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Robotic-assisted total knee arthroplasty (rTKA) has been developed to improve knee kinematics and functional outcomes, expedite recovery, and improve implants long-term survivorship. Robotic devices are classified into active, semi-active, and passive, based on their degree of freedom. Their capacity to provide increased accuracy in implants positioning with reduced radiographic outliers has been widely proved. However, these early advantages are yet to be associated with long-term survivorship. Moreover, multiple drawbacks are still encountered including a variable learning curve, increased setup and maintenance costs, and potential complications related to the surgical technique. Despite recent technologies applied to TKA have failed to prove substantial improvements, robotic-assisted surgery seems to be here to stay and revolutionize the field of TKA. To support its consistent usage on a daily basis, long-term results are still awaited, and further improvements are necessary to reduce the expenses related to it.

Background: C-reactive protein (CRP) to Albumin ratio (CAR) has been used in multiple clinical settings to predict early mortality. However, there is a lack of evidence on the predictive role of CAR in 30-day mortality after a hip fracture. The purpose of this study was to establish a potential association between CAR and 30-day mortality and to assess if the CAR Receiving Operating Characteristics curve (ROC) can be a reliable predictor of early mortality. Methods: We retrospectively reviewed the charts of 676 patients (>65 years) treated for hip fracture between 2006 and 2018. All hip fractures were included. Treatment strategies included closed reduction and internal fixation, open reduction and internal fixation, hemiarthroplasty, or total joint arthroplasty. Statistical analysis included T-test, Pearson correlation for CAR and other markers, ROC curves and area under the curve, Youden Model, and Odds Ratio. Results: The 30-day mortality rate analysis showed that higher preoperative levels of CAR were associated with higher early mortality. When analyzing the area under the ROC curve (AUROC) for 30-day mortality, the reported value was 0.816. The point of the ROC curve corresponding to 14.72 was considered a cut-off with a specificity of 87% and a sensibility of 40.8%. When analyzing values higher than 14.72, the 30-day mortality rate was 17.9%, whilst, for values lower than 14.72, the 30-day mortality rate was 1.8%. Conclusions: Patients older than 65 years affected by a hip fracture with increased preoperative levels of CAR are associated with higher 30-day mortality. Despite a moderate sensibility, considering the low cost and the predictivity of CAR, it should be considered a standard predictive marker.

The explicit derivation for the orbital precession of the S2 star in the Galactic Center in the Scalar-Tensor-Vector Gravity is discussed and compared with previous research. The two different predictions are validated by numerically integrating the geodesic equations for a test particle., Comment: 4 pages, 2 figures, 1 appendix. Accepted for publication in MNRAS

We use the kinematic data of the stars in eight dwarf spheroidal galaxies to assess whether $f(R)$ gravity can fit the observed profiles of the line-of-sight velocity dispersion of these systems without resorting to dark matter. Our model assumes that each galaxy is spherically symmetric and has a constant velocity anisotropy parameter $\beta$ and constant mass-to-light ratio consistent with stellar population synthesis models. We solve the spherical Jeans equation that includes the Yukawa-like gravitational potential appearing in the weak field limit of $f(R)$ gravity, and a Plummer density profile for the stellar distribution. The $f(R)$ velocity dispersion profiles depend on two parameters: the scale length $\xi^{-1}$, below which the Yukawa term is negligible, and the boost of the gravitational field $\delta>-1$. $\delta$ and $\xi$ are not universal parameters, but their variation within the same class of objects is expected to be limited. The $f(R)$ velocity dispersion profiles fit the data with a value $\xi^{-1}= 1.2^{+18.6}_{-0.9}$ Mpc for the entire galaxy sample. On the contrary, the values of $\delta$ show a bimodal distribution that picks at $\bar{\delta}=-0.986\pm0.002$ and $\bar{\delta}=-0.92\pm0.01$. These two values disagree at $6\sigma$ and suggest a severe tension for $f(R)$ gravity. It remains to be seen whether an improved model of the dwarf galaxies or additional constraints provided by the proper motions of stars measured by future astrometric space missions can return consistent $\delta$'s for the entire sample and remove this tension., Comment: 11 pages, 4 figures, 2 Tables. Accepted for publication on MNRAS

