The Ideal Timing of Bilateral Total Knee Arthroplasty: Simultaneous Versus Staged.

Objectives: The ideal timing for patients undergoing bilateral total knee arthroplasty (TKA) remains unknown. The purpose of this study was to compare 90-day outcomes between unilateral, simultaneous bilateral, and staged bilateral TKA. Methods: The PearlDiver database was used to retrospectively identify 231,119 patients undergoing primary TKA during 2015-2020, of which 67,956 (29.4%) were bilateral. Bilateral TKA patients were divided into cohorts of simultaneous bilateral TKA and staged bilateral TKA at 1-14 days, 15-30 days, 31-90 days, and 91-365 days. Each bilateral TKA cohort underwent one-to-one matching with unilateral TKA patients based on age, gender, year, Elixhauser Comorbidity Index (ECI), and a history of obesity, diabetes, and tobacco use. Ninety-day outcomes were compared between matched groups via univariate and multivariate analysis. In staged bilateral TKA groups, outcomes were collected beginning after the second TKA. Results: Compared to unilateral TKA, simultaneous bilateral TKA was associated with higher rates of venous thromboembolism (VTE; odds ratio [OR] 1.28, 95% confidence interval [CI] 1.07-1.54, p=0.007), acute kidney injury (AKI; OR 1.47, CI 1.17-1.84, p=0.001), blood transfusion (OR 6.81, CI 5.43-8.65, p<0.001), and any complication (OR 1.63, CI 1.49-1.78, p<0.001). Staged bilateral TKA at any time interval studied was associated with a similar or decreased risk of individual complications, emergency department visits, readmissions, reoperations, and any complication relative to unilateral TKA. Conclusion: Simultaneous bilateral TKA is associated with an increased risk of adverse events compared to unilateral TKA. However, bilateral TKA staged at a short interval appears safe in appropriately selected patients.

Fretting and Tribocorrosion of Modular Dual Mobility Liners: Role of Design, Microstructure, and Malseating.

BACKGROUND: Modular dual mobility (DM) bearings have a junction between a cobalt chrome alloy (CoCrMo) liner and titanium shell, and the risk of tribocorrosion at this interface remains a concern. The purpose of this study was to determine whether liner malseating and liner designs are associated with taper tribocorrosion. METHODS: We evaluated 28 retrieved modular DM implants with a mean in situ duration of 14.6 months (range, 1 to 83). There were two manufacturers included (12 and 16 liners, respectively). Liners were considered malseated if a distinct divergence between the liner and shell was present on postoperative radiographs. Tribocorrosion was analyzed qualitatively with the modified Goldberg Score (mGS) and quantitatively with an optical coordinate-measuring machine. An acetabular shell per manufacturer was sectioned for metallographic analysis. RESULTS: There were six implants (22%) that had severe grade 4 corrosion, six (22%) had moderate grade 3, 11 (41%) had mild grade 2, and five (18.5%) had grade 1 or no visible corrosion. The average volumetric material loss at the taper was 0.086 ± 0.19 mm3. There were seven liners (25%) that had radiographic evidence of malseating, and all were of a single design (P = 0.01). The two liner designs were fundamentally different from one another with respect to the CoCrMo alloy type, taper surface finish, and shape deviations. Malseating was an independent risk factor for increased volumetric material loss (P = 0.017). CONCLUSION: Dual mobility tribocorrosion with quantifiable material loss occurred more commonly in malseated liners. Specific design characteristics may make liners more prone to malseating, and the interplay between seating mechanics, liner characteristics, and patient factors likely contributes to the shell/liner tribocorrosion environment.

Proposal for a classification system of radiographic bone changes after cervical disc replacement.

