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Introduction The aim of the present study was to compare mid-term clinical and functional results of two fixed-bearing EUROP total knee arthroplasties (TKA) with the same design, one in which the posterior cruciate ligament was retained (CR) and the other with posterior-stabilization (PS). Hypothesis Mid-term results are similar. Materials and methods In this prospective, single centre, comparative study, 104 patients (mean age 76) received 114 cemented fixed-bearing posterior cruciate-retaining or posterior-stabilized EUROP TKA. Only patients in whom the medial pivot and ligaments were intact received a CR prosthesis. The final decision to retain or not the posterior cruciate ligament was made if the flexion gap was well balanced above 90°. Clinical evaluation was performed using the International Knee Society (IKS) score at a mean follow-up of 54 months. Results The preoperative IKS function score improved from 30 points in both groups, to 75 points in the CR group and to 65 points in the PS group postoperatively. The preoperative IKS knee score improved from 29 and 25 points in the CR and PS groups, respectively, to 87 points in both groups postoperatively. There was no significant difference in the pre- or postoperative scores between the two groups. Four prostheses underwent surgical revision, three CR and one PS. With revision for any reason as the end point, seven-year overall implant survival was 94.8% in the CR group and 97.5% in the PS group. There was no significant difference between the CR and PS groups. Discussion When the indications were followed, our study shows similar mid-term results for both types of TKA. Level of evidence Level IV, prospective study.

The aim of this study is to evaluate the relationship between patellofemoral contact stress and intraoperative knee kinematic patterns after mobile bearing total knee arthroplasty (TKA). Medial osteoarthritic knees of forty-six posterior-stabilized total knee prostheses were evaluated using a computed tomography-guided navigation system. Subjects were divided into two groups based on intraoperative knee kinematic patterns: the medial pivot group (n=19) and the non-medial pivot group (n=27). Mean intraoperative patello-femoral contact stress was significantly lower in the medial pivot group than in the non-medial pivot group (1.7MPa vs. 3.2MPa, P

ObjectivesThis systematic review and meta-analysis was conducted to determine the mid- to long-term clinical outcomes for a medial-pivot total knee replacement (TKR) system. The objectives were to synthesise available survivorship, Knee Society Scores (KSS), and reasons for revision for this system.MethodsA systematic search was conducted of two online databases to identify sources of survivorship, KSS, and reasons for revision. Survivorship results were compared with values in the National Joint Registry of England, Wales, and Northern Ireland (NJR).ResultsA total of eight studies that included data for 1146 TKRs performed in six countries satisfied the inclusion/exclusion criteria. Pooled component survivorship estimates were 99.2% (95% CI, 97.7 to 99.7) and 97.6% (95% CI, 95.8 to 98.6) at five and eight years, respectively. Survivorship was similar or better when compared with rates reported for all cemented TKRs combined in the NJR and was significantly better than some insert types at mid-term intervals. The weighted mean post-operative KSS was 87.9 (73.2 to 94.2), in the excellent range. Similar cumulative revision rates and KSS were reported at centres in the United States, Europe, and Asia.ConclusionsThe subject system was associated with survivorship and KSS similar or better than that reported for other TKR systems. Cite this article: Bone Joint Res 2014;3:297–304

Purpose To evaluate minimum 5-year follow-up clinical and radiological results of total knee arthroplasty (TKA) using a posterior cruciate ligament sacrificing (PS), non-substituting Advance Medial Pivot Knee. Materials and Methods One hundred and twenty knees in 80 patients who could be followed up for more than 5 years after TKA using the PS Advance Medial Pivot Knee were evaluated retrospectively. The evaluations included the preoperative and postoperative range of motion (ROM), tibiofemoral angle, Knee Society (KS) knee and function scores, and Western Ontario and McMaster Universities Arthritis Index (WOMAC) score. The Kaplan-Meier method was used for survival analysis. Results The ROM increased from a preoperative mean flexion contracture of 7.6° and further flexion of 115.1° to a postoperative mean flexion contracture of 1.5° and further flexion of 120.5°. The tibiofemoral angle was changed from 4.6° varus preoperatively to 5.8° valgus postoperatively. The KS knee and function scores as well as WOMAC score significantly improved after surgery (p

