Aims. Varus-valgus constrained (VVC) devices are typically used in revision settings, often with stems to mitigate the risk of aseptic loosening. However, in at least one system, the VVC insert is compatible with the primary posterior-stabilized (PS) femoral component, which may be an option in complex primary situations. We sought to determine the implant survivorship, radiological and clinical outcomes, and complications when this VVC insert was coupled with a PS femur without stems in complex primary total knee arthroplasties (TKAs). Methods. Through our institution’s total joint registry, we identified 113 primary TKAs (103 patients) performed between 2007 and 2017 in which a VVC insert was coupled with a standard cemented PS femur without stems. Mean age was 68 years (SD 10), mean BMI was 32 kg/m. 2. (SD 7), and 59 patients (50%) were male. Mean follow-up was four years (2 to 10). Results. The five-year survivorship free from aseptic loosening was 100%. The five-year survivorship free from any revision was 99%, with the only revision performed for infection. The five-year survivorship free from reoperation was 93%. The most common reoperation was treatment for infection (n = 4; 4%), followed by manipulation under anaesthesia (MUA; n = 2; 2%). Survivorship free from any complication at five years was 90%, with superficial wound infection as the most frequent (n = 4; 4%). At most recent follow-up, two TKAs had non-progressive radiolucent lines about both the tibial and femoral components. Knee Society Scores improved from 53 preoperatively to 88 at latest follow-up (p < 0.001). Conclusion. For complex primary TKA in occasional situations, coupling a VVC insert with a standard PS femur without stems proved reliable and durable at five years. Longer-term follow-up is required before recommending this technique more broadly. Cite this article: Bone Jt Open 2021;2(11):921–925

Aims. Mid-level constraint designs for total knee arthroplasty (TKA) are intended to reduce coronal plane laxity. Our aims were to compare kinematics and ligament forces of the Zimmer Biomet Persona posterior-stabilized (PS) and mid-level designs in the coronal, sagittal, and axial planes under loads simulating clinical exams of the knee in a cadaver model. Methods. We performed TKA on eight cadaveric knees and loaded them using a robotic manipulator. We tested both PS and mid-level designs under loads simulating clinical exams via applied varus and valgus moments, internal-external (IE) rotation moments, and anteroposterior forces at 0°, 30°, and 90° of flexion. We measured the resulting tibiofemoral angulations and translations. We also quantified the forces carried by the medial and lateral collateral ligaments (MCL/LCL) via serial sectioning of these structures and use of the principle of superposition. Results. Mid-level inserts reduced varus angulations compared to PS inserts by a median of 0.4°, 0.9°, and 1.5° at 0°, 30°, and 90° of flexion, respectively, and reduced valgus angulations by a median of 0.3°, 1.0°, and 1.2° (p ≤ 0.027 for all comparisons). Mid-level inserts reduced net IE rotations by a median of 5.6°, 14.7°, and 17.5° at 0°, 30°, and 90°, respectively (p = 0.012). Mid-level inserts reduced anterior tibial translation only at 90° of flexion by a median of 3.0 millimetres (p = 0.036). With an applied varus moment, the mid-level insert decreased LCL force compared to the PS insert at all three flexion angles that were tested (p ≤ 0.036). In contrast, with a valgus moment the mid-level insert did not reduce MCL force. With an applied internal rotation moment, the mid-level insert decreased LCL force at 30° and 90° by a median of 25.7 N and 31.7 N, respectively (p = 0.017 and p = 0.012). With an external rotation moment, the mid-level insert decreased MCL force at 30° and 90° by a median of 45.7 N and 20.0 N, respectively (p ≤ 0.017 for all comparisons). With an applied anterior load, MCL and LCL forces showed no differences between the two inserts at 30° and 90° of flexion. Conclusion. The mid-level insert used in this study decreased coronal and axial plane laxities compared to the PS insert, but its stabilizing benefit in the sagittal plane was limited. Both mid-level and PS inserts depended on the MCL to resist anterior loads during a simulated clinical exam of anterior laxity. Cite this article: Bone Jt Open 2023;4(6):432–441

