Early Mechanical Failure Research Articles

An Internet-of-Things-Based Dynamic Scheduling Optimization Method for Unreliable Flexible Manufacturing Systems under Complex Operational Conditions

The dynamic scheduling problem (DSP) in unreliable flexible manufacturing systems (UFMSs) with concurrency, conflicts, resource sharing, and sequential operations is a complex optimization problem that requires the use of efficient solution methodologies. The effectiveness of scheduling UFMSs relies on the quality of equipment maintenance. Currently, UFMSs with consistently large queues of parts awaiting service employ a repair-after-failure approach as a standard maintenance procedure. This method may require unexpected resources, incur costs, consume time, and potentially disrupt the operations of other UFMSs, either partially or fully. This study suggests using a predictive maintenance (PdM) strategy that utilizes the Internet of Things (IoT) to predict and avoid early mechanical equipment failures before they happen in UFMSs, thereby reducing unplanned downtime and enhancing reliability. Therefore, the objective of this paper is to construct timed Petri net (TPN) models using the IoT for the PdM configuration of mechanical equipment in the dynamic scheduling problem of UFMSs. This necessitates that users represent the specific problem using TPNs. The process of PN modeling requires the utilization of domain knowledge pertaining to the target problems as well as to machine information. However, it is important to note that the modeling rules for PNs are straightforward and limited in number. Consequently, the TPN model is applied to generate and formulate mixed-integer linear programming (MILP) instances accurately. This is done to identify the optimal production cycle time, which may be implemented in real-life scenarios. Several UFMS instances are used to demonstrate the applications and effectiveness of the proposed method. The computational results demonstrate that the proposed method shows superior solution quality, effectively solves instances for a total of 10 parts and 6 machines, and achieves a solution in a reasonable CPU time.

What Are the Risk Factors for Mechanical Failure in Spinal Arthrodesis? An Observational Study

Background: The aim of this study was to identify the incidence of early mechanical failure in the first post-surgical year in patients who had undergone spinal surgery and to assess the related risk factors. Methods: A retrospective observational study was conducted examining all patients who consecutively underwent arthrodesis surgery. The incidence of postoperative mechanical failure during the first year was calculated as the primary outcome. Results: A total of 237 patients were identified for statistical analysis. The median age of the group of patients was 47 years (IQR of 44), and 66.6% were female. The incidence of mechanical failure in the first postoperative year was 5.1% overall, with 12 events, and the median time between surgery and the need for revision surgery was 5 months (IQR = 7.75). ASA score (OR = 2.39; p = 0.134), duration of the surgical procedure (OR = 1.27; p = 0.118), and inability to walk at discharge (OR = 7.86; p = 0.007) were independent risk factors associated with the mechanical failure. Conclusions: A higher ASA score and longer duration of surgery were risk factors for mechanical failure in the first year in patients who had undergone spinal surgery and must be carefully considered when planning spinal surgery. Early recovery of ambulation must be encouraged to prevent mechanical failure.

Implant Choice May Reduce the Risk of Early Mechanical Failure in Total Ankle Replacement.

Total ankle replacements (TARs) have rapidly advanced in terms of volume, technique, design, and indications. However, TARs are still at risk for early mechanical failure and revision. Prior studies have investigated potential risk factors for failure, but have been limited to smaller series or older implants. This study sought to identify risk factors for early mechanical failure in modern TAR. This is a retrospective study of a single-institution registry. Five surgeons contributed cases involving patients who underwent a primary TAR with any implant. Implants were grouped on the basis of the type of fixation. The primary outcome was early mechanical failure (revision with component removal for a non-infectious etiology, that is, subsidence, aseptic loosening, and/or malalignment). Logistic regression determined the effects of age, weight, hindfoot arthrodesis, implant type, and radiographic deformity on failure. The 731 included patients had a mean follow-up of 2.7 years. Ten percent (71 patients) had hindfoot arthrodesis. There were 33 mechanical failures (4.5%) at a mean of 1.7 years after the index surgical procedure. Our model demonstrated that hindfoot arthrodesis was associated with 2.7 times greater odds of failure (p = 0.045), every 10 kg of body weight increased the odds of tibial-sided failure by 1.29 times (p = 0.039), and implants with more extensive tibial fixation (stems or keels) lowered the odds of tibial failure by 95% (p = 0.031). In patients with uncontrollable risk factors (hindfoot arthrodesis) or risk factors that may or may not be modifiable by the patient (weight), implants with more robust tibial fixation may be able to reduce the risk of early mechanical failure. Further research is warranted to support efforts to decrease early failure in TAR. Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Synthetic grafts for anterior cruciate ligament reconstructive surgery.

