Radiographic Evaluations of Revision Total Knee Arthroplasty: A Plea for Uniform Assessments

Novel dilation-erosion labeling technique allows for rapid, accurate and adjustable alignment measurements in primary TKA

BACKGROUND

Optimal implant position and alignment remains a controversial, yet critical topic in primary total knee arthroplasty (TKA). Future study of ideal implant position will require the ability to efficiently measure component positions at scale. Previous algorithms have limited accuracy, do not allow for human oversight and correction in deployment, and require extensive training time and dataset. Therefore, the purpose of this study was to develop and validate a machine learning model that can accurately automate, with surgeon directed adjustment, implant position annotation.

METHODS

A retrospective series of 295 primary TKAs was identified. The femoral-tibial angle (FTA), distal femoral angle (dFA), and proximal tibial angle (pTA) were manually annotated from the immediate short leg post-op radiograph. We then trained a neural network to predict each annotated landmark using a novel label augmentation procedure of dilation, reweighting, and scheduled erosion steps. The model was compared against diverse models and accuracy was assessed using a validation set of 43 patients and test set of 79 patients.

RESULTS

Our proposed model significantly improves accuracy compared to baseline training models across all measures in ten out of eleven cases (p < 1e-22 for each measure). The mean absolute error (difference from manual annotation) was 0.65° for FTA, 1.62° for dFA, and 1.44° for pTA.

CONCLUSION

Utilizing a novel algorithm, trained on a limited dataset, the accuracy of component position was approximately 1.2°. Additionally, the model outputs adjustable points from which the angles are calculated, allowing for clinician oversight and interpretable diagnostics for failure cases.

Radiolucent lines and revision risk in total knee arthroplasty using the conventional versus the Attune S+ tibial baseplate

Aims

This multicentre retrospective observational study's aims were to investigate whether there are differences in the occurrence of radiolucent lines (RLLs) following total knee arthroplasty (TKA) between the conventional Attune baseplate and its successor, the novel Attune S+, independent from other potentially influencing factors; and whether tibial baseplate design and presence of RLLs are associated with differing risk of revision.

Methods

A total of 780 patients (39% male; median age 70.7 years (IQR 62.0 to 77.2)) underwent cemented TKA using the Attune Knee System) at five centres, and with the latest radiograph available for the evaluation of RLL at between six and 36 months from surgery. Univariate and multivariate logistic regression models were performed to assess associations between patient and implant-associated factors on the presence of tibial and femoral RLLs. Differences in revision risk depending on RLLs and tibial baseplate design were investigated with the log-rank test.

Results

The conventional and novel Attune baseplates were used in 349 (45%) and 431 (55%) patients, respectively. At a median follow-up of 14 months (IQR 11 to 25), RLLs were present in 29% (n = 228/777) and 15% (n = 116/776) of the tibial and femoral components, respectively, and were more common in the conventional compared to the novel baseplate. The novel baseplate was independently associated with a lower incidence of tibial and femoral RLLs (both regardless of age, sex, BMI, and time to radiograph). One- and three-year revision risk was 1% (95% CI 0.4% to 1.9%)and 6% (95% CI 2.6% to 13.2%), respectively. There was no difference between baseplate design and the presence of RLLs on the the risk of revision at short-term follow-up.

Conclusion

The overall incidence of RLLs, as well as the incidence of tibial and femoral RLLs, was lower with the novel compared to the conventional tibial Attune baseplate design, but higher than in the predecessor design and other commonly used TKA systems.

Epiphyseal fixation in revision total knee arthroplasty: a comparison between trabecular metal and titanium augments

INTRODUCTION

The purpose of this retrospective study was to compare the medium-term clinical and radiographic outcomes of two series of patients treated for revision TKA: one implanted with trabecular metal (TM) augments and one implanted with classic titanium augments.

MATERIALS AND METHODS

A total of 85 patients with a type 2 AORI defect underwent revision TKA and were treated either with TM epiphyseal augments directly screwed in the bone or with traditional titanium augments. There were 46 patients in the TM group and 39 patients in the titanium group included in the study. All the patients received the same varus-valgus constrained implant and no metaphyseal fixation devices were used.

RESULTS

After a mean follow-up of 66.4 months, no statistically significant difference was observed in terms of failure for aseptic loosening between the two groups (4% in the TM group and 7.8% in the titanium group, p = 0.35). The ten-year survival using aseptic loosening as endpoint was 90.5% (95% CI 94.1-98.6) in the TM group and 85% (95% CI 101.9-119.3) in the titanium group (p = 0.26). A statistically significant difference was detected for the presence of RLL. No RLL were found under the studied TM augments compared to 13.7% of the titanium augments (p = 0.01).

