Cefazolin remains the linchpin for preventing acute periprosthetic joint infection following primary total knee arthroplasty

Aims Despite recent literature questioning their use, vancomycin and clindamycin often substitute cefazolin as the preoperative antibiotic prophylaxis in primary total knee arthroplasty (TKA), especially in the setting of documented allergy to penicillin. Topical povidone-iodine lavage and vancomycin powder (VIP) are adjuncts that may further broaden antimicrobial coverage, and have shown some promise in recent investigations. The purpose of this study, therefore, is to compare the risk of acute periprosthetic joint infection (PJI) in primary TKA patients who received cefazolin and VIP to those who received a non-cephalosporin alternative and VIP. Methods This was a retrospective cohort study of 11,550 primary TKAs performed at an orthopaedic hospital between 2013 and 2019. The primary outcome was PJI occurring within 90 days of surgery. Patients were stratified into two groups (cefazolin vs non-cephalosporin) based on their preoperative antibiotic. All patients also received the VIP protocol at wound closure. Bivariate and multiple logistic regression analyses were performed to control for potential confounders and identify the odds ratio of PJI. Results In all, 10,484 knees (90.8%) received cefazolin, while 1,066 knees (9.2%) received a non-cephalosporin agent (either vancomycin or clindamycin) as preoperative prophylaxis. The rate of PJI in the cefazolin group (0.5%; 48/10,484) was significantly lower than the rate of PJI in the non-cephalosporin group (1.0%; 11/1,066) (p = 0.012). After controlling for confounding variables, the odds ratio (OR) of developing a PJI was increased in the non-cephalosporin cohort compared to the cefazolin cohort (OR 2.389; 1.2 to 4.6); p = 0.01). Conclusion Despite the use of topical irrigant solutions and addition of local antimicrobial agents, the use of a non-cephalosporin perioperative antibiotic continues to be associated with a greater risk of TKA PJI compared to cefazolin. Strategies that increase the proportion of patients receiving cefazolin rather than non-cephalosporin alternatives must be emphasized. Cite this article: Bone Jt Open 2022;3(1):35–41.

Intraoperative Assessment of Gap Balancing in Total Knee Arthroplasty Using Navigation with Joint Stability Graphs

The purpose of this study was to assess continuous gaps in the replaced knee throughout the full range of motion (ROM) after total knee arthroplasty (TKA) using a joint stability graph, and to analyze the gap laxity in the mid-flexion range. Ninety-three TKAs were performed using imageless navigation with a joint stability graph. While positioning guides for each respective cut, the surgeon can safely preview the resection's impact for the resulting joint gaps and control the soft tissue balance at the knee flexion of 0° (extension) and 90° (flexion). The gaps between the femoral component and insert were evaluated throughout the full ROM using the joint stability graph. The mechanical axis (MA) and change of joint line height were radiographically evaluated. Posthoc power analyses using a significant α value of 0.05 were performed on the proportion of the mid-flexion instability as a primary outcome to determine whether the sample had sufficient power. The power was determined to be sufficient (100%). The flexion–extension gap differences in each medial and lateral compartment and the mediolateral gap differences in flexion and extension were all ≤3 mm. None of the knees had mid-flexion instability, which is defined by a peak mid-flexion gap that is 3 mm greater than the smaller value of flexion or extension gap. The average MA was well corrected from varus 11.4° to varus 1.0° postoperatively. The proportion of postoperative well-aligned knees (MA ≤ 3°) was 87.1%. The joint line height was well preserved (14.7 vs. 14.8 mm, p = 0.751). The joint stability graph in TKA using the navigation can effectively evaluate the continuous gap throughout the ROM, including the mid-flexion range. Mid-flexion instability was uncommon in primary TKAs with appropriate alignment and proper preservation of the joint line. The Level of evidence for the study is IV.

