Detection of aseptic loosening in total knee replacements: a systematic review and meta-analysis

Non-invasive quantitative assessment of induced component displacement can safely and accurately diagnose tibial component loosening in patients: A prospective diagnostic study

PURPOSE

Aseptic loosening often requires major, expensive and invasive revision surgery. Current diagnostic modalities merely show indirect signs of loosening. A recent proof of concept study proposed a non-invasive technique for the quantitative and visual assessment of implant movement as a diagnostic aid for tibial component loosening. The primary research question addressed is whether this novel diagnostic modality can safely and effectively aid the diagnosis of aseptic loosening.

METHODS

This clinical study included patients suspected of aseptic total knee arthroplasty (TKA) loosening listed for revision surgery and asymptomatic patients. Safety was evaluated using a numerical rating scale (NRS) for discomfort and by registration of adverse events. Feasibility was assessed by recording the duration and ease of the procedure. Intra- and interrater reliability were evaluated. In symptomatic patients, diagnostic accuracy metrics were evaluated with intra-operative assessment as a reference test.

RESULTS

In total, 34 symptomatic and 38 asymptomatic knees with a TKA were analysed. The median NRS for discomfort during loading was 6 (interquartile range [IQR]: 3.75-7.00) in symptomatic patients and 2 (IQR: 1.00-3.00) in asymptomatic patients. No adverse events were reported. The majority of users found the use of the loading device easy. The median time spent in the computed tomography room was 9 min (IQR: 8.00-11.00). Excellent to good intra- and interrater reliabilities were achieved. Diagnostic accuracy analysis resulted in a sensitivity of 0.91 (95% confidence interval [CI]: 0.72-0.97) and a specificity of 0.72 (95% CI: 0.43-0.90).

CONCLUSIONS

The proposed diagnostic method is safe, feasible, reliable and accurate in aiding the diagnosis of aseptic tibial component loosening.

LEVEL OF EVIDENCE

Level II.

MRI and SPECT/CT demonstrate, with low certainty of evidence, the highest diagnostic accuracy for aseptic knee arthroplasty loosening: A systematic comparative diagnostic test review and meta-analysis

PURPOSE

The purpose of this study was to evaluate and compare the diagnostic accuracy of modalities used to aid the diagnosis of aseptic knee arthroplasty loosening.

METHODS

A comparative diagnostic test accuracy systematic review and meta-analysis was conducted following the Cochrane and PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. PubMed, EMBASE and Cochrane databases were searched for original articles evaluating diagnostic modalities up to March 2024. Included studies compared the modality (index test) to the intraoperative finding as reference test. The QUADAS-C (Quality Assessment of Diagnostic Accuracy Studies-Comparative) tool was used to assess the quality of the included studies. The GRADE (Grading of Recommendations, Assessment, Development and Evaluation) approach was used to evaluate the certainty of evidence. Level of evidence was evaluated using the Oxford Levels of Evidence tool. The primary outcome was the summary of diagnostic accuracy metrics for each modality as demonstrated by a summary receiver-operating characteristic (SROC) curve.

RESULTS

The search yielded 467 articles. Of these, 14 articles were included. These 14 articles evaluated a total of five different diagnostic modalities: bone scintigraphy (three studies, 146 cases), 18-fluorodeoxyglucose positron emission tomography (two studies, 50 cases), single-photon emission computed tomography combined with computed tomography (SPECT/CT) (seven studies, 371 cases), radionuclide arthrogram (three studies, 196 cases) and magnetic resonance imaging (MRI) (one study, 116 cases). Nine studies exhibited a high risk of bias in patient selection, and all studies showed a high risk of bias related to the reference test. The majority of the included studies were classified as Level III evidence, leading to an overall low level of certainty in the evidence. The most accurate tests, as demonstrated by the SROC analysis, were MRI and SPECT/CT, with sensitivities ranging from 0.00 to 1.00 and 0.33 to 1.00 and specificities between 0.31-1.00 and 0.00-1.00, respectively.

CONCLUSIONS

This review and meta-analysis evaluated available diagnostic modalities to aid the diagnosis of knee arthroplasty loosening and based on a low certainty of evidence suggests that MRI and SPECT/CT are currently the most accurate modalities available to aid the diagnosis of aseptic loosening of knee arthroplasty components.

LEVEL OF EVIDENCE

Level III.

Passive Biotelemetric Detection of Tibial Debonding in Wireless Battery-Free Smart Knee Implants

Aseptic loosening is the dominant failure mechanism in contemporary knee replacement surgery, but diagnostic techniques are poorly sensitive to the early stages of loosening and poorly specific in delineating aseptic cases from infections. Smart implants have been proposed as a solution, but incorporating components for sensing, powering, processing, and communication increases device cost, size, and risk; hence, minimising onboard instrumentation is desirable. In this study, two wireless, battery-free smart implants were developed that used passive biotelemetry to measure fixation at the implant-cement interface of the tibial components. The sensing system comprised of a piezoelectric transducer and coil, with the transducer affixed to the superior surface of the tibial trays of both partial (PKR) and total knee replacement (TKR) systems. Fixation was measured via pulse-echo responses elicited via a three-coil inductive link. The instrumented systems could detect loss of fixation when the implants were partially debonded (+7.1% PKA, +32.6% TKA, both p < 0.001) and fully debonded in situ (+6.3% PKA, +32.5% TKA, both p < 0.001). Measurements were robust to variations in positioning of the external reader, soft tissue, and the femoral component. With low cost and small form factor, the smart implant concept could be adopted for clinical use, particularly for generating an understanding of uncertain aseptic loosening mechanisms.

