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Purpose: 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., Methods: 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 9 months 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)., Results: 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)., Conclusions: 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., Level of Evidence: IV., (© 2021. European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA).)

Purpose: The purpose of this study was to compare two types of posterior-stabilized (PS) mobile-bearing (MB) total knee arthroplasties (TKAs). The hypothesis was that no major differences were going to be found among the two TKA designs., Methods: Two cohorts of patients who were divided according to implant design (Cohort A, new design gradually reducing radius PS MB TKA; Cohort B, traditional dual-radius PS MB TKA) were analyzed by means of intraoperative navigation. All operations were guided by a non-image-based navigation system that recorded relative femoral and tibial positions in native and implanted knees during the following kinematic tests: passive range of motion (PROM), varus-valgus stress test at 0° and 30° (VV0, VV30) and anterior/posterior drawer test at 90° of flexion (AP90)., Results: There were no significative differences in kinematic tests between the two implants. Cohort A, however, showed a different post-implant trend for VV0 and VV30 that were lower than the pre-implant ones, as expected, while for Cohort B, the trend is opposite. However, the gradually reducing radius prosthesis (Cohort A) showed a trend of improving stability (29% compared to the preoperative status) in mid-flexion (VV30) which the traditional dual-radius design (Cohort B) would not. Moreover, we found no differences among postoperative results of the two TKA designs., Conclusion: Despite design variations, no difference has been found among the prostheses in terms of PROM, rotations and translations. Both design kinematics did not show paradoxical external rotations, but an increase in femoral translation in mid-flexion without affecting the functioning of the prosthesis., Level of Evidence: II., (© 2020. Istituto Ortopedico Rizzoli.)

Purpose: To evaluate if there was a correlation between in vivo kinematics of a medial-stabilized (MS) total knee arthroplasty (TKA) and post-operative clinical scores. We hypothesized that (1) a MS-TKA would produce a medial pivot movement and that (2) this specific pattern would be correlated with higher clinical scores., Methods: 18 patients were evaluated through clinical and functional scores evaluation (Knee Society Score clinical and functional, Womac, Oxford), and kinematically through dynamic radiostereometric analysis (RSA) at 9 months after MS-TKA, during the execution of a sit-to-stand and a lunge motor task. The anteroposterior (AP) Low Point translation of medial and lateral femoral compartments was compared through Student's t test (p < 0.05). A correlation analysis between scores and kinematics was performed through the Pearson's correlation coefficient r., Results: A significantly greater (p < 0.0001) anterior translation of the lateral compartment with respect to the medial one was found in both sit-to-stand (medial 2.9 mm ± 0.7 mm, lateral 7.1 mm ± 0.6 mm) and lunge (medial 5.3 mm ± 0.9 mm, lateral 10.9 mm ± 0.7 mm) motor tasks, thus resulting in a medial pivot pattern in about 70% of patients. Significant positive correlation in sit-to-stand was found between the peak of AP translation in the lateral compartment and clinical scores (r = 0.59 for Knee Society Score clinical and r = 0.61 for Oxford). Moreover, we found that the higher peak of AP translation of the medial compartment correlated with lower clinical scores (r = - 0.55 for Knee Society Score clinical, r = - 0.61 for Womac and r = - 0.53 for Oxford) in the lunge. A negative correlation was found between Knee Society Score clinical and VV laxity during sit-to-stand (r = - 0.56) and peak of external rotation in the lunge motor task (r = - 0.66)., Conclusions: The MS-TKA investigated produced in vivo a medial pivot movement in about 70% of patients in both examined motor tasks. There was a correlation between the presence of medial pivot and higher post-operative scores., Level of Evidence: IV.