The quest for a good and durable substitute to anterior cruciate ligament (ACL) is driving scientists to explore new promising areas of research. Autologous and allogenic ligament reconstruction bring satisfactory results in managing ACL surgery although their use is associated with significant drawbacks. To overcome the limitations of biologic grafts, many artificial devices have been developed and implanted as a substitute to the native ACL over the past decades. Although many synthetic grafts used in the past have been withdrawn from the market due to early mechanical failures ultimately leading to synovitis and osteoarthritis, there is recently a resurgence of interest in the use of synthetic ligaments for ACL reconstruction. However, this new generation of artificial ligaments, despite promising initial results, have shown to produce serious side effects such as high rupture rates, insufficient tendon-bone healing and loosening. For these reasons, recent advancements in biomedical engineering are focusing on improving technical features of artificial ligaments combining mechanical properties to biocompatibility. Bioactive coatings and surface modification methods have been proposed to enhance synthetic ligament biocompatibility and promote osseointegration. The path to the development of a safe and effective artificial ligament is still full of challenges, however recent advancements are leading the way towards a tissue-engineered substitute to the native ACL.

Effects of bone cement augmentation for uppermost instrumented vertebra on adjacent disc segment degeneration in lumbar fusions

We investigated the long-term effects of bone cement-augmented instrumentation in multilevel lumbar fusions in a retrospective cohort study. The use of cement-augmented screws is one of the techniques used to reduce early mechanical failure in treating multilevel lumbar fusion, especially in the elderly. However, little information is available regarding the long-term effects. A total of 51 patients who had undergone ≥3 levels of lumbar fusion were divided into two groups according to the use of bone cement-augmented screw fixation involving the upper instrumented vertebra: 22 patients in the cement-augmented group (group I) and 29 patients in the non-cement-augmented group (group II). Analysis of radiographic adjacent disc segment degeneration (ASD) revealed patients with lumbosacral fusion with a similar degree of osteoporosis. Radiologic ASD was defined as progression of >2 UCLA (University of California, Los Angeles) grades at 2 years postoperatively. Other sagittal parameters and the preoperative magnetic resonance imaging Pfirrmann grades at the adjacent levels, possibly related to ASD, were also analyzed. No significant differences were present in the preoperative demographic and radiographic parameters between the 2 groups. However, the postoperative kyphotic changes at 3 months were greater for the non-cement-augmented group. In terms of the long-term effects, the incidence of radiologic ASD (group I, n= 20 [95.2%]; vs group II, n= 15 [53.6%]) was significantly higher in the cement-augmented group. Logistic regression analysis of radiologic ASD, including other clinical and radiologic parameters, postoperative pelvic incidence-lumbar lordosis mismatch (odds ratio, 5.201; 95% confidence interval, 1.123-24.090; P= 0.035), and cement augmentation (odds ratio, 20.193; 95% confidence interval, 2.195-185.729; P= 0.008) showed a significant correlation with the development of radiologic ASD at 2 years postoperatively. Although bone cement-augmented screw implantation can prevent kyphotic deformation at the proximal junction of upper instrumented vertebra in the early postoperative stages of multilevel lumbar fusion, a careful selection of patients is required because of possibly accelerated degeneration of adjacent segments.

Prediction of hydrogen concentration responsible for hydrogen-induced mechanical failure in martensitic high-strength steels

Hydrogen, at critical concentrations, responsible for hydrogen-induced mechanical property degradation cannot yet be estimated beforehand and can only be measured experimentally upon fracture with specific specimen sizes. In this work, we develop two deep learning artificial neural network (ANN) models with the ability to predict hydrogen concentration responsible for early mechanical failure in martensitic ultra-high-strength steels. This family of steels is represented by four different steels encompassing different chemical compositions and heat treatments. The mechanical properties of these steels with varying size and morphology of prior austenitic grains in as-supplied state and after hydrogen-induced failure together with their corresponding hydrogen charging conditions were used as inputs. The feed forward back propagation models with network topologies of 12-7-5-3-2-1 (I) and 14-7-5-3-2-1 (II) were validated and tested with unfamiliar data inputs. The models I and II show good hydrogen concentration prediction capabilities with mean absolute errors of 0.28, and 0.33 wt.ppm at test datasets, respectively. A linear correlation of 80% and 77%, between the experimentally measured and ANN predicted hydrogen concentrations, was obtained for Model I and II respectively. This shows that for this family of steels, the estimation of hydrogen concentration versus property degradation is a feasible approach for material safety analysis.

