Medial Pivot Research Articles

Kinematics and center of axial rotation during walking after medial pivot type total knee arthroplasty

PurposeIn recent years, the medial pivot (MP) type total knee arthroplasty (TKA) implant has been developed and marketed for achieving more natural kinematics with MP. However, little is known about the pivot pattern during walking after MP type TKA. This study aimed to determine the kinematics and center of axial rotation during walking after MP type TKA.MethodsThis randomized prospective study enrolled 40 patients with MP type TKA, 20 with cruciate-substituting TKA (MP-CS group), 20 with posterior-stabilized TKA (MP-PS group), and 10 healthy volunteers (control group). The kinematics and center of axial rotation during overground walking were measured by a three-dimensional motion analysis system. The six-degrees-of-freedom kinematics of the knee were calculated by the point cluster method.ResultsThe amount of change in knee flexion in early stance phase was significantly lower in the MP-CS and MP-PS groups than in the control group. The femur showed anterior translation during early stance phase in all three groups. The median center of axial rotation in the transverse plane was predominantly on the lateral side of the knee during stance in all groups.ConclusionsKinematics during gait are thought to be determined by physical posture, the kinetic chain during weight-bearing, and the kinematic features of adjacent structures, such as the behavior of the biarticular muscles. MP-CS and MP-PS did not necessarily induce rotational motion centered on the medial ball-in-socket component during walking; translational and lateral pivoting movements were also observed. Long-term follow-up is needed to monitor for polyethylene wear and implant loosening.

Comparative study on mid- and long-term clinical effects of medial pivot prosthesis and posterior-stabilized prosthesis after total knee arthroplasty

ObjectiveThe purpose of this study was to explore the mid-and long-term clinical effects of Chinese patients with medial pivot (MP) prosthesis and posterior-stabilized (PS) prosthesis after total knee arthroplasty (TKA), to provide a reference for the recommendation of clinical prostheses.MethodsA retrospective analysis of 802 patients who received TKA was performed from June 2010 to December 2013. A total of 432 patients received a MP prosthesis (MP group) and 375 patients received a PS prosthesis (PS group). Postoperative range of motion (ROM), clinical scores including the knee scoring system (KSS), the Western Ontario and McMaster Universities osteoarthritis index (WOMAC), the forgotten joint score (FJS), and postoperative complications were compared between the two groups.ResultsA total of 527 patients were followed up, including 290 in the MP group and 237 in the PS group. Both groups achieved satisfactory results in terms of KSS score, WOMAC score, and postoperative ROM, which were significantly improved compared with those before surgery, but the difference between the groups was not statistically significant (P > 0.05). The FJS scores of the MP group and the PS group were satisfactory and no significant difference was observed (P = 0.426). Postoperative complications occurred in 5 and 11 patients in the MP group and PS group, respectively.ConclusionThe clinical results of TKA with MP or PS in Chinese patients at mid- and long-term are encouraging, and no significant differences were observed between the two types of prostheses. Studies have also shown that both prostheses are safe for Chinese patients.

A retrospective comparison of the effect of eMP CS and traditional PS prosthesis on ERAS of total knee arthroplasty