CONCLUSION

The use of TM augments directly screwed to the epiphysis of the femur and the tibia reduced the incidence of RLL compared to standard titanium augments during revision TKA with promising medium-term results.

Less Induction Time and Postoperative Pain Using Spinal Anesthesia Versus General Anesthesia With or Without the Use of Peripheral Nerve Blocks in Total Knee Arthroplasty

BACKGROUND

Our aim was to analyze anesthetic induction time and postoperative pain using spinal anesthesia versus general anesthesia with or without the use of peripheral nerve blocks (PNBs) in total knee arthroplasty. The hypothesis was that spinal anesthesia would be beneficial with respect to induction time and postoperative pain and that PNBs would complement this effect.

METHODS

Patients were stratified according to demographics, American Society of Anesthesiologists physical status classification system (ASA), and opioid intake and divided into: (A) general anesthesia without PNB; (B) general anesthesia with PNB; (C) spinal anesthesia without PNB; and (D) spinal anesthesia with PNB. Endpoints were anesthetic induction time, opioid consumption, and pain. Of 559 patients, 348 (62.3%) received general anesthesia (consisting of group A with 46 and group B with 302 patients), and 211 (37.7%) spinal anesthesia (consisting of group C with 117 and group D with 94 patients).

RESULTS

We observed significantly lower total opioid intake 48 hours postoperative when applying spinal anesthesia by 2.08 mg (P < .05) of intravenous morphine-equivalent, and a reduction of 7.0 minutes (P < .05) until skin incision. The application of a PNB achieved a reduction of piritramide intake of 3.59 mg (P < .05) 48 hours postoperative and lengthened induction time by 8.5 minutes (P < .05).

CONCLUSIONS

Statistically shorter anesthetic induction times without clinical relevance, but lower postoperative opioid dosages with clinical relevance were observed for patients undergoing total knee arthroplasty with spinal anesthesia. The additional application of PNBs led to a lower need for opioids and lower pain levels in the early postoperative phase.

Radiolucent line assessment in cemented stemmed total knee (RISK) arthroplasty: validation of a modernized classification system

BACKGROUND

This study aims to implement and assess the inter- and intra-reliability of a modernized radiolucency assessment system; the Radiolucency In cemented Stemmed Knee (RISK) arthroplasty classification. Furthermore, we assessed the distribution of regions affected by radiolucency in patients undergoing stemmed cemented total knee arthroplasty.

METHODS

Stemmed total knee arthroplasty cases over 7-year period at a single institution were retrospectively identified and reviewed. The RISK classification system identifies five zones in the femur and five zones in the tibia in both the anteroposterior (AP) and lateral planes. Post-operative and follow-up radiographs were scored for radiolucency by four blinded reviewers at two distinct time points four weeks apart. Reliability was assessed using the kappa statistic. A heat map was generated to demonstrate the reported regions of radiolucency.

RESULTS

29 cases (63 radiographs) of stemmed total knee arthroplasty were examined radiographically using the RISK classification system. Intra-reliability (0.83) and Inter-reliability (0.80) scores were both consistent with a strong level of agreement using the kappa scoring system. Radiolucency was more commonly associated with the tibial component (76.6%) compared to the femoral component (23.3%), and the tibial anterior-posterior (AP) region 1 (medial plateau) was the most affected (14.9%).

CONCLUSION

The RISK classification system is a reliable assessment tool for evaluating radiolucency around stemmed total knee arthroplasty using defined zones on both AP and lateral radiographs. Zones of radiolucency identified in this study may be relevant to implant survival and corresponded well with zones of fixation, which may help inform future research.

Does lucency equate to revision? A five-year retrospective review of Attune and Triathlon total knee arthroplasty

PURPOSE

The Attune® total knee arthroplasty system was introduced in 2013 to address lingering issues of patient dissatisfaction. However, recent literature reports concerns of early tibial tray debonding. The aim of this study was to compare the incidence of radiolucent lines, survivorship and patient reported outcome-measures between the Attune® system and the well-established Triathlon® system.

