The purpose of this retrospective study was to investigate and compare the clinical, radiographic, pathological, pathogenesis, and therapeutic features of simple bone cysts (SBCs) and aneurysmal bone cysts (ABCs) of the jaw.
35 patients with SBCs and 6 patients with ABCs who received treatment at the Department of Oral and Maxillofacial Surgery, Zhejiang University School of Medicine from 2017 to 2022 were followed up and reviewed retrospectively.
The study included 41 patients, accounting for 2.14% of all jaw pathologies, with 35 patients having SBCs and 6 patients having ABCs; their average ages were 26.63 ± 13.62 years and 17.83 ± 7.88 years, respectively. The prevalence of SBC and ABC did not differ significantly by sex. The mandible was the most vulnerable area to be involved. Only 5.71% (2/35) of patients with SBCs and 16.7% (1/6) of patients with ABCs reported histories of previous trauma in the same region of the pseudocysts. A total of 42.86% (15/35) of SBC cases and 66.67% (4/6) of ABC cases had malocclusions. The radiographic features of pseudocysts varied in shape, were associated with the root, and unilocular or multilocular. All patients had curettage with or without bone graft or substitute implantation, and recurrences did not occur in 94.29% (33/35) of SBC patients and 100% (6/6) of ABC patients after a mean follow-up time of 26.23 ± 15.47 months and 21.67 ± 19.75 months, respectively.
Pseudocysts, including SBCs and ABCs, are benign osteolytic lesions without an epithelial lining that occur occasionally in the jaw, mostly in adolescents and young adults, and their incidence did not significantly differ by sex. The most vulnerable site of involvement is the mandible, and they are generally not overtly aggressive. Trauma has a less significant role in pseudocysts, but minor trauma, such as malocclusion, has the potential to influence pseudocyst development. The clinical presentation of pseudocysts lacks specificity, and most patients are asymptomatic and found incidentally during radiographs. Dental panoramic radiographs and CBCT cannot accurately distinguish between SBC and ABC, and the final diagnosis depends on pathological diagnosis. Curettage combined with bone grafting is currently the best treatment for both, with a 5.71% (2/35) recurrence rate for SBC and no recurrence found for ABC.

Benign bone cysts in children have a high risk of recurrence after bone grafting. The optimal treatment and filling material for these lesions are currently unknown.
We compared cyst recurrence after intralesional curettage and filling with allograft versus bioactive glass (BG-S53P4; Bonalive) in a randomized clinical trial. The volume of recurrent cyst at 2-year follow-up was the primary outcome.
Of 64 eligible children, 51 (mean age, 11.1 years) were randomized to undergo filling of the cyst using morselized allograft (26) or bioactive glass (25). Twelve (46%) of the children in the allograft group and 10 (40%) in the bioactive glass group developed a recurrence (odds ratio [OR] for bioactive glass = 0.79, 95% confidence interval [CI] = 0.25 to 2.56, p = 0.77). The size of the recurrent cyst did not differ between the allograft group (mean, 3.3 mL; range, 0 to 13.2 mL) and the bioactive glass group (mean, 2.2 mL; range, 0 to 16.6 mL, p = 0.43). After adjusting for the type of lesion (aneurysmal bone cyst versus other), bioactive glass also did not prevent larger (>1 mL) recurrent cysts (adjusted OR = 0.42, 95% CI = 0.13 to 1.40, p = 0.16). The Musculoskeletal Tumor Society score improved significantly (p ≤ 0.013) from preoperatively to the 2-year follow-up in both groups (to 28.7 for bioactive glass and 29.1 for bone graft). Four (15%) of the children in the allograft group and 6 (24%) in the bioactive glass group required a reoperation during the follow-up (OR for bioactive glass = 1.74, 95% CI = 0.43 to 7.09, p = 0.50).
Filling with bioactive glass and with allograft in the treatment of benign bone lesions provided comparable results in terms of recurrence and complications.
Therapeutic Level I . See Instructions for Authors for a complete description of levels of evidence.

