Use of an Artificial Intelligence Device for Evaluating Blood Loss in Complex Major Orthopaedic Surgery Procedures.

BACKGROUND: An artificial intelligence algorithm that analyzes the pulse oximeter waveform in the fingertip can be used to determine the compensatory reserve index (CRI) in trauma patients. This measurement shows the remaining cardiovascular capacity and is known to be more specific and sensitive in detecting blood loss than are routine vital signs. We hypothesized that the CRI measurement could predict loss of reserve cardiovascular capacity in patients undergoing major orthopaedic surgery, and therefore could help in their management. METHODS: A total of 304 patients undergoing lower extremity arthroplasty consented to participate in waveform monitoring. Pulse oximeter waveforms were sensed with a fingertip probe and processed with a tablet computer that remained with the patient during surgery and recovery in the hospital. The CRI, systolic blood pressure, and heart rate were evaluated throughout the postoperative period. RESULTS: The CRI measurement identified a group of patients who were significantly more likely to require transfusions and emergency medical care (P = .000021). Patients who had morbid obesity were especially likely to have low CRI results and a high percentage of clinical events. A CRI of 0.40 or more was evaluated retrospectively as the criterion for withholding transfusion in 54 patients, but that group had a significantly higher incidence of transfusion later in treatment than did the cohort as a whole. The systolic blood pressure and heart rate were not useful in predicting the need for transfusion until late in treatment. CONCLUSIONS: This study suggests that the CRI measurement can identify patients at risk for transfusion and the need for urgent medical care and may aid in the management of blood loss and transfusion in major orthopedic surgery.

Cobalt-chromium femoral components developed scratches and released metal debris in simulated wear whereas ceramic femoral components did not.

AIMS: The aims of this study were to evaluate wear on the surface of cobalt-chromium (CoCr) femoral components used in total knee arthroplasty (TKA) and compare the wear of these components with that of ceramic femoral components. METHODS: Optical profilometry was used to evaluate surface roughness and to examine the features created by the wear process in a knee wear simulator. We developed a method of measuring surface changes on five CoCr femoral components and quantifying the loss of material from the articular surface during the wear process. We also examined the articular surface of three ceramic femoral components from a previous test for evidence of surface damage, and compared it with that of CoCr components. RESULTS: We found that the surface roughness of CoCr components rapidly increased during the first 1,000 wear cycles, then reached a steady state, but material loss from the surface continued at a rate of 1,778,000 µm3 per million cycles as carbides were removed from its matrix. These carbides formed third-body wear particles, leading to the formation of new scratches even as older scratches were worn away. In contrast, no scratching, loss of material, or other surface damage, when evaluated with one nanometer resolution, was found on the surface of the ceramic components after a 15 M wear cycle test. CONCLUSION: This study showed wear and loss of CoCr material from scratching and microabrasive wear in TKA. The material loss from the surface continued in a linear relationship with increasing cycles. We also found the absence of scratching and roughening of ceramic femoral components in simulated wear, suggesting an advantage in wear rate and avoiding metal sensitivity. This may have implications in the management of persistent pain after TKA. Cite this article: Bone Joint J 2021;103-B(6 Supple A):94-101.

Enhanced adhesion of plasma-sprayed commercially pure titanium porous coatings to polished Mg-PSZ ceramic substrates.

The purpose of this study was to evaluate the suitability of a plasma sprayed titanium porous coating on polished magnesia-stabilized zirconia (Mg-PSZ) ceramic surfaces. We hypothesized that diffusion bonding was responsible for the adhesion of the coating to the ceramic substrate. Mg-PSZ tensile test coupons were vibratory polished (roughness Sa = 0.50 µm) or vibratory polished/lapped (Sa = 0.12 µm) before coating and testing. The exposed surfaces after tensile testing were examined by energy dispersive X-ray (EDX) analysis. Mg-PSZ shear test coupons were vibratory polished (Sa = 0.48 µm). As the surface roughness of the ceramic substrate decreased by a factor of 4.175, the coating tensile strength increased from 62.6 to 66.8 MPa, comparable to that of porous coated cobalt chromium (CoCr) and titanium (Ti-6Al-4V) coupons. EDX analyses found titanium everywhere on the ceramic surface after the titanium layer was pulled off with tensile testing, even on areas that appeared to be "clean" to the naked eye. This suggested that titanium oxide compounds were present at the interface, where the oxygen required could only result from diffusion bonding across the interface. Diffusion bonding may also explain the significantly higher amounts of zirconium on the coating surface that had been pulled off the smoother lapped ceramic coupons. The measured shear strength of porous-coated ceramic coupons was significantly higher than that of CoCr and Ti-6Al-4V coupons. The superior adherence of the titanium coating to Mg-PSZ suggests this process has great clinical potential in arthroplasty, especially for patients with metal sensitivity. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1925-1932, 2019.

Phase Transformation and Roughening in Artificially Aged and Retrieved Zirconia-Toughened Alumina Femoral Heads.