BACKGROUND: The goal of this study is to propose a classification system with a common nomenclature for radiographic observations of periprosthetic bone changes following cTDR. METHODS: Aided by serial plain radiographs from recent cTDR cases (34 patients; 44 devices), a panel of experts assembled for the purpose of creating a classification system to aid in reproducibly and accurately identifying bony changes and assessing cTDR radiographic appearance. Subdividing the superior and inferior vertebral bodies into 3 equal sections, observed bone loss such as endplate rounding, cystic erosion adjacent to the endplate, and cystic erosion not adjacent to the endplate, is recorded. Determining if bone loss is progressive, based on serial radiographs, and estimating severity of bone loss (measured by the percentage of end plate involved) is recorded. Additional relevant bony changes and device observations include radiolucent lines, heterotopic ossification, vertebral body olisthesis, loss of core implant height, and presence of device migration, and subsidence. RESULTS: Serial radiographs from 19 patients (25 devices) implanted with a variety of cTDR designs were assessed by 6 investigators including clinicians and scientists experienced in cTDR or appendicular skeleton joint replacement. The overall agreement of assessments ranged from 49.9% (95% bootstrap confidence interval 45.1-73.1%) to 94.7% (95% CI 86.9-100.0%). There was reasonable agreement on the presence or absence of bone loss or radiolucencies (range: 58.4% (95% CI 51.5-82.7%) to 94.7% (95% CI 86.9-100.0%), as well as in the progression of radiolucent lines (82.9% (95% CI 74.4-96.5%)). CONCLUSIONS: The novel classification system proposed demonstrated good concordance among experienced investigators in this field and represents a useful advancement for improving reporting in cTDR studies.

Presentation and management of infection in total disc replacement: A review.

Background: Total disc replacement (TDR) is widely used in the treatment of cervical and lumbar spine pathologies. Although TDR infection, particularly delayed infection, is uncommon, the results can be devastating, and consensus on clinical management remains elusive. In this review of the literature, we asked: (1) What are the reported rates of TDR infection; (2) What are the clinical characteristics of TDR infection; and (3) How has infection been managed for TDR patients? Methods: We performed a search of the literature using PubMed and Embase to identify studies that reported TDR infection rates, the identification and management of TDR infection, or TDR failures with positive cultures. Twenty database studies (17 focusing on the cervical spine and 3 on the lumbar spine) and 10 case reports representing 15 patients were reviewed along with device Summary of Safety and Effectiveness Data reports. Results: We found a lack of clarity regarding how infection was diagnosed, indicating a variation in clinical approach and highlighting the need for a standard definition of TDR infection. Furthermore, while reported infection rates were low, the absence of a clear definition prevented robust data analysis and may contribute to underreporting in the literature. We found that treatment strategy and success rely on several factors including patient symptoms and time to onset, microorganism type, and implant positioning/stability. Conclusions: Although treatment strategies varied throughout the extant literature, common practices in eliminating infection and reconstructing the spine emerged. The results will inform future work on the creation of a more robust definition of TDR infection and as well as recommendations for management.

Establishing clinically meaningful ranges of metal hypersensitivity in orthopaedic patients using COVID-19 vaccine-induced adaptive immune responses from fully vaccinated adults.

Background: This study aimed to assess metal sensitization ranges among orthopaedic patients by comparing adaptive immune responses in all-comer pre- and post-operative orthopaedic adults who were COVID-19 unvaccinated or vaccinated vs patients with a painful aseptic implant by lymphocyte transformation test (LTT) to SARS-CoV-2-Spike-Protein (SP) and implant metal(s), respectively. Methods: Data were retrospectively reviewed from three independent groups: unvaccinated COVID-19 adults (n = 23); fully COVID-19 vaccinated adults (n = 35); unvaccinated, painful aseptic implant patients with history of metal allergy (n = 98). Standard in vitro LTT for SP and implant metal(s) (nickel, cobalt) were performed and rated as negative (stimulation index [SI]<2), mild (SI ≥ 2), positive (SI ≥ 4-15), and high sensitization (SI > 15) adaptive immune responses to tested antigen. Results: Overall, 17/23 (74%) of unvaccinated adults showed negative to mild LTT ranges, and 35/35 (100%) of vaccinated showed mild to positive LTT ranges to SP. Vaccinated individuals showed significantly higher median SI (16.1) to SP than unvaccinated (median SI, 1.7; P < 0.0001). Most vaccinated adults (94%) showed a lymphocyte SI > 4 to SP, establishing LTT SI ≥ 4 with >90% sensitivity for diagnosing effective COVID-19 adaptive immune responses. Significantly fewer painful orthopaedic patients (41%) showed comparable elevated levels of lymphocyte metal sensitivity at SI ≥ 4 compared to vaccinated group (P < 0.0001). Conclusions: Vaccinated adults showed significantly higher lymphocyte SI to SP than unvaccinated indicating that SI ranges ≥4 should be set as unequivocally diagnostic of LTT-positive adaptive immune responses to tested antigen. This analysis supports using higher LTT SI ranges (SI ≥ 4) in diagnosing clinical orthopaedic-related Type IV metal-hypersensitivity responses among orthopaedic patients.

