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In the vast majority of cases total knee arthroplasty is efficient for pain relief and improving the joint function. However, there is still a subset of patients who are not satisfied with their replacement surgery. Reasons cited include persistent pain, restricted movement, an unnatural feeling of the knee and complaints of instability. Additionally, active patients sometimes report limitations in performing high-level activities. Traditional designs of total knee prostheses cannot fully replicate the physiological kinematics of the knee joint. Medial pivot systems aim to reproduce the physiological biomechanics of the knee joint. Medially, they resemble, similar to a natural and healthy knee, a ball fitting into a highly congruent socket, ensuring stability in all planes and allowing for a constant ligament tension on the medial side. Externally, these implants are less congruent, permitting the natural rotational movement of the knee joint. The combination of natural, uncompromised knee mobility and high stability is intended to reproduce a physiological biomechanic of knee joint. This is the basis for good knee function in daily activities and sports. In Germany, these treatment concepts are used relatively infrequently compared to other countries, although their use has increased significantly. This review article aims to provide insight into these concepts, which are still relatively unknown in Germany. [ABSTRACT FROM AUTHOR]

PURPOSE: In total knee arthroplasty (TKA) with posterior cruciate ligament (PCL) retention, the medial and lateral insert conformity that restores in vivo native (i.e., healthy) knee tibial rotation and high function without causing stiffness is unknown. The purpose was to determine whether a ball-in-socket (B-in-S) medially conforming (MC) and flat lateral insert implanted with unrestricted kinematic alignment (KA) TKA and PCL retention restores tibial rotation to native. METHODS: One group of 25 patients underwent unrestricted KA TKA with manual instruments. Another group of 25 patients had native knees. Single-plane fluoroscopy imaged each knee while patients performed step-up and chair rise activities. Following 3D model-to-2D image registration, anterior-posterior (A-P) positions of the femoral condyles were determined. Changes in A-P positions with flexion were used to determine tibial rotation. RESULTS: At maximum flexion, mean tibial rotations of KA TKA knees were comparable to native knees (Step up: 12.3° ± 4.4° vs. 13.1° ± 12.0°, p = 0.783; Chair Rise: 12.7° ± 6.2° vs. 12.6° ± 9.5º, p = 0.941). However, paths of rotation differed in that screw home motion was less evident in KA TKA knees. At 8 months follow-up, the median Forgotten Joint Score was 69 points (range 65 to 85), the median Oxford Knee Score was 43 points (range 40 to 46), and mean knee flexion was 127º ± 8°. CONCLUSIONS: The ball-in-socket medial, flat lateral insert and PCL retention implanted with unrestricted KA TKA restored in vivo native knee tibial rotation at maximum flexion for each activity and high function without stiffness. Providing high A-P stability, this implant design might benefit patients desiring to return to demanding work and recreational activities. LEVEL OF EVIDENCE: Therapeutic - Level II.

Background: This study aimed to evaluate post-operative lower limb function following second-generation mechanically aligned medial pivot (MP) TKA implantation. Standard gait analysis was performed to collect kinematic and kinetic data, which were then compared with physiological data from the literature obtained using the same evaluation methodology as the present study. The hypothesis was that this TKA would not fully restore normal knee and adjacent joint motion during walking. Methods: Our cohort comprised 15 patients consecutively enrolled from September 2019 to December 2022 who underwent primary TKA with the second-generation MP Evolution Knee System (MicroPort Orthopaedics Inc., Arlington, TN, USA). Pre-operatively and 6 months post-surgery, gait analysis during level walking was performed on all patients, as well as clinical evaluations using the Knee Society Score (KSS), the Knee Injury and Osteoarthritis Outcome Score (KOOS), and the Visual Analogue Scale (VAS). Results: The clinical scores improved significantly (p < 0.001) after surgery (pre-/post-operative KSS functional, KSS clinical, VAS, and KOOS: 51.7 ± 17.3/84 ± 18.4, 45.3 ± 16.2/74.1 ± 12.6, 6.9 ± 1.8/2.0 ± 1.9, and 33.9 ± 11.8/69.1 ± 16.5, respectively). The statistical parametric mapping (SPM) analysis between the post-operative and reference control data revealed significant differences in the initial and final 20% of the gait cycle for the rotation of the knee in the frontal and transverse planes and for the rotation of the ankle in the sagittal plane. Conclusions: This study shows that new-generation MP TKA with mechanical alignment does not fully restore normal gait biomechanics, particularly in knee rotational movements, indicating a need for improved surgical techniques and prosthetic designs. [ABSTRACT FROM AUTHOR]

Background: Unrestricted kinematic alignment (uKA) in total knee arthroplasty (TKA) has the theoretical advantage of reproducing patients' constitutional alignment and restoring the pre-arthritic joint line position and obliquity. However, modifications of the original uKA technique have been proposed due to the potential risk of mechanical failure and instability. Given the significant variability in soft tissue behavior within the same bony morphology group, uKA pure knee resurfacing could be occasionally detrimental. This study aimed to kinematically compare the outcomes of uKA TKA with those of a robotic-assisted KA TKA technique based on specific soft-tissue boundaries. Methods: In this retrospective gait analysis study, 24 TKA patients and 12 healthy controls were recruited. Inclusion criteria were a 9-month minimum follow-up from successfully, primary medial-pivot or medially-congruent TKA performed for isolated degenerative joint disease. Preoperatively, patients were randomly assigned to two surgical groups: A) uKA (#12) and B) robot-assisted (#12), KA (hybrid-kinematic) with boundaries (±3° from hip-knee-ankle neutral axis) and a slight intercompartmental gap asymmetry (max 2 mm lateral-opening). The gait analysis was performed using instrumented treadmills equipped with 3D cameras. Results: Sagittal knee kinematic data: during the early-stance phase of gait, the uKA group showed a less consistent weight-acceptance phase and a less efficient transition between the first knee-flexion peak and mid-stance-extension plateau with respect to the hybrid-kinematic alignment group. Spatiotemporal and overall gait quality data: no significant differences were found between the two TKA groups regarding walking speed (P = .51) and step length (P = .8534). Control group patients walked more efficiently compared to TKA groups, showing inferior trunk flexion and inferior variation in step length (P < .0001). Conclusions: This study showed that restoring the pre-arthritic joint line, as advocated by surgeons following the uKA philosophy, does not guarantee a closer-to-normal knee kinematics.

Abstract Purpose The purpose of this study was to demonstrate closer-to-normal knee kinematics following primary total knee arthroplasty (TKA) performed establishing asymmetric gap balancing intraoperatively. Material and method Two age-, sex-, BMI-matched groups of patients underwent medially stabilized TKA because of isolated knee disease. Group A (12 patients) underwent “unrestricted” kinematic alignment (uKA) according to Howell while group B (15 patients) received robot-assisted “simplified” KA (sKA) with an alignment goal (Hip-Knee-Ankle axis-HKA) ± 5° respect to the mechanical axis. Intraoperatively, in group B, the flexion gap at 90° was first set at an average of 1.5 mm (0–5 mm; SD 4.4 mm) tighter in the medial compartment with respect to the lateral; in the same way, the extension gap was then set at an average of 2.0 mm (0–4.5 mm; SD 3.1 mm) tighter in the medial compartment with respect to the lateral. All patients, including a non-arthritic cohort (group C: 5 controls) underwent gait analysis using an instrumented treadmill (WalkerView–WV) equipped with an instrumented belt armed with a 3D video camera. The WV software evaluated multiple spatiotemporal and kinematic parameters, including: (1) contact time (s); (2) knee ROM during gait cycle; (3) step length percentage with respect to total gait (%) and pure step length (cm). Statistical analyses included t-Test and ANOVA and were conducted by using SPSS. Results At the final FU, significant differences were noted during gait between the two TKA groups (uKA-sKA) and the controls. Both TKA groups showed superior mean contact time on the surgical knee (uKA 1 s; sKA 0.97 s) as compared to the controls (0.72 s) (P = 0.002) while no differences were found between them (P = 0.11). TKA groups showed a lower, maximum ROM in the surgical knee (mean uKA 36º; mean sKA 49º) relative to the controls (mean 57º) (P

