Survivorship and Outcomes of Robotic Arm-Assisted Medial Unicompartmental Knee Arthroplasty at a Minimum of 5-Year Follow-Up.

PURPOSE: This study aimed to evaluate implant survivor-ship, complications, and re-operation rates following robotic arm-assisted unicompartmental knee arthroplasty (UKA) at mid-term follow-up. METHODS: Patient satisfaction, clinical outcome, and knee alignment restoration were evaluated. All patients undergo-ing robotic arm-assisted medial UKA during a 2-year period were prospectively enrolled. Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, varus-valgus deformity, and knee range of motion were studied pre- and postoperatively. Revisions and surgery-related complications were recorded. RESULTS: Eighty-five patients were included in the study (mean age: 71.2 years). The mean follow-up was 74.7 months. One conversion to total knee arthroplasty was performed due to periprosthetic fracture 4.5 years after initial surgery result-ing in a survivorship rate of 98.8%. Overall satisfaction was excellent; 97.7% of patients were satisfied or very satisfied, while none was dissatisfied or very dissatisfied. WOMAC score in total, as well as in each component, exhibited sig-nificant improvement postoperatively. Additionally, knee alignment in the coronal plane as well as flexion contracture were significantly improved following the procedure. CONCLUSIONS: The outcomes of the present cohort revealed that precise prosthesis implantation through the robotic arm-assisted system in UKA provided excellent overall satisfac-tion rates and clinical outcomes at mid-term follow-up.

Aseptic midterm survival rates between different cemented tibial stem designs in hinged total knee arthroplasty: a 6-year evaluation from the German Arthroplasty Registry.

INTRODUCTION: The rate of revision TKA and thus the use of hinged implants (HI) steadily rises. Aseptic loosening lies on the top of the failure patterns. However, no evidence exists until now based on national scale high-caseloads that analyzes the impact of cemented HI stem-design on aseptic survival rates. METHODS: Data on aseptic HI-revisions with full-cemented tibia-stems were conducted from the German Arthroplasty Registry. Cases were divided in primary HI (PHI) and HI used in revision operations (RHI). Endpoint was a new revision following either a PHI or an RHI. The impact of stem conicity (conical vs. cylindrical), diameter (≤ 13 mm vs. > 13 mm), length (≤ 90 mm vs. > 90 mm) and offset on the 6-Year-Cumulative-Aseptic-Revision-Rate (6Y-CARR) was estimated via Kaplan-Meier curve and compared between groups via Log-Rank-Tests. RESULTS: 3953 PHI and 2032 RHI fulfilled inclusion-criteria. Stem conicity had no impact on 6Y-CARR (p = 0.08 and p = 0.8). Diameter > 13 mm hat an impact on PHI (p = 0.05) with lower 6Y-CARR but not on RHI (p = 0.2). Length > 90 mm showed significantly worst 6Y-CARR in PHI (p = 0.0001) but not in RHI (p = 0.3). Offset-stems showed significantly better 6Y-CARR in PHI (p = 0.04), but not in RHI (p = 0.7). CONCLUSION: There was no significant impact of the cemented tibia-stem conicity on 6Y-CARR, neither in PHI nor in RHI. The effect of length, diameter and offset on the 6Y-CARR observed in the PHI, was not detectable in the more complex RHI-cases reflecting its limited clinical relevance by itself in more multifactorial backgrounds. Therefore, results must be interpreted with caution due to considerable system-effects and different utilization-scenarios.

Performance of medial pivot, posterior stabilized and rotating platform total knee arthroplasty based on anteroposterior stability and patient-reported outcome measures; a multicentre double-blinded randomized controlled trial of 210 knees.