BACKGROUND: Aneurysmal bone cysts (ABC) are rare benign cystic bone tumors, generally diagnosed in children and adolescents. Proximal femoral ABCs may require specific treatment strategies because of an increased pathologic fracture risk. As few reports are published on ABCs, specifically for this localization, consensus regarding optimal treatment is lacking. We present a large retrospective study on the treatment of pediatric proximal femoral ABCs.
METHODS: All eligible pediatric patients with proximal femoral ABC were included, from 11 tertiary referral centers for musculo-skeletal oncology (2000-2021). Patient demographics, diagnostics, treatments, and complications were evaluated. Index procedures were categorized as percutaneous/open procedures and osteosynthesis alone. Primary outcomes were: time until full weight-bearing and failure-free survival. Failure was defined as open procedure after primary surgery, >3 percutaneous procedures, recurrence, and/or fracture. Risk factors for failure were evaluated.
RESULTS: Seventy-nine patients with ABC were included [mean age, 10.2 (±SD4.0) y, n=56 male]. The median follow-up was 5.1 years (interquartile ranges=2.5 to 8.8).Index procedure was percutaneous procedure (n=22), open procedure (n=35), or osteosynthesis alone (n=22). The median time until full weight-bearing was 13 weeks [95% confidence interval (CI)=7.9-18.1] for open procedures, 9 weeks (95% CI=1.4-16.6) for percutaneous, and 6 weeks (95% CI=4.3-7.7) for osteosynthesis alone ( P =0.1). Failure rates were 41%, 43%, and 36%, respectively. Overall, 2 and 5-year failure-free survival was 69.6% (95% CI=59.2-80.0) and 54.5% (95% CI=41.6-67.4), respectively. Risk factors associated with failure were age younger than 10 years [hazard ratios (HR)=2.9, 95% CI=1.4-5.8], cyst volume >55 cm 3 (HR=1.7, 95% CI=0.8-2.5), and fracture at diagnosis (HR=1.4, 95% CI=0.7-3.3).
CONCLUSIONS: As both open and percutaneous procedures along with osteosynthesis alone seem viable treatment options in this weight-bearing location, optimal treatment for proximal femoral ABCs remains unclear. The aim of the treatment was to achieve local cyst control while minimizing complications and ensuring that children can continue their normal activities as soon as possible. A personalized balance should be maintained between undertreatment, with potentially higher risks of pathologic fractures, prolonged periods of partial weight-bearing, or recurrences, versus overtreatment with large surgical procedures, and associated risks.
METHODS: Level IV, therapeutic study.

BACKGROUND: The aneurysmal bone cyst (ABC) is a benign, but locally aggressive cystic lesion of the bone. It usually occurs in the metaphysis of long bones of adolescents and young adults but can also affect the pelvis.
METHODS: This single-center study is a retrospective review of 17 patients with primary ABCs of the pelvis. It examines the importance of polidocanol instillations as minimally invasive treatment option for ABCs of the pelvis compared to intralesional curettage or marginal resection.
RESULTS: Seventeen patients with the diagnosis of a primary ABC of the pelvis were included in the study. Six patients were male (35%) and 11 patients female (65%); the mean age was 18 (9-49) years. The mean follow-up time was 50 months (12-136 months). The most common location of manifestation was the pubis (6; 35%), followed by the ilium (6; 35%), the sacrum (3; 18%) and the ischium (2; 12%). Eight patients were treated by intralesional curettage with the use of adjuvants, one patient by marginal resection, seven by sequential instillation of polidocanol and one patient by simple observation. Five patients received an additional transarterial embolization. After intralesional curettage local recurrence was detected in 4/8 cases (50%). After instillation therapy six patients (86%) had a stable disease without recurrence, only one patient (14%) had a persistent disease with need of additional treatment and was therefore converted to intralesional curettage without local recurrence in the follow-up.
CONCLUSIONS: Sequential instillations of polidocanol are a promising, minimally invasive treatment method for ABCs of the pelvis and can be well combined with transarterial embolization.