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to demonstrate closer-to-normal knee kinematics following primary total knee arthroplasty (TKA) performed establishing asymmetric gap balancing intraoperatively. Material and method: Two age-, sex-, BMI-matched groups of patients underwent medially stabilized TKA because of isolated knee disease. Group A (12 patients) underwent "unrestricted" kinematic alignment (uKA) according to Howell while group B (15 patients) received robot-assisted "simplified" KA (sKA) with an alignment goal (Hip-Knee-Ankle axis-HKA) ± 5° respect to the mechanical axis. Intraoperatively, in group B, the flexion gap at 90° was first set at an average of 1.5 mm (0–5 mm; SD 4.4 mm) tighter in the medial compartment with respect to the lateral; in the same way, the extension gap was then set at an average of 2.0 mm (0–4.5 mm; SD 3.1 mm) tighter in the medial compartment with respect to the lateral. All patients, including a non-arthritic cohort (group C: 5 controls) underwent gait analysis using an instrumented treadmill (WalkerView–WV) equipped with an instrumented belt armed with a 3D video camera. The WV software evaluated multiple spatiotemporal and kinematic parameters, including: (1) contact time (s); (2) knee ROM during gait cycle; (3) step length percentage with respect to total gait (%) and pure step length (cm). Statistical analyses included t-Test and ANOVA and were conducted by using SPSS. Results: At the final FU, significant differences were noted during gait between the two TKA groups (uKA-sKA) and the controls. Both TKA groups showed superior mean contact time on the surgical knee (uKA 1 s; sKA 0.97 s) as compared to the controls (0.72 s) (P = 0.002) while no differences were found between them (P = 0.11). TKA groups showed a lower, maximum ROM in the surgical knee (mean uKA 36º; mean sKA 49º) relative to the controls (mean 57º) (P < 0.05) but a statistical difference was found between them (P = 0.003). Both TKA groups showed a higher step length percentage with respect to the total gait and a shorter step length on the surgical side (uKA: mean 8.28% and mean step length 35.5 cm; sKA: mean 8.38% and mean step length 34.6 cm) in comparison to the controls (mean 3.38%; mean step length 71.4 cm) (P < 0.05) while no statistical differences were found between them. Conclusion: To our knowledge, this was the first study to exhibit the kinematic advantages of a slightly asymmetric gap balancing during KA TKA. Combining a medially-stabilized implant design and a surgical technique aiming to obtain a tighter medial compartment represents a promising approach to improve outcomes after TKA. [ABSTRACT FROM AUTHOR]

Purpose: To clarify differences in surgery duration, postoperative knee range of motion (ROM), anterior and posterior (AP) laxity, and Forgotten Joint Score (FJS) in patients undergoing medial‐pivot (MP) and GRADIUS cruciate‐retaining (CR) total knee arthroplasty (TKA) surgeries. Methods: We examined patients who underwent either MP or CR TKA at six different Japanese centres. Patients were propensity score matched for age, sex, and preoperative hip‐knee angle (HKA). We compared the groups' average surgery duration, postoperative knee ROM, AP laxity, and FJS 1 year after surgery. Results: There were 86 study patients: 43 MP and 43 CR TKA matched for age, sex, and preoperative HKA. The MP group enjoyed a significantly shorter surgery duration (89.1 ± 10.9 mins vs. 95.7 ± 12.0 mins, p = 0.0091) and significantly better postoperative knee flexion than the CR group (123.7 ± 9.1° vs. 115.3 ± 12.4°, p < 0.001). The MP had significantly smaller postoperative AP laxity with 30° of knee flexion than the CR group (3.4 ± 1.3 vs. 5.6 ± 2.2 mm, p < 0.001). Conversely, postoperative AP laxity with 90° of knee flexion was significantly larger for the MP group (3.6 ± 1.3 vs. 2.7 ± 1.9 mm, p = 0.0098). There were no between‐group differences in postoperative FJS. Conclusions: The MP group showed better postoperative knee flexion, midrange AP knee stability, and shorter surgery duration. Level of Evidence: Level III, retrospective comparative study. [ABSTRACT FROM AUTHOR]

The number of performed total knee arthroplasty (TKA) operations is constantly growing. This study proposes an evaluation of a series of patients undergoing medial pivot (MP) TKA surgery from a subjective, clinical and biomechanical point of view. A consecutive series of 100 TKAs implanted in a single centre, by the same surgeon, with a medial parapatellar approach with the sacrifice of the posterior cruciate ligament and cemented components were evaluated. All patients underwent standardized radiographic and functional clinical evaluation, with standing antero-posterior, lateral and patellar axial views; pre-operatively and post-operatively at 1, 3, 6 and 12 months; and then annually. Results were evaluated using three different patient-related outcome measurement scores (PROMs): the Knee Osteoarthritis Outcome Score (KOOS), the new Knee Society Score (nKSS) and the Short Form Health Survey 36 (SF-36). Excellent results in all treated knees were documented using the PROMs: the mean nKSS was 199.8, the mean KOOS was good to excellent in every subscale, and the mean was SF-36 82%. There were no cases of septic or aseptic loosening, vascular damage, neurological damage, or revision surgery for any reason. According to the experience gained, MP implants demonstrated excellent results, being clinically functional in both objective and subjective terms as well as radiographic evaluations, thus resulting in a winning strategy for obtaining a TKA that makes the patient satisfied and able to perform their daily life activities.

Total knee arthroplasty (TKA) is a popular treatment for end-stage knee osteoarthritis. Advances in understanding knee biomechanics have led to the development of medial pivot (MP) prostheses, which aim to replicate natural knee kinematics. While short- and mid-term studies have shown favorable outcomes for MP-TKA, long-term follow-up studies are limited. This systematic review aims to analyze the available evidence on long-term outcomes of MP-TKA, including survivorship, complications, and patient-reported outcome measures (PROMs). A comprehensive search was conducted in PubMed, Embase, and Cochrane Database of Systematic Reviews for English language studies reporting long-term outcomes of primary MP-TKA. Nine studies with an average follow-up of 12.4 years were included. Data on survivorship, complications, and PROMs were collected and analyzed. The overall survivorship of MP-TKA was 98.2% at an average follow-up of 12.4 years. Aseptic loosening and periprosthetic joint infection (PJI) were the most common reasons for revision, with a revision rate of 0.4% for each. The overall complication rate was 6.6%, with secondary anterior knee pain and PJI being the most frequent complications. The reoperation rate was 3.1%, primarily due to PJI and knee instability. PROMs significantly improved postoperatively. MP-TKA demonstrates favorable long-term outcomes with high survivorship, low complication rates, and enhanced PROMs. The procedure provides reliable management for end-stage osteoarthritis, offering patients improved knee function and pain relief. Further research with standardized reporting and larger sample sizes is needed to validate and compare these findings to other implant designs.

Abstract Purpose To clarify differences in surgery duration, postoperative knee range of motion (ROM), anterior and posterior (AP) laxity, and Forgotten Joint Score (FJS) in patients undergoing medial‐pivot (MP) and GRADIUS cruciate‐retaining (CR) total knee arthroplasty (TKA) surgeries. Methods We examined patients who underwent either MP or CR TKA at six different Japanese centres. Patients were propensity score matched for age, sex, and preoperative hip‐knee angle (HKA). We compared the groups' average surgery duration, postoperative knee ROM, AP laxity, and FJS 1 year after surgery. Results There were 86 study patients: 43 MP and 43 CR TKA matched for age, sex, and preoperative HKA. The MP group enjoyed a significantly shorter surgery duration (89.1 ± 10.9 mins vs. 95.7 ± 12.0 mins, p = 0.0091) and significantly better postoperative knee flexion than the CR group (123.7 ± 9.1° vs. 115.3 ± 12.4°, p

Background: Kinematic alignment (KA) restores native limb alignment following total knee arthroplasty (TKA). The association of this technique with a medial pivot implant design attempts to re-establish the physiological kinematics of the knee. This study aims to analyze the clinical and radiological outcomes of patients undergoing MP-TKA with kinematic alignment and to assess the effect of limb alignment on the clinical outcomes. Methods: We retrospectively analyzed 55 patients who underwent kinematic aligned medial pivot TKA from September 2018 to January 2020. Patient-related outcomes (PROMs) were collected at baseline, 3, 12, and 24 months after surgery. Long-standing weight-bearing radiographs were performed three months after surgery. Results: We demonstrated a significant improvement in clinical outcomes from 3 months after surgery up to 24 months of follow-up. This clinical improvement was independent of limb alignment. The radiological analysis showed that the patient's native limb alignment was restored and that their joint line orientation was parallel to the floor. Conclusion: The association of kinematic alignment and a medial pivot TKA implant allows for a fast recovery, with good clinical and functional outcomes up to a minimum of 2 years of follow-up, independent of the final limb alignment. [ABSTRACT FROM AUTHOR]

