BACKGROUND: The purpose of this study was to determine implant survivorship and functional outcomes for revision total knee arthroplasty (rTKA) with contemporary rotating-hinge knee implants.
METHODS: A retrospective review identified 115 rTKAs using contemporary rotating-hinge implants from 2014 to 2018 for the treatment of instability (34, 30%), reimplantation after periprosthetic joint infection (PJI) (33, 29%), aseptic loosening (25, 22%), arthrofibrosis (14, 12%), periprosthetic fracture (4, 3%), osteolysis (4, 3%), and femoral component fracture (1, 1%). There were 70 women (61%), and the mean age was 67 years (range, 27 to 94). The mean follow-up was 3 years (range, 2 to 6). Kaplan-Meier analysis and Cox proportional hazard models estimated survivorship.
RESULTS: The re-revision rate was 20% (23 of 115) at an average of 18 months postoperatively. Re-revision indications included PJI (n = 14), aseptic loosening (n = 4), arthrofibrosis (n = 2), instability/malalignment (n = 1), femoral stem fracture (n = 1), and hinge mechanism disruption (n = 1). At 2 and 5 years, survivorship free from all-cause re-revision was 86% and 64%, and survivorship free from re-revision for aseptic loosening was 100% and 87%, respectively. Use of a rotating-hinge implant in reimplantation after PJI was a risk factor for subsequent re-revision (hazard ratio = 2.4, P = 0.046). On a radiographic review of unrevised rotating-hinges, there were major radiolucent lines around 2 femoral and 5 tibial components. The mean Knee Osteoarthritis Outcomes Score for Joint Replacement (KOOS JR) increased from 43 preoperatively to 60 at 1 year (P < 0.001).
CONCLUSIONS: In patients treated with a rotating-hinge implant for rTKA, there were relatively poor 2-year (86%) and 5-year (64%) survivorship free from all-cause re-revision, most commonly due to PJI. Mid-term survivorship free from re-revision for aseptic loosening was modest (87%). There should be a goal to mitigate complications in complex rTKAs with rotating-hinge implants, namely PJI.

BACKGROUND: The increasing prevalence of primary hip arthroplasty has led to a parallel rise in revision cases. Femoral revision often entails compromised bone integrity, requiring consideration of various solutions for optimal reconstructive options. Despite technological advancements, there is limited evidence on the clinical outcomes of the latest modular revision stems. This study aimed to evaluate the clinical outcomes and survival rates of next generation uncemented modular revision stem in patients undergoing hip revision surgery.
METHODS: This retrospective single-center study assessed the survival and failure causes of a specific uncemented modular stem in 48 patients undergoing hip revision surgery between 2012 and 2022. Data included preoperative parameters, surgical details, and postoperative outcomes measured through clinical and radiographic assessments. Forty-eight patients (25 males, 23 females; mean age 72 years) were included, with a mean Charlson Comorbidity Index of 5. Preoperative diagnoses varied, with periprosthetic joint infection (PJI) being the most common (45.8%), followed by periprosthetic fractures (27.1%). Partial revisions occurred in 60.4%, total revisions in 39.6%. According to Paprosky classification of femoral bone loss, type II and III were the most represented, respectively 35.4% and 50%.
RESULTS: At a mean follow-up of 4.6 years, stem survival was 92.5%. Complications (20%) included dislocation, PJI, fracture, and loosening; the overall reoperation rate was 12.5%. The SF-12 physical score was 43.6, while the mental score was 51.1. The HOOS score was 71.8, and the HHS score was 71.4. Radiographic analysis identified nonprogressive osteolysis in 15.1% of patients.
CONCLUSIONS: This study on this uncemented modular revision stem demonstrated favorable outcomes in an elder fragile population with moderate to severe femoral bone loss. The implant\'s modularity provides versatility in addressing various defects, without any implant breakage observed during the study period. Literature comparison highlighted similar outcomes despite sample size differences. The promising results warrant continued investigation into the long-term survivorship of this modular stem system.