Management of Femoral Neck Fractures in Patients Age ≥50 Years by American Board of Orthopaedic Surgery Part II Examination Candidates.

OBJECTIVE: Assess associations between fellowship training, procedure, and performance in femoral neck fracture (FNF) surgery on adults by American Board of Orthopaedic Surgery (ABOS) Part II Examination candidates. SETTING: ABOS SCRIBE database exam years 2007-2020. PARTICIPANTS: 6,777 candidates performing 39,283 FNF surgeries on adults age ≥ 50 years. INTERVENTION: Fellowship training. MAIN OUTCOME MEASUREMENTS: Case volume; procedure performed: internal fixation (IF), hemiarthroplasty (HA), or total hip arthroplasty (THA); complications; readmission; reoperation. RESULTS: Over the observation period, fewer candidates reported FNF surgery (68% overall, -0.6%/year, R2=0.80) while more candidates reported fellowship training (87% overall, +1.4%/year, R2=0.81). The rate of any complication was significantly associated with fellowship training (32% overall, p<0.001). Readmission (12%, p=0.080) and reoperation (5%, p=0.531) were not significantly associated with fellowship training. The odds of any complication (odds ratio [OR]=-0.03 [95% CI -0.07 to -0.001] per 10 cases) and surgical complication (OR=-0.12 [95% CI -0.17 to -0.07] per 10 cases) were negatively associated with candidate FNF case volume. 3,396 THA for FNF were performed (8% of cases). THA use increased 25 cases/year (R2=0.83) and was associated with adult reconstruction (p<0.001) and oncology (p<0.001) fellowship training. Any complication of THA for FNF (32%, p=0.261), readmission (9% overall, p=0.321), and reoperation (5%, p=0.200) were not significantly associated with fellowship training. CONCLUSIONS: Between 2007-2020, femoral neck fracture surgery was performed by fewer ABOS Part II Examination candidates and there was greater use of THA. Over this time period there was a greater prevalence of fellowship training but complications were not associated with fellowship training. Complications were associated with FNF case volume. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Has Wrought Cobalt-Chromium-Molybdenum Alloy Changed for the Worse Over Time?

BACKGROUND: Total hip arthroplasty (THA) failure due to tribocorrosion of modular junctions and resulting adverse local tissue reactions to corrosion debris have seemingly increased over the past few decades. Recent studies have found that chemically-induced column damage seen on the inner head taper is enabled by banding in the alloy microstructure of wrought cobalt-chromium-molybdenum alloy femoral heads, and is associated with more material loss than other tribocorrosion processes. It is unclear if alloy banding represents a recent phenomenon. The purpose of this study was to examine THAs implanted in the 1990s, 2000s, and 2010s to determine if alloy microstructure and implant susceptibility to severe damage has increased over time. METHODS: Five hundred and forty-five modular heads were assessed for damage severity and grouped based on decade of implantation to serve as a proxy measure for manufacturing date. A subset of heads (n = 120) was then processed for metallographic analysis to visualize alloy banding. RESULTS: We found that damage score distribution was consistent over the time periods, but the incidence of column damage significantly increased between the 1990s and 2000s. Banding also increased from the 1990s to 2000s, but both column damage and banding levels appear to recover slightly in the 2010s. CONCLUSION: Banding, which provides preferential corrosion sites enabling column damage, has increased over the last 3 decades. No difference between manufacturers was seen, which may be explained by shared suppliers of bar stock material. These findings are important as banding can be avoidable, reducing the risk of severe column damage to THA modular junctions and failure due to adverse local tissue reactions.

Microstructure and electrochemical behavior of contemporary Ti6Al4V implant alloys.