The number of performed total knee arthroplasty (TKA) operations is constantly growing. This study proposes an evaluation of a series of patients undergoing medial pivot (MP) TKA surgery from a subjective, clinical and biomechanical point of view. A consecutive series of 100 TKAs implanted in a single centre, by the same surgeon, with a medial parapatellar approach with the sacrifice of the posterior cruciate ligament and cemented components were evaluated. All patients underwent standardized radiographic and functional clinical evaluation, with standing antero-posterior, lateral and patellar axial views; pre-operatively and post-operatively at 1, 3, 6 and 12 months; and then annually. Results were evaluated using three different patient-related outcome measurement scores (PROMs): the Knee Osteoarthritis Outcome Score (KOOS), the new Knee Society Score (nKSS) and the Short Form Health Survey 36 (SF-36). Excellent results in all treated knees were documented using the PROMs: the mean nKSS was 199.8, the mean KOOS was good to excellent in every subscale, and the mean was SF-36 82%. There were no cases of septic or aseptic loosening, vascular damage, neurological damage, or revision surgery for any reason. According to the experience gained, MP implants demonstrated excellent results, being clinically functional in both objective and subjective terms as well as radiographic evaluations, thus resulting in a winning strategy for obtaining a TKA that makes the patient satisfied and able to perform their daily life activities. [ABSTRACT FROM AUTHOR]

Objectives: The objective of the study is to evaluate the relationship between clinical results following posterior-stabilized total knee arthroplasty (TKA) and intraoperative kinematic pattern determined from navigation. Methods: Participants were patients with knee osteoarthritis and varus deformity who underwent primary posterior-stabilized TKA. Preoperative and post-implantation kinematic data were recorded, and all kinematic patterns were divided into two types: medial pivot (MP) or non-MP. Knees with MP and non-MP patterns after implantation were compared in terms of postoperative flexion angle, pain, patient satisfaction, expectations, and activity using the new Knee Society Score 2011 at 1 year postoperatively. Results: This study involved 55 patients (12 men, 43 women) with a mean age of 73.1 years and mean body mass index of 26.5 kg/m². Preoperative kinematic measurements showed MP in 23 knees and non-MP in 32 knees. After implantation, navigation showed MP in 25 knees and non-MP in 30 knees. No significant differences were found between kinematic patterns preoperatively and after implantation. Postoperative flexion angle, pain, patient satisfaction, expectations, and activity using Knee Society Score 2011 showed no differences between MP and non-MP knees. Conclusion: Intraoperative knee kinematics as measured by navigation could not predict postoperative outcomes of TKA. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to investigate the in vivo kinematics of the same femoral design mechanically aligned posterior-stabilised (PS) total knee arthroplasty (TKA) with either fixed-bearing (FB) or mobile-bearing (MB) inlay, implanted by the same surgeon, using model-based dynamic radiostereometric analysis (RSA). The hypothesis of the present study was that the MB design would show wider axial rotation than the FB design, without affecting the clinical outcomes. Materials and methods: A cohort of 21 non-randomised patients (21 DePuy Attune PS-FB) was evaluated by dynamic RSA analysis at a minimum 9-month follow-up, while performing differently demanding daily living activities such as sit to stand (STS) and deep knee lunge (DKL). Kinematic data were compared with those of a cohort of 22 patients implanted with the same prosthetic design but with MB inlay. Anterior–posterior (AP) translations, varus–valgus (VV) and internal–external (IE) rotations of the femoral component with respect to the tibial baseplate were investigated. Translation of medial and lateral compartment was analysed using the low point method according to Freeman et al. Questionnaires to calculate objective and subjective clinical scores were administered preoperatively and during follow-up visit by the same investigator. Results: The FB TKA design showed lower AP translation during STS (6.8 ± 3.3 mm in FB vs 9.9 ± 3.7 mm in MB, p = 0.006*), lower VV rotation (1.9 ± 0.8° in FB vs 5.3 ± 3.3° in MB, p = 0.005) and lower IE rotation (2.8 ± 1.1° in FB vs 9.5 ± 4.3° in MB, p = 0.001) during DKL than the mobile-bearing TKA design. Posterior-stabilised FB group showed significant lower translation of the low point of the medial compartment than the MB group (p = 0.008). The percentage of patients performing medial pivot in the FB group was higher compared to MB group in the examined motor tasks. No significant differences in post-operative range of motion (117° ± 16° for FB group and 124° ± 13° for MB group) and in clinical outcomes emerged between the two cohort. Conclusions: The FB and MB designs differed in AP translations, VV rotations and IE rotations of the femoral component with respect to the tibial component in STS and DKL. Furthermore, FB cohort reported a significant higher percentage of medial pivot with respect to MB cohort. Despite this, no differences in clinical outcomes were detected between groups. Both designs showed stable kinematics and represent a viable option in primary TKA. Level of evidence: Prospective cohort study, II. [ABSTRACT FROM AUTHOR]

Abstract Background The newly-designed alumina ceramic medial pivot total knee prosthesis was introduced to reduce polyethylene wear and better fit the anatomical morphology of the Asian population. This study aimed to clarify the long-term clinical results of alumina medial pivot total knee arthroplasty over a minimum follow-up period of 10 years. Methods The data of 135 consecutive patients who underwent primary alumina medial pivot total knee arthroplasty were analyzed in this retrospective cohort study. Patients were examined over a minimum 10-year follow-up period. The knee range of motion, Knee Society Score (KSS) knee score, Knee Society Score function score, and radiological parameters were assessed. The survival rate was also evaluated by using reoperation and revision as endpoints. Results The mean follow-up period lasted 11.8 ± 1.4 years. Patients who were not followed accounted for 7.4% of the total cohort. Knee and function scores of KSS improved significantly following total knee arthroplasty (P

Purpose: The aim of this meta-analysis was a comparison between medial pivot (MP) and posterior-stabilised (PS) knee designs regarding functional and radiological outcomes as well as gait parameters. Methods: A systematic literature search was conducted in PubMed, Cochrane Library, Science Direct and Clinical Trials.gov from conception up to April 2022, to identify eligible randomised control trials (RCTs). The extracted data were analysed according to the Preferred Reporting Items for Systematic reviews and Meta-Analysis (PRISMA) statement. Results: Fifteen studies met inclusion criteria, enrolling 1101 patients who underwent 1242 total knee arthroplasties (TKAs). A total of 1158 TKAs (581 MP/577 PS) were included in the quantitative analysis. Mean follow-up ranged from 6 months up to 6.6 years. MP knees showed comparable range of motion (ROM) with PS design 1, 2 and 4 years postoperatively (p = 0.2, p = 0.25, p = 0.34, respectively). No statistical difference was found in patient-related outcome measures (PROMs) (p > 0.05). Mean walking speed (MWS), length of stay (LOS), radiographic alignment and complications rates were also similar between the two groups (p > 0.05). Discussion: The present meta-analysis demonstrated that the theoretical biomechanical advantage of MP implants does not have a better impact on patient satisfaction compared to the traditional PS knees. Level of evidence: I. [ABSTRACT FROM AUTHOR]

