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Background: Studies comparing the outcomes of bariatric surgery followed by total knee arthroplasty (TKA) versus TKA alone in obese patients have disparate results. This systematic review and meta-analysis sought to compare TKA with and without prior bariatric surgery in obese patients., Methods: MEDLINE, PubMed, and Embase were searched from inception to April 9, 2023. There were twelve included studies that yielded 2,876,547 patients, of whom 62,818 and 2,813,729 underwent TKA with and without prior bariatric surgery, respectively. Primary outcomes were medical complications (ie, urinary tract infection, pneumonia, renal failure, respiratory failure, venous thromboembolism [VTE], arrhythmia, myocardial infarction, and stroke); surgical complications (ie, wound complications [eg, infection, hematoma, dehiscence, delayed wound healing, and seroma], periprosthetic joint infection, mechanical complications, periprosthetic fracture, knee stiffness, and failed hardware); revision, and mortality. Secondary outcomes were blood transfusion, length of stay (day), and readmission., Results: The odds ratios (OR) of 90-day VTE (OR = 0.75 [0.66, 0.85], P < .00001), 90-day stroke (OR = 0.58 [0.41, 0.81], P = .002), and 1-year periprosthetic fracture (OR = 0.74 [0.55, 0.99], P = .04) were lower in those who underwent bariatric surgery before TKA. Although the mean difference in hospital stays (-0.19 days [-0.23, -0.15], P < .00001) was statistically less in those who underwent bariatric surgery before TKA, it was not clinically relevant. The other outcomes were similar between the groups., Conclusions: Bariatric surgery before TKA is beneficial in terms of a lower risk of VTE, stroke, and periprosthetic fracture. This analysis suggests surgeons consider discussing bariatric surgery before TKA in obese patients, especially those who are at risk of VTE and stroke., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Over 25% of patients with rheumatoid arthritis (RA) are expected to undergo a joint replacement during their lifetime. Current practice guidelines recommend withholding biologic therapy 1 week prior to total hip arthroplasty, given its immunosuppressive effects. Most patients are on a regimen including biologic and nonbiologic therapy; however, the individual influences of these therapies are not well understood in the setting of total knee arthroplasty (TKA). Therefore, we sought to compare biologic, nonbiologic, and recipients of both types of therapy in patients with RA undergoing TKA. We specifically assessed (1) medical complications at 90 days; (2) surgical complications up to 1 year; and (3) independent risk factors for prosthetic joint infections (PJIs).A retrospective review was conducted using a national, all-payer database for patients undergoing primary TKA from January 2010 to April 2020 ( n  = 1.97 million). Patients diagnosed with RA were then separated into at least 1-year users of biologic ( n  = 3,092), nonbiologic (28,299), or dual ( n  = 10,949) therapy. Bivariate analyses were utilized to assess for 90-day medical and up to 1-year surgical outcomes. Additionally, multivariate regression models were utilized to assess for independent risk factors.The incidence and odds ratio for medical/surgical outcomes were equivocal among the biologic, nonbiologic, and recipients receiving both types of therapy ( p  > 0.061). No differences were observed between the type of therapy as additional risk factors for infection ( p  > 0.505). However, glucocorticoids at 90 days and alcohol abuse, diabetes mellitus, obesity, as well as tobacco use were identified as additional risk factors for PJI( p  < 0.036).No appreciable differences in medical or surgical outcomes were associated with the independent use of biologic, nonbiologic, or recipients of both types of therapy in patients with RA. Additionally, alcohol abuse, diabetes mellitus, glucocorticoids, obesity, and tobacco use conferred an increased risk of PJI. These results can serve as an adjunct to current practice guidelines., Competing Interests: None declared., (Thieme. All rights reserved.)

