Full weight bearing was possible at mean 1.7 months (0.5 to 3.0). Mean follow-up period was 6.5 years (sd 5.4; 1.0 to 16.0). No complications developed during the follow-up. Proximal tibia osteotomy fixed with small monolateral external fixator provides accurate, safe and efficient correction in the management of coronal plane angular deformity in small children. Level IV.Level IV. Developmental dysplasia of the hip (DDH) ultrasound screening (USS), which is usually performed in Italy as an outpatient, was halted for an indefinite period in most centres during lockdown. The aim of this study was to analyze the effect of COVID-19 on DDH-USS, in two paediatric orthopaedic centres in one of the most critical areas of the western World. An academic teaching hospital and paediatric trauma centre (T) and a University hospital and DDH referral centre (H), classified as national COVID-19 hubs, were involved. Graf's method was applied in both centres. In T, paediatricians directly referred only patients with delayed DDH-USS or suspicious unstable hips; in H, paediatricians or parents could directly refer to the screening service. The mean age of the 95 patients (190 hips) who were referred for DDH-USS in T, was 3.85 months (0.1 to 7.4); 175 were type I, nine were type IIa (+ and -), five type D and one type IV. In H, the screened patients in 2020 were only 78% of the same period in 2019. A total of 28 patients with 32 hips (8 IIb, 5 IIc, 8 D, 11 III) had late diagnosis at a mean age of 114 days (96 to 146). In the same period in 2019 only eight patients with 11 hips (8 IIb, 1 D, 1 III, 1 IV) at a mean age of 142 days (92 to 305) had late diagnosis. DDH-USS was the only screening in newborns which halted during lockdown. Few centres, which still performed diagnosis and treatment, were overloaded causing a delay in DDH management. IV.IV. Proximal femoral and/or pelvic osteotomies (PFPO) are associated with significant blood loss, which can be harmful, especially in paediatric patients. Therefore, considering methods to reduce blood loss is important. The purpose of this study was to examine the efficacy of tranexamic acid (TXA) in reducing intraoperative estimated blood loss (EBL) in paediatric patients undergoing a PFPO. Paediatric patients who had a PFPO between 2014 and 2019 were retrospectively reviewed. Outcome measures included patient demographics, TXA use (none, preoperative and/or intraoperative bolus, pump), EBL, transfusion rate and thromboembolic complications. Univariate and multivariate analyses were performed to assess associations between investigated outcome measures and EBL. A total of 340 PFPO (263 patients) were included. Mean age at surgery was 8.0 years (sd 4.3). In all, 269 patients received no TXA, 20 had a preoperative bolus, 43 had an intraoperative bolus and eight patients had other TXA regimes (preoperative and intraoperative bolus or pump). Overall, mean blood loss was 211 ml (sd 163). Multivariate analysis showed significant associations between higher EBL and higher age at surgery, male sex, higher body mass index and longer procedure time. There was a significant association between lower EBL and a preoperative TXA bolus 66 ml (33%) less EBL compared with patients without TXA (95% confidence interval -129 to -4; p = 0.04). No thromboembolic complications were reported in any of the studied patients. Preoperative TXA administration is associated with a decreased EBL in PFPO. No thromboembolic events were reported. Administering TXA preoperatively appears to be effective in paediatric patients undergoing a PFPO. Level III - retrospective comparative study.Level III - retrospective comparative study. Avascular necrosis (AVN) may occur following treatment for developmental dysplasia of the hip (DDH). The primary aim of this study was to identify the incidence of AVN in a cohort of patients treated for DDH. Secondary aims were to classify AVN using available classification systems, analyze the correlation between the systems and investigate their relationship with the age at diagnosis of DDH. An 11-year retrospective study was carried out at a single tertiary centre, using data from the clinical portal (patient records database) and IMPAX (system used to store plain radiographic images). Clinical details (patient demographics and outcomes) and plain radiographic images were used to identify cases of DDH and categorize cases of AVN using available classification systems Tonnis and Kuhlmann, Kalamchi and McEwen, Bucholz and Ogden and Salter. Severin was used to assess final clinical outcome. In total, 405 (522 hips) cases of DDH were identified, of which 213 resolved without treatment, 93 were treated conservatively and 99 surgically. Only treated cases were included in the analysis (n = 192). INCB054329 datasheet AVN (45/99; 45.5%) was found to occur only postoperatively. A positive correlation was present between age at presentation and severity of AVN as classified according to Salter's criteria (chi-squared p value < 0.01). AVN incidence was 23.4% (45/192) and only occurred in surgically treated patients. Older age at diagnosis was associated with a higher incidence of AVN, as defined according to Salter's criteria. The classification systems appeared to show no correlation amongst each other (p-value < 0.01). III - Retrospective cohort study.III - Retrospective cohort study. In hip dysplasia the Pemberton osteotomy can modify the shape of the acetabulum and is indicated for children aged between two and 12 when the triradiate cartilage is still open. However, there have been concerns about acetabular retroversion following this type of osteotomy. The studies, however, have been based on plain radiographs. The aim of our investigation was to assess the 3D acetabular orientation in patients with previous Pemberton osteotomy after skeletal maturation. Ten patients with 12 operated hips were included who received Pemberton osteotomy for hip dysplasia between January 3, 2005 and March 25, 2011. Mean age at surgery and at follow-up were 7.2 years (sd 3.7) and 19.2 years (sd 3.7), respectively. MRIs were conducted with 1.5 T. Besides the measurement of acetabular version, the analysis included alpha angles, acetabular sector angles (ASAs) as well as modified ASAs (cartilage covered area angles). Furthermore, the presence of osteoarthritis (OA) as well as acetabular retroversion was determined on plain radiographs.