High cycle fatigue and ratcheting interaction of laser powder bed fusion stainless steel 316L:Fracture behaviour and stress-based modelling

Variations in the physical and mechanical properties of parts made by laser power bed fusion (L-PBF) could be affected by the choice of processing or post-processing strategies. This work examined the influence of build orientation and post-processing treatments (annealing or hot isostatic pressing) on the fatigue and fracture behaviours of L-PBF stainless steel 316L in the high cycle fatigue region, i.e. 104 – 106 cycles. Experimental results show that both factors introduce significant changes in the plastic deformation properties, which affect fatigue strength via the mechanism of fatigue-ratcheting interaction. Cyclic plasticity is characterised by hardening, which promotes mean stress insensitivity and improved fatigue resistance. Fatigue activities, involving the initiation of crack at defects and microstructural heterogeneities, are of greater relevance to the longer life region where the global deformation mode is elastic. As the simultaneous actions of ratcheting and fatigue generate complex nonlinear interactions between the alternating stress amplitude and mean stress, the fatigue properties could not be effectively predicted using traditional stress-based models. A modification to the Goodman relation was proposed to account for the added effects of cyclic plasticity and was demonstrated to produce good agreement with experimental results for both cyclic hardening and softening materials.EDB (Economic Devt. Board, S’pore)Accepted versio

Bilateral Congenital Dislocation of the Knee with Ipsilateral Developmental Dysplasia of the Hip – Report of Three Patients

Congenital dislocation of the knee (CDK) is a very rare condition. Here we report our strategy and results in treatment of three children with CDK. All three patients were treated with conservative method, and only one had underwent a surgical procedure on one knee. Of the remaining, we recorded a good outcome with conservative treatment in three knees, while two had poorer outcome as a result of musculoskeletal anomalies. We also present here a unique case of a child born without cruciate ligaments and patellas on both sides. We performed the operative procedure by Z-plasty of the extensor apparatus on one left knee according to Niebauer and King on one child. The clinical result of this procedure was very good. Five years after the operation we decided to perform an MRI examination to assess the postoperative status of the operated knee, especially the position and the shape of left patella. We found the asymmetry and high position of the operated patella resulting in patella alta. Compared to the initial clinical presentation, we consider all patients to have good clinical presentation nowdays

Two-Directional Arthrographic Assessment for Treating Bilateral Development Dislocation of the Hips in Children after Walking Age

We reviewed the treatment outcome in 14 hips of 7 patients who were diagnosed as having bilateral developmental dislocation of the hip (DDH) after walking age and could be followed up until they were at least 14 years of age. Based on the results of two-directional arthrography of the hip, closed reduction was performed in 2 hips, and open reduction was performed without osteotomy in 12 hips. The final radiographic evaluations were made according to the Kalamchi and MacEwen classification and Severin classification. The mean age at the initial visit was 1 year and 9 months (range, 1 year and 5 months to 3 years). The outcome was satisfactory for one hip in Group Ⅰ and 2 hips in Group Ⅱ according to the Kalamchi and MacEwen classification, and in 83% of the Severin Class Ⅰ and Ⅱ hips. Arthrography was useful for identifying asymmetry, demonstrating the usefulness of a treatment strategy based on arthrography of the hip

The Pavlik Harness in the Treatment of Congenital Dislocating Hip: Report on a Multicenter Study of the European Paediatric Orthopaedic Society

The results of functional treatment using the Pavlik harness in congenital dislocation and congenital dysplasia of the hip in children aged less than 11 months were examined by an EPOS study group. This study was conducted on 3,611 hips in 2,636 patients for a period of 1-9 years after treatment. The reduction rate was 92% in grade Tonnis 2 and 3; the healing rate was 80%. In children with dysplastic hips, the healing rate was 95.35%. Avascular necrosis of the femoral head was observed in 2.38%. The Pavlik harness is designed for outpatient treatment if the parents are complian

Total hip arthroplasty surgical approach does not alter postoperative gait mechanics one year after surgery

