Does Preoperative Pharmacogenomic Testing of Patients Undergoing TKA Improve Postoperative Pain? A Randomized Trial.

BACKGROUND: Pharmacogenomics is an emerging and affordable tool that may improve postoperative pain control. One challenge to successful pain control is the large interindividual variability among analgesics in their efficacy and adverse drug events. Whether preoperative pharmacogenomic testing is worthwhile for patients undergoing TKA is unclear. QUESTIONS/PURPOSES: (1) Are the results of preoperative pharmacogenetic testing associated with lower postoperative pain scores as measured by the Overall Benefit of Analgesic Score (OBAS)? (2) Do the results of preoperative pharmacogenomic testing lead to less total opioids given? (3) Do the results of preoperative pharmacogenomic testing lead to changes in opioid prescribing patterns? METHODS: Participants of this randomized trial were enrolled from September 2018 through December 2021 if they were aged 18 to 80 years and were undergoing primary TKA under general anesthesia. Patients were excluded if they had chronic kidney disease, a history of chronic pain or narcotic use before surgery, or if they were undergoing robotic surgery. Preoperatively, patients completed pharmacogenomic testing (RightMed, OneOME) and a questionnaire and were randomly assigned to the experimental group or control group. Of 99 patients screened, 23 were excluded, one before randomization; 11 allocated patients in each group did not receive their allocated interventions for reasons such as surgery canceled, patients ultimately undergoing spinal anesthesia, and change in surgery plan. Another four patients in each group were excluded from the analysis because they were missing an OBAS report. This left 30 patients for analysis in the control group and 38 patients in the experimental group. The control and experimental groups were similar in age, gender, and race. Pharmacogenomic test results for patients in the experimental group were reviewed before surgery by a pharmacist, who recommended perioperative medications to the clinical team. A pharmacist also assessed for clinically relevant drug-gene interactions and recommended drug and dose selection according to guidelines from the Clinical Pharmacogenomics Implementation Consortium for each patient enrolled in the study. Patients were unaware of their pharmacogenomic results. Pharmacogenomic test results for patients in the control group were not reviewed before surgery; instead, standard perioperative medications were administered in adherence to our institutional care pathways. The OBAS (maximum 28 points) was the primary outcome measure, recorded 24 hours postoperatively. A two-sample t-test was used to compare the mean OBAS between groups. Secondary measures were the mean 24-hour pain score, total morphine milligram equivalent, and frequency of opioid use. Postoperatively, patients were assessed for pain with a VAS (range 0 to 10). Opioid use was recorded preoperatively, intraoperatively, in the postanesthesia care unit, and 24 hours after discharge from the postanesthesia care unit. Changes in perioperative opioid use based on pharmacogenomic testing were recorded, as were changes in prescription patterns for postoperative pain control. Preoperative characteristics were also compared between patients with and without various phenotypes ascertained from pharmacogenomic test results. RESULTS: The mean OBAS did not differ between groups (mean ± SD 4.7 ± 3.7 in the control group versus 4.2 ± 2.8 in the experimental group, mean difference 0.5 [95% CI -1.1 to 2.1]; p = 0.55). Total opioids given did not differ between groups or at any single perioperative timepoint (preoperative, intraoperative, or postoperative). We found no difference in opioid prescribing pattern. After adjusting for multiple comparisons, no difference was observed between the treatment and control groups in tramadol use (41% versus 71%, proportion difference 0.29 [95% CI 0.05 to 0.53]; nominal p = 0.02; adjusted p > 0.99). CONCLUSION: Routine use of pharmacogenomic testing for patients undergoing TKA did not lead to better pain control or decreased opioid consumption. Future studies might focus on at-risk populations, such as patients with chronic pain or those undergoing complex, painful surgical procedures, to test whether pharmacogenomic results might be beneficial in certain circumstances. LEVEL OF EVIDENCE: Level I, therapeutic study.

Low Risk of Periprosthetic Joint Infection After Aseptic Revision Total Knee Arthroplasty With Intraosseous Vancomycin.

BACKGROUND: Aseptic revisions are the most common reason for revision total knee arthroplasty (rTKA). Previous literature reports early periprosthetic joint infection (PJI) rates after aseptic rTKA to range from 3 to 9.4%. Intraosseous (IO) regional administration of vancomycin has previously been shown to produce high local tissue concentrations in primary and rTKA. However, no data exist on the effect of prophylactic IO vancomycin on early PJI rates in the setting of aseptic rTKA. The aim of this study was to determine the following: (1) what is the rate of early PJI during the first year after surgery in aseptic rTKA performed with IO vancomycin; and (2) how does this compare to previously published PJI rates after rTKA. METHODS: A consecutive series of 117 cases were included in this study who underwent rTKA between January 2016 and March 2022 by 1 of 2 fellowship-trained adult reconstruction surgeons and received IO vancomycin at the time of surgery in addition to standard intravenous antibiotic prophylaxis. Rates of PJI at 3 months, 1 year, and the final follow-up were evaluated and compared to prior literature. RESULTS: Follow-up at 3 months was available for 116 of the 117 rTKAs, with 1 lost to follow-up. The rate of PJI was 0% at 3 months postoperatively. Follow-up at 1 year was obtained for 113 of the 117 rTKAs, and the PJI rate remained 0%. The rate of PJI at the final follow-up of ≥ 1 year was 0.88% (95% confidence interval: -0.84 to 2.61). Previous literature reports PJI rates in aseptic rTKA to range from 3 to 9.4%. CONCLUSIONS: Dual prophylactic antibiotics with IO vancomycin in conjunction with intravenous cephalosporins or clindamycin were associated with a substantial reduction in early PJI compared to prior published literature. These data supplement the early evidence about the potential clinical benefits of IO vancomycin for infection prevention in high-risk cases. LEVEL OF EVIDENCE: Level III, therapeutic study.