Vacuum Arc Plasma Coating for Polymer Surface Protection— A Plasma Enhanced In-Orbit Additive Manufacturing Concept

In-orbit additive manufacturing (AM) is a promising approach for fabrication of large structures. It allows to expand and accelerate human space exploration possibilities. Extrusion-based AM was demonstrated in zero gravity, while the realization of such a process in orbit-like vacuum conditions is currently under exploration. Still, a solution for protection of the UV and IR radiation sensitive polymers is needed in order to prevent their early mechanical failure under space conditions. Vacuum arc plasma based process is widely applied on earth for thin protective coating deposition. Its major advantage is its scalability—from tiny size used in electric propulsion to large scale coating devices. The usability of the vacuum arc process in space conditions was shown in electric propulsion applications in nano-satellites. In this work we discuss and demonstrate the integration of vacuum arc process as a post processing step after Fused Filament Fabrication (FFF) for additive manufacturing and functionalization of long polymer structures. Here we address the concept for technical realization, which integrates the vacuum arc into additive manufacturing process chain. More over we present a laboratory prototype, which implements this concept together with a use case, where a previously printed PEEK structure is coated with aluminum based coating suitable for UV radiation protection.

Risk Factors for Early Mechanical Failure and Revision in Modern Total Ankle Replacements

Category: Ankle Arthritis; Ankle Introduction/Purpose: Total ankle replacements (TAR) have rapidly advanced in terms of volume, technique, design, and indications. However, they are still at risk for failure and need for revision, even early in the postoperative period. Although recently there has been extensive research on TAR, many studies are limited in their power and sample size to assess risk factors for failure/revision. Using a large multi-surgeon retrospective database, we sought to describe the incidence and etiology of mechanical failure across modern implants. We also aimed to identify risk factors for early mechanical failure. We hypothesized that greater body mass index (BMI) and ipsilateral hindfoot fusion would be predictors of mechanical failure, and that implants with greater extent of tibial fixation (stems and keels) would be protective against mechanical failure. Methods: This is a single-center retrospective review of TAR patients in a prospective database. Adults undergoing primary TAR using any implant (Cadence, Inbone, Infinity, Invision, Salto, STAR, Vantage, Zimmer) who were minimum 2 years post-surgery were included. Exclusion criteria included revision TAR or patients undergoing ankle fusion takedown and conversion to TAR. Five surgeons contributed patients. Demographics, etiology of arthritis, operative data, and postoperative complications, reoperations, and revisions were collected. Revisions and reoperations were classified by standard criteria. Cause of revision was recorded. There were 560 TARs eligible for 2-year follow-up (mean 3.9 +- 1.1 years postoperative), with mean follow-up of 2.2 +- 1.4 years (range 1-71 months). The cohort had mean age 63.8 +- 9.1 years, BMI 29.4 +- 5.2 kg/m2, and 57% were male. Kaplan- Meier survival plots were created. Risk factors for revision due to mechanical failure were analyzed using multivariable logistic regression with partial Wald chi square statistics. Results: Most implants were low-profile (n=444, 79.3%), with 28 implants having tibial keels (5%) and 88 with tibial/talar stems (15.7%). There were 25 (4.5%) revisions of tibial and/or talar components at mean 1.6 years after index surgery (Figure). Preoperative coronal deformity did not impact revision rates (p=0.433). Patients who underwent revision for mechanical failure had significantly higher rates of concomitant hindfoot fusion (20% vs. 8.4%, p=0.047) and greater BMI (31.4 kg/m2 vs. 29.3 kg/m2, p=0.04). In multivariable logistic regression, hindfoot fusion was just short of statistical significance (odds ratio [OR] 2.96, p=0.056), and BMI was not significant (OR 1.05, p=0.417). Stemmed or keeled implants did not significantly decrease revision rates compared to low-profile implants, although the revision rate of stemmed implants was substantially low (1/88, 1.1%). Conclusion: Among 560 modern TAR implants, short-term survivorship was 95% at 2-year follow-up, which is consistent with existing studies. Patients who underwent revision for early mechanical failure had significantly higher BMI and rates of hindfoot arthrodesis. However, these variables fell short of statistical significance in multivariable regression, suggesting that there are either additional factors contributing to revision, or a larger cohort is needed. In addition, these results are likely biased by surgeons' tendencies to use stemmed implants in patients with hindfoot fusions. Further research is warranted to determine if stemmed implants provide a protective effect in these high-risk patients.

Lateral decubitus single position anterior-posterior (AP) fusion shows equivalent results to minimally invasive transforaminal lumbar interbody fusion at one-year follow-up.

