Is the American Joint Replacement Registry Able to Correctly Classify Revision Total Knee Arthroplasty Procedural Diagnoses?

Extended oral antibiotic prophylaxis and PJI-free survivorship after primary total knee arthroplasty

INTRODUCTION

Recent evidence has emerged supporting the use of extended oral antibiotic (EOA) prophylaxis after primary total knee replacement (TKA) to reduce periprosthetic joint infection (PJI) in high-risk patients. However, much of the evidence stems from single-institution series with limited sample sizes. This study aimed to explore the impact of EOA on complications and infection-free survivorship in a large cohort of patients after primary TKA.

METHODS

A large national database was used to identify patients undergoing primary TKA from 2015 to 2022. Patients receiving 7-14 days of EOA were identified. Propensity-score matching, based on patient comorbidities, was used to match patients who received EOA and to control patients who did not. Three cohorts were created: any-risk, high-risk, and standard-risk. Complications at 90-days were assessed with univariate analysis and survivorship free of PJI to 2 years was analyzed with the Kaplan-Meier method and cox regression.

RESULTS

We identified 5,701 patients who received EOA: 3,628 (64%) with high-risk comorbidities and 2,073 (36%) standard risk. There were no significant reduction in hazard of PJI at 90-days (any-risk: HR: 1.65, 95% CI: 0.90-3.04, P = 0.11; high-risk: HR: 1.37, 95% CI: 0.69-2.70, P = 0.4; standard-risk: HR: 1.51, 95% CI: 0.53-4.26, P = 0.4), 1 year (P > 0.07), or 2 years (any-risk: HR: 1.42, 95% CI: 0.98-2.05, P = 0.065; high-risk: HR: 1.14, 95% CI: 0.76-1.73, P = 0.5; standard-risk: HR: 1.51, 95% CI: 0.76-2.98, P = 0.2) with EOA administration.

DISCUSSION

EOA prophylaxis was not associated with improved PJI-free survivorship at any measured time point following primary TKA in either high-risk or standard-risk risk patients. Given the observed widespread use of EOA, our study highlights the need for further investigation to delineate what specific populations may benefit from EOA prophylaxis.

Medicare Advantage Is Associated With Higher Mortality After Antibiotic Spacer Placement for Periprosthetic Joint Infection

BACKGROUND

Privatized Medicare Advantage (MA) plans are an alternative to traditional Medicare (TM). We sought to identify differences in 90-day postoperative mortality and nonfatal adverse events between TM and MA patients undergoing stage 1 antibiotic spacer placement for periprosthetic joint infection (PJI) of the hip or knee.

METHODS

A nationally representative database was queried from 2015 to 2021 for adult patients undergoing stage 1 antibiotic spacer placement for PJI. Using the International Classification of Disease, 10th Revision, and Current Procedural Terminology codes, as well as hospital charges for antibiotics, patients undergoing stage 1 exchange arthroplasty for PJI were identified. Patients were then grouped into TM and MA cohorts. The primary outcome was the odds of 90-day mortality. Multivariable logistic regressions were conducted to address possible confounding demographic, comorbidity, and hospital characteristics.

RESULTS

Of the 40,346 patients undergoing stage 1 spacer placement for PJI, 16,637 (41.2%) had TM coverage and 9,218 (22.8%) had MA coverage. Mortality within 90 days of surgery was higher in the MA cohort (1.4% versus 1.0%, P = 0.004). Multivariable logistic regression demonstrated significantly higher adjusted odds of mortality (adjusted odds ratio = 1.42, 95% confidence interval = 1.11 to 1.81, P = 0.005) in MA patients compared to TM.

CONCLUSIONS

Even after accounting for available confounders with our multivariable analyses, patients enrolled in an MA plan were more than 40% more likely to die within 90 days of surgery compared to patients who have TM coverage. Further study is necessary to better understand the underlying cause of this finding.

Robotic Assistance Is Not Associated With Decreased Early Revisions in Cementless TKA: An Analysis of the American Joint Replacement Registry

BACKGROUND

Previously, we conducted a retrospective study of American Joint Replacement Registry (AJRR) data that examined the 2-year odds of revision between robotic-assisted and nonrobotic-assisted TKA, and we found no benefit to robotic assistance. However, proponents of robotic assistance have suggested that robot platforms confer more accurate bone cuts and precise implant sizing that might promote osteointegration of cementless implants by limiting micromotion at the bone-implant interface that could lead to aseptic loosening. Therefore, it seems important specifically to evaluate the odds of revision among patients with cementless implants only within our previous study population.