INTRODUCTION Baastrup disease (BD) is a common cause of low back pain which is often underdiagnosed. It is characterized by adjacent interspinous processes contact and it can be associated with cystic lesions. The aim of this review is to evaluate the epidemiology, diagnosis, and treatment options of patients with BD. EVIDENCE ACQUISITION The present study is performed according to PRISMA statement. MEDLINE via PubMed and Embase, Scopus, Cochrane Library database were searched using the keywords: "Baastrup", "Kissing Spines", "Syndrome", "Disease". A total of 35 papers met our inclusion criteria. Full text were reviewed for demographic, clinical data and treatment. EVIDENCE SYNTHESIS 1308 patients were included in the studies. The mean age of the enrolled patients was 59.6 years. The M:F ratio was 1.3:1. Population-based studies demonstrated a decade on decade increase in the incidence. Standard and dynamic flexion-extension radiographs of the lumbar spine were performed in 213 (16.2%) of cases. MRI was performed in 735 patients (56,2%) whereas FDG PET/CT was used to demonstrate BD in 77 included cases (5.9%). CT scan was performed in 574 cases (43.9%). 26 studies reported the treatment choice for a total of 277 patients. Anti-inflammatory drugs and physical therapy were chosen in 99 cases (35.7%). Percutaneous infiltrations and surgical decompression in 80 (28.9%) and 196 (70.7%) patients respectively. CONCLUSIONS Baastrup disease is a common cause of low back pain. Proper diagnosis needs for imaging investigations and dynamic flexion-extension radiographs. Conservative and surgical therapies are available but there is a need for randomized clinical trials.

Background Several studies have evaluated the survivorship and clinical outcomes of constrained acetabular liners (CALs) in complex primary and revision total hip arthroplasty with hip instability; however, there remains no consensus on the overall performance of this constrained implant. We therefore performed a systematic review of the literature to examine survivorship and complication rate of CAL usage. Methods A systematic review of the literature in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines was performed. A comprehensive search of PubMed, MEDLINE, EMBASE, and the Cochrane Database of Systematic Reviews was conducted for English articles using various combinations of keywords. Results In all, 37 articles met the inclusion criteria. A total of 4152 CALs were implanted. The all-cause reoperation-free survivorship was 79.9%. The overall complication rate was 22.2%. Dislocation was the most common complications observed and the most frequent reason for reoperation with an incidence of 9.4% and 9.2%, respectively. Infection after CAL placement had an incidence of 4.6%. The reoperation rate for aseptic acetabular component loosening was 2.9%. Overall, patients had improved outcomes as documented by postoperative hip scores. Conclusion CALs usage have a relatively high complication rate, particularly when compared with current bearing alternatives (dual mobility cups and large diameter femoral heads), however, it remains a valuable salvage procedure in complex patients affected by recurrent dislocation and implant instability. Newer designs have shown reduced impingement and higher survivorship free from dislocation. However, CALs should only be used when the reasons of instability have been correctly recognized and optimized.

Two-to 6-year results of reconstruction of severe bone defects in revision total knee arthroplasty (TKA) with highly porous tantalum cones have been encouraging, but 10-year follow-up is lacking. The purpose of this study was to determine the minimum 10-year results of tantalum cones in revision TKA.From 2005 to 2010, 30 consecutive patients (30 knees) underwent revision TKA with the use of cones. All patients were followed clinically and radiographically for a minimum of 10 years. A total of 42 cones (25 tibial and 17 femoral) were used to reconstruct massive bone defects classified as Anderson Orthopaedic Research Institute Types 2A (10), 2B (12), and 3 (19). The mean age of the patients was 73 years (range, 55 to 84) at the time of revision. The indication for the revision included aseptic loosening (15 patients) and second-stage reimplantation for deep infection (15 patients). Six patients were lost to follow-up.In total, 6 cones had to be revised. Minimum 10-year cone survivorship for any reason was 81% (25 of 31 cones). With cone revision for aseptic loosening as the end point, survivorship was 96% (30 of 31). No evidence of loosening or migration of any implant was noted on the most recent radiographs.Metaphyseal fixation with tantalum cones in revision TKA demonstrated excellent survivorship and fixation at a minimum follow-up of 10 years. This type of metaphyseal reconstruction can be a durable option for revision TKA in patients who have massive bone defects.