Background: Racial and ethnic disparities have been suggested to be associated with poor outcomes after total knee arthroplasty (TKA). While socioeconomic disadvantage has been studied, analyses of race as the primary variable are lacking. Therefore, we examined the potential differences between Black and White TKA recipients. Specifically, we assessed 30-day and 90-day, as well as 1 year: (1) emergency department visits and readmissions; (2) total complications; (3) as well as risk factors for total complications., Methods: A consecutive series of 1,641 primary TKAs from January 2015 to December 2021 at a tertiary health care system were reviewed. Patients were stratified according to race, Black (n = 1,003) and White (n = 638). Outcomes of interest were analyzed using bivariate Chi-square and multivariate regressions. Demographic variables such as sex, American Society of Anesthesiologists classification, diabetes, congestive heart failure, chronic pulmonary disease, and socioeconomic status based on Area Deprivation Index were controlled for across all patients., Results: The unadjusted analyses found that Black patients had an increased likelihood of 30-day emergency department visits and readmissions (P < .001). However, in the adjusted analyses, Black race was demonstrated to be a risk factor for increased total complications at all-time points (P ≤ .0279). Area Deprivation Index was not a risk for cumulative complications at these time points (P ≥ .2455)., Conclusion: Black patients undergoing TKA may be at increased risk for complications with more risk factors including higher body mass index, tobacco use, substance abuse, chronic obstructive pulmonary disease, congestive heart failure, hypertension, chronic kidney disease, and diabetes and were thus, "sicker" initially than the White cohort. Surgeons are often treating these patients at the later stages of their diseases when risk factors are less modifiable, which necessitates a shift to early, preventable public health measures. While higher socioeconomic disadvantage has been associated with higher rates of complications, the results of this study suggest that race may play a greater role than previously thought., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Background: Few studies investigate the influence of inflammatory bowel disease (IBD) on complications following total knee arthroplasty (TKA). Therefore, we compared complications and readmissions frequencies after TKA in patients with Crohn's disease (CD) and ulcerative colitis (UC) to patients without IBD., Methods: A large administrative claims database was used to identify patients who underwent primary TKAs from 2010 to 2019 and had a diagnosis of IBD before TKA. Patients were stratified into two groups: those with CD (n = 8,369) and those with UC (n = 11,347). These patients were compared a control of 1.3 million patients without an IBD diagnosis. Chi-square and unadjusted odds ratios (OR) with 95% confidence intervals (CI) were used to compare complication frequencies. Multivariable logistic regression was used to evaluate independent risk factors for 90-day complications., Results: Compared to patients without IBD, patients with IBD were associated with higher unadjusted 90-day odds for Clostridium difficile infection (CDI) (CD: OR 2.81 [95% CI 2.17 to 3.63]; p < 0.001; UC: OR 3.01 [95% CI 2.43 to 3.72]; p < 0.001) and two-year periprosthetic joint infection (CD: OR 1.34 [95% CI 1.18 to 1.52]; p < 0.001; UC: OR 1.26 [95% CI 1.13 to 1.41]; p < 0.001). After controlling for risk factors like obesity, tobacco use, and diabetes, both types of IBD were associated with higher 90-day odds for CDI and PJI (p < 0.001 for all)., Conclusion: IBD is associated with higher 90-day postoperative CDI and PJI compared with patients without IBD. Providers should consider discussing these risks with patients who have a diagnosis of IBD., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: RED receives research support from member; Biocomposites, Inc.; CyMedica Orthopedics; DePuy Synthes Product, Inc.; Flexion Therapeutics; Microport Orthopedics, Inc.; Orthofix, Inc.;Patient-Centered Outcomes Research Institute (PCORI); Smith & Nephew; Stryker; Tissue Gene; and United Orthopedic Corporation; and is a board member of the Baltimore City Medical Society All other authors have nothing to disclose., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Arthrofibrosis following total knee arthroplasty (TKA) is a debilitating condition typically diagnosed based on clinical findings. To gain insight into the histopathologic immune cell microenvironment of arthrofibrosis, we assessed the extent of tissue fibrosis and quantified immune cell populations in specific tissue regions of the posterior capsule. We investigated specimens from three prospectively-collected, matched cohorts, grouped as patients receiving a primary TKA for osteoarthritis, revision TKA for arthrofibrosis, and revision TKA for non-arthrofibrotic, non-infectious reasons. Specimens were evaluated using hematoxylin and eosin staining, picrosirius red staining, immunofluorescence, and immunohistochemistry with Aperio®-based digital image analysis. Increased collagen deposition and increased number of α-SMA/ACTA2 expressing myofibroblasts were present in the arthrofibrosis group compared to the two non-arthrofibrotic groups. CD163 + macrophages were the most abundant immune cell type in any capsular sample with specific enrichment in the synovial tissue. CD163 + macrophages were significantly decreased in the fibrotic tissue region of arthrofibrosis patients compared to the patients with primary TKA, and significantly increased in adipose tissue region of arthrofibrotic specimens compared to non-arthrofibrotic specimens. Synovial CD117 + mast cells were significantly decreased in arthrofibrotic adipose tissue. Together, these findings inform diagnostic and targeted therapeutic strategies by providing insight into the underlying pathogenetic mechanisms of arthrofibrosis., (© 2022. The Author(s).)