BACKGROUND: Despite advancements in total knee arthroplasty (TKA), 10-20% of patients remain dissatisfied after surgery. Improved anteroposterior (AP) stability provided by medial pivot (MP) implants may theoretically lead to higher patient satisfaction. METHODS: AP stability and patient-reported outcome measures (PROMs) at one-year postsurgery were compared between patients who underwent TKA with MP- (n = 121), posterior stabilized (PS; n = 53) and rotating platform (RP; n = 57) implants in a double-blind multicentre randomized controlled trial (Dutch Trial Register: NL6856, 21-02-2018). AP stability was assessed at 30°, 60° and 90° of knee flexion using a KT-2000 arthrometer. PROMs were measured preoperative and one-year postsurgery. RESULTS: MP-TKA provided significant better AP stability at early flexion (30°) compared to PS- and RP-TKA (median [IQR]; 1.79 [1.14-2.77] mm vs. 3.31 [2.51-4.08] mm vs. 2.82 [1.80-4.03] mm, p < 0.001). Additionally, MP-TKA provided significant better AP stability at mid-flexion (60°) compared to PS-TKA (1.75 [1.23-2.36] mm vs. 2.14 [1.49-2.83] mm, p = 0.014). PROM improvements were comparable between implant designs. AP laxity of ≥ 4 mm at early flexion was independently of implant design associated with significantly worse Kujala scores. The incidence of ≥ 4 mm AP laxity at any knee angle was however not significantly different between implant designs. CONCLUSION: MP-, PS- and RP-TKA all provide excellent and comparable results. Although MP-TKA provided better AP stability at early flexion compared to PS- and RP-TKA, this was found to be unrelated to improved PROMs in favour of MP-TKA. More studies focusing on early and mid-flexion performance based differences between MP and other TKA designs are required to confirm our findings. Other non-implant related factors may play a more important role in the performance of TKA and are potentially worthwhile examining.

Comparison of the coverage and rotation of asymmetrical and symmetrical tibial components: a systematic review and meta-analysis.

BACKGROUND: An optimized fit of the tibial component to the resection platform and correct rotational alignment are critical for successful total knee arthroplasty (TKA). However, there remains controversy regarding the superiority of symmetric tibial component versus asymmetric tibial component. The objective of this systematic review and meta-analysis was to evaluate the current evidence for comparing the coverage and rotation of asymmetrical and symmetrical tibial component. METHODS: We searched potentially relevant studies form PubMed, Web of science, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), and China National Knowledge Infrastructure (CNKI), up to 1 March 2023. Data extraction and quality assessment were performed by two independent reviewers. Meta-analysis was conducted using Review Manager 5.4. RESULTS: Sixteen articles were identified. Compared to symmetric tibial component, asymmetric tibial component increased the coverage of the proximal tibial cut surface (MD, -2.87; 95%CI, -3.45 to -2.28; P < 0.00001), improved the prevalence of tibial baseplate underhang (OR, 0.16; 95%CI, 0.07 to 0.33; P < 0.00001) and malrotation (OR, 0.13; 95%CI, 0.02 to 0.90; P = 0.04), and reduced the degree of tibial component rotation (MD, -3.11; 95%CI, -5.76 to -0.47; P = 0.02). But there was no statistical significance for improving tibial baseplate overhang (OR, 0.58; 95%CI, 0.08 to 3.97; P = 0.58). Additionally, no revision had occurred for the two tibial components in the included studies. CONCLUSION: The current evidence shows asymmetric tibial component offer advantages in terms of coverage and rotation compared with symmetric tibial component in TKA.

Comparison of Alignment Accuracy and Clinical Outcomes between a CT-Based, Saw Cutting Robotic System and a CT-Free, Jig-guided Robotic System for Total Knee Arthroplasty.

OBJECTIVE: The different cutting mode of robot-assisted TKAs may influence the accuracy of alignment. The purpose of this study was to compare alignment accuracy and early clinical outcomes between a CT-based, saw cutting robotic system (MAKO) and a CT-free, jig-guided robotic system (ROSA) for total knee arthroplasty (TKA). METHODS: A total of 20 MAKO TKAs and 20 ROSA TKAs from June 2021 to June 2022 were retrospectively analyzed. Differences in the postoperative hip-knee-ankle (HKA) angle, lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), posterior tibial slope (PTS) and 3° outlier frequency of the HKA, LDFA, MPTA and PTS were studied at 3 months and 1 year of follow-up. The operative time and total blood loss (TBL) were compared between these two groups. Clinical outcomes at 1 year after surgery, including range of motion (ROM), Western Ontario McMaster University Osteoarthritis Index (WOMAC) score, and Knee Society Score-2011 (KSS-2011), were also compared between these two groups. RESULTS: The baseline characteristics of the two groups were comparable. There were no significant differences in the mean deviations of postoperative HKA, LDFA, MPTA or PTS between the two groups at 3 months or 1 year (all ps > 0.05). Moreover, there was no significant difference in the percentage of 3° outliers for HKA, LDFA, MPTA, or PTS between the two groups at 3-month or 1-year follow-up (all ps > 0.05). The mean operation time of MAKO was longer than that of ROSA (112.7 ± 12.8 min vs 94.8 ± 23.0 min, p = 0.001), but the mean TBL (1356.7 ± 648.5 mL vs 1384.5 ± 676.3 mL) and transfusion rate (15.0% vs 5.0%) were not significantly different between the two groups (all ps > 0.05). No significant differences were found in postoperative ROM, WOMAC score or KSS score at 1 year (all ps > 0.05). CONCLUSION: The MAKO and ROSA had similar accuracy and precision in TKA alignment. The clinical outcomes at 1 year after surgery were also comparable.