Introduction:The theoretical advantage of medial pivot (MP) knee was thought to justify and replicate the natural knee motion, however, rarely have the comparisons between different designed prosthesis on the enhanced recovery after surgery (ERAS) of TKA can be available. We compared the effect of using Evolution Medial Pivot(eMP) knee system cruciate-substituting (CS) prosthesis and traditional posterior-stabilized(PS) prosthesis on the enhanced recovery after surgery (ERAS) of TKA in order to have a profound understanding of the clinical effects of medial pivot prosthesis.Hypotheses:eMP-CS prostheses can help patients to achieve better recovery after TKAMethods:This study was a retrospective comparison between 2 groups of patients having unilateral TKA(48MP-CS-TKA vs 52 PS-TKA) from Jan 2019 to Mar 2020. The main factors were compared in 2 groups, including Visual Analogue Scale(VAS) pain score,HSS score,FJS-12,range of motion(ROM) and incidence of perioperative complications,as well as overall satisfaction.Results:The VAS score was significantly lower at 1 week,6weeks,3 months and 6 months postoperation than preoperation in two groups(P＜0.05).The HSS score was significant higher at 1 week,,6weeks,3 months and 6 months postoperation than preoperation in two groups (P＜0. 05).The range of motion of knee joint was more than 90° at 1 week after operation in both groups. The recovery of ROM was satisfactory at the early stage,and the ROM increased further with time.There was no statistical difference in VAS,HSS and ROM between two groups in 1 week,6 weeks,3 months and 6 months postoperatively(P＞0.05).In the last follow-up,“Climbing stairs” and “Standing from low sitting position” were the very condition in which the eMP group scored higer.None statistical difference in FJS-12 total score was found between two groups. No significant difference in perioperative complication incidence and blood transfusion rate,and patient-reported satisfaction were observed between two groups(P＞0. 05).Conclusion:Both eMP-CS prostheses and traditional PS prostheses can help to achieve ERAS after TKA.All patients get a satisfying knee function,and the incidence of perioperative complications was low. Nevertheless,it is more natural for eMP-CS prostheses patients to walk stairs and stand up,but no significant difference in patient-reported satisfaction was observed between eMP-CS prostheses and tradional PS prostheses.

Résultats à court terme comparant les prothèses totales de genou de type médial pivot implantées avec alignement cinématique versus mécanique : étude cas-témoins

IntroductionThe kinematic alignment (KA) technique for total knee arthroplasty (TKA) and the medial pivot (MP) component design are two options promoting a physiologic prosthetic knee kinematics when used in combination that could improve TKA outcomes. Case-control study is initiated to compare the 1-year radio-clinical outcomes between kinematic alignment medial pivot total knee arthroplastiy (KA MP-TKAs) and mechanical alignment medial pivot total knee arthroplastiy (MA MP-TKA). Goal of a study was to answer the following questions: do KA MP-TKAs patients have improved functional outcomes compared to MA MP-TKAs patients? (Q1); do prosthetic knee and lower limb alignments differ between KA and MA patients (Q2)? And does kinematic implantation of MP TKA has higher risk of reoperations and revisions (Q3)? Material and methodsA case-control study was carried out to compare the 1-year clinical and radiographic outcomes between 24 consecutive KA-TKA patients and 24 matched MA-TKA patients. All patients had implantation with manual instruments and a cemented medial pivot TKA with excision of the PCL. All data were collected prospectively, and outcome scores were patient reported. ResultsKA patients had superior values in Forgotten Joint Score (FJS) at 1-year (KA 77 vs. MA 51) (p=0.05) follow-up. After one year, KA patients scored better in objective section of the new Knee Society Score (KSS) (p=0.02), and in sport section of the Knee Osteoarthritis Outcome Score (KOOS) (p=0.01). Eleven out of 24 patients (46%) in KA group and 7/24 patients (29%) in MA group had limb alignment out of 180±3°, whereas 17/24 (70%) of KA patients, and 14/24 (58%) of MA patients had orientation of tibial component with more than 3 of varus. No reoperation or revision occurred in either group. Discussion/conclusionThe KA of MP-TKA design seems to have a good efficacy at early-term, with some 1-year functional performance higher to the ones from MA MP-TKAs. Further research is needed to define if those early results will last over time. Level of evidenceIII, case-controlled study.

Which one restores in vivo knee kinematics effectively-medial or lateral pivot?

IntroductionTotal knee arthroplasty (TKA) usually provides good pain relief and improved function but has generally been unable to fully restore normal knee kinematics. Does Medial or Lateral Pivot TKA designs guide us to native knee kinematics needs to be elucidated? MethodsKinematic assessment of 13 knees with Medial Pivot TKA and 13 knees with Lateral Pivot TKA was done. The subjects were asked to perform step-up and weight bearing deep knee bend exercise under fluoroscopy for kinematic assessment. Patellar Tendon Angle (PTA) was measured after correcting f luoroscopic images for distortion against Knee Flexion Angle (KFA). ResultsDuring the weight bearing deep knee bend, the average active maximum flexion achieved with Medial Pivot design was 113.8 ͦ as compared to 102.9 ͦ with Lateral Pivot design. There was no significant difference in PTA in step up and deep knee bend exercise between both the designs. ConclusionThe kinematic assessment of both the Medial and Lateral Pivot TKA designs revealed linear trend of PTA with increasing KFA as described for normal knee. Both the designs were able to achieve functional knee range of motion.

