Medial Pivot Research Articles

Early Improvement in Postoperative Clinical Outcomes without Patellar Resurfacing in Patella-Friendly Design of Medial Pivot TKA.

There is continued debate about the efficacy and indications for patellar resurfacing in total knee arthroplasty (TKA), especially with the emergence of patella-friendly designs. This study aimed to compare the postoperative outcomes in patients undergoing TKA with or without patellar resurfacing using the same implant design. This is a retrospective cohort study of patients who underwent TKA including those with patellar resurfacing (PR group) and those without (NPR group). Demographic data included age, gender, side of surgery, operative time, and body mass index (BMI). Outcomes included preoperative, 2-week, 6-week, and 1-year postoperative Knee Injury and Osteoarthritis Outcome Score and Joint Replacement (KOOS, JR) values along with knee range of motion (ROM). Postoperative complications were recorded. The power analysis with a large effect size indicated that a minimum sample size of 54 was required for Student's t-test and 34 for the paired t-test. A total of 90 medial pivot (MP) TKA were included in this study. There were 30 knees in the PR group and 60 in the NPR group. There was no significant difference between the groups for all demographic data, preoperative and postoperative ROM, and KOOS, JR values at all time points (p > 0.05 for all variables). The KOOS, JR significantly improved in the NPR groups at 2 weeks, 6 weeks, and 1 year postoperatively when compared with the preoperative score and at 6 weeks and 1 year postoperatively in the PR group (p < 0.01). No revisions related to the patellofemoral joint were observed in patients initially undergoing patellar resurfacing. One patient in the NPR group required secondary patellar resurfacing. The patella-friendly MP TKA yielded favorable postoperative outcomes, with or without patellar resurfacing. Improvements in KOOS, JR were observed earlier in the NPR group when compared with the PR group, suggesting that patellar resurfacing may not always be necessary for modern TKA designs. LEVEL OF EVIDENCE: Retrospective cohort study, Level III.

Comparative analysis of medial pivot vs. posterior stabilized total knee arthroplasty in patients with valgus deformed osteoarthritic knees: a retrospective cohort study.

Total knee arthroplasty (TKA) is highly effective for end-stage knee osteoarthritis, providing long-term benefits and anticipated increased prevalence. The study compares Medial Pivot TKA's (MP-TKA) historical success for varus deformities with recent findings suggesting comparable outcomes for valgus deformities. Despite prevalent use of Posterior Stabilized TKA (PS-TKA) for valgus deformities, this research explores the unexplored comparative efficacy of MP-TKA vs. PS-TKA in knee osteoarthritis patients with valgus deformity. This single-centrecohort study focused on 57 knees in 53 patients undergoing TKA for knee osteoarthritis with valgus deformity. Conducted between January 2013 and April 2021, the study compared MP-TKA and PS-TKA. Surgeries adhered to a medial parapatellar approach and modified gap technique, with perioperative interventions for pain, bleeding, and swelling. Outcome measurements included knee joint range of motion, radiographic evaluation, patients-reported outcomes, operative time, blood laboratory tests, estimated blood loss, and postoperative adverse events, and analyzed between the two groups. Postoperative hip-knee-ankle angles showed no significant difference between MP-TKA and PS-TKA. The pie crust technique was similarly used in both groups, and deformity correction showed no significant difference. Range of motion and clinical outcomes, measured by WOMAC and JOA scores, were comparable postoperatively. MP-TKA had a shorter surgical duration (p = 0.01), and PS-TKA exhibited higher estimated blood loss (p = 0.01) without significant complications in either group. This pioneering study compares the outcomes of MP TKA and PS TKA in patients with valgus-deformed osteoarthritic knees. Compared to PS TKA, MP TKA shows a prolonged operative duration and increased blood loss, likely due to the requirement for patellar replacement. However, postoperative range of motion and clinical outcomes are similar. Both groups exhibit favorable midterm clinical results, supporting the viability of MP TKA for valgus deformed knees. The study, consistent in surgical approach, highlights MP TKA's effectiveness for valgus deformities.

Determinants of pivot kinematics in posterior stabilized total knee arthroplasty

BackgroundRestoring 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. MethodsTwelve 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. FindingsAcross 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. InterpretationCentral 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.

