Preventing of nonunion in congenital pseudarthrosis of the tibia cases of Crawford Type I and II through the use of allograft bypass and a brace: Midterm findings.

Background: Congenital pseudarthrosis of the tibia is a limb deformity, which can be distressing for the affected patients and the pediatric orthopedic surgeons involved. We hypothesized that the modified McFarland procedure would avoid fractures and even have a corrective effect on the affected tibia in congenital pseudarthrosis of the tibia patients. Toward this end, we evaluated the midterm results of treating congenital pseudarthrosis of the tibia patients of Crawford Type I and II with allograft bypass combined with long-term bracing. Methods: This study retrospectively evaluated 7 patients with congenital pseudarthrosis of the tibia who were treated with allograft bypass combined with long-term bracing between 2009 and 2018. The median follow-up was 7.0 years (range 3.8-10.0 years). The medical records and radiographs were reviewed for demographic data, clinical characteristics, outcomes, and complications. Results: At the time of the last follow-up, all allografts revealed complete consolidation in the patients' tibiae at both ends. All patients presented no functional restriction of the lower limbs and no amputation or non-union has occurred. Most of the obvious deformities of the tibia diaphysis or ankle joint were corrected. Two complications occurred that required successful revision surgery. Conclusion: In this series of seven congenital pseudarthrosis of the tibia patients, the allograft bypass technique showed satisfactory midterm results and validated our hypothesis. For congenital pseudarthrosis of the tibia patients of Crawford Type I and II, this procedure combined with long-term bracing, which involves the affected leg only, can delay or possibly prevent fractures, decrease tibial malalignment, and preserve leg length. Level of evidence: level IV.

Synovial sarcoma: the misdiagnosed sarcoma.

Synovial sarcoma is a rare and highly malignant soft tissue sarcoma. The inconspicuous and diversity of its early symptoms make it a highly misdiagnosed disease. The management of synovial sarcomas is challenging as they are rare and have a poor prognosis. Early and correct diagnosis and treatment are critical for clinical outcomes. Misdiagnosis or delayed diagnosis can have devastating consequences for the patient. The detection of SS18 gene rearrangement is considered a powerful tool in establishing the diagnosis of synovial sarcomas. Biopsies and testing for gene rearrangements are recommended for all patients in whom SS cannot be excluded. Surgery is the mainstay of treatment for synovial sarcomas. Neoadjuvant/adjuvant radiotherapy is recommended for patients with big tumors (>5 cm) or positive resection margins, and neoadjuvant/adjuvant chemotherapy is recommended for patients with high-risk tumors or advanced diseases. This article reviews synovial sarcomas from the perspectives of clinical and radiological presentation, histological and cytogenetic analysis, differential diagnosis, treatment, and prognosis.

Vascularized Growth Plate Transfer in Paediatric Ulna Non-Union: Operative Technique and Review of the Literature.

Congenital pseudarthrosis of forearm fractures is rare and is strongly associated with neurofibromatosis type 1 (NF1). Our case report illustrates the progression of a non-union of the ulna after minor trauma in a twelve-year-old boy, newly diagnosed with NF1, and presents the technique of microsurgical bone reconstruction, including the growth plate. More than seven years after the first operation, follow-up presents a favorable outcome with a pain-free patient and unrestricted function of the forearm after a secondary correction of the remaining radial bowing. This treatment is discussed with a comprehensive review of the current literature on ulnar congenital pseudarthrosis in PubMed and Google Scholar and free fibular growth plate transfer in PubMed and Google Scholar. Nine publications reporting on 20 cases of congenital ulnar non-unions were identified. With this reconstructive option, favorable outcomes were achieved in all cases with the union after primary surgery and complications requiring further surgeries in nine cases. The benefit of vascularized growth plate bone transfer in congenital ulna non-union seems to be significant compared to other therapies such as open reduction internal fixation (ORIF), non-vascularized bone grafts, or one-bone-forearms and beneficial when growth reconstruction is needed. Other techniques might be necessary to improve insufficient long-term results.