Zirconium as a Promising Synovial Biomarker for Loose Cemented Knee Prosthesis

BACKGROUND

Aseptic loosening is the most common mode of failure after total knee arthroplasty. Despite this, the diagnosis often remains challenging and mainly relies on imaging modalities. Until today, no biomarker exists to aid in diagnosing loosening of the implants. As zirconium (Zr) is often found in bone cement, where it serves as radiopacifier, this study aimed to establish Zr as a synovial biomarker for loosened cemented knee prostheses.

METHODS

A total of 31 patients scheduled for revision of a cemented knee prostheses were included. In all patients, the initial used cement contained Zr. After arthrotomy, specimens of synovial fluid were taken and levels of Zr were measured by inductively coupled plasma mass spectrometry. Depending on the necessary amount of force for explantation, the implants were graded "loose" or "well-fixed". Preoperative radiographs were evaluated by 2 independent physicians.

RESULTS

The concentration of Zr in the synovial fluid differed significantly (P < .001) between the "loose" (mean 170.9 μg/L, range 0 to 1941 μg/L) and the "well-fixed" (mean 0.6 μg/L, range 0 to 6 μg/L) implants. The receiver operating characteristic analysis revealed 0.25 μg/l as an optimal cutoff value leading to a sensitivity of 0.84, a specificity of 0.92, a positive predictive value of 0.94, and a negative predictive value of 0.79. There was no significant difference in the diagnostic performance compared to radiographs (P = .66).

CONCLUSIONS

Zirconium proved to be a reliable novel synovial biomarker for diagnosing aseptic loosening of knee prothesis fixed with cement containing Zr. This biomarker should not be interpreted in isolation, but in combination with existing diagnostic tools.

The Diagnostic Characteristic and Reproducibility of Bone Scintigraphy Single-Photon Emission Computed Tomography/Computed Tomography for Diagnosing Aseptic Loosening of Uncemented Total Knee Arthroplasty

BACKGROUND

The primary objective of this study was to investigate the diagnostic characteristics of bone scintigraphy single-photon emission computed tomography/computed tomography (BS-SPECT/CT) for diagnosing aseptic loosening after uncemented total knee arthroplasty (TKA), and to evaluate the following aspects: how to manage inconclusive results, the interobserver reliability, and the location of tracer uptake between symptomatic cases with and without aseptic loosening.

METHODS

In this study, 180 patients who had uncemented TKA and persistent knee pain suspected of aseptic loosening were included. As part of routine medical care, BS-SPECT/CT was used, and its results were compared with the reference standard, which involved revision surgery for aseptic loosening or a 12-month follow-up without revision or imaging. Inconclusive BS-SPECT/CT results were considered either negative (best-case scenario) or positive (worst-case scenario). Sensitivity, specificity, positive/negative likelihood ratios (LRs), and positive/negative predictive values (PPV and NPV) were calculated. Sensitivity analyses were conducted by comparing the diagnostic characteristics between cases with a follow-up of less and more than 2 years of follow-up. The anatomical distribution of tracer uptake and interobserver reliability were also evaluated.

RESULTS

Of the 180 BS-SPECT/CT scans conducted, 22 were determined positive, 113 negative, and 45 inconclusive. The best-case scenario showed a sensitivity of 66.7%, specificity of 93.8%, +LR 10.8, -LR 0.4, PPV 54.6%, and NPV 96.2%. In contrast, the worst-case scenario had a sensitivity of 94.4%, specificity of 69.1%, +LR 3.1, -LR 0.1, PPV 25.4%, and NPV 99.1%. Sensitivity analyses revealed no relevant differences in characteristics between the 2 TKA-interval groups. The interobserver reliability was fair-to-moderate (κ = 0.39; 95% confidence interval 0.18 to 0.60), with an estimated agreement of 79% (95% confidence interval 70 to 87). Four prosthetic zones had a notably higher proportion of cases with tracer uptake in those with aseptic loosening compared to those without.

CONCLUSIONS

The test characteristics of BS-SPECT/CT were deemed appropriate in patients who have complaints of uncemented TKA suspected of aseptic loosening. Inconclusive cases were best categorized as negative, especially in patients who have a short interval between TKA and the first BS-SPECT/CT. Increased tracer uptake in 4 prosthetic zones was observed in cases of aseptic loosening, although interobserver reliability was fair to moderate.

LEVEL OF EVIDENCE

Level III, Diagnostic Retrospective Cohort Study.

Load-induced deformation of the tibia and its effect on implant loosening detection

CT imaging under external valgus and varus loading conditions and consecutive image analysis can be used to detect tibial implant loosening after total knee arthroplasty. However, the applied load causes the tibia to deform, which could result in an overestimation of implant displacement. This research evaluates the extent of tibia deformation and its effect on measuring implant displacement. Ten cadaver specimen with TKA were CT-scanned under valgus/varus loading (20 Nm), first implanted without bone cement fixation (mimicking a loose implant) and subsequently with bone cement fixation (mimicking a fixed implant). By means of image analysis, three relative displacements were assessed: (1) between the proximal and distal tibia (measure of deformation), (2) between the implant and the whole tibia (including potential deformation effect) and (3) between the implant and the proximal tibia (reduced deformation effect). Relative displacements were quantified in terms of translations along, and rotations about the axes of a local coordinate system. As a measure of deformation, the proximal tibia moved relative to the distal tibia by, on average 1.27 mm (± 0.50 mm) and 0.64° (± 0.25°). Deformation caused an overestimation of implant displacement in the cemented implant. The implant displaced with respect to the whole tibia by 0.45 mm (± 0.22 mm) and 0.79° (± 0.38°). Relative to the proximal tibia, the implant moved by 0.23 mm (± 0.10 mm) and 0.62° (± 0.34°). The differentiation between loose and fixed implants improved when tibia deformation was compensated for by using the proximal tibia rather than the whole tibia.