Two-Year Outcomes are Equal in Kellgren-Lawrence Osteoarthritis Grades 1-4 after Total Knee Arthroplasty with Medial-Pivot Implants and Kinematic Alignment.

Introduction While risks exist with total knee arthroplasty (TKA) and survivorship is not indefinite, delaying surgery may lead to further deterioration of the knee joint, functional outcomes, and health status. Most studies report that patients with high-grade osteoarthritis (OA) scores have higher satisfaction and functional scores, cautioning against TKA in those with lower OA grades. This study correlates Kellgren-Lawrence (KL) OA scores with outcomes following kinematically-aligned TKA. Methods Preoperative anteroposterior weight-bearing radiographs of 168 patients enrolled in a prospective trial were scored for KL grade. Patients were segregated into two groups: the low-grade OA group had KL scores of 1 or 2, the high-grade OA group had a KL score of 3 or 4. Outcomes as measured with Forgotten Joint Score (FJS), Knee Society Score (KSS), and Range of motion were compared up to 2-years. Results There were 29 subjects with low-grade KL scores and 127 with high-grade KL scores. There were no differences in BMI, age, or gender distribution. The only statistically significant difference was in the preoperative KSS Pain/Motion score, 60.6 in the low-grade OA group vs. 46.4 in the high-grade group (P&lt;0.008). There were no significant differences between the groups in FJS at one or two-year follow-up. There were no differences in KSS Functional or Composite Scores, or in range of motion (ROM) at pre-op, 1-year or 2-years, and in KSS Pain/Motion at 1 or 2-years. Conclusion There were no significant differences in FJS, KSS, and ROM in patients with low- vs. high-grade OA up to 2-year follow-up. Patients with lower grade OA demonstrated substantial improvements in their FJS, KSS scores, and ROM indistinguishable from the higher-grade OA cohort up to 2-years, suggesting no shorter-term downside to earlier intervention with kinematically-aligned medial-pivot (MP) TKA.

Novel Surgical Technique for Total Knee Arthroplasty Integrating Kinematic Alignment and Real-Time Elongation of the Ligaments Using the NextAR System.

This study introduces an innovative surgical approach for total knee arthroplasty (TKA) that combines kinematic alignment (KA) principles with real-time elongation of the knee ligaments through the range of motion, using augmented reality (AR). The novelty of the surgical technique lies in the possibility of enhancing the decision-making process to perform the cut on the tibia as for the KA caliper technique developed by Dr. Stephen Howell. The NextAR is a CT-based AR system that offers the possibility of performing three-dimensional surgical preoperative planning and an accurate execution in the surgical room through single-use infrared sensors, smart glasses, and a control unit. During the preoperative planning, the soft tissue is not considered and only the alignment based on bony reference is ensured. Thanks to the possibility of measuring in real time the elongation of the knee collateral lateral ligaments, the system assists the surgeon in optimizing the cut on the tibia after an accurate resurfacing of the femur as described in the KA surgical technique. The implant used in this novel approach is a medial pivot design (Medacta GMK Sphere) that allows the restoration of the physiological behavior of the software tissue and natural knee kinematics. In conclusion, this novel technique offers a promising approach to TKA, allowing personalized treatment tailored to each patient's unique anatomy and soft tissue characteristics. The integration of KA and real-time soft tissue analysis provided by NextAR enhances surgical precision and outcomes, potentially improving patient satisfaction and functional results.

Comparison of Six-Week, Three-Month, and One-Year Postoperative Clinical Results of Kinematic and Mechanical Alignment in Primary Medial Pivot Total Knee Arthroplasty.