Poor metaphyseal fixation secondary to bone loss in revision total knee arthroplasty (TKA) continues to be challenging. One technique to increase implant stability is the use of novel three-dimensional (3D) printed titanium metaphyseal cones with adjunctive stems for added fixation. However, the survival of these novel constructs is poorly understood. Therefore, we sought to examine 3D-printed titanium metaphyseal cone components in revision TKA for aseptic as well as septic reasons and aimed to evaluate: (1) revision-free survivorships; (2) patient-reported outcomes measures (PROMs); (3) postoperative medical complications; and (4) radiographic outcomes. A consecutive series of 62 patients who underwent revision TKA with use of a titanium metaphyseal cone at a single institution between September 1, 2015 and May 31, 2021 were examined. The patients had a minimum follow-up period of 2 years (mean, 40 months, range, 24-72 months). PROMS included Knee Injury and Osteoarthritis Outcome Score Joint Replacement (KOOS-JR) scores at baseline and last clinical follow-up. Overall, when excluding infections, the combined implant survivorship was 96% (52 out of 54), while it was 95% (35 out of 57) for aseptic revisions and 100% (17 out of 17) for septic revisions. Reasons for revisions within the aseptic revision cohort included loosening (5%) as well as periprosthetic joint infections (PJIs) (7.5%). All failures following an index septic revision were due to PJI. Mean KOOS scores at baseline as well as at final follow-up was 43 points (range, 16-80) and 70 points (range, 34-100), respectively. None of the patients had medical complications. Other than the loosening reported (only femoral component), of the surviving patients no patients had evidence of progressive radiolucencies. The use of titanium cones in revision TKA provides good revision-free survivorship at 2 years. Further research is warranted on the longer-term survivorship of 3D-printed titanium cones. The current study has found that 3D-printed titanium cones can be incorporated as part of the revision knee surgeon's armamentarium., Competing Interests: None declared., (Thieme. All rights reserved.)

Mechanical knee symptoms secondary to knee osteoarthritis (OA) may warrant knee arthroscopy (KA). Degenerative changes may progress and require a subsequent total knee arthroplasty (TKA). Recent studies have evaluated the timing of KA prior to TKA, associated a narrow interval with increased post-TKA complications. However, an updated analysis is required. We compared surgical outcomes in recipients of KA prior to TKA as stratified by four, time-dependent cohorts (< 12, 12 to 16, 16 to 20, and 20 to 24 weeks prior to TKA). We specifically compared: 90-day (1) manipulations under anesthesia (MUAs); (2) septic revisions at 90 days, 1 year, and 2 years; as well as (3) how various independent risk factors influenced the manipulations or revisions. We queried a national database for patients undergoing TKA. Patients who underwent KA with the following intervals: < 12 ( n  = 1,023), 12 to 16 ( n  = 816), 16 to 20 ( n  = 1,957), and 20 to 24 weeks (1,727) prior to TKA were compared with those patients who did not have a history of KA ( n  = 5,000). Bivariate analyses were utilized to assess 90 days through 2 years surgical outcomes. Afterwards, multivariate regression models were utilized to assess for independent risk factors. The unadjusted analyses showed an increase in MUA through 2 years among all the KA recipients ( p  < 0.001). Septic revisions and surgical site infections at all time points were not associated with any of the four arthroscopy time intervals ( p  > 0.476). The adjusted analyses showed an increased risk for 90-day MUA among all TKA cohorts ( p  < 0.001). Risk for septic revisions did not reach significance. Delaying TKA by 24 weeks in KA recipients was not associated with a decreased risk in septic revisions. However, there was an apparent risk of MUA at 90 days for all KA cohorts suggesting that waiting after KA before TKA makes no difference in MUA rates. These results update existing literature, may serve as an adjunct to current practice guidelines, and can contribute to shared decision making in the preoperative setting., Competing Interests: None declared., (Thieme. All rights reserved.)

