Gnathodiaphyseal dysplasia: Diagnostic clues from two fetal cases and literature review.

This article presents two fetal cases of gnathodiaphyseal dysplasia (GDD), a rare autosomal dominant disorder, and reviews the relevant literature. The cases involved two fetuses exhibiting bone bowing, which led to the diagnosis of GDD. Genetic testing revealed two de novo variants of the ANO5 gene, confirming the diagnosis. A literature review was conducted to explore GDD's clinical and paraclinical presentation, diagnosis, and management. GDD is a rare but frequently inherited cause of bone fragility and jaw lesions characterized by a gain-of-function variant within the ANO5 gene. Clinical manifestations range from recurrent dental infections with mild jaw lesions to severe bone fragility with several fractures associated with large jaw lesions requiring disfiguring surgeries. Diagnostic techniques depend on the context and include targeted genetic testing of ANO5, untargeted molecular analysis with whole-exome sequencing, or whole-genome sequencing. This case report highlights the importance of recognizing GDD as a novel cause of bone bowing and fractures during pregnancy. By summarizing the literature, this article contributes to healthcare professionals' knowledge and improves the recognition, diagnosis, and care of patients with GDD.

Imaging characteristics of too-long anterior process syndrome in children and adolescents.

BACKGROUND: In the presence of pain over the lateral aspect of the foot or recurrent ankle sprain in children, medical imaging is often employed to investigate potential causes, such as a calcaneonavicular coalition or a too-long anterior process (TLAP) of the calcaneus. Diagnosis and categorization of calcaneonavicular coalitions (synostosis, synchondrosis, or synfibrosis) is generally facilitated through imaging, in contrast to TLAP, which lacks well-defined semiological characteristics, apart from a calcaneonavicular space measurement of less than 5 mm. However, this measurement initially performed on an oblique view radiograph can be subject to a lack of precision due to positional variations of the foot and overlapping bones. Furthermore, the differentiation between TLAP as an anatomical variant and TLAP syndrome (characterized by symptomatic presentation), remains a subject of uncertainty. OBJECTIVE: The objective of our retrospective study was to investigate the imaging diagnosis of TLAP syndrome. MATERIALS AND METHODS: A retrospective unmatched case-control study was conducted, covering data from February 2014 to January 2021. All patients, included retrospectively and consecutively, were initially managed in our hospital with radiography and/or computed tomography (CT) and/or magnetic resonance imaging (MRI). Two radiologists independently reviewed the images taken (radiographs, CT scans, and MRIs) of patients undergoing treatment in pediatric orthopedics for TLAP syndrome and control subjects, utilizing a standardized questionnaire. The control group consisted of subjects with no features suggestive of TLAP syndrome. The questionnaire included measurements of the calcaneonavicular space and identification of indirect signs associated with calcaneonavicular coalitions, as described in the related literature. RESULTS: A total of 128 patients who met the inclusion criteria were included in the analysis, including 38 patients and 90 controls. The prevalence of TLAP was 71.5% in the study population and 62.6% among controls. A threshold measurement of the calcaneonavicular space at 3.2 mm favored TLAP syndrome (sensitivity=97%, specificity=70%, area under the curve [95% confidence interval] =0.881[0.812-0.949]), with better precision using CT. Three indirect signs were significant: the "anteater nose" sign, the talar beak, and the tapered anterior calcaneal process. These signs demonstrated an even stronger association with TLAP syndrome when observed in conjunction with a reduction in the calcaneonavicular space, particularly in CT scans. CONCLUSION: TLAP is common among control subjects. Therefore, a variant appears to be the most plausible explanation and it can be considered a mild form of calcaneonavicular coalition. However, in conjunction with symptoms suggestive of TLAP syndrome, the diagnosis is further supported by imaging, specifically with a calcaneonavicular space measurement of less than 3.2 mm. This measurement is most accurately obtained using CT with 2-dimensional reconstructions in all three planes. The simultaneous presence of the "anteater nose" sign, the talar beak, or the tapered anterior calcaneal process provides additional diagnostic evidence. In the diagnostic approach of calcaneonavicular coalition, oblique foot radiography seems useful in initially detecting abnormal coalition (bony or not), and complementarily, CT emerges as the best modality to characterize TLAP syndrome.

Metaphyseal and Diaphyseal Contours: Variants and Pitfalls.