Purpose: The purpose of the present study was to assess the kinematical behavior of a multi-radius posterior-stabilized (PS) mobile-bearing (MB) total knee arthroplasty (TKA) during an activity of daily living (Sit-To-Stand-STS) and a high demanding motor task (Deep-Knee-Lunge-DKL) using model-based dynamic RSA. We hypothesized the achievement of medial pivoting movement in both motor tasks due to the congruent geometry of the inlay with the femoral component, which should allow good stability of the medial compartment, and to the high magnitude of rotations guaranteed by the MB on the tibial side., Methods: Twenty-two randomly selected patients were recruited and prospectively evaluated. The PS MB cemented TKA was implanted with the standard technique (medial parapatellar approach, adjusted mechanical alignment). At minimum 9-month follow-up, patients were examined with model based Dynamic RSA developed in our Institute (BI-STAND DRX 2) during the execution of two motor tasks: STS and DKL. The motion parameters were evaluated using the Grood and Suntay decomposition and the low-point kinematics methods., Results: In the extension phase of DKL femur performed a greater antero posterior translation of 3.8 mm compared to STS between 0° and 20° of knee flexion (p < 0.05). Low-point analysis showed a medial pivoting movement in both motor tasks: in 62% of patients during STS and 48% during DKL. Varus-valgus rotations were lower than 1° during all the range-of-motion in both motor tasks without differences., Conclusions: Medial pivot was partially produced by this multi-radius PS MB TKA with some differences during activity of daily living (STS) and high demanding motor task (DKL)., Level of Evidence: IV.

Purpose: Which total knee arthroplasty (TKA) design represents the better solution to restore a correct knee biomechanics is still debated. The aim of this study was to compare posterior stabilized (PS) and cruciate retaining (CR) version of the same TKA design (femoral component with an anatomic sagittal radius-J-curve design) by the use of dynamic Roentgen stereophotogrammetric analysis (RSA). The hypothesis was that the two models influence differently in vivo knee kinematic., Methods: A cohort of 16 randomly selected patients was evaluated 9 months after surgery: Zimmer PERSONA® was implanted, eight with CR design and eight with PS design. The kinematic evaluations were performed using a Dynamic RSA (BI-STAND DRX 2) developed in our Institute, during the execution of the sit-to-stand motor task. The motion parameters were obtained using the Grood and Suntay decomposition and the low-point kinematics methods., Results: PS TKA lateral femoral compartment had a wider anterior translation (17 ± 2 mm) than the medial one (11 ± 2 mm), while the two compartments of CR TKA showed a similar anterior translation (medial: 9 ± 2 mm/lateral: 11 ± 2 mm). T test for comparison between CR and PS TKA of antero-posterior translation showed a statistically significant difference (p < 0.05) in the flexion range between 15° and 40°. The CR prosthesis did not anteriorly translate during flexion. The PS design translated anteriorly showing a roll-forward mechanism during extension from 80° to 18° of flexion and a posterior translation from 18° to 0°. The same significant differences (p < 0.05) between the PS and CR groups were found comparing the low-point positions of the femoral condyles in the range of flexion between 25° and 40° for the medial compartment and between 15° and 25° for the lateral compartment., Conclusions: Dynamic RSA was able to investigate for the first time in vivo the kinematic behaviour of PS and CR version of the same TKA J-curve design. PS type showed a medial pivot during sit-to-stand motion task, while the CR type showed a cylindrical movement. Further studies are needed to evaluate the impact of different TKA designs on clinical results., Level of Evidence: IV.

