Osteochondroma Pathogenesis: Mouse Models and Mechanistic Insights into Interactions with Retinoid Signaling.

Osteochondromas are cartilage-capped tumors that arise near growing physes and are the most common benign bone tumor in children. Osteochondromas can lead to skeletal deformity, pain, loss of motion, and neurovascular compression. Currently, surgery is the only available treatment for symptomatic osteochondromas. Osteochondroma mouse models have been developed to understand the pathology and the origin of osteochondromas and develop therapeutic drugs. Several cartilage regulatory pathways have been implicated in the development of osteochondromas, such as bone morphogenetic protein, hedgehog, and WNT/ß-catenin signaling. Retinoic acid receptor-γ is an important regulator of endochondral bone formation. Selective agonists for retinoic acid receptor-γ, such as palovarotene, have been investigated as drugs for inhibition of ectopic endochondral ossification, including osteochondromas. This review discusses the signaling pathways involved in osteochondroma pathogenesis and their possible interactions with the retinoid pathway.

Understanding the Action of RARγ Agonists on Human Osteochondroma Explants.

Osteochondromas are cartilage-capped growths located proximate to the physis that can cause skeletal deformities, pain, limited motion, and neurovascular impingement. Previous studies have demonstrated retinoic acid receptor gamma (RARγ) agonists to inhibit ectopic endochondral ossification, therefore we hypothesize that RARγ agonists can target on established osteochondromas. The purpose of this study was to examine the action of RARγ agonist in human osteochondromas. Osteochondroma specimens were obtained during surgery, subjected to explant culture and were treated with RARγ agonists or vehicles. Gene expression analysis confirmed the up-regulation of RARγ target genes in the explants treated with NRX 204647 and Palovarotene and revealed strong inhibition of cartilage matrix and increased extracellular matrix proteases gene expression. In addition, immunohistochemical staining for the neoepitope of protease-cleaved aggrecan indicated that RARγ agonist treatment stimulated cartilage matrix degradation. Interestingly, cell survival studies demonstrated that RARγ agonist treatment stimulated cell death. Moreover, RNA sequencing analysis indicates changes in multiple molecular pathways due to RARγ agonists treatment, showing similarly to human growth plate chondrocytes. Together, these findings suggest that RARγ agonist may exert anti-tumor function on osteochondromas by inhibiting matrix synthesis, promoting cartilage matrix degradation and stimulating cell death.

Osteochondroma of the Pubic Symphysis Involved With Aberrantly Placed Minisling: A Case Report.

Osteochondromas are benign bone tumors that rarely involve the pubic symphysis. This case report describes a 41-year-old woman with a pubic symphyseal osteochondroma associated with an aberrantly placed single incision sling. After an outside surgeon placed a single incision midurethral sling for stress urinary incontinence, she developed pelvic pain, dyspareunia and vaginal mesh sling exposure. Imaging demonstrated a 2.6 centimeter calcified mass posterior to the pubic symphysis. The patient underwent excision of the mass and the eroded mesh sling via vaginal and abdominal approaches. Pathology demonstrated osteochondroma aggregated around mesh. This is a rare case of a single incision sling placed aberrantly into a pubic symphyseal osteochondroma that required excision.

An Unusual Presentation of Carney Complex

Carney complex (CNC) is a multiple neoplasia syndrome, characterized by pigmented lesions of the skin and mucosa, cardiac, cutaneous and other myxomas and multiple endocrine and non-endocrine tumors. Most of the cases have an inactivating mutation in the PRKAR1A gene. Osteochondromyxoma (OMX) is an extremely rare myxomatous tumor of bone, affecting 1% of CNC patients. Large cell calcifying Sertoli cell tumor (LCCSCT) is a testicular tumor affecting more than 75% of males with CNC. Here, we report an atypical case of CNC without typical pigmented skin lesions, presenting with a bone based tumor as the first manifestation. Initial presentation was for a recurrent, locally invasive intranasal tumor without definite diagnosis. Further clinical developments during follow up, central precocious puberty and testicular tumor with calcification, led to the diagnosis of LCCSCT, a CNC-related tumor. Histopathologic examination of the intranasal tumor was re-evaluated with this knowledge and OMX was diagnosed. Coexistence of OMX and LCCSCT suggested CNC. Genetic analysis revealed a heterozygous non-sense p.Trp 224* (c.672G>A) in the PRKAR1A gene. In our case, the diagnosis of OMX was delayed, because it is extremely rare and little is known about this tumor. Thus the aim of this report was to alert other clinicians to consider CNC if OMX is diagnosed.