Total knee replacement (TKR) is a common surgical solution for severe osteoarthritis. Kinematic alignment (KA) and mechanical alignment (MA) are two popular techniques. There is ongoing debate over the optimal method, influenced by varying long-term results and a scarcity of data on short-term postoperative outcomes. Early evaluation of these techniques is vital for improving rehabilitation outcomes and ensuring patient satisfaction. Methods: This study retrospectively analyzed outcomes from 71 KA-TKRs and 85 MA-TKRs performed between 2019 and 2021. Knee flexion, visual analog scale (VAS) scores, EuroQol-5d (EQ-5d) quality of life measures, and dependence on walking aids were evaluated. Evaluations were conducted at baseline, six-weeks, three-months, and 12-months postoperatively using two-sample t-tests for continuous data and Pearson's chi-squared test for categorical data. At six-weeks and three-months postoperatively, the KA group exhibited significantly better outcomes in knee flexion (98.6° vs. 90.2° at six-weeks; 114.7° vs. 94.2° at three-months), pain management, and reduced walking aids compared to the MA group. By 12-months, these differences were no longer significant, with both groups showing comparable results in knee flexion, pain scores, and patient-reported outcomes. Conclusion: KA offers substantial short-term advantages over MA for pain relief, increased knee flexion, and independence from walking aids. However, these benefits do not persist at one-year post-surgery, indicating a convergence of outcomes between the two techniques. Larger studies with extended follow-ups are required to determine the long-term implications of these alignment strategies.

Impact of implant positions in total knee arthroplasty on the postoperative knee kinematics of tibial rotation

IntroductionIn total knee arthroplasty (TKA), the implant positions and knee kinematics, as well as the manifestation of medial pivot motion, play pivotal roles in determining postoperative clinical outcomes. The purpose of the current study was to analyze the correlation between knee kinematics, which was measured during TKA and implant positions derived using computed tomography (CT) examination after TKA. MethodsThis study comprised 64 patients (76 knees) who underwent primary TKA between 2015 and 2022. A navigation system was used in TKA procedures, and intraoperative knee kinematics were automatically calculated with it. Utilizing three-dimensional evaluation software, positioning of implants was quantified with CT images taken pre- and post-operatively. Multiple regression analyses were employed to explore the impact of femoral component position (FP) and tibial component position (TP) on knee kinematics, focusing on the extent of tibial rotational motion (TRM) during passive knee motion. ResultsFP affected TRM between knee extension and 90° flexion (p = 0.003, 95 % confidence interval [CI]: 0.315–1.384) and between knee extension and full flexion (p = 0.0002, 95 % CI: 0.654–1.844) after TKA. FP in internal rotation positively affected internal TRM after TKA. TP was not associated with TRM. ConclusionsFindings of the current study suggest that FP in internal rotation positively impacts knee kinematics after TKA.

Biomechanical improvements in gait following medial pivot knee implant surgery

BackgroundTotal knee replacements are used to improve function and reduce pain in patients with advanced osteoarthritis. The medially stabilising implant is designed to mimic a healthy knee. This study aims to provide a comprehensive analysis of the kinematics and kinetics of a medially stabilising knee implant, comparing it to a healthy control group, as well as to its pre-operative state and the contralateral limb. MethodsSixteen total knee replacement patients and ten healthy participants were recruited. Patients underwent testing 4–6 weeks before surgery and repeated the same tests 12 months after surgery. Healthy participants completed the same tests at a single time point. All participants completed three walking trials: kinematics was captured with eight cameras; kinetics with in-ground force plates. Subject-specific musculoskeletal models were developed in OpenSim. Inverse kinematics and inverse dynamics were used to determine gait parameters. Joint angles and joint moments were evaluated using Statistical Parametric Mapping. Patient-reported outcome measures were also collected at both time points. FindingsSpatiotemporal results indicate significant differences in velocity and step length between pre-operative patients and control participants. Differences are observed in the adduction angles between the contralateral and ipsilateral limbs pre-operatively. Postoperatively, there was an increase in the 1st peak flexion moment, reduced adduction moment and reduced internal rotation moment. In PROMs, patients all report improvements in pain levels and high satisfaction levels following surgery. InterpretationsFollowing medial stabilising total knee arthroplasty, patients displayed improved clinical parameters and joint moments reflecting a shift towards more normal, healthy gait.

Medial-pivot total knee arthroplasty enhances tibiofemoral axial rotation stability in weight-bearing mid-range flexion compared to posterior-stabilised system.