Conservative and Surgical Treatment of Osteochondromas in Children, Particularly with or without Surgical Lengthening of the Ulna.

Prevention of rotatory impairment and radial head dislocation in the forearm is an important aspect when treating children with osteochondromas. Various studies tried to determine the best treatment, describing different surgical techniques. No consensus has been reached yet. This retrospective study compares the treatment outcome of patients with osteochondroma of the radius and ulna after surgical or conservative treatment. Seventeen forearms treated over a period of 20 years were analysed. Outcome parameters were the prospectively collected clinical data and the radiological findings: "relative shortening" of ulna/radius, the "radial articular angle" (RAA) and the "carpal slip" (CS). Our study shows an improvement of the range of motion and cosmetic appearance of the forearm after an operative procedure, with or without bone lengthening. We observed an increase in wrist and elbow mobility with a decrease in pain scores and a confirmed high cosmetic satisfaction in almost 70% of the patients after bone lengthening and up to 85% after simple excision. For patients suffering from functional impairment or pain, an operative approach is beneficial. Multiple and repetitive osteochondroma excisions are recommended during growth to prevent deformity and rotatory motion restriction. Lengthening procedures require a careful indication.

Exploring the Potential of Electronic Patient-Reported Outcome Measures to Inform and Assess Care in Sarcoma Centers: A Longitudinal Multicenter Pilot Study.

BACKGROUND: Electronic patient-reported outcome measures (ePROMs) are useful tools to assess care needs of patients diagnosed with cancer and to monitor their symptoms along the illness trajectory. Studies regarding the application of ePROMs by advanced practice nurses (APNs) specialized in sarcoma care and the use of such electronic measures for care planning and assessing quality of care are lacking. OBJECTIVE: To explore the potential of ePROMs in clinical practice for assessing the patient's quality of life, physical functionality, needs, and fear of progression, as well as distress and the quality of care in sarcoma centers. METHODS: A multicenter longitudinal pilot study design was chosen. Three sarcoma centers with and without APN service located in Switzerland were included. The instruments EQ-5D-5L, Pearman Mayo Survey of Needs, the National Comprehensive Cancer Network Distress Thermometer, PA-F12, and Toronto Extremity Salvage Score were used as ePROMs. Data were analyzed descriptively. RESULTS: Overall, 55 patients participated in the pilot study; 33 (60%) received an intervention by an APN, and 22 (40%) did not. Patients in sarcoma centers with APN service reported overall higher scores in quality of life and functional outcome. The number of needs and distress level were lower in sarcoma centers with APN service. No differences were found with respect to patients' fear of progression. CONCLUSIONS: Most of the ePROMs proved to be reasonable in clinical practice. PA-F12 has shown low clinical relevance. IMPLICATIONS FOR PRACTICE: Using ePROMs appears to be reasonable to obtain clinically relevant patient information and to evaluate the quality of care in sarcoma centers.

Long-term effects of retrograde approach on the knee after motorized femoral limb lengthening.

BACKGROUND AND PURPOSE: The retrograde femoral approach is an established technique for implantation of nails for leg lengthening and correction and in cases of distal femoral fractures. The purpose of this study was to determine the 10-year outcome of this technique by analyzing the clinical long-term effects and radiological status of the knee after leg lengthening via a retrograde femoral approach. PATIENTS AND METHODS: This retrospective single-center study included 13 patients (median age at surgery 17 [range 15-20] years) who underwent unilateral, retrograde, femoral lengthening with a motorized nail. Outcome measurements were graded variables of the SF-36, ISKD score, and Lysholm score. MRI of both knees was performed in all patients. MRI was evaluated for the presence of degenerative changes and compared with the healthy contralateral knee. Cartilage condition was graded according to the International Cartilage Repair Society (ICRS) scoring system. RESULTS: All patients were pain-free and had a full range of motion 10 (range 10.0-12.2) years after surgery. All postoperative knees showed fibrosis of Hoffa's fat pad and moderate to severe cartilage defects (ICRS Grade 2-4) of the trochlear groove (nail entry site). 6 out of 13 operated knees exhibited retropatellar cartilage defects. CONCLUSION: Our study showed that patients were pain-free, but cartilage defects at the entry point and arthrofibrosis at Hoffa's fat pad were observed without causing clinical impairment.