The aim of this study was to evaluate the relationship between clinical results including patient-reported outcomes and intraoperative knee kinematic patterns after total knee arthroplasty (TKA). A cross-sectional survey of forty consecutive medial osteoarthritis patients who had a primary TKA using a CT-based navigation system was conducted. Subjects were divided into two groups based on intraoperative kinematic patterns: a medial pivot group (n = 20) and a non-medial pivot group (n = 20). Subjective outcomes with the new Knee Society Score and clinical outcomes were evaluated. The functional activities, patient satisfaction and the knee flexion angle of the medial pivot group were significantly better than those of the non-medial pivot group. An intraoperative medial pivot pattern positively influences deep knee flexion and patient-reported outcomes.

Background In order to emulate normal knee kinematics more closely, and thereby potentially improve wear characteristics and implant longevity, the medial pivot-type knee replacement geometry was designed. In the current study the outcome of 50 consecutive knee replacements using a medial pivot-type knee replacement was compared with the results in the Australian Orthopaedic Association National Joint Replacement Registry. Methods Pre- and post-operatively at follow-up evaluation consisted of the Knee Society score system and the Western Ontario and McMaster Universities Arthritis Index Score. Patient satisfaction was documented using 5-point Likert-type scales. Standard radiographs were used to assess signs of radiographic failure. Revisions were subcategorized into major total, major partial and minor. Patient records were cross-referenced against the Australian Orthopaedic Associations National Joint Replacement Registry's and the outcome compared with the registry's subset of data on the medial pivot knee used. Results According to the patients' Knee Society score system and Western Ontario and McMaster Universities Arthritis Index scores, there was good pain relief and functional improvement; none of the implants showed radiographic signs of failure. There was one minor revision. There was no statistically significant difference in revision rate compared with the registry results. Discussion The medial pivot knee-type implant in this series provided pain relief, functional improvement and a revision rate, similar to what is reported in the literature after a longer follow-up period, which is reassuring for those who use this type of implant on a day-to-day basis.

Purpose: Primary total knee arthroplasty (TKA) can be an alternative method for treating distal femoral fractures in elderly patients with knee osteoarthritis. The purpose of this study was to evaluate the clinical and radiographic results in patients with knee osteoarthritis who underwent TKA with the Medial Pivot prosthesis for distal femoral fractures. Materials and Methods: Eight displaced distal femoral fractures in 8 patients were treated with TKA using the Medial Pivot prosthesis and internal fixation. The radiographic and clinical evaluations were performed using simple radiographs and Hospital for Special Surgery (HSS) knee scores during a mean follow-up period of 49 months. Results: All fractures united and the mean time to radiographic union was 15 weeks. The mean range of motion of the knee joint was 114.3 o and the mean HSS knee score was 85.1 at the final follow-up. Conclusions: Based on the radiographic and clinical results, TKA with internal fixation can be considered as an option for the treatment of simple distal femoral fractures in elderly patients who have advanced osteoarthritis of the knee with appropriate bone stock.

To report clinical results and demonstrate posterior femoral translation (PFT) in medial pivot total knee arthroplasty (TKA) of posterior cruciate ligament (PCL) retaining type.A prospective study was performed upon thirty consecutive subjects who were operated on with medial pivot TKA of PCL retaining type between March 2009 and March 2010 and had been followed up for at least 2 years. Clinically, the knee society knee score and function score were used. In full extension and active flexion lateral radiograph, anteroposterior (AP) condylar position and magnitude of PFT was determined.At last follow-up, the mean knee society knee score and function score improved significantly compared to preoperative scores. The AP condylar positions were consistently posterior to midline throughout the entire range of flexion. The PFTs averaged 0.31 (±0.12) of half length of tibial base plate and were greater in higher flexion cases (r = 0.56, p = 0.0012). There were no cases having either component migration or radiolucent line wider than 2 mm except for one case showing instability related to trauma.In medial pivot TKA of PCL retaining type, clinical outcomes were satisfactory and posterior femoral translations were consistently observed during progressive flexions of knees at two- to three-year follow-up.