Ti6Al4V is the most common titanium alloy within the biomaterial field. While material standards for different variations of this alloy exist, there are only minimal requirements with respect to its microstructure which is directly related to the alloy's properties. Thus, a better understanding of the Ti6Al4V microstructure of common contemporary implant components and its effect on the electrochemical behavior is needed; including additively manufactured (AM) devices. Therefore, this study aimed at characterizing the microstructures of conventional and AM total joint replacement components, and to identify the effect of microstructure on the electrochemical behavior. Thus, 22 components from conventional (surgically retrieved cast and wrought implants) and AM implants (not previously implanted) were analysed to characterize microstructure by means of electron backscatter diffraction (EBSD) and energy dispersive X-Ray spectroscopy (EDS), and tested to determine its electrochemical behavior (potentiodynamic polarization and EIS). The microstructure of the conventional implants varied broadly but could be categorized into four groups as to their grain size and shape: fine equiaxed, coarse equiaxed, bimodal, and lamellar. The AM components exhibited a fifth category: lath-type. The AM components had a network of ß-phase along the α-phase grain boundaries, prior ß-grains, and manufacturing voids. Finally, the electrochemical study showed that the equiaxed coarse grains and lath-type grains (AM components) had inferior electrochemical behavior, whereas cast alloys had superior electrochemical behaviour; fine-grained wrought alloys likely provide the best compromise between electrochemical and mechanical properties.

Non-ischaemic cardiomyopathy associated with elevated serum cobalt and accelerated wear of a metal-on-metal hip resurfacing.

A man in his late 30s developed non-ischaemic cardiomyopathy due to systemic cobalt toxicity associated with accelerated bearing surface wear from metal-on-metal hip resurfacing implanted in the previous 6 years. Following revision arthroplasty, the patient regained baseline cardiac function. Cobalt-induced cardiomyopathy is a grave condition that deserves early consideration due to potentially irreversible morbidity. We present this case to increase awareness, facilitate early detection and emphasise the need for research into the diagnosis and management of at-risk patients.

Optimal surgical component alignment minimizes TKR wear - An in silico study with nine alignment parameters.

Currently, preclinical mechanical wear testing of total knee replacements (TKRs) is done using ideally aligned components using standardized TKR level walking under either force or displacement-control regimes. To understand the influence of implant alignment and testing control regime, we studied the effect of nine component alignment parameters on TKR volumetric wear in silico. We used a computational framework combining Latin Hypercube sampling design of experiments, finite element analysis, and a numerical model of polyethylene wear, to create a predictive model of how component alignment affects wear rate for each control regime. Nine component alignment parameters were investigated, five femoral variables and four tibial variables. To investigate perturbations of the nine implant alignment variables, two separate 300-point designs were executed, one for each control regime. The results were then used to generate surrogate statistical models using stepwise multiple linear regression. Wear at the neutral position was 4.5mm3/million cycle and 8.6mm3/million cycle for displacement and force-control, respectively. Stepwise multiple linear regression surrogate models were highly significant for each control regime, but force-control generated a stronger predictive model, with a higher R2, more included terms, and a lower RMSE. Both models predicted transverse plane rotational mismatch can lead to large changes in predicted wear; a transverse plane alignment mismatch of 15° can elicit a change in wear of up to 5mm3/million cycle, almost double that of neutral alignment. Therefore, transverse plane alignment is particularly important when considering failure of the implant due to wear.

Methods for intratumoral microdialysis probe targeting and validation in murine brain tumor models.

BACKGROUND: Microdialysis is a well validated sampling technique that can be used for pharmacokinetic studies of oncological drugs targeting the central nervous system. This technique has also been applied to evaluate tumor metabolism and identify pharmacodynamic biomarkers of drug activity. Despite the potential utility of microdialysis for therapeutic discovery, variability in tumor size and location hamper routine use of microdialysis as a preclinical tool. Quantitative validation of microdialysis membrane location relative to radiographically evident tumor regions could facilitate rigorous preclinical studies. However, a widely accessible standardized workflow for preclinical catheter placement and validation is needed. NEW METHOD: We provide methods for a workflow to yield tailored placement of microdialysis probes within a murine intracranial tumor and illustrate in an IDH1-mutant patient-derived xenograft (PDX) model. This detailed workflow uses a freely available on-line tool built within 3D-slicer freeware to target microdialysis probe placement within the tumor core and validate probe placement fully within the tumor. RESULTS: We illustrate use of this workflow to validate microdialysis probe location relative to implanted IDH1-mutant PDXs, using the microdialysis probes to quantify levels of extracellular onco-metabolite D-2 hydroxyglutarate. COMPARISON WITH EXISTING METHODS: Previous methods have used 3D slicer to reliably measure tumor volumes. Prior microdialysis studies have targeted expected tumor locations without validation. CONCLUSIONS: The new method offers a streamlined and freely available workflow in 3D slicer to optimize and validate microdialysis probe placement within a murine brain tumor.

