Culture-positive (CP) and culture-negative (CN) periprosthetic joint infections (PJI) remain a crucial area of research; however, current studies comparing these infections rely on unstandardized outcome reporting tools. Our study aimed to compare the outcomes of two-stage revision of CP and CN PJI using the standardized Musculoskeletal Infection Society (MSIS) outcome reporting tool. We retrospectively reviewed 138 patients who were diagnosed with PJI and indicated for two-stage revision total knee arthroplasty (rTKA). The majority of patients in both CP and CN cohorts achieved infection control without the need for reoperation (54.1% and 62.5%, respectively). There was a significant difference in the overall distribution of MSIS outcomes (p = 0.043), with a significantly greater rate of CN patients falling into Tier 1 (infection control without the use of suppressive antibiotics) (52.5% versus 29.6%, p = 0.011). There was also a significant difference in the distribution of septic versus aseptic reoperations after 2nd stage (p = 0.013), with more CP reoperations being septic and more CN reoperations being aseptic. The duration from first to second stage was significantly shorter in the CN cohort (p = 0.002). While overall infection control was similar between cohorts, these data suggest that the outcomes of two-stage rTKA are favorable in cases of CN PJI.

Patient satisfaction is becoming an increasingly important measure of healthcare quality. Satisfaction following RTKA is poorly described within the literature, resulting in difficulty for clinicians to manage patient expectations and obtain informed consent.
We investigated postoperative satisfaction of RTKA patients by a single surgeon, using a single prosthesis, at a single institution. Patient satisfaction was assessed using structured telephone assessment questionnaires and review of orthopaedic/hospital records. The effect of patient and surgical characteristics on satisfaction was assessed using correlation coefficients and binary logistic regression in SPSS.
Two hundred and two RTKAs were performed in 178 patients between 2004 and 2015 inclusive. One hundred and twenty-four patients (143 RTKAs) were contactable to complete satisfaction assessment. Eighty-five percent of patients were satisfied and would have the RTKA again, 8% were unsure, 7% would not. Mean reported satisfaction on a numerical scale (1-10) was 8.17 (range 1-10), with 74% of patients scoring 8 or above, and 35% of patients scoring 10. The Mahomed Satisfaction Scale outcomes demonstrated a mean score of 87.7. High positive correlation was found between assessment tools. Logistic regression analysis identified factors contributing to satisfaction included ROM, OKS, BMI, and surgical time.
This cohort demonstrated high patient satisfaction rate following RTKA, utilizing simple and reliable outcome measurement tools. We found a high positive correlation between methods of assessment, and moderate positive correlation between satisfaction and functional outcomes. These results contribute to the understanding of satisfaction in RTKA patients, which may assist in informing patients of expected post-operative outcomes.

OBJECTIVE: Arthrofibrosis after primary total knee arthroplasty (TKA) is a significant contributor to patient dissatisfaction. While treatment algorithms involve early physical therapy and manipulation under anaesthesia (MUA), some patients ultimately require revision TKA. It is unclear whether revision TKA can consistently improve these patient\'s range of motion (ROM). The purpose of this study was to evaluate ROM when revision TKA was performed for arthrofibrosis.
METHODS: A retrospective study of 42 TKA\'s diagnosed with arthrofibrosis from 2013 to 2019 at a single institution with a minimum 2-year follow-up was performed. The primary outcome was ROM (flexion, extension, and total arc of motion) before and after revision TKA, and secondary outcomes included patient reported outcomes information system (PROMIS) scores. Categorical data were compared using chi-squared analysis, and paired samples t tests were performed to compare ROM at three different times: pre-primary TKA, pre-revision TKA, and post-revision TKA. A multivariable linear regression analysis was performed to assess for effect modification on total ROM.
RESULTS: The patient\'s pre-revision mean flexion was 85.6 degrees, and mean extension was 10.1 degrees. At the time of the revision, the mean age of the cohort was 64.7 years, the average body mass index (BMI) was 29.8, and 62% were female. At a mean follow-up of 4.5 years, revision TKA significantly improved terminal flexion by 18.4 degrees (p < 0.001), terminal extension by 6.8 degrees (p = 0.007), and total arc of motion by 25.2 degrees (p < 0.001). The final ROM after revision TKA was not significantly different from the patient\'s pre-primary TKA ROM (p = 0.759). PROMIS physical function, depression, and pain interference scores were 39 (SD = 7.72), 49 (SD = 8.39), and 62 (SD = 7.25), respectively.
CONCLUSIONS: Revision TKA for arthrofibrosis significantly improved ROM at a mean follow-up of 4.5 years with over 25 degrees of improvement in the total arc of motion, resulting in final ROM similar to pre-primary TKA ROM. PROMIS physical function and pain scores showed moderate dysfunction, while depression scores were within normal limits. While physical therapy and MUA remain the gold standard for the early treatment of stiffness after TKA, revision TKA can improve ROM.
METHODS: IV.

