Ultracongruent Total Knee Arthroplasty Research Articles

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.

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.

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.

Different intraoperative kinematics, stability, and range of motion between cruciate-substituting ultracongruent and posterior-stabilized total knee arthroplasty.

The aim of this study was the comparison of intraoperative kinematics, stability, and range of motion (ROM) between the native osteoarthritic knee and cruciate-substituting fixed-bearing total knee arthroplasty (TKA) using both an ultracongruent (UC) and a posterior-stabilized (PS) insert design in the same patient. We hypothesized less knee flexion and less antero-posterior stability in the UC TKA. Intraoperative measurements of kinematics, stability, and ROM were performed in 40 patients before soft-tissue release and bone cuts, and after implantation of the final femoral and tibial implants with both a UC insert and a PS insert. All measurements were performed using a navigation system. Kinematics changed significantly from a constant posterior femoral rollback before surgery to a paradoxical anterior translation during initial knee flexion with both inserts, but less pronounced with the PS insert (p < 0.001). There was significantly more posterior femoral rollback with the PS insert compared to the UC insert (p < 0.01). Stability measurements demonstrated no differences at full extension and 30° of knee flexion but significantly increased antero-posterior translation in 60° and 90° of knee flexion with the UC insert compared to the PS insert (p < 0.001). ROM measurements demonstrated improvement of knee flexion from 118° at the beginning of the surgery to 123° with the UC insert and 128° with the PS insert (p < 0.001). The use of a UC insert intraoperatively resulted in less antero-posterior stability and slightly less knee flexion compared to a PS insert. Surgeons should be aware of these differences when deciding for one of these options to substitute the posterior cruciate ligament (PCL). The impact of these findings on clinical outcome needs further investigation. II.

No difference in range of motion between ultracongruent and posterior stabilized design in total knee arthroplasty: a randomized controlled trial.

The use of an ultracongruent (UC) insert with a standard femoral component for substitution of the posterior cruciate ligament (PCL) is a bone-preserving and therefore interesting alternative to the established box and cam mechanism of posterior stabilized (PS) total knee arthroplasty (TKA). This study investigated range of motion (ROM), stability and patient-reported outcome (PRO) in UC and PS TKA. We hypothesized better knee flexion with the PS design but no difference in stability and PRO between UC and PS TKA. A randomized controlled study was performed. One hundred and twenty-seven patients were included, 63 with an UC and 64 with a PS TKA (Columbus, Aesculap, Tuttlingen, Germany). Intraoperative stability and range of motion was measured with the use of a navigation system. Patients were assessed before surgery, 3months and 1year postoperatively. There was no difference in ROM between both groups, neither intraoperatively nor at follow-up. There was 5mm less sagittal translation at 90° of knee flexion (p<0.001) and more posterior femoral rollback during knee flexion in the PS TKA. Axial rotation between extension and knee flexion was reduced by both designs. UC TKA was 7min faster (p=0.001). At the one-year follow-up, the Knee Society Score was similar in both groups, the Oxford Knee Score demonstrated better results in the UC TKA group (p=0.048). Increased intraoperative sagittal translation and reduced posterior femoral rollback during knee flexion of UC TKA seem to have no negative influence on short-term clinical outcome. Therefore, UC TKA seems to be a practical alternative to the established PS TKA for substitution of the PCL. This might be especially interesting for surgeons who do not always substitute the PCL. I.

Different intraoperative kinematics with comparable clinical outcomes of ultracongruent and posterior stabilized mobile-bearing total knee arthroplasty.

There remains no consensus as to whether mobile total knee arthroplasty (TKA) should use a posterior cruciate ligament-sacrificing ultracongruent (UC) or a posterior cruciate ligament-substituting posterior stabilized (PS) prosthesis. The purpose of this study was to assess intraoperative kinematics and clinical outcomes of UC and PS rotating platform mobile-bearing TKA. In this randomized controlled study, mobile UC TKA prostheses (n=45) were compared with mobile PS TKA prostheses (n=45) with regard to intraoperative kinematics and clinical outcomes. The passive kinematic study using intraoperative navigation system included anterior/posterior translation, varus/valgus alignment and rotation of femur during flexion. The patients were clinically and radiographically evaluated over a 3-year follow-up. Paradoxical anterior translation of the femur was 10.8±5.2mm in the UC knee from 0° to 82° of knee flexion and 8.7±3.0mm in the PS knee from 0° to 70° of knee flexion (p=0.027). Paradoxical internal rotation of the femur was 5.8° in the UC knees and 9.9° in the PS knees (p=0.003). But, there was no significant difference between the groups in regard to the coronal alignment. There was no significant difference in the range of motion, KS knee scores, KS function scores, and WOMAC index scores. Despite different intraoperative kinematics between mobile UC and mobile PS TKA, neither design reproduced physiologic knee kinematics and there was no difference in clinical outcomes between the two groups. The clinical relevance of the study is that despite different intraoperative kinematics, UC design can be a considerable alternative to PS design in mobile-bearing TKA in respect of clinical outcomes. II.

