxyapatite matrix (HA) in proximal femur and humerus. In 35 cases treated eight cases (case # 1, 2, 3, 9, 10, 11, 12, and 13) and with autograft, 21 cases (60%) were excellent, six combined autogenous graft and hydroxyapatite cases (17%) showed residual defect and eight cases matrix in two cases (case # 5 and 8). Internal fixation (23%) required re-operation. In 58 cases treated with was carried in the form of dynamic hip screw (DHS) allograft; 28 cases (48%) were excellent, 12 cases in five cases (case # 1, 2, 5, 6 and 13) and KWs in (48%) showed residual defect, and 18 (31%) cases one case (case # 3) which was removed in six weeks required re-operation. Thus autograft was slightly time. External fixator from the iliac bone to femur better[6] and therefore indicated in recurrence, when crossing the hip joint was applied in one case (case there is a sufficient quantity of bone which can be # 4). conveniently taken to fill the defect[4,6]. Allograft is indicated for the pediatric age group with large RESULTS cyst[4]. Campanacci et al did not find any relation Follow-up ranged from 9 -120 months with an between type of bone graft and rate of recurrence average of 42 months. With exception of one case and pointed out the importance of packing of the which showed recurrence 9 months after surgery cyst well as residual empty spaces might be a source (case # 8), the minimum follow-up was 24 months. for recurrence[5]. All other cases showed healing of the cyst with HA was reported to have been used to fill the consolidation and varying degrees of remodeling cavity of benign bone tumor and lesions after in one years time. The hardware was removed in surgical excision. Out of 22 cases of UBC treated September 2008 KUWAIT MEDICAL JOURNAL 205

Fig. 1a: Case # 13 showing preoperative status Fig. 1b: After curettage and filling the cavity Fig. 1c: Hardware removed two years after with hydroxyapatite matrix surgery shows complete healing of the cyst by curettage followed by packing of the cavity with four months after the onset of treatment which high-porosity HA, complete healing without cyst required open reduction and internal fixation. A recurrence occurred in 18 (78%) cases. New bone limb-length discrepancy was observed in two cases surrounding HA was radiologically detected within without prior surgery or pathological fracture. One an average of 2.3 months[26]. In the current study of them was at the proximal femur[9]. HA matrix was used alone to fill the curetted cavity Campanacci et al compared 178 cases of UBC in eight cases and combined with autogenic bone in treated by curettage and bone graft to 141 cases two cases. All ten cases healed and showed varying treated by methylprednisolone injection. The degrees of remodeling without recurrence (Fig. 1a, recurrence rate was 33 and 15% respectively. b, and c). Pathological fracture developed in two cases during Recurrence was reported in one case (7%) in the injection treatment and in another 11 cases after current study (case # 8). A 5-year-old boy presented recurrence of the cyst. AVN of the femoral head was with UBC involving the inter-trochanteric region observed in one case treated by injection therapy[5]. of left femur. He was treated by ILE and packing It was found that healing response to intra-lesional of the cyst cavity with a mixture of HA matrix and corticosteroid injection is unpredictable and usually autogenous bone graft. Early signs of recurrence incomplete even after multiple injections. The were detected by the ninth month. It was reported failure rate in the weight-bearing bone is high[27]. that recurrence following surgical treatment was Percutaneous injection of autogenous bone more frequent in patients under the age of 10 years, marrow was described for treatment of UBC. The and age was a more reliable prognostic factor than results of single injection of bone marrow into UBC the proximity of the cyst to growth plate[4,6]. were reported in eight cases, four out of them in In 1974, Scaglietti et al described minimally the proximal femur. Healing according to Capanna invasive empiric injection of UBC with criteria[9] was complete in one case, incomplete methylprednisolone. He reported 72 cases out of in six cases, no response in one case and there which 11 were located in the proximal femur with was no recurrence[28]. In a series of 79 consecutive a healing rate of 96%[7]. Capana et al reviewed 90 patients with UBC, the results of aspiration and cases of UBC treated by intra-cystic injection of bone marrow injection were compared with those methylprednisolone out of which 20 were located of aspiration and injection of steroids. The author at proximal femur. He reported 80% satisfactory reported that no advantage could be shown for the results and there was a need for two to six injections use of marrow injection over steroid injection in per patient in order to achieve healing. Recurrence treatment of UBC[29]. after cyst consolidation was observed in 12 patients Autogenous bone marrow injection was (13%). Pathological fracture developed in seven combined with allogenic demineralized bone patients during the course of treatment. One of matrix for treatment of UBC in 23 patients five of them was a displaced fracture at proximal femur them were in proximal femur. The average time for 206 Management of Unicameral Bone Cyst of Proximal Femur: Experience of .... September 2008