This study compares perioperative and 1-year outcomes of lateral decubitus single position circumferential fusion (L-SPS) versus minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) for degenerative pathologies. Multicenter retrospective chart review of patients undergoing AP fusion with L-SPS or MIS TLIF. Demographics and clinical and radiographic outcomes were compared using independent samples t tests and chi-squared analyses with significance set at p < 0.05. A total of 445 patients were included: 353 L-SPS, 92 MIS TLIF. The L-SPS cohort was significantly older with fewer diabetics and more levels fused. The L-SPS cohort had significantly shorter operative time, blood loss, radiation dosage, and length of stay compared to MIS TLIF. 1-year follow-up showed that the L-SPS cohort had higher rates of fusion (97.87% vs. 81.11%; p = 0.006) and lower rates of subsidence (6.38% vs. 38.46%; p < 0.001) compared with MIS TLIF. There were significantly fewer returns to the OR within 1year for early mechanical failures with L-SPS (0.0% vs. 5.4%; p < 0.001). 1-year radiographic outcomes revealed that the L-SPS cohort had a greater LL (56.6 ± 12.5 vs. 51.1 ± 15.9; p = 0.004), smaller PI-LL mismatch (0.2 ± 13.0 vs. 5.5 ± 10.5; p = 0.004). There were no significant differences in amount of change in VAS scores between cohorts. Similar results were seen after propensity-matched analysis and sub-analysis of cases including L5-S1. L-SPS improves perioperative outcomes and does not compromise clinical or radiographic results at 1-year follow-up compared with MIS TLIF. There may be decreased rates of early mechanical failure with L-SPS.

Unexpected high early failure rate of the Nexel total elbow arthroplasty.

BackgroundAseptic loosening, polyethylene wear, and mechanical failure have limited the use of total elbow arthroplasty (TEA) in physically demanding patients. Newer implant designs have been introduced to improve mechanical performance. The purpose of this study was to report the results obtained after implantation of the Nexel TEA.MethodsOver a 3-year period, 2 surgeons implanted a total of 35 consecutive Nexel primary TEAs. The average patient age was 65 years, and standard TEA indications were utilized. Elbows were evaluated for pain, motion, the Mayo Elbow Performance Score, complications, and reoperations.ResultsTwelve elbows underwent a revision surgery with removal of either a part of or all Nexel components at an average of 2.2 years. All revision surgeries performed at our institution revealed gross loosening of the component(s). Metallic debris and periprosthetic fractures were present in 45% and 50% of cases, respectively. Radiographic evaluation of existing components revealed humeral component loosening and periprosthetic fractures in 2 and 4 elbows, respectively. Overall, 17 of 35 (50%) elbows underwent reoperation, and 20 of 35 (60%) elbows sustained at least 1 postoperative complication.ConclusionPrimary TEA with implantation of this implant was associated with an unacceptably high rate of early implant loosening, periprosthetic fracture, and reoperation. We hypothesize that this early unexpected mechanical failure could be explained by both the utilization of a titanium-on-polyethylene bearing surface and a more posterior center of rotation causing premature anterior impingement with flexion leading to failure of the bonding interface, secondary titanium particle shedding, polyethylene wear, and osteolysis.

Functional outcome of internal fixation of complex intraarticular fractures of the distal humerus (OTA-AO type-C) in focus of O’Driscoll criteria for optimized stability

Introduction Internal fixation of distal humeral fractures is challenging because of complex anatomy and articular or metaphyseal comminution. Bi-columnar locked plating (orthogonal or parallel) is the standard method of fixation the success of which requires a rigid stable construct to optimize stability. The aim of this retrospective study was to evaluate the outcome of fixation of type-C distal humeral fractures by orthogonal locked plates and to determine the causes of early mechanical failure according to O’Driscoll criteria of optimized fixation stability. Settings and design A retrospective study conducted in Benha University Hospital. Patients and methods A review of 34 patients with type-C distal humeral fractures fixed with orthogonal anatomical locking plates through the period from 2014 to 2019, and evaluation of their outcome after 24–36 months. Radiographic images were reviewed for O’Driscoll criteria of optimized fixation, and complications were recorded. Results Functional outcome was assessed with Mayo elbow performance score. Twenty patients had an excellent outcome, seven patients good and seven fair in whom, O’Driscoll criteria for optimized fixation stability were not met and fixation was revised. All patients showed radiological union of fractures after about 3 months from definitive fixation. Multivariate analysis of the collected data was done by SPSS software to determine the cumulative percent of its factors and its relation with the final outcome. Conclusion Internal fixation of type-C distal humeral fractures by anatomically precontoured locking plates must be optimized according to O’Driscoll criteria to avoid early mechanical failure, revision surgery, and to achieve satisfactory functional outcome.