Total knee arthroplasty (TKA) is a popular treatment for end-stage knee osteoarthritis. Advances in understanding knee biomechanics have led to the development of medial pivot (MP) prostheses, which aim to replicate natural knee kinematics. While short- and mid-term studies have shown favorable outcomes for MP-TKA, long-term follow-up studies are limited. This systematic review aims to analyze the available evidence on long-term outcomes of MP-TKA, including survivorship, complications, and patient-reported outcome measures (PROMs). A comprehensive search was conducted in PubMed, Embase, and Cochrane Database of Systematic Reviews for English language studies reporting long-term outcomes of primary MP-TKA. Nine studies with an average follow-up of 12.4 years were included. Data on survivorship, complications, and PROMs were collected and analyzed. The overall survivorship of MP-TKA was 98.2% at an average follow-up of 12.4 years. Aseptic loosening and periprosthetic joint infection (PJI) were the most common reasons for revision, with a revision rate of 0.4% for each. The overall complication rate was 6.6%, with secondary anterior knee pain and PJI being the most frequent complications. The reoperation rate was 3.1%, primarily due to PJI and knee instability. PROMs significantly improved postoperatively. MP-TKA demonstrates favorable long-term outcomes with high survivorship, low complication rates, and enhanced PROMs. The procedure provides reliable management for end-stage osteoarthritis, offering patients improved knee function and pain relief. Further research with standardized reporting and larger sample sizes is needed to validate and compare these findings to other implant designs. [ABSTRACT FROM AUTHOR]

Purpose : For a new tibial insert design with ball-in-socket (B-in-S) medial conformity (MC), posterior cruciate ligament (PCL) retention, and flat lateral articular surface (B-in-S MC + PCL), this study determined whether internal tibial rotation and knee flexion were limited and clinical outcome scores were lower during weight-bearing activities relative to an insert with intermediate (I) (i.e., less than ball-in-socket) medial conformity (I MC + PCL). Methods: Twenty-five patients were treated with bilateral unrestricted, caliper-verified kinematic alignment (KA) total knee arthroplasty (TKA) with an I MC + PCL insert and B-in-S MC + PCL insert in opposite knees. Each patient performed weight-bearing deep knee bend, step up, and chair rise under single-plane fluoroscopy. Analysis following 3D model-to-2D image registration determined internal tibial rotation. For each TKA, knee flexion was measured and patients completed clinical outcome scoring questionnaires. Results: Internal tibial rotation did not differ between conformities during chair rise and step up (p = 0.3419 and 0.1030, respectively). During deep knee bend, internal tibial rotation between 90° and maximum flexion was 3° greater in the B-in-S MC + PCL group (18° vs 15°) (p = 0.0290). Mean knee flexion (p = 0.3115) and median Forgotten Joint Score (FJS), Oxford Knee Score (OKS), and Western Ontario and McMasters Universities Arthritis Index (WOMAC) scores (p = 0.2100, 0.2154, and 0.4542, respectively) did not differ between conformities. Conclusion: An insert with ball-in-socket medial conformity, which maximizes anteroposterior (AP) stability, did not limit internal tibial rotation and knee flexion and did not lower patient-reported outcomes when implanted with unrestricted caliper-verified KA and PCL retention. The high AP stability provided by the medial ball-in-socket might interest those surgeons exploring the treatment of the active patient with a desire to return to high-level and athletic activities. [ABSTRACT FROM AUTHOR]

Abstract Background Total knee arthroplasty (TKA) is one of the most performed orthopedic procedures worldwide. While excellent efficacy has been reported, about 20% of patients are not satisfied with the result. A potential cause is the problematic reproduction of knee kinematics. This systematic review examines gait analysis studies in primary medial pivot (MP) and posterior stabilized (PS) TKAs to investigate the differences between the two prosthesis designs. Methods A systematic review was conducted by following PRISMA guidelines. Five databases (PubMed, Medline, Embase, Scopus and the Cochrane Database of Systematic Reviews) were analyzed, and eligible articles were evaluated in terms of the levels of evidence. The methodological quality of the articles was assessed by using the MINORS scoring. This review was registered in PROSPERO. Results Nine studies were included. Gait analysis was performed in 197 MP TKA and 192 PS TKA patients. PS TKA cases showed (P 0.05) was reported regarding gait spatial–temporal parameters. The Forgotten Joint Score (FJS) and Western Ontario and McMaster Universities Comparison in terms of Arthritis Index (WOMAC) score (mean stiffness) showed that MP TKA yielded significantly better results than PS TKA. Conclusions This systematic review revealed significant kinematic and kinetic differences between MP and PS TKA at all gait analysis phases. Furthermore, the considerable difference between TKA design and the kinematics of healthy knee were highlighted in this study. Level of evidence III.

Background: The newly-designed alumina ceramic medial pivot total knee prosthesis was introduced to reduce polyethylene wear and better fit the anatomical morphology of the Asian population. This study aimed to clarify the long-term clinical results of alumina medial pivot total knee arthroplasty over a minimum follow-up period of 10 years. Methods: The data of 135 consecutive patients who underwent primary alumina medial pivot total knee arthroplasty were analyzed in this retrospective cohort study. Patients were examined over a minimum 10-year follow-up period. The knee range of motion, Knee Society Score (KSS) knee score, Knee Society Score function score, and radiological parameters were assessed. The survival rate was also evaluated by using reoperation and revision as endpoints. Results: The mean follow-up period lasted 11.8 ± 1.4 years. Patients who were not followed accounted for 7.4% of the total cohort. Knee and function scores of KSS improved significantly following total knee arthroplasty (P < 0.001). In 27 individuals (28.1%), a radiolucent line was observed. Aseptic loosening occurred in three cases (3.1%). The survival rates for reoperation and revision were 94.8% and 95.8% 10 years after the operation, respectively. Conclusions: During a minimum 10-year follow-up period, the present model of alumina medial pivot total knee arthroplasty showed good clinical outcomes and survival rates. [ABSTRACT FROM AUTHOR]

Abstract Purpose We aimed to compare the postoperative clinical efficacy and safety of medial pivot (MP) prosthesis and posterior-stabilized (PS) prosthesis in the treatment of knee osteoarthritis (KOA). Methods All studies involving MP and PS prosthesis in PubMed, EMBASE, Cochrane Library, and Web of Science were searched since the establishment of the database. The included outcomes were knee range of motion (ROM), functional score, radiographic results, complication rate, and revision rate. Studies were independently evaluated by the Newcastle–Ottawa Scale for case–control studies and the assessment tool of the Cochrane Collaboration for randomized controlled trials. I 2 was used to test the heterogeneity, and fixed- or random-effects models were selected for meta-analysis according to the heterogeneity results. Results A total of 19 studies, consisting of 3592 patients and 3783 knees (MP: 1811 knees, PS: 1972 knees), were included in the meta-analysis. The WOMAC (MD = − 1.11, 95% CI − 1.98 to − 0.23; P = 0.01) and HSS (MD = − 4.32, 95% CI − 8.30 to − 0.34; P = 0.03) in the MP group were significantly lower compared with the PS group, and the complication rate (OR 0.53, 95% CI 0.33–0.87; P = 0.01) was also lower compared with the PS group. There was no significant difference in ROM, radiographic results, and revision rate between the two groups (P > 0.5). Conclusions The existing literature provided evidence to support better clinical effect and lower complication rate of MP prosthesis compared to PS prosthesis. These results provide a reference for clinicians when choosing a suitable prosthesis.

Background: Total knee arthroplasty (TKA) is one of the most performed orthopedic procedures worldwide. While excellent efficacy has been reported, about 20% of patients are not satisfied with the result. A potential cause is the problematic reproduction of knee kinematics. This systematic review examines gait analysis studies in primary medial pivot (MP) and posterior stabilized (PS) TKAs to investigate the differences between the two prosthesis designs. Methods: A systematic review was conducted by following PRISMA guidelines. Five databases (PubMed, Medline, Embase, Scopus and the Cochrane Database of Systematic Reviews) were analyzed, and eligible articles were evaluated in terms of the levels of evidence. The methodological quality of the articles was assessed by using the MINORS scoring. This review was registered in PROSPERO. Results: Nine studies were included. Gait analysis was performed in 197 MP TKA and 192 PS TKA patients. PS TKA cases showed (P < 0.05) a significantly higher peak of knee flexion angle during the swing phase, greater knee flexion angle at toe-off, an increased knee adduction angle, higher knee flexion and extension moment, increased anterior femoral roll during knee flexion and anterior translation on medial and lateral condyle during knee flexion compared to MP TKA. MP TKA showed statistically significant (P < 0.05) higher knee rotational moment and greater tibiofemoral external rotation motion during knee flexion than PS TKA. No statistically significant difference (P > 0.05) was reported regarding gait spatial–temporal parameters. The Forgotten Joint Score (FJS) and Western Ontario and McMaster Universities Comparison in terms of Arthritis Index (WOMAC) score (mean stiffness) showed that MP TKA yielded significantly better results than PS TKA. Conclusions: This systematic review revealed significant kinematic and kinetic differences between MP and PS TKA at all gait analysis phases. Furthermore, the considerable difference between TKA design and the kinematics of healthy knee were highlighted in this study. Level of evidence: III. [ABSTRACT FROM AUTHOR]