Varus-valgus constrained insert with posterior-stabilized femoral components in complex primary total knee arthroplasties

Aims Varus-valgus constrained (VVC) devices are typically used in revision settings, often with stems to mitigate the risk of aseptic loosening. However, in at least one system, the VVC insert is compatible with the primary posterior-stabilized (PS) femoral component, which may be an option in complex primary situations. We sought to determine the implant survivorship, radiological and clinical outcomes, and complications when this VVC insert was coupled with a PS femur without stems in complex primary total knee arthroplasties (TKAs). Methods Through our institution’s total joint registry, we identified 113 primary TKAs (103 patients) performed between 2007 and 2017 in which a VVC insert was coupled with a standard cemented PS femur without stems. Mean age was 68 years (SD 10), mean BMI was 32 kg/m2 (SD 7), and 59 patients (50%) were male. Mean follow-up was four years (2 to 10). Results The five-year survivorship free from aseptic loosening was 100%. The five-year survivorship free from any revision was 99%, with the only revision performed for infection. The five-year survivorship free from reoperation was 93%. The most common reoperation was treatment for infection (n = 4; 4%), followed by manipulation under anaesthesia (MUA; n = 2; 2%). Survivorship free from any complication at five years was 90%, with superficial wound infection as the most frequent (n = 4; 4%). At most recent follow-up, two TKAs had non-progressive radiolucent lines about both the tibial and femoral components. Knee Society Scores improved from 53 preoperatively to 88 at latest follow-up (p < 0.001). Conclusion For complex primary TKA in occasional situations, coupling a VVC insert with a standard PS femur without stems proved reliable and durable at five years. Longer-term follow-up is required before recommending this technique more broadly. Cite this article: Bone Jt Open 2021;2(11):921–925.

Different microbial and resistance patterns in primary total knee arthroplasty infections – a report on 283 patients from Lithuania and Sweden

Background The microbiology and the susceptibility patterns of infected total knee arthroplasties (TKAs) vary depending on demographic, local antimicrobial stewardship, and surgical factors. We wanted to compare the recent microbial profile and antimicrobial resistance pattern in revisions due to infections after primary TKAs in Sweden and Lithuania. Our hypothesis was that there is a difference in bacteriology and resistance pattern based on patient related, societal and local hospital factors as almost similar praxis have been applied for TKA surgery, short term systemic prophylaxis and routine use of local gentamicin containing bone cement. Methods Primary TKAs revised for the first time due to verified or suspected infection were collected nationwide in Sweden during 2018, and in Lithuania between 2011 and 2020 from a single major TKA revision centre in Kaunas. We identified 202 TKAs in Sweden from the Swedish Knee Arthroplasty Register and 84 from Kaunas revised due to infection. We collected available culture reports and evaluated the type of microorganisms with antimicrobial resistance pattern at revision. Results The majority of the infected cases in Sweden were early-type prosthetic joint infection (PJI) (44%), whereas late-type PJI (52%) were more common in the Kaunas cases. Gram-positive bacteria prevailed in both Sweden (55%) and Lithuania (80%). Staphylococcus aureus was the most frequent organism identified in both countries (33% in Sweden and 34% in Lithuania). More polymicrobial infections were observed in Sweden than in Lithuania (16 and 6% respectively). Methicillin resistance in Staphylococcus aureus and coagulase-negative staphylococci were higher in Lithuania (4/28 and 19/29) than in Sweden (1/42 and 9/41). Conclusions The type of infections, microbial profile, and drug resistance pattern differed between Sweden and Lithuania. Societal and local hospitals factors with emerging resistance in Lithuania are the most plausible explanation for the difference. Lack of complete data on a national level in Lithuania underlines the importance of adding microbiology of PJIs in implant registers for national aggregation and allow cross country comparisons.