Rheumatoid Arthritis Is Not a Contraindication to Unicompartmental Knee Arthroplasty.

BACKGROUND: Rheumatoid arthritis (RA) has historically been considered a contraindication for unicompartmental knee arthroplasty (UKA). However, the widespread use of disease-modifying antirheumatic drugs has substantially improved the management of RA and prevented disease progression. The objective of this study was to ascertain whether RA impacts UKA revision-free survivorship. METHODS: Patients undergoing UKA from 2010 to 2021 were identified in an administrative claims database (n = 105,937) using Current Procedural Terminology code 27446. All patients who underwent UKA who had a diagnosis of RA with a minimum of 2-year follow-up (n = 1,422) were propensity score matched based on age, sex, and Elixhauser Comorbidity Index to those who did not have RA (n = 1,422). Laterality was identified using the 10th Revision of International Classification of Diseases codes. The primary outcome was ipsilateral revision to total knee arthroplasty (TKA) within 2 years, and the secondary outcome was ipsilateral revision at any time. RESULTS: Among the 1,422 patients who had a UKA and a diagnosis of RA, 37 patients (2.6%) underwent conversion to TKA within 2 years, and 48 patients (3.4%) underwent conversion to TKA at any point. In comparison, 28 patients (2.0%) in the propensity-matched control group underwent conversion to TKA within 2 years, and 40 patients (2.8%) underwent conversion to TKA at any point. Statistical analysis revealed no significant difference in conversion to TKA between patients who had and did not have RA, either within 2 years (P = .31) or anytime (P = .45). CONCLUSIONS: Patients who had RA and underwent UKA did not have an increased risk of revision to TKA compared to those who did not have RA. This may indicate that modern management of RA could allow for expanded UKA indications for RA patients.

Clostridium difficile Infection Prior to Total Hip Arthroplasty Independently Increases the Risk of Periprosthetic Joint Infection.

BACKGROUND: Periprosthetic joint infection (PJI) following total hip arthroplasty (THA) is associated with major morbidity. There may be a link between the gut microbiome and an individual's overall immune system. A Clostridium difficile (C. difficile) infection portends poor gut microbiome health and has been previously associated with increased 90-day complication rates in total joint arthroplasty (TJA). The purpose of this study was to determine the effect of a previous history of C. difficile infection within 2 years of undergoing THA on PJI within 2 years postoperatively. METHODS: Patients undergoing THA from 2010 to 2021 were identified in a patient claims database (n = 770,075). Patients who had active records 2 years before and after THA as well as a history of C. difficile infection within 2 years prior to THA (n = 1,836) were included and propensity matched to a control group using age, sex, and Elixhauser comorbidity index. The primary outcome was the 2-year incidence of postoperative PJI. The exposed C. difficile infection cohort was stratified into 4 groups based on the time proximity of the C. difficile infection. Chi-square tests and logistic regressions were used to compare the groups. RESULTS: A C. difficile infection anytime within 2 years prior to total hip arthroplasty was independently associated with higher odds of PJI (OR [odds ratio]: 1.49 [95% CI (confidence interval) 1.09 to 2.02, P = .014]). Proximity of C. difficile infection to arthroplasty was associated with increased risk of PJI (infection 0 to 3 months before THA: OR 2.01 [95% CI 1.23 to 3.20], infection 3 to 6 months before THA: OR 1.84 [95% CI 1.06 to 3.04], infection 6 to 12 months before THA: OR 1.10 [95% CI 0.65 to 1.77], infection 1 to 2 years before THA: OR 1.40 [95% CI 0.94 to 2.06]). CONCLUSIONS: A C. difficile infection prior to THA is an independent risk factor for PJI. Proximity of C. difficile infection is associated with increased risk of PJI. Future investigations should evaluate how to adequately optimize patients prior to THA and pursue strategies to determine appropriate timing for proceeding with THA.

Discordance Abounds in Minimum Clinically Important Differences in THA: A Systematic Review.