This study aimed to compare the in-vivo kinematics and articular contact status between medial-pivot total knee arthroplasty (MP-TKA) and posterior stabilized (PS) TKA during weight-bearing single-leg lunge. 16 MP-TKA and 12 PS-TKA patients performed bilateral single-leg lunges under dual fluoroscopy surveillance to determine the in-vivo six degrees-of-freedom knee kinematics. The closest point between the surface models of the femoral condyle and the polyethylene insert was used to determine the contact position and area. The nonparametric statistics analysis was performed to test the symmetry of the kinematics between MP-TKA and PS-TKA. PS-TKA demonstrated a significantly greater range of AP translation than MP-TKA during high flexion (p = 0.0002). Both groups showed a significantly greater range of lateral compartment posterior translation with medial pivot rotation. The contact points of PS-TKA were located significantly more posterior than MP-TKA in both medial (10°–100°) and lateral (5°–40°, 55°–100°) compartments (p < 0.0500). MP-TKA had a significantly larger contact area in the medial compartment than in the lateral compartment. In contrast, no significant differences were observed in PS-TKA. The present study revealed no significant differences in clinical outcomes between the MP and PS groups. The PS-TKA demonstrated significantly more posterior translations than MP-TKA at high flexion. The contact points are located more posteriorly in PS-TKA compared with MP-TKA. A larger contact area and medial pivot pattern during high flexion in MP-TKA indicated that MP-TKA provides enhanced medial pivot rotation. [ABSTRACT FROM AUTHOR]

Purpose: Stability in the sagittal plane, particularly regarding anterior cruciate ligament compensation, and postoperative functionality and satisfaction remain issues in total knee arthroplasty. Therefore, this prospective study compared the clinical outcomes between medial-pivot-based and posterior-stabilised total knee arthroplasty based on anterior translation and clinical scores. Methods: To assess outcomes of total knee arthroplasty for varus osteoarthritis, the anterior translation distance of the tibia relative to the femur was measured at 30 and 60° of flexion using a KS measure Arthrometer at 6 months postoperatively. The 2011 Knee Society Score, Forgotten Joint Score, visual analogue scale for pain, and range of motion were assessed at 6 months and 1 year postoperatively. The correlations among each score, anterior translation distance, range of motion, and visual analogue scale score for pain were investigated. Results: The medial-pivot and posterior-stabilised groups comprised 70 and 51 patients, respectively. The medial-pivot group exhibited a significantly shorter anterior translation distance at 60° flexion than the posterior-stabilised group. Furthermore, the medial-pivot group achieved significantly better outcomes regarding the visual analogue scale for pain, 2011 Knee Society Score, and Forgotten Joint Score than the posterior-stabilised group. A significant negative correlation was observed between the anterior translation distance and the function score of the 2011 Knee Society Score, whereas a significant positive correlation was found between the anterior translation distance and flexion angle, and between the extension angle and score of the Forgotten Joint Score or 2011 Knee Society Score. Significant negative correlations were also found between the pain visual analogue scale and both the 2011 Knee Society Score and Forgotten Joint Score. Conclusion: In total knee arthroplasty for osteoarthritis, the medial-pivot group displayed a shorter anterior translation distance than the posterior-stabilised group at 6 months postoperatively. The visual analogue scale score for pain was also significantly lower in the medial-pivot group than that in the posterior-stabilised group at both 6 months and 1 year postoperatively. Because a correlation was observed between the anterior translation distance and the function score, medial-pivot-based total knee arthroplasty was considered to significantly improve postoperative function compared to posterior-stabilised total knee arthroplasty. [ABSTRACT FROM AUTHOR]

Purpose: Postoperative instability represents one of the most common complications following primary total knee arthroplasty (TKA). To prevent this outcome, valgus deformities have been historically treated using more constrained implants. The purpose of this study was to evaluate the outcome of treating a moderate valgus deformity by combining a surgical technique used to release the postero-lateral soft tissue envelope with the use of a medially congruent (MC) TKA design without using classical, semi-constrained inserts. Methods: Seventy-nine MC TKAs were performed by three surgeons at three institutions between 2016 and 2018 as part of a multicenter, international study. Inclusion criteria were: radiographic late-stage osteoarthritic knees with Ranawat's type 1 or 2 classification of valgus deformity and integrity of the medial capsular–ligament complex (less than 10 mm of medial opening during valgus stress test at 10° of knee flexion). Exclusion criteria were: BMI > 40; neuromuscular, metabolic, or immunologic disorders; or the inability to complete outcome measures or radiographic assessment. Results: Seventy-seven patients (79 knees), 59 males and 18 females, were evaluated at 2-year minimum follow-up according to the Knee Society Score (KSS) and Forgotten Joint Score (FJS). Mean age at surgery was 70 years (range 48–91). The mean range of motion (ROM) improved from 110° (range 85°–130°) preoperatively to 121° (range 105°–135°) (p < 0.001) at the time of the last follow-up. Preoperative knee extension significantly improved from 3° (range − 15° to 20°) to 1° (range − 5° to 5°) of flexion at the last follow-up in all the patients. KSS and KSS Functional scores were 89 (range 65–100) and 82 points (range 55–100), respectively. The FJS obtained at the last follow-up was 72 (range 49–88). Two patients (2.5%) had major postoperative complications (one periprosthetic joint infection; one postoperative patellar fracture) requiring surgical interventions. Conclusions: In different surgeon's hands, the use of a modern medially congruent TKA design yielded good clinical outcomes at 2 years in a consecutive series of TKA in valgus arthritic knees. Postoperative instability was not recorded in this series and this finding was related to the high conformity design of the MC polyethylene insert, which significantly differs from classical posterior-stabilized (PS) designs. Level of evidence: IV. [ABSTRACT FROM AUTHOR]

Background: Total knee arthroplasty (TKA) is considered to be highly successful in treatment of end-stage osteoarthritis. There are multiple implant designs available on the market, and it is difficult to point which one is the best. The aim of this study was to compare the clinical and functional outcomes and gait pattern after TKA with the use of fixed-bearing medial pivot (K-Mod) vs multi-radius design (NexGen) implants and to compare them to norms for healthy patients with no osteoarthritis or arthroplasty procedure in anamnesis. Methods: A group of 30 patients who received the medial pivot (MP) TKA and 33 patients who received the posterior-stabilized (PS) TKA between May and August of 2018 were included. All surgeries were performed in the level III academic hospital by a single surgeon. Every patient was asked to fulfill the The Western Ontario and McMaster Universities Arthritis Index (WOMAC) questionnaire preoperatively and 2 years postoperatively. Standard X-ray, biomechanical gait analysis using a motion capture system, and statistical analysis were performed at 2 years postoperatively. Results: A total of 28 patients from either MP cohort (93%) or PS (85%) matched-control cohort completed the whole assessment at the final follow-up. There were statistically significant differences in a few gait parameters such as shorter mean step length both in operated and healthy limb, lower mean gait velocity, and lower mean walking cadence than the norm in both MP and PS groups. As to the WOMAC score, there was statistically significant improvement in both groups comparing preoperative and postoperative outcomes. Nevertheless, in the MP group, there was a significantly higher score, indicating worse outcomes, in the stiffness part of the WOMAC score than in the PS group. No significant differences were found between groups during radiological evaluation. Conclusions: There were satisfying and promising clinical, radiographic, and patient-reported outcomes in both MP and PS groups with very little difference in relation to norm values. However, both implants failed in fully restoring gait patterns similar to the healthy limb of the same patient.