The ideal total knee arthroplasty (TKA) should provide maximum range of motion and functional stability for all desired daily activities and, if possible, to replicate normal knee kinematics and function. The ADVANCE® Medial Pivot (AMP) Knee System was designed with a highly congruent medial compartment and a less conforming lateral compartment to more closely mimic the kinematics of the normal knee and to offer more stability through out of range of motion (ROM). The purpose of this study was to evaluate the long-term clinical and radiographic outcomes of this TKA system.Three hundred and twenty-five (325) patients (347 knees) with knee osteoarthritis underwent a TKA using the AMP prosthesis in our Department. For evaluation, objective and subjective clinical rating systems along with radiograph series were used. The average follow-up was 15.2years.All patients showed a statistically significant improvement (p0.0005) in the Knee Society clinical rating system, Western Ontario and McMaster Universities Osteoarthritis Index questionnaire, SF-12® questionnaire, and Oxford knee score. The majority of patients (94%) were able to perform age-appropriate activities with a mean knee flexion of 120° (range, 105°-135°) at final follow-up. Survival analysis showed a cumulative success rate of 98.8% at 17years.The obtained results demonstrate excellent long-term clinical outcome for this knee design.

Background The Orthopaedic Data Evaluation Panel (ODEP) monitors the performance of primary total knee arthroplasty (TKA) implants against guidance provided by the National Institute for Health and Care Excellence (NICE) and issues ratings based upon survivorship data meeting or exceeding 95 % at 10-year follow-up. The objectives of the current study were to determine if the survivorship for the ADVANCE Medial-Pivot System in an arthroplasty registry exceeds this threshold and if its survivorship is significantly different than that of all other cemented bi-, tricompartmental, minimally stabilized, and fixed bearing TKAs in the same registry. Methods The database of an arthroplasty registry was searched for all TKAs performed with the subject system and all other cemented TKAs. The Kaplan-Meier survivorship for the subject system was compared to the NICE criteria and also that of all other cemented TKAs. Complication modes were also examined for the two groups. Results The 10-year survivorship for the included 506 TKAs using the subject system (96.3 %) exceeded the NICE guidelines of 95 % at 10 years. Survivorship also exceeded that of all other cemented TKAs (95.7 %) in the same registry, but the difference was not significantly different. Conclusions The subject system was associated with survivorship that exceeds the NICE guidelines at 10 years and is similar to that of other cemented TKA systems. The use of this unique tibial insert design does not negatively impact component survivorship.

After total knee arthroplasty (TKA), patients may experience noise from their replaced knee. A prospective study was conducted with 465 (930 knees) patients to evaluate noise after bilateral TKA. A different randomly selected prosthesis was used on each side. The prostheses used were medial pivot (MP), anterior and posterior cruciate ligament retaining (ACL-PCL), posterior cruciate ligament retaining (PCL), posterior cruciate-substituting (PS), or mobile bearing (MB). The evaluation included the patients' responses to questions about noise after both their TKAs. Noise-related symptoms were reported by 12% of the patients with MP prostheses, 4% of patients with ACL-PCL, 31% of patients with PCL, 33% of patients with PS, and 42% of patients with MB. Occasionally, patients were concerned or dissatisfied with this phenomenon. Noise was less common with TKAs that used MP and ACL-PCL knee prostheses than with TKAs that used other prostheses.

Nine ADVANCE (Wright Medical Technology, Arlington, TN)) Medial-Pivot (MP) and 9 ADVANCE Double-High total knee arthroplasties were analyzed under radiographic surveillance at standing, mid kneeling, and full kneeling. In vivo tibiofemoral contact positions were obtained using the 3- to 2-dimensional image registration technique. The contact in Double-High knee was always more posterior than that in the MP knee presumably because of the presence of the posterior cruciate ligament. The contact positions in both the designs moved anterior from standing to mid kneeling, moved posterior from mid kneeling to full kneeling, and remained within the intended articulation range of the implants. This study indicates that kneeling is safe in MP total knee arthroplasty even in the absence of a cam-post or posterior cruciate ligament.