Fig. 2a: Case # 14 shows pathological fracture Fig. 2b: Healing with coxa vara and AVN (AP Fig. 2c: Healing with coxa vara and AVN treated conservatively view) (lateral view) pain relief was five weeks, and the average time In the current series there was a seven year old until patients returned to full unrestricted activity girl (case # 14) who presented with pathological was six weeks. A second injection was required neck fracture through UBC involving the femoral because of recurrence in five patients (22%) neck and inter-trochanteric area. She was treated whereas pathological fracture occurred in one conservatively in form of skin traction followed case[30]. Similar results were reported after injection by hip spica. The fracture healed and the cyst of demineralized bone graft without bone marrow, consolidated, but she developed coax vara and suggesting that the use of bone marrow may not be AVN of the femoral head (Fig. 2a, b, c). In a necessary to achieve good results[31]. series of 20 children with pathological fracture of Based on venous obstruction as a theory for proximal femur treated conservatively, the fracture development of UBC, Chigira et al introduced the was displaced in eight cases. All of the displaced treatment by multiple drill holes. He reported on fractures healed but with coxa vara and AVN in seven cases of UBC. Two were located in the femur. one child, coxa vara in a second and coxa breva in Healing was observed within six to eight months. a third child. All of 12 undisplaced fractures healed One of the cysts located in the femur required without deformity or avascular necrosis, but they curettage and bone graft because of poor healing[15]. required from 1 - 7 injections of prednisolone for The same technique was applied to 23 cases of UBC. healing of the cyst. Re-fracture was observed in six Nine cysts were located in the femur. Recurrence children 2 - 5 years after presentation[21]. was observed in 15 cases[16]. After pathological fracture through UBC the Roposch et al evaluated the results of flexible early radiological appearance suggests progressive intra-medullary nail in the treatment of UBC in 32 healing of the cyst, but complete healing of the cyst cases. The cyst was located in the proximal femur seldom takes place without operative treatment[32]. in nine patients. Recurrence was observed after Hence the proximal femoral cyst needs to be surgically removal of the nail in two cases, one of which was treated to avoid mal-union and persistence of the located in proximal femur. Change of the nail was cyst[19,33]. Wai et al reported 11 cases of pathological required in nine cases, three located in the femur. A fractures of proximal femur secondary to benign varus deformity of proximal femur developed in five lesion. All cases were treated with curettage, high cases after consolidation of the cyst[17]. In series of 12 speed burring and reconstruction using a mixture of cases of UBC of proximal femur treated by flexible allo - and autogenic graft, and a fixed angle implant. intra-medullary nail, complications were reported All factures healed without local recurrence[23]. in three cases. Perforation of the nail through the Both location of the cyst and the amount of bone lateral cortex led to coxa vara in one case. The nail loss dictate whether fixationcan stabilize the fracture was removed and the femoral neck was fixed with and type of fixationbest suited for this purpse. Based a plate. The nail was changed as it became too short on remaining bone in the femoral neck beneath the for the growing child in two cases[18]. growth plate, bone in the lateral proximal femur September 2008 KUWAIT MEDICAL JOURNAL 207

Fig. 3a: Case # 1 shows displaced pathological Fig. 3b: Fixation with DHS and anti rotation Fig. 3c: The hardware removed two years after fracture screw surgery sub-type III-B (case # 2 and 13). Case # 3 presented with undisplaced pathological fracture neck and was classified as II-A[17]. The fracture was fixed after surgical treatment with multiple KWs supplemented with hip spica (Fig. 4a, b). Case # 11 was a seven year old girl who presented with pathological fracture through UBC involving the neck, sub- and inter-trochanteric areas. After surgical treatment it was difficult to stabilize the fracture because there was not enough bone between the cyst and capital epiphysis and deficient lateral buttress (Fig. 5a, b, c). This case was classified as II-B[19]. The cyst consolidated and the fracture healed but with mal-union, shortening and Fig. 4a Fig. 4b growth arrest of the greater trochanter.