Background Several studies have evaluated the outcomes of tantalum cones in revision knee arthroplasty with moderate-to-severe metaphyseal bone defects. However, recent innovations have led to the development of 3-D printed titanium cones to better adapt to host bone, there remains no consensus on their overall performance. Objective We therefore performed a systematic review of the literature to examine short-term survivorship and complication rates of their usage in revision TKAs. Methods A systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A comprehensive search of PubMed, MEDLINE, EMBASE, and the Cochrane Database of Systematic Reviews was conducted for English articles using various combinations of keywords. Results In all, 7 articles met the inclusion criteria. A total of 687 cones were implanted in 557 revision TKAs. The all-cause revision-free survivorship of the implants was 95.3% (26 revisions), and of the cones was 95.5% (31 cones revised) at mean 24 months follow-up. The cones revision-free survivorship from aseptic loosening was 99.7%. The overall complication rate was 19.7% with infection as the most common complications observed and the most frequent reason for revision with an incidence of 10.4% and 4.1%, respectively. Overall, functional outcomes improved as documented by postoperative knee scores. Conclusion 3-D printed metal cones represent a reliable option in metaphyseal bone defects reconstruction that provides high fixation, good short-term survivorship, and complications rates in line with similar devices. In addition, they are associated with lower intraoperative complications, and higher survivorship from aseptic loosening.

Purpose Knee instability is considered one of the most frequent cause of failure after primary total knee arthroplasty (TKA). In order to address intraoperative instability, varus-valgus constrained knee implants (VVC) are increasingly utilized in primary TKA. Despite an increased risk of mechanical failure, short to mid-term results seem to be encouraging, but long-term results are still lacking. Methods A systematic review of prospective and retrospective studies that reported clinical outcomes of patients with VVC systems in primary TKAs between 1990 and 2020 was performed. Results In all, 28 articles met our inclusion criteria. A total of 2798 VVC implants were used in primary TKA. The all-cause revision-free survivorship was 95.2% at a mean follow-up of 7 years. Infection and aseptic loosening were the most common reasons for reoperation with an incidence of 1.8% and 1.7%, respectively. Overall complication rate was 9.6%, the most common complications were knee stiffness and infection with an incidence of 2.8% and 2.5%, respectively. Conclusions VVC implants in primary TKA are associated with improved functional outcomes and good mid-term survivorship, comparable to lower level of constraint implants. Non-modular stemless seem to be reliable implants at mid-term follow-up. However, given the lack data coming from long-term studies, VVC implants should be used cautiously in primary TKA.

Introduction Medial Pivot Total Knee Arthroplasty was introduced in clinical practice in 1990s to reproduce the in vivo-natural knee kinematics. This design is characterized by an asymmetric constraint profile, with aa highly congruent medial compartment, and a less congruent lateral compartment. Short-term outcomes of the medial pivot systems in primary knee arthroplasty have been widely reported in the current literature, however, only few studies have described results beyond 5-year follow-up. Objectives The primary objectives of this systematic review of the literature is to analyze the mid-term studies on medial pivot total knee arthroplasty focusing on the reoperation rate, survivorship and clinical outcome scores. Methods The US National Library of Medicine (PubMed/MEDLINE), EMBASE, and the Cochrane Database of Systematic Reviews were queried for publications from January 1980 to December 2019 utilizing the following keywords: “medial pivot”, “medial stabilized”, “medial rotating”, “medial congruent”, medial ball and socket”, “arthroplasty”, “TKA”, “TKR”, and “knee surgery”. Results 18 articles met the inclusion criteria for the present study. The average quality was 11.4 for non-comparative studies and 21.7 for comparative studies based on MINORS criteria. A total 2832 knee arthroplasties were included for the final analysis with an average age of 69 years, and an average follow-up of 8.1 years (minimum 5 years). The overall reoperation rate was 2.4%, with periprosthetic joint infection as the leading cause of revision in 0.9% of cases, followed by aseptic loosening in 0.4% of cases. The average Knee Society Score improved to a mean preoperative score of 40.1 to a mean postoperative score of 89.2. The functional knee society score improved from a mean preoperative score of 44.8 to an average postoperative score of 82.9. The global range of motion improved from 104.8° preoperatively to 115.6° postoperatively. Conclusion We found that medial pivot system in primary total knee arthroplasty provide overall mid-term survivorship comparable to other standard implasnts. In addition, medial pivot system is associated with better high-end function compared to standard implants.