ACR Appropriateness Criteria® Imaging After Total Knee Arthroplasty: 2023 Update

Total knee arthroplasty is the most commonly performed joint replacement procedure in the United States. This manuscript will discuss the recommended imaging modalities for six clinical variants; 1. follow-up of symptomatic or asymptomatic patients with a total knee arthroplasty. Initial imaging, 2. Suspected infection after total knee arthroplasty. Additional imaging following radiographs, 3. Pain after total knee arthroplasty. Infection excluded. Suspect aseptic loosening or osteolysis or instability. Additional imaging following radiographs, 4. Pain after total knee arthroplasty. Suspect periprosthetic or hardware fracture. Additional imaging following radiographs, 5. Pain after total knee arthroplasty. Measuring component rotation. Additional imaging following radiographs, and 6. Pain after total knee arthroplasty. Suspect periprosthetic soft-tissue abnormality unrelated to infection, including quadriceps or patellar tendinopathy. Additional imaging following radiographs. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

SPECT/CT of Total Ankle Arthroplasty

Use of SPECT/CT (Single Photon Emission Computed Tomography/Computed Tomography) is increasing providing additional information in patients with inconclusive clinical examination and unremarkable imaging findings presenting with chronic pain after total ankle arthroplasty. To differentiate the cause of pain after total ankle arthroplasty can be challenging. SPECT/CT combines structural and metabolic imaging as a hybrid tool leading to higher specificity and overall diagnostic accuracy presumably in cases of gutter impingement, prosthetic loosening, and osteoarthritis of adjacent joints. Moreover, SPECT/CT can complement diagnostic work up in periprosthetic joint infections. Basal tracer enhancement has to be considered for the interpretation of imaging findings.

Mechanical complications after total knee arthroplasty

INTRODUCTION

With the increasing demand for total knee arthroplasty (TKA) and the burden of revision TKA on the healthcare system, as well as the quality of life implications for patients, it is extremely important for surgeons to be able to anticipate and prevent TKA mechanical complications. Surgeons must be familiar with the different causes and mechanisms of TKA complications so that they can properly treat patients with failed TKAs and better avoid these complications.

AREAS COVERED

This review addresses TKA mechanical complications and provides context for the topic. A detailed review of surgical factors, implant factors, and patient factors that contribute to mechanical complications after TKA is provided. All of the literature cited in this review was gathered from the PubMed online database using different keywords based on the section of the manuscript.

EXPERT OPINION

As surgeons and engineers solve certain issues in TKA, new challenges will inevitably arise. We must continue to push forward and innovate from both a surgical technique and implant design perspective.

Impact of time to revision total knee arthroplasty on outcomes following aseptic failure

INTRODUCTION

Prior studies have demonstrated an association between time to revision total knee arthroplasty (rTKA) and indication; however, the impact of early versus late revision on post-operative outcomes has not been reported.

MATERIALS AND METHODS

A retrospective, observational study examined patients who underwent unilateral, aseptic rTKA at an academic orthopedic hospital between 6/2011 and 4/2020 with > 1-year of follow-up. Patients were early revisions if they were revised within 2 years of primary TKA (pTKA) or late revisions if revised after greater than 2 years. Patient demographics, surgical factors, and post-operative outcomes were compared.

RESULTS

470 rTKA were included (199 early, 271 late). Early rTKA patients were younger by 2.5 years (p = 0.002). The predominant indications for early rTKA were instability (28.6%) and arthrofibrosis/stiffness (26.6%), and the predominant indications for late rTKA were aseptic loosening (45.8%) and instability (26.2%; p < 0.001). Late rTKA had longer operative times (119.20 ± 51.94 vs. 103.93 ± 44.66 min; p < 0.001). There were no differences in rTKA type, disposition, hospital length of stay, all-cause 90-day emergency department visits and readmissions, reoperations, and number of re-revisions.

CONCLUSIONS

Aseptic rTKA performed before 2 years had different indications but demonstrated similar outcomes to those performed later. Early revisions had shorter surgical times, which could be attributed to differences in rTKA indication.

LEVEL OF EVIDENCE

III, retrospective observational analysis.

Machine Learning for Detecting Total Knee Arthroplasty Implant Loosening on Plain Radiographs

(1) Background: The purpose of this study was to investigate whether the loosening of total knee arthroplasty (TKA) implants could be detected accurately on plain radiographs using a deep convolution neural network (CNN). (2) Methods: We analyzed data for 100 patients who underwent revision TKA due to prosthetic loosening at a single institution from 2012 to 2020. We extracted 100 patients who underwent primary TKA without loosening through a propensity score, matching for age, gender, body mass index, operation side, and American Society of Anesthesiologists class. Transfer learning was used to prepare a detection model using a pre-trained Visual Geometry Group (VGG) 19. For transfer learning, two methods were used. First, the fully connected layer was removed, and a new fully connected layer was added to construct a new model. The convolutional layer was frozen without training, and only the fully connected layer was trained (transfer learning model 1). Second, a new model was constructed by adding a fully connected layer and varying the range of freezing for the convolutional layer (transfer learning model 2). (3) Results: The transfer learning model 1 gradually increased in accuracy and ultimately reached 87.5%. After processing through the confusion matrix, the sensitivity was 90% and the specificity was 100%. Transfer learning model 2, which was trained on the convolutional layer, gradually increased in accuracy and ultimately reached 97.5%, which represented a better improvement than for model 1. Processing through the confusion matrix affirmed that the sensitivity was 100% and the specificity was 97.5%. (4) Conclusions: The CNN algorithm, through transfer learning, shows high accuracy for detecting the loosening of TKA implants on plain radiographs.