Abnormal knee kinematics caused by mechanical alignment in symmetric bicruciate-retaining total knee arthroplasty are alleviated by kinematic alignment

BackgroundBicruciate-retaining total knee arthroplasty (BCR-TKA) was developed to maintain anterior cruciate ligament function and thus reproduce natural knee kinematics postoperatively. Traditional surgical techniques, however, may cause several complications secondary to kinematic conflict and ligament overtension. The objective of this study was to use a computer simulation of symmetric BCR-TKA to evaluate the effects of alternative surgical techniques on knee kinematics and ligaments. MethodsA musculoskeletal computer model of a healthy knee was constructed and was used to simulate a BCR model with mechanical alignment (MA). Five adjusted models were investigated, characterized, respectively, by kinematic alignment (KA), two degrees increased tibial slope, two-millimeter distal setting of the tibial component, and an undersized femoral component with either MA or KA. ResultsAll models exhibited a normal femoral position against the tibia at knee extension, with no anterior paradoxical motion during mid-flexion. The healthy knee model showed medial pivot motion and rollback. In contrast, the BCR MA model demonstrated abnormal bi-condylar rollback with excessive tensions of the lateral collateral ligament and posterior cruciate ligament during knee flexion, whereas the undersized femoral model with MA partly reduced both tensions. The BCR KA model retained relatively physiological kinematics and suppressed excessive ligament tensions. However, no adjusted model completely reproduced healthy knee conditions. ConclusionsThe BCR MA model showed abnormal biomechanics due to kinematic conflict between the retained ligaments and the replaced joint surface. Surgeons using symmetric BCR-TKA should consider using the KA method to achieve sufficient ligament laxity throughout knee flexion.

Clinical and radiological results of a stemmed medial pivot revision implant in aseptic total knee revision arthroplasty

BackgroundConstraint choice in revision total knee arthroplasty depends on the stability of the collateral ligaments and on the severity of bone loss, but the least degree of constraint necessary is recommended. The purpose of this retrospective matched-paired study was to compare clinical results, radiographic outcome and the survival of a stemmed medial pivot revision implant in aseptic revision TKA vs. medial pivot implant in primary TKA. MethodsRecords were reviewed for 69 cases of aseptic revision TKA using Advance® Medial Pivot Stemmed Revision Knee system between 2002 and 2016. These patients were then matched in a 1:2 ratio control group of patients who received a primary TKA with Advance® Medial Pivot system. American Knee Society Score and Visual Analogue Scale pain score were recorded. Alignment, loosening, and incidence of radiolucent lines were evaluated on X-rays. Implant survival was assessed by Kaplan–Meier survival analysis. ResultsThe primary TKA group had significant superior AKSS clinical and functional score at baseline (52.3 and 68.2 points, respectively) and at last follow up (84.6 and 68.6 points) compared with the revision TKA group (47.9 and 40.9 points; 78.4 and 59.9 points; P < 0.05). No significant difference was observed in the mean change from baseline to last follow up of AKSS score between the two groups (P > 0.05). Radiographical outcome and implant survival were similar in the two groups (P > 0.05). ConclusionThe authors support the use of this revision system in knees with collateral ligaments competence and mild-to-moderate bone defect.

Short-term follow-up of kinematically vs. mechanically aligned total knee arthroplasty with medial pivot components: A case-control study