BACKGROUND: The minimum clinically important difference (MCID) is intended to detect a change in a patient-reported outcome measure (PROM) large enough for a patient to appreciate. Their growing use in orthopaedic research stems from the necessity to identify a metric, other than the p value, to better assess the effect size of an outcome. Yet, given that MCIDs are population-specific and that there are multiple calculation methods, there is concern about inconsistencies. Given the increasing use of MCIDs in total hip arthroplasty (THA) research, a systematic review of calculated MCID values and their respective ranges, as well as an assessment of their applications, is important to guide and encourage their use as a critical measure of effect size in THA outcomes research. QUESTIONS/PURPOSES: We systematically reviewed MCID calculations and reporting in current THA research to answer the following: (1) What are the most-reported PROM MCIDs in THA, and what is their range of values? (2) What proportion of studies report anchor-based versus distribution-based MCID values? (3) What are the most common methods by which anchor-based MCID values are derived? (4) What are the most common derivation methods for distribution-based MCID values? (5) How do the reported medians and corresponding ranges compare between calculation methods for each PROM? METHODS: The EMBASE, MEDLINE, and PubMed databases were systematically reviewed from inception through March 2022 for THA studies reporting an MCID value for any PROMs. Two independent authors reviewed articles for inclusion. All articles calculating new PROM MCID scores after primary THA were included for data extraction and analysis. MCID values for each PROM, MCID calculation method, number of patients, and study demographics were extracted from each article. In total, 30 articles were included. There were 45 unique PROMs for which 242 MCIDs were reported. These studies had a total of 1,000,874 patients with a median age of 64 years and median BMI of 28.7 kg/m 2 . Women made up 55% of patients in the total study population, and the median follow-up period was 12 months (range 0 to 77 months). The overall risk of bias was assessed as moderate using the modified Methodological Index for Nonrandomized Studies criteria for comparative studies (the mean score for comparative papers in this review was 18 of 24, with higher scores representing better study quality) and noncomparative studies (for these, the mean score was 10 of a possible 16 points, with higher scores representing higher study quality). Calculated values were classified as anchor-based, distribution-based, or not reported. MCID values for each PROM, MCID calculation method, number of patients, and study demographics were extracted from each study. Anchor-based and distribution-based MCIDs were compared for each unique PROM using a Wilcoxon rank sum test, given the non-normal distribution of values. RESULTS: The Oxford Hip Score (OHS) and the Hip Injury and Osteoarthritis Score (HOOS) Pain and Quality of Life subscore MCIDs were the most frequently reported, comprising 12% (29 of 242), 8% (20 of 242), and 8% (20 of 242), respectively. The EuroQol VAS (EQ-VAS) was the next-most frequently reported (7% [17 of 242]) followed by the EuroQol 5D (EQ-5D) (7% [16 of 242]). The median anchor-based value for the OHS was 9 (IQR 8 to 11), while the median distribution-based value was 6 (IQR 5 to 6). The median anchor-based MCID values for HOOS Pain and Quality of Life were 33 (IQR 28 to 35) and 25 (14 to 27), respectively; the median distribution-based values were 10 (IQR 9 to 10) and 13 (IQR 10 to 14), respectively. Thirty percent (nine of 30) of studies used an anchor-based method to calculate a new MCID, while 40% (12 of 30) used a distribution-based technique. Thirty percent of studies (nine of 30) calculated MCID values using both methods. For studies reporting an anchor-based calculation method, a question assessing pain relief, satisfaction, or quality of life on a five-point Likert scale was the most commonly used anchor (30% [eight of 27]), followed by a receiver operating characteristic curve estimation (22% [six of 27]). For studies using distribution-based calculations, the most common method was one-half the standard deviation of the difference between preoperative and postoperative PROM scores (46% [12 of 26]). Most reported median MCID values (nine of 14) did not differ by calculation method for each unique PROM (p > 0.05). The OHS, HOOS JR, and HOOS Function, Symptoms, and Activities of Daily Living subscores all varied by calculation method, because each anchor-based value was larger than its respective distribution-based value. CONCLUSION: We found that MCIDs do not vary very much by calculation method across most outcome measurement tools. Additionally, there are consistencies in MCID calculation methods, because most authors used an anchor question with a Likert scale for the anchor-based approach or used one-half the standard deviation of preoperative and postoperative PROM score differences for the distribution-based approach. For some of the most frequently reported MCIDs, however, anchor-based values tend to be larger than distribution-based values for their respective PROMs. CLINICAL RELEVANCE: We recommend using a 9-point increase as the MCID for the OHS, consistent with the median reported anchor-based value derived from several high-quality studies with large patient groups that used anchor-based approaches for MCID calculations, which we believe are most appropriate for most applications in clinical research. Likewise, we recommend using the anchor-based 33-point and 25-point MCIDs for the HOOS Pain and Quality of Life subscores, respectively. We encourage using anchor-based MCID values of WOMAC Pain, Function, and Stiffness subscores, which were 29, 26, and 30, respectively.

There are Considerable Inconsistencies Among Minimum Clinically Important Differences in TKA: A Systematic Review.

