Reduction Sequence Research Articles

Guomo open-air site (15–12 ka) in Guangxi Zhuang Autonomous Region, southern China: A new cobble-based industry for rethinking the definition of “Hoabinhian”

The Hoabinhian technocomplex is one of the most discussed topics in the Paleolithic research of Southeast Asia because it is the most representative phenomenon in terms of cobble tools. Recent discoveries of Hoabinhian sites in Yunnan Province, southwest China largely expanded its tempo-spatial presence in this part of the world. Whether Hoabinhian sites are present in other parts of southern China has remained elusive. Located close to northern Vietnam, where more than 150 Hoabinhian sites were reported to have been discovered since the 1920s, the Guangxi Zhuang Autonomous Region of China is a strategic area for exploring the issues concerning Hoabinhian phenomenon in this Chinese territory. This article presents a novel cobble-based industry of a recently discovered site—the Guomo open-air site, situated in the China-Vietnam border area. The lithic assemblages from layers 3 and 4 were dated to around 15–12 ka by the OSL dating method, and they manifest consistent and identical typo-technological characteristics. Four reduction sequences were defined for this lithic production, including 1) partial unifacial knapping on cobbles to produce various types of cutting tools; 2) cobble-split débitage via bipolar-on-anvil technique to produce semi-cobbles, and then they are unifacially shaped into unifaces; 3) cobble-throwing débitage by the throwing technique to obtain flat cortical flake blanks and tools; 4) recurrent unidirectional flaking on single-platform cores without preparation. Considering limited similarities and remarkable difference between “Hoabinhian” lithic industries of South China and of Southeast Asia, we suggest that Guomo site is an important case to raise the question of the definition of “Hoabinhian” and to study the variability of cobble-tool industries in this vast region.

Primary Knapping Methods in Upper Paleolithic Industries at the Ushbulak Site Based on the Results of Refitting (Layer 5.1)

Purpose. The aim of this study is detailed reconstruction of the reduction sequences of the layer 5.1 lithic industry.Results. Through a comprehensive analysis of the material complex from the layer 5.1 we reconstructed three knapping strategies characterizing the industry. The first strategy is based on the usage of the narrow core working surface to obtain blades and lamellar flakes. The second strategy is the alternating usage of the working surface and striking platform aimed at blank production. The reduction sequence is characterized by the usage of narrow surfaces bounded by natural sides. The third strategy is the bladelets and microblades production using one narrow or two adjacent (narrow and wide) working surfaces. The comparison of the material complex of the layer 5.1 with the complexes of layers 7–6 indicates principal differences in the raw material preferences, primary knapping methods and toolkits.Conclusion. Based on the lack of continuity of the primary knapping and the principles of spatial exploitation of Ushbulak site area, we suggest a complete change in the population of the Shilikta valley at the boundary of MIS 3 and MIS 2.

The use of slice encoding for metal artifact correction (SEMAC) sequencing improves the diagnostic evaluation of graft integrity following anterior cruciate ligament reconstruction

