Treatment for Unicameral Bone Cysts in Long Bones: an Evidence Based

Orthopedic Reviews 2010; volume 2:e13

Treatment for unicameral bone unknown, it is estimated that approximately 75% of children present with pathological frac- Correspondence: Sandra Donaldson, cysts in long bones: ture.1 Cysts heal in less than 15% of children Orthopaedic Surgery, The Hospital for Sick an evidence based review following fracture.2 Although unicameral bone Children, S107-555 University Ave, cysts are believed to resolve with skeletal Toronto, Ontario, M5G 1X8, Canada. E-mail: [email protected] Sandra Donaldson,1 Josie Chundamala,2 maturity, without treatment these children are 3 2 Suzanne Yandow, James G. Wright at risk for pain, or recurrent fracture leading to Key words: unicameral bone cyst, pediatrics, 1Orthopaedic Surgery, The Hospital for activity restriction for many years. treatment, levels of evidence. Unicameral bone cysts may also lead to Sick Children, Toronto, Ontario, Canada; growth disturbance. Growth arrest, a relatively Contributions: SD and JC, analysis and interpreta- 2Department of Surgery, The Hospital for uncommon complication, may occur through tion of data, drafting the article, final approval of Sick Children, Toronto, Ontario, Canada; many mechanisms. The disruptive, hydrody- the version to be published; SY, analysis and inter- 3 Orthopaedic Surgery, Central Texas namic assault of cyst fluid on the physis may in pretation of data, revising article for important intellectual content, final approval of the version to Pediatric Orthopedics, Austin, Texas, itself result in growth disturbances.3 Other USA be published; JGW, conception and design; analy- rare causes for growth arrest include multiple sis and interpretation of data, revising article for fractures through the cyst that damage the important intellectual content, final approval of the physis, direct extension of the cyst through the version to be published and funding. physis, or as a result of treatment of cysts adja- Abstract cent to the physeal plate.4-6 Regardless of the Conflict of interest: the authors report no con- cause, growth retardation in the affected limb flicts of interest. The purpose of this paper is to perform an may lead to angular deformity and/or limb 6 Received for publication: 12 March 2010. evidence based review for treatment of uni- length discrepancy. Revision received: 18 March 2010. cameral bone cysts. A search of MEDLINE Recurrent pathological fractures in children Accepted for publication: 19 March 2010. (1966 to 2009) was conducted and the studies with unicameral bone cysts require immobi- were classified according to levels of evidence. lization, and/or internal fixation, and restric- This work is licensed under a Creative Commons This review includes only comparative Level I- tion of activities. Recurrent fractures, particu- Attribution 3.0 License (by-nc 3.0). III studies. The systematic review identified 16 larly in the lower limb, may also cause limb length discrepancy and deformity. In addition, ©Copyright S. Donaldson et al., 2010 studies. There is one level I study, one level II Licensee PAGEPress, Italy study and the remaining 14 studies are level children are often afraid of their usual play Orthopedic Reviews 2010; 2:e13 III. Seven of the sixteen studies had statistical- activities or are restricted from all sporting doi:10.4081/or.2010.e13 ly different results: three studies indicated that activities by their parents or physician because steroid injection was superior to bone marrow of the concern of fracture(s). Finally, some injection or curettage and bone grafting; one children with unhealed cysts complain of pain.7 holes,12 cannulated screws,19 and different study indicated that cannulated screws were Although the origin of this pain is unclear, the types of nails.20 Many mixed methods approach superior to steroid injections; one study indi- pain seems to resolve with the healing of the the cyst on multiple levels such as percuta- cated resection and myoplasty was superior to cyst.8 Thus despite the benign nature of these neous removal of cyst lining, curettage to steroid injection; one study indicated a combi- lesions, unicameral bone cyst can have signif- break up septations, intramedullary decom- nation of steroid, demineralized bone matrix icant detrimental effects on otherwise normal pression, and injection of calcium sulfate pel- and bone marrow aspirate, and curettage and children and their families. 16 bone grafting were superior to steroid injec- Many theories have been proposed to lets. To date, few comparative studies have tion; and one study indicated that curettage explain the pathogenesis of unicameral bone been conducted (Table 1). The purpose of this and bone grafting was superior to non-opera- cysts. An early theory was that injury to the study was to perform an evidence based review tive immobilization. Based on one Level I growth plate leads to abnormal endochondral of treatment of unicameral bone cysts. study, including a limited number of individu- bone formation.9 Interest has also been drawn als, steroid injection seems to be superior to to the cyst lining and the presence of bone bone marrow injection. As steroid injections resorptive factors in the cyst fluid, including have already demonstrated superiority over interleukin 1-B and prostaglandin E210 and oxy- Materials and Methods bone marrow injections in a randomized clini- gen free radicals and lysosomes.11,2 Another cal trial, the next step would be a prospective theory suggests that vascular obstruction caus- A search of MEDLINE (1966 to 2009) was trial comparing steroid injections with other es cyst fluid to accumulate under pressure and conducted using the following search string: treatments. expand at the expense of the normal bone.3,10-11 Bone cysts/ and (unicameral or multi-cameral However, the uncertainty of the etiology has or simple). The search was limited to English led to a wide variety of treatments. language, humans and children aged 0 to 18 Treatment strategies for unicameral bone years. The studies had the following inclusion Introduction cysts include injection, mechanical disruption criteria: sample size greater than one; random- of the cyst lining and/or wall, structural sup- ized controlled trial or comparative study; cysts Simple, or unicameral, bone cysts are a port, decompression, or mixed methods. located in long bones; and all forms of treat- benign lesion in growing children. While the Injections can include steroids,13 bone mar- ment including observation or fracture immo- two terms are used interchangeably some row,14 demineralized bone matrix,15 calcium bilization. Studies were excluded if the cysts would argue that bone cysts are not “simple”, sulfate pellets,16 and fibrin sealant.17 were located in areas other than long bones, whereas the cysts are not always unicameral. Mechanical disruption of the cyst lining or wall i.e. calcaneus or pelvis. Studies with mixed Cysts are more common in males (70%) and is done by curettage. Structural support can be populations of cyst location were included, but typically present in the proximal humerus done with flexible intramedullary nailing.18 studies focusing exclusively on calcaneal cysts (70%) or femur (25%). While exact figures are Decompression can be done with multiple drill were excluded. Studies of mixed populations