METHODS

This retrospective database review was conducted at a single institution in Cork, Ireland. All primary Attune® (N = 445) and Triathlon® (N = 285) systems implanted between 2015 and 2016 were reviewed. Radiolucent lines were assessed for those with a minimum two-year radiological follow-up (Attune® = 338; Triathlon® = 231). X-rays were taken post op, at 6 months, 2 years and 5 years. Radiolucent lines were documented using the Modern Knee Society Radiographic System. Five-year survival was assessed using Kaplan-Meier analysis with the Log Rank method to determine statistical significance. The Oxford Knee Score and EQ-5D-5L, were collected pre-op, at 6 months, 2 years and 5 years post-operatively and compared using the Kruskal-Wallis Test.

RESULTS

The Attune® had a higher proportion of radiolucent lines at the tibial tray [87.1% (54/62) vs 61.4% (27/44); p = 0.001] and at the implant-cement interface [62.9% (39/62) vs 43.2% (19/44); p = 0.02]. Conversely, the Triathlon® had a higher proportion AT the femur [38.6% (17/44) vs 12.9% (8/62); p = 0.001] and at the cement-bone interface [56.8% (25/44) vs 37.1% (23/62); p = 0.02]. The overall frequency of radiolucent lines was similar in both the Attune® and Triathlon® groups [17.8%, (60/338) vs 17.7%, (41/231); p = 0.49]. There was no difference in revision-free survival analysis at 5 years (Attune® 97.8% vs Triathlon® 95.8%; p = 0.129). The Attune® performed better at 5 years in the Oxford Knee Score [Attune® = 42.6 (SD 5.2) vs Triathlon® = 41 (SD 6.4); p = 0.001] and in the EQ-5D [Attune® = 0.773 (SD 0.187) vs Triathlon® = 0.729 (SD 0.218); p = 0.013]. There was no difference at 5 years in the EQ-VAS [Attune® = 80.4 (SD 13.7) vs Triathlon® = 78.5 (SD 15.3); p = 0.25].

CONCLUSION

The Attune® system exhibited a higher incidence of  radiolucent lines at the tibial tray. However, this did not lead to decreased survivorship at medium term follow-up compared to the Triathlon®. Furthermore, improvements in patient reported outcomes modestly favoured the Attune® system.

LEVEL OF EVIDENCE

III.

Total hip arthroplasty for hip fractures in patients older than 80 years of age: a retrospective matched cohort study

INTRODUCTION

Increasing age and hip fractures are considered risk factors for post-operative complications in total hip arthroplasty (THA). Consequently, older adults undergoing THA due to hip fracture may have different outcomes and require additional healthcare resources than younger patients. This study aimed to identify the influence of age on discharge disposition and 90-day outcomes of THA performed for hip fractures in patients ≥ 80 years to those aged < 80.

MATERIALS AND METHODS

A retrospective review of 344 patients who underwent primary THA for hip fracture from 2011 to 2021 was conducted. Patients ≥ 80 years old were propensity-matched to a control group < 80 years old. Patient demographics, length of stay (LOS), discharge disposition, and 90-day post-operative outcomes were collected and assessed using Chi-square and independent sample t tests.

RESULTS

A total of 110 patients remained for matched comparison after propensity matching, and the average age in the younger cohort (YC, n = 55) was 67.69 ± 10.48, while the average age in the older cohort (OC, n = 55) was 85.12 ± 4.77 (p ≤ 0.001). Discharge disposition differed between the cohorts (p = 0.005), with the YC being more likely to be discharged home (52.7% vs. 27.3%) or to an acute rehabilitation center (23.6% vs. 16.4%) and less likely to be discharged to a skilled nursing facility (21.8% vs. 54.5%). 90-day revision (3.6% vs. 1.8%; p = 0.558), 90-day readmission (10.9% vs. 14.5%; p = 0.567), 90-day complications (p = 0.626), and 90-day mortality rates (1.8% vs 1.8%; p = 1.000) did not differ significantly between cohorts.

CONCLUSION

While older patients were more likely to require a higher level of post-hospital care, outcomes and perioperative complication rates were not significantly different compared to a younger patient cohort. Payors need to consider patients' age in future payment models, as discharge disposition comprises a large percentage of post-discharge expenses.

LEVEL OF EVIDENCE

Level III, Retrospective Cohort Study.

Bone defect classifications in revision total knee arthroplasty, their reliability and utility: a systematic review

BACKGROUND

There are various classification systems described in the literature for managing bone defects in revision knee arthroplasty (RTKA). We analysed the reliability and usefulness of these classification systems.

QUESTIONS/PURPOSES

(1) To review and critique the various classification systems proposed for bone loss in RTKA. (2) Among all the proposed classifications which one is the most commonly used by surgeons to report their results. (3) What is the reliability of various bone defect classification systems for RTKA. In this review, we have assessed the studies validating those classifications with a detailed description of the limitations and the proposed modifications.

