Our investigation aimed to assess the reliability of the femoral head shape classification system devised by Rutz et al. and observe its application in patients with cerebral palsy (CP) at different skeletal maturity levels. Four independent observers assessed anteroposterior radiographs of the hips of 60 patients with hip dysplasia associated with non-ambulatory CP (Gross Motor Function Classification System levels IV and V) and recorded the femoral head shape radiological grading system as described by Rutz et al. Radiographs were obtained from 20 patients in each of three age groups: under 8 years, between 8 and 12 years and above 12 years old, respectively. Inter-observer reliability was assessed by comparing the measurements of four different observers. To determine the intra-observer reliability, radiographs were reassessed after a 4-week interval. Accuracy was checked by comparing these measurements with the assessment of expert consensus. Validity was checked indirectly by observing the relationship between the Rutz grade and the migration percentage. The Rutz classification system's evaluation of femoral head shape showed moderate to substantial intra-and inter-observer reliability (mean κ = 0.64 for intraobserver and mean κ = 0.5 for interobserver). Specialist assessors had slightly higher intra-observer reliability than trainee assessors. The grade of femoral head shape was significantly associated with increasing migration percentage. Rutz's classification was shown to be reliable. Once the clinical utility of this classification can be established, it has the potential for broad application for prognostication and surgical decision-making and as an essential radiographic variable in studies involving the outcomes of hip displacement in CP. Level of evidence: III.

Introduction Total Hip Arthroplasty is one of the most common orthopaedic procedures. Its outcome is assessed by radiographic evaluation. Two principal radiographic parameters are cup inclination and stem position angle. Aim The study aimed to compare radiological outcomes of two total hip arthroplasty techniques: Alloclassic Zweymüller versus Corail Pinnacle endoprostheses. Material and methods Medical histories of 345 patients who had a hip replacement between 2007 and 2017 were reviewed. Patients with primary total hip arthroplasty with both of mentioned systems were included in the research. Seven observers individually evaluated the radiological images of the 67 endoprostheses (39 Alloclassic Zweymüller and 26 Corail Pinnacle). The cup inclination and the stem position angle were measured using MB-Ruler programme. Results There was no statistical difference (p > 0.338) in cup inclination angle between Alloclassic Zweymüller and Pinnacle cups, with the angle ranging from 31.01° to 58.80° (45.20° on average) and from 30.61° to 59.1° (43.60° on average), respectively. Femoral stem position did not differ between both types of endoprosthesis (p > 0.932), ranging from −1.05° to 7.87° (3.09° on average) for Alloclassic Zweymüller and 0.35° to 7.79° (3.06° on average) for Corail Pinnacle stem. ICC (Intraclass Coefficient Correlation) was estimated and their 95% confident intervals were calculated for cup inclination and stem position showing good reliability of cup inclination measurements. Conclusions Both types of endoprostheses presented similar radiological outcomes. Cup inclination can be used by non-experienced medical staff to reliably assess the postoperative radiograms. Keywords: cementless hip replacement, radiological outcomes, imaging.

Introduction Simple bone cyst is benign fluid-filled lesion localized mainly in long bones. It is usually diagnosed in the first two decades, the most common in proximal humerus. Unicameral bone cyst is o›en asymptomatic but can cause pathological fracture. Aim of the study The aim of our study was to evaluate clinical, diagnostic and treatment factors concerning patients with simple bone cyst. Material and methods The retrospective analysis was performed on 22 patients treated in Department of Traumatology, Orthopaedics and Hand Surgery in Poznań between 2001 and 2017. We have analyzed epidemiological factors: age and sex; symptoms; clinical examination: range of motion, presence of pain; X-ray: localisation, cyst index of Kaelin and MacEwan and presence of pathological fractures; treatment: methods, number of hospitalizations and effectiveness. Results Mean age of patients was 10.8. From 22 patients 11 were females. Generally bone cyst was diagnosed because of pathological fracture – 18 patients (85.7%). Other reasons of X-ray diagnostic were: pain – 2 patients (9.1%), deformity – 1 patient (4.5%), incidentally – 2 patients (9.1%). The bone cyst was localized in humerus – 21 patients (95.5%), radius – 1 patient (4.5%). Treatment methods were various: 7 patients (31.8%) – Depomedrol injections, 4 patients (18.1%) – marrow injections, 4 patients (18.1%) – marrow and Depomedrol injections, 5 patients (22.7%) – injections with additional bone gra›s, 3 patients (13.6%) – only bone gra›s. Conclusions Simple bone cyst occurs generally in young people (under twenty). The most common problem is a pathological fracture. Treatment is long and multistage.

Introduction Simple bone cyst is benign fluid-filled lesion localized mainly in long bones. It is usually diagnosed in the first two decades, the most common in proximal humerus. Unicameral bone cyst is often asymptomatic but can cause pathological fracture. Aim of the study The aim of our study was to evaluate clinical, diagnostic and treatment factors concerning patients with simple bone cyst. Material and methods The retrospective analysis was performed on 22 patients treated in Department of Traumatology, Orthopaedics and Hand Surgery in Poznań between 2001 and 2017. We have analyzed epidemiological factors: age and sex; symptoms; clinical examination: range of motion, presence of pain; X-ray: localisation, cyst index of Kaelin and MacEwan and presence of pathological fractures; treatment: methods, number of hospitalizations and effectiveness. Results Mean age of patients was 10.8. From 22 patients 11 were females. Generally bone cyst was diagnosed because of pathological fracture – 18 patients (85.7%). Other reasons of X-ray diagnostic were: pain – 2 patients (9.1%), deformity – 1 patient (4.5%), incidentally – 2 patients (9.1%). The bone cyst was localized in humerus – 21 patients (95.5%), radius – 1 patient (4.5%). Treatment methods were various: 7 patients (31.8%) – Depomedrol injections, 4 patients (18.1%) – marrow injections, 4 patients (18.1%) – marrow and Depomedrol injections, 5 patients (22.7%) – injections with additional bone grafts, 3 patients (13.6%) – only bone grafts. Conclusions Simple bone cyst occurs generally in young people (under twenty). The most common problem is a pathological fracture. Treatment is long and multistage

Introduction: One of the most significant challenges nowadays is to educate and predict the predispositions of young surgeons taking into consideration that every ability has its own learning curve. Aim: To determine the influence of selected factors and examine the shape and the length of the learning curve in performing simple tasks on an endoscopic simulator. Material and methods: Twenty students took part in 4 training sessions with a one-week break between sessions. They were training 12 minutes and performed three tasks at every session on the endoscopic simulator. To identify whether selected factors influence the time of completing tasks, the participants were asked to fill in questionnaires. All participants also completed the Minnesota Manual Dexterity Test (MMDT) to assess hand-eye coordination. Results: Our research reveals that regardless of activities performed in free time, the shape of the learning curve was logarithmic. Improvement after the fourth session ranged from 50% to 75%. Performing specific activities in the free time did not influence the results achieved on the simulator. No statistically significant correlation between MMDT results and the time to accomplish each task was found. Conclusions: This study has shown that the length of the learning curve of performing simple tasks is quite short and the shape is logarithmic. It suggests that more complex exercises should be included in the training programme.