The purpose of this study was to determine if elevated pre-operative D-dimer levels in patients undergoing revision total knee arthroplasty (rTKA) pose an increased risk of: (1) post-operative venous thromboemboli (VTE); (2) intra-operative blood loss; and (3) need for transfusion of blood products. Eighty-nine patients who underwent rTKA by a single surgeon between January 1, 2017, and December 31, 2019, met the inclusion criteria. Elevated pre-operative D-dimer levels did not pose an increased risk of VTE, blood loss, or transfusion of blood products, demonstrating that elevated pre-operative D-dimer is not a contraindication to the use of tranexamic acid for rTKA.

BACKGROUND: In this study, the traditional \"Anatomical Landmark-Distance Method (AL-DM)\" in the formation of joint line (JL) was compared with \"Adductor Tubercle-Ratios method\" (AT-RM), and the effect of reestablishment of JL on clinical and functional outcomes were evaluated.
METHODS: 16 revision total knee arthroplasties (rTKAs) were performed by using \"AT-RM\" (group 1) and 16 rTKA by using \"AL-DM\" (group 2) in our clinic between 2015 and 2018. The data were prospectively collected and a total of 32 knees of 31 patients were analyzed. At the final follow-up, knee functions were evaluated by using Knee Society Score (KSS) knee and function, Western Ontario and McMaster Universities Arthritis Index (WOMAC) scores, Short Form-36 (SF-36) questionnaires and physical examinations.
RESULTS: Postoperative flexion arc was higher in Group 1. KSS knee and function scores were better in group 1. In group1, JL was reestablished successfully in all revision rTKAs in terms of ATJL and the tibial tubercle TT-JL ratios. The improvement in KSS knee and function scores and WOMAC scores were also better in group 1. Measurements showed that the improvement in KSS scores increased as AT-JL and TT-JL distances approached the calculated values.
CONCLUSIONS: \"AT-RM\" was shown to be superior to the traditional distance method in terms of JL reestablishment. Functional results and patient satisfaction increased when JL was reestablished.

Periprosthetic joint infection (PJI) remains one of the most common causes of revision knee arthroplasty. Controversy continues to surround the proper operative technique of PJI in knee arthroplasty with single- or two-stage replacement. Significant variations are seen in the eradication rates of PJI and in implant survival rates. This detailed retrospective analysis of a single tertiary center is intended to provide further data and insight comparing single- and two-stage revision surgery. A retrospective analysis of all revision total knee arthroplasty (TKA) surgeries from 2013 to 2019 was performed and screened with respect to single- or two-stage TKA revisions. Single- and two-stage revisions were analyzed with regard to implant survival, revision rate, microbiological spectrum, and other typical demographic characteristics. A total of 63 patients were included, with 15 patients undergoing single-stage revision and 48 patients undergoing two-stage revision. The mean follow-up time was 40.7 to 43.7 months. Statistically, no difference was found between both groups in overall survival (54.4% vs. 70.1%, p = 0.68) and implant survival with respect to reinfection (71.4% vs. 82.4%, p = 0.48). Further, high reinfection rates were found for patients with difficult-to-treat organisms and low- to semi-constrained implant types, in comparison to constrained implant types. A statistically comparable revision rate for recurrence of infection could be shown for both groups, although a tendency to higher reinfection rate for single-stage change was evident. The revision rate in this single-center study was comparably high, which could be caused by the high comorbidity and high proportion of difficult-to-treat bacteria in patients at a tertiary center. In this patient population, the expectation of implant survival should be critically discussed with patients.

OBJECTIVE: Histology is an established tool in diagnosing periprosthetic joint infections (PJIs). Different thresholds, using various infection definitions and histopathological criteria, have been described. This study determined the performance of different thresholds of polymorphonuclear neutrophils (≥ 5 PMN/HPF, ≥ 10 PMN/HPF, ≥ 23 PMN/10 HPF) , when using the European Bone and Joint Infection Society (EBJIS), Infectious Diseases Society of America (IDSA), and the International Consensus Meeting (ICM) 2018 criteria for PJI.
METHODS: A total of 119 patients undergoing revision total hip (rTHA) or knee arthroplasty (rTKA) were included. Permanent histology sections of periprosthetic tissue were evaluated under high power (400× magnification) and neutrophils were counted per HPF. The mean neutrophil count in ten HPFs was calculated (PMN/HPF). Based on receiver operating characteristic (ROC) curve analysis and the z-test, thresholds were compared.
RESULTS: Using the EBJIS criteria, a cut-off of ≥ five PMN/HPF showed a sensitivity of 93% (95% confidence interval (CI) 81 to 98) and specificity of 84% (95% CI 74 to 91). The optimal threshold when applying the IDSA and ICM criteria was ≥ ten PMN/HPF with sensitivities of 94% (95% CI 79 to 99) and 90% (95% CI 76 to 97), and specificities of 86% (95% CI 77 to 92) and 92% (95% CI 84 to 97), respectively. In rTKA, a better performance of histopathological analysis was observed in comparison with rTHA when using the IDSA criteria (p < 0.001).
CONCLUSIONS: With high accuracy, histopathological analysis can be supported as a confirmatory criterion in diagnosing periprosthetic joint infections. A threshold of ≥ five PMN/HPF can be recommended to distinguish between septic and aseptic loosening, with an increased possibility of detecting more infections caused by low-virulence organisms. However, neutrophil counts between one and five should be considered suggestive of infection and interpreted carefully in conjunction with other diagnostic test methods. Cite this article: Bone Joint Res 2021;10(8):536-547.