We discuss several variants of the metaphyseal and diaphyseal bone surfaces that may be misleading in clinical practice. They include metaphyseal stripes, spiculated metaphyseal cortex, cortical desmoid, laminated lateral supracondylar ridge, cortical vascular canals, variations in shape or lucency of normal tuberosities, cortical thickening of normal ridges, and well-organized undulated hyperostosis at the proximal phalanges.

The monthly incidence of abusive head trauma, inflicted skeletal trauma, and unexplained skin lesion in children in six French university hospitals during the COVID-19 pandemic.

INTRODUCTION: The COVID-19 pandemic was a stressful period. Lockdowns may have added to parental difficulty leading to an increase in violence. This study aimed to compare the monthly incidence of high suspicion of child physical abuse before and during the COVID-19 pandemic. MATERIAL: We have retrospectively reviewed imaging examinations of children having a skeletal X-ray examination in six university hospitals with high suspicion of abusive head traumatism (AHT), inflicted skeletal trauma (IST) and unexplained skin lesions (USL) between March 2020 and June 2021 and compared with the similar period from 2018 to 2019. The monthly incidence of the different physical maltreatment was analyzed using a QuasiPoisson regression model. RESULTS: We included 178 children (n = 127 boys, 71.3 %), 110 during the pandemic period, median age 5 months. AHT was diagnosed in 91 children, 55 had inflicted skeletal trauma (IST) and 46 had unexplained skin lesions (USL). Among the 91 patients with AHT, 86 had a subdural hematoma (95.6 %) and 40 had bridging veins thrombosis (44 %). The ophthalmological examination performed on 89 children (97.9 %) revealed retinal hemorrhages in 57 children (89.8 %). The incidence of AHT doubled during the months of COVID-19 lockdowns (rate ratio = 2; 95 % CI [1.1; 3.6], p = 0.03). No difference in monthly incidence was observed for IST and USL groups. CONCLUSION: A significant increase in AHT was observed during the months with lockdowns and curfews during the COVID-19 pandemic. This highlights the need for developing a national strategy to prevent physical abuse in children in this context.

Anatomical characterization of the too-long anterior process of the calcaneum: a computed tomography scan analysis of 69 feet.

Our work aims to identify and measure the morpho-anatomical characteristics of too-long anterior calcaneal process based on computed tomography scans done in patients with a history of pain and who have experienced repeated ankle sprains. The computed tomography scans of 69 feet were reviewed. These scans were used to calculate (1) the calcaneo-navicular distance; (2) the height, length, and width of the too-long anterior calcaneal process; (3) the length of the calcaneum; (4) the angle of the too-long anterior calcaneal process in the sagittal (anterior-superior angle), axial (anterior-medial angle), and frontal plane. Out of 69 feet, forty-nine were pathological (71%) with abnormalities of the too-long anterior calcaneal process, while the rest (29%) had no morphological abnormalities. The calcaneo-navicular distance was found to be <5 mm (mean: 2.8 ± 1.2 mm) in all pathological feet, which also had significantly reduced calcaneo-navicular distance ( P < 0.001) and longer bone portion distal to the calcaneocuboid tangent ( P < 0.001) in comparison to normal feet. In pathological feet, the mean too-long anterior calcaneal process length was 10.7 ± 1.9 mm; the mean anterior-superior angle was 29.6 ° ± 11.6, the mean angle anterior-medial angle was 40.7 ° ± 8.3, the mean angle frontal plane was 74.2 ° ± 14.1. Similar to a cone or a parallelepiped, the too-long anterior calcaneal process has a complex three-dimensional anatomy, with a superior, medial, and anterior direction. Using the measurements obtained, four different too-long anterior calcaneal process morphotypes could be identified: absence of TLACP, triangular shape, rectangular shape, and coalition (level of evidence III).

Interrelations Between the Too-Long Anterior Calcaneal Process, Hind and Mid-tarsal Bone Volumes, Angles and Osteochondral Lesion of the Dome of the Talus: Analysis by Software Slicer of 69 CT Scan of Feet.

