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Purpose Bipolar hemiarthroplasty has been shown to have a lower rate of dislocation than total hip arthroplasty. However, as the influencing risk factors for bipolar hemiarthroplasty dislocation remain unclear, we aimed to analyse patient and surgeon-specific influencing risk factors for bipolar hemiarthroplasty dislocation. Methods We retrospectively analysed patients who were operated between 2012 and 2018 and had dislocated bipolar hemiarthroplasty and matched them to patients without a dislocated bipolar hemiarthroplasty, operated between 2018 and 2019. The study was limited to patients who received either a pre- or postoperative pelvic computed tomography. Besides demographic, morphologic, and physiologic data, we analysed duration of surgery; ASA score; Charlson Comorbidity Index; Almelo Hip Fracture Score; Parker Score; and acetabular morphology angles including acetabular anteversion angle, posterior acetabular sector angle, posterior wall angle, and acetabular roofing. Results We included nine patients with a dislocated bipolar hemiarthroplasty and 30 with a non-dislocated bipolar hemiarthroplasty. Patient-specific factors prompting a higher risk for dislocated bipolar hemiarthroplasty were longer duration of surgery (min) (115 ± 50 vs. 80 ± 27, p = 0.01); dementia (56% vs. 13%, p < 0.01); smaller posterior acetabular sector angle (°) (96 ± 6 vs. 109 ± 10, p < 0.01); and smaller posterior wall angle (°) (67 ± 6 vs. 77 ± 10, p = 0.02). Conclusion Dementia and insufficient posterior wall angle were associated with higher risk of dislocation in bipolar hemiarthroplasty

Background In elderly patients, displaced femoral neck fractures are mostly treated by arthroplasty; however for younger patients (<50 years), open reduction and internal fixation is considered the gold standard approach. Despite there being no consensus on the specific procedure, everyday clinical practice in a level I trauma center has shown that postoperative maltorsion after internal fixation of femoral neck fractures can have a significantly worse impact on mobilization and outcome. Different methods for measurement of malrotations are reported in literature. However, any reported method for the assessment of a shaft malrotation in the femur does not work here. In femoral neck fractures, the pointer function of the femoral neck, which is absolutely essential for these techniques, is lost and cannot be set in relation to the condylar plane. These circumstances are not addressed in literature thus far. Therefore, we propose here a novel method to fill this diagnostic gap. Methods and findings Three investigators (1 orthopaedic surgeons and 2 radiologists) measured the torsion of 20 legs on 10 patients using the Jarret method and a new geometric technique. To determine the intraobserver reliability the torsional angles were calculated again after 3 months. We applied a new geometric technique, without the need to include the femoral condyles in the measurement, to directly measure the angulation. For torsional difference, the interrater reliability -ICC (interclass correlation) between all investigators was 0.887 (good) (significance level: 95%CI, 0.668–0.969; p<0.001), by using the method of Jarret et al. and 0.933 (good) for the novel technique (significance level: 95%CI, 0.802–0.982; p<0.001). If the examinations are classified according to the patient side, our data show that for established methods, an ICC between the examiners on the right lower extremity is 0.978 (good) (95%CI, 0.936–0.994; p<0.001) and that on the left extremity is 0.955 (good) (95%CI, 0.867–0.988; p<0.001). Comparing with the new method, the right side assumes an ICC of 0.971 (good) (95%CI, 0.914–0.992; p<0.001), while the left side assumes an ICC of 0.910 (good) (95%CI, 0,736–0.976; p<0.001). When it comes to the intraobserver reliability, the measured cohort shows a significant better ICC for the novel method compared to Jarrett et al, with 0.907 respectively 0.786 for comparison in torsional differences. Conclusion The established methods may fail in assessing this special aspect of malrotation after femoral neck fractures. Here, the method presented results in a significant difference between the injured and uninjured side and shows significant differences in results compared to conventional measurement methods. The inter- and intraobserver reliability determined in this study is excellent and even higher in the assessment of torsional differences than the established method. We believe that the measurement method presented in this study is a useful tool to objectify the postoperative deformities in this area and making therapy recommendations in the future.

Background/Aim: Patella baja (PB) and pseudopatella baja (PPB) have been shown to negatively influence outcomes after total knee arthroplasty. We hypothesized that there is a high incidence of PB and PPB after megaprosthetic total knee arthroplasty (M-TKA), and that this is associated with reduced range of motion. Patients and Methods: We retrospectively analysed all patients in our Orthopaedic Trauma Department after distal femur or proximal tibia replacement. Preoperative and one-year postoperative followup included measurement of range of motion and detection of PB and PPB using radiological indices. Results: We included 44 patients (age: 73±19 years). Preoperative PB detected by ISI could be reduced from 13 (36%) to 11 (25%) (p<0.01). Preoperative vs. postoperative ISI was 0.88±0.23 vs. 1.06±0.45 (p=0.03). PPB was observed preoperatively in 23 (63%) patients vs. 24 (54%) postoperatively. Preoperative vs. postoperative CDI was 0.70±0.24 vs. 0.95±0.43 (p=0.002). Preoperative flexion was 91˚±30˚ vs. 85˚±24˚ postoperatively (p>0.05). Conclusion: Both PB and PPB are frequently observed after M-TKA. A reduction in PB and PPB alone does not improve postoperative range of motion.

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