QUESTIONS/PURPOSES

(1) After controlling for potentially confounding variables, such as surgeon, institution, and patient comorbidity profile, was robotic assistance associated with a decreased odds of 2-year revision of cementless TKA for any reason compared with cementless TKAs performed without robotic assistance? (2) After again controlling for potentially confounding variables, was robotic assistance associated with a decreased odds of 2-year revision of cementless TKA for particular revision indications (such as aseptic loosening, infection, instability, or pain) compared with the cementless TKAs performed without robotic assistance?

METHODS

Using the AJRR, a retrospective cohort of patients ≥ 65 years of age with osteoarthritis who underwent primary TKA with cementless femur and tibial components from January 2017 through March 2020 was identified. Procedures performed with hybrid fixation (cement only on the tibia but not on the femur, or vice versa) were excluded. The AJRR was selected because it is the largest arthroplasty registry in the world by annual procedure volume, and it contains a data linkage with inpatient and outpatient Medicare claims data to ensure near-complete 2-year follow-up. A total of 9220 patients were identified, and robotic assistance was used in 45% (4130) of procedures. Patient age did not differ between groups (72 ± 5 years versus 72 ± 5 years; p = 0.29). However, the robotic-assisted cohort had a slightly higher proportion of female patients (56% [2332 of 4130] versus 53% [2693 of 5090]; p = 0.002) and higher Charlson comorbidity index (CCI) (2.9 ± 0.9 versus 2.8 ± 0.9; p = 0.003). Therefore, a mixed-effects model was used to analyze the ORs for all-cause linked revision with robotic assistance and was adjusted for age, gender, CCI, surgeon, and institution. Subanalyses were performed on indications for revision. A power analysis demonstrated the ability to measure a difference as small as one-half SD between risk of revision within each cohort (specifically, moderate effect sizes based on Cohen d).

RESULTS

After controlling for potentially confounding variables, such as surgeon, location of surgery, and patient comorbidity profile, we found no difference regarding odds of all-cause revision between robotic-assisted and nonrobotic-assisted cementless TKA (OR of robotic-assisted versus nonrobotic-assisted cementless TKA 0.8 [95% CI 0.5 to 1.3]; p = 0.41). There were no differences in reasons for revision between robotic-assisted and nonrobotic-assisted cementless TKA, such as mechanical loosening (OR 3.2 [95% CI 0.8 to 12]; p = 0.09) and infection (OR 1.5 [95% CI 0.8 to 2.6]; p = 0.19).

CONCLUSION

We found no evidence that robotic assistance improves the odds of cementless implant survival free from revision at 2 years. Importantly, the differences in odds of revision beyond 2 years as a function of robotic assistance in cementless TKA remains unknown and warrants further population-level investigation, but until or unless robotic assistance proves its value in well-designed studies in terms of endpoints that patients can perceive (such as pain, function, or survivorship), we recommend against widespread adoption until further evidence becomes available. Additionally, we encourage surgeons and healthcare facilities using robotic assistance in cementless TKAs to study its impact on patient outcomes, if any.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Does the Addition of a Tibial Stem Extender in Total Knee Arthroplasty Decrease Risk of Aseptic Loosening in Patients with Obesity? An Analysis from the American Joint Replacement Registry

Mechanical loosening is a leading cause of failure of total knee arthroplasties (TKAs) for which obesity may be a risk factor. With rising rates of obesity and increasing incidence of TKA, the identification of factors to mitigate this cause of failure is necessary. The purpose of this study is to determine if the use of a tibial stem extender (TSE) decreases the risk of mechanical loosening in patients with obesity undergoing TKA. The American Joint Replacement Registry and linked Centers for Medicare & Medicaid Services claims database were utilized to identify a patient cohort with a body mass index (BMI) of 30 kg/m2 or greater and age 65 years or older who underwent primary elective TKA between 2012 and 2021. Patients were divided into cohorts based on obesity class and TSE utilization. The estimated association of TSE use, BMI categories, and covariates with the risk of revisions for mechanical loosening in both unadjusted and adjusted settings was determined. Hazard ratios and their 95% confidence intervals for the risk of mechanical loosening were calculated. A total of 258,775 TKA cases were identified. A total of 538 of 257,194 (0.21%) patients who did not receive a TSE and one patient out of 1,581 (0.06%) with a TSE were revised for mechanical loosening. In adjusted analysis, TSE use was not protective against mechanical loosening and BMI > 40 was not a significant risk factor. Use of a TSE was not found to be protective against mechanical loosening in patients with obesity; however, analysis was limited by the small number of outcome events in the cohort. Further analysis with a larger cohort of patients with TSE and a longer follow-up time is necessary to corroborate this finding.