OBJECTIVE: Establishing the diagnosis of loosening in total or unicondylar knee arthroplasty remains a challenge with different clinical and radiological signs evaluated in study designs with high risk of bias, where few or incomplete criteria are formulated for establishing the diagnosis of implant loosening. This study aimed at evaluating the variability between different clinical and radiological criteria and establish a consensus regarding clinical and radiological criteria for the diagnosis of knee arthroplasty loosening.
METHODS: Highly specialized knee surgeons focusing on revision arthroplasty were invited to take part in an international panel for a Delphi consensus study. In the first round, the participants were asked to state their most important clinical and radiological criteria for implant loosening. In a second round, the panel\'s agreement with the collected criteria was rated on a 5-point Likert scale (1-5). High variability was defined by receiving at least one score each indicating complete disagreement and complete agreement. Consensus was established when over 70% of participants rated a criterion as \'fully agree\' (5) or \'mostly agree\' (4).
RESULTS: High variability was observed in 56% of clinical criteria and 38% of radiological criteria. A consensus was reached on one clinical (weight-bearing pain [82%]) and four radiological criteria, that is, implant migration, progressive radiolucencies, subsidence and radiolucencies >2 mm on X-ray or computed tomography (CT) (84%-100%).
CONCLUSIONS: Amongst specialized knee revision surgeons, there is high variability in clinical and radiological criteria that are seen as important contributing factors to diagnosis of knee implant loosening. A consensus was reached on weight-bearing pain as clinical criterion and on implant migration, progressive radiolucencies, subsidence and radiolucencies of more than 2 mm on X-ray or CT as radiological criteria. The variability rates observed, along with the criteria that reached consensus, offer important insights for the standardization of diagnostic protocols.
METHODS: Level V.

Improper osteotomy during total knee arthroplasty (TKA) can lead to anterior femoral notching, which increases the risk of periprosthetic fractures due to stress concentration. One potential solution is the addition of an intramedullary stem to the femoral component. However, the optimal stem length remains unclear. In this study, we aimed to determine the optimal stem length using finite element models. Finite element models of femurs were developed with unstemmed prostheses and prostheses with stem lengths of 50, 75, and 100 mm. Under squat loading conditions, the von Mises stress at the notch and stress distribution on four transversal sections of the femur were analyzed. Additionally, micromotion of the prosthesis-bone interface was evaluated to assess initial stability. The unstemmed prosthesis exhibited a von Mises stress of 191.8 MPa at the notch, which decreased to 43.1, 8.8, and 23.5 MPa for stem lengths of 50, 75, and 100 mm, respectively. The stress reduction on four selected femoral transversal sections compared with the unstemmed prosthesis was 40.0%, 84.4%, and 67.1% for stem lengths of 50, 75, and 100 mm, respectively. Micromotion analysis showed a maximum of 118.8 μm for the unstemmed prosthesis, which decreased significantly with the application of stems, particularly at the anterior flange. Intramedullary stems effectively reduced stress concentration at the femoral notch. The 50-mm stem length provided the optimal combination of reduced notch stress, minimized stress-shielding effect, and decreased micromotion at the anterior flange.

BACKGROUND: The use of a tibial stem for large deformities (> 10°) would reduce the incidence of pain. The aim of this study was to compare the effect of tibial stem on postoperative pain and aseptic loosening at the tibia in patients with a preoperative deformity > 10° in the frontal plane at 2 years follow-up.
METHODS: This was a retrospective single-center case-control study. Ninety-eight patients with deformities greater than 10° in the frontal plane and a BMI > 30 kg/m2 who had undergone posterior-stabilized (PS) total knee arthroplasty (TKA) with a tibial stem were matched using a propensity score to 98 patients who had undergone PS TKA without a tibial stem. The primary endpoint was the pain rate at 2 years. The secondary endpoints were the rate of aseptic loosening of the tibia at 2 years post-operatively.
RESULTS: A significant difference was found in the rate of postoperative pain at 2 years. It was higher in the group without tibial stem compared with the group with tibial stem (41.8% vs 17.3%, p = 0.0003). In the group without tibial stem, 24.4% of pain was mild, 61% moderate and no severe pain. In the tibial stem group, 47.1% of pain was mild, 41.2% moderate and no severe pain. A radiolucent line (RLL) was present at 2 years in 26.5% of prostheses in the without tibial stem group and in 9.2% of prostheses in the tibial stem group (p = 0.002). There was no difference between the two groups in terms of aseptic loosening.
CONCLUSIONS: The use of a tibial stem in primary TKA in patients with frontal deformities greater than 10° reduces postoperative pain and the presence of radiolucent lines.

