Ultracongruent Research Articles

No difference in patient-reported outcomes or range of motion between ultracongruent and posterior stabilized total knee arthroplasty: A randomized controlled trial.

Ultracongruent (UC) inserts were designed to overcome potential issues with posterior stabilized (PS) inserts, including bone resection, post-breakage, and patellar clunk syndrome. However, there remains a shortage of high-quality studies directly comparing this insert design to the established PS Total Knee Arthroplasty (TKA). This prospective randomized controlled trial (RCT) aimed to compare clinical outcomes, range of motion, and complications of UC and PS TKA. Ninety six patients with primary knee osteoarthritis were randomly assigned to either the PS or the UC group. There were no significant differences between the groups regarding age, body mass index, sex, or Osteoarthritis grade. The measured outcomes were Knee Injury and Osteoarthritis Outcome Score (KOOS) and Range of Motion (ROM), recorded preoperatively and at 3 and 6 months postoperative. Both the patient and interviewer were blinded to the allocation group. Eighty one patients were included in the analysis, with a mean follow-up of 1.3 years. Both groups exhibited a gradual improvement in KOOS. Still, no statistically significant differences were observed between the groups during the follow-up examinations at 3 or 6 months in KOOS or range of motion. No complication occurred in either group during the follow-up period. Both designs demonstrated comparable positive outcomes, reinforcing the viability of UC designs as an alternative to the well-established PS TKA. Level l, randomized controlled trial.

Tibial insert design significantly alters knee kinematics using a single cruciate-retaining total knee implant.

Patient dissatisfaction is not uncommon following primary total knee arthroplasty. One proposed method to alleviate this is by improving knee kinematics. Therefore, we aimed to answer the following research question: are there significant differences in knee kinematics based on the design of the tibial insert (cruciate-retaining (CR), ultra-congruent (UC), or medial congruent (MC))? Overall, 15 cadaveric knee joints were examined with a CR implant with three different tibial inserts (CR, UC, and MC) using an established knee joint simulator. The effects on coronal alignment, medial and lateral femoral roll back, femorotibial rotation, bony rotations (femur, tibia, and patella), and patellofemoral length ratios were determined. No statistically significant differences were found regarding coronal alignment (p = 0.087 to p = 0.832). The medial congruent insert demonstrated restricted femoral roll back (mean medial 37.57 mm; lateral 36.34 mm), while the CR insert demonstrated the greatest roll back (medial 42.21 mm; lateral 37.88 mm; p < 0.001, respectively). Femorotibial rotation was greatest with the CR insert with 2.45° (SD 4.75°), then the UC insert with 1.31° (SD 4.15°; p < 0.001), and lowest with the medial congruent insert with 0.8° (SD 4.24°; p < 0.001). The most pronounced patella shift, but lowest patellar rotation, was noted with the CR insert. The MC insert demonstrated the highest level of constraint of these inserts. Femoral roll back, femorotibial rotation, and single bony rotations were lowest with the MC insert. The patella showed less shifting with the MC insert, but there was significantly increased rotation. While the medial congruent insert was found to have highest constraint, it remains uncertain if this implant recreates native knee kinematics or if this will result in improved patient satisfaction.

Ultracongruent Versus Posterior-Stabilized Polyethylene: No Difference in Anterior Knee Pain but Decreased Noise Generation.