BACKGROUND: Revision total knee arthroplasty after multiple pre-surgeries is challenging. Due to severe bone defects, standard implants for metaphyseal and diaphyseal anchoring may no longer be suitable. The primary aim of this case series is to evaluate the early complication rate for individual knee implants with custom-made cones and stems after two-stage revision with severe bone defects.
METHODS: Ten patients who were treated with custom-made 3D-printed knee revision implants were included. Inclusion criteria were a two-stage revision due to late-onset or chronic periprosthetic joint infection as well as aseptic loosening. All severe bone defects were AORI type III. All procedure-related complications were evaluated. Postoperative range of motion after one year was measured. The time between the two surgeries was evaluated.
RESULTS: The mean follow-up was 21 months (range: 12-40). The mean time between the two-stage surgeries was 71.6 days. No fractures were observed intra- and postoperatively. Two patients were revised without changing metal components due to persistent hematoma (three weeks post-surgery) and persistent PJI (three months post-surgery). The mean passive postoperative range of motion was 92° (range: 80-110°).
CONCLUSIONS: Individual custom-made implants for rTKA provide a safe procedure for patients with huge bone defects after several pre-surgeries. If standard knee systems with standard cones or sleeves are not suitable anymore, custom-made treatment offers the patient the last option for limb preservation. However, this is associated with increased costs.

We report the successful use of allograft-prosthesis composite (APC) and structural femoral head allografting in the bilateral reconstruction of large femoral and tibial uncontained defects during revision total knee arthroplasty (RTKA).
A 67-year-old female with degenerative arthritis underwent bilateral total knee arthroplasty (TKA) using the Press Fit Condylar (PFC) modular knee system at our clinic in March, 1996. At 8 years postoperatively, the patient presented with painful, bilateral varus knees, with swelling, limited passive range of motion (ROM), and severe instability. We treated to reconstruct both knee using a femoral head allograft at the tibial site, a structural distal femoral allograft at the femoral site, and a varus-valgus constrained (VVC) prosthesis with cement. At the 10-year follow up, we found no infection, graft failure, loosening of implants, in spite of using massive bilateral structural femoral head allografts in RTKA.
The use of APC enabled a stable and durable reconstruction in this uncommon presentation with large femoral bone deficiencies encountered during a RTKA.

BACKGROUND: Revision total knee arthroplasty with a cementless metaphyseal sleeve is suggested to be used without stem in revision total knee arthroplasty (rTKA). To the best of our knowledge, no papers investigating this have been published. The purpose of this study was to evaluate clinical outcome.
METHODS: In this retrospective study, 71 patients operated with rTKA with sleeves without stem in the period 2009-2011 were identified; 63 were examined. All patients with the prosthesis still in place were invited to a medical examination including X-rays. American Knee Society Score (AKSS) and Oxford Knee Score (OKS) were used as primary clinical outcome scores.
RESULTS: Mean number of revisions including the revision with sleeve was 1.7. AKSS increased significantly from 62.7 to 109.6; (p value <0.0001). The overall satisfaction was 2.5 on a four-stage scale, going from very satisfied to dissatisfied (range 1-4). The Anderson Orthopaedic Research Institute (AORI) classification showed 63 % of the tibias and 56 % of the femurs to be type 2B, whereas 19 % tibias and 5 % femurs were type 3. Review of the X-rays showed all prostheses fixed. Mean tibiofemoral alignment was 6.0° valgus, and 51 % were outside optimal alignment (2.4°-7.2°). Six patients were excluded from the study.
CONCLUSIONS: We found that the prostheses were overall well fixed and patients\' AKSS increased significantly. Many patients had pain conditions, both comorbid pain and pain that might be alignment-related, and adding a stem thus seems to be a good idea in terms of alignment. Level of evidence Level IV, case series without control group.