124. Cervical deformity score: a composite alignment tool to optimize outcomes while mitigating complications

<h3>BACKGROUND CONTEXT</h3> Cervical alignment and cervical deformity surgery are complex topics. Recently, a score inspired by work on thoracolumbar alignment was developed for cervical alignment (cervical deformity score, CDS). While this score was designed to predict early mechanical failures, its association with patient reported outcomes (PROM) remains unclear. <h3>PURPOSE</h3> Investigate the association between PROM, complications, and a newly described cervical deformity score. <h3>STUDY DESIGN/SETTING</h3> Retrospective review of prospective multicenter database. <h3>PATIENT SAMPLE</h3> A total of 102 adult cervical deformity (CD) patients with at least 1 year follow-up. <h3>OUTCOME MEASURES</h3> NDI, neck pain, EQ5D, complication rates. <h3>Methods</h3> CD patients with baseline and 1-year follow-up were included. Postoperative CDS was constructed using offset from age-adjusted values: SVA [(age -55)*2+25], T1 Slope [(age -55)/4 + 28.7], and TS minus CL [cst: between 26.5 and 14.5°]. Points were assigned based on the offset from alignment targets and the CDS was the sum of the three individual scores. Association with patient-reported outcomes was investigated using Pearson's correlations. Comparison of CDS between patients with and without complication within 1-year was conducted. Logistical regression controlling for demographic and comorbidities was conducted to identify if CDS was an independent predictor of complications. <h3>Results</h3> A total of 102 patients met inclusion criteria (61.7yo±10, 66.7% F); 37.6% of them had a history of previous cervical surgery (16.7% previous ACDF, 11.7% previous posterior fusion). Preoperatively, they had elevated disability (NDI: 47.1±18.1), pain (NSR Neck: 6.6±2.5), myelopathy (mJOA: 13.6±2.7) and lower general health (EQ5D: 0.74±0.07). They also presented with an overall cervical kyphotic alignment (C2-C7: -6.3°±20.9), a moderate cervical anterior alignment (cSVA: 39mm±20; TS-CL: 37.9°±19.4) and a posterior global thoracolumbar alignment (SVA: -3mm±68). The median of number of levels fused was 7 [4-9], with 49% treated with a posterior approach and 30.4% with a combined approach; 83.2% received an osteotomy, 44.6% some posterior osteotomy, 16.8% grade 6 or 7. The mean operative time was 368min±208, median EBL was 525cc [200 1025], and LOS was 5 days [4 8]. At 1 year, patients improved significantly in terms of disability (NDI: 36.2±20.7, 60.8% reached MCID), pain (NSR: 4.1±2.9) and general health (EQ5D: 0.79±0.08) (all p<0.001). The cervical alignment significantly changed (C2-C7: 7.8±14.5m; cSVA: 34mm±15; TS-CL: 28.9°±12.6 all p <0.002), with a 1-year CDS of 1.68±2.46 (prctl [0 3.25]). There was a significant association between increased CDS and increased disability (r=0.273), pain (r=0.336) and lower general health (r=-0.283). Patient with a lower disability level (NDI<20) had a significantly lower CDS (0.71±2.3 vs 2.16±2.4 p<0.004). Patients without any complications before 1 year had a lower CDS (0.78±2.33 vs 2.18±2.40 p=0.005), as did patients without major complications (1.36±2.27 vs 2.50±.78 p=0.037). Deeper analysis revealed significant differences in terms of CDS for patients experiencing cardiopulmonary, instrumentation and radiographic complications (p<0.05). Multivariate analysis, controlling for age and comorbidities, show 1-year CDS to be a significant predictor of complication (p=0.002, OR=1.409). <h3>Conclusions</h3> With better outcomes and lower complication rate, maintaining a proportionate alignment postoperatively can result in superior outcomes following CD surgery. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

Indications for cement augmentation in fixation of geriatric intertrochanteric femur fractures: a systematic review of evidence.

