Medial Pivot Total Knee Arthroplasty Research Articles

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.

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 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 the student 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-week, 6-week, and 1-year postoperatively when compared to the preoperative score and at 6-week 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 to the PR group, suggesting that patellar resurfacing may not always be necessary for modern TKA designs.

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.

Association Between Overhang of the Posterior Femoral Condyle and Restricted Postoperative Knee Flexion Related to Patient-Reported Stiffness in Medial-Pivot Total Knee Arthroplasty

BackgroundThe primary aim of this study was to investigate the association between the posterior longitudinal overhang in the femoral condyle (PLOF) in medial-pivot total knee arthroplasty (TKA) and a change in knee flexion angle (change in flexion). MethodsThis retrospective cohort study included 148 knees undergoing medial-pivot TKA for medial knee osteoarthritis. The primary outcome was the change in flexion (c-flexion) preoperatively and 1-year postoperatively. The component positions were evaluated using 3-dimensional measurements, where the PLOF was measured for each medial and lateral femoral condyle. The secondary outcome was the Western Ontario and McMaster Universities Osteoarthritis Index scores taken preoperatively and 2 years postoperatively. A multivariate regression analysis was performed to determine predictors of c-flexion and risk factors for negative c-flexion (less than 0°). Furthermore, a receiver operating characteristic curve was utilized to determine the threshold for negative c-flexion. ResultsThe mean c-flexion was −3.2° ± 8.7, and lateral PLOF was significantly associated with c-flexion (β = −0.52; P < 0.001). Larger preoperative flexion angles (odds ratio, 1.10; P < 0.001) and larger lateral PLOF (odds ratio, 1.69; P = 0.001) were risk factors for negative c-flexion, with thresholds of 129° and 1.1 mm, respectively (sensitivity, 0.79; specificity, 0.72). Additionally, patients who had negative c-flexion (n = 91) demonstrated less improvement in preoperative and 2-year postoperative Western Ontario and McMaster Universities Osteoarthritis Index stiffness subscores than patients who had positive c-flexion (0° or more; n = 57) (P = 0.01). ConclusionsA larger lateral PLOF was associated with decreased and negative c-flexion after medial-pivot TKA. Patients who had negative c-flexion demonstrated less improvement in knee stiffness. Surgical strategies aimed at minimizing lateral PLOF may enhance postoperative knee flexion and overall patient outcomes in medial-pivot TKA.

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.

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.

Sitting Sideways Causes Different Femoral-Tibial Rotations in Each Knee.

Purpose According to a previous study, asymmetrical kneeling, such as sitting sideways, does not exhibit asymmetrical movements. Rotational analyses of each femur and tibia help explain why rotational knee kinematics while sitting sideways do not exhibit asymmetrical movement. We aimed to assess the rotation of the femur and tibia in normal knees while sitting sideways. Methods Each volunteer sat sideways under fluoroscopy. Two-dimensional and three-dimensional registration techniques were used. After evaluating the femoral rotation angle relative to the tibia at each flexion angle, the femoral and tibial sole rotation angles at each flexion angle were compared between the ipsilateral and contralateral knees. Results While sitting sideways, both knees showed femoral external rotation relative to the tibia with flexion. In the ipsilateral knees, the femurs exhibited an external rotation of 26.3 ± 8.0°, from 110° to 150° of flexion. Conversely, the tibia exhibited an external rotation of 12.2 ± 7.8°, from 110° to 150° of flexion. From 110° to 150° of flexion, femoral external rotation was significantly larger than tibial external rotation. In the contralateral knees, the femurs exhibited an internal rotation of 23.8 ± 6.3°, from 110° to 150° of flexion (110°, p < 0.001; 120°, p < 0.001; 130°, p < 0.001; 140°, p < 0.001; and 150°, p < 0.001). Contrastingly, the tibia exhibited an internal rotation of 30.4 ± 8.8°, from 110° to 150° of flexion, which was significantly larger than femoral internal rotation (110°, p = 0.002; 120°, p < 0.001; 130°, p < 0.001; 140°, p < 0.001; and 150°, p < 0.001). Conclusions Although bilateral knees exhibited femoral external rotation relative to the tibia while sitting sideways, the ipsilateral and contralateral knees showed femoral and tibial sole rotations in opposite directions. In particular, the contralateral knees might show a strained movement because both femurs and tibias exhibited internal rotation with flexion. Patients who have undergone guided-motion total knee arthroplasty (TKA) or medial-pivot TKAs might be advised to avoid sitting sideways.

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.

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.

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.