Objective: To investigate the differences in gait biomechanics on the basis of surgical approach 1 year after surgery. Design: This was a descriptive laboratory study to investigate the side-to-side differences in walking mechanics at a self-selected walking speed as well as a functional assessment 1year after total hip arthroplasty (THA). Temporospatial, kinetic, and kinematic data as well as functional outcomes were collected. Two-way analysis of variance was used to assess for between-group differences and limb-to-limb asymmetries. Setting: A controlled laboratory study. Participants: This study examined 35 patients with primary, unilateral THA. The THA surgical approaches that were used in these patients included 12 direct lateral, 18 posterior, and 11 anterolateral. All the patients were assessed 1 year after THA. Patients were excluded from the study if they had contralateral hip pain or pathology, or any prior lower extremity total joint replacements. Main Outcome Measurements: Three-dimensional lower extremity kinematics and kinetics as well as spatiotemporal variables were collected. In addition, a series of physical performance measures were collected. Results: No main effects for the physical performance measures or biomechanical variables were observed among the approach groups. Significant limb-to-limb asymmetries were observed among all the patients, with decreased sagittal plane range of motion, peak extension, and peak vertical ground reaction forces on the operative side. Conclusion: The results of this study indicated that no significant differences existed among the different surgical approach groups for any study variable. However, 1 year after THA, the patients demonstrated asymmetric gait patterns regardless of surgical approach, which indicated the potential need for continued intervention through physical therapy to regain normal side-to-side symmetry after THA. © 2014 American Academy of Physical Medicine and Rehabilitation

Retrieval evidence of impingement at the third articulation in contemporary dual mobility cups for total hip arthroplasty

PURPOSE: We aimed to assess polyethylene liners of retrieved hips of one design of a dual mobility (DM) cup liner and two designs of femoral stems to better understand the role of femoral stem design on polyethylene impingement. METHODS: This was a case-control study involving 70 retrieved highly cross-linked polyethylene (X3) liners used with ABGII (n = 35) and Rejuvenate (n = 35) stems (Stryker). All polyethylene liners were assessed for evidence of rim deformation and the damage quantified using metrology methods. RESULTS: A total of 80% of polyethylene liners paired with ABGII necks had macroscopic evidence of neck impingement resulting in a raised lip whilst 23% of liners paired with Rejuvenate necks had evidence of a raised lip (p < 0.0001). The height of the raised rims of the DM cups paired with ABGII necks had a median (range) of 139 μm (72-255). The height of the raised rims of the DM cups paired with Rejuvenate necks had a median (range) of 52 μm (45-90) (p < 0.0001). CONCLUSION: Our new findings from retrieved dual mobility bearings showed that polyethylene liner rim deformation resulting from impingement with the femoral neck occurs in early in-human function, is circumferential in distribution, and is affected by the stem neck design. We recommend the use of highly polished and non-edged neck designs when used in conjunction with DM cups

Update on pediatric hip imaging

Hip disorders are common in children. Prompt diagnosis and treatment are important because of the potential complications. Symptoms are frequently nonspecific, and clinical examination can be difficult and unreliable, especially in smaller children. Therefore, imaging can be valuable. Radiography and ultrasound remain the initial imaging modalities of choice. Increasingly, magnetic resonance imaging is obtained for assessing the pediatric hip, although the long imaging time and need for sedation may limit its use in daily practice. Because of the exposure to ionizing radiation, the use of computed tomography and bone scintigraphy in children is limited to selected cases. Pediatric hip pathology varies depending on patient age. This article provides an overview of common hip pathologies in children including congenital and developmental pathologies, trauma, infectious processes, inflammatory disease, and neoplasm. The age of the child, history, and clinical examination are essential to narrow down the differential diagnosis and subsequent selection of the appropriate imaging modality

Luxación anterior de cadera: presentación de un caso y revisión de la literatura.

La luxación anterior de cadera es una lesión poco frecuente y que se produce por traumatismos de alta energía. Este tipo de luxación requiere maniobras especiales para su reducción. El tratamiento ortopédico puede dar buenos resultados, aunque en ocasiones es necesaria la reducción abierta y el tratamiento quirúrgico de lesiones asociadas. Presentamos el caso de un varón de 27 años que presentaba una luxación anterior de cadera derecha debido a accidente automovilístico. Además tenía lesiones asociadas en pie derecho. Se realizó reducción cerrada y tratamiento conservador con buenos resultados. El pronóstico de una luxación de cadera depende de la gravedad de la lesión así como del tiempo que se tarda en realizar la reducción, que está relacionando con el riesgo de desarrollo de necrosis avascular. La luxación anterior de cadera tiene mejor pronóstico que la luxación posterior cuando se realiza un tratamiento temprano adecuado.The anterior hip dislocation is a little frequent injury and is produced by high energy traumatisms. This type of dislocation requires special maneuvers for its reduction. The orthopaedic treatment can give good results, although sometimes it is necessary the open reduction and the surgical treatment of associate injuries. We present a case of a 27 year-old man who presented an anterior hip dislocation due to automobile accident. He had associated injuries on right food. He was treated by closed reduction and orthopaedic treatment and he had good results. The prognosis of a hip dislocation depends on the gravity of the injury as well as the time that takes in realizing the reduction, that it is relating to the risk of development of avascular necrosis. The anterior hip dislocation has better prognosis than the posterior dislocation when a suitable treatment is early realized