Total knee arthroplasty (TKA) stands as a primary intervention for severe knee ailments, yet concerns remain regarding postoperative patient satisfaction and flexion instability. This study aims to evaluate the in-vivo kinematics of medial-pivot (MP) and posterior-stabilised (PS) designs during step-up activity, in comparison to the kinematics of the nonoperated contralateral knee. Sixteen patients with PS-TKA and 14 with MP-TKA were retrospectively examined. Clinical outcomes were assessed using patient-completed questionnaires. Motion during step-up was captured using a dual fluoroscopic system. Statistical analysis was applied to evaluate the in-vivo tibiofemoral six-degree-of-freedom kinematics and articular contact positions between the two groups. Despite being older, patients in the MP group reported higher postoperative subjective scores for weight-bearing functional activities. The axial rotation centres of MP-TKA located on the medial tibial plateau exhibited less variance compared to PS-TKA and contralateral knees. Compared to the contralateral knee (contralateral to medial-pivot [C-MP] or contralateral to posterior-stabilised [C-PS]), the MP group exhibited limited range of motion in terms of anteroposterior translation (MP: 3.6 ± 1.3 mm vs. C-MP: 7.4 ± 2.5 mm, p < 0.01) and axial rotation (MP: 6.6 ± 1.9° vs. C-MP: 10.3 ± 4.9°, p = 0.02), as well as in the PS group for anteroposterior translation (PS: 3.9 ± 1.7 mm vs. C-PS: 7.2 ± 3.7 mm, p < 0.01). The MP group with better postoperative ratings demonstrated a more stable MP axial rotation pattern during step-up activity compared to the PS group, underscoring the pivotal role of prosthetic design in optimising postoperative rehabilitation and functional recovery. Level III.

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

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. 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. 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 ≥ 4mm at early flexion was independently of implant design associated with significantly worse Kujala scores. The incidence of ≥ 4mm AP laxity at any knee angle was however not significantly different between implant designs. 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.

A Novel Ligamentous Complex in the Anteromedial Region of the Knee: A Cadaveric Study.

The medial knee structures have a primary role in stabilizing valgus and rotational stress, which makes them important in assessing the ligament-injured knee globally and choosing the most adequate treatment. To conduct a layer-by-layer dissection of the knee's anteromedial side and provide a qualitative and quantitative description of the anatomy and histology of a ligament in the anteromedial region of the knee, which we have termed the anterior oblique ligament (AOL). Also, to describe the AOL relationship with what we have termed the medial cross-a ligament complex that stabilizes the medial pivot. Descriptive laboratory study. A total of 35 fresh-frozen knees from transfemoral amputations that were exclusively performed for vascular reasons were dissected. Structures were identified after meticulous dissection, respecting the same protocol, measured with a digital caliper rule, and histologically studied for data. The AOL was found in all dissected knees, with a mean length of 31.47 ± 5.06 mm. This structure presented a ligament histology with densely organized collagen fibrils. The medial cross was represented by the superficial medial collateral ligament, AOL (anterior region), and posterior oblique ligament. This study demonstrated the presence of a ligament in the anteromedial region of the knee, termed the AOL. This structure was in the anterior part of a ligament complex-the medial cross. Studying and revisiting the medial compartment can provide important information for understanding joint instability and promoting better results in ligament reconstructions.

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

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. The study included 10 knees that underwent primary TKA using MMPTKA. After TKA, lateral view radiographs of the knee in full extension, 90° of flexionand 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. 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. 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 IV,prospective biomechanical case series study.

Achieving Specified Laxity in a Noncruciate Total Knee: A Laboratory Design Study

BackgroundNoncruciate total knee arthroplasty designs, including ultracongruent, medially congruent, and medial pivot, are gaining increasing attention in total knee arthroplasty surgery. However, there is no consensus for the bearing surface design, whether there should be different medial, lateral, anterior, and posterior laxities, or whether the medial side should be a medial pivot. This study proposes the criterion of reproducing the laxity of the anatomic knee, defined as the displacements and rotations of the femur on the tibia in the loaded knee when shear and torque are applied. The purpose of this study was to determine the ideal tibial radii to achieve that goal. MethodsThe femoral component was based on the average knee from 100 mild arthritic knee scans. There were 8 tibial components that were designed with different sagittal radii: antero-medial, antero-lateral, postero-medial, and postero-lateral. Radii were defined as the percent height reduction from full conformity with the femoral profile. Components were 3-dimensional–printed. A test rig was constructed where the tibial component was fixed and shear and torque were applied to the femoral component. Displacements and rotations of the femoral component were measured at 0 and 45° of flexion, the latter representing any flexion angle due to the constant femoral sagittal radius. ResultsDisplacements ranged from 0 to 11 mm, and rotations ranged from 1 to 11°. Anterior femoral displacements were higher than posterior due to the shallow distal-anterior femoral profile. The final femoral and tibial components with the most closely matched anatomic laxity values were designed and tested. ConclusionsA steeper distal-anterior femoral radius was an advantage. High medial-anterior tibial conformity was important. However, on the lateral side, the posterior sagittal tibial radius had to be shallower than ideal to allow femoral rollback in high flexion. This meant that the posterior laxity displacements on the lateral side were higher than anatomic, and there was no guidance for lateral femoral rollback.