Background: No consensus exists regarding the appropriate timing of bariatric surgery (BS) or the complication profiles between Roux-en-Y Gastric Bypass (RYGB) and sleeve gastrectomy (SG) prior to total knee arthroplasty (TKA). We sought to compare 90-day medical and up to two-year surgical complications and revisions among (1) BS performed 6 months and 1 year prior to TKA; (2) between BS types (RYGB and SG) prior to TKA; and (3) with comparison to 2 non-BS cohorts of morbidly and nonmorbidly obese patients., Methods: We queried a national database to identify patients undergoing BS (RYGB and SG) prior to TKA from 2010 to 2020. Timing (six-month and one-year intervals) and type of BS (RYGB and SG) were identified. Cohorts without prior BS served as comparators: BMI, kg/m 2 > 40 and 20-35. Ninety-day to two-year medical/surgical complications and revisions were assessed. Multivariate regression analyses examined the risk factors for prosthetic joint infections (PJIs) and revisions., Results: The timing of BS (6 months and 1 year) had similar incidences of medical/surgical complications and revisions, with both lower than the BMI > 40 cohort (P < .001). Differences between types of BS were also lower than the BMI > 40 cohort (P < .001). The BMI 20-35 had lower complications and revisions among all cohorts. No differences were observed between BS timing or type as risk-factors for PJIs and revisions., Conclusion: Timing (6 months or 1 year prior to TKA) and type of BS shared similar complication profiles, lower than BMI > 40 and higher than BMI 20-35. These findings support a surgeon's decision to proceed with TKA at six months post-BS if indicated., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Introduction: Current diagnostic criteria for arthrofibrosis are limited. Since many patients will be aspirated during their clinical course, synovial fluid analysis may supplement current diagnostic criteria for arthrofibrosis. The goal of this study was to determine a unique synovial fluid and inflammatory marker profile for diagnosing arthrofibrosis., Hypothesis: Patients with arthrofibrosis following total knee arthroplasty will have a unique synovial fluid aspirate profile compared to control patients to aid in diagnosis., Materials and Methods: Between 2013 and 2017, 32 patients (32 total knee arthroplasties [TKAs]) underwent revision TKAs for arthrofibrosis. Fourteen patients had pre-revision aspirations. They were 2:1 matched based on age, sex, body mass index (BMI), and year of revision to 28 patients who underwent aseptic revision TKAs for reasons other than arthrofibrosis (control group). Mean age at revision was 66years, with 64% males., Results: In TKAs revised for arthrofibrosis, mean total cell count was 828cells/uL. These aspirates contained a mean distribution of 46% macrophages (range: 4-76%), 31% lymphocytes (range: 11-68%), 21% neutrophils (range: 0-75%), 1% other cells (mainly synovial cells; range: 0-11%), and 1% eosinophils (range: 0-7%). There was no significant difference in mean total cell count (p=0.8) or mean distribution of macrophages (p=0.6), lymphocytes (p=0.1), neutrophils (p=0.2), eosinophils (p>0.9), or serum inflammatory markers (p>0.7) when compared to controls. All aspirations were culture negative for infection., Discussion: The profile of arthrofibrotic synovial fluid aspirates and serum inflammatory marker values were similar to patients revised for non-arthrofibrotic aseptic etiologies. This suggests synovial fluid and serum inflammatory markers in non-infected knees with arthrofibrosis should expect to have characteristics similar to synovial fluid and inflammatory marker profiles in other aseptic diagnoses., Level of Evidence: III; retrospective case-control study., (Copyright © 2021 Elsevier Masson SAS. All rights reserved.)