Effect of Distal Ulna Osteochondroma Excision and Distal Ulnar Tether Release on Forearm Deformity in Preadolescent Patients With Multiple Hereditary Exostosis.

BACKGROUND: Multiple hereditary exostosis is a benign condition that can lead to significant forearm deformity secondary to physeal disturbances. As the child grows, the deformity can worsen as relative shortening of the ulna causes tethering, which may lead to increased radial articular angle, carpal slippage, and radial bowing, over time this tethering can also result in radial head subluxation or frank dislocation. Worsening of forearm deformities often require corrective reconstructive osteotomies to improve anatomic alignment and function. The purpose of this study is to evaluate the effectiveness of osteochondroma excision and distal ulnar tether release on clinical function, radiographic anatomic forearm alignment, and need for future corrective osteotomies. METHODS: The authors reviewed a retrospective cohort of preadolescent patients who underwent distal ulna osteochondroma resection and ulnar tethering release (triangular fibrocartilage complex). Patients were invited back and prospectively evaluated for postoperative range of motion, pain scores, self-reported and parent-reported Disabilities of the Arm, Shoulder, and Hand (DASH) and Pediatric Outcomes Data Collection Instrument (PODCI) scores. In addition, preoperative and final postsurgical follow-up forearm x-rays were reviewed. RESULTS: A total of 6 patients and 7 forearms were included in our study with an average age of 7.9 years at time of surgery. The average final follow-up was 7.4 years. With respect to range of motion, only passive radial deviation demonstrated improvement -20 to 14 degrees (P=0.01). Although there was not statistically significant change in radial articular angle, this study did find an improvement in carpal slip 75.7% to 53.8% (P=0.03). At final follow-up DASH score was 5.71 (σ=5.35), PODCI Global Function score was 95.2 (σ=5.81), and PODCI-Happiness score 98 (σ=2.74). Visual analogue scale appearance and visual analogue scale pain assessment were 1.67 (σ=1.21) and 1.00 (σ=1.26), respectively, at final follow-up. No patient in the cohort developed a radial head dislocation. Only one of 7 forearms required a corrective osteotomy within the study's follow-up time period. CONCLUSIONS: Surgical excision of forearm osteochondromas with ulnar tether release in the preadolescent patients improves carpal slip, may help to prevent subsequent surgical reconstruction and provides satisfactory clinical results at an average 7-year follow-up. LEVEL OF EVIDENCE: Level III-therapeutic study.

Talar-sided osteochondral lesion of the subtalar joint following the intra-articular calcaneal fracture: study via a modified computed tomography mapping analysis.

INTRODUCTION: This study is to report the prevalence of osteochondral lesions in subtalar joint following intra-articular calcaneal fracture, including the relationship between fracture severity and lesion characteristics, using modified computed tomography (CT) mapping analysis. METHODS: Thirty patients with intra-articular calcaneal fracture who were preoperatively imaged with modified CT mapping analysis were recruited. The presence of talar-sided osteochondral lesions (OLTS) of subtalar joint was noted with lesion area defined by Akiyama's mapping classification. Lesion severity was assessed via Ferkel's classification, and fracture severity via Sanders' classification. RESULTS: Lesions were found in 28 patients (93.3%), mostly at anterior [16 (57.1%) lesions] or central [13 (46.4%) lesions] areas of posterior talar facet. Most common grade of lesion severity was grade I (mild) seen in 24 (80%) patients. Most fractures were classified as Sanders' grade III and IV with 12 (40%) and 12 (40%) patients noted, respectively. High severity of fracture denoted by Sanders' grade IV showed a trend of higher prevalence of OLTS at anterior and central sites of posterior talar facet (P = 0.181). Lesion severity was significantly higher in patients with double lesions than patients with single lesions (P = 0.005). However, OLTS were not significantly related with osteoarthritic changes in follow-up radiographs (P > 0.05). CONCLUSIONS: The prevalence of OLTS is very high following intra-articular calcaneal fractures. Most lesions occur at anterior or central area of posterior talar facet and are more likely to occur in patients with higher fracture severity. Lesion severity was significantly higher in patients with double lesions than patients with single lesions.