BACKGROUND: Patient-reported outcome measures (PROMs) are frequently used to assess the impact of total knee arthroplasty (TKA) on patients. However, mere statistical comparison of PROMs is not sufficient to assess the value of TKA to the patient, especially given the risk profile of arthroplasty. Evaluation of treatment effect sizes is important to support the use of an intervention; this is often quantified with the minimum clinically important difference (MCID). MCIDs are unique to specific PROMs, as they vary by calculation methodology and study population. Therefore, a systematic review of calculated MCID values, their respective ranges, and assessment of their applications is important to guide and encourage their use as a critical measure of effect size in TKA outcomes research. QUESTIONS/PURPOSES: In this systematic review of MCID calculations and reporting in primary TKA, we asked: (1) What are the most frequently reported PROM MCIDs and their reported ranges in TKA? (2) What proportion of studies report distribution- versus anchor-based MCID values? (3) What are the most common methods by which these MCID values are derived for anchor-based values? (4) What are the most common derivation methods for distribution-based values? (5) How do the reported medians and corresponding interquartile ranges (IQR) compare between calculation methods for each PROM? METHODS: Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, a systematic review was conducted using the PubMed, EMBASE, and MEDLINE databases from inception through March 2022 for TKA articles reporting an MCID value for any PROMs. Two independent reviewers screened articles for eligibility, including any article that calculated new MCID values for PROMs after primary TKA, and extracted these data for analysis. Overall, 576 articles were identified, 38 of which were included in the final analysis. These studies had a total of 710,128 patients with a median age of 67.7 years and median BMI of 30.9 kg/m 2 . Women made up more than 50% of patients in most studies, and the median follow-up period was 17 months (range 0.25 to 72 months). The overall risk of bias was assessed as moderate using the Jadad criteria for one randomized controlled trial (3 of 5 ideal global score) and the modified Methodological Index for Non-randomized Studies criteria for comparative studies (mean 17.2 ± 1.8) and noncomparative studies (mean 9.6 ± 1.3). There were 49 unique PROMs for which 233 MCIDs were reported. Calculated values were classified as anchor-based, distribution-based, or not reported. MCID values for each PROM, MCID calculation method, number of patients, and study demographics were extracted from each study. Anchor-based and distribution-based MCIDs were compared for each unique PROM using a Wilcoxon rank sum test given non-normal distribution of values. RESULTS: The WOMAC Function and Pain subscores were the most frequently reported MCID value, comprising 9% (22 of 233) and 9% (22 of 233), respectively. The composite Oxford Knee Score (OKS) was the next most frequently reported (9% [21 of 233]), followed by the WOMAC composite score (6% [13 of 233]). The median anchor-based values for WOMAC Function and Pain subscores were 23 (IQR 16 to 33) and 25 (IQR 14 to 31), while the median distribution-based values were 11 (IQR 10.8 to 11) and 22 (IQR 17 to 23), respectively. The median anchor-based MCID value for the OKS was 6 (IQR 4 to 7), while the distribution-based value was 7 (IQR 5 to 10). Thirty-nine percent (15 of 38) used an anchor-based method to calculate a new MCID, while 32% (12 of 38) used a distribution-based technique. Twenty-nine percent of studies (11 of 38) calculated MCID values using both methods. For studies reporting an anchor-based calculation method, a question assessing patient satisfaction, pain relief, or quality of life along a five-point Likert scale was the most commonly used anchor (40% [16 of 40]), followed by a receiver operating characteristic curve estimation (25% [10 of 40]). For studies using distribution-based calculations, all articles used a measure of study population variance in their derivation of the MCID, with the most common method reported as one-half the standard deviation of the difference between preoperative and postoperative PROM scores (45% [14 of 31]). Most reported median MCID values (15 of 19) did not differ by calculation method for each unique PROM (p > 0.05) apart from the WOMAC Function component score and the Knee Injury and Osteoarthritis Outcome Score Pain and Activities of Daily Living subscores. CONCLUSION: Despite variability of MCIDs for each PROM, there is consistency in the methodology by which MCID values have been derived in published studies. Additionally, there is a consensus about MCID values regardless of calculation method across most of the PROMs we evaluated. CLINICAL RELEVANCE: Given their importance to treatment selection and patient safety, authors and journals should report MCID values with greater consistency. We recommend using a 7-point increase as the MCID for the OKS, consistent with the median reported anchor-based value derived from several high-quality studies with large patient groups that used anchor-based approaches for MCID calculation, which we believe are most appropriate for most applications in clinical research. Likewise, we recommend using a 10-point to 15-point increase for the MCID of composite WOMAC, as the median value was 12 (IQR 10 to 17) with no difference between calculation methods. We recommend use of median reported values for WOMAC function and pain subscores: 21 (IQR 15 to 33) and 23 (IQR 13 to 29), respectively.

A Randomized Controlled Trial of Kinematically and Mechanically Aligned Total Knee Arthroplasties: Long-Term Follow-Up.

BACKGROUND: The optimal alignment technique for total knee arthroplasty (TKA) remains controversial. We previously reported 6-month and 2-year results of a randomized controlled trial comparing kinematically versus mechanically aligned TKA. In the present study, we report the mean 13-year (range, 12.6-14.4) follow-up results from this trial. METHODS: The original cohort included 88 TKAs (44 kinematically aligned using patient-specific guides and 44 mechanically aligned using conventional instrumentation), performed from 2008 to 2009. After institutional review board approval, the health records of the original 88 patients were queried. Revisions, reoperations, and complications were recorded. There were 26 patients who died, leaving 62 patients for follow-up. Of these, 48 patients (77%) were successfully contacted via phone. Reoperations and complications were documented. Furthermore, a battery of patient-reported outcome measures (PROMs) (including Western Ontario and McMaster University Index, Oxford Knee Score, Knee Injury and Osteoarthritis Outcome Score Junior, Forgotten Joint Score, Modified-Single Assessment Numerical Evaluation, and patient satisfaction) were obtained. RESULTS: Of the original 88 patients in the study, 15 patients had at least one reoperation (17%) and 5 patients had undergone complete revision surgery (6%). There was no difference between the 2 alignment methods for major and minor reoperations (P = .66). The kinematically aligned total knees self-reported a nonstatistically significant (P = .16) improved satisfaction (96% versus 82%), but no difference in other PROMs compared to mechanically aligned TKAs. CONCLUSION: Kinematically aligned TKA demonstrates excellent mean 13-year results, comparable to mechanically aligned TKA with similar reoperations, complications, and PROMs.

Risk Factors in Patients Who Had Prior Renal or Liver Transplant Undergoing Primary Total Knee Arthroplasty.