Four-hundred forty patients underwent staged bilateral total knee arthroplasty using a different prosthesis on each side. Prostheses used were anterior-posterior cruciate-retaining (ACL-PCL), posterior cruciate-retaining (PCL), Medial Pivot (MP), posterior cruciate-substituting (PS), and mobile bearing (MB). At the 2-year evaluation, we asked "Which is your better knee overall?" Responses were as follows: 89.1% preferred the ACL-PCL to the PS and 76.2% preferred the MP to the PS. The ACL-PCL and the MP were preferred equally. The MP was preferred over the PCL by 76.0%, and 61.4% preferred the MP over the MB. The PS and PCL were preferred equally. Range of motion, pain relief, alignment, and stability did not vary significantly by prosthesis used. Patients with bilateral total knee arthroplasties preferred retention of both cruciates with use of the ACL-PCL prosthesis or substituting with an MP prosthesis.

Paradoxical anterior movement of the femoral condyles after total knee arthroplasty (TKA) often attenuates the extension mechanism and causes a suboptimal outcome. The medial-pivot implant design aimed to confine anterior movement and emulate physiologic knee kinematics. In our study, a consecutive series of 58 medial-pivot TKA were enrolled with a minimum 5-year follow-up. The Knee Society score improved from 30.5 to 91.1 in objective and from 36.7 to 82.3 in functional scale. The average range of motion was 115.4°. The medial-pivot TKA provided significant improvement in the postoperative range of motion, objective Knee Society score, pain scale, and functional score (P < .05) statistically. A larger sample and longer follow-up are recommended to draw definitive conclusions of this new implant design.

In modern total knee arthroplasty (TKA), it is important to reproduce both medial pivot motion and posterior femoral rollback to obtain greater postoperative knee flexion. Several studies have reported the factors affecting knee motion and range of motion after TKA. The purpose of this study was to evaluate the effect of the tibial insert geometry on the tibiofemoral contact kinematics, especially focusing on the medial pivot motion and posterior femoral rollback.Seven cadaveric knees were replaced with the Advance Medial Pivot TKA, and two different geometries of polyethylene tibial insert, the standard medial pivot design (MP-design) and double high design (DH-design), were biomechanically compared. Four experimental configurations were evaluated in each specimen in this order: (1) the MP-design with posterior cruciate ligament (PCL) retaining, (2) the DH-design with PCL retaining, (3) the MP-design with PCL sacrificing, and (4) the DH-design with PCL sacrificing.Under the PCL-retaining condition, both designs showed no medial pivot but bicondylar femoral rollback more than 60 degrees of knee flexion. In the MP-design, tibiofemoral contact point (estimated contact point, ECP) of the medial compartment was located on the posterior lip of the ball-insocket structure while demonstrating greater than 120 degrees of knee flexion. The posterior translation was also the same in both designs. On the other hand, ECP of the MP-design and the DH-design showed only medial pivot pattern under the PCL-sacrificing condition. In the DH-design, ECP of the lateral compartment showed paradoxical anterior translation from 0 degrees to 60 degrees of knee flexion. Total posterior translation was significantly greater in the lateral compartment than that in the medial compartment.The results of this study suggest that in this type of TKA system the ball-in-socket geometry in the MP-design has an advantage for reproducing medial pivot motion in the PCL-sacrificing condition, and the flexion path structure in the DH-design is considered to be both effective and safe for femoral rollback in the PCL-retaining condition. However, neither design is sufficient to reproduce medial pivot motion and posterior femoral rollback. Therefore, a different design of tibial insert is needed for more physiological kinematics after TKA.