Noise generation and anterior knee pain can occur after primary total knee arthroplasty (TKA) and may affect patient satisfaction. Polyethylene design in cruciate-sacrificing implants could be a variable influencing these complications. The purpose of this study was to analyze the effect of polyethylene design on noise generation and anterior knee pain. We prospectively reviewed a cohort of patients who underwent primary TKA between 2014 and 2022 by a single surgeon using either a posterior-stabilized (PS) or ultracongruent (UC) polyethylene of the same implant design. The primary outcomes were measured through a noise generation questionnaire and the Knee Injury and Osteoarthritis Outcome Score-Patellofemoral score. A total of 409 TKA procedures were included, 153 (37.4%) PS and 256 (62.6%) UC. No difference was noted in the Knee Injury and Osteoarthritis Outcome Score-Patellofemoral score between PS and UC designs (71.7 ± 26 versus 74.2 ± 23.2, P = 0.313). A higher percentage of patients in the PS cohort reported hearing (32.7% versus 22.3%, P = 0.020) or feeling noise (28.8 versus 20.3, P = 0.051) coming from their implant. No notable difference was observed in noise-related satisfaction rates. Independent risk factors of noise generation were age (OR, 0.96; P = 0.006) and PS polyethylene (OR, 1.61; P = 0.043). Noise generation was associated with decreased patient-reported outcome measure scores (P < 0.001). While there was no difference in anterior knee pain between PS and UC polyethylene designs, PS inserts exhibit higher rates of noise generation compared with UC. Noise generation had comparable satisfaction but was associated with decreased patient-reported outcome measure scores.

Ultracongruent Polyethylene Liners Do Not Affect Survival of Total Knee Arthroplasty for Valgus Deformity

BackgroundValgus knee deformity is observed in nearly 10% of patients undergoing total knee arthroplasty (TKA). The degree of polyethylene constraint required to balance a valgus knee remains controversial, and historically, posterior-stabilized (PS) designs have been favored. This study evaluated the survivorship of TKA done in valgus knees based on implant design and specifically compared posterior-stabilized (PS) and ultracongruent (UC) liners. MethodsA total of 549 primary TKAs performed on valgus knees by fellowship-trained arthroplasty surgeons from 2013 to 2019 were reviewed. Demographics, comorbidities, degrees of preoperative deformity, implants used, and all-cause revisions until final follow-up were recorded. Cox regression analyses evaluated survival to all-cause revision in each cohort. The mean follow-up was 4.9 years (range, 2 to 9). ResultsThere were 403 UC liners compared to 146 PS liners. There was no difference in patient age (68 versus 67 years; P = .30), body mass index (30.9 versus 30.4; P = .36), or degree of deformity (8.6 versus 8.8 degrees; P = .75) between the cohorts. At final follow-up, there were 5 revisions in the PS cohort (3.4%) versus 11 revisions in the UC cohort (2.7%) (P = .90). The most common reason for revision in both cohorts was periprosthetic joint infection (4 PS; 8 UC). Multivariable regression analyses controlling for age, body mass index, Elixhauser comorbidity score, sex, and degree of deformity demonstrated UC polyethylene liners were not associated with revision (hazard ratio 0.76; 95% confidence interval [CI] 0.26 to 2.21; P = .62). There was no difference in eight-year survivorship to all-cause revision, including aseptic and septic failure. ConclusionsAlternative polyethylene liners from the historically utilized PS liners for TKA for valgus deformity did not reduce survivorship. With modern polyethylene designs, UC inserts can be utilized for this deformity without increasing the risk of failure.

Clinical Relevance of Posterior Osteophyte Formation in Ultra-congruent Total Knee Arthroplasty: Midterm Radiographic Rollback and Impingement Analysis.

Posterior femoral condylar osteophytes were frequently observed in patients with the ultra-congruent (UC) deep-dish design prosthesis. Therefore, the purpose of the present study was to verify the clinical relevance of osteophyte formation in the UC design. From March 2014 to February 2018, a comparative study was conducted on 96 knees using the UC design. They were divided into 2 groups (group 1: osteophyte +, group 2: osteophyte -). Intraoperative findings, indirect femoral rollback assessment using 30° flexion and active full flexion lateral radiographs, serial change of the osteophyte, and outcomes were compared. The mean follow-up period was 49.35 ± 3.47 months in group 1 and 47.52 ± 3.37 months in group 2. Posterior component coverage was significantly different between the groups: group 1 exhibited more underhang and group 2 exhibited more overhang (p = 0.022). On the indirect assessment of the femoral rollback, there was a statistically significant difference in deep flexion and change in distance (p < 0.001 and p < 0.001, respectively). There was no statistical difference between the 2 groups in the American Knee Society knee and function score, and group 2 showed significant improvement in pain compared to group 1 in Western Ontario and McMaster University Arthritis Index pain score (p = 0.029). Posterior condylar osteophyte formation was related to posterior impingement. It was more frequently observed in the underhang of the femoral component and insufficient femoral rollback. In addition, it changed with time and caused negative effects, including a gradual decrease in flexion and more pain.