The long-term results of total knee arthroplasty in octogenarian

Aims: With increasing life expectancy and ageing population, more octogenarians would benefit from total knee arthroplasty (TKA). The aim of this study is to evaluate the survivorship of TKA in octogenarian and their long-term outcomes. Methods: This was a retrospective review of 67 patients aged above 80 years who had primary TKA performed between 2005 and 2013 at a single centre. A sex-matched younger cohort of 67 primary TKAs during the same time-period was recruited for control. Five and 10-year survival was calculated. Pre- and peri-operative factors were collected and compared. Post-operative range of motion, Knee Society Score (KSS) and Function Score (KFS) were collected and compared. Rate of revision, infection, aseptic loosening and mortality was collected. Results: The mean follow-up period was 10.39 ± 2.29 years. The 5- and 10-year survival of octogenarian group was 85.1% and 54.6%, respectively. Pre- and peri-operative factors between the octogenarian and control groups were comparable ( p > 0.05). Both groups showed improvement in range of motion, KSS and KFS post-operatively. Rate of revision, aseptic loosening and deep infection was 0% in octogenarian and 1.5% in control group. Conclusion: TKA can be performed in patients with age above 80 years old with comparable post-op knee range, complication rate and long-term functional score. Advanced age should not be a limiting factor for TKA.

True Kinematic Alignment Is Applicable in 44% of Patients Applying Restrictive Indication Criteria—A Retrospective Analysis of 111 TKA Using Robotic Assistance

Introduction: Image-based robotic assistance appears to be a promising tool for individualizing alignment in total knee arthroplasty (TKA). The patient-specific model of the knee enables a preoperative 3D planning of component position. Adjustments to the individual soft-tissue situation can be done intraoperatively. Based on this, we have established a standardized workflow to implement the idea of kinematic alignment (KA) for robotic-assisted TKA. In addition, we have defined limits for its use. If these limits are reached, we switch to a restricted KA (rKA). The aim of the study was to evaluate (1) in what percentage of patients a true KA or an rKA is applicable, (2) whether there were differences regarding knee phenotypes, and (3) what the differences of philosophies in terms of component position, joint stability, and early patient outcome were. Methods: The study included a retrospective analysis of 111 robotic-assisted primary TKAs. Based on preoperative long leg standing radiographs, the patients were categorized into a varus, valgus, or neutral subgroup. Initially, all patients were planned for KA TKA. When the defined safe zone had been exceeded, adjustments to an rKA were made. Intraoperatively, the alignment of the components and joint gaps were recorded by robotic software. Results and conclusion: With our indication for TKA and the defined boundaries, “only” 44% of the patients were suitable for a true KA with no adjustments or soft tissue releases. In the varus group, it was about 70%, whereas it was 0% in the valgus group and 25% in the neutral alignment group. Thus, significant differences with regard to knee morphotypes were evident. In the KA group, a more physiological knee balance reconstructing the trapezoidal flexion gap (+2 mm on average laterally) was seen as well as a closer reconstruction of the surface anatomy and joint line in all dimensions compared to rKA. This resulted in a higher improvement in the collected outcome scores in favor of KA in the very early postoperative phase.

Relative Clinical Outcomes Comparing Manual and Robotic-Assisted Total Knee Arthroplasty at Minimum 1-Year Follow-up

Background: Total knee arthroplasty (TKA) demonstrates excellent durability using jig-based manual techniques (manual TKA [mTKA]), but significant rates of dissatisfaction remain. Modifications of mTKA techniques and TKA implant designs to improve outcomes have had minimal success. Studies comparing relative outcomes of mTKA and robotic-assisted TKA (raTKA) are limited. Purpose: This study sought to compare outcomes of mTKA and raTKA in patients at a single institution. Methods: We retrospectively reviewed all primary TKAs performed by 1 surgeon from 2015 to 2017. In all, 139 consecutive mTKAs (2015–2016) and 148 consecutive raTKAs (2016–2017) were included. No cases were excluded. Patient demographics, complications, readmission rates, and clinical and patient-reported outcomes were compared at a minimum of 1-year follow-up. A post hoc student t test and Pearson χ2 test were used for continuous and categorical data. Results: We found that mTKA patients compared with raTKA patients required significantly longer length of stay (LOS) (1.73 vs 1.18 days, respectively), greater morphine milligram equivalents consumption (89.6 vs 65.2, respectively), and increased physical therapy (PT) visits (13.0 vs 11.0, respectively) with increased 30-day readmission rates (4.3 vs 0.7%, respectively) that approached significance. Knee Injury and Osteoarthritis Outcome Score for Joint Replacement and the University of California at Los Angeles activity score did not differ significantly comparing raTKA with mTKA patients at 1 year. There were no differences in complication rates. Conclusion: Significant early clinical benefits were noted with raTKA, including lower opioid requirements, shorter LOS, and fewer PT visits when compared with mTKA. A reduction in 30-day readmission rates was noted with raTKA that was not significant. Excellent clinical results with similar patient-reported outcomes were noted in both groups at 1-year follow-up. Further prospective investigations at longer follow-up intervals comparing these techniques are warranted.