Newer designs of total knee arthroplasty (TKA), through the use of added degrees of constraint, attempt to provide a "guided motion" to restore more normal and predictable kinematics. Two such design philosophies are the posterior stabilised (PS) using a cam-post and the medial pivot (MP) concepts. Knee kinematics of 12 patients with a PS TKA, 13 subjects with a MP TKA and 10 normal subjects were compared. For kinematic assessment, patients underwent fluoroscopic assessment of the knee during a step-up exercise and deep knee bend. Fluoroscopic images were corrected for distortion and assessed using 3D model fitting to determine relative 3D motion, and a 2D method to measure the patellar tendon angle (PTA) as function of knee flexion. For the PS design the cam-post mechanism engaged between 70 degrees and 100 degrees flexion. Between extension and 50 degrees there was forward motion of the contact points. Beyond 60 degrees both condyles rolled moved posteriorly. The majority of the external rotation of the femur occurred between 50 degrees and 80 degrees . The PTA was lower than normal in extension and higher than normal in flexion. The MP exhibited no anterior movement throughout the rage of motion. The medial condyle moved minimally. The lateral contact point moved posteriorly from extension to flexion. The femur rotated externally throughout the range of flexion analysed. The PTA was similar to normal from extension to mid flexion and then higher than normal beyond to high flexion. The PS design fails to fully restrain paradoxical anterior movement and although the cam engages, it does not contribute significantly to overall rollback. The MP knee does not show significant anterior movement, the medial pivot concept appears to achieve near normal kinematics from extension to 50 degrees of knee flexion. However, the results show that at high flexion this design does not achieve normal knee kinematics.

Background Despite the theoretical advantage of a knee design that can more reliably replicate the medial pivot (MP) of the natural knee, only a few clinical studies have compared the clinical results between the MP prosthesis and another design of prosthesis. We compared the midterm results of total knee arthroplasty (TKA) using an MP prosthesis vs a posterior-stabilized prosthesis via a matched-pair analysis; we included results related to patellofemoral joint symptoms. Methods The midterm clinical and radiographic results of 125 consecutive patients (150 knees) who underwent a TKA with the ADVANCE MP prosthesis were compared with those of a control group who had undergone a primary TKA with a posterior-stabilized prosthesis. Results Values of the Knee Society’s Knee Scoring System, Western Ontario and McMaster Universities Osteoarthritis Index, and Kujala and Feller scoring systems, as well as the range of motion after TKA, did not significantly differ between the 2 groups. No differences in femorotibial angle and component position, including the patella component, were observed between the 2 groups. No significant differences in the change of patella tilt angle and the postoperative patellar translation were observed between the 2 groups. Conclusion Patients with the MP prosthesis experienced satisfactory pain relief and a functional recovery, providing results similar to those of the posterior-stabilized prosthesis, including the resolution of patellofemoral joint symptoms.

Alterations in normal knee kinematics following total knee arthroplasty (TKA) arise in part from the non-anatomic articular geometry of contemporary implants. In this study, the kinematics of a novel posterior cruciate-retaining (CR) implant with anatomic (biomimetic) articular surface, were compared to that of contemporary CR implants during various simulated activities. Across different simulated activities the biomimetic-CR mimicked normal kinematic patterns more closely than contemporary CR implants. In particular, during deep knee bend and chair-sit, the biomimetic-CR showed medial pivot motion, while other CR implants showed abnormal motion including lateral pivot or no pivot, and paradoxical anterior sliding. Further in vivo and clinical studies are needed to determine whether such biomimetic implants can truly help to achieve a more normal feeling knee and improved patient satisfaction.

There are a number of different total knee arthroplasty (TKA) implant options on the market today with different kinematic properties. Posterior-stabilized total knee systems sacrifice the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL). The PS system relies on a cam-post mechanism to engage during flexion, forcing posterior femoral translation. This allows for improved deep flexion by both providing stability and decreasing posterior femoral impingement on the tibial component. Cruciate-retaining total knee arthroplasty follows the tenets of retaining an intact, appropriately tensioned PCL. Cruciate-retaining (CR) systems rely on the knee’s ligamentous balance and PCL to provide those same goals as described above. The medial pivot knee is cruciate sacrificing and available with or without posterior-stabilization (PS). The medial rotation (MR) design focuses on achieving both stability and the native knee’s “screw home mechanism” of internal tibial rotation in comparison to the femoral condyles through a highly concentric tibial polyethylene insert. The spherical medial femoral condyle and complimentary medial tibial tray with a slotted lateral compartment encourage both femoral rollback and the medial pivot axis of the normal knee. The differences and/or benefits of one type of system over the other have not been clearly and definitively born out in the literature. As long-term success of total knee arthroplasty has continued to improve since its inception and first implantation in the 1970s, the progression over the past decades has been with the end goal of achieving native knee motion through the weight-bearing flexion arc. PS implant designs may more reliably create posterior femoral rollback. However, none of the described TKA systems completely restore normal knee kinematics. Outcomes for the described implant categories have been good with survivorship reported as high as 90–95 % at 15–20 years. Despite this, further research is ongoing to better replicate the normal knee and restore the stability and flexion that both patients and orthopedic surgeons seek in a total knee arthroplasty.