Is Routine Spine MRI Necessary in Skeletally Immature Patients With MHE? Identifying Patients at Risk for Spinal Osteochondromas.

BACKGROUND: Multiple hereditary exostoses (MHE) is an autosomal dominant condition leading to development of osteochondromas throughout the body. Although long bones are most often affected, spine involvement may occur and usually requires advanced imaging for diagnosis. However, the high cost of detection, infrequent occurrence, and very low likelihood of spinal cord compression and neurological injury, create a management conundrum. The purpose of our investigation is to identify patients at greatest risk for spinal lesions and refine indications for advanced imaging. METHODS: All MHE patients in a 24-year period were retrospectively reviewed. Skeletally immature patients with advanced imaging of the spine were further evaluated. The demographic characteristics, family history, clinical presentation, past surgical history, tumor burden, and distribution of patients with spinal lesions were compared with those without. RESULTS: In total, 227 MHE patients were identified and 21 underwent advanced spinal imaging. Spinal lesions were found in 8 of the 21 screened patients (38.1%, 3.5% overall), of which 4 were intracanal and 1 was symptomatic (4.8%, 0.4% overall). Only the symptomatic patient underwent excision of the spinal lesion. Patients with spinal lesions had higher tumor burden than those without (median, 28.5 vs. 19 locations; P=0.010). There was a significant association with rib (P=0.018) and pelvic (P=0.007) lesions, which may serve as "harbinger" lesions. The presence of both a rib and a pelvic lesion used as a screening tool for spinal lesions produces a sensitivity of 100% and specificity of 69%. CONCLUSIONS: Symptomatic spinal involvement in children with MHE is rare and tends to occur in patients with higher tumor burden. We recommend limiting advanced spine imaging to children with neurological symptoms or with rib and pelvic "harbinger" lesions. Patients without these findings are unlikely to have spine involvement needing intervention. This approach offers an opportunity to avoid unnecessary testing and substantially reduce costs of diagnostic imaging. LEVEL OF EVIDENCE: Level III.

Fibrodysplasia ossificans progressiva: a current review of imaging findings.

OBJECTIVE: Fibrodysplasia ossificans progressiva is a rare genetic disorder characterized by congenital skeletal deformities and soft tissue masses that progress to heterotopic ossification. Deformities of the great toes are distinctive, and heterotopic ossification in the soft tissues follows an expected anatomic and temporal pattern. In addition to heterotopic ossification, osteochondromata, middle ear ossification, demyelination, lymphedema, and venous thrombosis are characteristic. Awareness of this constellation of findings is important to early diagnosis and surveillance. CONCLUSIONS: Recognition of the imaging manifestations of fibrodysplasia ossificans progressiva is imperative to early diagnosis in order to appropriately direct patient care and preclude unnecessary biopsies or surgical procedures.

Osteocondromas traqueales, hallazgo casual / Tracheal osteochondromas, accidental finding

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Osteochondral mosaicplasty along with osteochondroplasty of the femoral head in femoroacetabular impingement: a case report.

Although femoroacetabular impingement (FAI) syndrome is included in the etiology of lesions involving the acetabular labrum and acetabular cartilage, it is one of many possible reasons behind osteochondral lesions in the femoral head. Herein, we present clinical findings and outcomes of two cases with osteochondral defects and cam type impingement of femoral head. Both cases underwent autologous osteochondral mosaicplasty along with femoral osteochondroplasty following controlled hip dislocation. Harris hip scores improved significantly postoperatively and magnetic resonance imaging showed an adequate graft union and formation of a healthy chondral surface at the final assessment. Autologous osteochondral mosaicplasty of parafoveal region defects and femoral neck osteochondroplasty combination may be an effective treatment method for young patients with FAI syndrome. In addition, we believe that cam type impingement may also have a role in the etiology of parafoveal osteochondral lesions.

Osteochondroma: ignore or investigate? / Osteocondroma: ignorar ou investigar?