Detection of Prosthetic Loosening in Hip and Knee Arthroplasty Using Machine Learning: A Systematic Review and Meta-Analysis

Background: prosthetic loosening after hip and knee arthroplasty is one of the most common causes of joint arthroplasty failure and revision surgery. Diagnosis of prosthetic loosening is a difficult problem and, in many cases, loosening is not clearly diagnosed until accurately confirmed during surgery. The purpose of this study is to conduct a systematic review and meta-analysis to demonstrate the analysis and performance of machine learning in diagnosing prosthetic loosening after total hip arthroplasty (THA) and total knee arthroplasty (TKA). Materials and Methods: three comprehensive databases, including MEDLINE, EMBASE, and the Cochrane Library, were searched for studies that evaluated the detection accuracy of loosening around arthroplasty implants using machine learning. Data extraction, risk of bias assessment, and meta-analysis were performed. Results: five studies were included in the meta-analysis. All studies were retrospective studies. In total, data from 2013 patients with 3236 images were assessed; these data involved 2442 cases (75.5%) with THAs and 794 cases (24.5%) with TKAs. The most common and best-performing machine learning algorithm was DenseNet. In one study, a novel stacking approach using a random forest showed similar performance to DenseNet. The pooled sensitivity across studies was 0.92 (95% CI 0.84-0.97), the pooled specificity was 0.95 (95% CI 0.93-0.96), and the pooled diagnostic odds ratio was 194.09 (95% CI 61.60-611.57). The I2 statistics for sensitivity and specificity were 96% and 62%, respectively, showing that there was significant heterogeneity. The summary receiver operating characteristics curve indicated the sensitivity and specificity, as did the prediction regions, with an AUC of 0.9853. Conclusions: the performance of machine learning using plain radiography showed promising results with good accuracy, sensitivity, and specificity in the detection of loosening around THAs and TKAs. Machine learning can be incorporated into prosthetic loosening screening programs.

The role of SPECT/CT in painful, noninfected knees after knee arthroplasty: a systematic review and meta-analysis-a diagnostic test accuracy review

PURPOSE

The aim of this systematic review was to present the current evidence on the clinical use of single-photon emission computed tomography/computed tomography (SPECT/CT) in the evaluation of noninfected painful knees after knee arthroplasty.

METHODS

Embase, PubMed, Google Scholar, Ovid, Scopus, Science Direct and the Cochrane Database of Systematic Reviews were searched from database inception to May 2022 following the PRISMA guidelines. As a primary outcome, we defined the role of SPECT/CT in the diagnostic approach to noninfected painful knee arthroplasty; as a secondary objective, we described the noninfection-related factors linked to painful knee arthroplasty. Pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio values and other indicators were calculated; receiver operating characteristic (ROC) curve analysis results and a summary of the areas under the curve (AUCs) from the included studies were reported. A Fagan plot, likelihood ratio plot and Deeks' funnel plot were generated and analysed. Methodological quality was assessed using the QUADAS-2 tool, and the certainty of evidence was assessed by the GRADE approach.

RESULTS

A total of 493 publications were identified, of which eight met the inclusion criteria, with a final pooled sample size of 308 patients. The pooled sensitivity and specificity of SPECT/CT in diagnosing the source of pain in painful knee prostheses were 0.86 (95% CI: 0.75-0.93) and 0.90 (95% CI: 0.79-0.96), respectively, with pooled +LR and -LR values of 8.9 (95% CI: 4.11-19.19) and 0.15 (95% CI: 0.09-0.28). The pooled diagnostic odds ratio was 57.35, and the area under the curve was 0.94. SPECT/CT highly accurately identified different sources of pain, such as loosening of the prosthetic components, patellofemoral overloading, instability, malalignment of the components and degeneration of the patellofemoral compartment. The confidence of the estimates was moderate according to the GRADE approach.

CONCLUSION

With demonstrated high sensitivity and specificity, as a diagnostic tool, SPECT/CT can identify the source of pain in painful knees after knee arthroplasty, particularly in cases of loosening, patellofemoral disorders and component malalignment (level of evidence III). These findings have significant clinical repercussions, such as in changing the initial diagnosis, identifying or excluding different causes of painful knee arthroplasties, guiding subsequent treatment and positively impacting the final clinical outcome. We moderately recommend the use of SPECT/CT for identifying the source of pain after knee arthroplasty according to the GRADE assessment. This review was preregistered in Prospero under code CRD42022320457.

Could Novel Radiographic Findings Help Identify Aseptic Tibial Loosening?

BACKGROUND

Aseptic loosening following total knee arthroplasty remains one of the leading causes of long-term failure. Radiographic identification of loose implants can be challenging with standard views. The purpose of this study was to compare the incidence of novel radiographic findings of anterior heterotopic bone formation and medial or lateral cyst formation in patients who have aseptic loosening to patients who have well-fixed implants.

METHODS

A retrospective radiographic review was performed on 48 patients' revised secondary to aseptic tibial loosening. This cohort was compared to two additional cohorts; 48 patients returning for routine postoperative follow-up (control 1), and 48 patients revised secondary to infection or instability who had well-fixed implants (control 2).

RESULTS

There were 41 of 48 (85%) patients who had implant loosening and were noted to have anterior heterotopic bone formation compared to 1 of 48 (2%) patients in control 1 and 3 of 48 (6%) patients in control 2 (P ≤ .0001). There were 43 of 48 (90%) patients who had implant loosening and had medial cyst formation compared to 3 of 48 (6%) patients in control 1 and 5 of 48 (10%) in control 2 (P ≤ .0001). There were 42 of 48 (88%) patients who had implant loosening and had lateral cyst formation compared to 2 of 48 (4%) patients in control 1 and 4 of 48 (8%) in control 2 (P ≤ .0001).