[page 40] [Orthopedic Reviews 2010; 2:e13] Review

Table 1. Summary of Levels of Evidence I -III [N=1340]. Author Level Study Age of Follow-Up Definition Intervention Complications Outcome Year of design population years of evidence years healed

Wright I RCT Mean: 9.5 Mean: 2.2 Modified Neer / Steroid injection Fractures: 11 Steroid superior et al. 20077 Range: 2.8 to 17.1 Range: 1.5 to 3.3 Cole classification [n=38] Complications: 0 to bone marrow 4 grade scale, healing Autologous bone Fractures: 9 (P=0.01) defined as grades 3 or 4: marrow injection [n=39] Complications: 2 3) sclerosis around or within superficial infections a partially visible cyst; 4) complete healing with obliteration of cyst Brecelj II Prospective Mean: 9.8 Mean: 5.8 Chang classification Steroid injection Fractures: none reported Cannulated screw et al. 200719 comparative Range: 2.7 to 16 Range: 1 to 13.1 4 grade scale, healing defined [n=33] Complications: none reported superior to as grades 1 or 2: Curettage + bone Fractures: none reported steroid 1) Healed: cyst filled by formation grafting [n=8] Complications: none reported (P=0.001) of new bone with or without small Cannulated screw Fractures: complications: static radiolucent area(s) less than [n=28] 3 broken 1 cm in size; screws (left in place) 2) Healing with defect: static radiolucent area(s), less than 50% of the diameter of the bone with adequate cortical thickness to resist fracture. Sung III Retrospective Mean: 11.2 Mean: 4.7 Outcome defined as: Steroid injection Fractures: 17 SDB superior et al. 200821 comparative Range: Range: 0.08 to 27 Treatment failure (defined clinically as [n=94] Complications: 5 deformity/ to steroid injection not provided subsequent pathological fracture or need growth disturbance (P<0.001) for retreatment to prevent pathological Curettage and bone Fractures: 1 Curettage and bone fracture) or complications. grafting [n=39] Complications: grafting superior 3 deformity/ growth disturbance to steroid (P=0.01) SDB: Combination injection Fractures: 4 No difference of steroid, demineralized Complications: between curettage bone matrix, and bone 1 deformity/ growth disturbance and SDB (P=0.23) marrow aspirate [n=34] Cho III Retrospective Mean: 11.2 Mean: 4.7 Modified Neer classification Steroid injection [n=30] Fractures: 0 No difference et al. 200722 comparative Range: 2 to 18 Range: 2 to 15.5 4 grade scale, healing defined as 1 or 2: Autologous bone marrow Complications: none reported between treatment 1) Healed: cyst filled by new bone, with injection [n=28] Fractures: 3 groups (P>0.05) or without small radiolucent area(s) Complications: none reported <1 cm in size; 2) Healed with defects: radiolucent area(s)<50% of the diameter of bone, with enough cortical thickness to prevent fracture. Chuo III Retrospective Mean: 11.9 Mean 5.7 Modified Neer / Capanna classification Observation [n=6] Fractures: 0 No difference et al. 200323 comparative Range: 6 to 21 Range 2 to 12 4 grade scale, healing not defined Complications: between treatment beyond grades. 1 malunion (humerus) groups (P=0.42) 1) Completely healed Curettage + bone grafting + Fractures: 0 2) Healed with residue ORIF [n=4] Complications: none reported 3) Recurred Cannulated screw [n=7] Fractures: 0 4) No response Complications: none reported Chang III Retrospective Mean: 9.1 Mean: 3.7 Modified Neer classification Steroid injection [n=65] Fractures: 26 No difference et al. 200224 comparative Range: Range: 1 to 9 4 grade scale, healing defined as 1 or 2: Complications: none reported between groups Not provided 1) Healed: cyst filled by formation of new Autologous bone marrow Fractures: none reported (P>0.05) bone with or without small static, injection [n=14] Complications: none reported radiolucent area(s) less than 1 cm in size; 2) Healed with defect: static, radiolucent area(s) greater than 50% of the diameter of bone with enough cortical thickness to prevent fracture. Tsuchiya III Retrospective Mean: 15.2 Mean: 6.8 Not defined Curettage, multiple drilling Fractures: 2 No difference et al. 200225 comparative Range: 8 to 22 Range: 0.7 to 12.3 + titanium cannulated screws Complications: none reported between treatment [n=15] groups (P=0.12) Curettage, multiple Fractures: 0 drilling + cannulated Complications: none reported hydroxyapatite pin [n=11] Continued next page

[Orthopedic Reviews 2010; 2:e13] [page 41] Article

Table 1. Continued from previous page. Author Level Study Age of Follow-Up Definition Intervention Complications Outcome Year of design population years of evidence years healed