Introduction: Although the association between Too-Long Anterior Calcaneal Process (TLACP) and osteochondral lesion of the dome of the talus (OCL) has been hypothesized, no study has investigated the interrelations between TLACP, hind and mid-tarsal volumes and angles and the development of OCL. The main goals of this work are: (1) to measure the volume of the calcaneum, talus, navicular and cuboid in subjects with and without TLACP; (2) to evaluate the angular relationships between talus, calcaneum and navicular in subjects with and without TLACP; (3) to assess whether TLACP has an effect on the volume of OCL. Methods: This is a retrospective study of 69 CT scans of 54 consecutive children aged 11-15 years who had undergone a CT scan due to symptomatology suggestive of TLACP. The 3D Slicer software allowed to calculate the volume of the talus, calcaneum, navicular, cuboid, TLACP and OCL (in cm3). The PACS system was used to perform the angular measurements (in degrees) between talus, calcaneum and navicular in the frontal, axial and sagittal plane. Results: Amid the 69 CT scans, 49 were found to have pathologies related to TLACP (71%, TLACP Group) and 20/69 were normal (29%, Control Group). The mean hind and mid-tarsal bone volumes of the TLACP group were comparable to those of the control group. There were 40 (81.6%) OCLs detected exclusively in pathological feet (TLACP group); 32 lesions were medial (80%), and 8 lesions were lateral (20%). According to Ferkel and Sgaglione CT Staging System, there were 22 (55%) stage 1 lesions, 5 (12.5%) stage 2A, 3 (7.5%) stage 2B and 10 (25%) stage three lesions. Only the angle between the talus and calcaneum in the frontal plane was significantly lower in pathological feet with respect to the control group (p < 0.001). In pathological feet, the talus was supinated, and the calcaneus pronated. Conclusions: TLACP tend to stiffen the foot, modifying its biomechanics and leading to supination of the talus and pronation of the calcaneum. This induces an overpressure at the medial side of the talus where we observed a greater frequency of medial OCL with larger volume than lateral OCL. Level of Evidence: III.

The too-long anterior process and osteochondral lesion of the talus: Is there an anatomical predisposition? A case-control study on 135 feet.

INTRODUCTION: The too-long anterior process (TLAP) increases mechanical stress on the hindfoot and could lead to osteochondral lesions of the talus (OLT) by localized hyper-pressure. The purpose of this study is to investigate an association between TLAP and OLT in children. METHODS: This is a retrospective, multicenter, case-control study conducted between 2010 and 2020. The OLT group was compared to a control group (CoG). TLAP is characterized by a distance between the anteromedial process of the calcaneus and the navicular bone (CN) of< 5 mm. RESULTS: Forty-three feets were included in the OLT group and 92 in the CoG. The OLT group had a lower CN distance on CT than the CoG, a median of 2.8 mm versus 3.75 mm (p = 0.002); 86% of patients (37 feet/43) in the OLT group had a CN distance of< 5 mm (OR=3.0 [1.1; 9.5], p = 0.023) compared to 67% in the CoG. DISCUSSION: The OLT group had an increased risk of developing TLAP compared to the CoG. LEVEL OF EVIDENCE: III.

Treatment of two infants with PIK3CA-related overgrowth spectrum by alpelisib.

PIK3CA-related overgrowth spectrum (PROS) includes rare genetic conditions due to gain-of-function mutations in the PIK3CA gene. There is no approved medical therapy for patients with PROS, and alpelisib, an approved PIK3CA inhibitor in oncology, showed promising results in preclinical models and in patients. Here, we report for the first time the outcome of two infants with PROS having life-threatening conditions treated with alpelisib (25 mg) and monitored with pharmacokinetics. Patient 1 was an 8-mo-old girl with voluminous vascular malformation. Patient 2 was a 9-mo-old boy presenting with asymmetrical body overgrowth and right hemimegalencephaly with West syndrome. After 12 mo of follow-up, alpelisib treatment was associated with improvement in signs and symptoms, morphological lesions and vascular anomalies in the two patients. No adverse events were reported during the study. In this case series, pharmacological inhibition of PIK3CA with low-dose alpelisib was feasible and associated with clinical improvements, including a smaller size of associated complex tissue malformations and good tolerability.

Congenital and Developmental Abnormalities of the Hand and Wrist.

Identification of congenital skeletal abnormalities is complex because of the large variety of individual syndromes and dysplasias that are often difficult to remember. Although a correct diagnosis relies on a combination of clinical, radiologic, and genetic tests, imaging plays an important role in selecting those patients who should be referred for further genetic counseling and expensive genetic tests. In addition to information derived from radiologic analysis of other skeletal elements, radiographs of the hand and wrist may provide particular useful information. In the first part of this article, we provide a guide for a systematic radiologic analysis of the hand and wrist bones that may help characterize congenital and developmental diseases. Special attention is given to the use of correct terminology. In the second part, we discuss typical examples of congenital and developmental diseases involving the hand and wrist, with an emphasis on skeletal dysplasias.

Chest computed tomography findings for a cohort of children with pulmonary Langerhans cell histiocytosis.