CONCLUSION

In this study, we describe novel radiographic findings of anterior heterotopic bone formation and cysts that develop in patients who have aseptic loosening following primary total knee arthroplasty. We believe that these radiographic features may lead to easier identification of aseptic loosening.

A novel image-based machine learning model with superior accuracy and predictability for knee arthroplasty loosening detection and clinical decision making

Background

Loosening is the leading cause of total knee arthroplasty (TKA) revision. This is a heavy burden toward the healthcare system owing to the difficulty in diagnosis and complications occurring from the delay management. Based on automatic analytical model building, machine learning, may potentially help to automatically recognize the risk of loosening based on radiographs alone. The aim of this study was to build an image-based machine-learning model for detecting TKA loosening.

Methods

Image-based machine-learning model was developed based on ImageNet, Xception model and a TKA patient X-ray image dataset. Based on a dataset with TKA patient clinical parameters, another system was then created for developing the clinical-information-based machine learning model with random forest classifier. In addition, the Xception Model was pre-trained on the ImageNet database with python and TensorFlow deep learning library for the prediction of loosening. Class activation maps were also used to interpret the prediction decision made by model. Two senior orthopaedic specialists were invited to assess loosening from X-ray images for 3 attempts in setting up comparison benchmark.

Result

In the image-based machine learning loosening model, the precision rate and recall rate were 0.92 and 0.96, respectively. While for the accuracy rate, 96.3% for visualization classification was observed. However, the addition of clinical-information-based model, with precision rate of 0.71 and recall rate of 0.20, did not further showed improvement on the accuracy. Moreover, as class activation maps showed corresponding signals over bone-implant interface that is loosened radiographically, this confirms that the current model utilized a similar image recognition pattern as that of inspection by clinical specialists.

Conclusion

The image-based machine learning model developed demonstrated high accuracy and predictability of knee arthroplasty loosening. And the class activation heatmap matched well with the radiographic features used clinically to detect loosening, which highlighting its potential role in assisting clinicians in their daily practice. However, addition of clinical-information-based machine-learning model did not offer further improvement in detection. As far as we know, this is the first report of pure image-based machine learning model with high detection accuracy. Importantly, this is also the first model to show relevant class activation heatmap corresponding to loosening location.

Translational potential

The finding in this study indicated image-based machine learning model can detect knee arthroplasty loosening with high accuracy and predictability, which the class activation heatmap can potentially assist surgeons to identify the sites of loosening.

Osteoimmunomodulation role of exosomes derived from immune cells on osseointegration

Despite the high success rate of biomedical implants adopted clinically, implant failures caused by aseptic loosening still raise the risk of secondary surgery and a substantial economic burden to patients. Improving the stable combination between the implant and the host bone tissue, achieving fast and high-quality osseointegration can effectively reduce the probability of aseptic loosening. Accumulating studies have shown that the osteoimmunomodulation mediated by immune cells mainly dominated by macrophages plays a pivotal role in osseointegration by releasing active factors to improve the inflammatory microenvironment. However, the mechanism by which osteoimmunomodulation mediates osseointegration remains unclear. Recent studies have revealed that exosomes released by macrophages play a central role in mediating osteoimmunomodulation. The exosomes can be internalized by various cells participating in de novo bone formation, such as endothelial cells and osteoblasts, to intervene in the osseointegration robustly. Therefore, macrophage-derived exosomes with multifunctionality are expected to significantly improve the osseointegration microenvironment, which is promising in reducing the occurrence of aseptic loosening. Based on this, this review summarizes recent studies on the effects of exosomes derived from the immune cells on osseointegration, aiming to provide a theoretical foundation for improving the clinical success rate of biomedical implants and achieving high-quality and high-efficiency osseointegration.

Material parameters identification of 3D printed titanium alloy prosthesis stem based on response surface method

3D printed Titanium alloy is widely used as a material of artificial joints and its mechanical properties is a key factor for improving operation results. Because the elastic modulus of the 3 D printed titanium alloy specimen was related to the size of the metal blank. It is very difficult to identify mechanical parameters by traditional mechanics experiments. In this paper, according to the inverse analysis principle of the parameter estimation, a response surface methodology (RSM) was proposed to identify the mechanical parameters, based on finite element inverse analysis. The finite element models of femoral prosthesis stem were established in line with compression experiments. The material parameters were combined by central composite design (CCD), and the response surface (RS) models were constructed using a quadratic polynomial with cross terms and optimized using a genetic algorithm (GA). Finally, the best mechanical parameter combination of the femoral prosthesis was calculated. The calculated elastic modulus and Poisson's ratio of a 3 D printed titanium alloy femoral prosthesis stem were 109.07 GPa and 0.29, respectively, with the elastic modulus error being very small. The proposed method is effective and can be extended for the identification of mechanical parameters in other 3 D printed models.

High rate of tibial debonding and failure in a popular knee replacement

Aims

Total knee arthroplasty (TKA) is a common and safe orthopaedic procedure. Zimmer Biomet's NexGen is the second most popular brand of implant used in the UK. The primary cause of revision after the first year is aseptic loosening. We present our experience of using this implant, with significant concerns around its performance with regards early aseptic loosening of the tibial component.

Methods

A retrospective, single-surgeon review was carried out of all of the NexGen Legacy Posterior Stabilized (LPS) TKAs performed in this institute. The specific model used for the index procedures was the NexGen Complete Knee System (Legacy Knee-Posterior Stabilized LPS-Flex Articular Surface, LPS-Flex Femoral Component Option, and Stemmed Nonaugmentable Tibial Component Option).

