Current Insights in the Evaluation and Treatment of Infected Total Knee Arthroplasty.

Total knee arthroplasty is a widely successful procedure, but a small percentage of patients have a postoperative course complicated by periprosthetic joint infection (PJI). PJI is a difficult problem to diagnose and to treat, and the management of PJI differs, depending on the acuity of the infection. This paper discusses the established and newer technologies developed for the diagnosis of PJI as well as different treatment considerations and surgical solutions currently available.

Resorbable Pins to Enhance Scaffold Retention in a Porcine Chondral Defect Model.

OBJECTIVE: Cartilage repair strategies have seen improvement in recent years, especially with the use of scaffolds that serve as a template for cartilage formation. However, current fixation strategies are inconsistent with regards to retention, may be technically challenging, or may damage adjacent tissues or the implant itself. Therefore, the goal of this study was to evaluate the retention and repair potential of cartilage scaffolds fixed with an easy-to-implement bioresorbable pin. DESIGN: Electrospun hyaluronic acid scaffolds were implanted into trochlear groove defects in 3 juvenile and 3 adult pigs to evaluate short-term retention (2 weeks; pin fixation vs. press-fit and fibrin fixation) and long-term repair (8 months; scaffold vs. microfracture), respectively. RESULTS: For the retention study, press-fit and fibrin fixation resulted in short-term scaffold dislodgment (n = 2 each), whereas pin fixation retained all scaffolds that were implanted (n = 6). Pin fixation did not cause any damage to the opposing patellar surface, and only minor changes in the subchondral bone were observed. For long-term repair, no differences were observed between microfracture and scaffold groups, in terms of second-look arthroscopy and indentation testing. On closer visualization with micro computed tomography and histology, a high degree of variability was observed between animals with regard to subchondral bone changes and cartilage repair quality, yet each Scaffold repair displayed similar properties to its matched microfracture control. CONCLUSIONS: In this study, pin fixation did not cause adverse events in either the short- or the long-term relative to controls, indicating that pin fixation successfully retained scaffolds within defects without inhibiting repair.

Diagnosing Infection in Patients Undergoing Conversion of Prior Internal Fixation to Total Hip Arthroplasty.

BACKGROUND: Criteria for diagnosis of infected internal fixation implants at the time of conversion to total hip arthroplasty (THA) are not clear. The purpose of this study is to identify risk factors for infection in patients undergoing conversion to THA. METHODS: We retrospectively reviewed patients at a single institution who underwent conversion to THA from 2009 to 2014. Patients were diagnosed with infection preoperatively using Musculoskeletal Infection Society criteria or postoperatively if they were found to have positive cultures intraoperatively at the time of conversion surgery. Medical comorbidities and preoperative inflammatory markers were compared between infected and noninfected groups. Univariate and multivariate logistic regression analysis were performed to identify independent risk factors for infection. Receiver operating characteristic curves were generated to determine test performance of erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). A post hoc power analysis was performed. RESULTS: Thirty-three patients were included in the study. Six patients (18%) were diagnosed with infection. We found no association between comorbidities and infection in this cohort. The mean ESR and CRP were higher in infected (ESR = 41.6 mm/h, CRP = 2.0 mg/dL) vs noninfected (ESR = 19.3 mm/h, CRP = 1.3 mg/dL) groups (both P < .01). ESR >30 mm/h (odds ratio 28.8, 95% confidence interval 2.6-315.4, P = .001) and CRP >1.0 mg/dL (odds ratio 11.5, 95% confidence interval 1.6-85.2, P = .01) were strongly associated with infection. Receiver operating characteristic curves for ESR (area under the curve [AUC] = 0.89) and CRP (AUC = 0.89) demonstrated good fit. CONCLUSION: We report a high incidence of infection in patients who underwent conversion to THA. Preoperative ESR and CRP are effective screening tools though occult infections may still be missed. Patients with borderline or elevated inflammatory markers should raise strong suspicion for infection.

Are Bundled Payments a Viable Reimbursement Model for Revision Total Joint Arthroplasty?

BACKGROUND: Alternative payment models, such as the Centers for Medicare & Medicaid Services (CMS) Bundled Payment for Care Improvement (BPCI) initiative, aim to decrease overall costs for hip and knee arthroplasties. QUESTIONS/PURPOSES: We asked: (1) Is there any difference in the CMS episode-of-care costs, hospital length of stay, and readmission rate from before and after implementation of our bundled-payment program? (2) Is there any difference in reimbursements and resource utilization between revision THA and TKA at our institution? (3) Are there any independent risk factors for patients with high costs who may not be appropriate for a bundled-payment system for revision total joint arthroplasty (TJA)? METHODS: Between October 2013 and March 2015, 218 patients underwent revision TKA or THA in one health system. Two hundred seventeen patients were reviewed as part of this study, and one patient with hemophilia was excluded from the analysis as an outlier. Our institution began a BPCI program for revision TJA during this study period. Patients' procedures done before January 1, 2014 at one hospital and January 1, 2015 at another hospital were not included in the bundled-care arrangement (70 revision TKAs and 56 revision THAs), whereas 50 revision TKAs and 41 revision THAs were performed under the BPCI initiative. Patient demographics, medical comorbidities, episode-of-care reimbursement data derived directly from CMS, length of stay, and readmission proportions were compared between the bundled and nonbundled groups. RESULTS: Length of stay in the group that underwent surgery before the bundled-care arrangement was longer than for patients whose procedures were done under the BPCI (mean 4.02 [SD, 3.0 days] versus mean 5.27 days [SD, 3.6 days]; p = 0.001). Index hospitalization reimbursement for the bundled group was less than for the nonbundled group (mean USD 17,754 [SD, USD 2741] versus mean USD 18,316 [SD, USD 4732]; p = 0.030). There was no difference, with the numbers available, in total episode-of-care CMS costs between the two groups (mean USD 38,107 [SD, USD 18,328] versus mean USD 37,851 [SD, USD 17,208]; p = 0.984). There was no difference, with the numbers available, in the total episode-of-care CMS costs between revision hip arthroplasties and revision knee arthroplasties (mean USD 38,627 [SD, USD 18,607] versus mean USD 37,414 [SD, USD 16,884]; p = 0.904). Disposition to rehabilitation (odds ratio [OR], 5.49; 95% CI, 1.97-15.15; p = 0.001), length of stay 4 days or greater (OR, 3.66; 95% CI, 1.60-8.38; p = 0.002), and readmission within 90 days (OR, 6.99; 95% CI, 2.58-18.91; p < 0.001) were independent risk factors for high-cost episodes. CONCLUSIONS: Bundled payments have the potential to be a viable reimbursement model for revision TJA. Owing to the unpredictable nature of the surgical procedures, inherent high risks of complications, and varying degrees of surgical complexity, future studies are needed to determine whether bundling patients having revision TJA will result in improved care and decreased costs. LEVEL OF EVIDENCE: Level IV, economic and decision analysis.