METHODS

This systematic review was conducted following PRISMA guidelines. Pubmed/Medline, CINAHL, EMBASE, Scopus, Cochrane databases and Web of Science databases were searched using multiple search terms and MeSH terms where possible. Studies meeting inclusion criteria were assessed for statistical parameters of reliability of a classification system.

RESULTS

We found 16 classification systems for bone defects in RTKA. Six studies were found evaluating a classification system with reporting their reliability parameters. Fifty-four studies were found which classified bone loss using AORI classification in their series. AORI classification is most commonly reported for classifying bone defects. Type T2B and F2B are the most common bone defects in RTKA. The average kappa value for AORI classification for femoral bone loss was 0.38 (0.27-0.50) and 0.76 (0.63-1) for tibial bone loss assessment.

CONCLUSION

None of the available classification systems is reliably established in determining the bone loss and treatment plans in RTKA. Among all, AORI classification is the most widely used system in clinical practice. The reliability of AORI Classification is fair for femoral bone loss and substantial for tibial bone loss.

Unexpected high rate of revision of a modern cemented fixed bearing modular posterior-stabilized knee arthroplasty

AIMS

To establish our early clinical results of a new total knee arthroplasty (TKA) tibial component introduced in 2013 and compare it to other designs in use at our hospital during the same period.

METHODS

This is a retrospective study of 166 (154 patients) consecutive cemented, fixed bearing, posterior-stabilized (PS) TKAs (ATTUNE) at one hospital performed by five surgeons. These were compared with a reference cohort of 511 knees (470 patients) of other designs (seven manufacturers) performed at the same hospital by the same surgeons. There were no significant differences in age, sex, BMI, or follow-up times between the two cohorts. The primary outcome was revision performed or pending.

RESULTS

In total, 19 (11.5%) ATTUNE study TKAs have been revised at a mean 30.3 months (SD 15), and loosening of the tibial component was seen in 17 of these (90%). Revision is pending in 12 (7%) knees. There was no difference between the 31 knees revised or with revision pending and the remaining 135 study knees in terms of patient characteristics, type of bone cement (p = 0.988), or individual surgeon (p = 0.550). In the reference cohort, there were significantly fewer knees revised (n = 13, 2.6%) and with revision pending (n = 8, 1.5%) (both p < 0.001), and only two had loosening of the tibial component as the reason for revision.

CONCLUSION

This new TKA design had an unexpectedly high early rate of revision compared with our reference cohort of TKAs. Debonding of the tibial component was the most common reason for failure. Additional longer-term follow-up studies of this specific component and techniques for implantation are warranted. The version of the ATTUNE tibial component implanted in this study has undergone modifications by the manufacturer. Cite this article: Bone Joint J 2021;103-B(6 Supple A):137-144.

Fluoroscopic Intraoperative Images Produce Higher Image Quality and Decrease Total Radiation Exposure Compared to Radiographic X-ray Images in Patients After Primary Total Knee Arthroplasty

BACKGROUND/AIM

Proper radiographic documentation of implant alignment is needed to analyse malrotation and malpositioning. We examined whether intraoperative fluoroscopic images can achieve more accurate image quality than postoperative radiographic X-ray images.

PATIENTS AND METHODS

We prospectively analysed 30 consecutive patients after total knee arthroplasty (TKA). We compared intraoperative fluoroscopic images with postoperative radiographic X-ray images. Radiation exposure was documented.

RESULTS

Fluoroscopic anterior-posterior images could achieve accurate image quality in 77% compared to 60% in radiographic images (p=0.016) and 54% compared to 34% on lateral view, respectively (p=0.008). Very good intra-observer correlation for fluoroscopic images could be achieved for femoral α angle with 0.84. Radiation exposure was 0.087+/-0.128 mGy.

CONCLUSION

We observed significantly better image quality in fluoroscopic images than in radiographic X-ray images. The observed radiation exposure is lower than those expected for radiographic X-ray images. We conclude that fluoroscopic images can produce higher image quality and decreased radiation exposure.

Modern cemented total knee arthroplasty design shows a higher incidence of radiolucent lines compared to its predecessor

PURPOSE

To prevent early failure it is necessary to evaluate modern TKA system for possible shortcomings during implantation. The aim of this study was to evaluate the radiographic outcome and short-term survival of a modern cemented primary TKA system compared to its predecessor.