Background: Total knee arthroplasties (TKAs) with cementless fixation have been studied in multiple series with varying success. The aim of this study was to prepare a systematic review of the literature to evaluate clinical outcomes and revtpdelision rates of patients undergoing contemporary cementless TKA., Methods: A search of PubMed and MEDLINE was conducted for English-language articles published between 2005 and 2018 to identify studies examining survivorship and clinical outcomes of cementless TKAs. Studies that reported clinical and/or radiographic outcomes were included. Data collected included the number of TKAs, implant utilized, primary diagnosis, mean age and follow-up, implant survivorship, complications, revisions, and clinical outcome scores. All hybrid constructs and revision TKAs were excluded. Poisson regression analysis was used to determine the revision incidence rates per 1,000 person-years., Results: Forty-three studies with 10,447 TKAs met inclusion criteria, of which 8,187 were primary cementless TKAs. The mean follow-up was 7 years. The revision incidence per 1,000 person-years was 4.8 for all cementless designs. The complication rate for all cementless TKAs was 6%, with deep venous thrombosis being the most common complication. The mean postoperative Knee Society Score and Functional Score were 92 and 83, respectively., Conclusions: While newer-generation cementless designs have shown improved survivorship and clinical outcomes compared with earlier-generation cementless designs, the literature for cementless designs remains limited when compared with cemented designs. Further studies are needed to determine if cementless TKA can achieve the same benefits that have been realized with cementless total hip arthroplasty., Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Background: Varus-valgus constrained (VVC) implants are used for compromised ligamentous stability in revision total knee arthroplasties (TKAs). Mobile-bearing VVC implants may reduce rotational forces; yet, limited clinical data exist. The purpose of this study is to report mid-term risk of re-revision, complications, and clinical outcomes with a mobile-bearing VVC implant., Methods: Three hundred thirty-seven patients (367 TKAs) who underwent revision TKA with a mobile-bearing VVC implant between 1999 and 2013 at a single institution were reviewed. Mean age at revision was 67 years. Mean follow-up was 4 years. The main indications for revision were aseptic loosening in 158 cases (43%), reimplantation after 2-stage exchange arthroplasty in 120 (33%), instability in 61 (17%), and other in 28 (7%). Clinical outcomes were assessed by Knee Society Scores, and survivorship was analyzed with death as the competing risk., Results: The 5-year cumulative incidences of any re-revision or re-revision for aseptic loosening were 9% and 3%, respectively. Twenty-six knees (7%) were re-revised: 15 for infection, 6 for aseptic loosening, and 5 for other causes. There were 17 cases of irrigation and debridement, 10 cases of manipulations under anesthesia, and 9 cases of periprosthetic fractures. There were no bearing "spin-outs." The mean Knee Society Scores improved from 45 preoperatively to 77 at most recent follow-up (P < .001)., Conclusion: The functional improvement and 5-year cumulative incidence of revision of a mobile-bearing VVC implant demonstrated acceptable outcomes with no unique complications related to the mobile-bearing construct. Additional follow-up will be needed to determine long-term implant survivorship., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: Quadriceps snips (QSs) are commonly used to gain enhanced exposure during revision total knee arthroplasties (TKAs). The goals of this study were to evaluate the longer-term clinical outcomes and complications in a contemporary cohort of patients treated with QS and to compare them to a matched cohort treated with standard exposure during revision TKAs., Methods: We retrospectively identified 3107 revision TKAs performed at our institution between 2002 and 2012. QS was performed in 321 of these knees. Each QS revision TKA was 1:1 matched to a control (standard exposure) based on age, gender, body mass index, surgery date, and reason for revision. Clinical outcomes studied included Knee Society Score, range of motion, and extensor lag. Other outcomes assessed were complications (especially extensor mechanism disruption) and survivorship. Mean follow-up was 5 years., Results: The mean Knee Society Score improvement was not significantly different between groups (P = .9). At latest follow-up, the mean range of motion was 93° in the QS group and was slightly higher at 100° in the control group (P = .002). Postoperative extensor lag of 10 degrees or more was present in 21 (6.7%) QS knees versus 19 (6.8%) control knees (P = .95). Complication rates were similar in both groups with extensor mechanism disruption occurring in 3 in the QS group (0.7% at 10 years) versus 4 in the control group (0.8% at 10 years; P = .91). Kaplan-Meier survivorships free of revision for aseptic loosening, free of any revision, and free of any reoperation were similar at 10 years (85%, 71%, and 61%, respectively, in the QS group vs 89%, 70% and 60%, respectively, in the control group)., Conclusion: This matched cohort study is the largest to report the results of QS and also the largest to report results compared with patients treated with standard exposure. Building on the results of smaller historical series, this study demonstrates QS was a facile technique in complex revision TKAs allowing for safe exposure with few complications., Level of Evidence: III (case-control study)., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: Stiffness is a common reason for suboptimal clinical outcomes after primary total knee arthroplasty (pTKA). There is a lack of consensus regarding its definition, which is often conflated with its histopathologic subcategory-i.e., arthrofibrosis. There is value in refining the definition of acquired idiopathic stiffness in an effort to select for patients with arthrofibrosis. We conducted a systematic review and meta-analysis to establish a consensus definition of acquired idiopathic stiffness, determine its prevalence after pTKA, and identify potential risk factors for its development., Methods: MEDLINE, Embase, Cochrane Controlled Register of Trials (CENTRAL), and Scopus databases were searched from 2002 to 2017. Studies that included patients with stiffness after pTKA were screened with strict inclusion and exclusion criteria to isolate the subset of patients with acquired idiopathic stiffness unrelated to known extrinsic or surgical causes. Three authors independently assessed study eligibility and risk of bias and collected data. Outcomes of interest were then analyzed according to age, sex, and body mass index (BMI)., Results: In the 35 included studies (48,873 pTKAs), the mean patient age was 66 years. In 63% of the studies, stiffness was defined as a range of motion of <90° or a flexion contracture of >5° at 6 to 12 weeks postoperatively. The prevalence of acquired idiopathic stiffness after pTKA was 4%, and this did not differ according to age (4%, I = 95%, among patients <65 years old and 5%, I = 96%, among those ≥65 years old; p = 0.238). The prevalence of acquired idiopathic stiffness was significantly lower in males (1%, I = 85%) than females (3%, I = 95%) (p < 0.0001) as well as in patients with a BMI of <30 kg/m (2%, I = 94%) compared with those with a BMI of ≥30 kg/m (5%, I = 97%) (p = 0.027)., Conclusions: Contemporary literature supports the following definition for acquired idiopathic stiffness: a range of motion of <90° persisting for >12 weeks after pTKA in patients in the absence of complicating factors including preexisting stiffness. The mean prevalence of acquired idiopathic stiffness after pTKA was 4%; females and obese patients were at increased risk., Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Background: Periprosthetic joint infection (PJI) of the knee with concurrent disruption of the extensor mechanism is a devastating complication. Historically, knees with such complications have been salvaged with use of an arthrodesis or amputation. The purpose of this study was to assess the survival and functional outcomes of a 2-stage exchange arthroplasty combined with knitted monofilament polypropylene (Marlex; C.R. Bard) mesh reconstruction of the extensor mechanism., Methods: From 2000 to 2015, 16 patients underwent a 2-stage exchange arthroplasty and Marlex-mesh reconstruction for PJI with an extensor mechanism disruption. The study included 9 male patients and 7 female patients with a mean age at the time of reimplantation and mesh reconstruction of 64 years. The mean follow-up was 4 years. PJI was diagnosed on the basis of the Musculoskeletal Infection Society criteria. Clinical outcomes, including survivorship, Knee Society Score (KSS) results, and complications, were assessed., Results: Of 16 reconstructions, 13 were in place at the time of the latest follow-up. At 2 years, survivorship free of mesh failure was 86%, survivorship free of PJI