The Exeter-Trident THA with ceramic-on-ceramic-bearings: 10-year outcomes in 275 total hip arthroplasties.

AIMS: This study reports on the Exeter-Trident total hip arthroplasty (THA) using an alumina ceramic-on-ceramic bearing with 10-year clinical and radiographic follow-up. PATIENTS AND METHODS: Between January 2001 and January 2006, 275 THAs were performed. Mean age at surgery was 52.7 (17-86) years, with 84 patients (33.6%) aged <50 years. The primary outcome was all-cause construct survival at minimum 10 years. Secondary outcomes included functional and noise scores. Radiographs were compared between baseline and latest follow-up and assessed for component loosening, migration and lysis. RESULTS: No patient was lost to follow-up. Mean follow-up for surviving patients was 12.5 (9.5-15.6) years. Kaplan-Meier survival for all-cause revision was 94.0% (95% CI, 90.5-97.5) at 14.3 years. 2 patients had a femoral component fracture. All scores improved significantly at latest follow-up. HSS-NQ for 247 hips (90.2%) at mean 9.1 (7.0-14.4) years post implantation showed most hips (93.1%) reported no more than occasional noise. At minimum 5 years, radiolucency around the acetabular component was observed in 2 hips (0.8%), and lysis at the interface in 1 hip (0.4%). On the femoral side, endosteal lysis was observed in 7 hips. CONCLUSIONS: The Exeter-Trident THA with alumina ceramic-on-ceramic bearings performed well in this population. Patients are at low risk of revision in the first decade. However, there is a small risk of stem fracture as a late complication and some patients experience significant noise.

A Rare Volar Carpo-metacarpal Joint Dislocation in a Child: A Case Report and Literature Review.

Introduction: Carpometacarpal joint (CMCJ) dislocations are a rare presentation and a volar dislocation in a pediatric patient even more so. We present a case of this condition along with management strategies to help guide future treatment of this injury. Case Report: A fit and well 8-year-old boy presented with pain and deformity of his right hand following a fall from a horse. He had no history of previous trauma or injury to this hand. X-rays demonstrated a volar dislocation of the second CMCJ, along with several metacarpal base fractures. This injury was managed emergently with closed reduction in the Emergency Department and then underwent definitive treatment through percutaneous Kirschner wire (K-wire) fixation 2 days after injury. At 3- month follow-up, the patient and his family reported no pain, and on examination, there was no deformity and he had excellent range of motion. The patient had already returned to horse riding with no issues. Conclusion: A volar carpometacarpal dislocation in a pediatric patient is an uncommon presentation. We were able to achieve a full functional recovery using a mixture of closed reduction and K-wire fixation techniques. This clinical experience offers several learning points and also guidance around management strategies for future presentations of this condition.

IMPACT OF THE ENDF/B-VIII.0 LIBRARY ON MCNP6.2-COMPUTED AMBIENT AND PERSONAL DOSE EQUIVALENT CONVERSION COEFFICIENTS.

The 2018 release of the Evaluated Nuclear Data File (ENDF)/B-VIII.0 library initiated several examinations of the impact of the revised nuclear data on Monte Carlo models. This study used version 6.2 of the Monte Carlo N-Particle® code (MCNP6.2) with the ENDF/B-VI and ENDF/B-VIII.0 libraries to compute conversion coefficients for fluence-to-ambient and fluence-to-personal dose equivalent from neutron energy groups described by an International Atomic Energy Agency 53-bin structure and 47 monoenergetic neutron sources listed in International Commission on Radiological Protection (ICRP) 74. The MCNP6.2 models with ENDF/B-VI data were validated against results published in 2005 by Veinot and Hertel. Conversion coefficients computed with MCNP6.2 and ENDF/B-VIII.0 slightly underestimated the ICRP 74 values but were within ICRP-specified tolerances and do not justify revising the ICRP coefficients. Conversion coefficients for personal dose equivalent were computed with MCNP6.2 and ENDF/B-VIII.0 at four angles of incidence greater than those available in ICRP 74. These new coefficients are relevant to radiation protection studies of interest to US defence-focused organisations.

DOSE CONVERSION COEFFICIENTS FROM MONOENERGETIC NEUTRONS COMPUTED WITH THE MCNP6.2 CODE IN THE VIP-MAN PHANTOM.

Computational estimates of dosimetric quantities from external exposures to neutron fields are valuable to ongoing radiation protection studies that are of interest to US defense-focused organizations. Conversion coefficients for fluence-to-absorbed dose and fluence-to-effective dose were computed using version 6.2 of the Monte Carlo N-Particle® code (MCNP6.2) in the visible photographic man (VIP-Man) numerical model for 45 monoenergetic neutron fields between 10-9 and 20 MeV under six irradiation geometries. Comparisons to the formative VIP-Man study by Bozkurt et al. revealed excellent agreement. The mean relative difference between our VIP-Man/MCNP6.2-computed and the International Commission on Radiological Protection (ICRP) 116-published absorbed dose conversion coefficients in 14 organs and remainder tissues under all geometries was 4.7%, which is within ICRP-reported variations. The effective dose coefficients computed with VIP-Man/MCNP6.2 were strongly similar to ICRP 116 values in all geometries except for posterior-anterior, where the difference was attributed to shielding of anterior organs by the relatively fatty composition of the VIP-Man phantom.

APPLICATION OF THE MCNP6.1 CODE TO ESTIMATE THE DIRECTIONAL DEPENDENCE OF RADIATION PROTECTION FACTOR VALUES FOR A SIMPLE SURROGATE VEHICLE.