Aims. This study compared patient-reported outcomes of three total knee arthroplasty (TKA) designs from one manufacturer: one cruciate-retaining (CR) design, and two cruciate-sacrificing designs, anterior-stabilized (AS) and posterior-stabilized (PS). Methods. Patients scheduled for primary TKA were included in a single-centre, prospective, three-armed, blinded randomized trial (n = 216; 72 per group). After intraoperative confirmation of posterior cruciate ligament (PCL) integrity, patients were randomly allocated to receive a CR, AS, or PS design from the same TKA system. Insertion of an AS or PS design required PCL resection. The primary outcome was the mean score of all five subscales of the Knee injury and Osteoarthritis Outcome Score (KOOS) at two-year follow-up. Secondary outcomes included all KOOS subscales, Oxford Knee Score, EuroQol five-dimension health questionnaire, EuroQol visual analogue scale, range of motion (ROM), and willingness to undergo the operation again. Patient satisfaction was also assessed. Results. Patients reported similar levels of pain, function, satisfaction, and general health regardless of the prosthetic design they received. Mean maximal flexion (129° (95% confidence interval (CI) 127° to 131°) was greater in the PS group than in the CR (120° (95% CI 121° to 124°)) and AS groups (122° (95% CI 120° to 124°)). Conclusion. Despite differences in design and constraint, CR, AS, and PS designs from a single TKA system resulted in no differences in patient-reported outcomes at two-year follow-up. PS patients had statistically better ROM, but the clinical significance of this finding is unclear. Cite this article: Bone Joint J 2023;105-B(12):1271–1278

Aims. We have previously reported the mid-term outcomes of revision total knee arthroplasty (TKA) for flexion instability. At a mean of four years, there were no re-revisions for instability. The aim of this study was to report the implant survivorship and clinical and radiological outcomes of the same cohort of of patients at a mean follow-up of ten years. Methods. The original publication included 60 revision TKAs in 60 patients which were undertaken between 2000 and 2010. The mean age of the patients at the time of revision TKA was 65 years, and 33 (55%) were female. Since that time, 21 patients died, leaving 39 patients (65%) available for analysis. The cumulative incidence of any re-revision with death as a competing risk was calculated. Knee Society Scores (KSSs) were also recorded, and updated radiographs were reviewed. Results. The cumulative incidence of any re-revision was 13% at a mean of ten years. At the most recent-follow-up, eight TKAs had been re-revised: three for recurrent flexion instability (two fully revised to varus-valgus constrained implants (VVCs), and one posterior-stabilized (PS) implant converted to VVC, one for global instability (PS to VVC), two for aseptic loosening of the femoral component, and two for periprosthetic joint infection). The ten-year cumulative incidence of any re-revision for instability was 7%. The median KSS improved significantly from 45 (interquartile range (IQR) 40 to 50) preoperatively to 70 (IQR 45 to 80) at a mean follow-up of ten years (p = 0.031). Radiologically, two patients, who had not undergone revision, had evidence of loosening (one tibial and one patellar). The remaining components were well fixed. Conclusion. We found fair functional outcomes and implant survivorship at a mean of ten years after revision TKA for flexion instability with a PS implant. Recurrent instability and aseptic loosening were the most common indications for re-revision. Components with increased constraint, such as a VVC or hinged, should be used in these patients in order to reduce the risk of recurrent instability. Cite this article: Bone Joint J 2022;104-B(10):1126–1131

Aims. This systematic review and meta-analysis aimed to compare the influence of patellar resurfacing following cruciate-retaining (CR) and posterior-stabilized (PS) total knee arthroplasty (TKA) on the incidence of anterior knee pain, knee-specific patient-reported outcome measures, complication rates, and reoperation rates. Methods. A systematic review of MEDLINE, PubMed, and Google Scholar was performed to identify randomized controlled trials (RCTs) according to search criteria. Search terms used included: arthroplasty, replacement, knee (Mesh), TKA, prosthesis, patella, patellar resurfacing, and patellar retaining. RCTs that compared patellar resurfacing versus unresurfaced in primary TKA were included for further analysis. Studies were evaluated using the Scottish Intercollegiate Guidelines Network assessment tool for quality and minimization of bias. Data were synthesized and meta-analysis performed. Results. There were 4,135 TKAs (2,068 resurfaced and 2,027 unresurfaced) identified in 35 separate cohorts from 33 peer-reviewed studies. Anterior knee pain rates were significantly higher in unresurfaced knees overall (odds ratio (OR) 1.84; 95% confidence interval (CI) 1.20 to 2.83; p = 0.006) but more specifically associated with CR implants (OR 1.95; 95% CI 1.0 to 3.52; p = 0.030). There was a significantly better Knee Society function score (mean difference (MD) -1.98; 95% CI -1.1 to -2.84; p < 0.001) and Oxford Knee Score (MD -2.24; 95% CI -0.07 to -4.41; p = 0.040) for PS implants when patellar resurfacing was performed, but these differences did not exceed the minimal clinically important difference for these scores. There were no significant differences in complication rates or infection rates according to implant design. There was an overall significantly higher reoperation rate for unresurfaced TKA (OR 1.46 (95% CI 1.04 to 2.06); p = 0.030) but there was no difference between PS or CR TKA. Conclusion. Patellar resurfacing, when performed with CR implants, resulted in lower rates of anterior knee pain and, when used with a PS implant, yielded better knee-specific functional outcomes. Patellar resurfacing was associated with a lower risk of reoperation overall, but implant type did not influence this. Cite this article: Bone Joint J 2023;105-B(6):622–634