Fig. 4a: Case # 3. Insufficient bone between cyst and the growth plate but Few studies were published to assess the good lateral buttress to hold K wires and 4b: When the cyst was stabilized fracture risk in cases of UBC. Kaelin et al devised a with K wires following currettage cyst index to assess the risk for fracture and found that in femoral fracture the average index was 4.4 (lateral buttress) and skeletal maturity, Dormans et (SD = 0.75), the lowest index was 3.6 and there al classified pathological fracture of femoral neck was no fracture in cysts with index lower than in children into three types with six subtypes and [24] [19] 3.5 . Shih et al defined the criteria for impending described the best fixation for each type . fracture secondary to UBC of proximal femur as 2.5 Case # 1 presented with displaced pathologic cm or larger lytic area in the upper femur, a lesion baso-trochanteric fracture. It was type 111-B involving half of the femoral neck or more and according to classification proposed by Dormans et expansile lesion with thin cortex and progressive [19] al . Treatment was in form of ILE, local adjuvant deformity[22]. therapy, and filling the cavity with HA. The Jaffe et al reported management of seven patients fracture was stabilized by DHS and anti-rotation with benign lesion of the femoral head and neck. screw. The hardware was removed two years after The diagnosis was fibrous dysplasia in four cases, surgery. At 47 month follow-up there was excellent aneurysmal bone cyst in two cases, and UBC in function, healing of the fracture without deformity one case. Curettage and autogenous fibular strut and complete consolidation of the cyst (Fig. 3a, b, graft in conjunction with a sliding hip screw were c). DHS was also applied to stabilize the fracture carried out in six cases. One case was treated by after surgical treatment in two cases classified as curettage and strut graft. The results were excellent 208 Management of Unicameral Bone Cyst of Proximal Femur: Experience of .... September 2008

Fig. 5a: Case # 11 pre-operative status. Fixation Fig. 5b: Shows mal-union with growth arrest Fig. 5c: Shows mal-union with growth arrest of could not be done due to sufficient bone of greater trochanter greater trochanter between the cyst and the growth plate to accommodate DHS, or lateral buttress to hold K wires.

