Comparison of Delphi Consensus Criteria and Musculoskeletal Infection Society Outcome Reporting Tool Definitions of Successful Surgical Treatment of Periprosthetic Knee Infection.

BACKGROUND: Agreement on success following surgical treatment for periprosthetic joint infection (PJI) is important for comparing the efficacy of different surgical approaches with varying consequences and outcomes and setting patient expectations. We compared success rates following two-stage exchange arthroplasty for knee PJI using two expert-consensus definitions of success. METHODS: Prospectively documented data for 57 knees treated by a single surgeon at an academic tertiary care center were retrospectively reviewed. Treatment outcomes were quantified using the Delphi Consensus Criteria and the Musculoskeletal Infection Society Outcome Reporting Tool (MSIS ORT). RESULTS: Success rates were 81% using the Delphi Consensus Criteria and 56% using the MSIS ORT (P = .008). The MSIS ORT success rates increased to 76% when aseptic revisions and deaths unrelated to PJI were not penalized as failures of treatment. Predicted probabilities of successful treatment in a hypothetical case scenario were lowest based on the MSIS ORT and similarly higher using Delphi Consensus Criteria and MSIS ORT modified for both women (53.0, 90.8, and 88.7%) and men (29.1, 89.1, and 89.3%). CONCLUSIONS: Study observations underscore the need for a uniformly accepted single definition of surgical treatment success.

The Fate of Zone 2 Radiolucencies in Contemporary Highly Porous Acetabular Components: Not All Designs Perform Equally.

BACKGROUND: The enhanced frictional resistance of modern ultraporous acetabular components can impede complete seating; however, surgeons expect the enhanced ingrowth surface to resolve polar (zone 2) gaps over time via osseointegration. This study characterized zone 2 radiographic osseointegration in 3 acetabular component designs: 2 highly porous ingrowth and one traditional ongrowth. METHODS: A consecutive cohort of primary total hip arthroplasties was reviewed which utilized 3 different acetabular cup designs: ongrowth titanium with hydroxyapatite (HA), highly porous titanium with machined radial grooves (MRG), and dual-porous titanium substrate with micropore (MP). Radiographic analysis was performed using accepted measurement criteria with particular attention to radiolucent lines. RESULTS: Seven hundred ninety cases were available for analysis. Initial 1-month radiographs revealed 43.2% of HA, 78.2% of MRG, and 81.0% of MP cups exhibited zone 2 radiolucencies, consistent with incomplete seating. At 1 year, all HA radiolucencies resolved, whereas 46.2% and 34.7% of radiolucencies remained in MRG and MP cups, respectively (P ≤ .005). At minimum 2 years, a significant proportion of zone 2 radiolucencies remained in 46.0% of MRG compared with 23.9% of MP cups and 3.0% of HA cups (P ≤ .007). CONCLUSION: The resolution of zone 2 radiolucencies at 1-year and minimum 2-year follow-up signified osseointegration for nearly all HA and most MP cups. Highly porous titanium cups with machined radial grooves demonstrated persistent zone 2 radiolucencies at 1 year and beyond. Given reports of early loosening with this particular acetabular implant, further follow-up is warranted as this study highlights that not all contemporary highly porous metal acetabular components perform equally. LEVEL OF EVIDENCE: III.

Contemporary 2-Stage Treatment of Periprosthetic Hip Infection with Evidence-Based Standardized Protocols Yields Excellent Results: Caveats and Recommendations.

BACKGROUND: This study quantified the effectiveness of contemporary and evidence-based standardized 2-stage treatment for periprosthetic hip infection. Findings illustrate potential limitations of criticisms of 2-stage protocols and potential consequences of adopting single-stage protocols before definitive data are available. METHODS: Fifty-four consecutive hips treated with 2-stage resection and reimplantation were retrospectively reviewed. Standardized protocols were adhered to including implant resection, meticulous surgical debridement, antibiotic spacer, 6-week intravenous antibiotics, a 2-week drug holiday, and laboratory assessment of infection eradication before reimplantation. After reimplantation, patients were placed on prophylactic intravenous antibiotics until discharge and discharged on oral antibiotics for a minimum of 7 days until intraoperative cultures were final. Successful treatment was defined per Delphi-based International Multidisciplinary Consensus. RESULTS: The overall treatment success rate was 95.7% (44 of 46 cases) with mean infection-free survivorship of 67.2 (range, 23.8-106.4) months. Success rates were 100% for early and acute hematogenous infections regardless of host type and 100% for chronic infections in uncompromised hosts. 95% (19/20) of chronic infections in compromised hosts and 83.3% (5/6) of chronic infections in significantly compromised hosts were successfully treated. About 4% of primary hips and 20% of revision hips required repeat debridement and spacer exchange after initial resection. No patients died because of treatment. CONCLUSION: Details from this consecutive series of patients undergoing 2-stage treatment for hip infection suggest that some criticisms of 2-stage treatment as well as some arguments in support of single-stage treatment may be overstated. Promotion and uncritical adoption of single-stage treatment protocols are discouraged until further and more definitive data exist.

Do Antibiotic Intramedullary Dowels Assist in Eradicating Infection in Two-Stage Resection for Septic Total Knee Arthroplasty?

BACKGROUND: Evidence suggests approximately 40% of intramedullary (IM) canals are culture positive at resection for infected knee arthroplasty. While commonly utilized, no clinical data on the efficacy of antibiotic-eluding IM dowels exist. We quantified treatment success with and without the use of antibiotic-eluding IM dowels in two-stage treatment of periprosthetic knee infection using static and articulating antibiotic cement spacers. METHODS: 109 consecutive patients who underwent two-stage treatment for periprosthetic knee infection were reviewed. Treatment failure, defined as repeat resection before reimplantation or recurrent infection within 6 months of reimplantation, was evaluated based on spacer type and use of IM dowels, accounting for infection type and systemic host and local extremity grade. RESULTS: After exclusions for confounds, articulating spacers without IM dowels were used in 49 (57.7%) cases, articulating spacers with IM dowels in 14 cases (16.5%), and static spacers with IM dowels in 22 (25.9%) cases. Treatment success regardless of infection classification was 85.7% for articulating spacers with IM dowels, 89.8% for articulating spacers without IM dowels, and 68.2% for static spacers with IM dowels (P = .074). In chronically infected poor hosts with compromised extremities, treatment success remained highest in patients with articulating spacers with (90.9%) or without (92.9%) IM dowels compared with static spacers with IM dowels (68.4%) (P = .061). CONCLUSION: Findings suggest that the use of IM dowels did not enhance infection eradication above and beyond that observed for articulating spacers alone, including in the worst cases involving chronically infected poor hosts with compromised extremities.