Aims. To establish our early clinical results of a new total knee arthroplasty (TKA) tibial component introduced in 2013 and compare it to other designs in use at our hospital during the same period. Methods. This is a retrospective study of 166 (154 patients) consecutive cemented, fixed bearing, posterior-stabilized (PS) TKAs (ATTUNE) at one hospital performed by five surgeons. These were compared with a reference cohort of 511 knees (470 patients) of other designs (seven manufacturers) performed at the same hospital by the same surgeons. There were no significant differences in age, sex, BMI, or follow-up times between the two cohorts. The primary outcome was revision performed or pending. Results. In total, 19 (11.5%) ATTUNE study TKAs have been revised at a mean 30.3 months (SD 15), and loosening of the tibial component was seen in 17 of these (90%). Revision is pending in 12 (7%) knees. There was no difference between the 31 knees revised or with revision pending and the remaining 135 study knees in terms of patient characteristics, type of bone cement (p = 0.988), or individual surgeon (p = 0.550). In the reference cohort, there were significantly fewer knees revised (n = 13, 2.6%) and with revision pending (n = 8, 1.5%) (both p < 0.001), and only two had loosening of the tibial component as the reason for revision. Conclusion. This new TKA design had an unexpectedly high early rate of revision compared with our reference cohort of TKAs. Debonding of the tibial component was the most common reason for failure. Additional longer-term follow-up studies of this specific component and techniques for implantation are warranted. The version of the ATTUNE tibial component implanted in this study has undergone modifications by the manufacturer. Cite this article: Bone Joint J 2021;103-B(6 Supple A):137–144

Aims. Knee arthroplasty surgery is a highly effective treatment for arthritis and disorders of the knee. There are a wide variety of implant brands and types of knee arthroplasty available to surgeons. As a result of a number of highly publicized failures, arthroplasty surgery is highly regulated in the UK and many other countries through national registries, introduced to monitor implant performance, surgeons, and hospitals. With time, the options available within many brand portfolios have grown, with alternative tibial or femoral components, tibial insert materials, or shapes and patella resurfacings. In this study we have investigated the effect of the expansion of implant brand portfolios and where there may be a lack of transparency around a brand name. We also aimed to establish the potential numbers of compatible implant construct combinations. Methods. Hypothetical implant brand portfolios were proposed, and the number of compatible implant construct combinations was calculated. Results. A simple knee portfolio with cemented cruciate-retaining (CR) and posterior-stabilized (PS) components, with and without a patella, has four combinations. If there are two options available for each component, the numbers double for each option, resulting in 32 combinations. The effect of adding a third option multiplies the number by 1.3. Introducing compatible uncemented options, with the effect of hybrids, multiplies the number by 4. An implant portfolio with two femoral components (both in CR and PS), with two insert options and a patella, all in cemented and uncemented versions leads to 192 possible compatible implant construct combinations. There are implant brands available to surgeons with many more than two options. Conclusion. This study demonstrates that the addition of multiple variants within a knee brand portfolio leads to a large number (many hundreds) of compatible implant construct combinations. Revision rates of implant combinations are not currently reviewed at this level of granularity, leading to the risk of camouflage of true outcomes. Cite this article: Bone Joint J 2021;103-B(10):1555–1560

Aims. Surgeons commonly resect additional distal femur during primary total knee arthroplasty (TKA) to correct a flexion contracture, which leads to femoral joint line elevation. There is a paucity of data describing the effect of joint line elevation on mid-flexion stability and knee kinematics. Thus, the goal of this study was to quantify the effect of joint line elevation on mid-flexion laxity. Methods. Six computational knee models with cadaver-specific capsular and collateral ligament properties were implanted with a posterior-stabilized (PS) TKA. A 10° flexion contracture was created in each model to simulate a capsular contracture. Distal femoral resections of + 2 mm and + 4 mm were then simulated for each knee. The knee models were then extended under a standard moment. Subsequently, varus and valgus moments of 10 Nm were applied as the knee was flexed from 0° to 90° at baseline and repeated after each of the two distal resections. Coronal laxity (the sum of varus and valgus angulation with respective maximum moments) was measured throughout flexion. Results. With + 2 mm resection at 30° and 45° of flexion, mean coronal laxity increased by a mean of 3.1° (SD 0.18°) (p < 0.001) and 2.7° (SD 0.30°) (p < 0.001), respectively. With + 4 mm resection at 30° and 45° of flexion, mean coronal laxity increased by 6.5° (SD 0.56°) (p < 0.001) and 5.5° (SD 0.72°) (p < 0.001), respectively. Maximum increased coronal laxity for a + 4 mm resection occurred at a mean 15.7° (11° to 33°) of flexion with a mean increase of 7.8° (SD 0.2°) from baseline. Conclusion. With joint line elevation in primary PS TKA, coronal laxity peaks early (about 16°) with a maximum laxity of 8°. Surgeons should restore the joint line if possible; however, if joint line elevation is necessary, we recommend assessment of coronal laxity at 15° to 30° of knee flexion to assess for mid-flexion instability. Further in vivo studies are warranted to understand if this mid-flexion coronal laxity has negative clinical implications. Cite this article: Bone Joint J 2021;103-B(6 Supple A):87–93