ObjectivesTo determine whether magnetic resonance imaging (MRI) with metal artifact reduction sequencing is superior to conventional knee MRI in the evaluation of an injured anterior cruciate ligament (ACL) graft, where visualisation on conventional MRI can be limited by the metal artifact from fixation devices. MethodsEighteen patients underwent conventional MRI sequence (proton density fat saturated [PDFS]) and two types of metal artifact reduction sequencing MRI (WARP, slice encoding for metal artifact correction (SEMAC); Siemens) following a secondary injury to their ACL reconstructed knee. Six raters with experience in knee MRI evaluation reviewed sagittal PDFS, WARP, and SEMAC sequences, providing semi-quantitative grades for visualisation and diagnostic confidence assessing the ACL, posterior cruciate ligament , menisci, tibial and femoral tunnel margins, and articular cartilage. Intra-class correlation coefficients for inter-rater reliability were evaluated. The 6-rater mean scores for the visualisation and diagnostic confidence derived from each sequence were compared using the Friedman test for multiple paired samples. ResultsNo statistically significant difference in the ACL visualisation among the sequences was found (p ​= ​0.193). Further, a subgroup analysis was performed in cases evaluated as “moderately blurry” or “indistinct ACL visualisation” on PDFS (58% of cases). SEMAC significantly improved diagnostic confidence in ACL visualisation (p ​= ​0.041) and ACL graft rupture (p ​= ​0.044) compared to PDFS.There was no statistically significant difference in the inter-observer reliability between sequences. The WARP sequence added 2.84 ​± ​0.69 ​min, while SEMAC added 2.95 ​± ​0.40 ​min to the standard knee MRI scan time. Conclusionuse of the SEMAC metal reduction sequence significantly improved diagnostic accuracy and confidence in the detection of ACL graft rupture in cases where the ACL was moderately blurry or indistinct on the PDFS sequence. This sequence should be considered as an adjunct to conventional PDFS in cases where graft visualisation is limited by the metal artifact from fixation devices. Level of evidenceIII.

Understanding passive film degradation and its effect on hydrogen embrittlement of super duplex stainless steel – Synchrotron X-ray and electrochemical measurements combined with CalPhaD and ab-initio computational studies

The passive film stability on stainless steel can be affected by hydrogen absorption and lead to microstructure embrittlement. This work shows that the absorption of hydrogen results in surface degradation due to oxide reduction and ionic defect generation within the passive film, which decomposes and eventually vanishes. The passive film provides a barrier to entering hydrogen, but when hydrogen is formed, atomic hydrogen infuses into the lattices of the austenite and ferrite phases, causing strain evolution, as shown by synchrotron x-ray diffraction data. The vacancy concentration and hence the strains increase with increasing electrochemical cathodic polarization. Under cathodic polarization, the surface oxides are thermodynamically unstable, but the complete reduction is kinetically restrained. As a result, surface oxides remain present under excessive cathodic polarization, contesting the classical assumption that oxides are easily removed. Density-functional theory calculations have shown that the degradation of the passive film is a reduction sequence of iron and chromium oxide, which causes thinning and change of the semiconductor properties of the passive film from n-type to p-type. As a result, the surface loses its passivity after long cathodic polarization and becomes only a weak barrier to hydrogen absorption and hence hydrogen embrittlement.

Synthesis of the Purported Structure of Glyphaeaside C and Proposed Revisions to the Structures of the Glyphaeaside Alkaloids.

The 10 glyphaeaside alkaloids isolated from the roots of Glyphaea brevis were originally purported as piperidine-based 1-C-alkylated iminosugars, with the A-, B-, and C-type glyphaeasides bearing l-DFJ, DGJ, and DNJ ring configurations, respectively. Subsequent investigations have revealed glyphaeaside C as being a pyrrolidine-based iminosugar with a DMDP ring configuration via total synthesis of the revised structure. In this work, side chain diastereomers of the originally purported structure of glyphaeaside C (10) and two related α-1-C-alkylated DNJ derivatives were synthesized from a common precursor, which was prepared in turn via stereoselective Grignard addition to a protected d-glycosylamine, followed by a reductive amination-cyclization sequence. Glycosidase inhibitory activity studies revealed general structure 10 as having potent inhibition against various α-glucosidases and weak inhibition against almond β-glucosidase in agreement with similar DNJ-based iminosugars and in contrast to natural glyphaeaside C, suggesting that the (1,2-dihydroxy-3-phenyl)propyl moiety does not play a particularly vital role in the inhibitory modes of action of either compound. Furthermore, the absolute configuration of natural glyphaeaside C was proposed as that of d-DMDP, and the structures of the A- and B-type glyphaeasides were revised as 1-deoxy-DALDP and DALDP derivatives, respectively, based on interpretation of their reported NMR spectroscopic data.