The role of Vitamin E in hip implant-related corrosion and toxicity: Initial outcome.

In orthopedic healthcare, Total Hip Replacement (THR) is a common and effective solution to hip-related bone and joint diseases/fracture; however, corrosion of the hip implant and the release of degradation metal ions/particles can lead to early implant failure and pose potential toxicity risk for the surrounding tissues. The main objective of this work was to investigate the potential role of Vitamin E to minimize corrosion-related concerns from CoCrMo hip implants. The study focused on two questions (i) Can Vitamin E inhibit CoCrMo corrosion? and (ii) Does Vitamin E moderate the toxicity associated with the CoCrMo implant particles? In the study (i) the electrochemical experiments (ASTM G61) with different concentrations of Vitamin E (1, 2, 3 mg/ml against the control) were performed using normal saline and simulated synovial fluid (Bovine calf serum-BCS, 30 g/L protein, pH 7.4) as electrolytes. The polished CoCrMo disc (Ra 50 nm) was the working electrode. The findings suggested that both Vitamin E-Saline (45 ± 0.9%) and Vitamin E-BCS (91 ± 3%) solutions protected against implant corrosion at a Vitamin E concentration of 3 mg/ml, but Vitamin E-BCS showed protection at all Vitamin E (1-3 mg/ml) concentration levels. These results suggested that the Vitamin E and the protein present in the BCS imparted additive effects towards the electrochemical inhibition. In the study (ii) the role of Vitamin E in cytotoxicity inhibition was studied using a mouse neuroblastoma cell line (N2a) for CoCrMo particles and Cr ions separately. The CoCrMo particles were generated from a custom-built hip simulator. The alamarBlue assay results suggested that Vitamin E provides significant protection (85% and 75% proliferation) to N2a cells against CoCrMo particles and Cr ions, respectively at 1 µg/ml concentration, as compared to the control group. However, the results obtained from ROS expression and DNA fiber staining suggest that Vitamin E is only effective against CoCrMo degradation particles and not against Cr ions. In summary, the findings show that Vitamin E can minimize the corrosion processes and play a role in minimizing the potential toxicity associated with implants.

COVID-19 (SARS-CoV-2) lymphocyte responses are associated with inflammatory biomarkers in total joint replacement surgery candidates pre-operatively.

BACKGROUND: Recent studies indicate that, in addition to antibody production, lymphocyte responses to SARS-CoV-2 may play an important role in protective immunity to COVID-19 and a percentage of the general population may exhibit lymphocyte memory due to unknown/asymptomatic exposure to SARS-CoV-2 or cross-reactivity to other more common coronaviruses pre-vaccination. Total joint replacement (TJR) candidates returning to elective surgeries (median age 68 years) may exhibit similar lymphocyte and/or antibody protection to COVID-19 prior to vaccination METHODS: In this retrospective study, we analyzed antibody titters, lymphocyte memory, and inflammatory biomarkers specific for the Spike and Nucleocapsid proteins of the SARS-CoV-2 virus in a cohort of n=73 returning TJR candidates (knees and/or hips) pre-operatively. RESULTS: Peripheral blood serum of TJR candidate patients exhibited a positivity rate of 18.4% and 4% for IgG antibodies specific for SARS-CoV-2 nucleocapsid and spike proteins, respectively. 13.5% of TJR candidates exhibited positive lymphocyte reactivity (SI > 2) to the SARS-CoV-2 nucleocapsid protein and 38% to the spike protein. SARS-CoV-2 reactive lymphocytes exhibited a higher production of inflammatory biomarkers (i.e., IL-1ß, IL-6, TNFα, and IL-1RA) compared to non-reactive lymphocytes. CONCLUSIONS: A percentage of TJR candidates returning for elective surgeries exhibit pre-vaccination positive SARS-CoV-2 antibodies and T cell memory responses with associated pro-inflammatory biomarkers. This is an important parameter for understanding immunity, risk profiles, and may aid pre-operative planning. TRIAL REGISTRATION: Retrospectively registered.