IntroductionThe kinematic alignment (KA) technique for total knee arthroplasty (TKA) and the medial pivot (MP) component design are two options promoting a physiologic prosthetic knee kinematics when used in combination that could improve TKA outcomes. Case-control study is initiated to compare the 1-year radio-clinical outcomes between kinematic alignment medial pivot total knee arthroplasty (KA MP-TKAs) and mechanical alignment medial pivot total knee arthroplasty (MA MP-TKA). Goal of a study was to answer the following questions: Do KA MP-TKAs patients have improved functional outcomes compared to MA MP-TKAs patients? (Q1); Do prosthetic knee and lower limb alignments differ between KA and MA patients (Q2)? And does kinematic implantation of MP TKA has higher risk of reoperations and revisions (Q3)? Material and methodsA case-control study was carried out to compare the 1-year clinical and radiographic outcomes between 24 consecutive KA-TKA patients and 24 matched MA-TKA patients. All patients had implantation with manual instruments and a cemented medial pivot TKA with excision of the PCL. All data were collected prospectively, and outcome scores were patient reported. ResultsKA patients had superior values in Forgotten Joint Score (FJS) at 1-year (KA 77 vs. MA 51) (p=0.05) follow-up. After one year KA patients scored better in objective section of the new Knee Society Score (KSS) (p=0.02), and in sport section of the Knee Osteoarthritis Outcome Score (KOOS) (p=0.01). Eleven out of 24 patients (46%) in KA group and 7/24 patients (29%) in MA group had limb alignment out of 180°±3°, whereas 17/24 (70%) of KA patients, and 14/24 (58%) of MA patients had orientation of tibial component with more than 3° of varus. No reoperation or revision occurred in either group. Discussion/ConclusionThe KA of MP TKA design seems to have a good efficacy at early-term, with some 1-year functional performance higher to the ones from MA MP TKAs. Further research is needed to define if those early results will last over time. Level of evidenceIII, case-controlled study.

Biomechanical analysis on total knee replacement patients during gait: Medial pivot or posterior stabilized design?

BackgroundTotal Knee Replacement surgery restores joint function in patients with advanced osteoarthritis. There are several prostheses available based on different mechanisms, which guarantee knee stability during Activities of Daily Living. The aim of this study is to compare ball-in-socket (or Medial Pivot) and post-cam mechanisms to detect possible differences in terms of biomechanical parameters between these two prosthesis designs and to evaluate which design is closer to physiological biomechanics. MethodsA kinematics, kinetics and electromyography lower limb analyses were performed during gait on sixty subjects: twenty with Medial Pivot prosthesis, twenty with posterior stabilized prosthesis and twenty healthy subjects to obtain a physiologic reference. FindingsTotal Knee Replacement gait pattern for both patient groups were characterized by reduced walking speed, reduced stride length and increased stance time respect to control group. Comparison between Medial Pivot and Posterior Stabilized groups showed a reduction of knee flexion and flexor moment in patients with ball-in-socket mechanism. A prolonged muscular activity of rectus femoris was observed in Medial Pivot patients compared to Posterior Stabilized and control groups. Interpretation“Stiff knee pattern” mechanism was showed for both patient groups but more enhanced in Medial Pivot patients. Even though the Posterior Stabilized design introduces the non-physiological paradoxical motion and the Medial Pivot design seems to better reproduce the physiological condylar movement as gait analysis parameters, including kinematics, kinetics and electromyographic parameters were closer to control group and, in turn, to physiological gait for the Posterior Stabilized than Medial Pivot group parameters.

Sensor-guided technology helps to reproduce medial pivot kinematics in total knee arthroplasty.

Two cohorts of 50 patients each were preoperatively matched to receive the same TKA, having a J-curve femoral design with an adapted "medially congruent" polyethylene insert; the second cohort (group B) underwent the intraoperative sensor-check. Intraoperative sensor data were recorded as tibiofemoral load at 10°, 45°, and 90°. We considered stable knees those with a pressure <50 lbs on the medial compartment, <35 lbs on the lateral, and a mediolateral inter-compartmental difference <15 lbs. Clinical outcomes were evaluated according to the Oxford Knee Score (OKS) and Knee Society Score (KSS). All patients (group A: no sensor; group B: sensor) were available at 2-year minimum follow-up (FU; min. 24 months, max. 34 months); no preoperative statistical differences existed between groups in the average range of motion (ROM), OKS, KSS, and body mass index. There were no statistical differences at final FU between groups in the average OKS (group A: 41.1; group B: 41.5), in the average KSS (group A: 165.7; group B: 166.3), or in final ROM (group A: 123°; group B: 124°). One patient in each group required a manipulation under anesthesia. In the sensor group, an accessory soft tissue release/bone recut was necessary after sensor testing with trial components in 24% to obtain the desired loads; in the same group, the level of constraint in the final components was increased to posterior-stabilized in 12% because of an inter-compartmental difference >40 lbs. Surgical time was 8 min longer in the sensor group. The use of this sensing technology did not improve the clinical outcome but supported multiple intraoperative decisions aimed to better reproduce the medial pivot kinematic of the normal knee.