• PS group had greater forward lean which reduced hip flexion on the operated limb. • MBS and PS groups favoured their non-operated limb during sit-to-stand tasks. • Operated limb had less muscle and knee contact forces compared to non-operated limb. • TKA groups had reduced medial compartment knee contact force during sit-to-stand tasks. • Control group favoured their dominant limb during sit-to-stand tasks. Understanding how forces are transmitted through the knee after TKA is essential, as it may explain why many patients experience pain or functional limitations during various activities. This study compared knee muscle forces and knee contact forces (KCF) during sit-to-stand in patients one year after unilateral total knee arthroplasty (TKA) with either a medial ball-and-socket (MBS) or posterior stabilized (PS) implant and compared them to a group of similarly healthy aged controls (CTRL). A musculoskeletal model and static optimization estimated lower limb kinematics, knee kinetics, muscle forces, and KCFs. The normalized sit-to-stand cycle was compared among the groups using statistical nonparametric mapping, and peak between-limb differences were compared using discrete statistics. The PS group required greater forward lean during the sit-to-stand task, causing greater spine flexion, posterior pelvic tilt, and decreased hip flexion on the operated limb. PS and MBS groups favoured their non-operated limb, resulting in less range of motion throughout the lower limb, lower knee kinetics, muscle forces, and KCFs on the operated limb. Compared to the controls, the MBS and PS groups had reduced medial compartment KCF. The control group did favour their dominant limb over their non-dominant limb. Post-operative rehabilitation should continue to promote greater use of the operated knee to have more symmetrical loading between operated and non-operated limbs and improve strength and mobility at the hip and ankle joints. One year after surgery, TKA patients remain with reduced muscle forces and KCF on their operated limb during a sit-to-stand task, regardless whether they received an MBS or PS implant. [ABSTRACT FROM AUTHOR]

Restoring medial knee pivot kinematics post-total knee arthroplasty is widely recognized to enhance patient satisfaction. Our study investigates the kinematics of patients who received posterior stabilized implants via robotic-arm assisted surgery, specifically analyzing effects of implant alignment and soft tissue balance on pivot location. Twelve high-functioning patients with unilateral posterior stabilizing knee implants underwent CT-guided robotic-arm assisted surgery. We then evaluated their knee kinematics using stereo radiography during gait, stair descent, lunge, seated knee extension and leg press. Femoral low-point condylar kinematics were used to calculate the transverse center of rotation, or pivot, using principal component analysis. Linear mixed effects regression was used to identify surgical parameters that influence pivot location across a flexion range. Across all five activities a central pivot pattern emerged as the primary pivot location (40 %) followed by medial (25 %), no pivot (22 %) and lateral (14 %). Tibial medial resection depth and Tibial implant flexion-extension placement were significantly associated with shifting the pivot location laterally prior to cam-post engagement. Femoral implant external-internal implant placement, and medial compartment laxity in extension were significantly associated with shifting the pivot location laterally during the cam-post engagement, while femoral distal-lateral resection depth was associated with a medial shift. Central and medial pivot locations are predominant in patients with posterior stabilized total knee arthroplasty, facilitated by robotic-arm assisted surgery. Despite significant associations between surgical parameters such as tibial medial resection depth and lateral compartment laxity with medial pivot, these variables explained a small portion of the variability in pivot location. This suggests that while surgical precision influences pivot kinematics, individual patient factors may play a more critical role, suggesting a need for further research into patient-specific biomechanics to optimize post-surgical outcomes. • Central is the primary pivot location across activities of daily living. • Engagement of cam-post mechanism reduces pivot location variability. • Surgical parameters impact pivot location during cam-post engagement phases. • Pivot location during pre-cam engagement is mostly determined by individual patient variability. [ABSTRACT FROM AUTHOR]

Background: Clinical outcomes of kinematically aligned total knee arthroplasty (KA-TKA) have been reported as comparable or superior to those of mechanically aligned TKA (MA-TKA). However, cruciate-retaining prostheses have mostly been used for KA-TKA. This study used medial pivot knee prostheses for KA-TKA, and knee kinematics after KA-TKA were assessed and compared with those after MA-TKA. Methods: Thirteen knees in 9 patients undergoing primary TKA (8 KAs, 5 MAs) were subjected to two-dimensional (2D) to three-dimensional (3D) registration analysis at 1 year postoperatively. Each patient performed weight-bearing activities, and movements were recorded as intermittent digital radiographic images. Three-dimensional implant positions during activities were analyzed for anterior-posterior translation in the sagittal plane, condylar liftoff and mediolateral translation in the coronal plane, and femoral rotation in the axial plane. Results: Posterior translation of the lateral femoral condyle from 0° to 100° was larger in KA-TKA than in MA-TKA (P = .006). The degrees of condylar liftoff and mediolateral translation were comparable between TKAs. Total external rotation of the femoral component relative to tibial component was significantly greater for KA-TKA (7.7 ± 5.2°) than for MA-TKA (1.3 ± 3.3°; P = .03). The kinematic path of the femoral component revealed greater medial pivoting motion in KA-TKA than in MA-TKA. Conclusions: KA-TKA using a medial pivot knee prosthesis successfully reproduced the medial pivot pattern and achieved larger femoral external rotation relative to the tibia than MA-TKA. KA-TKA was able to maximize the primary concept of the medial pivot knee prosthesis.

Purpose: The purpose of this study was to analyze the dynamic kinematics of the mobile medial pivot-type total knee arthroplasty (MMPTKA) using the three-dimensional (3D)-to-2D registration technique. Methods: Cadaveric knees from five humans were used. Computed tomography of the lower limb and preoperative 3D planning for MMPTKA were performed. After performing TKA, passive motion of the knee was observed from a fully extended position to maximum flexion using a flat panel detector. The following parameters were determined: (1) anteroposterior (AP) translations of the medial and lateral most distal points (estimated contact point) of the femoral component, (2) rotational femoral component's X-axis (FCX) angle, and (3) rotational insert angle. Paired t-tests were used to analyze differences in the AP translation between the medial and lateral most distal points of the femoral component as well as differences in the changes in the rotational angle between the FCX and X-axis of the insert on the tibial component's axial plane. Results: The AP translations of the femoral component's medial and lateral most distal points were 8.4 ± 2.5 and 13.6 ± 3.3 mm, respectively (p = 0.001). The rotational angles of the FCX and insert were 10.7° ± 4.9° external rotation and 8.9° ± 4.1° internal rotation, respectively (p = 0.004). Conclusions: The posterior translation of the lateral side of the femoral component was greater than that of the medial in all cases. Hence, a medial pivot pattern was identified. The femoral component exhibited external rotation throughout knee flexion in all subjects, whereas the mobile insert exhibited internal rotation (opposite pattern relative to the femoral component). This study provides valuable kinematical information of MMPTKA that has not been clear yet. [ABSTRACT FROM AUTHOR]

In the last decades, several surgical techniques, such as medial pivot (MP) philosophy and kinematic alignment (KA), have been introduced in total knee arthroplasty (TKA) to improve patients' outcomes. This retrospective study aims to evaluate the clinical, radiographic, and functional results of PCL preservation or sacrifice in KA MP-TKA. A consecutive series of 147 patients older than 60, with a minimum follow-up of two years, were treated with TKA for severe primary knee osteoarthritis (OA) at the Department of Orthopedics and Traumatology between 1 January 2019, and 1 July 2020. After excluding those not meeting the inclusion criteria, 64 patients were included in the study analysis. Regarding radiographic outcomes, no statistically significant difference was observed between patients with preserved or sacrificed PCL (p > 0.05). A slight improvement in Knee Society Score (KSS), knee and function score, and FJS was observed for the PCL-preserved group, although this superiority tendency was not statistically significant (p > 0.05). PCL-preserved MA MP-TKA reported a statistically significant result in only two questions on the FJS questionnaire (p < 0.05). A slight, non-statistically significant improvement in active ROM was found in the PCL-sacrificed group (p > 0.05). No interventions or revisions were reported in this case series for all treated patients at the final follow-up. No significant differences were described in clinical, radiographic, and functional outcomes in preserved or sacrificed PCL KA MP-TKA. Although not significant, a slight trend toward better clinical outcomes was reported in PCL-preserved KA MP-TKA. [ABSTRACT FROM AUTHOR]

Background: Total knee arthroplasty (TKA) remains the standard of care for treating end-stage osteoarthritis of the knee. Approximately 15%-20% of the patients are dissatisfied following surgery. To improve accuracy and outcomes of TKA, various assistive technologies have been introduced. For this study, an augmented reality (AR) system was explored and tested., Methods: The Knee + system (Pixee Medical, Besancon, France) was used to guide TKA. It uses a combination of quick response-code labeled instruments and AR glasses to guide tibial and femoral cuts. The primary research goal was to evaluate its accuracy by direct comparing the planned angular values for lateral distal femoral angle, medial proximal tibial angle, hip-knee-ankle axis, and tibial slope to the intraoperative obtained values and the measured angles on postoperative full leg radiographs. The secondary research goal was to assess its feasibility., Results: This retrospective study evaluated 124 patients, with a follow-up of at least 1 year. The average absolute difference between planned and measured postop values were 1.39° for lateral distal femoral angle, 1.03° for medial proximal tibial angle, 2.16° for tibial slope, and 1.51° for hip-knee-ankle axis. Within the follow-up period, 8 complications were observed. The average surgical time was 83 minutes., Conclusions: This study has demonstrated a high accuracy, comparable to robotic-assisted total knee arthroplasty, of the Knee + AR system. It has shown to be a safe, cheap and time-efficient assistive technology for patients undergoing medial pivot TKA., (© 2024 The Authors.)