Fig. 6a: Case # 7 shows the cyst involving head and neck of femur in five cases, good in one case and fair in one case. Fig. 6b: Shows CT scan of the cyst AVN of the femoral head developed in a case with pathological neck fracture through aneurysmal bone classification[19] for selection of fixation after surgical cyst[20]. Shih et al treated 35 cases of benign lesion of treatment. Type III-B matched two cases (case # 5 the femoral neck and inter-trochanteric area and 11 and 6) where DHS was applied. The femoral head out of them were UBC. The lesions were curetted, was completely destroyed by the cyst in two cases filled with cortical strut allo-graft and autogenic (case # 4 and 7, Fig. 6a, b, Fig. 7a). This type was iliac cancellous graft and fixed with sliding hip not included in Dorman’s classification and was screw. They reported excellent results[22]. difficult to fix. Case # 4 was stabilized by external In the present study six cases presented with hip fixator extending from the iliac bone to proximal pain without fracture. We tried to apply Dorman’s femur crossing the hip joint (Fig. 7 b). The treatment September 2008 KUWAIT MEDICAL JOURNAL 209

Fig. 7a: Case # 4 shows the femoral head Fig. 7b: Shows the use of external fixators for Fig. 7c: Shows the X-ray at 24 months follow- completely destroyed by cyst support after excision of the cyst up was designed to achieve healing of the cyst and to 3. Komiya S, Minamitani K, Sasaguri Y, Hashimoto S, prevent collapse of the articular surface. Our clinical Morimatsu M, Inouc A. Simple bone cyst: treatment by trepanation and studies on bone resorptive factors in cyst assessment at 24 months follow-up reported fluid with a theory of its pathogenesis. Clin Orthop Relat minimal pain and good range of movement. Res 1993; 287:204-211. Radiographic examination showed consolidation of 4. Neer CS, Francis KC, Johnston AD, Kiernan HA Jr. Current the cyst with mild narrowing of joint space (Fig. 7c). concepts on the treatment of solitary unicameral bone cyst. At that time no active intervention was indicated. Clin Orthop Relat Res 1973; 97:40-51. 5. Campanacci M, Capanna R, Picci P. Unicameral and However, when disability develops reconstructive aneurismal bone cysts. Clin Orthop Relat Res 1986; 204:25- procedures for the hip will be considered 36. accordingly. 6. Neer CS , Francis KC , Marcove RC, Terz J, Carbonara PN. Treatment of unicameral bone cyst; A follow-up study of one hundred seventy five cases. J Bone Joint Surg Am 1966; CONCLUSION 48:731-745. UBC of the proximal femur needs special 7. Scaglietti O, Marchetti PG, Bartolozzi P. The effect of consideration as it exhibits unique characteristics methylprednisolone actetate in the treatment of bone cysts. and complications. Each case should be evaluated Results of three years' followup. J Bone Joint Surg Br 1979; individually. HA matrix is useful and effective 61:200-204 . 8. Azouz EM , Karamitsos C, Reed MH, Baker L, Koslowski bone substitute particularly in the pediatric age K, Hoeffel JC. Types and complications of femoral neck group where there is limited supply of autogenic fractures in children. Pediatr Radiol 1993; 23: 415-420. bone graft. Post-excision stabilization of the cyst is 9. Capanna R, Dal Monte AD, Gitelis S, Campanacci M. recommended to avoid mal-union and to facilitate The natural history of unicameral bone cyst after steroid post-operative rehabilitation and earlier return injection. Clin Orthop Relat Res 1982; 166:204-211. 