Results

Between 2013 and 2016, 352 NexGen TKAs were carried out on 331 patients. A total of 62 TKAs have been revised to date, giving an all-cause revision rate of 17.6% at a minimum of five years. Three of these revisions were due to infection. Overall, 59 of the revisions were performed for aseptic loosening (16.7%) of the tibial component. The tibial component was removed intraoperatively without instrumentation due to significant tibial debonding between the implant-cement interface.

Conclusion

While overall, we believe that early aseptic loosening is multi-factorial in nature, the significantly high aseptic revision rate, as seen by an experienced fellowship-trained arthroplasty surgeon, has led us to believe that there is a fundamental issue with this NexGen implant design. Continued implant surveillance and rigorous review across all regions using this particular implant is warranted based on the concerning findings described here.

Cite this article: Bone Jt Open 2022;3(6):495–501.

Are cementation quality and clinical outcomes affected by the use of tourniquet in primary total knee arthroplasty?

INTRODUCTION

Total knee arthroplasty is used to treat end-stage knee osteoarthritis with great results. Tourniquet use has become popular over the years because of its various benefits, but the literature regarding functional outcomes, pain and rehabilitation and comparison between tourniquet use and improvement cement penetration and overall improve fixation is limited. The authors proposed a hypothesis that cementation quality, and clinical outcomes can be influenced by tourniquet technique.

METHODS

Fifty patients were allocated randomly in two groups: (1) tourniquet was inflated throughout all the procedure and (2) only during skin incision and cementation. Radiolucent lines were analyzed by two and independent examiners, using the The Knee Society Roentgenographic Evaluation and Scoring System. The functional scores used were the Oxford knee score and improvement in visual pain scale (VAS).

RESULTS

After a mean follow-up period of 2.4 ± 0.2 years, no difference was observed regarding partial use of tourniquet in the cementation quality (p value > 0.05). There was no difference between groups regarding gender, age, knee side, Visual VAS, Oxford Score, total range-of-motion (ROM), knee extension and knee flexion (p value > 0.05).

CONCLUSIONS

No difference was attained regarding functional outcomes and cementation quality regarding two different tourniquet protocols.

Diagnostic Performance of MRI for Component Loosening in Total Knee Arthroplasty Compared with Radiography

Background Because loosening of total knee arthroplasty (TKA) occurs due to poor osseous integration at component-bone interfaces, interface assessment may be helpful in diagnosing loosening at MRI. Purpose To determine interreader reproducibility for characterizing component interfaces and diagnosing loosening and to evaluate the diagnostic performance of MRI for diagnosing loosening after TKA compared with radiography. Materials and Methods Consecutive knees with TKA that underwent revision between July 2018 and June 2019 and were imaged at MRI and radiography were included in this retrospective study. Interface type (normal, fibrous membrane, fluid, or osteolysis), percent integration (<33%, 33%-66%, or >66%), and presence of bone marrow edema pattern were assessed. Loosening was diagnosed at MRI if no or almost no normal interface was present. Sensitivity and specificity were compared with radiographs by using surgical findings as reference. Gwet agreement coefficient evaluated interreader reproducibility between two readers and multivariable logistic regression assessed risk factors for loosening. Results Among 116 knees in 114 patients (mean age, 63 years ± 10 [SD]; 59 women), 61 of 116 knees (52.6%) had at least one loose component. Interreader reproducibility of MRI was substantial to excellent (Gwet agreement coefficient, 0.67-0.96). Loosening was associated with fluid interface (odds ratio [OR], 20.1; 95% CI: 5.7, 70.9) or osteolysis (OR, 3.1; 95% CI: 1.8, 5.3), absence of any normal interface (OR, 11.8; 95% CI: 6.3, 22.2), poor (<33%) osseous integration (OR, 20.4; 95% CI: 9.7, 42.6), and bone marrow edema pattern (OR, 4.7; 95% CI: 2.8, 7.8). Sensitivity and specificity of MRI for loosening were 84% (27 of 32; 95% CI: 72, 97) and 85% (71 of 84; 95% CI: 77, 92) for the patellar, 31% (eight of 26; 95% CI: 13, 49) and 100% (90 of 90; 95% CI: 100, 100) for the femoral, and 81% (22 of 27; 95% CI: 66, 96) and 98% (87 of 89; 95% CI: 95, 100) for the tibial component, respectively. MRI had higher sensitivity (84% vs 31%; P < .001) but lower specificity (85% vs 96%; P = .003) for patellar component loosening than did radiography, respectively, whereas no evidence of a difference was found for femoral (sensitivity and specificity, MRI vs radiography: 31% vs 46% [P = .20] and 100% vs 99% [P > .99], respectively) or tibial (sensitivity and specificity, MRI vs radiography: 81% vs 70% [P = .16] and 98% vs 97% [P = .32], respectively) component loosening. Conclusion MRI demonstrated substantial to excellent interreader reproducibility and higher sensitivity than did radiography for diagnosing patellar component loosening after total knee arthroplasty. © RSNA, 2022 Online supplemental material is available for this article.

Biomaterials-Driven Sterile Inflammation

Performance of the biomaterials used for regenerative medicine largely depends on biocompatibility; however, the biological mechanisms underlying biocompatibility of a biomaterial within the host system is poorly understood. In addition to the classical immune response against non-self-entities, the sterile inflammatory response could limit the compatibility of biological scaffolds. Whereas the immediate to short-term host response to a biomaterial implant have been characterized, the long-term progression of host-biomaterial relationship has not been described. This article explores the novel concept of biomaterials-driven sterile inflammation (BSI) in long-term biodegradable implants and throws light for possible explanation for the onset of BSI and the associated damage-associated molecular patterns. The understanding of BSI would advance the current strategies to improve biomaterial-host tissue integration and open novel translational avenues in biomaterials-based tissue regeneration. Impact statement Understanding the novel concept of biomaterials-driven sterile inflammation and associated damage-associated molecular patterns in long-term biodegradable implants would determine their success and improves the tissue engineering and regenerative strategies.