In vivo femorotibial kinematics of medial-stabilized total knee arthroplasty correlates to post-operative clinical outcomes.

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

Trends in Total Knee Arthroplasty in a Developing Region: A Survey of Latin American Orthopaedic Surgeons.

A number of different total knee arthroplasty techniques are available. There is also a degree of surgeon preference for these, and the variation across orthopaedic surgeons in Latin America is currently unknown. A survey on members of Sociedad Latinoamericana de Artroscopia, Rodilla y Deporte was performed, with questions based on categories within worldwide national joint registries. In total, 315 Sociedad Latinoamericana de Artroscopia, Rodilla y Deporte members received the survey via e-mail, and the return answers were compared with the latest worldwide national joint registry annual reports. The survey was completed in full by 262 surgeons (83%). It was answered that 19% of surgeons perform less than 10 total knee arthroplasties per year, 54% perform less than 30, and only 9% perform more than 100. Seventy-three percent of surgeons use a posterior stabilized total knee replacement, 18% use a cruciate retaining total knee replacement, and 9% use a medial pivot design. Forty-nine percent of surgeons resurface the patella, 27% never resurface it, and 24% choose to resurface it based on an individual case scenario. Ninety-eight percent of surgeons use cemented fixation in the femur and tibia, with the remaining 2% choosing hybrid fixation and 1% using fully noncemented fixation. This survey among Latin American surgeons has demonstrated important differences in surgical technique and implants choice compared with worldwide national registries.

CORR Insights®: Decreased Survival of Medial Pivot Designs Compared with Cruciate-retaining Designs in TKA Without Patellar Resurfacing.

CORR Insights®: Decreased Survival of Medial Pivot Designs Compared with Cruciate-retaining Designs in TKA Without Patellar Resurfacing.

No clinical differences at the 2-year follow-up between single radius and J-curve medial pivot total knee arthroplasty in the treatment of neutral or varus knees.

Modern total knee arthroplasty (TKA) systems are designed to reproduce the normal knee kinematics and improve patient outcome. The authors compared two different third-generation medial pivot TKA implants, having a single-radius or a J-curve design in their sagittal plane, hypothesizing no clinical differences. Two cohorts of 50 patients who underwent primary TKA were first preoperatively matched by sex, deformity, body mass index (BMI), Oxford Knee Score (OKS), Knee society score (KSS) and range of motion (ROM) and then statistically analyzed at a minimum follow-up (FU) of 2years. An identical surgical technique, which aimed to reproduce a slightly tighter medial than lateral compartment, was used in all knees. At a minimum follow-up of 2years (range 24-34months) there were no statistically significant differences in OKS and KSS between the two implant groups. The final ROM differed statistically between the two groups: the average maximum active flexion was 123° in the J-curve femoral design group with an adapted "medially-congruent" polyethylene insert, and 116° in the single radius femoral design with a medial "ball-in-socket" articulation. No clinical and radiological differences were found when the two cohorts of patients were compared. This study showed that the implant design played a minor role in the final outcome as opposed to a precise surgical technique. Retrospective case-control study, Level III.

The inclination of the femoral medial posterior condyle was almost vertical and that of the lateral was tilted medially.