PCL retained is safe in medial pivot TKA—a prospective randomized trial

PurposeMedial pivot (MP) designs resemble native knee kinematics and restore the “natural” kinematics of a knee after total knee arthroplasty (TKA). However, whether to preserve or resect the posterior cruciate ligament (PCL) is still under debate. We inquired whether sacrificing the PCL would improve range of motion, functional outcomes, and limb alignment compared to preserving the PCL in TKA using medial pivot implants (MP-TKA).MethodsThis prospective, double-blinded, randomized controlled trial consisted of 33 patients (66 knees) undergoing bilateral simultaneous MP-TKA. In one knee, a PCL preservation technique was performed, and in the contralateral knee, the PCL was resected. The primary outcome was postoperative range of motion (ROM). The secondary outcomes were visual analogue scale (VAS) score for knee pain at walking, Knee Injury and Osteoarthritis Outcome Score for symptoms (KOOS-S) and quality of life (KOOS-QoL), Oxford knee score (OKS), and Forgotten Joint Score (FJS), and measurement of the mechanical femoral-tibial axis (mFTA) on X-ray images. All patients were followed up for a minimum of 2 years after surgery.ResultsPatients who underwent MP-TKA with PCL preservation had a similar ROM at 2 years (125.45 ± 7.00 vs. 126.21 ± 6.73, p = 0.65) as those who underwent MP-TKAs with PCL resection. There was also no difference in VAS score (1.94 ± 0.79 vs. 2.00 ± 0.71, respectively, p = 0.51), OKS (39.97 ± 2.01 vs. 39.67 ± 2.03, respectively, p = 0.52), KOOS-S (84.41 ± 3.77 vs. 84.19 ± 3.57, respectively, p = 0.92), KOOS-QoL (82.94 ± 4.76 vs. 82.75 ± 4.70, respectively, p = 0.84), or FJS (72.66 ± 8.99 vs. 72.35 ± 8.64, respectively, p = 0.76) at the 2-year follow-up. No difference in the measurement of the mFTA was found between the two groups (180.27 ± 2.25 vs. 181.30 ± 2.13, respectively, p = 0.59).ConclusionThis study demonstrated that both medial pivot TKA with PCL preservation and PCL resection achieved excellent results. There was no difference at the 2-year follow-up in terms of postoperative ROM, patient-reported outcomes, or radiographic evaluation.Level of EvidenceTherapeutic study, Level I.

Long-Term Follow-Up of Medial Pivot Total Knee Arthroplasty: A Systematic Review of the Current Evidence

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.

Short-term clinical and radiological comparisons between two Medial Pivot Total Knee Arthroplasty implants with different geometries.

Different total knee arthroplasty (TKA) implants were created for the treatment of severe symptomatic gonarthrosis and Medial Pivot TKA (MP TKA) seem to reproduce the normal kinematics of the knee. We compare two different prosthetic designs of MP TKA in order to identify whether there is a difference between the two in terms of degree of patient satisfaction. Methods: A total of 89 patients were analyzed. A group of 46 patients who benefited from a TKA with the Evolution® prosthesis and one of 43 patients who received a TKA with the Persona® prosthesis. KSS, OKS, FJS and the ROM were analyzed at follow up. The values of KSS and OKS were similar between the two groups (p>0,05). Our statistical analysis revealed a statistically significant increase (p <0.05) in ROM in the Persona® group and in FJS in the Evolution® group. No radiolucent lines were observed in both groups at the radiological final follow-up. Conclusions: MP TKA models analysed are a valuable tool to achieve satisfactory clinical outcomes. This study demonstrates that the FJS is an important score for the evaluation of patient's satisfaction: a ROM's limitation can be accepted by the patient in exchange for a more natural perceived knee.

Long-term clinical results of alumina ceramic medial pivot total knee arthroplasty: a 10-year follow-up study

BackgroundThe 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.MethodsThe 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.ResultsThe 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.ConclusionsDuring a minimum 10-year follow-up period, the present model of alumina medial pivot total knee arthroplasty showed good clinical outcomes and survival rates.

Medial pivot total knee arthroplasty: Mid-term results.

This study aims to evaluate the mid-term results of patients who underwent medial pivot total knee arthroplasty at a single center. A total of 304 knees of 236 patients (40 males, 196 females; mean operation age and standard deviation : 66,64 ±7,09 years; range, 45 to 82 years) treated with medial pivot total knee prosthesis in our center between January 2010 and December 2014 were retrospectively analyzed. The American Knee Society Score, Oxford Knee Score, and especially flexion angles were recorded during pre- and postoperative follow-up. Of the operated knees, 71.2% were unilateral and 28.8% were bilateral. The mean follow-up was 79.30±14.76 months. The postoperative results with the Functional Score, Knee Score, Oxford Score, Total Knee Society Score, and flexion angles were significantly higher compared to baseline (p<0.01). All postoperative scores were significantly lower inpatients aged ≥65years, compared to those aged <65 years (p<0.01). In patients who underwent resection of anterior and posterior the cruciate ligaments, only the mean flexion angles were found to increase (p<0.01). Our study results suggest that medial pivot knee prostheses are reliable in the mid-term and provide favorable results in terms of function and patient satisfaction. Level of Evidence: Level IV retrospective study.