10. Czitrom AA, Pritzker KP. Simple bone cyst causing collapse to normal activities. Choice of internal fixation off the articular surface of the femoral head and incongruity depends on the location of the cyst, amount of bone of the hip joint. A case report. J Bone Joint Surg Am 1980; loss and skeletal maturity. The surgeon, the patient 62:842-845. and parents should be worried about the possible 11. Taneda H, Azuma H. Avascular necrosis of the femoral complications. epiphysis complicating a minimally displaced fracture of solitary bone cyst of the neck of the femur in a child , A case report. Clin Orthop Relat Res. 1994; 304:172-175. REFERENCES 12. Agerholm JC, Goodfellow JW. Simple cyst of the humerus treated by radical excision, J Bone Joint Surg Br 1965; 47:714- 1. Capanna R, Campanacci DA, Manfrini M. Unicameral and 717. aneurismal bone cysts. Orthop Clin North Am 1996; 27:605- 13. Fahey JJ, O’Brien ET. Subtotal resection and grafting in 614. selected cases of solitary unicameral bone cyst. J Bone Joint 2. Yu J, Chang SS, Suratwala S, et al. Zoledronate induces Surg Am 1973; 55:59-68. apoptosis in cells from fibro-cellular membrane of 14. Mckay DW, Nason SS. Treatment of unicameral bone cyst unicameral bone cyst (UBC). J Orthop Res 2005; 23:1004- by subtotal resection without graft. J Bone Joint Surg Am 1012. 1977; 59:515-519. 210 Management of Unicameral Bone Cyst of Proximal Femur: Experience of .... September 2008

15. Chigira M, Maehara S, Arita A, Uda Gawa E. The aetiology 24. Kaelin AJ, MacEwen GD. Unicameral bone cysts. Natural and treatment of simple bone cysts. JBone Joint Surg Br history and the risk of fracture. Int Orthop 1989; 13:275- 1983; 65:633-637. 282. 16. Shinozaki T, Arita S, Watanabe H, et al. Simple bone cyst 25. Gitelis S , Mallin BA , Piasechi P, Turner F. Intralesional treated by multiple drill – holes. Acta Orthop Scand 1983; excision compared with en block resection for giant cell 67:288-290. tumors of bone. J Bone Joint Surg Am 1993; 75:1648-1654. 17. Roposch A , Saraph V , Linhart WE. Flexible intramedullary 26. Inoue O, Ibaraki K, Shimabukuro H, Shingaki Y. Packing nailing for the treatment of unicameral bone cysts in long with high – porosity hydroxyapatite cubes alone for the bones. J Bone Joint Surg Am 2000; 82:1447-1453. treatment of simple bone cyst. Clin Orthop Relat Res 1993; 18. Roposch A, Saraph V, Linhart WE. Treatment of femoral 293:287-292. neck and trochanteric simple bone cysts. Arch Orthop 27. Hashemi-Nejad A, Cole WG. Incomplete healing of simple Trauma Surg 2004; 124:437-442. bone cysts after steroid injections. J Bone Joint Surg Am 19. Dormans JP, Flynn JM. Pathological fractures associated 1997; 79:727-730 . with tumors and unique conditions of the musculoskeletal 28. Delloye C, Docquier PL, Cornu O, et al. Simple bone cysts system. In: Rockwood CA Jr, Wilkins KE, Beatry JH, editors. treated with aspiration and a single bone marrow injection. Fractures in children 2000; Vol 3, 5th ed. Philadelphia: Int Ortho 1998; 22:134-138. Lippincott – Raven. 29. Chang CH, Stanton RP, Glutting J. Unicameral bone cysts 20. Jaffe KA, Dunham WK. Treatment of benign lesions of the treated by injection of bone marrow or methylprednisolone. femoral head and neck. Clin Orthop Relat Res 1990; 257:134- J Bone Joint Surg Am 2002; 84:407-412. 137. 30. Rougraff BT, Kling TJ. Treatment of active unicameral bone 21. Norman-Taylor FH, Hashemi-Nejad A, Gillingham BL, cyst with percutaneous injection of demineralized bone Stevens D, Cole WG. Risk of refracture through unicameral matrix and autogenous bone marrow. J Bone Joint Surg Am bone cysts of the proximal femur. J Pediatr Orthop 2002; 2002; 84:921-929. 22:249-254 . 31. Killian JT, Wilkinson L, White S, Brazard M. Treatment of 22. Shih NH, Cheng CY, Chen YJ, Huang TJ, Hsu RW. Treatment unicameral bone cyst with demineralized bone matrix. J of the femoral and trochanteric benign lesions. Clin Orthop Pediatr Orthop 1998; 18:621-624 . 1996; 328:220226. 32. Clark L. The influence of trauma on unicameral bone cysts. 23. Wai EK, Davis AM, Griffin A, Bell RS, Wunder JS. Clin Orthop 1962; 22:209-214. Pathological fracture of the proximal femur secondary to 33. Ortiz EJ, Isler MH, Navia JE, Canosa R. Pathological benign bone tumors. Clin Orthop Relat Res 2001; 393:279- fractures in children. Clin Orthop Relat Res 2005; 432: 116- 286 . 126.