Bensahel III Retrospective Mean: 7 Mean: 9 Not defined Steroid injection [n=55] Fractures: 0 Resection and et al. 199826 comparative Range: 2 to14 Range: 3 to 15 Complications: 0 myoplasty superior to Resection + myoplasty [n=50] Fractures: 0 steroid injection Complications: 0 (P=0.02) Gennari III Retrospective Mean: 7 Mean: 6 Not defined Steroid injection [n=3] Fractures: 0 No difference et al. 199527 comparative Range: 3 to 13 Range: Complications: 0 between treatment Not provided Curettage + bone grafting Fractures: 2 groups (P=0.08) + ostesynthesis [n=10] Complications: 2 limb shortenings Rupture of cyst w/o Fractures: 2 osteosynthesis [n=5] Complications: 3 limb shortenings Orthopedic treatment [n=2] Fractures: 0 Complications: 1 limb lengthening Mylle III Retrospective Mean: 15 Mean: 8.5 Neer/Campanacci Classification Steroid injection [n=20] Fractures: 0 Steroid injection et al. 199228 comparative Range: Range: 4 grade scale, healed defined as 2 or 3: Complications: superior to Not provided Not provided 2) Incomplete healing: new bone 1 superficial infection curettage + formation fills the area previously Curettage +/- bone grafting Fractures: 0 bone grafting occupied by the cyst. Small sites of [n=21] Complications: (P=0.03) osteolysis remain visible in the 3 superficial infection boundaries of the cyst; Curettage + steroid Fractures: 0 3) Complete healing: the space injection [n=6] Complications: occupied by the SBC is completely filled 1 superficial infection by new bone or by hydroxyapatite. No treatment [n=12] Fractures: 10 Complications: 1 growth disturbance Farber III Retrospective Mean: 8.1 Mean: 6.7 Not defined Steroid injection [n=17] Fractures: none reported No difference et al. 199029 comparative Range: Range: Complications: 0 between Not provided Not provided Curettage Fractures: none reported treatment groups + bone grafting [n=19] Complications: 0 (P=0.27) Bovill III Retrospective Mean: 8.9 Mean: 5.6 Oppenheim and Galleno Steroid injection [n=12] Fractures: 3 No difference between et al. 198930 comparative Range: 0.75 to 30 Range: Modification Complications: 0 treatment groups Not provided 4 grade scale, healing defined as 1 or 2: Surgical treatment (multiple) Fractures: 1 (P=0.11) 1) Resolution: 70-100% obliteration and [n=15] Complications: renewed cortical thickening on serial X-ray; 3 limb deformity, 1 infection, 2) Incomplete resolution: 50-70% 1 median nerve palsy, obliteration with renewed cortical thickening. and 1 keloid. Non-surgical treatment Fractures: 0 (orthopedic) [n=5] Complications: 0 Pentimalli III Retrospective Mean: 9.1 Mean: 7 3 grade scale: Steroid injection [n=20] Fractures: none reported No difference between et al. 198731 comparative Range: 4-15 Range: (3 to 20) healing not defined further Complications: none reported treatment 1) Good: cyst had completely disappeared, Curettage + Fractures: none reported groups (P=0.29) the thickness of cortical bone was normal, bone grafting [n=20] Complications: none reported and no irregularity was present in the medullary canal; 2) Fair: cyst had disappeared, but the cortical bone was thinner than normal and some irregularities were evident inside the medullary canal; 3) Poor: cyst was still present, although reduced in volume, and/or there was shortening of the affected bone by more than 2 cm, with the bone slightly deformed at the site of the cyst. Continued next page

[page 42] [Orthopedic Reviews 2010; 2:e13] Review

Table 1. Continued from previous page. Author Level Study Age of Follow-Up Definition Intervention Complications Outcome Year of design population years of evidence years healed