Good Short-Term Survivorship of Constrained Condylar Revision Knee Implants With Medial Pivot Kinematics: A Level IV Retrospective Study

BackgroundThe need for revision total knee arthroplasty surgery is increasing worldwide, and, in many cases, a constrained implant is required to provide joint stability. The purpose of this study was to examine the early loosening and functional outcome of a novel constrained condylar (CCK) revision total knee system designed to have medial pivot (MP) kinematics. MethodsA retrospective cohort study was performed, collecting clinical data from all patients who underwent revision total knee arthroplasty using a novel MP CCK system with a minimum four-year clinical follow-up. Patient demographics, survivorship, complications, and Forgotten Joint Score were analyzed based upon chart review. ResultsThere were 49 patients available for follow-up, who had a 100% survivorship free of aseptic loosening. All-cause revision survivorship was 92%. There were 4 patients who subsequently underwent rerevision. The causes for rerevision included periprosthetic joint infection in 2 patients, coronal plane instability in one patient, and a traumatic knee dislocation in one patient. There were 45 patients who completed the Forgotten Joint Score, who had an average of 49.8 (± 32.8, range 6.25 to 100). ConclusionsAt 4 years, mid-term follow-up, this novel CCK revision total knee system designed to have MP kinematics had good patient-reported outcomes with no revision for aseptic loosening. Future studies should evaluate the mid- and long-term survivorship of this innovative implant.

Comparison of postoperative clinical outcome in medial-pivotal and gradually reducing radius design cruciate-retaining total knee arthroplasty-A multicenter analysis of propensity-matched cohorts.

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. 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. 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. The MP group showed better postoperative knee flexion, midrange AP knee stability, and shorter surgery duration. Level III, retrospective comparative study.

Cementless medial pivot design demonstrates equal or better outcomes compared to cementless cruciate-retaining design following total knee arthroplasty

IntroductionTraditional total knee arthroplasty (TKA) designs fail to reproduce physiologic knee kinematics, which can contribute to patient dissatisfaction. In an attempt to restore more normal knee kinematics, the medial pivot (MP) design may improve knee function and stability as well as patient satisfaction. A limited number of studies have compared postoperative outcomes of exclusively cementless Cruciate-Retaining (CR) TKAs to cementless MP TKAs. We aimed to compare: (1) 90-day, 1-year, and 2-year complications and revisions, (2) preoperative and postoperative range of motion (ROM), (3) Knee Injury and Osteoarthritis Outcome (KOOS-JR), and (4) visual analog scale (VAS) pain scores at 3-month, 6-month, 1-year, and 2-years. MethodsA retrospective analysis was performed to identify all patients who had previously undergone a TKA at our institution and compare a cementless CR system to a cementless MP design. Categorical variables, including demographics, comorbidities, and complications utilized Chi-square tests in bivariable analysis. Continuous variables, such as age, were compared using Student's t-tests. Significance was defined as p < 0.05. ResultsCementless CR and cementless MP cohorts showed low profiles of postoperative complications and favorable patient-reported outcome measures (PROMs). The MP cohort had lower VAS pain at 1-year (1.70 vs. 3.76, p < 0.001) and 2-years (1.43 vs. 2.60, p < 0.001) and higher ROM at 3-months (118 vs. 100, p < 0.001), 6-months (113 vs. 103, p < 0.0001), and 1-year (117 vs. 110, p = 0.02), respectively. ConclusionThis study is the first comparison of postoperative outcomes between a cementless CR TKA and cementless MP TKA designs. Implant design and fixation type are vital components influencing patient satisfaction after TKA. Pain scores and range of motion favored the cementless MP cohort in comparison to the cementless CR cohort.