OBJECTIVE: This study was undertaken to describe the spectrum of lung computed-tomography (CT) findings in children with pulmonary Langerhans cell histiocytosis (PLCH) and to evaluate for this population the CT-scan nodule and cyst scores proposed by adult pulmonologists at diagnosis and during follow-up. METHODS: Among 175 children with PLCH identified in the French national population-based Langerhans cell histiocytosis cohort, 60 were retrospectively selected by the availability of CT for a central review by three pediatric radiologists. These 60 patients are representative of childhood PLCH for almost all clinical aspects, except a lower percentage of risk organ involvement (38% vs 54%; P = 0.05). RESULTS: The 60 children's chest CT scans (n = 218) were reviewed. At diagnosis, 63% of them had nodules, 53% had cysts, and 29% had both. The percentages of patients with nodules or cysts increased from diagnosis to peak disease activity, respectively, from 63% to 73% and from 53% to 66%. The costophrenic angle was involved in 71%. Patients with pneumothorax (25%) had a higher median cyst score. Alveolar consolidation was observed in 34%. Patients with low CT-scan nodule and cyst scores had no long-term pulmonary sequelae. CONCLUSIONS: Well-known characteristics of adult PLCH (nodules and cysts) were observed in children. The chest CT scores proposed by adult pulmonologists could easily be applied to childhood PLCH. Lesions in children, unlike those in adults, are frequently located near the costophrenic angles. Alveolar consolidation might be considered an atypical feature of childhood PLCH.

Radiographic/MR Imaging Correlation of the Pediatric Knee Growth.

Normal bone growth of the pediatric knee as well as normal variants of ossification result in different appearances that can be identified on imaging (radiography/MR imaging). Familiarity with these changes is important to avoid confusing normal growth with pathology. This article illustrates the main features related to normal bone growth (growth arrest lines, physeal changes, ossification centers within the epiphysis, hematopoietic marrow within the metaphysis) and physis disappearance (« FOPE ¼). Variants in femur (epiphyseal irregularities, subchondral anomalies of posterior condyles, periosteal desmoid), tibia (tibial tuberosity ossification), and patella (dorsal defect, bipartite patella, lower pole fragmentation) are also described.

Imaging Features of the Juvenile Inflammatory Arthropathies.

We discuss the imaging of several juvenile inflammatory arthropathies including juvenile idiopathic arthritis, juvenile systemic lupus erythematosus, juvenile scleroderma, juvenile dermatomyositis, and chronic recurrent multifocal osteomyelitis. Juvenile idiopathic arthritis is the most common autoimmune chronic systemic disease of connective tissue in children. The remaining systemic juvenile connective tissue diseases are rare. However, they require early diagnosis and initiation of treatment to prevent injury, not only to the musculoskeletal system but also to the internal organs, and even death. Imaging of juvenile inflammatory arthropathies has relied for years on radiography. Recent advances in disease-modifying drugs have led to a greater emphasis on the detection of early inflammation not evident on plain radiography. Ultrasound examination allows for the early recognition of the disease process in the soft tissues. Magnetic resonance imaging detects early inflammatory changes involving the soft tissues, the subcortical bone of peripheral joints, the spine, and entheses.

Assessment of micro-dose biplanar radiography in lower limb measurements in children.

OBJECTIVES: To evaluate in children microdose protocol compared with low dose for lower limb alignment (LLA) measurements on biplanar radiography. METHODS: Children 6 years or older were included. Height, weight and hip width were measured prior to imaging. Hip width allowed classifying children into morphotype M1 (width <25 cm), M2 (25-35 cm) or M3 (>35 cm) corresponding to predefined acquisition parameters (kV, mA, tube speed). Micro- and low-dose protocols were used alternately, with simultaneous acquisition of frontal and lateral radiographs. LLA measurements were performed by two independent observers (n = 526). In 15 children per morphotype, a third observer performed measurements twice (n = 180). Intraclass correlation coefficients and the dose (delivered, absorbed) were calculated. RESULTS: 100 girls and 160 boys (mean age = 11.7 years) were investigated: 74 M1 (mean BMI, 15.7kg/m2), 149 M2 (19.8 kg/m2) and 40 M3 (30.2 kg/m2). With microdose, inter- and intra-observer agreement was >0.90 for lengths whatever the morphotype, 0.75-0.90 (M1) and >0.90 (M2, M3) for valgus/varus and flexion/hyperextension deviations. Dose reduction reached a factor of 8.5 and 5.4 for the delivered and absorbed dose respectively. CONCLUSIONS: Microdose could be used for LLA measurements in children and permits a significant dose reduction. KEY POINTS: • Lower limb lengths of children can be evaluated with microdose biplanar radiography. • Valgus/varus deviations also can be evaluated with microdose biplanar radiography. • Microdose biplanar radiography significantly reduces delivered and absorbed dose in children.