How much is a leg worth following radical tumor resection in bone sarcomas? Literature review.

Bone sarcomas of the lower extremities are rare malignancies occurring mostly amongst adolescents and young adults. Necessarily, the therapy conducted in sarcoma centers is multimodal and multidisciplinary. In certain cases, in a metastasis free situation with adequate therapy, an overall survival rate of 90% can be achieved. Two principal surgical procedures exit for the local control of the malignancy: 1. Limb salvage with biological with/or endoprosthetic reconstruction; and, 2. amputation with restoration of the function with exoprosthesis or endo-exoprosthesis. Currently, limb salvage procedures are performed in up to 95% of cases. In contrast, amputation is performed when the disease has reached an advanced stage or limb salvage has failed. Both of the surgical options have their risks and possible complications. According to the literature, there should be no significant difference between limb salvage and amputation with respect to long-term overall survival, overall quality of life, psycho-socio-economic outcomes, or patient satisfaction. An important advantage of limb salvage is greater everyday functionality. With the expanded indication of limb salvage and great survival rates, the cases of late complications in patients expecting to maintain their own leg continues to increase. In some cases, it requires multiple interventions, ranging from minor up to the most complex revisions, to maintain the functionality of the extremity. Despite the great costs, personal effort, and the possible complications, limb salvage could be a suitable method to achieve functionally beneficial outcomes and patient satisfaction in bone sarcomas of the lower extremities over the long-term even in cases involving complications.

Vascularized and Non-vascularized Fibula Grafts in Tumour Reconstruction: Single Centre Experience With Mid to Long-term Results.

BACKGROUND/AIM: Vascularized (VFG) and non-vascularized fibula grafts (NVFG) are used in reconstruction of bone defects after tumour resection. This study compared both autografts and their results, risk factors, and complications. PATIENTS AND METHODS: Tumour resection and reconstruction by using VFG (n=17) and NVFG (n=36) were performed in 53 patients at our institute (range=3-65 years of age, mean: 21.2 ± 13.2 years) of which 24 were female. Malignant tumours were diagnosed in 26 patients (VFG=16 patients-94%). The mean follow-up was 14.9 years (range=1.5-43 years). Factors like consolidation, functional and oncologic outcomes, and complications were analysed. RESULTS: In total, 75 struts of fibula were obtained. The mean length of the fibula was 16.3 cm (16 in NVFG and 16.5 in VFG). The mean union time was 13 months (6 to 25 months) overall. Hypertrophy was found in 65 of 75 grafts (86.7%) and consolidation was found in 69 (92%). Hypertrophy was similar in VFG (85.3%) and NVFG (87.1%). Complication rate in VFG was 41% and in NVFG 25%. Fractures were found in 7 (13%), infections in 4 (7.5%), and non-union in 5 (9.4%) patients. Chemotherapy was the only negative prognostic factor for union time (p=0.021). CONCLUSION: Both VFG and NVFG are used with successful results in the reconstruction of segmental bone tumour defects. With lower complication rates, NVFG showed comparable results to VFG but is limited in indication by size for greater defects, and malignant tumours. Chemotherapy is an adverse factor leading to prolonged union time in both techniques.

[Proximal femoral varus osteotomy in Legg-Calve-Perthes disease]. / Proximale Varisationsosteotomie des Femurs beim Morbus Perthes.