Prospective Evaluation of Magnetic Resonance Imaging Features of Magnesium-Based Alloy Screw Resorption in Pediatric Fractures.

The resorption of magnesium-based alloy bioabsorbable screws results in the release of hydrogen gas, which can mimic infection and enter the growth plate. The screw itself and the released gas may also affect image quality. The evaluation of magnetic resonance imaging (MRI) findings during the most active phase of screw resorption is the objective, with particular focus on the growth plate and to assess for the presence of metal-induced artifacts. In total, 30 prospectively acquired MRIs from 17 pediatric patients with fractures treated with magnesium screws were assessed for the presence and distribution of intraosseous, extraosseous, and intra-articular gas; gas within the growth plate; osteolysis along the screw; joint effusion; bone marrow edema; periosteal reaction; soft tissue edema; and metal-induced artifacts. Gas locules were found in the bone and soft tissues in 100% of the examinations, intra-articular in 40%, and in 37% of unfused growth plates. Osteolysis and the periosteal reaction were present in 87%, bone marrow edema in 100%, soft tissue edema in 100%, and joint effusion in 50% of examinations. Pile-up artifacts were present in 100%, and geometric distortion in 0% of examinations. Fat suppression was not significantly impaired in any examination. Gas and edema in the bone and soft tissues are normal findings during the resorption of magnesium screws and should not be misinterpreted as infection. Gas can also be detected within growth plates. MRI examinations can be performed without metal artifact reduction sequences. Standard fat suppression techniques are not significantly affected.

Synthesis of Aryl‐ and Alkyl‐Containing 3‐Methylene‐5‐hydroxy Esters via a Barbier Allylation Reaction

AbstractThe formation of C−C bonds via the allylation of carbonyl compounds has been widely applied in total syntheses. Amongst the many possible strategies, the Barbier‐type allylation in aqueous media has received only moderate attention over the last decades despite its mild reaction conditions. In this study, we investigated the indium (In0) and zinc (Zn0) mediated Barbier allylation reaction to efficiently synthesize base‐labile 3‐methylene‐5‐hydroxy containing building blocks for natural product total synthesis. As model study we selected the allylation of lipidic undecanal with ethyl 3‐(bromomethyl)but‐3‐enoate in the presence of either Zn0 or In0 and investigated the effects of additives on yields and selectivities. We then applied the optimized reaction conditions to sterically demanding allyl bromides and functionalized aromatic aldehydes yielding eleven new homoallylic alcohols, one of which was further transformed via oxidation and reduction sequences.

The Proceduralization of Hominin Knapping Skill: Memorizing Different Lithic Technologies

Reconstructing the technical and cognitive abilities of past hominins requires an understanding of how skills like stone toolmaking were learned and transmitted. We ask how much of the variability in the uptake of knapping skill is due to the characteristics of the knapping sequences themselves? Fundamental to skill acquisition is proceduralization, the process whereby skilful tasks are converted from declarative memories (consciously memorized facts and events) into procedural memories (sub-consciously memorized actions) via repetitive practice. From knapping footage, we time and encode each action involved in discoidal, handaxe, Levallois and prismatic blade production. The structure and complexity of these reduction sequences were quantified using k-mer analysis and Markov chains. The amount of time spent on tasks and the pattern of core rotations revealed portions of these reduction sequences that are predisposed to being converted into procedural memories. We observed two major pathways to achieve this proceduralization: either a repetitive or a predictable sequence of core rotations. Later Acheulean handaxes and Levallois knapping involved a predictable platform selection sequence, while prismatic blade knapping involved a repetitive exploitation of platforms. Technologies and the portions of their reduction sequence that lend themselves to proceduralization probably facilitated the more rapid uptake of stone toolmaking skill.