was 87%, and survivorship free of PJI or mesh failure was 75%. The mean KSS improved from 48 prior to resection to 74 after mesh reconstruction and reimplantation. The mean extensor lag improved from 31° prior to resection to 3° after mesh reconstruction. Two patients required mesh revision, 1 patient required an above-the-knee amputation for complex wound complications related to reinfection, 1 patient developed a reinfection requiring irrigation and debridement, and 1 patient developed a superficial infection that required debridement., Conclusions: Two-stage exchange arthroplasty combined with Marlex-mesh reconstruction of the extensor mechanism is a viable alternative to knee arthrodesis or amputation. At 2 years, 75% of mesh reconstructions were in place and without evidence of PJI. Moreover, the functional outcomes were improved, with a negligible extensor lag., Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Total knee arthroplasty (TKA) is a durable and reliable procedure to alleviate pain and improve joint function. However, failures related to flexion instability sometimes occur. The goal of this study was to define biological differences between tissues from patients with and without flexion instability of the knee after TKA. Human knee joint capsule tissues were collected at the time of primary or revision TKAs and analyzed by RT-qPCR and RNA-seq, revealing novel patterns of differential gene expression between the two groups. Interestingly, genes related to collagen production and extracellular matrix (ECM) degradation were higher in samples from patients with flexion instability. Partitioned clustering analyses further emphasized differential gene expression patterns between sample types that may help guide clinical interpretations of this complication. Future efforts to disentangle the effects of physical and biological (e.g., transcriptomic modifications) risk factors will aid in further characterizing and avoiding flexion instability after TKA., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Background: Disruption of the extensor mechanism after total knee arthroplasty (TKA) is debilitating, and the reported results of numerous reconstructive options have varied. We previously reported the early results of 13 patients who underwent reconstruction of the extensor mechanism with use of Marlex mesh. The purpose of the current study was to assess results in a larger cohort of patients, with an emphasis on the survivorship of the mesh, clinical results, and complications., Methods: During the period of 2000 to 2015 at a single tertiary care academic institution, 77 patients (77 TKAs) underwent reconstruction with use of Marlex mesh for an extensor mechanism disruption (27 quadriceps tendon disruptions, 40 patellar tendon disruptions, and 10 patellar fractures). The mean patient age at the time of reconstruction was 65 years; 70% of the patients were female. The mean body mass index was 35 kg/m. The mean follow-up was 4 years. Eighteen (23%) of the patients underwent mesh reconstruction with the primary TKA in place, and 59 (77%) had mesh reconstruction at the time of revision TKA. The mean time between disruption and reconstruction was 7 months. Twenty (26%) of the patients had previously undergone attempted extensor mechanism reconstruction at outside institutions., Results: Sixty-five of the 77 mesh reconstructions were in place at the time of the latest follow-up. Twelve patients experienced a failure that required mesh revision: 5 for patellar tendon rupture, 5 for quadriceps tendon rupture, and 2 for symptomatic lengthening. Four additional patients with mesh failure were treated nonoperatively with bracing. The 2-year survivorship free of mesh revision was 86% for patients with no prior reconstruction and 95% for patients with previous reconstructions of the extensor mechanism that did not involve Marlex mesh. Knee Society Score (KSS) results significantly improved following reconstruction (p < 0.001). Extensor lag improved by a mean of 26°, with mean postoperative extensor lag measuring 9° (p < 0.001)., Conclusions: Reconstruction of the extensor mechanism with use of Marlex mesh is a viable option in patients with catastrophic disruption after TKA. At the time of the latest follow-up, 84% of the mesh reconstructions were in place and the functional outcomes were excellent, with mean improvement in extensor lag of 26°. Extended follow-up is required, but the results of this large series with a mean follow-up of 4 years are encouraging., Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.