First long-term analysis of survival and clinical outcome in patient-specific instrumentation for total knee arthroplasty: follow-up of a prospective cohort study.

Patient-specific instrumentation (PSI) was introduced to improve post-operative alignment, and consequently the revision rate and clinical results after total knee arthroplasty (TKA). Short- to mid-term data are conflicting regarding these theoretical advantages of PSI. The purpose of this retrospective analysis was to evaluate the survival rate and clinical outcome in PSI TKA 8.4 years after initial surgery. To our knowledge, no other study investigated long-term follow-up of TKA procedures using PSI. From a total cohort of 184 consecutive patients (200 TKA) 136 patients (144 TKA, 72%) were prospectively analysed at a mean follow-up of 8.4 years (±0.4). A survival analysis with all-cause revision of TKA as endpoint was performed. Patient-reported outcome measures (PROMs) were obtained preoperatively and after 1-, 2-, 5-, and 8.4-years of follow-up. Differences between these moments of follow-up were analysed. At final follow-up, 4 TKAs (2%) had undergone revision, all between 2-4 years after primary surgery. Reasons for revision were late infection, aseptic loosening, instability and polyethylene insert breakage. The median score of certain PROMs (WOMAC, VAS, EQ-index, EQ-VAS) decreased compared to previous follow-up scores but were significantly higher than preoperative scores. After 8.4 years of follow-up, no additional revision surgery was performed compared to 5-years postoperatively. Certain PROMs at 8.4-year follow-up decreased compared to earlier moments of follow-up, but all PROMs improved compared to preoperative PROMs.

Cemented is not superior to cementless total knee arthroplasty for complications: a propensity score matched analysis.

INTRODUCTION: There is continued debate regarding the survivorship and revision rate of cementless versus cemented total knee arthroplasty (TKA) prostheses. This includes the assessment of early revision surgery due to aseptic loosenings and periprosthetic joint infections (PJIs). Studies have not always taken into account the impact of comorbidities, such as diabetes, obesity, and tobacco. Therefore, we compared revisions in a large population of patients undergoing cemented or cementless TKAs at 90 days, 1 year, and 2 years. METHODS: A review of an administrative claims database was used to identify patients undergoing primary TKA, either cementless (n = 8,890) or cemented (n = 215,460), from October 1, 2015 to October 31, 2020. Revision surgery for PJI and aseptic loosening were identified with diagnosis and associated procedural codes at 90 days, 1 year, and 2 years and then compared between groups. A propensity matched-analysis was performed for age, sex, Charles Comorbidity Index (CCI) > 3, alcohol abuse, tobacco use, obesity, and diabetes. Chi square tests assessed statistical significance of differences in the matched cohorts using odds ratios (ORs) with 95% confidence intervals (CIs). A P < 0.05 was defined as statistically significant. RESULTS: Cementless TKA was associated with similar revisions rates due to PJIs at 90 days (OR, 1.04, 95% CI 0.79-1.38, p = 0.83), 1 year (OR, 0.93, 95% CI 0.75-1.14, p = 0.53, and 2 years (OR, 0.87, 95% CI 0.73-1.05, p = 0.17) in comparison to the cemented TKA cohort. The odds ratio of revision due to aseptic loosening was similar as well at 90 days (OR, 0.67, 95% CI 0.34-1.31, 0.31), 1 year (OR, 1.09, 95% CI 0.73-1.61, p = 0.76), and 2 years (OR, 1.00, 95% CI 0.73-1.61, p = 0.99). CONCLUSIONS: This study found a comparable risk of PJI and aseptic loosening in cementless and cemented TKA when controlling for several comorbidities, such as tobacco, diabetes, and alcohol. Therefore, with proper patient selection, cementless TKAs can be performed with expectation of low risks of infections and aseptic loosenings.