Radiation protection factor (RPF) values are relevant to various US defense and civil support organizations. An equation was developed to quantify the angular-dependent protection of a shielding configuration in the presence of a mono-energetic radiation field. Values of ambient dose equivalent, H*(10), were computed with version 6.1 of the Monte Carlo N-Particle Code (MCNP6.1) for more than 70 distinct, mono-energetic, planar photon and neutron fields using both the kerma approximation and energy deposition from primary and secondary radiations. The two computational approaches were compared, and the MCNP6.1 models were then modified to simulate the same radiation fields and compute values of directional dose equivalent, H'(10,α), in a tissue sphere centered inside a surrogate vehicle for 13 angles of incidence. Values of H*(10) and H'(10,α) were recast as energy- and angular-dependent RPF values for the incident field-shielding geometries and tabulated. Examples of implementation are provided, and limitations are discussed.

Retrospective cohort study of operatively treated ankle fractures involving the posterior malleolus.

BACKGROUND: Direct fixation of the posterior malleolus through a posterolateral approach is increasing in popularity. However, data is limited, and no studies have stratified results by posterior malleolus size. METHODS: A retrospective cohort study of patients with posterior malleolus (PM) fractures undergoing internal fixation over an 18-month period was conducted. Radiographic and patient reported outcomes measures (PROMs) were assessed. 75 patients were included, and 31 returned Manchester-Oxford Foot and Ankle (MOXFQ), EQ-5D-3 L, 5-point Likert satisfaction questionnaires. Mean age was 56.2 years, 68% were female, mean ASA was 1.72, 6.7% were diabetic, and average surgical time was 75.7 min (±40.9). RESULTS: Overall, the MOXFQ summary score was 26.9 (±25.8), with the pain domain showing the most severe score 32.4 (±24.0). The EQ-5D VAS index was 0.75 (±0.24). Larger PM size was associated with more anatomical reduction (58.8%, n = 20 of <10% vs. 90.9%, n = 10 of >30%) and larger sized fragments were more likely to be fixed posteriorly. Best PROMs were observed in PM fragments <10%, and the worst in fragments 10-20%. A tendency towards more secondary surgery was observed with posterior subluxation 21.9% (n = 7) vs. 7.0% (n = 3) (p = 0.06). CONCLUSIONS: Patients with fragments >10% have an intra-articular injury. We recommend direct anatomic reduction and rigid internal fixation. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

Should we use dabigatran or aspirin thromboprophylaxis in total hip and knee arthroplasty? A natural experiment.

BACKGROUND: Despite long clinical experience some authorities recommend against the use of aspirin for perioperative VTE prophylaxis and favour alternatives such as dabigatran. A change from Dabigatran to an Aspirin based protocol in a British district general hospital created the conditions of a natural experiment. METHODS: We conducted a single centre, retrospective study of 6-months using a dabigatran based protocol (THA n = 191, TKA n = 155) and 6-months using and aspirin based protocol (THA n = 165, TKA n = 136). Outcomes addressed include: VTE used, VTE events within 90-days, 30-day return to theatre (RTT) rates, and 90-day mortality. RESULTS: Pre-intervention, the dabigatran prescription rate was 73% (n = 139) and 78% (n = 123) with aspirin prescription post-intervention in 67% (n = 110) and 70% (n = 90) for THA and TKA respectively. We found a similar VTE rate when comparing dabigatran and aspirin groups for THA (2.2% vs. 0%, p = 0.17) and TKA (0.64% vs. 0%, p = 0.32). Similarly, no difference in the RTT rate was seen for THA (0.7% vs.2.7%, p = 0.23) or TKA (1.6% vs. 3.2%, p = 0.38). CONCLUSION: No significant differences in safety were found comparing aspirin to dabigatran for VTE prophylaxis for lower limb arthroplasty which, has not been previously reported and represents significant cost saving implications.

Estimating radiation protection factor (RPF) values for a simple surrogate vehicle using the MCNP6.1 code.

Computational and experimental estimates of radiation protection factor (RPF) values are of significant interest to various defense-related organizations. Values of the operational quantity of ambient dose equivalent were computed, using version 6.1 of the Monte Carlo N-Particle® code (MCNP6.1), for 25 photon energies and 53 neutrons energies. Energy-dependent values for absorbed dose at a 10-mm depth in the 30-cm-diameter ICRU tissue-equivalent sphere, D*(10), were estimated using the kerma approximation for photon (MCNP F6:p tally) and neutron (MCNP F6:n tally) radiation fields, and then transformed to fluence-to-ambient dose equivalent conversion coefficients, H*(10)/ϕ, using appropriate quality factors, Q, and radiation fluences. MCNP6.1-computed values of H*(10)/ϕ were compared with tabulated values from ICRP Publication 74. The published conversion coefficients for photon radiation fields were within the error bounds of all MCNP6.1-calculated values. For neutron fields, the computed and published conversion coefficients agreed within calculated error bounds for neutron energies of 100 keV and above, while responses to neutron fields below 100 keV exhibited the same shape and were consistent with the kerma approximation applied in the computational model. The MCNP6.1 models were then modified to simulate the same radiation fields, but H*(10)/ϕ conversion coefficients were calculated in the shielded environment of a surrogate vehicle (steel cube)-in keeping with historical and recent studies-and the ratios of shielded and unshielded vehicle response functions were expressed as energy-dependent RPF values. The MCNP6.1-computed neutron RPF values were compared with two prior experimental studies involving a mono-energetic neutron source and a high-yield, short-duration fission neutron spectrum and found to agree within the uncertainty of the experimentally-measured values. Limitations of the computed RPF values are discussed.