Increased risk of periprosthetic joint infection after acute, traumatic wound dehiscence following primary total knee arthroplasty

Aims To describe the risk of periprosthetic joint infection (PJI) and reoperation in patients who have an acute, traumatic wound dehiscence following total knee arthroplasty (TKA). Methods From January 2002 to December 2018, 16,134 primary TKAs were performed at a single institution. A total of 26 patients (0.1%) had a traumatic wound dehiscence within the first 30 days. Mean age was 68 years (44 to 87), 38% (n = 10) were female, and mean BMI was 34 kg/m2 (23 to 48). Median time to dehiscence was 13 days (interquartile range (IQR) 4 to 15). The dehiscence resulted from a fall in 22 patients and sudden flexion after staple removal in four. The arthrotomy was also disrupted in 58% (n = 15), including a complete extensor mechanism disruption in four knees. An irrigation and debridement with component retention (IDCR) was performed within 48 hours in 19 of 26 knees and two-thirds were discharged on antibiotic therapy. The mean follow-up was six years (2 to 15). The association of wound dehiscence and the risk of developing a PJI was analyzed. Results Patients who sustained a traumatic wound dehiscence had a 6.5-fold increase in the risk of PJI (95% confidence interval (CI) 1.6 to 26.2; p = 0.008). With the small number of PJIs, no variables were found to be significant risk factors. However, there were no PJIs in any of the patients who were treated with IDCR and a course of antibiotics. Three knees required reoperation including one two-stage exchange for PJI, one repeat IDCR for PJI, and one revision for aseptic loosening of the tibial component. Conclusion Despite having a traumatic wound dehiscence, the risk of PJI was low, but much higher than experienced in all other TKAs during the same period. We recommend urgent IDCR and a course of postoperative antibiotics to decrease the risk of PJI. A traumatic wound dehiscence increases risk of PJI by 6.5-fold. Cite this article: Bone Joint J 2021;103-B(6 Supple A):191–195.

The effectiveness of laboratory tests to predict early postoperative periprosthetic infection after total knee arthroplasty