Campanacci III Retrospective The majority C + BG Modified Neer classification Steroid injection [n=141] Fractures: 13 Steroid injection et al. 198632 comparative of these cases Mean: 4 grade scale, healing not defined further: Complications: superior to curettage were under not provided 1) Complete healing – the space occupied 28 limb length discrepancies, and bone grafting the age of Range: 1-35 by cyst was completely filled by new 1 avascular necrosis (P=<0.001) 15 years. SI bone formation; Curettage Fractures: none reported Mean: 2) Incomplete healing – new bone + bone grafting [n=178] Complications: 25 limb Not provided formation did fill the area previously length discrepancies Range: 1-8 occupied by the cyst; small sites of osteolysis were seen within the boundaries of the cyst; 3) Recurrence – initially the cyst was consolidated with new bone, and areas of osteolysis with definite cortical thinning appeared; 4) No response – no clinical or radiographic evidence of amelioration was noted. Oppenheim III Retrospective Mean: 74% Mean: 3.8 4 grade scale, healed defined as 1 or 2: Steroid injection [n=20] Fractures: none reported No difference between et al. 198433 comparative of cases Range: 0.5 to 12 1) Healed: complete obliteration Complications: 1 mild steroid treatment groups presenting of the cyst, or at most a 1 cm flush, 1 shortening of humerus (P=0.22) between the non progressive radiolucent Curettage or excision + Fractures: none reported ages of 5 and area and a serial increase grafting [n=37] Complications: 6, including 15 years. in cortical bone thickness; coxa vara, wound infection, Range: 1.5 to 26 2) Improved: Non progressive, physeal arrest and radiolucent areas 1-3 cm in diameter extremity shortening and enough cortical thickness to prevent fractures. Neer et al. III Retrospective Mean: 12.02 Mean: not provided 3 grade scale Curettage Fractures: 3 femoral Curettage + bone 1946 comparative Range: 1.5 to 54 Range: 1) excellent: complete + bone grafting [n=125] Complications: grafting superior non- operative obliteration of the cyst 1 wound infection, to non operative 1 to 10 during the period of observation; 4 premature immobilization 2) Residual defect: one or more static, epiphyseal closures (P<0.001) cyst-like residua with good bone Non-operative Fractures: 32 humeral, 4 femoral strength by the appearance immobilization after Complications: 4 growth of roentgenogram; fracture [n=45] disturbance/ deformity 3) Re-operation: subsequent operation required by recurrence. including children and adults were included as nal study then the associated P value was used. tions (pathological fractures, growth arrest, long as the mean age of patients ranged Second, if a P value was not provided but sta- limb length discrepancy); and 13 had an between 0 and 18 years. tistical data (absolute or relative) on cyst heal- English abstract but the paper was written in The following information was collected ing was available, then a c2 test was used to another language. This review included the from each of the studies: year of publication, calculate a P value. Cyst “healing” was defined results of 16 identified studies as listed in study design, age of patients, duration of fol- as “complete healing or partial healing (with Table 1. Years of publication span 1966 to 2009 low-up, definition/grading system for cyst heal- small residual cyst)” when a cyst graded scale and include a total number of 1,340 patients ing, treatment(s), sample size, and outcome. was specified. When cyst healing index was and 13 different types of treatment. Table 2 The studies were classified according to levels not specified, the author’s description of provides ranges of treatment success. There is of evidence as described in the Journal of Bone “healed” was used. one level I study, one level II study and the and Joint Surgery, where therapeutic studies remaining 14 studies are level III. Studies are are classified into five levels based on study presented chronologically by level, starting 34 35 design. This review includes levels I-III only. with the most current publications. Level I evidence consists of high quality ran- Results domized controlled trials and systematic reviews of level I studies with consistent Level I studies 7 results. Level II evidence includes lesser quali- The literature search yielded 263 articles In the one level I study, Wright et al. report- ty randomized controlled trials, prospective (Figure 1). Of these, 247 were excluded for the ed a randomized clinical trial comparing comparative studies, and systematic reviews of following reasons: 99 were levels IV or V (case intralesional bone marrow [n=39] and methyl- level II studies or level I studies with inconsis- series, editorial, or review article); 53 were prednisolone [n=38] injections. This trial tent results. Level III evidence consists of case- focused on non-long bones (calcaneal, involved 24 centers and 47 surgeons across control studies, retrospective comparative stud- mandible, pelvis); 36 were not therapeutic North America and India with follow-up of 2.2 ies, and systematic review of level III studies.34 (diagnostic or prognostic); 28 were differential years. Results of the trial indicated that steroid P values were obtained in two ways. First, if diagnosis (benign lesions or malignant injection (42% healed) was significantly better statistical analysis was performed in the origi- tumors); 18 focused on treatment of complica- than bone marrow (23% healed) for healing

[Orthopedic Reviews 2010; 2:e13] [page 43] Review bone cysts (P=0.01). The authors also found Table 2. Rates of success by treatment. that both subsequent fracture (P=0.04) and Treatment: N=1340 [n] Range of success (%) increased cyst area (P=0.03) were significantly associated with non-healing of the cyst. Steroid injection [563] 15-1007,19,21,22,24,26-33 Complications included 9 subsequent fractures Bone marrow injection [81] 23-9222,24 and 2infections in the bone marrow injection group, and 11 fractures and no infections in Curettage and bone grafting [447] 36-85 2,7, 19,21,28,29,31-33 the steroid group (P=0.12). Cannulated screw [35] 46-10019,23

021 Level II studies Steroid injection + DBM + bone marrow aspirate[34] 29-5 Curettage + bone grafting + ORIF [4] 7523 In the one level II study, Brecelj et al.19 compared steroid injection (n=33), curettage and Curettage + multiple drilling + titanium cannulated screw [15] 8025 bone grafting (n=8), and a specially designed Curettage + multiple drilling + hydroxyapatite pin [11] 10025 cannulated screw (n=28) in a prospective 26 comparative study with a follow-up of 5.8 years. Resection + myoplasty [50] 72 All three groups required multiple courses of Curettage + bone grafting + osteosynthesis [10] 10027 treatment. The cannulated screw group, after Cyst rupture + osteosynthesis [5] 6027 two attempts, demonstrated the highest rate of Orthopedic treatment [70] 4-1002,27,30 healing (P=0.001) at 65% compared to 50% and 19% for open curettage and methylpred- Mixed surgical treatment [15] 8730 nisolone injections, respectively. Complica- tions included three screws that broke during removal and were left in place. None of the fol- Figure 1. Literature lowing factors were related to treatment suc- search and review cess: sex, cyst size ratio, cyst activity, age at results. first treatment, pathological fractures or number of humeral cysts (with exception of second steroid injection, there were a higher number of humeral cysts in the failed treatment group [P=0.017]).