We report a case of previously undescribed medial unicompartmental knee arthroplasty failure due to femoral component implant fracture. The patient experienced sudden pain and locking while ambulating 8 years postoperatively. Radiographs revealed catastrophic femoral component failure with a transverse break through the metal. The patient underwent revision to total knee arthroplasty. At 1-year follow-up, the patient had no pain and a range of motion of 130 degrees. Particular attention should be paid to obtaining adequate femoral component posterior flange fixation during unicompartmental knee arthroplasty. Patient education regarding maintaining a healthy weight is crucial to preventing this complication.

BACKGROUND: Obesity rates have been increasing globally, leading to a higher incidence of knee osteoarthritis and a surge in primary and revision total knee arthroplasty (TKA). The debate continues on the impact of obesity on TKA success, particularly regarding the use of stemmed tibial components in obese patients. This systematic review aimed to compare the effectiveness of stemmed tibial components versus standard keeled tibial components in obese patients undergoing TKA, hypothesizing that stemmed components would yield better clinical and radiological outcomes.
METHODS: A systematic review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement guidelines. Databases including PubMed, Embase, Scopus, and Web of Science were searched from inception to December 2023. The eligibility criteria were based on the PICO framework; Participants: Patients who have obesity undergoing TKA, Intervention: stemmed TKA, Comparator: standard keeled tibial TKA, Outcome: aseptic loosening, Patient-Reported Outcome Measures (PROMs), and overall revision. Data extraction and quality assessment were performed using the Newcastle-Ottawa Scale for cohort studies and the Cochrane risk-of-bias tool for randomized trials.
RESULTS: The search yielded 470 studies, with 10 studies (42,533 knees) meeting the inclusion criteria. These studies included three randomized clinical trials and seven retrospective cohorts. The primary outcomes measured were aseptic loosening and overall revision rates, while secondary outcomes included PROMs. Results indicated mixed findings, with some studies suggesting improved outcomes with stemmed components in cases of aseptic loosening and mechanical failure, while others showed no significant difference. The PROMs did not show a significant difference between groups post-TKA. The certainty of the evidence was graded as \"very low\" using the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) framework.
CONCLUSIONS: Current literature does not provide conclusive evidence to support the routine use of stemmed tibial components in TKA for obese patients. The decision to use stem extensions should not solely rely on the patient\'s obesity status. Further high-quality studies are needed to clarify the role of stemmed components in TKA for this patient population.

BACKGROUND: Approximately 5% of primary total knee arthroplasty patients require revision within 10 years, often due to distal component loosening. Application of a thin layer of PMMA cement as precoating on the tibial component aims to prevent aseptic loosening. This study investigates the impact of precoating and fat contamination on tibial baseplate stability.
METHODS: Two groups of NexGen® stemmed tibial implants (size 4) were studied: Option implants (N = 12) and PMMA Precoat implants (N = 12). Each implant design was divided into two subgroups, (N = 6), with one subgroup featuring bone marrow fat at the implant-cement interface and the other without contamination. In a mechanical testing machine, the implants underwent uniaxial loading for 20,000 cycles, while recording vertical micromotion and migration of the tibial baseplates. Subsequently, a push-out test assessed fixation strength at the cement interfaces. Results were compared using non-parametric statistics and presented as median and min-to-max ranges.
RESULTS: Option implants exhibited higher micromotion in dry conditions compared to precoated implants (p = 0.03). Under contamination, both designs demonstrated similar micromotion values. Fixation strength did not significantly differ between designs under dry, uncontaminated conditions (p > 0.99). However, under contaminated conditions, the failure load for the non-coated Option implant was nearly half that of the uncontaminated counterparts (3517 N, 2603-4367 N vs 7531 N, 5163-9000 N; p = 0.002). Precoat implants displayed less susceptibility to fat contamination (p = 0.30).
CONCLUSIONS: NexGen® implant PMMA precoating might reduce the risk of aseptic loosening and revision surgery in case of eventual bone-marrow fat contamination.