Early outcomes of a modern cemented total knee arthroplasty : is tibial loosening a concern?

AIMS: Recent total knee arthroplasty (TKA) designs have featured more anatomical morphologies and shorter tibial keels. However, several reports have raised concerns about the impact of these modifications on implant longevity. The aim of this study was to report the early performance of a modern, cemented TKA design. METHODS: All patients who received a primary, cemented TKA between 2012 and 2017 with a minimum two-year follow-up were included. The implant investigated features an asymmetrical tibial baseplate and shortened keel. Patient demographic details, Knee Society Scores (KSS), component alignment, and the presence of radiolucent lines at final follow-up were recorded. Kaplan-Meier analyses were performed to estimate survivorship. RESULTS: A total of 720 of 754 primary TKAs (95.5%) were included with a mean follow-up of 3.9 years (SD 1.3); 562 (78.1%) were cruciate-retaining and 158 (21.9%) were posterior-stabilized. A total of 11 (1.5%) required reoperation for periprosthetic joint infection and seven (1.0%) for aseptic tibial loosening (five cruciate-retaining, two posterior-stabilized). Loosening occurred at a mean of 3.3 years (0.9 to 6.5). There were no cases of loosening in the 33 patients who received a 14 mm × 30 mm tibial stem extension. All-cause survivorship was 96.6% at three years (95% confidence interval (CI) 95.3% to 98.0%) and 96.2% at five years (95% CI 94.8% to 97.7%). Survivorship with revision for aseptic loosening was 99.6% at three years (95% CI 99.1% to 100.0%) and 99.1% at five years (95% CI 98.4% to 99.9%). Tibial components were in significantly more varus in those with aseptic loosening (mean 3.4° (SD 3.7°) vs 1.3° (SD 2.0°); p = 0.015). There were no other differences in demographic, radiological, or surgical characteristics between revised and non-revised TKAs for aseptic loosening (p = 0.293 to 1.00). Mean KSS improved significantly from 57.3 (SD 9.5) preoperatively to 92.6 (SD 8.9) at the final follow-up (p < 0.001). CONCLUSION: This is the largest series to date of this design of implant. At short-term follow-up, the rate of aseptic tibial loosening is not overly concerning. Further observation is required to determine if there will be an abnormal rate of loosening at mid- to long-term follow-up. Cite this article: Bone Joint J 2021;103-B(6 Supple A):51-58.

Are Damage Modes Related to Microstructure and Material Loss in Severely Damaged CoCrMo Femoral Heads?