In a series of 90 Medial Pivot arthroplasties rotational alignment of the femur was achieved by provisionally reconstructing the lateral side of the joint and tensioning the medial side with feeler gauges. Axial CT scans were employed to measure the rotational alignment relative to surgical epicondylar axis. In valgus knees the cutting block was externally rotated to adjust for posterolateral bone loss. The mean rotational alignment of the femur was 0.6° of external rotation (S.D. 1.3, range 3° of ER to 4° of IR). The mean laxity of the medial ligament was 1 mm in flexion (SD 1, range 0–5 mm) and 0.5 mm in flexion (S.D. 0.5, range 0–2 mm) In those knees in which the medial ligament had been released the CT alignment was perfect, but when internally rotated against the hip 3–4 mm of gapping was noted. In valgus knees the mean rotation of the femoral component was 0.8° of internal rotation (S.D. 1.5, range 1° of IR to 4° of ER). In spite of externally rotating the cutting block there was still a tendency to internally rotate the femur in some knees. This simple technique achieves the two goals of ligament stability and correct rotational alignment in a high proportion of cases. It may be applicable to any instrument system which employs posterior referencing.

Contemporary posterior cruciate-retaining total knee designs have provided pain relief and improved knee function but have failed to reproduce the kinematics and stability of the normal nonarthritic knee. The Medial Pivot total knee design features a near constant radius of curvature of the femoral component. The tibial surface is highly congruent and asymmetric, permitting a medial pivot motion during knee flexion. The purpose of the current study was to analyze and compare the gait kinematics of the Sigma posterior cruciate-retaining total knee implant, the Advance Traditional posterior cruciate-retaining total knee implant, and the Advance Medial Pivot knee implant using fluoroscopic analysis. In vivo kinematics were determined for 15 clinically successful total knee arthroplasties. Five knee implants were evaluated from each group. The authors analyzed the kinematics of knee motion during the stance phase of gait for each patient. On average, subjects with the Medial Pivot knee implant had a medial pivot motion. Both posterior cruciateretaining designs had a paradoxical roll forward of the tibia on femur during knee flexion and had greater excursion of both condyles during knee flexion than the medial pivot design. Nine of 10 of the posterior cruciate-retaining designs had condylar lift-off averaging 1.7 mm whereas only one Medial Pivot knee implant had condylar lift-off measuring 1.1 mm.

We conducted a retrospective review of 2 consecutive series of posterior-stabilized total knee arthroplasties (TKAs) to evaluate patellofemoral complications, in particular, significant patellofemoral crepitance or patellar clunk syndrome. Twenty posterior-stabilized Axiom PSK (Wright Medical Technology, Arlington, TN) TKAs (group 1) were compared with 20 posterior cruciate-sacrificed Advance medial pivot (Wright Medical Technology, Arlington, TN) TKAs (group 2). The average age in group 1 was 69 years and in group 2 was 70 years. Preoperative valgus alignment in group 1 was 7.5 degrees and in group 2 was 1.3 degrees. Postoperative valgus alignment for the 2 groups was 4.8 degrees and 5.3 degrees valgus. Postoperative patellar tilt for the 2 groups was 0.9 degrees lateral tilt and 8 degrees lateral tilt. Patellofemoral signs of crepitance > or =2+ and significant box impingement complaints of either snapping or clunking decreased significantly postoperatively from 5 of 20 (25%) in group 1 to 0 of 20 in group 2 (P=.0079).