METHODS

The authors reviewed 529 primary cemented TKAs [276 Attune (ATT) and 253 PFC Sigma (PFC)], which were implanted between 2014 and 2017 concerning the radiographic outcome and short-term survival. Radiographs were taken before discharge, 6 weeks, 6 months and 12 months postoperatively. Radiographic analysis was performed by two independent assessors using the Modern Knee Society Radiographic Evaluation System.

RESULTS

The incidence of radiolucent lines was significantly higher in the ATT group compared with the PFC group 12 months postoperatively (35.1%; n = 97 TKAs vs. 7.5%; n = 19 TKAs; p < 0.001). Survival analysis could not show any differences in revision-free survival or revision rate.

CONCLUSION

The modern primary TKA system shows an increased number of radiolucent lines, especially on the tibial component in this short-term analysis and may mostly be due to technique-related issues. Patients with those radiolucent lines even though they show no clinical evidence for loosening should be closely monitored at regular intervals. These findings are of vital clinical importance because surgeons should be aware of particular challenges in preparation and cementing technique once they are using this TKA-system.

LEVEL OF EVIDENCE

Retrospective cohort study, Level III.

A Novel Percentage-Based System for Determining Aseptic Loosening of Total Knee Arthroplasty Tibial Components

BACKGROUND

There are limited data on evaluating the significance of radiolucent lines and aseptic loosening in total knee arthroplasty (TKA). We sought to compare the sensitivity, specificity, and reliability of the Knee Society Total Knee Arthroplasty Roentgenographic Evaluation and Scoring System (KSRES) in detecting tibial component loosening compared to a novel percentage-based system (PBS).

METHODS

We retrospectively reviewed radiographs obtained from 48 patients within 6 months prior to revision TKA. The radiographs were randomized and four reviewers independently used the KSRES to categorize tibial implants as nonconcerning, clinical follow-up for progression, or loose as described by KSRES. For the PBS, the percent involvement of the tibial implant interface of any radiolucency at the bone-cement or cement-implant interface was determined. The higher percentage from either the anteroposterior or the lateral image was the final score. Components were categorized as nonconcerning (≤10%), clinical follow-up for progression (11%-24%), or loose (≥25%). We compared the sensitivity, specificity, and interobserver reliability using intraoperative assessment of implant fixation as the gold standard.

RESULTS

For the KSRES, the mean sensitivity for determining tibial loosening was 7.3% and mean specificity for determining a nonconcerning implant was 95.9%. The PBS significantly increased the sensitivity to 91.1% (P < .001) while maintaining a specificity of 87.9% (P = .2). Interobserver reliability significantly increased from a mean kappa of 0.26 to 0.75 (P < .001).

CONCLUSION

The KSRES significantly underestimates implant loosening. The proposed percentage-based system demonstrated excellent sensitivity, specificity, and interobserver reliability in determining tibial implant loosening in this patient population.

Fluoroscopically Assisted Radiographs Improve Sensitivity of Detecting Loose Tibial Implants in Revision Total Knee Arthroplasty

BACKGROUND

Fluoroscopically assisted radiographs theoretically improve detection of total knee arthroplasty (TKA) implant loosening by providing a better evaluation of the true implant interface, but their utility has not been well studied. We sought to determine whether fluoroscopically guided radiographs improve the sensitivity, specificity, and interobserver reliability of determining TKA implant loosening compared to standard radiographs.

METHODS

Standard anteroposterior and lateral and fluoroscopically assisted radiographs were retrospectively obtained from 60 patients within 6 months before revision TKA. Thirty knees were revised for aseptic loosening and 30 knees for other indications, most commonly instability. The radiographs were randomized. Four reviewers independently determined whether each tibial and femoral component was radiographically loose or stable. Intraoperative determination of implant stability was utilized as the gold standard.

RESULTS

Fluoroscopically guided radiographs had a significantly higher sensitivity for detecting tibial component loosening compared to standard radiographs (85.3% vs 74.8%, P = .02). Sensitivity in detecting femoral component loosening was poor overall and not improved by fluoroscopic enhancement compared to standard radiographs (58.8% vs 66.5%, P = .33). Fluoroscopically guided radiographs did not improve the specificity of detecting well-fixed implants in either tibial or femoral components nor affect the mean interobserver reliability over standard radiographs (kappa = 0.58 vs kappa = 0.60, P = .6).

CONCLUSION

Fluoroscopically assisted radiographs increased the sensitivity of detecting tibial component loosening over standard radiographs, but this clinical significance is unclear. Fluoroscopically guided radiographs may provide benefit in diagnosing aseptic loosening in select patients with painful TKAs.