OBJECTIVE: The proximal femoral varus osteotomy (FVO) aims to re-centre the femoral head in the acetabular socket after prognostically unfavourable subluxation, e.g. in Legg-Calve-Perthes disease (LCPD). INDICATIONS: No unified indication criteria have been defined yet for containment therapy in LCPD. However, specific radiographic features related to deformity development, age at diagnosis or onset and classifications describing pathomorphological changes in the femoral head related to bone necrosis can support decisionmaking. CONTRAINDICATIONS: Absolute contraindications-a hinge abducted joint; failure of femoral head reduction in the 20° abduction anteroposterior view; total epiphyseal necrosis. Relative contraindication-children < 6 years, in lateral pillar classification group A or Catteral group I and II. SURGICAL TECHNIQUE: Lateral approach to the proximal femur. Insertion of the first K­wire to mark the anteversion of the femoral neck. Additional K­wires are placed parallel to the first via the positioner aiming block. Lokalise the optimal postion for the osteotomy. Insertion of additional K­wires in the distal fragment an facilitate manipulation and serve as reference for derotation. After osteotomy proximal fixation of the plate with locking screws replacing the K-wires. Insertion of a cortical screw into the middle hole to achieve optimal interfragmentary compression. Remaining locking screws are inserted and cortical screw replaced by a locking screw. POSTOPERATIVE MANAGEMENT: Mobilization with heel-touch weight-bearing on crutches for 6 weeks. Increased weightbearing after radiographic follow-up as soon as sufficient bone union is present. Implant removal after 9-12 months. Return to sports after 3 months. RESULTS: The FVO has been used in the surgical treatment of severe LCPD for nearly 60 years and is established worldwide. Growing knowledge and consecutive optimization of the surgery indication together with the new implants contribute to improving clinical and radiological outcomes and reducing intraoperative and postoperative complications.

The "true" acetabular anteversion angle (AV angle): 2D CT versus 3D model.

INTRODUCTION: Different factors can lead to inconsistencies in measurement for the acetabular version using 2D axial CT-cuts. We have defined a "true" anteversion angle (AV angle) in the physiological position of the pelvis in 3D with the largest European population measured to our knowledge. MATERIAL AND METHODS: We analyzed 258 hemipelvises and created 3D models. We compared the results of our AV angle 3D method with the cross-sectional cuts of the same acetabula. We included factors like side, sex, body mass index, and patient positioning. RESULTS: Overall, the mean (SD) AV angle was 16.1 (5.9)° as measured with the 3D method and 22.0 (6.0)° as measured with the 2D method (p < 0.0001). Measured with both the 3D and the 2D method, the AV angle was significantly larger in female than in male individuals (p < 0.0001). In the 2D method, the AV angle estimation was influenced by the pelvic tilt. CONCLUSION: We propose a more accurate method for the measurement of the AV angle of the acetabulum in a 3D model that is not influenced by patient positioning or pelvic tilt. We provide a computational model that will facilitate operative decisions and improve preoperative planning. We confirm that 3D measurement should be the gold standard in measuring the acetabular anteversion.

Personalized 3D-printed guide in malignant bone tumor resection and following reconstruction - 17 cases in pelvic and extremities.

INTRODUCTION: Customized accurate tumor resection and individualized reconstruction is a challenging in treatment of malignant bone tumor. Three-dimensional (3D)-printing technique is now widely used in the resection and following reconstruction of malignant bone tumor, which included but not limited to tumor model, osteotomy guide and customized implant. METHODS: We retrospectively reviewed 17 patients, who underwent limb salvage surgery by using 3D-printed guide at a single center between August 2014 and October 2019. The median duration of follow-up was 26.5 months. Osteosarcoma (41.2%) were the predominant diagnoses. The functional outcomes were assessed by Musculoskeletal Tumor Society (MSTS) functional score. We also analyzed survival status, intraoperative data (blood loss, operation time and resection length), reconstruction method, margin outcomes and complications. RESULTS: We totally performed 93 guided osteotomies on affected bone and allograft bone in 17 patients. Reconstruction in 12 cases was performed with biological technique: allograft combined with autograft was used in 7 cases. 11 of 12 (91.7%) cases showed a good bone healing in both allograft and autograft. 1 of 12 (8.3%) cases had allograft necrosis. Additional intra-operative extracorporeal radiation was performed in 3 pelvic cases for reconstruction. 63 of 64 (98%) osteotomies achieved wide resection and negative margin. All the cases had successful limb salvage result without amputation. At the latest follow up, the mean MSTS Score was 24 (range: 13-30), 12 patients alive with no evidence of disease, 1 patient alive with disease, 5 patients had died of disease and 5 years overall survival is 73.3%. The most common complications are wound healing disorder in 4 cases (23.5%) and infection in 3 cases (17.6%). CONCLUSION: The 3D-printed resection guide was easy to use and showed promise in the field of orthopedic oncology. It can not only used in primary malignant bone tumor personalized resection but also in shaping structural bone allograft in biological reconstruction, which can achieve a safety surgical margin and individualized resection at the same time.