Similar stability and range of motion between cruciate-retaining and cruciate-substituting ultracongruent insert total knee arthroplasty

The use of an ultracongruent (UC) insert with a standard femoral component for substitution of the posterior cruciate ligament (PCL) is a bone-preserving and therefore interesting alternative to the established box and cam mechanism of posterior-stabilized total knee arthroplasty (TKA). Despite the regular use of these UC inserts, there is little evidence about stability and range of motion (ROM). The aim of this study was to evaluate the stability and ROM in standard cruciate-retaining (CR) and cruciate-substituting UC inserts of the same TKA. In 39 patients, intraoperative measurements of stability and ROM were taken (1) before soft tissue release and bone cuts, (2) after implantation of a CR TKA and (3) after resection of the PCL and substitution with an UC insert. All measurements were taken using a navigation system. Stability measurements demonstrated no differences between CR (PCL intact) and UC TKA (PCL resected), but significantly increased anteroposterior translation at 60° and 90° of knee flexion compared with the preoperative condition. ROM measurements demonstrated improvement of knee flexion from preoperatively mean 105° (SD 14.1°) to intraoperative 120.2° (SD 6.7°) with the CR and 121.0° (SD 7.5°) with the UC insert and 113.5° (SD 14.0°) at the 1-year follow-up. This study demonstrates similar stability of an UC insert compared with a standard CR insert. UC inserts are therefore a bone-preserving solution if the PCL needs to be substituted. ROM was not improved after resection of the PCL and substitution with the UC insert. II.

Paper # 224: The Effect of PCL on Kinematic and Clinical Results of Ultracongruent Mobile TKA

The PCL-preserving ultracongruent mobile TKA showed more potentially vulnerable intraoperative kinematics and two serious complications, compared with the PCL-sacrificing TKA. There is a concern that patients who have undergone posterior cruciate ligament(PCL)-preserving ultracongruent mobile total knee arthroplasty(TKA) that does not have a cam and post mechanism can improve the kinematics, stability and clinical outcome, compared with PCL-sacrificing TKA. We aimed to evaluate the effect of PCL on kinematics and clinical results of UC mobile TKA. Ninety knees with primary osteoarthritis were randomly allocated to Group P(PCL-preserving UC RP TKA) or Group S(PCL-sacrificing UC RP TKA). Passive intraoperative kinematics was recorded by navigation system immediately after implantation. Three parameters of tibiofemoral relationship(anterior/posterior translation, varus/valgus rotation, internal/external rotation) were analyzed in both groups from 10° to 120° of flexion. The range of motion, functional scores, radiographic results and complications were also evaluated. The minimally follow up period was 2 years postoperatively. There were significant differences in the varus/valgus rotation and anterior/posterior translation of the femur. Group P(42knees) had more varus rotation over 90° flexion(p<0.05) and more anterior translation of the femur in all range of flexion(p<0.05) than group S(44knees). There was no difference in internal/external rotation of the femur(p>0.05). The range of motion was not different at final follow up(125° vs 120°, p=0.178). Functional scores and radiographic results were not different between two groups. Two knees in Group P were revised: one presented with posterior instability by attenuated PCL at 7 weeks after surgery and treated with exchange into thicker insert; the other with insert subluxation over 120° flexion at 1 week treated with resection of tight PCL and thicker insert. PCL-preserving ultracongruent mobile TKA showed not only the significant deviation in kinematics including anterior translation of the femur and varus rotation but also unpredictable complications including instability and subluxation, compared with PCL-sacrificing ultracongruent mobile TKA. It is recommended to remove PCL and get well balanced gap and stability independent of PCL at initial surgery in ultracongruent TKA.