Severe acetabular bone defects during revision total hip arthroplasty are often treated with a hemispherical shell and highly porous modular metal augments. Several papers have been already published reporting on the clinical performance of trabecular metal (TM) augments combined with a hemispherical shell for the management of severe acetabular defects. However, no systematic review of the literature has been published to date. The U.S. National Library of Medicine (PubMed/MEDLINE), EMBASE, and the Cochrane Database of Systematic Reviews were queried for publications utilizing keywords pertinent to tantalum augments and TM (Zimmer Biomet, Warsaw, Indiana) augments, revision THA, clinical outcomes, and complications associated with these procedures. Fifteen articles were found to be suitable for inclusion in the present study, which included 769 revision cases where acetabular augments were used. The majority of acetabular bone defects were type 3 according to the Paprosky classification (type 2A in 58 cases, 7.2%; type 2B in 139 cases, 17.2%; type 2C in 72 cases, 8.9%; type 3A in 360 cases, 44.7%; and type 3B in 177 cases, 22.0%). The overall revision rate for the 769 acetabular revisions with augments was 5.7% (46 cases) at mean mid-term follow-up. The most common reasons for revision were dislocation (3.3%), periprosthetic joint infection (2.9%), and aseptic loosening (2.7%). TM augments combined with hemispherical shells were found to be effective in the treatment of moderate-to-severe acetabular bone defects with a 5% acetabular component revision rate at mean mid-term follow-up. The literature did not delineate whether pelvic discontinuity was associated with a higher risk of aseptic loosening after TM augment. Further studies are needed to clarify the impact of additional screw fixation on survival rates, and whether the type of augment (wedge augments, “flying buttress” augments, column augments), the configuration used, and the number of screws influence clinical and radiographic outcomes.

Background The ability to utilize magnetic resonance imaging (MRI) to assess bony fixation in 3 dimensions may allow a better understanding of the implant design and bony integration. We hypothesized that a new 3-dimensionally printed cementless highly porous acetabular component (Stryker Trident II TritaniumTM) would show better fixation than an earlier cup from the same manufacturer as assessed by the noninvasive technique of multispectral MRI. Methods Multiacquisition variable-resonance image combination selective metal suppression MRI was performed in 19 patients implanted with a new 3-dimensionally printed cup and 20 patients who had received a previous-generation cup from the same manufacturer at 1-year follow-up. Each cup was graded globally as well as by 9 specific zones. Integration grades were performed for each zone: 0, full bone integration; 1, fibrous membrane present; 2, osteolysis; and 3, fluid present. A mixed-effects logistic regression model was used to compare fixation between the 2 groups. Results All cups in both cohorts showed greater than 90% radiographically estimated global bony integration (3-dimensionally printed cups, 99.4%; regular cups 91.6%) with no osteolysis or fluid observed in any cup. The 3-dimensionally printed cup had 1 of 171 zones (0.6%) graded as fibrous membrane present, while the 2-dimensional group had 15 of 180 zones (8.3%) graded as fibrous. Of note, screw hole regions were omitted but may be read as fibrous membrane areas. Conclusion Using multiacquisition variable-resonance image combination selective MRI, our analysis showed greater biologic fixation and less fibrous membrane formation in the 3-dimensionally printed cups than the control group at 1-year follow-up.