BACKGROUND: Zirconia-toughened alumina (ZTA) used in hip arthroplasty contains yttria-stabilized zirconia (Y-TZP) as a toughening agent. However, Y-TZP is well known to degrade in vivo from tetragonal to monoclinic phase transformation. The stability of never-implanted ZTA femoral heads was evaluated in a severe artificial aging test, with retrieved ZTA heads also evaluated for clinical relevance. We hypothesized that ZTA would degrade due to tetragonal-to-monoclinic phase transformation, with changes in surface topography and progressive roughening. Y-TZP specimens served as a positive comparison group, while magnesia-stabilized zirconia (Mg-PSZ), which does not undergo phase transformation, served as a stable comparison group. METHODS: Monoclinic phase concentration, surface topography, and roughness of never-implanted ZTA, Y-TZP, and Mg-PSZ heads were measured by X-ray diffraction and optical profilometry, before and after 2 rounds of 24 hours of hydrothermal aging. Explanted ZTA heads were characterized by the same methods. RESULTS: After 48 hours in an autoclave, the surface of ZTA heads exhibited irregularly spaced protrusions about 20-30 nm high by 100-150 µm in diameter, with significant increases in monoclinic phase concentration (from 12.2% to 21.3%) and surface roughness. Similar features were observed on the surface of explanted ZTA heads, with 33% monoclinic phase after 2.7 years in vivo. CONCLUSION: Based on data collected from ZTA retrievals, this artificial aging test underestimated the amount of phase transformation in vivo. Phase transformation and surface roughening of ZTA heads steadily increased without reaching a plateau, which may lead to stress concentrations and weakening of the ceramic material, and could result in late fracture and wear.

Retrieved Magnesia-Stabilized Zirconia Femoral Heads Exhibit Minimal Roughening and Abrasive Potential.

BACKGROUND: The degradation of ceramic femoral heads made of yttria-stabilized zirconia (Y-TZP) because of tetragonal-to-monoclinic phase transformation in vivo is well-described, whereas magnesia-stabilized zirconia (Mg-PSZ) ceramics resist phase transformation in a warm aqueous environment. The purpose of this study was to evaluate phase transformation, changes in surface topography, and roughness parameters, including changes in surface polarity and abrasiveness, among retrieved zirconia femoral heads. METHODS: A total of 69 Y-TZP and 86 Mg-PSZ-retrieved femoral heads were examined, with 5 never-implanted heads of each type as controls. Selected heads were scanned by x-ray diffraction, to measure % monoclinic phase. All heads were scanned by optical profilometry to find visual evidence of degradation and to measure surface roughness, surface polarity, and the functional roughness parameters. Monoclinic phase % and roughness data were plotted vs time in vivo. RESULTS: Visual evidence of phase transformation was observed among Y-TZP femoral heads, and some exhibited pitting. Y-TZP femoral heads roughened and become more abrasive in vivo, although those made by CeramTec exhibited less degradation than those by Morgan and Saint Gobain. In contrast, Mg-PSZ heads did not exhibit pitting, undergo phase transformation, or roughen in vivo, and retained a negative surface polarity. CONCLUSION: All Y-TZP femoral heads exhibited increased phase transformation with time in vivo, although not all Y-TZP heads exhibited catastrophic roughening. No phase transformation was observed on Mg-PSZ femoral heads after up to 19.2 years in vivo. The lack of degradation among Mg-PSZ retrievals suggests a lower wear potential in joint replacement.

Diamond-like carbon coatings enhance scratch resistance of bearing surfaces for use in joint arthroplasty: hard substrates outperform soft.

The purpose of this study was to test the hypotheses that diamond-like carbon (DLC) coatings will enhance the scratch resistance of a bearing surface in joint arthroplasty, and that a hard ceramic substrate will further enhance scratch resistance by reducing plastic deformation. We tested these hypotheses by applying a hard DLC coating to medical-grade cobalt chromium alloy (CoCr) and magnesia-stabilized zirconia (Mg-PSZ) femoral heads and performing scratch tests to determine the loads required to cause cohesive and adhesive fracture of the coating. Scratch tracks of DLC-coated and noncoated heads were then scanned by optical profilometry to determine scratch depth, width, and pile-up (raised edges), as measures of susceptibility to scratching. DLC-coated CoCr specimens exhibited cohesive coating fracture as wedge spallation at an average load of 9.74 N, whereas DLC-coated Mg-PSZ exhibited cohesive fracture as arc-tensile cracks and chipping at a significantly higher average load of 41.3 N (p < 0.0001). At adhesive coating fracture, DLC-CoCr delaminated at an average load of 35.2 N, whereas DLC-Mg-PSZ fractured by recovery spallation at a significantly higher average load of 46.8 N (p < 0.05). Both DLC-CoCr and DLC-Mg-PSZ specimens exhibited significantly shallower scratches and less pile-up than did uncoated specimens (p < 0.005 and p < 0.01, respectively). However, the harder ceramic substrate of DLC-Mg-PSZ better resisted plastic deformation, requiring significantly higher loads for cohesive and adhesive coating fracture. These findings supported both of our hypotheses.