Level III studies The remaining 14 studies were level III. A retrospective study by Sung et al.21 compared steroid (n=94), curettage and bone grafting (n=39), and a combination injection (SDB) of steroid, demineralized bone matrix, and bone marrow aspirate. Results indicate that both curettage and bone grafting and the combination injection (SBD) were superior to steroid, P=0.01 and P<0.001 respectively. However, there was no difference between curettage and bone grafting and the combination injection (SBD) (P=0.23). Subsequent pathological fractures were reported in 18% (17/94) of patients treated with steroid injection, 2.6% (1/39) of patients treated with curettage, and 12% (4/34) of patients treated with the combination injection SDB. Other complications, (P<0.05) and needed more injections to com- of healing between treatment groups (P=0.42) such as deformity or growth disturbance, were plete healing (P<0.05). Cho et al. indicated was not statistically different. There was one reported in 5.3% (5/94) of patients treated with there was no association between healing complication of a malunion in the observation steroid injection, 7.7% (3/39) of patients treat- after the initial procedure and age, gender, group. ed with curettage and 2.9% (1/34) of patients location of the cyst, cyst activity or previous A retrospective study by Chang et al.24 com- treated with SDB. pathological fracture in either the bone mar- pared steroid (n=65) and bone marrow injec- A retrospective study by Cho et al.22 com- row or steroid group (P>0.05). Complications tions (n=14) with a follow-up of 3.7 years. pared bone marrow (n=28) and steroid (n=30) included three fractures after bone marrow Although there was no statistical difference injections with a follow-up of 4.7 years. The injections in patients who did not follow post- between treatment groups (P>0.05), the rate overall success rates were 86.7% after 2.5 operative immobilization instructions. of healing after 2 injections in the bone mar- injections in the steroid group and 92.0% after A retrospective study by Chuo et al.23 com- row group and 1.5 injections in the steroid 1.8 injections in the bone marrow group pared cannulated screws (n=7), curettage and group was 37% and 56%, respectively. No com- (P>0.05). Despite this lack of difference bone grafting with ORIF (n=4), and observa- plications were reported in either group. Cysts between treatment groups in the final out- tion (n=6) with a follow-up of 5.7 years. that healed after one injection (of either bone come, they found that the steroid group had a Although the authors concluded cannulated marrow or steroid) compared with those that higher recurrence rate after one injection screws were preferred, the difference in rates didn’t heal, had a significant difference in the