Methylation and copy number profiling: emerging tools to differentiate osteoblastoma from malignant mimics?

Rearrangements of the transcription factors FOS and FOSB have recently been identified as the genetic driver event underlying osteoid osteoma and osteoblastoma. Nuclear overexpression of FOS and FOSB have since then emerged as a reliable surrogate marker despite limitations in specificity and sensitivity. Indeed, osteosarcoma can infrequently show nuclear FOS expression and a small fraction of osteoblastomas seem to arise independent of FOS/FOSB rearrangements. Acid decalcification and tissue preservation are additional factors that can negatively influence immunohistochemical testing and make diagnostic decision-making challenging in individual cases. Particularly aggressive appearing osteoblastomas, also referred to as epithelioid osteoblastomas, and osteoblastoma-like osteosarcoma can be difficult to distinguish, underlining the need for additional markers to support the diagnosis. Methylation and copy number profiling, a technique well established for the classification of brain tumors, might fill this gap. Here, we set out to comprehensively characterize a series of 77 osteoblastomas by immunohistochemistry, fluorescence in-situ hybridization as well as copy number and methylation profiling and compared our findings to histologic mimics. Our results show that osteoblastomas are uniformly characterized by flat copy number profiles that can add certainty in reaching the correct diagnosis. The methylation cluster formed by osteoblastomas, however, so far lacks specificity and can be misleading in individual cases.

FGF-23 transmitted tumor - induced hypophosphatemic osteomalacia: A rare case of a young woman with recurrent fractures and review of the literature.

We present a case of tumor-induced osteomalacia (TIO) in a young woman of 22 years. The fibroblast growth factor 23 transmitting tumor in her left foot remained undetected for several years. She suffered several fractures including insufficiency fractures of both femoral necks requiring bilateral proximal femoral nailing. After phosphaturia was diagnosed any known genetic etiology was excluded. Even advanced imaging modalities were unable to detect the clinically silent tumor until an 68Ga-DOTA-TOC-PET/CT-scan revealed a mass with paraneoplastic activity in the left foot. Complete resection of the tumor proved to cure her condition after 9 years of uncertainty and suffering. Serum phosphate levels returned to normal within days. After presentation of the case report, the current literature on published cases of TIO between 1956 and 2021 is summarized to emphasize the importance of an accurate and early diagnosis. Our case report aims to illustrate that a long latency period of diagnosis may be avoided utilizing the latest imaging techniques to spare affected patients from long treatment of symptoms instead of finding the underlying cause.

Vascularized Bone Graft Reconstruction Following Bone Tumor Resection at a Multidisciplinary Sarcoma Center: Outcome Analysis.

BACKGROUND/AIM: Limb-sparing procedures are frequently applied to improve patient outcomes. The use of vascularized bone grafts is associated with significant improvements in oncologic safety and functional satisfaction. This study highlights the clinical outcomes following tumor resection combined with vascularized bone graft reconstructions. PATIENTS AND METHODS: Twenty-five free vascularized bone grafts (17 fibulas, 5 iliac crests, 3 medial femoral condyles) were assessed with respect to consolidation and hypertrophy, functional and oncologic outcomes, and local complications. RESULTS: The rate of healing of fibular grafts after a median of 5 months was 86%. The rate of achieved unions of iliac crest grafts after a median of 5 months was 80%. In medial femoral condyle bone grafts, union occurred after a median of 4 months. Significant hypertrophy was observed in 13 patients. We identified six complications with highest rates in the fibula-group. Despite the high complications, functional results were highly satisfactory. CONCLUSION: Vascularized bone grafts represent a reconstructive approach, maintaining long-term functionality and cosmetic satisfaction without compromising tumor recurrence outcomes.