Comparison of ultra-congruent anterior-stabilized vs. a posterior cruciate substituting total knee arthroplasty for osteoarthritis with severe varus knee deformity: comparable 2 year outcomes with two design.

In this retrospective study, we compared the functionality and clinical outcomes of patients with severe varus knees who underwent total knee arthroplasty (TKA) that used prostheses with either a posterior stabilized (PS) design or an ultra-congruent (UC) design. Primary TKA was performed in 161 patients; the UC device was used in 82 (51%) cases and the PS device in 79 (49%). Preoperatively and at the final follow-up examination, all patients were evaluated by orthoroentgenography. The mechanical axis angle and radiolucent lines were evaluated according to the Knee Society Roentgenographic Evaluation System on preoperative and 5-year follow-up radiographs. Total Knee Society Score (KSS) (knee score/function score) and Visual Analog Scale scores were obtained at the final follow-up examination. Demographic and surgical data and revision rates were evaluated for all patients. Postoperative angle values were significantly decreased in both the UC and PS groups (p<0.001 and p<0.001, respectively). Postoperative flexion range of motion values were significantly increased in both the UC and PS groups (p<0.001 and p<0.001, respectively). The postoperative KSS function scores were not significantly different between the groups (p=0.194). The mean surgical time of the PS group (54.99±4.18 minutes) was significantly higher than that of the UC group (46.02±4.48 minutes) (p<0.001). No notable differences were found between the UC and PS groups with respect to the clinical and functional parameters examined. Based on these results, UC TKA can be considered a safe alternative to PS TKA in severe varus knees.

Inserting the best knee: A short-term analysis of posterior stabilized versus cruciate substituting ultracongruent tibial inserts for total knee replacement

Objectives: As the posterior cruciate ligament is a primary stabilizer of the knee, it is functionally replaced using posterior stabilized (PS) or anterior stabilized ultracongruent (UC) inserts in cases where it is attenuated or requires resection. This study compared PS and UC inserts in terms of functional and pain scores in patients undergoing total knee replacement (TKR). Methods: This prospective randomized study included 90 consecutive patients who underwent total TKR; PS and UC inserts were used in 47 and 43 patients, respectively. Outcomes were measured over 1 year. The duration of surgery was recorded, and the pain was assessed using the Visual Analog Scale score; functional outcomes were evaluated by assessment of the range of motion (ROM), Knee Society Score, and joint stability. All parameters and scores were assessed pre-operatively, immediately post-operative, 1 month, 3 months, and at 1-year follow-up. Results: The groups showed no significant differences and matched similarly in terms of body mass index, sex, or age. At a minimum of 1-year follow-up, TKR using either insert significantly improved the mean ROM and Knee Society and functional scores, which were comparable between the groups. Overall, 14 and 13 patients with UC and PS inserts, respectively, had excellent outcomes; 2 and 1 patients from the PS and UC groups, respectively, were lost to follow-up. Surgery was significantly shorter in the UC group. Although the Visual Analog Scale score had reduced significantly in both groups at the end of 3 months, one patient from the PS group had persistent knee pain with decreased ROM. Conclusion: The inserts showed no significant differences in terms of the ROM and Knee Society and functional scores. Surgery was notably shorter in the UC group (by 5 min). TKR using UC inserts is an effective alternative in patients with small bony geometry and may preserve intercondylar bone.

Clinical relevance of roll-back replacement of ultra congruent total knee arthroplasty: comparison of mid-term outcomes with posterior stabilizing design.