Variability in Silcrete Heat Treatment at Klein Kliphuis Shelter, South Africa, and Its Role in Core Reduction

ABSTRACT Silcrete heat treatment was the earliest known transformative process enhancing the mechanical properties of materials. Its study has implications for our understanding of the cultural evolution of early humans in the Middle Stone Age and southern Africa. Here, we analyze a silcrete assemblage from the South African site Klein Kliphuis. We first investigate the relative prevalence of heat treatment in assemblage and then the position of heat treatment within reduction sequences. We found that ∼60% of all silcrete was heat-treated prior to knapping in one post-Howiesons Poort assemblage and ∼85% in two Howiesons Poort assemblages. However, heat treatment early-on was not the only strategy present in the site. Late-stage heat treatment was occasionally deployed to extend the utility of small cores. This finding emphasizes the ability of early anatomically modern humans in Africa to adapt their tool making behavior to changing economic conditions related to raw materials quality and availability.

Assessing osteonecrosis of the femoral head after internal fixation of femoral neck fractures in young patients with fixation implants in situ: the value of MARS MRI in relation to conventional radiography and patient-reported outcomes

Little is known on the use of metal artifact reduction sequence (MARS) MRI to diagnose osteonecrosis of the femoral head (ONFH) after fixation of femoral neck fractures (FNF) with conventional metal implants present. We compared MARS MRI with radiography in diagnosing ONFH. Secondarily, we determined whether signs of ONFH on MARS MRI correlate with patient-reported outcomes (PROs) via Oxford Hip Score (OHS) and pain (VAS). 30 adults under 60 years treated with internal fixation after FNF were prospectively included (2015-2018) at 2 hospitals. They were followed up with radiography and PROs at 4, 12, and 24 months and MARS MRI at 4 and 12 months. OHS < 34 or VAS pain > 20 was considered significant. At 12 months, 14 patients had a pathological MRI. 3 of 14 had ONFH on radiographs at 12 months, increasing to 5 at 24 months, and 4 had unfavorable PROs. 2 of 5 patients with ONFH signs on both MRI and radiography had unfavorable PROs. 1 of 10 patients with normal MRI and radiography had unfavorable 2-year PROs. 4 patients had inconsistent MRI results, of which 1 developed ONFH. 1 patient dropped out. Information from a pathological MRI was not useful, as a majority remained free from symptoms and ONFH signs on radiographs. Furthermore, PROs did not correlate with imaging results. MARS MRI findings must be better understood before being taken into clinical practice. However, a normal MARS MRI seems to be a good prognostic finding.

A strong call-by-need calculus

We present a call-by-need $\lambda$-calculus that enables strong reduction (that is, reduction inside the body of abstractions) and guarantees that arguments are only evaluated if needed and at most once. This calculus uses explicit substitutions and subsumes the existing strong-call-by-need strategy, but allows for more reduction sequences, and often shorter ones, while preserving the neededness. The calculus is shown to be normalizing in a strong sense: Whenever a $\lambda$-term t admits a normal form n in the $\lambda$-calculus, then any reduction sequence from t in the calculus eventually reaches a representative of the normal form n. We also exhibit a restriction of this calculus that has the diamond property and that only performs reduction sequences of minimal length, which makes it systematically better than the existing strategy. We have used the Abella proof assistant to formalize part of this calculus, and discuss how this experiment affected its design. In particular, it led us to derive a new description of call-by-need reduction based on inductive rules.

Rapid Total Synthesis of Iheyamine A via a Pictet–Spengler/Redox-Mediated Cyclization Cascade

The Pictet-Spengler reaction between tryptamine and (5-methoxy-2-nitrophenyl)-glyoxal in hot AcOH could trigger a redox-mediated cyclization and reduction sequence to form iheyamine A in 52% yield.