Knee kinematics are not different between asymmetrical and symmetrical tibial baseplates in total knee arthroplasty: A fluoroscopic analysis of step-up and lunge motions.

PURPOSE: This clinical fluoroscopy study investigated knee kinematics of two different cemented fixed-bearing, posterior-stabilised (PS) total knee arthroplasty (TKA) designs: an asymmetric tibial component including an asymmetric insert designed to optimise personalised balance and fit and its precursor symmetrical design with symmetric insert. METHODS: A consecutive series of patients (16 TKAs from each treatment group) participating in a randomised controlled trial comparing TKA migration was included. The exclusion criterion was the use of walking aids. Flat-panel fluoroscopic recordings of step-up and lunge motions were acquired 1-year postoperatively. Medial and lateral contact points (CPs) were determined to calculate CP displacement, femoral axial rotation and pivot position. Using linear mixed-effects modelling techniques, kinematics between TKA designs were compared. RESULTS: During knee extension between 20° flexion and full extension, the CPs moved anteriorly combined with a small internal femoral rotation (a screw-home mechanism). Whereas CP movement was reversed: femoral rollback, external femoral rotation while flexing the knee between full extension and 20° knee flexion, At larger flexion angles, femoral axial rotation (FAR) occurred around a lateral pivot point both during step-up and lunge. The symmetric design had a 2.3° larger range of FAR compared to the asymmetric design during lunge (p = 0.02). All other kinematics were comparable. CONCLUSION: Despite the differences in design, this study showed that the asymmetric and symmetric PS TKA designs had mostly comparable knee kinematics during step-up and lunge motions. It is therefore expected that the functionality of the successor TKA design is similar to that of its precursor design. LEVEL OF EVIDENCE: Level II, prospective comparative study.

Mobile medial pivot (lateral slide)-type total knee arthroplasty exhibited different motion patterns between under anaesthesia and weight-bearing condition.

PURPOSE: Total knee arthroplasty (TKA), which has medial pivot and mobile-bearing mechanisms, has been developed and clinically used. However, the in vivo dynamic kinematics of the mobile medial pivot-type TKA (MMPTKA) is unclear. This study analysed the in vivo kinematics of MMPTKA in weight-bearing and nonweight-bearing conditions. METHODS: The study included 10 knees that underwent primary TKA using MMPTKA. After TKA, lateral view radiographs of the knee in full extension, 90° of flexion and passive full flexion were taken under general anaesthesia in the nonweight-bearing condition. At least 6 months postoperatively, knee motion during squatting from a weight-bearing standing position was observed using a flat-panel detector and analysed using the three-dimensional-to-two-dimensional image registration technique. RESULTS: Under anaesthesia: in passive full flexion, the anteroposterior (AP) locations of the femoral component's medial and lateral distal points were 10.2 and 16.0 mm posterior, and the rotational angles of the femoral component's X-axis (FCX) and insert were 8.1° external rotation and 18.5° internal rotation to full extension, respectively. Squatting: the AP translations of the femoral component's medial and lateral most distal points were 2.2 and 6.4 mm, and the rotational angles of the FCX and insert were 5.7° and 1.6° external rotation, respectively. Significant differences were observed in the AP translation of the femoral component's medial and lateral most distal points and changes in the insert's rotational angle when comparing under anaesthesia and squatting. CONCLUSIONS: The kinematics of the insert in MMPTKA was significantly influenced by loading and muscle contraction. The femoral component exhibited substantial external rotation and posterior translation under anaesthesia, which may contribute to achieving an optimal range of motion. The insert remained relatively stable during squatting and minimal rotation was observed, indicating good stability. MMPTKA was expected to demonstrate rational kinematics by incorporating mobile and medial pivot mechanisms. LEVEL OF EVIDENCE: Level IV, prospective biomechanical case series study.

The wear and kinematics of two medially stabilised total knee replacement systems.