BACKGROUND: More solid organ transplant (SOT) patients are undergoing total knee arthroplasty (TKA). This study identifies risk factors for complications, implant survivorship, and mortality in TKA patients who had prior SOT. METHODS: We identified 176 TKAs in patients who had prior SOT. Of these, 77 had a prior renal (RT), 77 had a prior liver (LT) transplant, and 22 had multiple prior transplants (MT). Median survival was estimated using Kaplan-Meier. Univariate analyses were assessed with mixed-effects logistic regressions for complications and Cox-regressions for mortality. Median follow-up was 63 months (range, 24 to 109). RESULTS: At least one acute medical complication occurred in 25, 13, and 27% of cases with prior RT, LT, and MT, respectively (P = .12). None of the variables were significantly associated with acute medical complications. At least one surgical complication occurred in 14, 13 and 14% of cases with prior RT, LT, and MT, respectively (P = 1). Vitamin D supplementation (Odds Ratio [OR] = 0.38, P < .03) was associated with lower risk of surgical complications. Reoperation and revision rates were 5 and 3%, respectively. Older age at time of transplantation and greater level of serum creatinine at time of TKA were associated with lower risk (OR = 0.96, P = .01), and higher risk of reoperation (OR = 4.9, P = .01), respectively. Coronary artery disease was associated with higher mortality (Hazard Ratio = 2.35, P = .01). CONCLUSIONS: Vitamin D was associated with lower surgical complications, whereas a younger age at time of transplantation increased the risk of reoperation. Additionally, SOT patients with coronary artery disease demonstrated higher mortality after TKA.

Higher Tissue Concentrations of Vancomycin Achieved With Low-Dose Intraosseous Injection Versus Intravenous Despite Limited Tourniquet Duration in Primary Total Knee Arthroplasty: A Randomized Trial.

BACKGROUND: Vancomycin use has been suggested in high risk patients undergoing total knee arthroplasty (TKA). Previous literature has shown that a lower dose (500 mg) of vancomycin given by intraosseous regional administration (IORA) achieves tissue concentrations 4-10 times higher than intravenous (IV) administration. There is increasing interest in performing TKA with limited tourniquet inflation time. The purpose of this study is to evaluate whether IORA of vancomycin can achieve effective tissue concentrations with limited tourniquet inflation time. METHODS: Based on prior power calculations, 24 patients undergoing primary TKA were randomized into 2 groups. Group IV-Systemic received weight-based (15 mg/kg) vancomycin with the tourniquet inflated for cementation only. Group IORA received 500 mg vancomycin via IORA after tourniquet inflation which remained inflated for 10 minutes, then reinflated for cementation only. Vancomycin concentrations from tissue, serum, and drain fluid were compared between the 2 groups. RESULTS: Median vancomycin concentrations in tissue were significantly higher (5-15 times) at all time points in the IORA group. Concentrations in fat at the time of wound closure, after the tourniquet had been deflated for most of the procedure, were 5.2 µg/g in Group IV-Systemic and 33.1 µg/g in Group IORA (P < .001). Median bone concentrations taken just prior to cementation were 7.9 µg/g in Group IV-Systemic and 21.8 µg/g in Group IORA (P = .006). There were no complications related to IORA. CONCLUSION: For surgeons who wish to limit tourniquet time and when indicated to use vancomycin, low-dose vancomycin IORA achieves tissue concentrations 5-15 times higher than those achieved by IV administration. LEVEL OF EVIDENCE: Level 1 therapeutic randomized trial.

Robotic-Assisted Total Knee Arthroplasty Allows for Trainee Involvement and Teaching Without Lengthening Operative Time.

BACKGROUND: Robot-assisted total knee arthroplasty (RA-TKA) is more accurate than mechanical total knee arthroplasty (M-TKA) and can provide real-time feedback about alignment and soft-tissue balancing that may be helpful in trainee education. However, both robotic-assist and trainee involvement potentially increase the surgical time. This study sought to evaluate whether RA-TKA procedures were longer than M-TKA procedures and whether trainee participation added additional surgical time. METHODS: This retrospective cohort study reviewed 220 consecutive primary TKAs (110 M-TKA and 110 RA-TKA) performed by an orthopedic trainee under supervision or performed by the consultant surgeon with an assistant present. For M-TKAs, a measured resection technique was used. For all RA-TKAs, the MAKO robotic system (Stryker, USA) was used. Tourniquet time was measured from inflation immediately prior to skin incision to deflation after placement of the final polyethylene insert. Procedures performed by a consulting surgeon with a surgical assist were used as controls for procedures performed by the trainee. In trainee-conducted procedures, the trainee is responsible for performing all critical aspects of the procedure while the consulting surgeon provides supervision and acts as first assist. RESULTS: 103 M-TKA and 96 RA-TKA were included. Tourniquet time was significantly longer for RA-TKAs vs M-TKAs (100 vs 89 minutes, P < .0001). However, there were no significant differences in tourniquet times between surgery performed by a trainee vs the consulting surgeon with surgical assist for either M-TKA (P = .3452) or RA-TKA (P = .6724). CONCLUSIONS: While RA-TKA takes longer, orthopedic trainees do not add additional time. Trainees at all stages of postgraduate learning can be educated in the use of robotic technology and potentially benefit from real-time feedback without further compromising surgical efficiency or increasing patient risk.

Is There an Optimal Cutoff for Aspiration Fluid Volume in the Diagnosis of Periprosthetic Joint Infection?