Scheduling Musculoskeletal MRI for Patients With Metallic Hardware: Initial Observations on Decreasing Nondiagnostic and Repeat Examinations at a Multisite Academic Medical Center

As healthcare delivery systems expand to include multiple imaging centers, the process of scheduling patients at the site which best meets their needs continues to become more complex. This quality improvement study aims to create a protocol for patients with metallic hardware at sites with metallic artifact reduction sequences (MARS), increasing the proportion of exams that are diagnostic and reducing the need for repeat imaging. The study population included 322 patients with metallic hardware receiving an MRI at a large multisite healthcare system, divided into a pre-intervention and postintervention cohort. A retrospective PACS query was performed using several keywords in musculoskeletal MRI reports indicating the presence of metallic hardware. This cohort was studied to better understand the existing system failures. An intervention was then implemented by meeting with the departmental RIS and scheduling teams to discuss workflow when scheduling exams for patients with metallic hardware System changes were implemented and results were again studied retrospectively. Before protocol implementation, 134/244 (55%) of exams were performed at sites with metallic artifact reduction sequences which improved to 54 of 78 (69%) in the postintervention cohort (P=0.02). Additionally, the number of exams performed on 3T MRI machines pre-intervention was 14 of 244 (5.7%) compared to 1 of 78 (1.2%) postintervention (P=0.13). The rate of nondiagnostic exams in the preintervention cohort was significantly higher at 41 of 244 (16.8%) when compared to the postintervention cohort at 4 of 78 (5.1% P=0.01). The implementation of this quality improvement protocol reduced the rate of nondiagnostic MSK MRI exams and reduced the inappropriate use of 3T scanners, ultimately saving time and cost for both patients and the health care system.

Early Upper Paleolithic cultural variability in the Southern Levant: New evidence from Nahal Rahaf 2 Rockshelter, Judean Desert, Israel

The Levantine Early Upper Paleolithic (ca. 45–30 ka) has been a focus of research because of its unique position as a conduit of human, flora, and fauna species between Africa and Eurasia. Studies have mainly focused on the Early Ahmarian and Levantine Aurignacian, two entities, the former endemic and the latter foreign, which are considered to have coinhabited the region during that period. However, other cultural entities, such as the Atlitian in the Mediterranean region and the Arkov-Divshon in the arid regions of the southern Levant received less attention, and accordingly, suffer from broad definitions and chronological insecurity. These cultures hold potential insights regarding nuanced adaptations, reciprocal influences, and diachronic assimilation processes. The recently discovered site of Nahal Rahaf 2 Rockshelter in the Judean Desert provides integral information on one of these entities—the Arkov-Divshon. Two excavation seasons revealed a sequence of archaeological layers, with lithic assemblages in which laterally carinated items were prominent. Alongside rich faunal assemblages, other components of the material culture include perforated marine shells and bone tools, marking the first association of these elements with Arkov-Divshon and implying some degree of contact with the Mediterranean regions of the Levant. Good preservation of organic materials allowed radiocarbon dating of the human occupation at the site to ca. 37.5–34.0 ka cal BP, indicating chronological overlap with the Levantine Aurignacian, and possibly also with the latest phases of the Early Ahmarian. Thus, challenging the validity of the widely accepted ‘Two Tradition’ Model of the Levantine Upper Paleolithic. Lithic analyses suggest the use of one main reduction sequence and the primary production of bladelets from carinated items. Faunal remains suggest targeted hunting of ibex and gazelle. Botanical remains and sedimentary analyses suggest roughly similar environmental conditions, with a possible woodier environment in the surroundings of the site.

Identification of protective and 'at risk' HLA genotypes for the development of pseudotumours around metal-on-metal hip resurfacings.