BACKGROUND: Medially stabilised total knee replacement systems aim to provide a more natural feeling knee replacement by providing increased stability through flexion. The aim of this study was to compare the kinematics and wear of two different medially stabilised total knee replacement systems in an experimental simulation study. The Medial Rotation Knee™ system (MRK) is an early medially stabilised knee (>20 years clinical success); the SAIPH® knee system being a more modern and refined, bone conserving evolution of the original design with a larger size range. METHODS: Three SAIPH and three MRK total knee replacements (MatOrtho Ltd, UK) were investigated. The study was performed on a knee simulator with load controlled input kinematic conditions (ISO 14243-1). 6 million cycles of simulation were carried out with the wear of the UHMWPE tibial components assessed gravimetrically. The resulting anterior-posterior translation and tibial rotation position was measured throughout the study. RESULTS: The mean UHMWPE wear rate was 0.57 ± 0.71 and 1.24 ± 2.0 mm3/million cycles for SAIPH and MRK total knee replacement systems respectively with no significant difference in wear (p = 0.24). Analysis of simulator output kinematics showed a larger range of anterior-posterior motion for SAIPH total knee replacements compared to MRK. The magnitude of tibial rotation was low for both knee replacement systems. CONCLUSION: The small magnitude of anterior-posterior displacement and tibial rotation motion demonstrates the inherent stability of this knee system design offered by the constrained medial compartment. This study shows the potential for medially stabilised knee systems as a low polyethylene surface wear solution.

A morphometric medial compartment-specific unicompartmental knee system: 5 years follow up results from a pilot center.

BACKGROUND: Unicompartmental Knee Arthroplasty (UKA) is a valuable solution for the treatment of medial osteoarthritis of the knee. New implants feature designs for the elective substitution of a specific compartment. Aim of this study was to assess the survivorship and functional outcomes at minimum 4 years of the first 60 implanted patients in a pilot center of a new medial UKA as the evolution of a well performing long lasting fixed bearing implant. METHODS: Between June 2017 and the end of 2018, 60 medial UKA were implanted in 58 patients. All patients were available for the last follow up and were analyzed prospectively. 37 were females and 21 were males with a mean age of 67 years (SD 10,71) and a mean of BMI 27.16 (SD 3.94) for the male population and of 26.73 (SD 4.05) for the female population. RESULTS: At final follow up the mean Oxford Knee Score (OKS) was 44,02 (SD 3,1) and the mean Forgotten Joint Score (FJS) 78,6 (SD 7,9). The Knee Society Score (KSS) score was 95,2 for the "knee" score and 89.8 for the "function" score. No patients were revised. Kaplan-Meyer survival estimate showed a 100% survivorship at final follow up. No progressive radiolucent lines were found and no direct or indirect signs of polyethylene wear were registered on the final radiographs. CONCLUSIONS: This new implant demonstrated promising clinical results with an excellent survival rate at short to midterm follow- up. Further follow up is needed to confirm this trend at longer term.

Four-Year Outcomes of Cementless Versus Cemented Fixation of a Newly Introduced Total Knee Arthroplasty Design.

BACKGROUND: Aseptic loosening continues to be a major cause of failure of total knee arthroplasty (TKA). Although cemented fixation remains the gold standard, there is renewed interest in cementless fixation as a means of decreasing this risk via biologic fixation. The purpose of this study was to evaluate the clinical outcomes of cemented and cementless versions of a newly introduced TKA design at an average of 4 years postoperatively. MATERIALS AND METHODS: This was a retrospective case-control study of 100 primary TKAs comparing cementless vs cemented TKAs using the same cruciate-retaining implant design (ATTUNE Knee System; DePuy Synthes). Fifty patients undergoing cementless TKA with a mean age of 60.8 years (range, 48-71 years) and body mass index (BMI) of 31.6 kg/m2 (range, 23.7-41.9 kg/m2) were matched to 50 patients undergoing primary cemented TKA with a mean age of 62.7 years (range, 51-73 years) and BMI of 30.1 kg/m2 (range, 24.6-43.9 kg/m2). The mean follow-up was 4.2 years (range, 4.0-4.4 years) in the cementless group and 7.6 years (range, 7.5-7.7 years) in the cemented group. Complications, clinical outcomes using the Knee Society Score (KSS), and radiographic analyses were evaluated at final follow-up. Student's t tests were used for statistical analyses. RESULTS: There was no statistical difference in age, BMI, and preoperative KSS between the two groups (P=.12, P=.15, and P=.55, respectively). There were no complications or reoperations in either cohort. There were no statistical differences in range of motion and total KSS at final follow-up between the two groups. Final total KSS had a mean of 91.1 for the cementless group and 93.7 for the cemented group. There was no radiographic evidence of component subsidence or loosening in either cohort. CONCLUSION: When compared with its cemented counterpart, the newly introduced cementless TKA design had similar excellent clinical improvements and radiologic results at an average of 4 years of follow-up. [Orthopedics. 2024;47(3):161-166.].