The outcomes of total knee arthroplasty (TKA) remain controversial, and we do not know which factors are important for successful outcomes. This study aimed to compare the mid-term outcomes of different conceptual designs by evaluating the radiological and clinical outcomes. A total of 478 total knee arthroplasties (TKAs) were enrolled and allocated into groups I [posterior stabilizing (PS) with anterior referencing (AR)], II [PS with posterior referencing (PR), and III [ultra-congruent (UC) TKA)]. Preoperative findings, last follow-up clinical outcomes, and final follow-up radiological and indirect assessments of the femoral rollback were compared between the groups. The mean follow-up period was 72.6 ± 12.9months. The tourniquet was used samely applied to every group. Flexion contracture was significantly larger in group III than in groups I and II (3.3 ± 2.7, p < 0.001), and further flexion was significantly smaller in group III (130.0° ± 2.7°, p < 0.001). Among the radiological parameters, posterior osteophyte formation was the most common in group III (67.8%). The rollback distance was significantly smaller in group III than in groups I and II (p < 0.001). The active deep flexion angle was affected by the posterior condylar offset (PCO) ratio, and the contact point changed the distance (p < 0.05). PS TKAs showed better ROMs than UC TKAs; however, no differences were noted in the clinical outcome scales. The flexion angle was affected by the PCOR and rollback at both PS and UC TKAs. However, rollback negatively affected the flexion angle during UC TKAs. An inappropriate femoral rollback was identified, and femoral osteophyte formation was determined to be the most prominent in UC TKAs. Level of evidence Level III comparative study.

Ultracongruent Designs Compared to Posterior-Stabilized and Cruciate-Retaining Tibial Inserts – What Does the Evidence Tell Us? A Systematic Review and Meta-Analysis

BackgroundPosterior-stabilized (PS) and cruciate-retaining (CR) have been the most common tibial designs used in total knee arthroplasty. Ultra-congruent (UC) inserts are becoming popular because they preserve bone without relying on the posterior cruciate ligament balance and integrity. Despite increasing use, there is no consensus on how UC inserts perform versus PS and CR designs. MethodsA comprehensive literature search of 5 online databases was performed for articles from January 2000 to July 2022 comparing the kinematic and clinical outcomes of PS or CR tibial inserts to UC inserts. There were nineteen studies included. There were 5 studies comparing UC to CR and 14 comparing UC to PS. Only one randomized controlled trial (RCT) was rated “good quality”. ResultsFor CR studies, pooled analyses showed no difference in knee flexion (n = 3, P = .33) or Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores (n = 2, P = .58). For PS studies, meta-analyses showed better anteroposterior stability (n = 4, P < .001) and more femoral rollback (n = 2, P < .001) for PS but no difference in knee flexion (n = 9, P = .55) or medio-lateral stability (n = 2, P = .50). There was no difference with WOMAC (n = 5, P = .26), Knee Society Score (n = 3, P = .58), Knee Society Knee Score (n = 4, P = .76), or Knee Society Function Score (n = 5, P = .51). ConclusionAvailable data demonstrates there are no clinical differences between CR or PS and UC inserts in small short-term studies ending around 2 years after surgery. More importantly, high-quality research comparing all inserts is lacking, demonstrating a need for more uniform and longer-term studies beyond 5 years after surgery to justify increased UC usage.

Favorable outcomes of posterior cruciate-stabilized inserts over ultracongruent inserts in total knee arthroplasty.