BACKGROUND: The diagnosis of periprosthetic joint infection is often challenging in the setting of low aspiration volumes, or in the presence of infection with a slow-growing organism. We sought to determine if an optimal threshold of aspiration fluid volume exists when cultures from the preoperative aspiration are compared to intraoperative cultures. METHODS: All revision total hip and knee arthroplasty procedures over 5 years at our institution were reviewed. Cases were excluded if they underwent joint lavage during aspiration, had an antibiotic spacer in place, were suspected of adverse local tissue reaction to metal debris, did not have an accurate aspiration volume recorded, or if there were no aspiration or operative cultures available. Receiver operating characteristic curves were used to evaluate aspiration volume for identifying cases with identical aspiration and culture results. RESULTS: A total of 857 revision cases were reviewed, among which 294 met inclusion criteria. There were 45 cases (15.3%) with discordant aspiration and operative cultures. The mean aspiration volume for identical cases was significantly higher than for discordant cases (19.1 vs 10.2 mL, P = .02). The proportion of slow-growing organisms was significantly greater among discordant compared to identical operative cultures (52.4% for discordant cases vs 8.2% for identical cases, P < .001). The optimal cutoff value for predicting identical cultures was 3.5 mL for typical organisms and 12.5 mL for slow-growing organisms. CONCLUSION: Aspiration cultures are more likely to correlate with intraoperative cultures with higher aspiration volumes, and the optimal aspiration volume is higher for slow-growing organisms.

The Clinical and Financial Consequences of the Centers for Medicare and Medicaid Services' Two-Midnight Rule in Total Joint Arthroplasty.

BACKGROUND: To lessen the financial burden of total joint arthroplasty (TJA) and encourage shorter hospital stays, the Centers for Medicare and Medicaid Services (CMS) recently removed TKA from the inpatient-only list. This policy change now requires providers and institutions to apply the two-midnight rule (TMR) to short-stay (1-midnight) inpatient hospitalizations (SSIH). METHODS: The National Inpatient Sample from 2012 through 2016 was used to analyze trends in length of stay following elective TJA. Using publically-available policy documentation, published median Medicare payments, and National Inpatient Sample hospital costs, we analyzed the application of the TMR to SSIHs and compared the results to the previous policy environment. Specifically, we modeled 3 scenarios for all 2016 Medicare SSIHs: (1) all patients kept an extra midnight to satisfy the TMR, (2) all patients discharged as an outpatient, and (3) all patients discharged as an inpatient. RESULTS: The overall percentage of Medicare SSIHs increased significantly from 2.7% in 2012 to 17.8% in 2016 (P < .0001). Scenario 1 resulted in no change in out-of-pocket (OOP) costs to patients, no change in CMS payments, and hospital losses of $117.0 million. Scenario 2 resulted in no change in patient OOP costs, reduction in payments from CMS of $181.8 million, and hospital losses of $357.3 million. Scenario 3 resulted in no change in patient OOP costs, no change in CMS payments, and an estimated $1.71 billion of SSIH charges at risk to hospitals for audit. CONCLUSION: The results of this analysis reveal the conflict between length of stay trends following TJA and the imposition of the TMR.

Can a Convolutional Neural Network Classify Knee Osteoarthritis on Plain Radiographs as Accurately as Fellowship-Trained Knee Arthroplasty Surgeons?

BACKGROUND: Osteoarthritis (OA) is the leading cause of disability among adults in the United States. As the diagnosis is based on the accurate interpretation of knee radiographs, use of a convolutional neural network (CNN) to grade OA severity has the potential to significantly reduce variability. METHODS: Knee radiographs from consecutive patients presenting to a large academic arthroplasty practice were obtained retrospectively. These images were rated by 4 fellowship-trained knee arthroplasty surgeons using the International Knee Documentation Committee (IKDC) scoring system. The intraclass correlation coefficient (ICC) for surgeons alone and surgeons with a CNN that was trained using 4755 separate images were compared. RESULTS: Two hundred eighty-eight posteroanterior flexion knee radiographs (576 knees) were reviewed; 131 knees were removed due to poor quality or prior TKA. Each remaining knee was rated by 4 blinded surgeons for a total of 1780 human knee ratings. The ICC among the 4 surgeons for all possible IKDC grades was 0.703 (95% confidence interval [CI] 0.667-0.737). The ICC for the 4 surgeons and the trained CNN was 0.685 (95% CI 0.65-0.719). For IKDC D vs any other rating, the ICC of the 4 surgeons was 0.713 (95% CI 0.678-0.746), and the ICC of 4 surgeons and CNN was 0.697 (95% CI 0.663-0.73). CONCLUSIONS: A CNN can identify and classify knee OA as accurately as a fellowship-trained arthroplasty surgeon. This technology has the potential to reduce variability in the diagnosis and treatment of knee OA.

Screening for Periprosthetic Joint Infections With ESR and CRP: The Ideal Cutoffs.