Achieving durable mechanical stability in geriatric intertrochanteric proximal femur fractures remains a challenge. Concomitant poor bone quality, unstable fracture patterns, and suboptimal reduction are additional risk factors for early mechanical failure. Cement augmentation of the proximal locking screw or blade is one proposed method to augment implant anchorage. The purpose of this review is to describe the biomechanical and clinical evidence for cement augmentation of geriatric intertrochanteric fractures, and to elaborate indications for cement augmentation. The PubMed database was searched for English language studies up to January 2021. Studies that assessed effect of calcium phosphate or methylmethacrylate cement augmentation during open reduction and internal fixation of intertrochanteric fractures were included. Studies with sample size < 5, nontraumatic or periprosthetic fractures, and nonunion or revision surgery were excluded. Study selection adhered to PRISMA criteria. 801 studies were identified, of which 40 met study criteria. 9 studies assessed effect of cement augmentation on fracture displacement. All but one found that cement decreased fracture displacement. 10 studies assessed effect of cement augmentation on total load or cycles to failure. All but one demonstrated that augmented implants increased this variable. Complication rates of cement augmentation during ORIF of intertrochanteric fractures ranged from 0 to 47%, while non-augmented implants ranged from 0 to 51%. Reoperation rates ranged from 0 to 11% in the cement-augmented group and 0 to 11% in the non-augmented group. Fixation failure ranged from 0 to 11% in the cement-augmented group and 0 to 20% in the non-augmented group. Nonunion ranged from 0 to 3.6% in the cement-augmented group and 0 to 34% in the non-augmented group. Calcium phosphate or PMMA-augmented CMN fixation of IT fractures increased construct stability and improved outcomes in biomechanical and early clinical studies. The findings of these studies suggest an important role for cement augmentation in patient populations at high risk of mechanical failure.

Functional outcome of midshaft clavicle fractures treated with a pre-contoured locking plate: A prospective study

Introduction: Traditionally, displaced mid clavicular fractures have been treated with conservative methods. Conservative methods like strapping gives mediocre results. The present study has been undertaken to study the role of pre-contoured locking compression plate in the fixation of mid-third clavicle fractures. Materials and Methods: 40 patients with mid-shaft clavicle fractures (Robinson 2B) with displacement >2 cms were treated with open reduction and internal fixation with a pre-contoured locking plate and functional outcome through 3 months was assessed. Results: Union was seen radiologically in all the fractures by 10-12 weeks. The average Constant-Murley score at 3 months was 93.5. None of our patients had complications like malunion, wound dehiscence, hardware irritation, early mechanical failure, incisional numbness, infections and neurovascular damage. There were 4 patients with hardware prominence, 2 cases of hypertrophic scar formation, 2 patients with delayed union at 18 weeks and 1 case of plate loosening. Conclusions: Pre-contoured locking plate fixation in displaced fractures of clavicle allows earlier return to a pain free functional shoulder. Keywords: Clavicle fracture, Middle third, Pre-contoured locking plate.

Early Short-Term Postoperative Mechanical Failures of Current Ceramic-on-Ceramic Bearing Total Hip Arthroplasties.

Although ceramic-on-ceramic (CoC) bearings have been shown to produce the smallest amount of wear volume in vitro as well as in vivo studies when used for total hip arthroplasties (THA), concerns about the failure of these bearing surfaces persist due to early failures observed after short postoperative time. In this study, an exhaustive analysis of the early failure occurred on the new generation of ceramic bearings, consisting of a composite alumina matrix-based material reinforced with yttria-stabilized tetragonal zirconia (Y-TZP) particles, chromium dioxide, and strontium crystals, was performed. For this study, 118 CoC bearings from 117 patients were revised. This article describes a group of mechanical failure CoC-bearing BIOLOX THA hip prosthesis patients without trauma history. The retrieved samples were observed under scanning electron microscopy (SEM), composition was analyzed with energy dispersive X-ray spectroscopy (EDX), and damaged surfaces were analyzed by grazing-incidence X-ray diffraction (GI-XRD) and white light interferometry. In the short term, CoC articulations provided similar mechanical behavior and functional outcome to those in XLPE cases. However, 5% more early mechanical failures cases were observed for the ceramic components. Although the fracture rate of third generation CoC couples is low, the present study shows the need to further improve the third generation of CoC-bearing couples for THA. Despite the improved wear compared to other materials, stress concentrators are sources of initial crack propagation, such as those found in the bore-trunnion areas. Moreover, in view of the evidence observed in this study, the chipping observed was due to the presence of monoclinic phase of the Y-TZP instead of tetragonal, which presents better mechanical properties. The results showed that total safety after receiving a THA is still a goal to be pursued.

Cervical Characterization with Tactile-Ultrasound Probe.