Posterior cruciate-stabilized (PS) and ultracongruent (UC) inserts are used during total knee arthroplasty (TKA), but superiority in gaining postoperative knee flexion and functionality remains contested. Therefore, this study compared postoperative outcomes between PS and UC inserts. A retrospective review evaluated unilateral or bilateral TKAs with PS or UC inserts from August 2011 to March 2020. Nonparametric statistics were performed to evaluate differences in patient demographics, pre- and postknee flexion and Knee Society Knee (KSS-K) and Function Score (KSS-F). Univariate and multivariable regressions were performed to evaluate the influence on postoperative knee flexion ≥ 120°, presented as odds ratios (OR) and 95% confidence intervals (CI). Patient demographics were not significantly different between the 577 PS and 399 UC knees evaluated. Postoperatively, a larger proportion of UC knees demonstrated knee flexion < 120° (36.0% vs. 18.6%, p < 0.001) and lower KSS-K (91.0 ± 8.7 vs. 91.6 ± 10.3, p < 0.001) and KSS-F (76.8 ± 21.6 vs. 79.9 ± 21.6, p = 0.007) than the PS group. The PS group had greater improvement in flexion angle (4.9° ± 14.9° vs. 1.0° ± 15.6°, p < 0.001) and KSS-F (27.3 ± 23.3 vs. 23.1 ± 25.3, p = 0.007) as compared to that of UC patients. Patients with preoperative flexion < 120° (OR 2.787, CI 2.066-3.761; p < 0.001), higher body mass index (OR 1.033, CI 1.006-1.061; p = 0.017) and UC insert (OR 2.461, CI 1.832-3.307; p < 0.001) were less likely to achieve flexion ≥ 120°. Favorable clinical and functional outcomes were noted in the PS group as compared to UC inserts in TKA. The greater improvement in overall knee flexion may suggest the PS insert may be especially appropriate for patients with lower preoperative range of motion. III, retrospective comparative study.

A prospective comparison of total knee arthroplasty using ultra-congruent, condylar-stabilizing, and posterior-stabilized devices implanted with kinematic alignment: better 2-year outcomes with ultra-congruent

PurposeThis study compared the 5-year results of posterior cruciate ligament (PCL)-sacrificing total knee arthroplasty (TKA) with either a post and cam posterior-stabilized (PS) device, a dished, congruent condylar-stabilizing (CS) device, or a deep-dished ultra-congruent (UC) device. The hypothesis was that the clinical and radiographic outcomes would be equivalent. CS and PS participants were part of a prospective, randomized trial, and UC participants were part of a separate prospective, non-randomized protocol that was otherwise identical. A kinematic alignment surgical technique was utilized.MethodsParticipants were assessed preoperatively, and postoperatively at 6 weeks, 6 months, and annually for 5 years by Knee Society Score (KSS), SF-36 v2, Lower Extremity Activity Scale (LEAS), and physical and radiographic evaluation. There were 116 CS/PS participants and 69 UC participants who participated in the study.ResultsTourniquet (P = .02) and operative (P = .01) times for the CS and UC groups were significantly shorter than the PS group. KSS Function scores were better for the UC group than the CS and PS groups at 6 months (P = .04) and 1 year (P = .03), and better in the UC group vs. CS at 2 years (P = .04). The KSS Pain-only score was also better in the UC compared to PS at 6 months (P = .04). There were no significant differences for the KSS Pain/Motion scores, flexion, SF-36, and LEAS scores at any time.ConclusionThese data confirm the hypothesis that there are no clinically meaningful significant differences in outcomes between the three groups at a 5-year minimum follow-up, though there is a trend toward less pain and better function at earlier visits in the UC group.Level of evidenceII.

A TKA Insert with A Lateral Flat Articular Surface Maximizes External and Internal Tibial Orientations without Anterior Lift-Off Relative to Low- and Ultracongruent Surfaces.

Background: In total knee arthroplasty (TKA), inserts can have different levels of medial and lateral congruency determined by the acuteness of the upslopes of the anterior and posterior articular surfaces. The present study evaluated an insert with different levels of lateral congruency and a medial ball-in-socket congruency to test the hypothesis that a lateral flat (F) insert maximizes external tibial orientation at extension and internal orientation at 90° flexion and lowers the incidence of anterior lift-off relative to low-congruent (LC) and ultracongruent (UC) lateral inserts. Methods: Two surgeons treated 23 patients with unrestricted caliper-verified kinematic alignment (KA) and posterior cruciate ligament (PCL) retention. They randomly trialed inserts with a medial radial dial that functioned as a built-in goniometer by measuring the tibial orientation relative to a sagittal line on the femoral trial component. Anterior lift-off of the insert from the baseplate indicated PCL tightness. Results: The F insert’s mean of 9° of external tibial orientation was higher than that of the LC (5°, p < 0.0001) and UC inserts (2°, p < 0.0001). The −13° of internal tibial orientation at 90° flexion was higher than that of the LC (−9°, p < 0.0001) and UC inserts (−7°, p < 0.0001). The 0% incidence of anterior lift-off was less than that of the LC (26%) and UC inserts (57%) (p < 0.0001). Conclusions: Surgeons and implant manufacturers should know that adding congruency to the lateral articular surface limits external tibial orientation in extension and internal tibial orientation at 90° flexion and overtightens the PCL. These rotational limitations and flexion space tightness can adversely affect patellofemoral tracking and knee flexion.