Hip resurfacing remains a potentially valuable surgical procedure for appropriately-selected patients with optimised implant choices. However, concern regarding high early failure rates continues to undermine confidence in use. A large contributor to failure is adverse local tissue reactions around metal-on-metal (MoM) bearing surfaces. Such phenomena have been well-explored around MoM total hip arthroplasties, but comparable data in equivalent hip resurfacing procedures is lacking. In order to define genetic predisposition, we performed a case-control study investigating the role of human leucocyte antigen (HLA) genotype in the development of pseudotumours around MoM hip resurfacings. A matched case-control study was performed using the prospectively-collected database at the host institution. In all, 16 MoM hip resurfacing 'cases' were identified as having symptomatic periprosthetic pseudotumours on preoperative metal artefact reduction sequence (MARS) MRI, and were subsequently histologically confirmed as high-grade aseptic lymphocyte-dominated vasculitis-associated lesions (ALVALs) at revision surgery. 'Controls' were matched by implant type in the absence of evidence of pseudotumour. Blood samples from all cases and controls were collected prospectively for high resolution genetic a nalysis targeting 11 separate HLA loci. Statistical significance was set at 0.10 a priori to determine the association between HLA genotype and pseudotumour formation, given the small sample size. Using a previously-reported ALVAL classification, the majority of pseudotumour-positive caseswere found to have intermediate-grade group 2 (n = 10; 63%) or group 3 (n = 4; 25%) histological findings. Two further patients (13%) had high-grade group 4 lesions. HLA-DQB1*05:03:01 (p = 0.0676) and HLA-DRB1*14:54:01 (p = 0.0676) alleles were significantly associated with a higher risk of pseudotumour formation, while HLA-DQA1*03:01:01 (p = 0.0240), HLA-DRB1*04:04:01 (p = 0.0453), HLA-C*01:02:01 (p = 0.0453), and HLA-B*27:05:02 (p = 0.0855) were noted to confer risk reduction. These findings confirm the association between specific HLA genotypes and the risk of pseudotumour development around MoM hip resurfacings. Specifically, the two 'at risk' alleles (DQB1*05:03:01 and DRB1*14:54:01) may hold clinical value in preoperative screening and prospective surgical decision-making.

Optimization of Partial Transmit Sequences for PAPR Reduction of OFDM Signals Without Side Information

This paper develops a novel optimization of partial transmit sequences (PTS) with phase quantization to reduce the peak-to-average-power ratio (PAPR) of orthogonal frequency-division multiplexing (OFDM) signals and enable data detection without side information. Since the formulated optimization problem is non-convex and has exponential time complexity, we employ a convex relaxation method to convert the original optimization problem into a series of convex programming whose solutions converge to a sub-optimal point satisfying the Karush-Kuhn-Tucker (KKT) conditions in polynomial time. Moreover, the obtained phase factors are quantized to enable the maximum likelihood (ML) phase estimation at the receiver, hence removing the need of sending side information. Analytical and numerical results are provided to show that our proposed PTS design achieves better PAPR reduction over existing PTS methods, while no performance degradation is incurred in data detection when the number of phase factors is properly chosen.

The anatomical location of cystic pseudotumors and muscle atrophy in metal-on-metal resurfacing hip arthroplasty is related to the surgical approach used for implantation. A subgroup analyses of a randomized controlled trial.

Pseudotumors and muscle atrophy have been associated with metal-on-metal (MoM) resurfacing hip arthroplasty (RHA). We aimed to investigate the influence of the anterolateral (AntLat) and the posterior (Post) surgical approach on the location, grade and prevalence of pseudotumors and muscle atrophy in MoM RHA. Forty-nine patients were randomized to MoM RHA by the AntLat (n = 25) or the Post (n = 24) approach at Aarhus University Hospital. Patients underwent metal artifact reduction sequence (MARS) magnetic resonance imaging (MRI) scans for investigation of location, grade and prevalence of pseudotumors and muscle atrophy. Plain radiographs, metal-ions concentrations and clinical outcome scores were evaluated to compare outcomes of the surgical approaches. MRI-detected pseudotumors were seen in 7 of 18 patients (39%) in the AntLat group and in 12 of 22 patients (55%) in the Post group (p = 0.33). Pseudotumors were mainly located anterolaterally to the hip joint in the AntLat group and postero-lateral to the hip joint in the Post group. Higher grades of muscle atrophy of the caudal part of the gluteus medius and minimus (p < 0.004) were seen in the AntLat group, and higher grades of muscle atrophy of the small external rotators were seen in the Post group (p < 0.001). The AntLat group had higher anteversion angles of mean 15.3° (range 6.1-7.5) versus mean 11.5° (range 4.9-22.5) in the Post group (p = 0.02). Metal-ion concentrations and clinical outcome scores were similar between groups (p > 0.08). Muscle atrophy and pseudotumor location after MoM RHA follow the surgical approach used for implantation. This knowledge may help differentiate between "normal postoperative appearance" and "MoM disease."