BackgroundThe purpose of this study was to evaluate (1) the reoperation rates and survivorship for septic and aseptic causes, (2) radiographic outcomes, and (3) clinical outcomes of condylar-constrained knee (CCK) implants used in primary total knee arthroplasty (TKA) with severe coronal deformity and/or intraoperative instability.Materials and methodsA consecutive series of CCK implants in primary TKA was retrospectively evaluated in patients with severe coronal deformities. Forty-nine patients (54 knees) were included with a mean follow-up of 9 years (range 6–12). All patients were treated with a single-design, second-generation CCK implant. The primary diagnosis was osteoarthritis in 36 knees, post-traumatic arthritis in 7 knees, and rheumatoid arthritis in 4 knees. Preoperatively, standing femorotibial alignment was varus in 22 knees and valgus in 20 knees.ResultsAt a mean follow-up of 9 years, overall survivorship was 93.6%. Two knees (4.3%) required revision for periprosthetic joint infection. One knee (2.1%) required subsequent arthroscopy due to patellar clunk syndrome. At final follow-up, no evidence of loosening or migration of any implant was reported, and the mean Knee Society knee scores improved from 43 to 86 points (p p ConclusionCCK implants in primary TKA with major coronal deformities and/or intraoperative instability provide good midterm survivorship, comparable with less constrained implants. In specific cases, CCK implants can be considered a viable option with good clinical and radiographic outcomes. However, a higher degree of constraint should be used cautiously, leaving the first choice to less constrained implants.Level of evidenceTherapeutic study, level IV.

Introduction: In conjunction with impaction bone grafting (IBG), metal meshes have been proposed to minimise defects of the medial and superolateral walls in order to convert combined complex uncontained segmental defects into contained cavitary defects to facilitate IBG. Methods: The US National Library of Medicine (PubMed/MEDLINE), EMBASE, and the Cochrane Database of Systematic Reviews were queried for publications from January 1980 to March 2019 utilising keywords pertinent to total hip arthroplasty (THA), acetabular impaction bone grafting, clinical or functional outcomes, revision THA, or postoperative complications. Results: 7 articles were found to be suitable for inclusion in the present study. The mean modified Coleman methodology score for methodological deficiencies of the studies was 45.3 (range 38–59). Severe acetabular bone loss was present in 56% of cases having moderate bone loss in 18%, and mild in 26%. The all-cause reoperation rate was 7.4%, while the all-cause revision rate of the acetabular component was 6.2%. Conclusions: IBG with mesh is effective for selected patients with acetabular bone defects. Most patients with moderate bone loss as well as selected patients with large superolateral defects can be successfully treated with IBG combined with mesh. There is limited data to show that IBG with mesh might be associated with decreased survival rates in patients with severe lateral defects (Paprosky IIIA) combined with ischial or medial wall osteolysis who require combined medial and lateral meshes. In addition, patients with severe superomedial migration of the cup (Paprosky IIIB) should not be treated with IBG and mesh.

Background: It has not been determined yet whether hip arthroscopy (HA) leads to adverse outcomes after total hip arthroplasty (THA). The purpose of this study was to (1) determine 2-year conversion rate of HA done for osteoarthritis (OA) to THA and (2) explore the relationship between HA performed in patients with hip osteoarthritis and the risk of revision THA within 2 years of index arthroplasty. Methods: Data was collected from the Medicare Standardized Analytic Files insurance database using the PearlDiver Patient Records Database from 2005–2016. Patients were stratified into 2 groups based upon a history of hip arthroscopy prior to THA. Results: The 2-year conversion to THA rate for hip arthroscopy in patients with OA was 68.4% (95% CI, 66.2–70.6%). Multivariate analysis demonstrated that OA patients who underwent HA prior to THA were at an increased risk of revision surgery (OR 3.72; 95% CI, 3.15–4.57; p = 0.012), periprosthetic joint infection (OR 1.86; 95% CI, 1.26–2.77, p = 0.010) and aseptic loosening (OR 2.81; 95% CI, 1.66–4.76; p Conclusions: Analysis of a large insurance database found the conversion rate from HA performed in Medicare OA patients to THA within 2 years is unacceptably high. Hip arthroscopy prior to THA also significantly increased the risk of THA revision within 2 years after index THA. These results suggest that arthroscopic hip surgery should not be performed in patients with a diagnosis of OA as conversion rates are high and revision rates post THA are significantly increased.