[page 44] [Orthopedic Reviews 2010; 2:e13] Review size of the cyst (P<0.01). Sex, cyst activity, pre- found between rates of healing in the treat- ly different results: three studies indicated that vious pathological fracture, and site of the cyst ment groups (P=0.11). There were eight com- steroid injection was superior to bone marrow had no affect on healing. plications in the surgical group: three leg injection or curettage and bone grafting;7,28,32 In 2002, Tsuchiya et al.25 retrospectively length deformities, one infection, one tran- one study indicated that cannulated screws compared curettage, multiple drilling and tita- sient median nerve palsy, one subsequent frac- were superior to steroid injections;19 one study nium cannulated screws (n=15) and curet- ture, and one keloid. There were three subse- indicated resection and myoplasty was superi- tage, multiple drilling and cannulated hydrox- quent fractures in the steroid group. or to steroid injection;30 one study indicated a yapatite pins (n=11) with a follow-up of 6.8 Pentimalli et al.31 retrospectively compared combination of steroid, demineralized bone years. The authors recommended the hydrox- steroid injections (n=20) and curettage and matrix and bone marrow aspirate, and curet- yapatite pins because the pins didn’t require bone grafting (n=20) with a follow-up of seven tage and bone grafting were superior to steroid removal. Although all patients receiving can- years. Although the authors recommend injection;21 and one study indicated that curet- nulated titanium screws healed, there was no steroid injections because the radiographic tage and bone grafting was superior to non- difference in healing between treatment results were better with a lower recurrence operative immobilization.2 In interpreting the groups (P=0.12). There were two complica- rate, the rates of healing for steroid injections literature the different treatments have differ- tions in the cannulated screw group (one frac- (95%) and curettage and bone grafting (85%) ent pros and cons. The treatments range from ture and one fissure fracture) and no compli- were not statistically different (P=0.29). No simple injections to open treatments to inter- cations in the hydroxyapatite pin group. complications were reported. nal fixation. The invasiveness must be con- Bensahel et al.26 retrospectively compared Campanacci et al.32 retrospectively compared trasted with the need for repeat treatment resection and myoplasty using a local muscle steroid injections (n=141) and curettage and such as steroids which may require multiple flap (n=50) and steroid injections (n=55) with bone grafting (n=178) with a follow-up of one injections. These factors must all be balanced a follow-up of nine years. Resection and to 35 years (mean not provided). Although the against risk of fracture and probability of suc- myoplasty compared with steroids had a high- authors indicated the end results were compa- cess. er rate of healing of 71% and 50%, respectively rable in both groups, the steroid group had The literature has several shortcomings. (P=0.02). There were no complications report- higher rates of healing than curettage on bone First, the outcome for almost all studies ed in either group. grafting (P<0.0001), 91% and 68%, respective- (15/16) was based on radiographic healing Gennari et al.27 retrospectively compared ly. The steroid group had 28 limb length dis- rather than patient based outcomes such as steroid injection (n=3), curettage and bone crepancies, 13 subsequent fractures, and one fracture, pain or function. Second, there was grafting and osteosynthesis (n=10), rupture of avascular necrosis. The curettage and bone variability in the type of radiographic healing cyst without osteosynthesis (n=5), and obser- grafting group had 25 limb length discrepan- scale or index used. Eight of the sixteer stud- vation (or “orthopedic treatment”) (n=2) in cies. ies used a modification of the Neer criteria, cysts in the upper third of the femur with a fol- Oppenheim et al.33 retrospectively compared four did not define the scale or index used, and