OBJECTIVE: Aneurysmal bone cyst (ABC) and telangiectatic osteosarcoma (TOS) share several clinical and imaging features, including young presentation, long bone involvement, lytic appearance on radiography and fluid-fluid levels on MRI. Therefore, they may be difficult to differentiate. The aim of this study is to identify clinical, radiological and MRI features which aid differentiation of the two lesions.
METHODS: Retrospective review of all histologically confirmed ABC and TOS over an 11-year period. Data recorded include age at presentation, sex, skeletal location and various radiographic and MRI features.
RESULTS: This retrospective study included 183 patients, 92 males and 91 females. Mean age at presentation of 18.4 years (range 1-70 years); 152 cases of ABC and 31 TOS. No significant difference between age and sex. TOS was significantly less likely to involve the axial skeleton; no difference related to location within the bone. Radiographic findings significantly favouring ABC included a less aggressive pattern of bone destruction, a purely lytic appearance, an expanded but intact cortex, no periosteal response and no soft tissue mass. MRI features significantly favouring ABC included smaller tumour size (maximum mean dimension 46 mm compared to 95 mm for TOS), absence of soft tissue mass, > 2/3 of the lesion filled with fluid levels and thin septal enhancement following contrast.
CONCLUSIONS: Several radiographic and MRI features aid in the differentiation between ABC and TOS. Lesions with a geographic Type 1A or IB pattern of bone destruction which are completely filled with FFLs on MRI can confidently be diagnosed as ABC.

Herein we described the clinical, radiological, histological, and molecular characteristics of seven soft tissue aneurysmal bone cysts (STABCs) diagnosed and managed at a tertiary cancer center and to elucidate their relationship with myositis ossificans (MO). All cases had established imaging and histopathological diagnosis of STABC and were subject to fluorescence in situ hybridization (FISH) for USP6 rearrangement and Archer® FusionPlex® targeted RNA sequencing (RNASeq) analysis to identify the fusion partner. A thorough literature review of STABC and MO was conducted. The patients presented with painful masses unpreceded by trauma, occurring most commonly in the deep soft tissue of the thigh/gluteus (4/7), and also in the supraclavicular region, the axilla, and the hand. On imaging, the lesions were frequently associated with peripheral calcification on conventional radiographs and CT (6/7), cystic components on ultrasound, as well as perilesional edema (7/7) and fluid levels (3/7) on MRI. Bone scan (1/1) showed intense radiotracer uptake. Histologically, 6/7 cases demonstrated zonal arrangements reminiscent of MO. USP6 rearrangement was found in all seven cases by FISH and/or RNASeq. RNASeq further detected COL1A1-USP6 fusion in six cases and a novel ANGPTL2-USP6 fusion in one case. Four patients underwent resection of the tumors and were disease free at their last follow-up. Three patients who underwent incisional or needle biopsies had no evidence of disease progression on imaging studies. In conclusion, the clinical, radiological, and pathological overlap between STABC and MO suggests that they are closely related entities. A novel fusion ANGPTL2-USP6 is associated with distinct clinical and pathological presentation.

An aneurysmal bone cyst (ABC) is a vascular locally proliferative, non-neoplastic, benign lesion observed in children and young adults. 75% of ABCs occur before the age of twenty. The cyst frequently develops in the long bones and comprises 1.4% of primary bone tumors. Spinal ABC is rare and is typically observed in the thoracic and cervical regions. In the spinal region, the posterior elements of a single vertebra are usually involved. The lamina, pedicle, facet joints are more commonly affected. The lesion may also expand toward the corpus. We present a case involving successful total excision of a lumbar spinal giant ABC by combining surgery with preoperative coil embolization. Preoperative arterial embolization contributes to decreased morbidity and mortality rates by reducing the duration of surgery and occurrence of intraoperative hemorrhage.