Several clinical trials have retrospectively evaluated the role of extended trochanteric osteotomy in two-stage total hip arthroplasty (THA) revision for the management of periprosthetic joint infection of the hip. However, no systematic review of the literature has been published to date to evaluate the clinical, functional, and radiographic outcomes of extended trochanteric osteotomy (ETOs) performed as part of implant removal during a two-stage revision for the management of periprosthetic joint infection (PJI). The US National Library of Medicine (PubMed/MEDLINE), and the Cochrane Database of Systematic Reviews were queried for publications from January 1980 to April 2019 using the following keywords: “extended” AND “trochanteric” AND “osteotomy.” Six studies included in this systematic review assessed 305 cases (281 patients) of PJI treated surgically with two-stage revision combined with ETO at the first stage. The mean overall union rate of the ETO was 97%, while the overall rate of radiographic femoral stem subsidence >5 mm was 5%. In addition, the overall mean infection-free rate of two-stage revision combined with ETO was 94% (288 out of 305 operated hips), while the overall complication rate requiring reoperation was 8% (26 out of 305 operated hips). Finally, there was some evidence to show that two-stage revision with ETO was associated with improved infection-free rates compared with two-stage revision without ETO. ETO seems safe and effective in patients with well-fixed femoral stems who require two-stage THA revision for the management of chronic PJI. Two-stage revision with ETO might result in improved infection-free rates compared with two-stage revision without ETO.

Recently, a variety of studies have analyzed the potential correlation between lumbar degenerative disease (LDD) and inferior clinical outcomes after total hip arthroplasty. However, there has been limited data concerning the role of LDD as a risk factor for failure after total knee arthroplasty (TKA). The aim of our study was to determine: (1) what is the association of LDDs with TKA failure (all-cause revision) within 2 years of index arthroplasty and (2) if patients with LDD and lumbar fusion are at increased risk of TKA revision within 2 years compared with LDD patients without fusion. Data were collected from the Humana insurance database using the PearlDiver database from 2007 to 2017. To assess aim 1, patients were stratified into two groups based on a prior history of LDD (International Classification of Diseases [ICD]-9 or -10 diagnostic codes). To analyze aim 2, patients within the LDD cohort were stratified based on the presence of lumbar fusion (lumbar fusion Current Procedural Terminology code). All-cause revision rate was 3.4% among LDD patients versus 2.4% of patients with non-LDD (p

In this paper, we study the Jeans analysis in the context of energy-momentum-squared gravity (EMSG). More specifically we find the new Jeans mass for non-rotating infinite mediums as the smallest mass scale for local perturbations that can be stable against its own gravity. Furthermore, for rotating mediums, specifically for rotating thin disks in the context of EMSG, we find a new Toomre-like criterion for the local gravitational stability. Finally, the results are applied to a hyper-massive neutron star, as an astrophysical system. Using a simplified toy model we have shown that, for a positive (negative) value of the EMSG parameter $\alpha$, the system is stable (unstable) in a wide range of $\alpha$. On the other hand, no observational evidence has been reported on the existence of local fragmentation in HMNS. Naturally, this means that EMSG with positive $\alpha$ is more acceptable from the physical point of view., Comment: 21 pages, 6 figs, Published (EPJC)

In this paper, we introduce the post-Minkowskian approximation of Energy-Momentum-Squared Gravity (EMSG). This approximation is used to study the gravitational energy flux in the context of EMSG. As an application of our results, we investigate the EMSG effect on the first time derivative of the orbital period of the binary pulsars. Utilizing this post-Keplerian parameter, the free parameter of the EMSG theory, $f_0'$, is estimated for six known binary pulsars. Taking the binaries that have the most accurate observations, it turns out that $-6\times 10^{-37}\text{m}\,\text{s}^2\text{kg}^{-1}, Comment: 21 pages, 5 figures URL: https://link.aps.org/doi/10.1103/PhysRevD.105.044014