No kinematical difference between ultra-congruent and medial-congruent total knee arthroplasty when implanted with mechanical alignment: an in vivo dynamic RSA study

PurposeTo explore in vivo kinematical behavior of the same total knee arthroplasty (TKA) cruciate-retaining (CR) femoral design with either medial-congruent (MC) or ultra-congruent (UC) inlay using model-based dynamic radiostereometric analysis (RSA). The hypothesis was that there would be comparable kinematics between the two groups.MethodsA cohort of 16 randomly selected patients (8 MC Persona Zimmer, 8 UC Persona Zimmer) was evaluated through dynamic radiostereometric analysis (RSA) at a minimum of 9 months after TKA, during the execution of a sit-to-stand. The antero-posterior (AP) translation of the femoral component and the AP translation of the low point of medial and lateral femoral compartments were compared through Student’s t test (p < 0.05).ResultsBoth groups showed a medial pivot behavior, with a significantly greater anterior translation of the Low Point of the lateral compartment with respect to the medial compartment (MC medial range: 2.4 ± 2.4 mm; MC lateral range: 7.7 ± 3.0 mm; p < 0.001 – UC medial range: 3.3 ± 3.3 mm; UC lateral range: 8.0 ± 3.2 mm; p < 0.001). A statistically significant greater degree of flexion was clinically recorded at follow-up visit in the MC group respect to the UC group (126° vs 101°—p = 0.003).ConclusionThe present study did not show difference in the medial pivot behavior between ultra-congruent and medial-congruent total knee arthroplasty when implanted with mechanical alignment; however, the MC group demonstrated a greater degree of flexion. The MC design examined is a valid alternative to the UC design, allowing to achieve a screw-home movement restoration combined with a high flexion.Level of evidenceIV.

Press-Fit Dual-Pivot Total Knee Arthroplasty: Early Results With aMinimum 2-Year Follow-Up.

Ultracongruent (UC) tibial bearings are being used with increasing frequency in the United States. Evidence suggests that the use of certain UC bearings may lead to improved patient satisfaction when compared with using conventional inserts. However, little is known as to what effect the use of UC tibial inserts has on bone ingrowth in uncemented total knee arthroplasty (TKA). The purpose of this study was to determine the early clinical and radiographic results of TKA using a press-fit dual-pivot design. Between 2017 and 2019, a consecutive series of 232 TKAs were implanted using a press-fit tibial and femoral component and a UC dual-pivot tibial insert. Sixty-two percent of patients were male. The average age was 56 years. Patients were followed for a minimum of 2 years (range, 24-42 months) using KOOS-JR and Knee Society clinical and radiographic evaluation. No patient had more than mild knee stiffness at the final follow-up. Two patients reported moderate knee pain with stair climbing. All other patients reported either mild or no pain with activity. Knee Society pain scores averaged 42 points. Flexion averaged 118 degrees. Three knees (1.3%) were revised (one each for flexion instability, tibial plateau fracture, and suspected femoral component loosening). No other cases of femoral or tibial loosening were identified. Although the success of uncemented TKA is determined by a variety of factors, the use of this dual-pivot knee design did not appear to influence tibial or femoral component fixation at early follow-up, yielding acceptable clinical and radiographic outcomes.

Survivorship Comparisons of Ultracongruent, Cruciate-Retaining and Posterior-Stabilized Tibial Inserts Using a Single Knee System Design: Results From the Australian Orthopedic Association National Joint Replacement Registry.