Larger Medial Contact Area and More Anterior Contact Position in Medial-Pivot than Posterior-Stabilized Total Knee Arthroplasty during In-Vivo Lunge Activity

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.

Medial stability and lateral flexibility of the collateral ligaments during mid-range flexion in medial-pivot total knee arthroplasty patients demonstrates favorable postoperative outcomes.

The objectives of the present study were to investigate the length change in different bundles of the superficial medial collateral ligament (sMCL) and lateral collateral ligament (LCL) during lunge, and to evaluate their association with Knee Society Score (KSS) following medial-pivot total knee arthroplasty (MP-TKA). Patients with unilateral MP-TKA knees performed a bilateral single-leg lunge under dual fluoroscopy surveillance to determine the in-vivo six degrees-of-freedom knee kinematics. The contralateral non-operated knees were used as the control group. The attachment sites of the sMCL and LCL were marked to calculate the 3D wrapping length. The sMCL and LCL were divided into anterior, intermediate, and posterior portions (aMCL, iMCL, pMCL, aLCL, iLCL, pLCL). Correlations between lengths/elongation rate of ligament bundles from full extension to 100° flexion and the KSS were examined. The sMCL and LCL demonstrated relative stability in length at low flexion, but sMCL length decreased whereas LCL increased with further flexion on operated knees. The sMCL length increased at low flexion and remained stable with further flexion, while the LCL length decreased with flexion on the contralateral non-operated knees. The lengths of aMCL, iMCL, and pMCL showed moderate (0.5 < r < 0.7, p < 0.05) negative correlations with the KSS, and the lengths of aLCL, iLCL, and pLCL were positively correlated with the KSS at mid flexion on operated knees (p < 0.05). The elongation rates of aLCL, iLCL, and pLCL were negatively correlated with the KSS at high flexion on operated knees (p < 0.05). However, no significant correlations between the length of different bundles of sMCL or LCL with KSS were found on contralateral non-operated knees. The elongation pattern of sMCL/LCL on MP-TKA knees showed differences with contralateral non-operated knees. The sMCL is tense at low to middle flexion and relaxed at high flexion, while LCL is relaxed at low to middle flexion and tense at high flexion following MP-TKA. Medial stability and proper lateral flexibility during mid flexion were associated with favorable postoperative outcomes in MP-TKA patients. In contrast, lateral relaxation at deep flexion should be avoided when applying soft-tissue balancing in MP-TKA. Level III.

Intraoperative femoral rotational kinematics are similar in varus and valgus knees during medial pivot total knee arthroplasty

BackgroundMedial-pivot type total knee arthroplasty is designed to reproduce physiological femoral rotational kinematics during knee flexion; however, its rotational kinematics in valgus knees remain unknown. This study's hypothesis is that its kinematics show the similar medial pivot motion in valgus knees as in varus knees. MethodsThis retrospective study included 50 cases of primary medial-pivot type total knee arthroplasty performed with navigation for knee osteoarthritis. Cases were grouped as valgus (n = 20) or varus (n = 30). In valgus knees, surgeons used preoperative manual testing to confirm that alignment was correctable. They evaluated femoral rotational kinematics at maximum extension, 30°, 60°, 90°, and maximum flexion, using a navigation system, both before and after implantation. Finally, intraoperative rotational kinematics, postoperative patient-reported outcomes, and knee range of motion were compared between the two groups. FindingsBefore implantation, both valgus and varus knees displayed external femoral rotation relative to the tibia during knee flexion. The rotation magnitude was significantly larger in varus knees at 60°, 90°, and maximum flexion angles compared to valgus knees (P < 0.05). In contrast, after implantation, both groups displayed external femoral rotation of 12–13° during knee flexion with no significant differences between the two groups at any knee flexion angle tested (P > 0.05). Short-term clinical outcomes were comparable between valgus and varus knees. InterpretationPostoperatively, medial-pivot type total knee arthroplasty for knee osteoarthritis resulted in external femoral rotation during knee flexion. Notably, this occurred even in valgus knees with good short-term clinical outcomes.