It is well known that N-body simulations of ultralight bosons show the formation of a solitonic dark matter core in the innermost part of the halo. The scale length of such a soliton depends on the inverse of the mass of the boson. On the other hand, the orbital motion of stars in the Galactic Center depends on the distribution of matter whether be it baryonic or dark, providing an excellent probe for the gravitational field of the region. In this Letter we propose the S-stars in the Galactic Center as a new observational tool, complementary to other astrophysical systems, to narrow down the range of allowed values for an ultralight dark matter candidate boson mass. We built mock catalogs mirroring the forthcoming astrometric and spectroscopic observations of S2, and we used a MCMC analysis to predict the accuracy down to which the mass of an ultralight boson may be bounded, and we showed that, once complementary constraints are considered, this analysis will help to restrict the allowed range of the boson mass. Our analysis forecasts the bound on the mass of an ultralight boson to be $< 10^{-19}$ eV at the 95% of confidence level., 5 pages, 2 figures, 1 table, 5 appendices. Accepted for publication in A&A Letters. Publication title changed with respect to previous versions during the editorial process

We present a rare case of a patient who presented with complete and rapid wear-through of a ceramic femoral head through a polyethylene liner and titanium acetabular cup. In addition, this patient exhibited significantly elevated serum titanium ion levels, which may serve as a marker of severe metallosis in cases where the preoperative plain radiographs underestimate signs of periarticular metal debris. The unique findings of this case include the rapid (less than 1 year time) wear-through of the femoral head in interval radiographs and the dramatic progression of metallosis and pelvic and femoral osteolysis that required both component revision. In addition, the markedly elevated titanium levels secondary to cup wear-through are also of interest and demonstrate a systemic manifestation of abrasive wear of a titanium alloy component. Keywords: Total hip arthroplasty, Revision arthroplasty, Wear-through cup failure, Catastrophic failure, Osteolysis, Ceramic on poly

The GRAVITY Collaboration achieved a remarkable detection of the orbital precession of the S2 star around the Galactic Center supermassive black hole, providing yet another proof of the validity of general relativity. The departure from the Schwarzschild precession is encoded in the parameter ${f}_{\mathrm{SP}}$, which multiplies the predicted general relativistic precession. This parameter results in ${f}_{\mathrm{SP}}=1.10\ifmmode\pm\else\textpm\fi{}0.19$, which is consistent with general relativity (${f}_{\mathrm{SP}}=1$) at $1\ensuremath{\sigma}$ level. Nevertheless, this parameter may also hide an effect of the modified theories of gravity. Thus, we consider the orbital precession due to the Yukawa-like gravitational potential arising in the weak field limit of $f(R)$-gravity, and we use the current bound on the ${f}_{\mathrm{SP}}$ to constrain the strength and the scale length of the Yukawa-like potential. No deviations from general relativity are revealed at the scale of $\ensuremath{\lambda}l6300\text{ }\text{ }\mathrm{AU}$ with the strength of the Yukawa potential restricted to $\ensuremath{\delta}=\ensuremath{-}{0.01}_{\ensuremath{-}0.14}^{+0.61}$.

Finite element (FE) models are frequently used to assess mechanical interactions between orthopedic implants and surrounding bone. However, FE studies are often limited by the small number of bones that are modeled; the use of normal bones that do not reflect the altered bone density distributions that result from osteoarthritis (OA); and the application of simplified load cases usually based on peak forces and without consideration of tibiofemoral kinematics. To overcome these limitations, we undertook an integrated approach to determine the most critical scenario for the interaction between an uncemented tibial component and surrounding proximal tibial bone. A cementless component, based on a modern design, was virtually implanted using computed-tomography scans from 13 patients with knee OA. FE simulations were performed across a demanding activity, stair ascent, by combining in vivo experimental forces from the literature with tibiofemoral kinematics measured from patients who had received the same design of knee component. The worst conditions for the bone-implant interaction, in terms of micromotion and percentage of interfacial bone mass at risk of failure, did not arise from the maximum applied loads. We also found large variability among bones and tibiofemoral kinematics sets. Our results suggest that future FE studies should not focus solely on peak loads as this approach does not consistently correlate to worst-case scenarios. Moreover, multiple load cases and multiple bones should be considered to best reflect variations in tibiofemoral kinematics, anatomy, and tissue properties. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:350-357, 2019.