BACKGROUND: The purpose of this study was to (1) determine the sensitivity and specificity of erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) when screening for a periprosthetic joint infection (PJI) using the standard MSIS cutoff of 30 mm/h and 10 mg/L, respectively, and (2) determine the optimal ESR and CRP cutoff to achieve a sensitivity ≥95%. METHODS: We retrospectively analyzed 81 PJI patients and 83 noninfected arthroplasty patients. We calculated the sensitivity and specificity (and 95% confidence intervals) for ESR and CRP at thresholds of 30 mm/h and 10 mg/L, respectively. We determined the optimal cutoff for both ESR and CRP to yield a sensitivity greater than or equal to 95%. RESULTS: The ESR cutoff that resulted in a sensitivity ≥ to 95% (95% CI: 85.2-97.6%) was 10 mm/h, and the CRP cutoff that resulted in a sensitivity ≥ to 95% (95% CI: 87.1-98.4%) was 5 mg/L. The sensitivity and specificity with a combined ESR and CRP of 10 mm/h and 5 mg/L was 100% (95% CI: 94.1-100%) and 54.7% (95% CI: 46.4-62.3%). CONCLUSION: When using ESR and CRP as a screening tool with the accepted cutoffs of 30 mm/h and 10 mg/L, there is an unacceptably low sensitivity and a high number of false negatives. Therefore, further recommendation must be given to lowering these thresholds to avoid the devastating morbidity of a missed PJI. LEVEL OF EVIDENCE: III.

Frequency, Cost, and Clinical Significance of Incidental Findings on Preoperative Planning Images for Computer-Assisted Total Joint Arthroplasty.

BACKGROUND: The frequency of incidental findings with computer-assisted total joint arthroplasty (CA TJA) preoperative imaging and their clinical significance are currently unknown. METHODS: We reviewed 573 patients who underwent primary CA TJA requiring planning imaging. Incidental findings were defined as reported findings excluding those related to the planned arthroplasty. Secondary outcomes were additional tests or a delay in surgery. Associated charges were obtained from our institution's website. Charge and incidence data were combined with TJA volumes obtained from the 2016 National Inpatient Sample to model costs to the healthcare system. RESULTS: Overall, 262 patients (45.7%) had at least 1 incidental finding, 144 patients (25.1%) had 2, and 65 (11.3%) had 3. The most common finding types were musculoskeletal (MSK, 67.7%), digestive (19.5%), cardiovascular (4.9%), and reproductive (4.7%). Also, 9.3% of patients had at least 1 non-MSK incidental finding. Both MSK and non-MSK incidental findings were more common with total hip arthroplasty compared to total knee arthroplasty (67.9% vs 42.2%, P < .0001, and 15.4% vs 8.3%, P < .05, respectively). Further testing was required in 6 cases (1.0%); 1 case required delay in surgery (0.2%). Using the 2016 volume of TJA procedures and assuming a 10%, 15%, and 25%, utilization rate of image-based CA TJA, the annual cost of additional testing was $2.7 million (95% confidence interval, $1.1-$6.3 million), $4.1 million ($1.6-$9.5 million), and $6.9 million (95% confidence interval, $2.7-$15.8 million), respectively. CONCLUSION: Incidental findings are relatively common on planning images. Stakeholders should be aware of the hidden costs of incidental findings given the increasing popularity of image-based CA TJA.

Measuring Tibial Component Rotation Following Total Knee Arthroplasty: What Is the Best Method?

BACKGROUND: Tibial component malrotation is associated with pain, stiffness, and altered patellofemoral kinematics in total knee arthroplasty (TKA). However, measuring tibial component rotation following TKA is difficult. Proposed protocols utilizing computed tomography (CT) lack validity and can be time-consuming. This study aimed to (1) compare the reproducibility of the Berger (two-dimensional CT) and Mayo (three-dimensional CT) protocols and (2) validate a simple measurement technique using an anatomical distance on two-dimensional axial CT-the Center of the Tibial tray to the tip of the Tibial Tubercle (CTTT). METHODS: Rotational alignment of 70 TKA patients was evaluated by 3 independent observers using the Berger, Mayo, and CTTT protocols. The inter-rater and intra-rater interclass correlation coefficients, mean difference between measurements, and the mean measurement times were calculated. RESULTS: The intra-rater reliability for all 3 protocols was rated as "very good" (Mayo 0.96, Berger 0.85, and CTTT 0.85). The inter-rater reliability for the Mayo and the Berger method was rated as "very good" (0.87 and 0.83, respectively), and the CTTT was rated as "good" (0.79). Comparing the CTTT to the Mayo method produced an r2 value of 0.73 with 92% of CTTT measurements ≤6 mm having <9° of tibial component internal rotation and 93% of patients with a CTTT ≥10 mm having ≥9° internal rotation. CONCLUSION: Three-dimensional CT is the gold standard for measuring tibial component rotational alignment. The CTTT has the strongest correlation to the Mayo method and can be reliably used as a rapid screening tool.

Accuracy of a New Robotically Assisted Technique for Total Knee Arthroplasty: A Cadaveric Study.

BACKGROUND: Although the utility of robotic surgery has already been proven in cadaveric studies, it is our hypothesis that this newly designed robotically assisted system will achieve a high level of accuracy for bone resection. Therefore, we aimed to analyze in a cadaveric study the accuracy to achieve targeted angles and resection thickness. METHODS: For this study, 15 frozen cadaveric specimens (30 knees) were used. In this study, Zimmer Biomet (Warsaw, IN) knees, navigation system, and robot (ROSA Knee System; Zimmer Biomet) were used. Eight trained, board-certified orthopedic surgeons performed robotically assisted total knee arthroplasty implantation using the same robotic protocol with 3 different implant designs. The target angles obtained from the intraoperative planning were then compared to the angles of the bone cuts performed using the robotic system and measured with the computer-assisted system considered to be the gold standard. For each bone cut the resection thickness was measured 3 times by 2 different observers and compared to the values for the planned resections. RESULTS: All angle mean differences were below 1° and standard deviations below 1°. For all 6 angles, the mean differences between the target angle and the measured values were not significantly different from 0 except for the femoral flexion angle which had a mean difference of 0.95°. The mean hip-knee-ankle axis difference was -0.03° ± 0.87°. All resection mean differences were below 0.7 mm and standard deviations below 1.1mm. CONCLUSION: Despite the fact that this study was funded by Zimmer Biomet and only used Zimmer Biomet implants, robot, and navigation tools, the results of our in vitro study demonstrated that surgeons using this new surgical robot in total knee arthroplasty can perform highly accurate bone cuts to achieve the planned angles and resection thickness as measured using conventional navigation.