OBJECTIVE: The epidemiology and clinicopathology of aneurysmal bone cysts (ABCs) secondary to giant cell tumors of bone (GCTBs) have been well documented in the previous literature. However, reports on whether secondary ABCs could affect the postoperative recurrence of GCTBs are rare. This study analyzed the effects of secondary ABCs and other relevant clinical factors on the postoperative recurrence of GCTBs of the extremities.
METHODS: We retrospectively analyzed 256 cases of GCTBs of the extremities that were treated surgically at our institution. Among them, there were 60 patients diagnosed with GCTBs combined with secondary ABCs and 196 patients diagnosed with simple GCTBs. Intralesional curettage and tumor resection were performed in 136 and 120 cases, respectively. Univariate analysis, Kaplan-Meier survival analysis, and multivariate regression analysis were used to assess the factors for postoperative recurrence. The follow-up period was at least 24 months.
RESULTS: The total postoperative recurrence rate was 32%. The recurrence rate in the secondary ABCs group was significantly higher than that in the simple GCTBs group (53.3% vs 25.5%, P < 0.05). Curettage was associated with a higher recurrence rate than tumor resection (42.5% vs 20%, P < 0.05). Kaplan-Meier survival analysis showed that patients with GCTBs combined with secondary ABCs and who were treated by intralesional curettage had a decreased disease-free survival rate. The hazard ratio was 2.18 (95% confidence interval [CI], 1.15-4.13) for the group of GCTB combined with ABCs ( P = 0.01) and 1.97 (95% CI, 1.22-7.50) for the curettage group ( P = 0.01), respectively. Multivariate regression analysis revealed that the presence of secondary ABCs and curettage were independent factors for recurrence of GCTBs.
CONCLUSIONS: According to the results of this study, the presence of secondary ABCs is a potential risk factor for postoperative relapse of GCTBs.

METHODS: A retrospective observational study.
OBJECTIVE: Our aim is to define the efficacy and safety of serial selective arterial embolization (SAE) in the treatment of aneurysmal bone cysts (ABCs), to explore potential treatment alternatives, and to define a therapeutic algorithm.
BACKGROUND: ABC is a benign lesion with an unpredictable behavior. Its treatment is challenging especially in poorly accessible surgical areas, such as spine and pelvis. Currently, the first-line treatment of ABC is repeated SAE until healing. Other options have been used with variable success rates.
METHODS: From January 2004 to September 2015, 23 patients affected by ABC of the mobile spine have been treated with SAE and prospectively followed up by computed tomographic scan and magnetic resonance imaging. Signs of neurological deficit, complications, healing of the lesion, and clinical outcomes were registered.Signs of healing are defined as peripheral sclerotic bone rim formation, decrease of the ABC mass, disappearance of the double content image, and bone formation inside the ABC mass, associated with remission of pain.
RESULTS: Twenty-three patients underwent SAE according to the protocol. Seventeen patients have healed. The number of procedures necessary to obtain healing (clinical and radiographic) varied from 1 to 10. No complication occurred during the procedure. Follow-up time ranged from 5 to 120 months after the last angiographic procedure. All 17 patients had complete relief of pain symptoms. Six patients did not respond to SAE, presenting a progressive clinical and radiographic worsening, and underwent other medical or minimally invasive treatments.
CONCLUSIONS: Our study confirms the safety of SAE. The efficacy of the treatment was however lower than expected. SAE is indicated when pathological fracture or signs of cord damage are not detected. Infiltration with autologous bone marrow concentrate or administration of Denosumab is under investigation as alternative choices of treatment.
METHODS: 4.

Dextroscope three-dimensional (3D) imaging has been extensively applied for generation of virtual reality (VR) workspaces for in neurosurgery and laparoscopy, though few applications in orthopedic surgery have been reported. Patients undergoing surgery for periarticular tumors (n = 10) from Oct. 2008 to Jun. 2010 were enrolled and presurgically subjected to computed tomography (CT), magnetic resonance imaging (MRI), and MRI angiography (MRI-A). Imaging data was transferred and integrated in Dextroscope, producing a VR simulation. Resultant presurgical 3D anatomical reconstructions and intraoperative anatomical characteristics (virtual vs. actual data) and surgical approach (virtual vs. actual situation) measurement and subjective appearance were compared. Anatomical characteristics in the area of interest and tumor diameters were consistent between virtual and actual data. However, the virtual surgical situations remained inconsistent with the actual intraoperative situation in many cases, leading to complications. The resolution of original CT, MRI, and MRI-A images directly correlated with the quality of 3D simulations, with soft tissues most poorly represented. Tumor tissue imaging quality in 3D varied extensively by tumor type.
CONCLUSIONS: Anatomical structures of periarticular tumors can be reconstructed using the Dextroscope system with good accuracy in the case of simple fenestration, increasing individualization of treatment, surgical competence level, and potentially reducing intraoperative complications. However, further specialization of VR tools for use in orthopedic applications that involve specialized tools and procedures, such as drilling and implant placement, are urgently required.