Excellent clinical and kinematical performance is commonly reported after medial pivot knee arthroplasty. However, there is conflicting evidence as to whether the posterior cruciate ligament should be retained. This study simulated how the posterior cruciate ligament, post-cam mechanism and medial tibial insert morphology may affect postoperative kinematics. After the computational intact knee model was validated according to the motion of a normal knee, four TKA models were built based on a medial pivot prosthesis; PS type, modified PS type, CR type with PCL retained and CR type with PCL sacrificed. Anteroposterior translation and axial rotation of femoral condyles on the tibia during 0°–135° knee flexion were analyzed. There was no significant difference in kinematics between the intact knee model and reported data for a normal knee. In all TKA models, normal motion was almost fully restored, except for the CR type with PCL sacrificed. Sacrificing the PCL produced paradoxical anterior femoral translation and tibial external rotation during full flexion. Either the posterior cruciate ligament or post-cam mechanism is necessary for medial pivot prostheses to regain normal kinematics after total knee arthroplasty. The morphology of medial tibial insert was also shown to produce a small but noticeable effect on knee kinematics. V.

A comparison was made between 261 knees replaced with the Medial Pivot arthroplasty and 288 replaced with the 913 posterior stabilised arthroplasty (PS knee). There was no significant difference in the flexion obtained at 12 months after surgery (111 degrees and 109 degrees , respectively). When the knees were grouped into preoperative flexion ranges, there was no significant difference between the two implants. Those knees with preoperative flexion up to 90 degrees gained most (mean 22.6 degrees and 19 degrees for the PS knee and Medial Pivot, respectively). Knees with a preoperative flexion of 125 degrees or greater lost flexion. Regression analysis of individual knees revealed a small (average 2.9 degrees ), but significant greater loss of flexion at 12 months after surgery in the Medial Pivot group, with increasing preoperative flexion (beta coefficient = 2.923, P = 0.007). Some knees in both groups which had less than average preoperative flexion lost rather than gained flexion. We attributed this to patient factors such as pain, swelling and poor compliance with rehabilitation. Although the Medial Pivot knee may have advantages in terms of contact area and kinematics we found no advantage in terms of postoperative flexion over our posterior stabilised knee.

Background: Patient dissatisfaction following total knee replacement (TKR) has been reported as high as 24%. Most previous studies have focused on satisfaction for TKR overall, with few reporting satisfaction for specific implant designs. The purpose of this study was to assess patient satisfaction for TKRs performed using a second generation medial-pivot system (EVOLUTION ® , MicroPort Orthopedics Inc., Arlington, TN, USA). Methods: Of a single surgeon’s first 250 consecutive TKRs performed using the subject system, 224 completed a patient satisfaction assessment, the Knee Injury and Osteoarthritis Outcome Score (KOOS), range of motion, and radiographs at 2 months follow-up. Results: The overall very satisfied/satisfied rate was 94.6% at 2 months. Following the first 50 TKRs, the satisfied rate improved to 99.4% suggesting a bias towards the initial cases potentially due to learning the system and instrumentation. Overall KOOS, range of motion, and radiographic outcomes were satisfactory at final follow-up. Conclusions: In conclusion, more subjects implanted with a second generation medial-pivot system were satisfied compared to previous reports for TKR.

ADVANCE Medial-Pivot (MP) (Wright Medical Technology, Arlington, TN, USA) total knee arthroplasty (TKA) was developed to replicate normal tibiofemoral knee joint kinematics, allowing medial-pivot knee motion. The design concept of the prosthesis is unique; therefore, the influence on the patellofemoral knee joint remains unclear at present. The purpose of this study was to determine the in vivo patellofemoral kinematics with ADVANCE MP TKA and compare them with the pre-operative conditions.ADVANCE MP TKA was performed in ten subjects with osteoarthritis (OA). At before and one month after surgery, lateral radiographs with weight-bearing at maximum extension, 30, 60 and 90° were taken, and patella flexion angle (PF), tibiopatellar angle (TP) and estimated patellofemoral contact point (PC) were evaluated, according to a previously reported method.In PF and TP, there was no statistically significant change between pre-operative and postoperative values. Pre-operative PC reached its peak at 90°; however, its peak was at 60° at one month after surgery. Postoperative PC at maximum extension was significantly higher compared to before surgery.The results in this study indicated that ADVANCE MP TKA changed patellofemoral joint kinematics compared to before surgery. Early postoperative evaluation is the limitation of this study; however, we consider that the results in this study might be one of the keys to resolving the kinematic features of this prosthesis, helping clinicians to comprehend this prosthesis.