Aseptic loosening of the option stemmed tibial tray in the Zimmer NexGen LPS total knee arthroplasty system.

BACKGROUND: We investigated the relationship between the backside deformation of polyethylene (PE) tibial inserts and aseptic loosening of the Option stemmed tibial tray used with Zimmer NexGen posterior-stabilised (PS) devices. We hypothesized that explanted inserts used in PS designs would exhibit greater extents of PE backside deformation than those used in equivalent cruciate retaining (CR) designs and that PE inserts retrieved from total knee arthroplasties (TKAs) revised for aseptic tibial tray loosening would exhibit greater extents of backside deformation than TKAs revised for other reasons. METHODS: A total of 73 explanted fixed-bearing TKAs (42 CR and 31 PS) were examined. PE components underwent geometric examination with a coordinate measuring machine using validated techniques. Multiple regression modelling was used to identify variables associated with revision secondary to aseptic loosing and to determine factors associated with increased PE backside deformation. RESULTS: PE inserts retrieved from TKAs with aseptic loosening had significantly greater backside deformation than those retrieved from TKAs revised for other reasons (p < 0.001). Greater PE backside deformation was significantly associated with larger tray/insert clearance heights (p < 0.001), thinner inserts (p < 0.001) and PS TKAs (p = 0.001). CONCLUSION: PE backside deformation was significantly greater in the PS TKAs. This may provide one explanation for the increased rate of aseptic loosening reported with the Option tibial tray used with the Legacy Posterior Stabilised (LPS) system.

Longer term follow up of outcomes following implantation of a modular rotating hinge knee prosthesis: 53 implants at mean 7.6 year follow up.

BACKGROUND: Rotating hinge knee replacements are becoming more common but have historically had high complication and failure rates. This study is one of the largest to assess the implant survival and patient outcomes of a third-generation rotating hinge knee replacement at a single tertiary orthopaedic centre. METHODS: Data for consecutive operations at our tertiary unit between 2006 to 2020 were assessed with review of electronic patient and radiology records. The Oxford Knee Score was used to assess outcomes and the Kaplan Meier method used to estimate survivorship. RESULTS: 53 rotating hinge knees were implanted in 46 patients (13 male, 33 female) at a mean age of 67.8 years. 21 were primary and 32 were revision procedures. Indications for use of this implant included instability, loosening, fracture and infection. Survivorship was 77.8% at the mean follow up of 7.6 years. A total of 29 complications were noted with ongoing pain, stiffness, infection and patellofemoral symptoms being the most common. 8% of unresurfaced patellas required a subsequent secondary resurfacing. The Oxford Knee Score demonstrated a significant improvement from 14.6 preoperatively to 27.5 at one year postoperatively, which was maintained in the longer term. CONCLUSION: The third-generation rotating hinge knee implant in use at our unit has improved outcomes for patients. The survivorship of the implant is comparable to the published literature, although there is a paucity of data. The complication rates remain relatively high and patients should be counselled appropriately. We advise resurfacing the patella to avoid the need for secondary procedures.

Clinical and Biomechanical Evaluation of Mid-Level Constrained and Posterior-Stabilized Polyethylene Inserts in Primary Total Knee Arthroplasty: An Analysis of 12,674 Cases.