Is Wear Still a Concern in Total Knee Arthroplasty With Contemporary Conventional and Highly Crosslinked Polyethylene Tibial Inserts in the mid- to Long-Term?

Background

Modern literature has brought into question if wear of tibial inserts made from conventional or highly crosslinked polyethylene (HXL PE) is still a factor limiting longevity of total knee arthroplasty (TKA) in the mid- to long-term. It is the objective of this study to determine: 1) most common causes of mid- to long-term TKA failure, 2) the prevalence of delamination, and 3) the medial/lateral linear wear rates of conventional and HXL PE tibial inserts retrieved in the mid- to long-term.

Methods

A tibial insert retrieval cohort of 107 inserts (79 conventional, 28 HXL PE) with a minimum time in situ of 6.5 years (mean 11.7 ± 4) was studied. Failure causes were determined from chart-review, delamination presence was assessed microscopically, and medial/lateral linear wear was determined by minimal thickness changes measured with a dial-indicator.

Results

The most common mid-to long-term etiologies for failure were instability (44.9%), PE wear 15%), aseptic loosening (14%), and infection (13.1%). Delamination occurred in 70% of inserts (72.1% conventional, 64.3% HXLPE). Gross material loss due to delamination appeared to be the underlying reason for at least 33.3% of cases exhibiting instability. Of the cases removed for infection, 75% exhibited no histopathological hallmarks of acute infection. The medial/lateral wear rates were 0.054/0.051 (conventional) and 0.014/0.011 (HXL) mm/y, respectively.

Conclusions

Polyethylene wear still appears to be a major primary and secondary cause for TKA revision in the mid- to long-term. Wear may manifest as destabilizing delamination or as continuous release of fine wear particles potentially resulting in inflammatory responses and subsequent failure.

Mode of Fixation and Survivorship in Primary Total Knee Arthroplasty in the American Joint Replacement Registry

BACKGROUND

A recent rapid increase in cementless total knee arthroplasty (TKA) has been noted in the American Joint Replacement Registry (AJRR). The purpose of our study was to compare TKA survivorship based on the mode of fixation reported to the AJRR in the Medicare population.

METHODS

Primary TKAs from Medicare patients submitted to AJRR from 2012 to 2022 were analyzed. The Medicare and AJRR databases were merged. Cox regression stratified by sex compared revision outcomes (all-cause, infection, mechanical loosening, and fracture) for cemented, cementless, and hybrid fixation, controlling for age and the Charlson comorbidity index (CCI).

RESULTS

A total of 634,470 primary TKAs were analyzed. Cementless TKAs were younger (71.8 versus 73.1 years, P < .001) than cemented TKAs and more frequently utilized in men (8.2 versus 5.8% women, P < .001). Regional differences were noted, with cementless fixation more common in the Northeast (10.5%) and South (9.2%) compared to the West (4.4%) and Midwest (4.3%) (P < .001). No significant differences were identified in all-cause revision rates in men or women ≥ 65 for cemented, cementless, or hybrid TKA after adjusting for age and CCI. Significantly lower revision for fracture was identified for cemented compared to cementless and hybrid fixation in women ≥ 65 after adjusting for age and CCI (P = .0169).

CONCLUSIONS

No survivorship advantage for all-cause revision was noted based on the mode of fixation in men or women ≥ 65 after adjusting for age and CCI. A significantly lower revision rate for fractures was noted in women ≥ 65 utilizing cemented fixation. Cementless fixation in primary TKA should be used with caution in elderly women.

Robotic-assisted TKA is Not Associated With Decreased Odds of Early Revision: An Analysis of the American Joint Replacement Registry

BACKGROUND

Robotic-assisted TKA continues to see wider clinical use, despite limited knowledge of its impact on patient satisfaction and implant survival. Most studies to date have presented small cohorts and came from single-surgeon or single-center experiences. Therefore, a population-level comparison of revision rates between robotic-assisted and conventional TKA in the registry setting may help arthroplasty surgeons better define whether robotic assistance provides a meaningful advantage compared with the conventional technique.

QUESTIONS/PURPOSES

(1) After controlling for confounding variables, such as surgeon, location of surgery, and patient comorbidity profile, were robotic-assisted TKAs less likely than conventional TKAs to result in revision for any reason at 2 years? (2) After again controlling for confounding variables, were robotic-assisted TKAs less likely to result in any specific reasons for revision than the conventional technique at 2 years?