Ultracongruent (UC) tibial inserts can increase knee replacement stability, but how survivorship compares to cruciate retaining (CR) or posterior stabilized (PS) inserts is unclear. Data from a large joint registry were used to calculate the cumulative percent revision of a single popular knee design used with different inserts. There were 67,523 procedures, of which 12,434 were UC, 21,635 CR, and 33,454 PS. Revision rates and reasons for revision were analyzed. The cumulative percent revision at 18 years was 8.3% for UC, 9.2% for CR, and 8.9% for PS. There was no difference when UC was compared to CR, but PS had a higher risk of revision. Revision reasons were similar. Compared to the CR, an UC insert did not increase revision rates and was actually lower than a PS insert. An UC insert does not compromise long-term total knee arthroplasty survivorship in the Genesis II prosthesis.

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.

Early Outcomes of Dual-Pivot Total Knee Replacement Compared to an Ultracongruent Design.

With a quest to optimize outcomes, there have been significant advancements in modern designs of total knee implants, attempting to mimic the natural knee motion and feel. One such new design reproducing the medial and lateral knee pivot is a dual-pivot (DP) knee. In the present study, we endeavored to compare the performance of the DP knee vis-a-vis an ultracongruent (UC) Knee design. This prospective cohort study was performed in a joint replacement center of a tertiary care military hospital. We enrolled 50 patients each in the DP knee group and the UC knee group and assessed knee flexion, patient-reported outcome (new Knee Society Score [nKSS]), patient performance (Delaware Osteoarthritis Profile Score), and function (Forgotten Joint Score [FJS]) at 2 years of follow-up. The nKSS was similar in the two groups. In the DP group, patients had significantly better improvement in the stair climb test (p = 0.026). In the UC group, timed up and go test was significantly better (p = 0.004). The gain in knee flexion was similar in the two groups: 26.3° ± 23.3° in the DP group and 27.5° ± 27.5° in the UC group (p = 0.930). Return to activity as judged by 2-year FJS was similar in both groups (p = 0.687). Our study showed that the DP knee design had similar knee function to the UC knee. The DP knee design had significantly better stair climbing ability, whereas getting up from chair was better in the UC knee design. With comparable patient-reported outcome and possible differences in patient performance in terms of day-to-day activities, any future trial should focus on comparing patient performance.

Early outcomes of ultra-congruent insert in cruciate-retaining total knee arthroplasty: A prospective study

Introduction: The exponents of cruciate-retaining (CR) total knee arthroplasty (TKA) assert that the retention of posterior cruciate ligament (PCL) preserves more normal knee kinematics, femoral rollback on the tibia during flexion, greater stabilization of the prosthesis, and improved position sense as compared to PCL resection TKA. However, one has to shift to the posterior stabilized (PS) femoral component with box and accompanying cam postpolyethylene, especially in cases where PCL is too attenuated to be functional or too tight predisposing to accelerated polyethylene wear. To minimize both the cam mechanism polyethylene wear and the bone sacrifice due to the intercondylar box cut, the ultra-congruent (UC) inserts have been developed that are characterized by a high anterior wall and a deep-dished plate, promising good stability without cam mechanism. Materials and Methods: We did a prospective study to clinically evaluate the short-term results of the patients who underwent TKA using cemented posterior CR implants and UC inserts. PCL was required to be released either partially or completely in all the study patients. Thirty patients were evaluated preoperatively and postoperatively after 12 months with the new Knee Society Knee Scoring System (2011) and the findings were statistically analyzed. Results: There was a statistically significant postoperative improvement in flexion (from mean of 87.69° to 111.53°, P = 0.000), objective knee indicators (33.53 ± 8.51–70.84 ± 4.91, P = 0.000), patient satisfaction scores (7.48 ± 2.12–21.53 ± 4.26, P = 0.000), and the functional activities score (32.53 ± 5.12–69.02 ± 6.36, P = 0.000). We did not note any disadvantage of CR TKA with UC insert and no patient underwent an early revision for instability. Conclusion: Using UC insert in CR TKA is a reliable procedure that has decreased the dependence on the PS designs.