Traumatic avulsion of the superior extensor retinaculum of the ankle as a cause of subperiosteal haematoma of the distal fibula in children. A retrospective study of 7 cases.

OBJECTIVE: To describe a new sonographic feature for a traumatic lesion of the ankle in children. MATERIALS AND METHODS: We present a retrospective review of superior extensor retinaculum (SER) avulsions diagnosed by ultrasound (US) as a cause of subperiosteal haematoma (SPH) and periosteal apposition of the distal fibula in seven children (3 girls and 4 boys, mean age 13.4 years; age range 10-15 years) after an inversion trauma of the ankle. Two children were subsequently examined with magnetic resonance imaging (MRI). RESULTS: At the acute phases (6 children), US showed a hypoechoic collection with periosteal elevation at the fibular insertion of the SER. The fibular cortex and growth plate were unremarkable. The SPH was isolated in three cases and associated with an anterior talofibular ligament sprain in four. In two cases, MRI confirmed the SER periosteal avulsion and the integrity of the distal fibula. At the later phase (one child), US showed a periosteal apposition at the fibular insertion of the SER with hypoechoic thickening of the SER and power Doppler hyperaemia. CONCLUSION: This is the first sonographic description of SER avulsion as cause of SPH of the distal fibula in children. SPH in children should not be considered as pathognomonic of a Salter-Harris type 1 lesion of the distal fibula. Later, it may be responsible for persistent ankle pain. Therefore, SER may be systematically explored in children during US examination of the ankle after trauma.

Prospective evaluation of free-breathing diffusion-weighted imaging for the detection of inflammatory bowel disease with MR enterography in childhood population.

OBJECTIVE: To evaluate prospectively the performance of diffusion-weighted imaging (DWI) for the detection of active lesions on MR enterography (MRE) in children with inflammatory bowel disease (IBD). METHODS: MRE of 48 children (mean age 13 years) with suspected or known IBD were blindly analysed by 2 independent readers for the presence of active lesions. Two sets of imaging including DWI and gadolinium-enhanced imaging (GEI) were reviewed. A reader consensus was obtained. The gold standard was histopathological findings. In patient-level analysis and segment-level analysis, sensitivity and specificity were calculated for DWI and GEI and compared using McNemar's test or logistic random-effects models. RESULTS: At least 1 active lesion was confirmed in 42 (87.5%) children. Sensitivity and specificity for the detection of at least one lesion were 88.1% (95% CI, 74.3-96.1) and 83.3% (95% CI, 35.9-99.6), respectively, for DWI and 66.7% (95% CI, 50.4-80.4) and 83.3% (95% CI, 35.9-99.6), respectively, for GEI. In segment-level analysis, sensitivity and specificity for the detection of specific segment lesions were 62.5% (95% CI, 48.1-75) and 97.1% (95% CI, 93.5-98.7), respectively, for DWI and 45.7% (95% CI, 30.8-61.3) and 98.2% (95% CI, 95.3-99.4), respectively, for GEI. The sensitivity of DWI was significantly better than that of GEI per patient (p = 0.004) and per segment (p = 0.028). CONCLUSION: DWI demonstrates better performance than GEI for the detection of active lesions in children with IBD. ADVANCES IN KNOWLEDGE: Examination with no intravenous injection-DWI can replace T1 weighted images when paediatric patients are screened with MRE for IBD. Examination performed in free breathing is better tolerated by children.

Renal involvement in tuberous sclerosis complex with emphasis on cystic lesions.