Diagnostic Performance of Single-Photon Emission Computed Tomography/Computed Tomography in Aseptic Loosening: A Systematic Review and Meta-Analysis

BACKGROUND

The aim of this study is to evaluate the diagnostic value and clinical applicability of single-photon emission computed tomography/computed tomography (SPECT/CT) in aseptic loosening (AL) of prostheses by meta-analysis.

METHOD

Literature on the diagnostic value of SPECT/CT in AL of prostheses was obtained by computer and manual review. The quality of the included studies was evaluated according to the Quality Assessment Diagnostic Accuracy Studies 2. Pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio, and other indicators were calculated, and a forest map and summary receiver operating characteristic were drawn to calculate the area under the curve. Meta-regression analysis was performed to identify the sources of heterogeneity and corresponding subgroup analysis was performed. A Fagan plot, likelihood ratio point plot, and Deek's funnel plot were drawn and analyzed.

RESULTS

A total of 15 studies were included. The meta-analysis results showed that the pooled sensitivity and specificity of SPECT/CT for the diagnosis of aseptic prosthetic loosening were 0.94, 95% confidence interval [CI] (0.90-0.96) and 0.89, 95% CI (0.78-0.95), respectively while the pooled positive likelihood ratio and pooled negative likelihood ratio were 8.65, 95% CI (4.18-17.90) and 0.07, 95% CI (0.04-0.11), respectively. The pooled diagnostic odds ratio was 130.36, 95% CI (45.18-376.19), and the area under the curve was 0.97, 95% CI (0.95-0.98).

CONCLUSION

As a diagnostic method for AL, SPECT/CT has high diagnostic sensitivity and specificity as well as high diagnostic efficiency. It has good clinical application value and should be a primary choice in the diagnosis of AL after joint replacement.

[Diagnosis of loosening after knee arthroplasty]

BACKGROUND

Aseptic loosening is one of the most common reasons for revision in knee arthroplasty. Its pathogenesis is multifactorial, and early diagnosis is necessary to initiate appropriate therapy and to avoid serious complications, such as substantial bone loss or even periprosthetic fractures.

OBJECTIVES

This paper describes the current standard in the diagnosis of aseptic loosening in total knee arthroplasty. Sensitivity and specificity of the individual diagnostic procedures are presented, and other causes for differential diagnoses of painful total knee arthroplasty (TKA) are discussed.

RESULTS

In the case of suspected loosening in TKA, infection diagnostics should be performed to rule out periprosthetic infection, as this is crucial in terms of surgical strategy. The gold standard in diagnosing aseptic loosening is conventional radiography. Radiolucent lines at the cement-bone or metal-cement interface of more than 2 mm or increasing in translucency, migration of components, and cement fractures are obvious signs of loosening. Artifact-reduced computed tomography can bring additional information regarding periprosthetic osteolysis. A single bone scan is not reliable in diagnosing aseptic loosening, especially in the first 2 years after surgery. Single photon emission computed tomography (SPECT-CT) could be a useful extension in loosening diagnosis in the future.

CONCLUSIONS

The diagnosis of aseptic loosening poses a great challenge to the treating physician and requires a structured diagnostic algorithm. After exclusion of infection, conventional radiography is the basic examination, which should be supplemented by computed tomography and nuclear medicine examinations according to the clinical symptoms and the time course.

Accuracy comparison of various quantitative [99mTc]Tc-DPD SPECT/CT reconstruction techniques in patients with symptomatic hip and knee joint prostheses

BACKGROUND

There is a need for better diagnostic tools that identify loose total hip and knee arthroplasties. Here, we present the accuracy of different 99mTc-dicarboxypropandiphosphate ([99mTc]Tc-DPD) SPECT/CT quantification tools for the detection of loose prostheses in patients with painful hip and knee arthroplasties.

METHODS

Quantitative reconstruction of mineral phase SPECT data was performed using Siemens xSPECT-Quant and xSPECT-Bone, with and without metal artefact reduction (iMAR) of CT-data. Quantitative data (SUVmax values) were compared to intraoperative diagnosis or clinical outcome after at least 1 year as standard of comparison. Cut-off values and accuracies were calculated using receiver operator characteristics. Accuracy of uptake quantification was compared to the accuracy of visual SPECT/CT readings, blinded for the quantitative data and clinical outcome.

RESULTS

In this prospective study, 30 consecutive patients with 33 symptomatic hip and knee prostheses underwent [99mTc]Tc-DPD SPECT/CT. Ten arthroplasties were diagnosed loose and 23 stable. Mean-SUVmax was significantly higher around loose prostheses compared to stable prostheses, regardless of the quantification method (P = 0.0025-0.0001). Quantification with xSPECT-Bone-iMAR showed the highest accuracy (93.9% [95% CI 79.6-100%]) which was significantly higher compared to xSPECT-Quant-iMAR (81.8% [67.5-96.1%], P = 0.04) and xSPECT-Quant without iMAR (77.4% [62.4-92.4%], P = 0.02). Accuracies of clinical reading were non-significantly lower compared to quantitative measures (84.8% [70.6-99.1%] (senior) and 81.5% [67.5-96.1%] (trainee)).

CONCLUSION

Quantification with [99mTc]Tc-DPD xSPECT-Bone-iMAR discriminates best between loose and stable prostheses of all evaluated methods. The overall high accuracy of different quantitative measures underlines the potential of [99mTc]Tc-DPD-quantification as a biomarker and demands further prospective evaluation in a larger number of prosthesis.