BACKGROUND: Accurate positioning of components in total knee arthroplasty (TKA) is essential to a satisfactory outcome. Significant malrotation may lead to chronic pain, stiffness, and dysfunction. This study aims to quantify improvements in functional outcomes following revision surgery for malrotation of either one or both components in TKA versus revision for aseptic loosening.
METHODS: This was a retrospective review of TKAs that matched and compared the two-year functional outcomes of the malrotation group to a functionally similar aseptic loosening group. Functional outcomes were compared between groups using Short Form (SF-12), Western Ontario and McMaster University Osteoarthritis Index (WOMAC), and Knee Society Functional Score (KSFS). Student t-tests and chi-squared or Fisher\'s tests were used for statistical analysis.
RESULTS: Of the patients revised, 24 had malrotation and 57 had aseptic loosening. A total of 16 femoral and 17 tibial components were revised for malrotation. All 16 femoral components were internally malrotated (mean -4.8 ± 4.1 degrees; range, -0.5 to -16.6). Of the tibial components, 15 were internally malrotated, (mean -9.5 ± 6.6 degrees; range, -2.2 to -23.5) and 2 were externally malrotated (mean 4.6 ± 2.1 degrees; range, 3.1 to 6.0). All functional outcome measures significantly improved comparably within both groups preoperatively to 24 months postoperatively. At 24 months, functional outcome measures were comparable between the groups and WOMAC function scores were significantly higher in the malrotation group.
CONCLUSIONS: Revision TKA for malrotation can yield clinically and statistically significant functional improvements, similar in magnitude to those seen following revision TKA for aseptic loosening.
METHODS: Level III.

UNASSIGNED: Aseptic loosening is the most common cause for revisions after total knee arthroplasty (TKA). Despite many studies exploring various risk factors associated with aseptic loosening, findings often present inconsistencies. To address this, we conducted a thorough review of the literature to identify and analyse these risk factors in cemented TKA. Additionally, we performed a meta-analysis to reconcile the divergent conclusions observed across studies.
UNASSIGNED: We searched PubMed, Web of Science and Embase from 1996 up to 2024 and evaluated the quality of the included literature. Seventy-four studies were included to assess the association of BMI, diabetes, high physical activity (HPA), osteoporosis, rheumatoid arthritis (RA), cement material and implant design. Twenty-nine studies were used to calculate relative risk and CIs (using the random effects theory) and study heterogeneity for six different risk factors (BMI, diabetes, HPA level, cement material, polyethylene and implant design).
UNASSIGNED: Patients with diabetes are eight times more likely to experience aseptic loosening compared to those without diabetes (RR = 9.18, 95% CI: 1.80-46.77, p < 0.01). The use of tibial stem extension or highly crosslinked polyethylene can help reduce the incidence of aseptic loosening. However, we did not identify BMI, HPA, osteoporosis, RA, the use of high-viscosity cement and the utilization of mobile-bearing designs as risk factors for aseptic loosening post-cemented TKA.
UNASSIGNED: Patients with diabetes undergoing TKA should be counselled regarding their potential increased risk of aseptic loosening. The use of tibial stem extensions and HXLPE can mitigate the incidence of aseptic loosening in cemented TKA. However, given a limited number of studies were included in the meta-analysis, we believe that higher-level studies are necessary to clearly identify other risk factors.
UNASSIGNED: Level III.