An integrated approach to reconstruct the role of the heat treatment within the reduction sequence of chert artefacts: The case of the early Neolithic site of Lugo di Grezzana (north‐eastern Italy)

AbstractThe lithic assemblage from the well‐known site of Lugo di Grezzana (Italy) attributable to the Fiorano group (5,300–4,900 BC cal) is analysed to shed new insights on the early Neolithic lithic technology in North‐Eastern Italy. Techno‐typological data are discussed allowing detailed reconstruction of the reduction sequence, thanks also to several refittings. A complex laminar production with several technical objectives has been identified. Whereas clues for the heat treatment of lithic materials have been identified, we verified it by a combined experimental approach. In the first place, we used density measurements, which already proved to be useful for prescreening analysis, to detect potentially heated artefacts. Afterward, we performed Fourier Transform Infrared (FT‐IR) spectroscopy tests to assess the actual (de)hydration condition of the siliceous materials. Reflectance spectra have been acquired, analysing any item and avoiding any constraint related to both morphology and thickness of the sample. The archaeometric results, combined with the reduction sequence reconstruction, provide new indications on the technical capabilities and knowledge of the human groups that inhabited the region during the early Neolithic.

Stable Silapyramidanes

Starting from tetrakis(trimethylsilyl)cyclobutadiene and an amidinate-supported silylene of the Roesky-type, a sequence of addition and reduction cleanly gives the elusive silapyramidane via an isolable cyclobutene intermediate with an exocyclic Si═C bond. The silapyramidane features an unusually shielded 29Si NMR resonance at -448.3 ppm for the apex silicon atom. Treatment with Fe2(CO)9 results in the formation of the corresponding silapyramidane-iron complex. Silapyramidane also reacts with the cyclobutadiene starting material to cleanly afford a fluorescent spirobis(silole).

Sensitivity and specificity for detecting pseudotumors in patients with hip resurfacing arthroplasty, metal-on-metal or metal-on-polyethylene total hip arthroplasty-MRI versus ultrasonography performed by an orthopedic surgery resident.

Metal artifact reduction sequence magnetic resonance imaging (MRI) scan is a common method to detect adverse reaction to metal debris in total hip arthroplasty (THA). It might be quicker and cheaper if ultrasonography (US) could screen for the need for an MRI. However, both require trained personnel. We aimed to investigate the sensitivity and specificity of US for detecting pseudotumors (PT) when performed by an orthopedic surgery resident compared to MRI. We also investigated the sensitivity and specificity of US to detect PTs in obese and non-obese patients. We examined 205 patients with hip resurfacing arthroplasty, metal-on-metal or metal-on-polyethylene THA with both MRI and US. US was performed by an orthopedic surgery resident who was trained according to a standardized training program in musculoskeletal US. Results from MRI were used as gold standard. US had a sensitivity of 0.92 (95% CI 0.81-0.98) and specificity of 0.94 (95% CI 0.89-0.97) for detecting PT. It had a positive predictive value of 0.84 (95% CI 0.73-0.91) and a negative predictive value of 0.97 (95% CI 0.93-0.99). US performed similarly in obese and non-obese patients. US had a high sensitivity and specificity for detecting PT when performed by an orthopedic surgery resident. Trained orthopedic surgeons could screen for the need of an MRI scan when searching PTs.