Increased posterior translation but similar clinical outcomes using ultracongruent instead of posterior stabilized total knee arthroplasties in a prospective randomized trial.

The aim of this study was to compare the posterior tibial translation after ultracongruent (UC) and posterior-stabilized (PS) total knee arthroplasty (TKA) with two different UC with different heights in the anterior lip, and two different PS designs. This study also aimed to compare the range of motion (ROM) and outcomes scores after the use of these TKA models. It was hypothesised less posterior tibial translation after PS than after UC TKA, and less posterior tibial translation with a higher anterior lip in the UC insert than with a lower one. It was designed as a prospective randomized study of a group of 120 patients operated with a cemented TKA. To clarify the main purpose of the study, four groups were analysed using different polyethylene designs: Triathlon PS insert in group one, Triathlon UC insert in group two, U2 PS insert in group three and U2 UC insert in group four. One year after surgery, a forced posterior drawer with a Telos Stress applying 15kg of force posteriorly on the proximal tibia at 90° of knee flexion was analysed in the lateral radiograph. Limb alignment, tibial posterior slope and posterior condylar offset were also studied. 30 patients were included in each group. The average age was 73years. There were 72.2% female and 27.8% male patients. There were no significant differences in any demographic or radiographic studied variables, preoperative range of motion (ROM) or preoperative Knee Society Scores (KSS) among the different groups. One year after surgery, the average postoperative ROM and the postoperative KSS Knee and KSS Function scores improved in respect of the preoperative values in all the groups. There were no significant differences in the postoperative outcome scores among the different groups (p = n.s.). Postoperative alignment of the limb, tibial posterior slope and posterior condylar offset were similar in the 4 study groups (p = n.s.). The postoperative posterior tibial translation was different between groups: the PS groups (groups 1 and 3) showed significant inferior values (p < 0.001) in respect of the UC groups (groups 2 and 4). There were no differences between both groups of PS models, but there was a significant increase in the posterior tibial translation of the Triathlon UC insert (11.2mm SD 3.2) in respect of the U2 UC insert (6.1mm SD 4.5) (p = 0.004). UC inserts restrict the posterior tibial translation after TKA less than PS inserts, but a design with a high anterior lip in the polyethylene UC insert can better control the posterior tibial translation than an insert with a small anterior lip. Level I. Randomised controlled trial.

In vivo kinematic comparison between an ultra-congruent and a posterior-stabilized total knee arthroplasty design by RSA.

The aim of the present study was to compare the in vivo under weight-bearing kinematic behavior of a posterior-stabilized (PS) and an ultra-congruent (UC) total knee arthroplasty (TKA) model during a sit-to-stand motor task, a common activity of daily life. A cohort of 16 randomly selected patients (8 PS Persona Zimmer, 8 UC Persona Zimmer) was evaluated through dynamic radiostereometric analysis (RSA) at a minimum of 9months after TKA, during the execution of a sit-to-stand. The anteroposterior (AP) translation of the femoral component and the AP translation of the low point of medial and lateral femoral compartments were compared through Student's t test (p < 0.05). A significantly greater anterior translation of the femoral component was found for the PS group compared to the UC group. The flexion interval where statistical significance was found was between 30° and 0° (p = 0.017). Both groups showed a significantly greater anterior translation of the low point of the lateral compartment with respect to the medial one (PS: p = 0.012, UC: p = 0.018). This was consistent with a medial-pivot pattern. Furthermore, a significantly greater anterior translation of the medial compartment was found in the PS group compared to the UC group (p = 0.001). The same pattern was observed for the lateral compartment (p = 0.006). The TKA designs evaluated in the present study showed comparable in-vivo kinematics with regards to medial pivot pattern but differences in absolute AP translation. Specifically, the UC design showed greater AP stability than the PS design. This finding could be positive in terms of implant stability, but negative in terms of premature polyethylene wear and thus implant failure. This remains to be verified in studies with a larger sample size and longer follow-up. IV.