Background:Premature cervical softening and shortening may be considered an early mechanical failure that predisposes to preterm birth. Preliminary clinical studies demonstrate that cervical elastography may be able to quantify this phenomenon and predict spontaneous preterm delivery.Objective:To explore a new approach for cervix elasticity and length measurements with tactile-ultrasound probe.Methods:Cervix probe has tactile array and ultrasound transducer designed to apply controllable load to cervix and acquire stress-strain data for calculation of cervical elasticity (Young’s modulus) and cervical length for four cervix sectors. Average values, standard deviations, intraclass correlation coefficients and the 95% limits of agreement (Bland-Altman plots) were estimated.Results:Ten non-pregnant and ten pregnant women were examined with the probe. The study with non-pregnant women demonstrated a reliable acquisition of the tactile signals. The ultrasound signals had a prolonged appearance; identification of the internal os of the cervix in these signals was not reliable. The study with pregnant women with the gestational age of 25.4 ± 2.3 weeks demonstrated reliable data acquisition with real-time visualization of the ultrasound signals. Average values for cervical elasticity and standard deviations of 19.7 ± 15.4 kPa and length of 30.7 ± 6.6 mm were calculated based on two measurements per 4 sectors. Measurement repeatability calculated as intraclass correlation coefficients between two measurements at the same cervix sector on pregnant women was found to be 0.97 for cervical elasticity and 0.93 for the cervical length. The 95% limits of agreement of 1) cervical elasticity were from −22.4% to +14.9%, and 2) cervical length from −13.3% to +16.5%.Conclusions:This study demonstrated clinically acceptable measurement performance and reproducibility. The availability of stress-strain data allowed the computation of cervical elasticity and length. This approach has the potential to provide cervical markers to predict spontaneous preterm delivery.

Treatment of distal femur fractures with VA-LCP condylar plate: A single trauma centre experience

IntroductionGiven the recent criticisms in the literature regarding Synthes Variable Angle Locking Compression Condylar Plate (VA-LCP), the purpose of this study was to evaluate functional outcome, fracture healing, and complications of distal femoral intra-articular fractures using this device. MethodsPatients with distal femoral fractures treated with 4.5 mm VA-LCP Curved Condylar Plate were included in this retrospective study. Follow-ups were at 4 weeks, 3 months, 6 months and 1 year. For the clinical and functional assessment of the knee, WOMAC, Koos Knee Survey, the Knee Score Society and the SF-12 questionnaire were used. Radiographically we assessed the fracture healing and the angles of the operated limb compared to the healthy contralateral limb. Complications have also been described. ResultsForty-two patients with distal femoral fractures were included in the study. The mean follow-up was 8 months. Most cases (57%) reported a type 33-A fracture. Radiological healing was achieved in 33 cases; the mean time required to heal was 13 weeks. Three patients had an early postoperative complication and four cases had a late complication. Five cases required additional surgical procedures. Most patients (47.2%) achieved a complete flexion of 130° or more. WOMAC mean value 27.4%, KSS mean value 77.6 for the clinical part and 60 for the functional part, KOOS mean score 60.1, SF-12 mean score 46.1 for MCS and 35.5 for PCS. DiscussionThe results of this retrospective study suggest that VA-LCP Curved Condylar Plates have a good functional outcome and fracture healing similar to other standard distal femoral locking plates. VA technology allows greater versatility in fractures internal fixation regardless of the plate design. Fixation devices or Prosthesis implants previously placed may be avoided, as in periprosthetic fractures. Moreover, we have not recorded any early mechanical damage. ConclusionsOsteosynthesis with Synthes 4.5 mm VA-LCP Curved Condylar Plate demonstrated to have no early mechanical failure rate with good clinical and radiological results.

Early Mechanical Failure of a Tumoral Endoprosthesic Rotating Hinge in the Knee: Does Bumper Wear Contribute to Hyperextension Failure?

