Aims. In this study, we aimed to evaluate incidence trends and potential risk factors associated with Perthes’ disease in Denmark, using publicly available data. Methods. Our population-based case-control study used data from the Danish National Patient Register and Danish Civil Registration System, accessed through the publicly available Danish Biobank Register, to identify 1,924,292 infants born between 1985 and 2016. We estimated age-specific incidence rates for four birth periods of equal duration (1985 to 1992, 1993 to 2000, 2001 to 2008, and 2009 to 2016) and investigated associations with perinatal conditions, congenital malformations, coagulation defects, autism spectrum disorders (ASD), and attention deficit hyperactivity disorders (ADHD). Results. We identified 2,374 (81.6% male) diagnosed with Perthes’ disease aged between two and 12 years, corresponding to an overall incidence of 12.1 per 100,000 live births relative to the year of birth. The incidence declined across all four birth periods, irrespective of sex or age at diagnosis. Several perinatal conditions were associated with higher Perthes’ disease risk. Children with reported birth injuries (vs no reported injuries) exhibited the highest risk (relative risk (RR) 7.48 (95% CI 3.37 to 16.63)) followed by those with versus without coagulation defects (RR 4.77 (95% CI 1.79 to 12.69)). Children diagnosed with syndromic (RR 2.90 (95% CI 2.08 to 4.04)) or non-syndromic major congenital malformations (RR 1.86 (95% CI 1.55 to 2.23)) (vs those with no malformation diagnosis) were also associated with higher Perthes’ disease risk. The development of Perthes’ disease was positively associated with several ASD and ADHD diagnoses. However, once adjusting for the sex of the child and period of birth, the associations with ASD and ADHD were no longer significant. Conclusion. Using publicly available data, we observed a declining incidence of Perthes’ disease in Denmark over a 32-year study period. Our findings also confirm positive associations between Perthes’ disease and various perinatal conditions, coagulation defects, and congenital malformations, highlighting potential aetiological pathways for further investigation. Cite this article: Bone Joint J 2025;107-B(2):268–276

Introduction. Neonatal fractures are often quite distressing to parents and medical teams involved. Their management can be daunting due to the small size of the patient, the concern of the new parents and the fear of the obstetric staff about litigation and deformity or long term disability of the neonate. Aim. This study assesses the radiological and functional outcome of neonatal fractures up to two years post injury. Methods. We reviewed the notes of neonates at our hospital who sustained fractures spanning a 4 year period. Clavicle and humeral fractures were treated in a swaddling bandage for 3 weeks. Femoral fractures were treated in a gallows traction for 2–3 weeks. Xrays were taken once weekly. Patients were examined two years following their injury and function of the affected limb was assessed and compared with the unaffected side. Radiographs of the previously fractured bones were also taken at the 2 years follow up. Results. Eighteen (18) neonates sustained fractures predominantly due to birth trauma. There were four clavicle fractures, one fracture of a humerus, three femoral and 10 skull fractures. All seven (7) patients extremity fractures healed satisfactorily clinically and radiologically, with no residual deformity, limb length discrepancy or functional impairment at 2 years follow up. All parents were very satisfied with the outcome. Discussion and Conclusion. Neonatal fractures occur in <1% of births. Causes include birth trauma and congenital bone disease. Neonates with fractures are referred for Orthopaedic management which can be intimidating due to the infrequency of management of this cohort of patients. In our study all of our neonates with long bone fractures had good radiological results and no functional deficit when reviewed after 2 year. Clinicians can be reassured that neonatal fractures have a propensity to heal rapidly without residual functional or radiological abnormality as long as alignment is grossly maintained initially