BACKGROUND: Mid-level constraint polyethylene designs provide additional stability in total knee arthroplasty (TKA). The purposes of this study were to (1) compare the survivorship and reason for revision between mid-level inserts and posterior-stabilized (PS) used in primary TKA and (2) evaluate the biomechanical constraint characteristics of mid-level inserts. METHODS: We reviewed all cases of primary TKA performed at our institution from 2016 to 2019 using either PS or mid-level constrained inserts from 1 of 6 manufacturers. Data elements included patient demographics, implants, reasons for revision, and whether a manipulation under anesthesia was performed. We performed finite element analyses to quantify the varus/valgus and axial-rotation constraint of each mid-level constrained insert. A one-to-one propensity score matching was conducted between the patients with mid-level and PS inserts to match for variables, which yielded 2 cohorts of 3,479 patients. RESULTS: For 9,163 PS and 3,511 mid-level TKAs, survivorship free from all-cause revision was estimated up to 5 years and was lower for mid-level than PS inserts (92.7 versus 94.1%, respectively, P = .004). When comparing each company's mid-level insert to the same manufacturer's PS insert, we found no differences in all-cause revision rates (P ≥ .91) or revisions for mechanical problems (P ≥ .97). Using propensity score matching between mid-level and PS groups, no significant differences were found in rates of manipulation under anesthesia (P = .72), all-cause revision (P = .12), revision for aseptic loosening (P = .07), and revision for instability (P = .45). Finite element modeling demonstrated a range in varus/valgus constraint from ±1.1 to >5°, and a range in axial-rotation constraint from ±1.5 to ±11.5° among mid-level inserts. CONCLUSIONS: Despite wide biomechanical variations in varus/valgus and axial-rotation constraint, we found minimal differences in early survivorship rates between PS and mid-level constrained knees.

Lower Perioperative Complication Rates and Shorter Lengths of Hospital Stay Associated With Technology-Assisted Total Knee Arthroplasty Versus Conventional Instrumentation in Primary Total Knee Arthroplasty.

BACKGROUND: The use of technology allows increased precision in component positioning in total knee arthroplasty (TKA). The objectives of this study were to compare (1) perioperative complications and (2) resource utilization between robotic-assisted (RA) and computer-navigated (CN) versus conventional (CI) TKA. METHODS: A retrospective cohort study was performed using a national database to identify patients undergoing unilateral, primary elective TKA from January 2016 to December 2019. A total of 2,174,685 patients were identified and included RA (69,445), CN (112,225), or CI (1,993,015) TKA. Demographics, complications, lengths of stay, dispositions, and costs were compared between the cohorts. Binary logistic regression analysis was performed. RESULTS: The RA TKA cohort had lower rates of intraoperative fracture (0.05 versus 0.08%, P < .05), respiratory complications (0.6 versus 1.1%, P < .05), renal failure (1.3 versus 1.7%, P < .05), delirium (0.1 versus 0.2%, P < .05), gastrointestinal complications (0.04 versus 0.09%, P < .05), postoperative anemia (8.9 versus 13.9%, P < .05), blood transfusion (0.4 versus 0.9%, P < .05), pulmonary embolism, and deep vein thrombosis (0.1 versus 0.2%, P < .05), and mortality (0.01 versus 0.02%, P < .05) compared to conventional TKA, though the cohort did have higher rates of myocardial infarction (0.09 versus 0.07%, P < .05). The CN cohort had lower rates of myocardial infarction (0.02 versus 0.07%, P < .05), respiratory complications (0.8 versus 1.1%, P < .05), renal failure (1.5 versus 1.7%, P < .05), blood transfusion (0.8 versus 0.9%, P < .05), pulmonary embolism (0.08 versus 0.2%, P < .05), and deep vein thrombosis (0.2 versus 0.2%, P < .05) over CI TKA. Total cost was increased in RA (16,190 versus $15,133, P < .05) and CN (17,448 versus $15,133, P < .05). However, the length of hospital stay was decreased in both RA (1.8 versus 2.2 days, P < .05) and CN (2.1 versus 2.2 days, P < .05). CONCLUSIONS: Technology-assisted TKA was associated with lower perioperative complication rates and faster recovery.

Analysis of alternate material Onyx™ for total knee arthroplasty instrumentation sets.

CONTEXT: A 25-pound weight limit is currently set on containerized instrumentation sets by the Association of periOperative Registered Nurses (AORN) and the Association for the Advancement of Medical Instrumentation (AAMI), in order to reduce strain on the staff and ensure that the sets are not too crowded in order to preserve sterilization and drying of the instruments. This is pushing companies to reduce the weight and number of instrumentation sets for the operating room. One solution has been to explore the viability of new, lighter materials such as Onyx. OBJECTIVES: The goal of this study is to evaluate the novel material Onyx as a viable material utilized in reusable total knee arthroplasty (TKA) instrumentation sets utilizing traditional steam sterilization as the sterilization method. METHODS: Mechanical and biocompatibility tests according to the American Society for Testing Materials (ASTM) and International Organization for Standardization (ISO) 10,993 were run to evaluate the Onyx Material to see if it would be a viable alternative to the stainless and martensitic steel that is currently being utilized. RESULTS: Gross warping and cracking after 10 rounds of sterilization was observed. This was qualitatively worse in the Onyx without a carbon fiber component. The Onyx material did not meet biocompatibility standards for its application. CONCLUSIONS: Onyx was determined to not be a viable material for TKA instruments regarding multiple high-pressure and -temperature sterilizations and cytotoxic cell testing.