As the conformity of a medial ball-in-socket total knee arthroplasty (TKA) provides intrinsic anterior-posterior (A-P) stability, surgeons cannot rely on the manual examination of sagittal laxity to identify the optimal insert thickness. Instead, the present study determined whether measuring tibial axial orientation in extension and 90° flexion with an insert goniometer could identify the optimal thickness that, when implanted, provides high postoperative function. In twenty-two patients that underwent unrestricted caliper-verified kinematic alignment (KA) with a PCL retaining implant, two surgeons measured tibial orientation in extension and 90° flexion with 10, 11, 12, and 13 mm thick insert goniometers. Each TKA had one insert thickness that restored either the maximum external tibial orientation in extension, the maximum internal tibial orientation at 90° flexion, or both relative to 1 mm thinner and thicker inserts. In addition, the 6-month median [interquartile range] Forgotten Joint Score of 73 (54–87) and Oxford Knee Score of 42 (38–45) indicated high satisfaction and function. In conclusion, surgeons using a medial ball-in-socket TKA design can measure external tibial orientation in extension and internal tibial orientation at 90° flexion with an insert goniometer. Furthermore, implanting an insert with the thickness that provided the maximum orientation values resulted in high postoperative function, thereby personalizing PCL tension. [ABSTRACT FROM AUTHOR]

Purpose: We aimed to compare the postoperative clinical efficacy and safety of medial pivot (MP) prosthesis and posterior-stabilized (PS) prosthesis in the treatment of knee osteoarthritis (KOA). Methods: All studies involving MP and PS prosthesis in PubMed, EMBASE, Cochrane Library, and Web of Science were searched since the establishment of the database. The included outcomes were knee range of motion (ROM), functional score, radiographic results, complication rate, and revision rate. Studies were independently evaluated by the Newcastle–Ottawa Scale for case–control studies and the assessment tool of the Cochrane Collaboration for randomized controlled trials. I2 was used to test the heterogeneity, and fixed- or random-effects models were selected for meta-analysis according to the heterogeneity results. Results: A total of 19 studies, consisting of 3592 patients and 3783 knees (MP: 1811 knees, PS: 1972 knees), were included in the meta-analysis. The WOMAC (MD = − 1.11, 95% CI − 1.98 to − 0.23; P = 0.01) and HSS (MD = − 4.32, 95% CI − 8.30 to − 0.34; P = 0.03) in the MP group were significantly lower compared with the PS group, and the complication rate (OR 0.53, 95% CI 0.33–0.87; P = 0.01) was also lower compared with the PS group. There was no significant difference in ROM, radiographic results, and revision rate between the two groups (P > 0.5). Conclusions: The existing literature provided evidence to support better clinical effect and lower complication rate of MP prosthesis compared to PS prosthesis. These results provide a reference for clinicians when choosing a suitable prosthesis. [ABSTRACT FROM AUTHOR]

Introduction: The medial pivot total knee arthroplasty (TKA) has good patients' satisfaction; however, there is likely the restriction of postoperative knee flexion. The 2nd generation medial pivot TKA prosthesis was designed to improve postoperative knee flexion. This study aimed to compare the clinical outcomes and patient satisfaction between the 2nd generation and 1st generation medial pivot TKA prostheses. Materials and methods: We conducted a retrospective study of 472 consecutive TKAs, performed using either the 2nd generation (EVOLUTION™), having smaller posterior femoral condyle and asymmetrical tibial tray, or 1st generation (ADVANCE™) prosthesis. The use of each system was historically determined. Patient age, sex and body mass index were matched between the two groups, with 157 cases ultimately included in each group. Measured clinical outcomes included: knee range of motion, the Knee Society Score, the rate of re-operation, and radiological parameters. Patient satisfaction was evaluated using the 12-item Forgotten Joint Score (FJS-12). Results: The average follow-up period was 5.0 (3.7–6.3) years for the 2nd generation group and 8.7 (6.1–12.8) years for the 1st generation group (p < 0.01). The postoperative knee flexion range was 127° (80°–140°) for the 2nd generation and 118° (90°–135°) for the 1st generation at final follow-up (p < 0.01). On multivariate regression analysis, use of the 2nd generation prosthesis predicted greater postoperative knee flexion. The average FJS-12 score was 64 (0–100) for the 2nd generation and mean 57 (0–100) for the 1st generation (p < 0.01). Other clinical outcomes were similar between the two groups. Conclusions: Compared to the 1st generation, the 2nd generation medial pivot prosthesis provides greater postoperative knee flexion and patient satisfaction. [ABSTRACT FROM AUTHOR]

Aims: Medial pivot (MP) total knee arthroplasties (TKAs) were designed to mimic native knee kinematics with their deep medial congruent fitting of the tibia to the femur almost like a ball-on-socket, and a flat lateral part. GMK Sphere is a novel MP implant. Our primary aim was to study the migration pattern of the tibial tray of this TKA. Methods: A total of 31 patients were recruited to this single-group radiostereometric analysis (RSA) study and received a medial pivot GMK Sphere TKA. The distributions of male patients versus female patients and right versus left knees were 21:10 and 17:14, respectively. Mean BMI was 29 kg/m2 (95% confidence interval (CI) 27 to 30) and mean age at surgery was 63 years (95% CI 61 to 66). Maximum total point motions (MTPMs), medial, proximal, and anterior translations and transversal, internal, and varus rotations were calculated at three, 12, and 24 months. Patient-reported outcome measure data were also retrieved. Results: MTPMs at three, 12, and 24 months were 1.0 mm (95% CI 0.8 to 1.2), 1.3 mm (95% CI 0.9 to 1.7), and 1.4 mm (0.8 to 2.0), respectively. The Forgotten Joint Score was 79 (95% CI 39 to 95) and Knee Injury and Osteoarthritis Outcome Score obtained at two years was 94 (95% CI 81 to 100), 86 (95% CI 75 to 93), 94 (95% CI 88 to 100), 69 (95% CI 48 to 88), and 81 (95% CI59 to 100) for Pain, Symptoms, Activities of Daily Living, Sport & Recreation, and Quality of Life, respectively. Conclusion: In conclusion, we found that the mean increase in MTPM was lower than 0.2 mm between 12 and 24 months and thus apparently stable. Yet the GMK Sphere had higher migration at one and two years than anticipated. Based on current RSA data, we therefore cannot conclude on the long-term performance of the implant, pending further assessment. Cite this article: Bone Jt Open 2021;2(9):737–744.