Osteochondromas are bone protuberances surrounded by a cartilage layer. They generally affect the extremities of the longbones in an immature skeleton and deform them. They usually occur singly, but a multiple form of presentation may be found. They have a very characteristic appearance and are easily diagnosed. However, an atypical site (in the axial skeleton) and/or malignant transformation of the lesion may sometimes make it difficult to identify osteochondromas immediately by means of radiographic examination. In these cases, imaging examinations that are more refined are necessary. Although osteochondromas do not directly affect these patients' life expectancy, certain complications may occur, with varying degrees of severity...

Osteocondromas são protuberâncias ósseas envolvidas por uma camada de cartilagem. Atingem, habitualmente, as extremidades dos ossos longos no esqueleto imaturo e os deformam. Em geral são únicos, mas a forma de apresentação múltipla pode ser encontrada. De aspecto bastante característico, são de fácil diagnóstico. Contudo, por vezes, a localização atípica (esqueleto axial) e/ou a malignização da lesão podem dificultar a sua pronta identificacão por exames radiográficos. Nesses casos, exames de imagem mais apurados são necessários. Apesar de não afetarem diretamente a expectativa de vida do portador, algumas complições, com variados graus de gravidade, podem ocorrer...

A bizarre parosteal osteochondromatous proliferation (Nora's lesion) of metatarsus, a histopathological and etiological puzzlement.

Nora's lesion (bizarre parosteal osteochondromatous proliferation) is a rare, benign lesion that is composed of differing amounts of cartilage, bone, and spindle cells and an unusual form of calcified cartilage so-called "blue bone". Whether it represents a reactive proliferation or a neoplastic lesion still remains controversial. We present a 24-year-old woman having a 4.5cm two lobulated mass attached to second metatarsus of her left foot. The lesion was hyperintense on magnetic resonance imaging and accompanied by an extensive soft tissue and bone marrow edema. In resection specimen, smaller lobule appeared stuck-on the cortex while the larger one had a broader base and a 0.4cm cartilaginous cap-like formation. The histological picture was best fit to Nora's lesion however showed less fibroblastic tissue and cartilaginous pleomorphism. The lesion also showed areas with cortical invasion and a small focus of fracture callus accompanied by adjacent medullary edema and fat necrosis. The case is presented with the comparative radiologic, macroscopic and microscopic findings for its diagnostic difficulties and etiopathogenetic considerations in favour of a maturation phenomenon in parosteal ostecartilaginous lesions irrespective of the cause.

Osteochondromas after radiation for pediatric malignancies: a role for expanded counseling for skeletal side effects.

BACKGROUND: A relationship has been reported between total body irradiation (TBI) and later development of osteochondromas in children who receive radiation therapy as conditioning before hematopoietic stem cell transplantation (HSCT). The goal of this study was to better characterize osteochondromas occurring in these children. METHODS: We identified all children (0 to 18 y) who received an allogeneic HSCT and TBI from 2000 to 2012 from a blood and marrow transplant (BMT) database. Thereafter, we identified those who developed osteochondromas through a chart review. In addition, we searched for diagnosis and operative codes from 1996 to 2012 in our pediatric orthopaedic clinical records, isolating osteochondroma patients with a history of radiation exposure. RESULTS: Four patients who underwent allogeneic HSCT and were later diagnosed with osteochondromas were identified from the BMT database (N=233 children); all 4 were among a group of 72 patients who received TBI. Three patients were identified from orthopaedic records. The cohort included 5 boys and 2 girls with acute lymphoblastic leukemia (N=5) or neuroblastoma (N=2), diagnosed at a median age of 2.0 years. Therapy for all patients included chemotherapy, radiation therapy (TBI, N=5; abdominal, N=2), and HSCT. A diagnosis of osteochondroma was made at a median age of 11.7 years (range, 5 to 16 y), on average 8.6 years after radiation therapy. Diagnosis was incidental in 2 patients and secondary to symptoms (pain or genu valgum) in 5. Locations of osteochondromas were the proximal tibia (N=3), distal tibia, distal femur, distal ulna, and the distal phalanx (N=1 each). Three patients underwent surgical resection. CONCLUSIONS: Children may be more likely to develop osteochondromas after early exposure to radiation therapy, which may cause pain and require surgical resection. To the best of our knowledge, this is the first reported case of a radiation-induced osteochondroma causing lower extremity malalignment. Patients typically present to the pediatric orthopaedist's attention when symptomatic, but there may be an expanded role for counseling for potential for long-term skeletal effects in this group. LEVEL OF EVIDENCE: Level IV, case series.