low-up of six years. There was no difference in steroid injections (n=20) and curettage or four used their own original criteria. Third, rates of healing between treatment groups excision with or without grafting (n=37) with there was a wide variation in treatment proto- (P=0.08). There were two limb shortenings a follow-up of 3.8 years. There was no differ- cols. For example, although all steroid injec- (<2 cm) in the curettage group, three shorten- ence in rates of healing between steroid injection protocols used methylprednisolone ings (≥2 cm) in the cyst rupture group, and tion (40%) and the curettage group (57%) acetate, the dosage ranged from 40 to 250 mg one lengthening (>2 cm) in the observation (P=0.22), although the authors recommended and number of injections ranged from one to 6. group. the steroid injection due to its simplicity and Bone marrow injection protocols also varied Mylle et al.28 retrospectively compared reduced morbidity. Complications included one including amount withdrawn from each har- steroid injection (n=20), curettage and bone mild steroid flush (2.4 g dose of Depo Medrol vest site (2-8 mL), amount injected into cyst grafting (n=21), curettage and steroid injec- was inadvertently given) and one shortening (9-50 ml), and number of injections (1-4). tion (n=6), and no treatment (n=12) with a of the humerus in the steroid group. There Fourth, there was different duration of follow- follow-up of 8.5 years. Steroid injection was were 6 complications in the curettage group up with the mean ranging from 2.2 to 9.0 years found to be superior to curettage and bone which included coxa vara, wound infection, and overall range from one to 35 years. Finally, grafting (P=0.03) with 90% and 43% healing, physeal arrest, and extremity shortening. the studies had a variety of sample sizes, rang- respectively. Complications included one Neer et al.2 retrospectively compared curet- ing from very small (n=2) to 178. superficial infection in the steroid group, three tage and bone grafting (n=125) with immobi- As unicameral bone cysts and corresponding in the curettage and bone grafting group, and lization after fracture (n=45) with a minimum pathological fractures present in different one in the curettage and steroid injection 2-year follow-up. Curettage and bone grafting locations, variations in treatment may result. group. There were ten subsequent fractures had higher rates of healing than the non-oper- Pathological fractures in the lower extremi- and one growth disturbance in the ‘no treat- ative treatment (P<0.001), 77% and 4%, ties, particularly in the proximal femur, have ment’ group. respectively. Complications for the non-opera- greater potential for complications. Farber et al.29 retrospectively compared tive group included subsequent fractures in 36 Fracture(s) in this area may result in physeal steroid injections (n=17) and curettage and patients and 4 growth disturbances and defor- damage, coxa vara, extremity shortening or bone grafting (n=19) with a follow-up of 6.7 mity. Complications for the curettage group avascular necrosis.27,36 As cysts rarely heal fol- years. Although methylprednisolone has high- were 3 subsequent fractures, one wound infec- lowing fracture,36,37 risk of refracture leads to er rates of healing of 70% compared with 53% tion, and 4 premature epiphyseal closures restriction of physical activities. As failure to in the curettage group, the difference was not which led to shortening of 1-3 cms. achieve radiographic healing within the first statistically different (P=0.27). No complica- year following presentation increases the risk tions were reported. of refracture,38 the goal of treatment is to stabi- Bovill et al.30 retrospectively compared lize the fracture and treat the cyst simultane- steroid injections (n=12), multiple surgical Discussion ously. Flexible intramedullary nails have been techniques (n=15), and observation (n=5) promoted as they stabilize the fracture (or with a follow-up of 5.6 years. No difference was Seven of the sixteen studies had statistical- pending pathological fracture) and provide