Aims It remains difficult to diagnose early postoperative periprosthetic joint infection (PJI) following total knee arthroplasty (TKA). We aimed to validate the optimal cutoff values of ESR, CRP, and synovial fluid analysis for detecting early postoperative PJI in a large series of primary TKAs. Methods We retrospectively identified 27,066 primary TKAs performed between 2000 and 2019. Within 12 weeks, 169 patients (170 TKAs) had an aspiration. The patients were divided into two groups: those evaluated ≤ six weeks, or between six and 12 weeks postoperatively. The 2011 Musculoskeletal Infection Society (MSIS) criteria for PJI diagnosis in 22 TKAs. The mean follow-up was five years (two months to 17 years). The results were compared using medians and Mann-Whitney U tests and thresholds were analyzed using receiver operator characteristic curves. Results Within six weeks, the median CRP (101 mg/l vs 35 mg/l; p = 0.011), synovial WBCs (58,295 cells/μl vs 2,121 cells/μl; p ≤ 0.001), percentage of synovial neutrophils (91% vs 71% (p < 0.001), and absolute synovial neutrophil count (ANC) (50,748 cells/μl vs 1,386 cells/μl (p < 0.001) were significantly higher in infected TKAs. Between six and 12 weeks, the median CRP (85 mg/l vs 5 mg/l (p < 0.001)), ESR (33 mm/hr vs 14 mm/hr (p = 0.015)), synovial WBCs (62,247 cells/μl vs 620 cells/μl (p < 0.001)), percentage of synovial neutrophils (93% vs 54% (p < 0.001)), and ANC (55,911 cells/μl vs 326 cells/μl (p < 0.001)) were also significantly higher in infected TKAs. Optimal thresholds at ≤ six weeks were: CRP ≥ 82 mg/l (sensitivity 70%, specificity 77%), synovial WBCs ≥ 8,676 cells/μl (83%, 90%), percentage of synovial neutrophils ≥ 88% (67%, 78%), and ANC ≥ 8,346 cells/μl (83%, 91%). Between six and 12 weeks, thresholds were: CRP ≥ 34 mg/l (90%, 93%), synovial WBCs ≥ 1,983 cells/μl (80%, 85%), percentage of synovial neutrophils ≥ 76% (80%, 81%), and ANC ≥ 1,684 cells/μl (80%, 87%). Conclusion Early PJI after TKA should be suspected within six weeks if the CRP is ≥ 82 mg/l, synovial WBCs are ≥ 8,676 cells/μl, the percentage of synovial neutrophils is ≥ 88%, and/or the ANC is ≥ 8,346 cells/μl. Between six and 12 weeks, thresholds include a CRP of ≥ 34 mg/l, synovial WBC of ≥ 1,983 cells/μl, a percentage of synovial neutrophils of ≥ 76%, and/or an ANC of ≥ 1,684 cells/μl. Cite this article: Bone Joint J 2021;103-B(6 Supple A):177–184.

3D-printed titanium metaphyseal cones in revision total knee arthroplasty with cemented and cementless stems

Aims Porous metaphyseal cones can be used for fixation in revision total knee arthroplasty (rTKA) and complex TKAs. This metaphyseal fixation has led to some surgeons using shorter cemented stems instead of diaphyseal engaging cementless stems with a potential benefit of ease of obtaining proper alignment without being beholden to the diaphysis. The purpose of this study was to evaluate short term clinical and radiographic outcomes of a series of TKA cases performed using 3D-printed metaphyseal cones. Methods A retrospective review of 86 rTKAs and nine complex primary TKAs, with an average age of 63.2 years (SD 8.2) and BMI of 34.0 kg/m2 (SD 8.7), in which metaphyseal cones were used for both femoral and tibial fixation were compared for their knee alignment based on the type of stem used. Overall, 22 knees had cementless stems on both sides, 52 had cemented stems on both sides, and 15 had mixed stems. Postoperative long-standing radiographs were evaluated for coronal and sagittal plane alignment. Adjusted logistic regression models were run to assess malalignment hip-knee-ankle (HKA) alignment beyond ± 3° and sagittal alignment of the tibial and femoral components ± 3° by stem type. Results No patients had a revision of a cone due to aseptic loosening; however, two had revision surgery due to infection. In all, 26 (27%) patients had HKA malalignment; nine (9.5%) patients had sagittal plane malalignment, five (5.6%) of the tibia, and four (10.8%) of the femur. After adjusting for age, sex, and BMI, there was a significantly increased risk for malalignment when a cone was used and both the femur and tibia had cementless compared to cemented stems (odds ratio 3.19, 95% confidence interval 1.01 to 10.05). Conclusion Porous 3D-printed cones provide excellent metaphyseal fixation. However, these central cones make the use of offset couplers difficult and may generate malalignment with cementless stems. We found 3.19-times higher odds of malalignment in our TKAs performed with metaphyseal cones and both femoral and tibial cementless stems. Cite this article: Bone Joint J 2021;103-B(6 Supple A):150–157.