Primary malignant bone tumours of spine and pelvis in children.

PURPOSE: Axial malignant bone tumours are rare in children and adolescents, and their prognosis is still relatively poor due to non-specific symptoms, such as back or groin pain, which may result in late hospital presentation. Therefore, it is very important to raise awareness regarding this pathology. METHODS: We performed a narrative review, including scientific publications published in English. We searched Medline and Google Scholar databases for information on the incidence and prognosis of axial malignant bone tumours in children and adolescents (< 18 years). Outcomes of different surgical management strategies and reconstruction options were assessed. RESULTS: The incidence of primary malignant bone tumours before the age of 18 years is approximately five per one million population; around 25% of these tumours are located in the axial skeleton. With a five-year survival rate of 50%, tumours in an axial location (chest cage, spine, pelvis) are associated with a poorer prognosis than tumours in more peripheral locations. En bloc excision with clear margins has been shown to improve local control and overall survival, even though obtaining adequate surgical margins is difficult due to the close location of large neurovascular structures and other major organs. Spinal reconstruction options include instrumented fusion with allograft or expandable cage. Pelvic reconstruction is needed in internal hemipelvectomy, and the options include biological, endoprosthetic reconstructions, hip transposition, arthrodesis or creation of pseudoarthrosis and lumbopelvic instrumentation. CONCLUSION: Early diagnosis, a timely adequate multidisciplinary management, appropriate en bloc excision, and reconstruction improve survival and quality of life in these patients. LEVEL OF EVIDENCE: V.

Severe Acute Lung Injury After H2O2 Irrigation of an Aneurysmal Bone Cyst in an 8-Year-Old Girl: A Case Report.

An 8-year-old girl developed severe acute lung injury after irrigation of a pelvic aneurysmal bone cyst with H2O2 and filling with bone cement. Sudden profound oxygen desaturation occurred on the operating table when the patient was turned from the prone to the supine position. After a brief improvement in her oxygenation, the girl developed rapidly progressing severe respiratory failure necessitating reintubation and hour-long manual ventilation, while copious amounts of hemorrhagic frothy fluids were aspirated through the endotracheal tube. The patient started to improve after 24 hours and eventually made a full recovery. We hypothesize that the incident was caused by gas embolization and pulmonary endothelial damage by H2O2.

Overactivation of the IGF signalling pathway in osteosarcoma: a potential therapeutic target?

Osteosarcoma is the most common primary malignant bone tumour in children and adolescents. More than a third of patients do not respond to standard therapy and urgently require alternative treatment options. Due to a high degree of inter- and intra-tumoural genomic heterogeneity and complexity, recurrent molecular alterations that could serve as prognostic predictors or therapeutic targets are still lacking in osteosarcoma. Copy number (CN) gains involving the IGF1R gene, however, have been suggested as a potential surrogate marker for treating a subset of patients with IGF1R inhibitors. In this study, we screened a large set of osteosarcomas and found specific CN gains of the IGF1R gene in 18 of 253 (7.1%) cases with corresponding IGF1R overexpression. Despite the discouraging results observed in clinical trials in other tumours so far, focusing only on selected patients with osteosarcoma that show evidence of IGF pathway activation might represent a promising new and innovative treatment approach.

Long-Term Outcomes of Acute Osteoarticular Infections in Children.