Objective To systematically evaluate the patellofemoral joint design of medial pivot prosthesis, which incorporates a variety of “patella‐friendly” design features, by comparing clinical and radiographic results with another prosthesis. Methods All consecutive patients who underwent unilateral total knee arthroplasty (TKA) with medial pivot prosthesis (Group MP, 126 cases) between September 2016 and April 2018 were enrolled in this retrospective study. For each patient reviewed, a control patient was matched, according to age, gender, side, body mass index (BMI), preoperative range of motion (ROM), and operating period, who had received primary unilateral TKA with a conventional posterior‐stabilized prosthesis at the same period as the study group (Group PS, 126 cases). All patients underwent at least 1‐year follow‐up. At the preoperative and final follow‐up periods, data on the Knee Society Score (KSS) score, WOMAC score, Kujala score, and ROM were collected. Merchant views were taken with the knee flexion at 30°, 60°, and 90° to measure patella shift and tilt. Preoperative posterior condylar angle (PCA) was also measured. Postoperative complications, including anterior knee pain, maltracking, patellar clunk or crepitus (PCC), were evaluated. Results There were no significant differences in the demographics or clinical characteristics between the two groups. No statistically significant difference was identified in the KSS total score, including knee score and function score, or in the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score between the two groups after the operation. We found statistically significant differences in the postoperative Kujala scores and the ROMs between the two groups. The mean Kujala score in group MP was better than in group PS (MP 77.16 ± 3.80 vs PS 75.97 ± 4.06, P

Purpose: Medial pivot total knee arthroplasty (MP-TKA) is characterized by the ball-in-socket medial tibiofemoral articulation to achieve low wear and to reproduce the medial pivot motion similar to that in the normal knee, and there have been reports of favorable long-term postsurgical outcomes. However, most of these cases concerned varus knees, and the outcomes of MP-TKA in valgus knees are unknown. The objective of this study was to investigate the postoperative outcomes in end-stage valgus knee OA patients who underwent MP-TKA, through comparisons with those who underwent TKA using the same prosthesis for varus deformity. Methods: This retrospective, single-center, cohort study analyzed 171 knees of 121 patients who were divided into two groups (valgus knee group: 15 knees (13 patients), varus knee group: 156 knees (109 patients)). Primary outcome measures included the knee joint range of motion (evaluated preoperatively and at every year postoperatively). Secondary outcomes included operative time, laboratory data, estimated blood loss, clinical outcome measures and adverse events. Results: There were no significant differences in age, sex and body mass index, as well as in the postoperative primary and secondary outcome measures between the two groups. Conclusion: The use of MP-TKA featuring ball-in-socket medial tibiofemoral articulation in patients with valgus knee OA showed equally favorable clinical outcomes more than 2 years after surgery, compared to patients with varus knees who received MP-TKA. [ABSTRACT FROM AUTHOR]

Background: Both medial pivot (MP) and rotating platform (RP) mobile-bearing (MB) total knee arthroplasty (TKA) have been developed to better mimic the natural knee kinematics and femoral roll back in flexion. The purpose of this retrospective study was to compare the mid-term functional outcomes and range of motion (ROM) of MP and RP types of total knee arthroplasty. Methods: 116 patients (mean age of 66.3 years) undergoing TKA (52 Medial pivot design and 64 Rotating Platform design) were evaluated retrospectively with Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) knee score, knee society score (KSS) with its subgroups namely, Knee Score (KSKS) and Functional Score (KSFS) and forgotten joint score (FJS) at a mean follow-up of 7.1 years. Range of motion (ROM) and tibiofemoral anatomic angle on the radiographs were also compared. Results: Mean ROM, WOMAC and KSKS improved significantly from pre-operative to postoperative knees in both the groups. There was, however, no significant difference between the two groups at the final follow-up. In contrast, mean KSFS score improved to 89.5 ± 8.1 in MP group and 86.3 ± 7.1 in RP Group (p = 0.025), while mean FJS was 85.6 ± 4.1 and 80.9 ± 5.4 in the MP and RP groups, respectively (p = < 0.0001). Conclusion: Satisfactory clinical and functional outcomes can be obtained using either a MP or RP knee joint in tricompartmental osteoarthritis of knee. The MP design scores better on the KSFS score and FJS than the RP-TKA. [ABSTRACT FROM AUTHOR]

Background: This study aims to evaluate the clinical and radiological outcomes of a modified technique of Kinematically Aligned Total Knee Arthroplasty (KA TKA) using a cruciate sacrificing (CS) medially stabilised prosthesis at a minimum 24-months follow-up. Methods: 59 patients with a varus HKA angle who underwent a TKA from May, 2016 to April, 2017 were retrospectively enrolled. Radiological and clinical evaluations were assessed after 40 days, 6 months and at a minimum follow-up of 24 months. Long leg standing X-rays were performed pre-operatively and the Hip–Knee–Ankle (HKA) angle, the mechanical Lateral Distal Femoral Angle (mLDFA), the mechanical Medial Proximal Tibial Angle (mMPTA) and the Knee Joint Line Obliquity Angle (KJLOA) were analysed. At a minimum follow-up of 24 months, the patients were evaluated subjectively based on the Western Ontario and McMaster Universities Osteoarthritis Index Score (WOMAC) and the Oxford Knee Score (OKS). The post-operative range of motion (ROM) was measured. To reduce flexion instability, an original technique was used, with more posterior positioning of the femoral component, called the "virtuous mistake". Results were compared to the data reported in the literature in patients treated with standard kinematic alignment (KA) technique. Results: No difference was found between the mean pre-operative and post-operative angles regarding mLDFA (p value = 0.410) and mMTPA (p value = 0.242). A difference of 0.8° in HKA angle between males and females was found, with more varus results in males. At a minimum follow-up of 24 months, the WOMAC was 87 (SD 4.3), the OKS was 41 (SD 2.4), and the flexion was 124°, which was similar to the data reported in literature with standard KA. There were not any cases of aseptic failures. Conclusions: The modified KA TKA surgical technique proposed in this study can achieve good clinical results at minimum 24 months of follow-up, reproducing accurately native mLDFA and mMPTA. Level of evidence: Level III, therapeutic study. [ABSTRACT FROM AUTHOR]

Background: This study aimed to clarify differences in clinical results, including in patients' joint awareness, between cruciate-substituting (CS) and cruciate-retaining (CR) medial pivot total knee arthroplasty (TKA) over a 10-year follow-up.Methods: A total of 333 TKAs were included in this study. There were 257 cases of CS and 76 cases of CR TKAs. Knee range of motion, Knee Society Score, and radiological outcomes were assessed. The patients' joint awareness was evaluated using the Forgotten Joint Score-12 at the final follow-up. The survival rate with respect to reoperation or revision was analyzed.Results: The mean follow-up period was 10 ± 1.7 years, and the loss to follow-up was 5.4%. All clinical outcomes improved significantly after surgery in both groups (P < .001). Postoperative knee flexion was 118° ± 13° in the CS group and 116° ± 10° in the CR group (P = .10). The mean Forgotten Joint Score-12 scores were 57 ± 27 points in the CS group and 56 ± 28 points in the CR group (P = .59). Ten years after the operation, the survival rates for reoperation were 96.3% in the CS group and 94.2% in the CR group (P = .61), and those for revision were 98.4% and 98.7% in the CS and CR groups, respectively (P = .87). Other postoperative clinical results did not differ between the 2 groups.Conclusion: In this 10-year follow-up study, medial pivot TKA, regardless of polyethylene insert type, showed a high survival rate and good patient awareness of the prosthetic joint. [ABSTRACT FROM AUTHOR]

Abstract Purpose The purpose of this study was to analyze the dynamic kinematics of the mobile medial pivot‐type total knee arthroplasty (MMPTKA) using the three‐dimensional (3D)‐to‐2D registration technique. Methods Cadaveric knees from five humans were used. Computed tomography of the lower limb and preoperative 3D planning for MMPTKA were performed. After performing TKA, passive motion of the knee was observed from a fully extended position to maximum flexion using a flat panel detector. The following parameters were determined: (1) anteroposterior (AP) translations of the medial and lateral most distal points (estimated contact point) of the femoral component, (2) rotational femoral component’s X‐axis (FCX) angle, and (3) rotational insert angle. Paired t‐tests were used to analyze differences in the AP translation between the medial and lateral most distal points of the femoral component as well as differences in the changes in the rotational angle between the FCX and X‐axis of the insert on the tibial component’s axial plane. Results The AP translations of the femoral component’s medial and lateral most distal points were 8.4 ± 2.5 and 13.6 ± 3.3 mm, respectively (p = 0.001). The rotational angles of the FCX and insert were 10.7° ± 4.9° external rotation and 8.9° ± 4.1° internal rotation, respectively (p = 0.004). Conclusions The posterior translation of the lateral side of the femoral component was greater than that of the medial in all cases. Hence, a medial pivot pattern was identified. The femoral component exhibited external rotation throughout knee flexion in all subjects, whereas the mobile insert exhibited internal rotation (opposite pattern relative to the femoral component). This study provides valuable kinematical information of MMPTKA that has not been clear yet.