BACKGROUND: Fretting and corrosion in metal-on-polyethylene total hip arthoplasty (THA) modular junctions can cause adverse tissue reactions that are responsible for 2% to 5% of revision surgeries. Damage within cobalt-chromium-molybdenum (CoCrMo) alloy femoral heads can progress chemically and mechanically, leading to damage modes such as column damage, imprinting, and uniform fretting damage. At present, it is unclear which of these damage modes are most detrimental and how they may be linked to implant alloy metallurgy. The alloy microstructure exhibits microstructural features such as grain boundaries, hard phases, and segregation bands, which may enable different damage modes, higher material loss, and the potential risk of adverse local tissue reactions. QUESTIONS/PURPOSES: In this study, we asked: (1) How prevalent is chemically dominated column damage compared with mechanically dominated damage modes in severely damaged metal-on-polyethylene THA femoral heads made from wrought CoCrMo alloy? (2) Is material loss greater in femoral heads that underwent column damage? (3) Do material loss and the presence of column damage depend on alloy microstructure as characterized by grain size, hard phase content, and/or banding? METHODS: Surgically retrieved wrought CoCrMo modular femoral heads removed between June 2004 and June 2019 were scored using a modified version of the Goldberg visually based scoring system. Of the total 1002 heads retrieved over this period, 19% (190 of 1002) were identified as severely damaged, exhibiting large areas of fretting scars, black debris, pits, and/or etch marks. Of these, 43% (81 of 190) were excluded for metal-on-metal articulations, alternate designs (such as bipolar, dual-mobility, hemiarthroplasty, metal adaptor sleeves), or previous sectioning of the implant for past studies. One sample was excluded retroactively as metallurgical analysis revealed that it was made of cast alloy, yielding a total of 108 for further analysis. Information on patient age (57 ± 11 years) and sex (56% [61 of 108] were males), reason for removal, implant time in situ (99 ± 78 months), implant manufacturer, head size, and the CoCrMo or titanium-based stem alloy pairing were collected. Damage modes and volumetric material loss within the head tapers were identified using an optical coordinate measuring machine. Samples were categorized by damage mode groups by column damage, imprinting, a combination of column damage and imprinting, or uniform fretting. Metallurgical samples were processed to identify microstructural characteristics of grain size, hard phase content, and banding. Nonparametric Mann-Whitney U and Kruskal-Wallis statistical tests were used to examine volumetric material loss compared with damage mode and microstructural features, and linear regression was performed to correlate patient- and manufacturer-specific factors with volumetric material loss. RESULTS: Chemically driven column damage was seen in 48% (52 of 108) of femoral heads, with 34% (37 of 108) exhibiting a combination of column damage and imprinting, 12% (13 of 108) of heads displaying column damage and uniform fretting, and 2% (2 of 108) exhibiting such widespread column damage that potentially underlying mechanical damage modes could not be verified. Implants with column damage showed greater material loss than those with mechanically driven damage alone, with median (range) values of 1.2 mm3 (0.2 to 11.7) versus 0.6 mm3 (0 to 20.7; p = 0.03). Median (range) volume loss across all femoral heads was 0.9 mm3 (0 to 20.7). Time in situ, contact area, patient age, sex, head size, manufacturer, and stem alloy type were not associated with volumetric material loss. Banding of the alloy microstructure, with a median (range) material loss of 1.1 mm3 (0 to 20.7), was associated with five times higher material loss compared with those with a homogeneous microstructure, which had a volume loss of 0.2 mm3 (0 to 4.1; p = 0.02). Hard phase content and grain size showed no correlation with material loss. CONCLUSION: Chemically dominated column damage was a clear indicator of greater volume loss in this study sample of 108 severely damaged heads. Volumetric material loss strongly depended on banding (microstructural segregations) within the alloy. Banding of the wrought CoCrMo microstructure should be avoided during the manufacturing process to reduce volumetric material loss and the release of corrosion products to the periprosthetic tissue. CLINICAL RELEVANCE: Approximately 30% of THAs rely on wrought CoCrMo femoral heads. Most femoral heads in this study exhibited a banded microstructure that was associated with larger material loss and the occurrence of chemically dominated column damage. This study suggests that elimination of banding from the alloy could substantially reduce the release of implant debris in vivo, which could potentially also reduce the risk of adverse local tissue reactions to implant debris.

Simultaneous Characterization of Implant Wear and Tribocorrosion Debris within Its Corresponding Tissue Response Using Infrared Chemical Imaging.

Biotribology is one of the key branches in the field of artificial joint development. Wear and corrosion are among fundamental processes which cause material loss in a joint biotribological system; the characteristics of wear and corrosion debris are central to determining the in vivo bioreactivity. Much effort has been made elucidating the debris-induced tissue responses. However, due to the complexity of the biological environment of the artificial joint, as well as a lack of effective imaging tools, there is still very little understanding of the size, composition, and concentration of the particles needed to trigger adverse local tissue reactions, including periprosthetic osteolysis. Fourier transform infrared spectroscopic imaging (FTIR-I) provides fast biochemical composition analysis in the direct context of underlying physiological conditions with micron-level spatial resolution, and minimal additional sample preparation in conjunction with the standard histopathological analysis workflow. In this study, we have demonstrated that FTIR-I can be utilized to accurately identify fine polyethylene debris accumulation in macrophages that is not achievable using conventional or polarized light microscope with histological staining. Further, a major tribocorrosion product, chromium phosphate, can be characterized within its histological milieu, while simultaneously identifying the involved immune cell such as macrophages and lymphocytes. In addition, we have shown the different spectral features of particle-laden macrophages through image clustering analysis. The presence of particle composition variance inside macrophages could shed light on debris evolution after detachment from the implant surface. The success of applying FTIR-I in the characterization of prosthetic debris within their biological context may very well open a new avenue of research in the orthopedics community.