[Orthopedic Reviews 2010; 2:e13] [page 45] Review treatment of the cyst through continuous cyst. J Prosth Orthotics 1998;18:198-201. study. J Prosth Orthotics B 2007;16;5:367- decompression.39-45 Advantages of this treat- 4. Cohen J. A current synthesis of reported 72. ment include stability to the bone and early cases. Orthop Clin of N A 1977;8:715-36. 20. Bumci I, Vlahovic T. Significance of open- mobilization of the patient. Complications 5. Tachdjian MO. Pediatric Orthopaedics ing the medullar canal in surgical treat- include nail revisions due to bone growth and 1990,1271-1. Philadelphia, W.B. Saunders. ment of simple bone cyst. J Prosth difficulty of anchoring nails due to lack of bone 6. Haims AH, Desai P, Present D, Beltran J. Orthotics 2002, 22;1:125-9. in the femoral neck.41 Epiphyseal extension of a unicameral 21. Sung AD, Anderson ME, Zurakowski D, et There are few reports in the literature on bone cyst. Skeletal Radiol 1997;26:51-4. al. Unicameral bone cyst: a retrospective prophylactic internal fixation of bone cysts at 7. Wright JG, Yandow S, Donaldson S, Marley study of three surgical treatments. Clin risk for pathological fracture in the proximal L. A randomized clinical trial comparing Orthop Relate Res 2008;466:2519-26. femur.39,41,44,45 These reports are case series with intralesional bone marrow and steroid 22. Cho HS, Oh JH, Kim H-S, et al. Unicameral the majority of patients presenting with patho- injections for simple bone cysts. J Bone bone cysts: a comparison of injection of logical fractures. The authors acknowledge the Joint Surg 2008;90-A:722-30. steroid and grafting with autologous bone numbers for cysts treated prophylactically with 8. Hashemi-Nejad A, Cole WG. Incomplete marrow. J Bone Joint Surg 2007;89- internal fixation are small but indicate they healing of simple bone cysts after steroid B;2:222-6 see no difference in rates of cyst healing when injections. J Bone Joint Surg 1997;79- 23. Chuo C-Y, Fu Y-C, Chien S-H, et al. compared to cysts treated with concurrent B;727-30. Management strategy for unicameral bone pathological fracture. 9. Jaffe H, Lichtenstein L. Solitary unicamer- cyst. Kaohsiung J Med Sci 2003;19:289-95. Treatment for unicameral bone cysts has al bone cyst, with emphasis on the roent- 24. Chang CH, Stanton RP, Glutting J. evolved over the years. Curettage and bone gen picture, pathologic appearance and Unicameral bone cysts treated by injection grafting was used for many years.5 pathogenesis. Arch Surg 1942;44:1001-25. of bone marrow or methylprednisolone. J Unfortunately, this aggressive approach had 10. Watanabe H, Arita S, Chigira M. A etiology Bone Joint Surg 2002;84-B;3:407-12. high recurrence rates of 40-50% with the asso- of a simple bone cyst. Int Orthop 1994; 25. Tsuchiya H, Abdel-Wannis ME, Uehara K, ciated scar and morbidity of surgery.32 A less 18:16-9. et al. Cannulation of simple bone cysts. 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