Tumor surgeons use a variety of endoprosthetic designs for reconstruction after bone tumor resection. However, functional results and implant survival have not been evaluated for each design. Because the outcomes and failure modes (for example, implant breakage, loosening) may differ between prosthetic design types, it is important to examine the problems associated with different designs. Because of experiences in our practice, we became concerned about a surprisingly high frequency of device breakage with one particular design, and we wished to report on that experience. QUESTION/PURPOSES: (1) In a small series of patients, what proportion of a particular design (Zimmer® Segmental [Zimmer Inc, Warsaw, IN, USA]) of rotating-hinge endoprosthesis experienced implant breakage at short-term follow-up? (2) What patient symptoms were associated with this finding? (3) What is the function as assessed by Musculoskeletal Tumor Society (MSTS) score with the use of this implant before and after revision? We treated 87 patients in our tertiary center from 1987 to 2014 who had sarcomas around the knee with wide resection and reconstruction with tumoral endoprosthesis; five patients were lost to follow-up. In all, 33 of the remanining 82 prostheses, treated from 1987 to 2006, were reconstructed with fixed-hinge designs. From 2006 to 2014, 49 patients were reconstructed with a knee endoprosthesis, and 48 of them had a rotating-hinge prosthesis. In our center, we mostly used four designs: 16 of 49 patients were reconstructed with GMRS (Stryker Howmedica, Kalamazoo, MI, USA), seven received the LPS™ (DePuy Synthes, Warsaw, IN, USA), 20 of 49 had the METS (Stanmore, Hertfordshire, UK), and six of 49 received the Zimmer Segmental. The focus of this report is on the six patients with the Segmental. We retrospectively gathered clinical and radiologic data from these six patients' records and we assessed radiographic images. We evaluated function with the MSTS score of the 49 patients. The median follow-up duration of the Segmental prosthesis reconstruction was 65 months (range 24 to 85). Three of the six patients had posterior instability and recurrent joint effusion on physical examination. Three patients who did not have hyperextension presented with restricted knee ROM. Six revision procedures were performed in three patients. The median MSTS score at 6 months for the Segmental® prosthesis was 15 of 30 (range 6 to 24). The score in the three patients who had posterior instability was 9 of 30 (range 6 to 15) and it improved to median 25 of 30 (range 19 to 30) 6 months after revision. The patients with the Segmental® prosthesis who did not undergo revision had a median MSTS score of 20 (range 16 to 24). The Zimmer Segmental rotating-hinge tumoral prosthesis underwent revision for implant breakage at short term in three of six patients after tumor resection and reconstruction of the knee. Bumper breakage was associated with posterior instability that was related to wear of the bushing blocking system. We are unaware of reports of these issues by other observers or in other prosthetic designs, but we feel larger registries should be created to see if this failure mechanism has been observed by others. If so, this design needs to be improved or the blocking system should be avoided.Level of Evidence Level IV, therapeutic study.

Simulation based on the Gompertz Curve Model to Assess Early Systematic and Mechanical BEEMS Failures

The purpose of this study is to introduce the simulation procedure for assessing early systematic and mechanical failures of the Building, Environment and Energy Management System (BEEMS) to prevent the newly-installed system from incurring major damage, troubles and risks. Here, the Gompertz curve model is simulated using the unit of measurement called “mean time between failures (MTBF)” to evaluate failure rates. The research focuses are placed on the types of facilities and devices, the number of failure cases, the Mean Time Between Failures (MTBF), estimations on the basis of the Weibull analysis, the Bayesian method and the Gompertz curve model. Especially, it was confirmed to be effective to use the Gompertz curve model together with the Bayesian method for data of 20 failures or less. And the Gompertz curve model would be appropriate for the estimation of a regular inspection period more precisely under several assumptions based on a limited number of data as its lower limit of probability could deliver some margin for safety.

Cervix Elasticity and Length Measurements With Tactile-Ultrasound Probe: First Clinical Experience [32J

INTRODUCTION: Premature cervix softening and shortening may be considered an early mechanical failure that predisposes to preterm birth. Clinical studies demonstrate that cervical elastography may be able to predict spontaneous preterm delivery. The purpose of the study was to access a new approach to cervix elasticity and length measurements based on the acquisition of stress-strain data by tactile and ultrasound transducers. METHODS: A Cervix Monitor (CM) was designed to provide a single-use, inexpensive cervix probe with a tactile array and an ultrasound transducer. 10 non-pregnant and 10 pregnant women at 22-29 weeks of pregnancy were examined with the CM in IRB approved studies. Cervix stress-to-strain ratio was used to calculate cervix elasticity (Young's modulus) for four cervix sectors at 3, 6, 9, and 12 o'clock. RESULTS: The study with non-pregnant women demonstrated the device safety. The study with pregnant women with gestational age 25.4±2.3 weeks demonstrated cervix elasticity 19.7±15.4 kPa and length 30.7±6.6 mm. Intraclass correlation coefficients between two measurements at the same cervix sector were found to be 0.97 for cervix elasticity and 0.93 for cervix length. The bias and the 95% limits of agreement (Bland-Altman plot) of cervix elasticity measurement are 3.8% and -22.4% to +14.9%, the precision was 9.5%. The bias and the 95% limits of agreement of cervix length measurement are -1.6% and -13.3% to +16.5%, the precision was 7.6%. CONCLUSION: The CM stress-strain data allowed computation of cervix elasticity and length. This approach has a potential to provide cervix markers to predict spontaneous preterm delivery in a cost-effective manner.