Two-Stage Debridement With Prosthesis Retention for Acute Periprosthetic Joint Infections.

BACKGROUND: Historically, infection control rates with debridement and component retention have been poor in the management of acute prosthetic joint infections. We previously described a 2-stage debridement with prosthesis retention protocol for acute periprosthetic joint infection and reported a 90% success rate in a sample of 20 patients. METHODS: A retrospective review of 83 patients who underwent a 2-stage debridement with implant retention with a minimum 1-year follow-up was performed. Patient data were primarily analyzed to determine infection control rates. Infections were considered controlled when patients had not undergone a reoperation for infection, and demonstrated lack of any clinical signs or symptoms of infection (a well healed wound, diminishing swelling and warmth, absence of erythema, improvement in baseline pain symptoms) A secondary goal of this study was to examine the effects of symptom duration on infection control rate. RESULTS: Average patient follow-up was 41.8 months (range 12-171) for all patients. The overall protocol success rate was 86.7% (72/83): 82.9% in hips and 89.6% in knees. Additionally, protocol success was observed in 45 of 48 primary joints (93.8%) and 27 of 35 (77.1%) revision joints (P = .046). Average time from onset of symptoms to surgery was 6.2 days for successfully treated patients (range 0-27 days) compared to 10.7 days for those who failed treatment (range 1-28 days, P = .070). CONCLUSION: This 2-stage retention protocol resulted in a higher likelihood of infection control compared to prior reports of single stage debridement and modular part exchange.

The John N. Insall Award: Higher Tissue Concentrations of Vancomycin Achieved With Intraosseous Regional Prophylaxis in Revision TKA: A Randomized Controlled Trial.

BACKGROUND: In primary TKA, prophylaxis with low-dose vancomycin through intraosseous regional administration (IORA) achieves tissue concentrations six to 10 times higher than systemic administration and was shown to provide more effective prophylaxis in an animal model. However, in revision TKA, the presence of a tibial implant may compromise IORA injection, and tourniquet deflation during a prolonged procedure may lower tissue concentrations. QUESTIONS/PURPOSES: (1) Does low-dose IORA reliably provide equal or higher tissue concentrations of vancomycin compared with systemic IV administration in revision TKA? (2) Are tissue concentrations of vancomycin after IORA maintained for the duration of the revision TKA despite a period of tourniquet deflation? (3) Is there any difference in early postoperative (< 6 weeks) complications between IORA and systemic IV administration in revision TKA? METHODS: Twenty patients undergoing aseptic revision TKA were randomized to two groups. The IV group received 1 g systemic IV prophylactic vancomycin. The IORA group received 500 mg vancomycin as a bolus injection into a tibial intraosseous cannula below an inflated thigh tourniquet before skin incision. In all patients receiving IORA, intraosseous tibial injection was technically possible despite the presence of a tibial implant. Mean procedure length was 3.5 hours in both groups. Mean initial tourniquet inflation was 1.5 hours with a second inflation for a mean of 35 minutes during cementation. During the procedure, subcutaneous fat and bone samples were taken at regular intervals. Tissue vancomycin concentrations were measured using high-performance liquid chromatography. RESULTS: Overall geometric mean tissue concentration of vancomycin in fat samples was 3.7 µg/g (95% confidence interval [CI], 2.6-5.2) in the IV group versus 49.3 µg/g in the IORA group (95% CI, 33.2-73.4; ratio between means 13.5; 95% CI, 8.2-22.0; p < 0.001); mean tissue concentrations in femoral bone were 6.4 µg/g (95% CI, 4.5-9.2) in the IV group versus 77.1 µg/g (95% CI, 42.4-140) in the IORA group (ratio between means 12.0; 95% CI, 6.2-23.2; p < 0.001). Vancomycin concentrations in the final subcutaneous fat sample taken before closure were 5.3 times higher in the IORA group versus the IV group (mean ± SD, 18.2 ± 11.6 µg/g IORA versus 3.6 ± 2.5 µg/g; p < 0.001). The intraarticular concentration of vancomycin on postoperative Day 1 drain samples was not different between the two groups with the numbers available (mean 4.6 µg/L in the IV group versus 6.6 µg/g in the IORA group; mean difference 2.0 µg/g; 95% CI, 6.2-23.2; p = 0.08). CONCLUSIONS: IORA administration of vancomycin in patients undergoing revision TKA resulted in tissue concentrations of vancomycin five to 20 times higher than systemic IV administration despite the lower dose. High tissue concentrations were maintained throughout the procedure despite a period of tourniquet deflation. These preliminary results justify prospective cohort studies, which might focus on broader safety endpoints in more diverse patient populations. We believe that these studies should evaluate patients undergoing revision TKA in particular, because the risk of infection is greater than in patients undergoing primary TKA. LEVEL OF EVIDENCE: Level I, therapeutic study.