Purpose: This work presents a kinematic evaluation of a cruciate retaining highly congruent mobile bearing total knee arthroplasty design using dynamic Roentgen sterephotogrammetric analysis. The aim was to understand the effect of this implant design on the kinematics of prosthetic knees during dynamic activities., Methods: A cohort of 15 patients was evaluated at nine month follow-up after surgery. The mean age was 74.8 (range 66-85) years. The kinematics was evaluated using the Grood and Suntay decomposition and the Low-Point (LP) methods., Results: ?tlsb=-0.15pt?>From sitting to standing up position, the femoral component internally rotated (from -11.3 ± 0.2° to -7.0 ± 0.2°). Varus-valgus rotations were very close to 0° during the whole motor task. LP of medial condyle moved from an anterior position of 12.0 ± 0.2 mm to a posterior position of -12.4 ± 0.2 mm; LP of the lateral condyle moved from an anterior position of 8.1 ± 0.2 mm to a posterior position of -12.4 ± 0.2 mm, showing a bi-condylar rollback where both condyles moved parallel backward. Moreover, the femoral component showed anterior translation with respect to the tibia from 80° to 20° (from -4.9 ± 0.2 mm to 3.3 ± 0.2 mm), then a posterior translation from 20° to full extension was identified (from 3.3 ± 0.2 mm to 0.5 ± 0.2 mm)., Conclusions: Paradoxical anterior femoral translation and absence of medial-pivoting motion were recorded, highlighting the role of the symmetric deep dishes insert as main driver of the kinematic of this TKA design., Competing Interests: Declaration of competing interest The authors declare that they have no competing interests., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Purpose: To assess, using model-based dynamic radiostereometric analysis (RSA), the biomechanical behaviour of a new design posterior-stabilized (PS) fixed-bearing (FB) total knee arthroplasty (TKA) in vivo while patients performing two common motor tasks. The hypothesis was that model-based dynamic RSA is able to detect different behaviour of the implant under weight-bearing and non-weight-bearing conditions., Methods: A cohort of 15 non-consecutive patients was evaluated by dynamic RSA 9 months after TKA implantation. The mean age of patients was 73.4 (65-72) years. The kinematic evaluations were performed using an RSA device (BI-STAND DRX 2) developed in our Institute. The patients were asked to perform two active motor tasks: sit-to-stand in weight-bearing condition; range of motion (ROM) while sitting on the chair. The motion parameters were evaluated using the Grood and Suntay decomposition and the low-point kinematics methods., Results: The dynamic RSA evaluation showed a significant difference (p < 0.05) between the biomechanical behaviour of the prosthesis during the two motor tasks. When subjected to the patient weight (in the sit-to-stand) the low point of the medial compartment had a shorter motion (5.7 ± 0.2 mm) than the lateral (11.0 ± 0.2 mm). This realizes a medial pivot motion as in the normal knee. In the ROM task, where the patient had no weight on the prosthesis, this difference was not present: the medial compartment had a displacement of 12.7 ± 0.2 mm, while the lateral had 17.3 ± 0.2 mm., Conclusions: Model-based RSA proved to be an effective tool for the evaluation of TKA biomechanics. In particular, it was able to determine that the fixed-bearing posterior-stabilized TKA design evaluated in this study showed a medial pivoting movement under weight-bearing conditions that was not present when load was not applied. Under loading conditions what drives the pattern of movement is the prosthetic design itself. By the systematic use of this study protocol future comparisons among different implants could be performed, thus contributing significantly to the improvement of TKA design., Level of Evidence: IV.

Purpose: The purpose of this randomized double-blind study was to investigate the effectiveness of the Videoinsight ® psychological enhancing method in promoting early recovery during rehabilitation following total knee arthroplasty., Methods: One-hundred and ten patients treated with cemented total knee arthroplasty were randomly assigned to Group A or Group B, and both groups underwent the same rehabilitation programme. Group A (55 patients) received one art video selected according to Videoinsight ® concept. This art video promoting self-confidence and psychological support to the patient has been shown in the physical therapy department before any rehabilitation session, in the first 15 days after surgery and then three times a week for the next 4 weeks. Group B (55 patients) underwent the same rehabilitation protocol in the same setting, after TKA surgery, without the video support. Patients were evaluated pre-operatively and 3 months after surgery with Physical and Mental SF-36, State-Trait Anxiety Inventory (STAI), Beck Depression Inventory (BDI), Tampa Scale of Kinesiophobia (TSK), Knee Society Score (KSS), VAS, and WOMAC scores., Results: Eight patients were lost to follow-up, and 102 patients (Group A: 52 patients; Group B: 50 patients) were available at mean 3.0 ± 0.2 months follow-up. Age at surgery was 69.1 ± 13.0 years. The two groups were homogeneous regarding pre-operative demographic data and clinical outcomes. Significant improvements were observed in both groups compared to baseline and in Group A compared to Group B at final follow-up for functional and psychological scores except for SF-36. Respectively, Group A and Group B showed WOMAC 79.9 ± 13.0 and 69.7 ± 9.5 (p < 0.005), VAS 2.8 ± 1.6 and 4.0 ± 1.5, (p < 0.005), KSS 87.8 ± 9.6 and 78.3 ± 8.2 (p < 0.005), BDI 5.1 ± 4.8 and 9.4 ± 3.9 (p < 0.005), STAI 30.8 ± 7.9 and 34.8 ± 7.8 (p < 0.005), and TSK 24.4 ± 5.5 and 29.3 ± 4.8 (p < 0.005)., Conclusion: The Videoinsight( ® ) psychological enhancing method, by the view of video art images, combined to an adequate rehabilitation protocol can be a means for further improving short-term clinical and functional outcomes by giving a psychological support to patients who underwent total knee arthroplasty., Level of Evidence: I.