INTRODUCTION: Tuberous sclerosis complex (TSC) involves frequently the kidneys. Lesions encompass mainly angiomyolipoma and cysts. The disease can be associated with autosomal dominant polycystic kidney disease leading to the contiguous gene syndrome (CGS) The objectives of the present study were to review the US appearances of the renal involvement in children affected by classical TSC or by the CGS and to verify whether it is possible to differentiate between both entities. The evolution of the lesions through time was also studied. MATERIALS AND METHODS: 55 cases of patients <16 years with STB were reviewed by two pediatric radiologists. Clinical data reviewed included age at diagnosis, genetic assessment and complications; US data reviewed included renal size, type of lesions (angiomyolipoma-AML, or cysts), number and location as well as their evolution with time. Complications were also analyzed. RESULTS: 30 patients (56 %) had at least one kidney lesion (27 classical TSC and 3 CGS). On the basis of the US findings, these patients were separated into four groups. Group 1 (9 patients) displayed microscopic (diffuse) AML; group 2 (3 patients) displayed macroscopic AML; group 3 (9 patients) displayed only renal cysts and group 4 (9 patients) displayed the association of AML and cysts. Increased renal size, the large number and size of cystic lesions were suggestive of the CGS. The isolated AML were suggestive of classical STB. The average growth of angiomyolipoma was low before age of 12 and exceeded 4 mm/year thereafter. CONCLUSION: In children with TSC, renal involvement is common. Some US criteria can help to suggest the diagnosis of CGS. The growth of angiomyolipoma is slow before 12 years and accelerates thereafter. Complications are rare.

Recommendations of the ESSR Arthritis Subcommittee for the Use of Magnetic Resonance Imaging in Musculoskeletal Rheumatic Diseases.

This article presents the recommendations of the European Society of Musculoskeletal Radiology Arthritis Subcommittee regarding the standards of the use of MRI in the diagnosis of musculoskeletal rheumatic diseases. The recommendations discuss (1) the role of MRI in current classification criteria of musculoskeletal rheumatic diseases (including early diagnosis of inflammation, disease follow-up, and identification of disease complications); (2) the impact of MRI on the diagnosis of axial and peripheral spondyloarthritis, rheumatoid arthritis, and juvenile spondyloarthritis; (3) MRI protocols for the axial and peripheral joints; (4) MRI interpretation and reporting for axial and peripheral joints; and finally, (5) methods for assessing MR images including quantitative, semiquantitative, and dynamic contrast-enhanced MRI studies.

Association between Kniest dysplasia and chondrosarcoma in a child.

Constitutive COL2A1 mutations are associated with a wide variety of clinical manifestations known as type II collagenopathies. Among them is Kniest dysplasia, which is phenotypically variable and includes both skeletal (short trunk and limbs, kyphoscoliosis, prominent joints, and osteoarthritis) and craniofacial characteristics. Kniest dysplasia mutations primarily arise in the triple-helicoidal region of the alpha 1 (II) chain in COL2A1 between exons 12 and 24. Somatic COL2A1 mutations have been identified in chondrosarcoma, a rare cartilage forming neoplasm, with a hypermutability of the gene reported in 37% of cases. However, to the best of our knowledge, there is no reported increase in predisposition to chondrosarcoma in human collagenopathies, and no reported clinical association between these congenital diseases and cartilaginous tumors. In the case study presented here, we report the first description of an association between these two rare diseases involving COL2A1, in a child presenting with Kniest dysplasia and a grade I sphenoethmoidal chondrosarcoma. We also describe a new constitutive mutation in COL2A1.

Community-acquired bone and joint infections in children: a 1-year prospective epidemiological study.

BACKGROUND: The incidence of childhood bone and joint infections (BJIs) is not well known, but is useful for identifying epidemiological differences and improving practice. OBJECTIVE: To determine the incidence of BJI in previously well children and describe their clinical, laboratory and radiological characteristics. DESIGN: A multicentre, population-based, prospective study performed from July 2008 through June 2009. SETTING: Region of northern France with a population of 872 516 children <16 years old. PATIENTS: All previously well children admitted in the region with septic arthritis, acute osteomyelitis or spondylodiscitis, diagnosed according to consensus criteria and after blinded radiological review. MAIN OUTCOME MEASURES: The corrected incidence of BJI, determined with a capture-recapture method that used this prospective database and the discharge summary database. RESULTS: 58 cases were identified (median age: 3.6 years, range: 1 month-15.8 years; male to female ratio: 1.6). The completeness of the prospective database was 90%. The corrected incidence of any BJI was 7.1/100 000 children (95% CI 5.3 to 8.9). Thirty patients had septic arthritis (52%, incidence: 3.7/100 000; 95% CI 2.4 to 4.9), 24 osteomyelitis (41%, incidence 3.0/100 000; 95% CI 1.8 to 4.1), 4 spondylodiscitis (7%) and 0 osteoarthritis. Micro-organisms were identified from 15 patients (26%), with Staphylococcus aureus the most frequent organism. Radiological findings were characteristic of infection in 44% of BJI. CONCLUSIONS: The corrected incidence of BJI in northern France, according to consensus diagnostic criteria, was 7.1/100 000 children <16 years of age.