Kinematic Performance of Medial Pivot Total Knee Arthroplasty

BackgroundTotal knee arthroplasty (TKA) implants have continued to evolve to accommodate new understandings of knee mechanics. The medial-pivot implant is a newer design, which is intended to limit anterior-posterior translation in the medial compartment while allowing lateral compartment translation. However, evidence for a generalized medial-pivot characteristic across all activities is limited. The purpose of the study was to quantify and compare in vivo knee joint kinematics using high-speed stereo radiography during activities of daily living in patients who have undergone a TKA with a cruciate sacrificing medial-pivot implant to age-matched and sex-matched native controls. MethodsFifteen participants (7 patients, 4 women, mean age 70 years and 8 nonsymptomatic controls, 4 women, mean age 64 years) performed 6 functional tasks in high-speed stereo radiography: deep-knee lunge, chair rise, step down, gait, gait with 90° turn, and seated knee extension. Translational differences between groups (surgical versus control) were assessed for the medial and lateral condyle, while pivot location was normalized to subject-specific tibial plateau geometry. ResultsThe surgical cohort displayed a more constrained medial condyle that provided greater stability of the medial compartment and did not result in the paradoxical anterior translation at mid-flexion angles during weight-bearing activities, but was associated with less condylar translation than native knees. Additionally, the transverse tibial pivot location occurs most commonly in the middle third of the tibial plateau and secondarily on the medial third. ConclusionsSome variability in pivot location occurs between activities and is more in nonsymptomatic, native knee controls.

Clinical and Functional Outcomes of Kinematic Aligned Total Knee Arthroplasty with a Medial Pivot Design: Two-Year Follow-Up

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.

Equivalence of clinical and radiological outcomes in cruciate-retaining and cruciate-substituting total knee arthroplasty with medial pivot knee: A comparative study

IntroductionTotal knee arthroplasty (TKA) has been recognized as the most efficacious surgical intervention for individuals suffering from advanced arthritis; however, there is ongoing debate on the technical details of the procedure. It remains unknown whether preservation of the posterior cruciate ligament (PCL) significantly affects the mid-to long-term performance of ADVANCE® medial-pivotal (AMP) knee implants to enhance patient satisfaction. The hypothesis of this study was to investigate whether the preservation of the PCL has a substantial impact on the functional outcomes of medial pivot (MP) implants in patients undergoing TKA. Therefore, this study aimed to compare the midterm clinical and radiographic outcomes of cruciate-retaining (CR) and cruciate-substituting (CS) TKA using MP prostheses. MethodsWe included 376 consecutive patients who underwent unilateral TKA between January 2011 and April 2014. Follow-up evaluations were conducted in April 2021. After propensity score matching analysis, clinical and radiological outcomes and complication rates were compared between patients in the CR and CS groups. ResultsThe postoperative outcomes in the two groups significantly improved the preoperative conditions of the patients (all p > 0.05). The postoperative outcomes (WOMAC score, p = 0.517; KSS, p = 0.107; KSFS, p = 0.240; ROM, p = 0.795; FJS, p = 0.822) and radiographic outcomes (preoperative FTA, p = 0.997; postoperative FTA, p = 0.646; aLDFA, p = 0.094; aMPTA, p = 0.970; PTS, p = 0.243) were comparable between the two groups. The complication and revision rates between the groups were not statistically significant (p = 0.34). The Kaplan–Meier cumulative survival of patients in the CRTKA and CSTKA groups was 100 % and 98.6 %, respectively. ConclusionsThis study supports the hypothesis that when MP prostheses are used, both CR and CS procedures achieve equally good mid-to long-term clinical and radiographic outcomes and complication rates. These findings suggest that PCL preservation may not significantly affect the overall performance of MP implants in patients undergoing TKA.

Medial Ball-in-Socket Posterior Cruciate-Sacrificing Total Knee Arthroplasty: Clinical, Functional and Radiographic Evaluation of 100 Consecutive Implants

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.