METHODS

The American Joint Replacement Registry was used to identify patients 65 years or older who underwent TKA between January 2017 and March 2020 with a minimum of 2 years of follow-up. Patients were limited to age 65 yeas or older to link TKAs to Medicare claims data. Two retrospective cohorts were created: robotic-assisted TKA and conventional TKA. Patient demographic variables included in the analysis were age, gender, BMI, and race. Additional characteristics included the Charlson comorbidity index, anesthesia type, year of the index procedure, and length of stay. A total of 10% (14,216 of 142,550) of TKAs performed during this study period used robotics. Patients with robotic-assisted TKA and those with conventional TKA were similar regarding age (73 ± 6 years versus 73 ± 6 years; p = 0.31) and gender (62% [8736 of 14,126] versus 62% [79,399 of 128,334] women; p = 0.34). A multivariable, mixed-effects logistic regression model was created to analyze the odds of all-cause revision as a factor of robot use, and a logistic regression model was created to investigate specific revision diagnoses.

RESULTS

After controlling for potentially confounding variables, such as surgeon, location of surgery, and Charlson comorbidity index, we found no difference between the robotic-assisted and conventional TKAs in terms of the odds of revision at 2 years (OR of robotic-assisted versus conventional TKA 1.0 [95% CI 0.8 to 1.3]; p = 0.92). The reasons for revision of robotic-assisted TKA did not differ from those of conventional TKA, except for an increased odds of instability (OR 1.6 [95% CI 1.0 to 2.4]; p = 0.04) and pain (OR 2.1 [95% CI 1.4 to 3.0]; p < 0.001) in the robotic-assisted cohort.

CONCLUSION

In light of these findings, surgeons should not assume that robotic assistance in TKA will lead to improved early implant survival. Our findings do not support an improvement over conventional TKA with robotic assistance with regards to common causes of early revisions such malalignment, malposition, stiffness, pain, and instability, and in some cases, suggest there is a benefit to conventional TKA. Differences in the mid-term and long-term revision risk with conventional versus robotic-assisted TKA remain unknown. Appropriate informed consent around the use of robotic assistance should not imply decreased early revision risk.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Precision or Pitfall? Evaluating the Accuracy of ICD-10 Coding for Cemented Total Hip Arthroplasty: A Multicenter Study

BACKGROUND

The International Statistical Classification of Diseases and Related Health Problems, 10th Revision, Procedure Coding System (ICD-10-PCS) was adopted in the U.S. in 2015. Proponents of the ICD-10-PCS have stated that its granularity allows for a more accurate representation of the types of procedures performed by including laterality, joint designation, and more detailed procedural data. However, other researchers have expressed concern that the increased number of codes adds further complexity that leads to inaccurate and inconsistent coding, rendering registry and research data based on ICD-10-PCS codes invalid and inaccurate. We aimed to determine the accuracy of the ICD-10-PCS for identifying cemented fixation in primary total hip arthroplasty (THA).

METHODS

We retrospectively reviewed all cemented primary THAs performed at 4 geographically diverse, academic medical centers between October 2015 and October 2020. Cemented fixation was identified from the ICD-10-PCS coding for each procedure. The accuracy of an ICD-10-PCS code relative to the surgical record was determined by postoperative radiograph and chart review, and cross-referencing with institution-level coding published by the American Joint Replacement Registry (AJRR) was also performed.

RESULTS

A total of 552 cemented THA cases were identified within the study period, of which 452 (81.9%) were correctly coded as cemented with the ICD-10-PCS. The proportion of cases that were correctly coded was 187 of 260 (72%) at Institution A, 158 of 185 (85%) at Institution B, 35 of 35 (100%) at Institution C, and 72 of 72 (100%) at Institution D. Of the 480 identified cemented THA cases at 3 of the 4 institutions, 403 (84%) were correctly reported as cemented to the AJRR (Institution A, 185 of 260 cases [71%]; Institution B, 185 of 185 [100%]; and Institution C, 33 of 35 [94%]). Lastly, of these 480 identified cemented THA cases, 317 (66%) were both correctly coded with the ICD-10-PCS and correctly reported as cemented to the AJRR.

CONCLUSIONS

Our findings revealed existing discrepancies within multiple institutional data sets, which may lead to inaccurate reporting by the AJRR and other registries that rely on ICD-10-PCS coding. Caution should be exercised when utilizing ICD-10 procedural data to evaluate specific details from administrative claims databases as these inaccuracies present inherent challenges to data validity and interpretation.