Exostoses as a long-term sequela after pediatric hematopoietic progenitor cell transplantation: potential causes and increase risk of secondary malignancies from Ann & Robert H. Lurie Children's Hospital of Chicago.

Allogeneic hematopoietic progenitor cell transplantation (HPCT) is a curative therapy for pediatric patients with both malignant and nonmalignant diseases. Single or multiple benign exostoses or osteochondromas have been reported after total body irradiation (TBI), as well as after focal irradiation. Patients exposed to TBI at a young age are at highest risk of developing exostoses. The objective of this institutional review board-approved study was to look at potential factors, besides radiation, that may play a role in development of exostoses. All patients who underwent allogeneic and autologous HPCT at a single institution between March 1992 and December 2003 and who developed an exostosis identified by clinical findings or as an incidental finding on a radiologic study were included. A case-control design matched patients with controls who had the same stem cell source.

Cell biology of osteochondromas: bone morphogenic protein signalling and heparan sulphates.

Frequent benign outgrowths from bone known as osteochondromas, exhibiting typical endochondral ossification, are reported from single to multiple lesions. Characterised by a high incidence of osteochondromas and skeletal deformities, multiple hereditary exostoses (MHE) is the most common inherited musculoskeletal condition. While factors for severity remain unknown, mutations in exostosin 1 and exostosin 2 genes, encoding glycosyltransferases involved in the biosynthesis of ubiquitously expressed heparan sulphate (HS) chains, are associated with MHE. HS-binding bone morphogenetic proteins (BMPs) are multifunctional proteins involved in the morphogenesis of bone and cartilage. HS and HS proteoglycans are involved in BMP-mediated morphogenesis by regulating their gradient formation and activity. Mutations in exostosin genes disturb HS biosynthesis, subsequently affecting its functional role in the regulation of signalling pathways. As BMPs are the primordial morphogens for bone development, we propose the hypothesis that BMP signalling may be critical in osteochondromas. For this reason, the outcomes of exostosin mutations on HS biosynthesis and interactions within osteochondromas and MHE are reviewed. Since BMPs are HS binding proteins, the interactions of HS with the BMP signalling pathway are discussed. The impact of mouse models in the quest to better understand the cell biology of osteochondromas is discussed. Several challenges and questions still remain and further investigations are needed to explore new approaches for better understanding of the pathogenesis of osteochondromas.

Chondrosarcoma arising within a radiation-induced osteochondroma several years following childhood total body irradiation: case report.

Malignant degeneration arising in radiation-induced osteochondromas is extremely rare. We report a case of a 34-year-old man with a chondrosarcoma arising from an osteochondroma of the left posterior eighth rib that developed following total body irradiation received as part of the conditioning regimen prior to bone marrow transplantation at age 8. To our knowledge, this is only the fourth reported case of a chondrosarcoma arising within a radiation-induced osteochondroma and the first case occurring following childhood total body irradiation.

Posttraumatic intramedullary osteochondroma: report of a case.

We present a rare osteochondroma, which instead of being the usual exophytic growth outside bone, grew inward into the medullary cavity of distal femur in a patient with prior trauma to his knee. Except for its intramedullary location, the benign tumor had all the classic radiographic and pathologic features of typical osteochondroma.

Osteochondroma with metaphyseal abnormalities after total body irradiation followed by stem cell transplantation.

The occurrence of osteochondroma after total body irradiation (TBI) followed by stem cell transplantation (SCT) in our institutions was described, and its clinical significance discussed. Of 305 cases treated with SCT using TBI conditioning from 1980 to 2001, 4 cases of osteochondroma were identified on clinical examination. Mean age at the time of TBI was 4.4 years (range, 1.6 to 8.0). One patient developed multiple osteochondromas. All 4 cases showed metaphyseal abnormalities, including sclerotic metaphyseal lesion, fraying, and longitudinal striation, in the area where osteochondromas occurred. Only 1 patient required resection of the tumor due to pain. Two cases had other skeletal abnormalities including slipped capital femoral epiphysis and valgus-knee deformity, which required surgical intervention to prevent or correct these deformities. Osteochondroma is one of the complications developing after TBI, possibly concurrently with the metaphyseal abnormalities as seen on radiographs. However, clinical problems arising from osteochondroma are minimal, and surgical intervention is necessary in limited cases.