Diagnostic accuracy of SPECT/CT arthrography in patients with suspected aseptic joint prostheses loosening

Purpose

To evaluate the diagnostic accuracy of SPECT/CT arthrography in patients with suspected aseptic prosthesis loosening following hip and knee arthroplasty.

Methods

A retrospective review of 63 SPECT/CT arthrogram studies (36 knees and 27 hips) between February 1, 2013, and July 1, 2018, was conducted. All patients underwent clinical and radiologic evaluation as part of their assessment for persistent pain following hip and knee arthroplasty. The detection of tracer activity along the bone-prosthetic interface on SPECT/CT suggests aseptic loosening. Operative assessment as well as clinical/radiologic follow-up at a minimum of 1 year was used as the reference standard.

Results

The sensitivity and specificity of SPECT/CT for detection of aseptic loosening was 6/7 (86%) and 55/56 (98%), respectively. This gives a positive predictive value (PPV) of 6/7 (86%), a negative predictive value (NPV) of 55/56 (98%), and a diagnostic accuracy of 61/63 (97%).

Conclusion

SPECT/CT arthrography has a high diagnostic accuracy (97%) in the evaluation of loosening of both hip and knee arthroplasties in patients with persistent post-procedural pain.

Simple Smart Implants: Simultaneous Monitoring of Loosening and Temperature in Orthopaedics With an Embedded Ultrasound Transducer

Implant failure can have devastating consequences on patient outcomes following joint replacement. Time to diagnosis affects subsequent treatment success, but current diagnostics do not give early warning and lack accuracy. This research proposes an embedded ultrasound system to monitor implant fixation and temperature - a potential indicator of infection. Requiring only two implanted components: a piezoelectric transducer and a coil, pulse-echo responses are elicited via a three-coil inductive link. This passive system avoids the need for batteries, energy harvesters, and microprocessors, resulting in minimal changes to existing implant architecture. Proof-of-concept was demonstrated in vitro for a titanium plate cemented into synthetic bone, using a small embedded coil with 10 mm diameter. Gross loosening - simulated by completely debonding the implant-cement interface - was detectable with 95% confidence at up to 12 mm implantation depth. Temperature was calibrated with root mean square error of 0.19°C at 5 mm, with measurements accurate to ±1°C with 95% confidence up to 6 mm implantation depth. These data demonstrate that with only a transducer and coil implanted, it is possible to measure fixation and temperature simultaneously. This simple smart implant approach minimises the need to modify well-established implant designs, and hence could enable mass-market adoption.

Reasons for failure in primary total knee arthroplasty - An analysis of prospectively collected registry data

Objective

The aim of this study was to determine the causes leading to a first revision of primary total knee arthroplasty (TKA) in a specialized knee centre and compare the results with previously published data.

Methods

Prospectively collected data of a consecutive number of 195 patients after primary TKA and who underwent first revision surgery after completing the diagnostic algorithm for persistent knee pain were included. Data was prospectively collected from a specialized knee centre in which the patients presented between 2015 and 2020 and retrospectively analysed. Indications for revision surgery were categorized using all available information from patients' records. Patients were divided into early (up to two years) and late revision (more than two years).

Results

Overall mean time from index to revision surgery was 3.6 years. 49% of knee revisions occurred in the first two years, 51% after two years. 86% of the patients were referred to the knee centre from other surgeons. The most frequent reason for revision was instability, followed by patellofemoral problems, extensor mechanism insufficiency and malalignment. The most frequently performed revision was complete removal and re-implantation of a semi constrained implant design (52.5%) followed by revision using a full constrained implant design (16%). Secondary patella-resurfacing as part of complete revision was carried out in 71.5% of the cases. The majority of the patients showed concurrent reasons for TKA failure with significant correlations amongst another. Furthermore, correlations were identified between indications for revision surgery and revision implant designs.

Conclusion

In a specialized knee centre the most common indications for the first TKA revision were instability and patellofemoral and/or extensor mechanism insufficiency followed by malalignment. In most patients there was not only one failure mode, but a combination of many. It is important to establish a standardized diagnostic algorithm to facilitate comprehensive and efficient diagnostics and the optimal treatment.

Why do knees after total knee arthroplasty fail in different parts of the world?

Objective

The aim of this narrative review was to provide an overview of failure modes after total knee arthroplasty in different parts of the world based on data from worldwide representative studies and National Joint Registries.

Methods

A review of the available literature was performed using the keyword terms “total knee arthroplasty”, “revision”, “failure”, “reasons”, “causes”, “complications”, “epidemiology”, “etiology”; “assessment”, “painful knee”, “registry” and “national” in several combinations. The following databases were assessed: Pubmed (https://pubmed.ncbi.nlm.nih.gov), Cochrane Reviews (https://www.cochrane.org), Google Scholar (https://scholar.google.com). In addition, registry data were obtained directly from national registry archives. Due to the heterogeneity of available data it was decided to present the review in a narrative manner.

Results

Current literature report that infection has become the primary acute cause of TKA failure, while aseptic loosening and instability remain the overall most frequent reasons for revisions. Based on national registries certain tendencies can be deducted. The predominant overall failure mode of aseptic loosening is particularly found in Japan, United Kingdom, New Zealand and Switzerland. Leading early TKA failure mode represents infection with percentages of 20–30% in Sweden, Australia, New Zealand, Japan and the United States. Higher numbers could only be found in clinical studies on the Asian continent such as Korea (38%), China (53%), Iran (44%) and India (87%).

Conclusion

Although there are regional differences in TKA failure modes, TKA fails worldwide especially due to infections and aseptic loosening. It is important to diagnose these in good time and reliably using appropriate, standardized diagnostics in order to recommend the best possible therapy to the patient.