Risk Stratification Algorithm for Management of Head-Neck Taper Tribocorrosion in Patients with Metal-on-Polyethylene Total Hip Arthroplasty: Consensus Statement of the American Association of Hip and Knee Surgeons, the American Academy of Orthopaedic Surgeons, and The Hip Society.

ABSTRACT: Adverse local tissue reactions (ALTRs) were initially reported as complications associated with metal-on-metal (MoM) bearings; however, there is increasing concern regarding the occurrence of adverse local tissue reactions from mechanically assisted crevice corrosion (MACC) at the femoral head-neck junction or between other modular junctions of the implant containing cobalt chromium parts in patients with metal-on-polyethylene (MoP) bearings. ALTR due to MACC at the head-neck junction has primarily been reported in association with cobalt chromium alloy femoral heads. As pain following total hip arthroplasty may have various intrinsic and extrinsic causes, a systematic approach to evaluation (risk stratification algorithm) based on the currently available data is recommended to optimize patient management. Evaluation should begin by ruling out common causes of pain, including component loosening and periprosthetic joint infection. While specialized tests such as blood metal analysis and metal artifact reduction sequence magnetic resonance imaging (MARS MRI) are useful modalities in evaluating for ALTRs, over-reliance on any single investigative tool in the clinical decision-making process should be avoided. There should be a low threshold to perform a systematic evaluation for ALTR due to MACC in patients with metal-on-polyethylene total hip arthroplasty as early recognition and diagnosis is critical, as delays in appropriate treatment initiation may result in soft-tissue damage, which complicates surgical treatment and is associated with a higher risk of complications and poorer patient outcomes.

Comparison of Bone Turnover Biomarkers in Serum and Urine Measured on an Automated Analytical Platform.

BACKGROUND: Matched serum and urine samples from patients who had total hip replacement were used to assess serum-validated immunoassay reagents for use in urine. METHODS: Samples were evaluated by an automated electrochemiluminescent immunoassay (cobas e411; Roche Diagnostics) for C-terminal telopeptide of type I collagen isoform ß (ß-Crosslaps), osteocalcin N-terminal midfragment (N-MID OC), N-terminal propeptide of type I collagen (PINP), and interleukin 6 (IL-6). Spike and recovery experiments were utilized to assess urinary matrix effects. Correlations between serum and both raw and creatinine-corrected urinary measures were assessed. Short-term precision was assessed. RESULTS: Spike and recovery experiments indicated minimal matrix effects of urine for the ß-Crosslaps assay. Potential matrix effects were observed for the other analytes because N-MID OC and IL-6 tended to be slightly overrecovered, whereas PINP was underrecovered. There were strong correlations between serum ß-Crosslaps and raw (Spearman ρ [rs] = 0.725, P < 0.0001) and creatinine-corrected (rs = 0.793, P < 0.0001) urinary measures and moderate correlations between serum N-MID OC and raw (rs = 0.582, P < 0.0001) and creatinine-corrected (rs = 0.482, P < 0.0001) urinary measures. PINP was not detected in urine, and no significant serum-urine correlations were found for IL-6. Short-term precision for urinary levels of ß-Crosslaps, N-MID OC, and IL-6 were 1.6%, 6.3% and 14.4%, respectively. CONCLUSIONS: Urinary measurements of ß-Crosslaps and N-MID OC assays were correlated with serum measurements and had good short-term precision. Urinary PINP was not detectable. IL-6 can be measured in urine using this technology, but the levels did not correlate with serum levels, and the short-term precision was variable.

Augmented Reality in Orthopedic Practice and Education.

Augmented reality (AR) technology enhances a user's perception through the superimposition of digital information on physical images while still allowing for interaction with the physical world. The tracking, data processing, and display technology of traditional computer-assisted surgery (CAS) navigation have the potential to be consolidated to an AR headset equipped with high-fidelity cameras, microcomputers, and optical see-through lenses that create digital holographic images. This article evaluates AR applications specific to total knee arthroplasty, total hip arthroplasty, and the opportunities for AR to enhance arthroplasty education and professional development.