3D-printed, patient-specific cutting guides improve femoral and tibial cut alignment in canine total knee replacement.

OBJECTIVES: The purpose of this cadaveric study was to determine whether patient-specific guides (PSGs) improve the accuracy of tibial and femoral cut alignment in canine total knee replacement (TKR), as compared with generic cutting guides. STUDY DESIGN: Original research. ANIMALS: Sixteen pelvic limbs from skeletally mature medium- to large-breed canine cadavers. METHODS: Specimens were randomly allocated to one of two groups (PSG or Generic; N = 8/group). In the Generic group, femoral and tibial ostectomies were made using the standard canine TKR femoral cutting blocks and tibial alignment guide. In the PSG group, the cuts were made using a series of custom 3D-printed cutting guides. "Planned" and "actual" tibial and femoral cut alignments were compared in the frontal and sagittal planes, and errors were calculated by subtracting actual from planned values. RESULTS: Use of 3D-printed PSGs improved tibial cut alignment in the frontal plane but not the sagittal plane. PSGs also improved the alignment of the cranial and distal femoral ostectomies but did not impact varus-valgus alignment. CONCLUSIONS: These findings support the use of PSGs for TKR in dogs. Clinical trials are now needed to determine whether the benefits of PSGs translate into measurable improvements in joint function and implant longevity. CLINICAL SIGNIFICANCE: PSGs have the potential to improve femoral and tibial component alignment in canine TKR.

Long-term outcomes of one single-design varus valgus constrained versus one single-design rotating hinge in revision knee arthroplasty after over 10-year follow-up.

BACKGROUND: The appropriate degree of constraint in knee prosthetic revision is unknown, necessitating the use of the lowest possible constraint. This study aimed to compare the long-term clinical and survival results of revision with rotation hinge knee (RHK) VS constrained condylar constrained knee (CCK) implants. METHODS: Overall, 117 revision case were prospectively reviewed and dividing into two groups based on the degree of constraint used, using only one prosthetic model in each group (61 CCK vs 56 RHK). All implants were evaluated for a minimum of 10 years. Survival of both implants at the end of follow-up, free from revision for any cause, aseptic loosening, and septic cause was compared. RESULTS: Better results were seen with use of the RHK in joint ranges of (p = 0.023), KSCS (p = 0.015), KSFS (p = 0.043), and KOOS (p = 0.031). About 22.2% of the cases required repeat surgery (11.7% RHK vs 29.6% CCK, p = 0.023). Constrained condylar implants had a significantly lower survival rates than rotating hinge implants (p = 0.005), due to a higher aseptic loosening rate (p = 0.031). CONCLUSION: Using a specific RHK design with less rotational constraint has better clinical and survival outcomes than implants with greater rotational constraint, such as one specific CCK.

Kinematics and kinetics comparison of ultra-congruent versus medial-pivot designs for total knee arthroplasty by multibody analysis.

Nowadays, several configurations of total knee arthroplasty (TKA) implants are commercially available whose designs resulted from clinical and biomechanical considerations. Previous research activities led to the development of the so-called medial-pivot (MP) design. However, the actual benefits of the MP, with respect to other prosthesis designs, are still not well understood. The present work compares the impact of two insert geometries, namely the ultra-congruent (UC) and medial-pivot (MP), on the biomechanical behaviour of a bicondylar total knee endoprosthesis. For this purpose, a multibody model of a lower limb was created alternatively integrating the two implants having the insert geometry discretized. Joint dynamics and contact pressure distributions were evaluated by simulating a squat motion. Results showed a similar tibial internal rotation range of about 3.5°, but an early rotation occurs for the MP design. Furthermore, the discretization of the insert geometry allowed to efficiently derive the contact pressure distributions, directly within the multibody simulation framework, reporting peak pressure values of 33 MPa and 20 MPa for the UC and MP, respectively. Clinically, the presented findings confirm the possibility, through a MP design, to achieve a more natural joint kinematics, consequently improving the post-operative patient satisfaction and potentially reducing the occurrence of phenomena leading to the insert loosening.