Background: Acute hematogenous osteomyelitis (OM) and septic arthritis require immediate diagnosis and treatment by an interdisciplinary team of pediatric infectious disease specialists and pediatric orthopedic surgeons. Adverse outcomes such as growth disturbance, bone deformity, and chronic infections have been described in older studies. However, there is only little known about long-term follow-up of patients of the last two decades. Therefore, we aimed to evaluate subjective and objective long-term outcomes of these children with osteoarticular infections treated in the millennial years. Methods: Cross-sectional study performed in two pediatric centers including patients admitted for OM and/or SA between 2005 and 2014 and follow-up consultations in 2019. Patients with symptoms of ≤2 weeks duration at initial presentation were contacted. Subjective outcomes were assessed by standardized interview, objective outcomes by clinical examination. Medical charts were used to extract data from the initial presentations. Statistical analysis was performed by non-parametric tests and Fisher's exact test. Results: Of 147 eligible patients 77 (52%) agreed to participate, of which 68 (88%) had an interview and physical examination and 9 (12%) an interview only. Thirty-three (39%) had OM, 26 (34%) SA, and 21 (27%) combined OM/SA. Median (IQR) age at follow-up was 13.3 (10.5-18.0) years with a median (IQR) follow-up of 7.1 (6.1-8.6) years. Persistent complaints including pain, functional differences and scar paresthesia, reported by 21 (28%) patients, were generally mild and only 3 (5%) required ongoing medical care. Objective sequelae including pain, limited range of motion, unilateral axis deformity or asymmetric gait were found in 8 (12%) participants. Older age, female sex, joint involvement, surgical intervention, persistent fever, and C-reactive protein elevation were associated with adverse clinical outcome. Conclusions: Adverse outcomes were observed in a considerable number of patients, most of which were minor, and only few required ongoing medical care. Long-term follow up is advisable for patients with risk factors identified during the initial presentation. This study was registered on ClinicalTrials.gov (NCT03827980).

Percutaneous cyst aspiration with injection of two different bioresorbable bone cements in treatment of simple bone cyst.

INTRODUCTION: Simple bone cysts (SBCs) are common in children and adolescents. The risk of refracture and the probability of spontaneous healing in SBCs are mainly dependent on the activity of the cyst and can be quantified with the Cyst-Index. Avoiding pathological fractures is the primary goal. Our study presents a comparison of two different bioresorbable bone graft substitutes (BGSs) in the minimally-invasive treatment of SBC in the active stage by percutaneous cyst aspiration and injection. METHODS: Between 2006 and 2017, 38 patients (aged two to 37 years; mean age 12.4 (sd 5.6)) were treated with percutaneous cyst aspiration and refilled with bioresorbable BGSs in three hospitals. The cysts of 21 patients (11 humerus, five femur, four calcaneus, one fibula) were refilled with porous beta-tricalcium phosphate (PB-TP group) (ChronOS Inject) and of 17 patients (nine humerus, six femur, one calcaneus, one fibula) with hydroxyapatite/calcium sulphate (H/CS group) (CERAMENT|BONE VOID FILLER). There were 13 (62%) preceding fractures in the PB-TP group and eight (47%) in the H/CS group. The follow-up of all patients was at least two years. During follow-up, radiological healing (modified Neer classification), activity level, refracture rates, recurrence rates, resorption period and complications were analyzed. RESULTS: In all, 21 patients treated with PB-TP group experienced 27 operations (one refracture, three recurrences and one persistent cyst). A total of 17 patients treated with H/CS experienced 20 operations (one refracture and one recurrence). After six weeks, 95% in the PB-TP group returned to unrestricted activity with one refracture in the femur due to insufficient biomechanical stability and all returned to unrestricted activity in the H/CS group. Partial or complete radiological response was observed in 81% after 13 months (sd 3.4). Three recurrences (14%) occurred in the PB-TP group and one recurrence (6%) occurred in the H/CS group. The refracture rates were similar in both groups; one (5%) in the PB-TP group and one (6%) in the H/CS group. All H/CS treated cysts showed completed resorption after two years, whilst in PB-TP treated cysts no resorption occurred in five cases (25%) (p = 0.031). Two (10%) wound infections occurred in the PB-TP group and no infections occurred in the H/CS group. CONCLUSION: Both PB-TP and H/CS can provide stability and prevent refracture in patients with single bone cysts at the upper extremity or the foot. For the proximal femur, additional stabilization is necessary, due to the weight-bearing and associated high refracture rate. The H/CS bone graft substitute has a better resorption rate than the PB-TP graft. LEVEL OF EVIDENCE: III.