The purpose of this study was to three-dimensionally analyse the size and shape of the femoral posterior condyles of the normal knee. A total of 62 healthy Japanese volunteers (37 males and 25 females) providing a sample of 124 normal knee joints, who had no knee-related symptoms and no history of major trauma, underwent computed tomography scans of the bilateral femur and tibia. Three-dimensional digital models of the femur were constructed from computed tomography data using visualisation and modelling software. The following parameters were evaluated: (1) the radii of the posterior condyles approximated to spheres and (2) the inclination angle of the posterior condyles in the coronal plane of the femoral coordinate system. The radii of the medial and lateral condyles approximated to spheres were 17.0 ± 1.6 and 17.1 ± 1.8mm, respectively and were not different. The inclination angles of the medial and lateral condyles in the coronal plane were - 0.6° ± 4.6° and 9.7° ± 5.7°, respectively. The medial condyle was almost vertical, whereas the lateral one was medially tilted. This study found an asymmetrical inclination between medial and lateral condyles. This may be related to the asymmetrical motion of the knee, which is known as medial pivot motion. This finding provides valuable morphological information and may be useful for implant designs for total knee arthroplasty. IV.

P.102 Spatio-temporal characterization of its expression pattern reveals new roles of the 5-HT6 receptor in neurodevelopment

Constraint choice in revision total knee arthroplasty depends on the stability of the collateral ligaments and on the severity of bone loss, but the least degree of constraint necessary is recommended. The purpose of this retrospective matched-paired study was to compare clinical results, radiographic outcome and the survival of a stemmed medial pivot revision implant in aseptic revision TKA vs. medial pivot implant in primary TKA.Records were reviewed for 69 cases of aseptic revision TKA using Advance® Medial Pivot Stemmed Revision Knee system between 2002 and 2016. These patients were then matched in a 1:2 ratio control group of patients who received a primary TKA with Advance® Medial Pivot system. American Knee Society Score and Visual Analogue Scale pain score were recorded. Alignment, loosening, and incidence of radiolucent lines were evaluated on X-rays. Implant survival was assessed by Kaplan–Meier survival analysis.The primary TKA group had significant superior AKSS clinical and functional score at baseline (52.3 and 68.2 points, respectively) and at last follow up (84.6 and 68.6 points) compared with the revision TKA group (47.9 and 40.9 points; 78.4 and 59.9 points; P < 0.05). No significant difference was observed in the mean change from baseline to last follow up of AKSS score between the two groups (P > 0.05). Radiographical outcome and implant survival were similar in the two groups (P > 0.05).The authors support the use of this revision system in knees with collateral ligaments competence and mild-to-moderate bone defect.

Gait Analysis in Patients Underwent Total Knee Arthroplasty With a Medial Pivot Design.

Gait Analysis in Patients Underwent Total Knee Arthroplasty With a Medial Pivot Design.

Prediction of wear performance in femoral and tibial conformity in patient-specific cruciate-retaining total knee arthroplasty

BackgroundArticular surface curvature design is important in tibiofemoral kinematics and the contact mechanics of total knee arthroplasty (TKA). Thus far, the effects of articular surface curvature have not been adequately discussed with respect to conforming, nonconforming, and medial pivot designs in patient-specific TKA. Therefore, this study evaluates the underlying relationship between the articular surface curvature geometry and the wear performance in patient-specific TKA.MethodsWe compare the wear performances between conventional and patient-specific TKA under gait loading conditions using a computational simulation. Patient-specific TKAs investigated in the study are categorized into patient-specific TKA with conforming articular surfaces, medial pivot patient-specific TKA, and bio-mimetic patient-specific TKA with a patient’s own tibial and femoral anatomy. The geometries of the femoral components in patient-specific TKAs are identical.ResultsThe anterior-posterior and internal-external kinematics change with respect to different TKA designs. Moreover, the contact pressure and area did not directly affect the wear performance. In particular, conforming patient-specific TKAs exhibit the highest volumetric wear and wear rate. The volumetric wear in a conforming patient-specific TKA is 29% greater than that in a medial pivot patient-specific TKA.ConclusionThe findings in this study highlight that conformity changes in the femoral and tibial inserts influence the wear performance in patient-specific TKA. Kinematics and contact parameters should be considered to improve wear performance in patient-specific TKA. The conformity modification in the tibiofemoral joint changes the kinematics and contact parameters, and this affects wear performance.

Multi-radius posterior-stabilized mobile-bearing total knee arthroplasty partially produces in-vivo medial pivot during activity of daily living and high demanding motor task.

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

The short term clinical results of Medial pivot total knee arthroplasty with medially stabilized procedure

The short term clinical results of Medial pivot total knee arthroplasty with medially stabilized procedure