Aims. The aim of this study was to assess the effect of posterior cruciate ligament (PCL) resection on flexion-extension gaps, mediolateral soft-tissue laxity, fixed flexion deformity (FFD), and limb alignment during posterior-stabilized (PS) total knee arthroplasty (TKA). Patients and Methods. This prospective study included 110 patients with symptomatic osteoarthritis of the knee undergoing primary robot-assisted PS TKA. All operations were performed by a single surgeon using a standard medial parapatellar approach. Optical motion capture technology with fixed femoral and tibial registration pins was used to assess gaps before and after PCL resection in extension and 90° knee flexion. Measurements were made after excision of the anterior cruciate ligament and prior to bone resection. There were 54 men (49.1%) and 56 women (50.9%) with a mean age of 68 years (. sd. 6.2) at the time of surgery. The mean preoperative hip-knee-ankle deformity was 4.1° varus (. sd. 3.4). Results. PCL resection increased the mean flexion gap significantly more than the extension gap in the medial (2.4 mm (. sd. 1.5) vs 1.3 mm (. sd. 1.0); p < 0.001) and lateral (3.3 mm (. sd. 1.6) vs 1.2 mm (. sd. 0.9); p < 0.01) compartments. The mean gap differences after PCL resection created significant mediolateral laxity in flexion (gap difference: 1.1 mm (. sd. 2.5); p < 0.001) but not in extension (gap difference: 0.1 mm (. sd. 2.1); p = 0.51). PCL resection significantly improved the mean FFD (6.3° (. sd. 4.4) preoperatively vs 3.1° (. sd. 1.5) postoperatively; p < 0.001). There was a strong positive correlation between the preoperative FFD and change in FFD following PCL resection (Pearson’s correlation coefficient = 0.81; p < 0.001). PCL resection did not significantly affect limb alignment (mean change in alignment: 0.2° valgus (. sd. 1.2); p = 0.60). Conclusion. PCL resection creates flexion-extension mismatch by increasing the flexion gap more than the extension gap. The increase in the lateral flexion gap is greater than the increase in the medial flexion gap, which creates mediolateral laxity in flexion. Improvements in FFD following PCL resection are dependent on the degree of deformity before PCL resection. Cite this article: Bone Joint J 2019;101-B:1230–1237

The influence of soft tissue balance in mobile-bearing posterior-stabilized (PS) total knee arthroplasty (TKA) on the patellofemoral (PF) joint was investigated in thirty varus-type osteoarthritis patients. Intraoperative soft tissue balance including joint component gap and varus/valgus ligament balance and the medial/lateral patellar pressure were measured throughout the range of motion after the femoral component placement and the PF joint repair. The lateral patellar pressure, which was significantly higher than the medial side in the flexion arc, showed inverse correlation with the lateral laxity at 60° and 90° of flexion. The lateral patellar pressure at 120° and 135° of flexion also inversely correlated with the postoperative flexion angle. Surgeons should take medial and lateral laxity into account when considering PF joint kinematics influencing postoperative flexion angle in PS TKA

Introduction. Manipulation under anesthesia (MUA) after total knee arthroplasty (TKA) helps restore range of motion. This study identifies MUA risk factors to support early interventions to improve functionality. Methods. Data was retrospectively reviewed in 2,925 primary TKAs from October 2013 through December 2015 from 13 orthopedic surgeons using hospital and private practice electronic medical records (EMR). Statistical analysis evaluated MUA and non-MUA groups, comparing demographic, operative, hospital-visit, and clinical factors. T-test, chi-square test, ANOVA and regression analysis were performed. Significance was set at p<0.05. Results. Of 2,925 TKAs, 208 MUAs were performed (7.1%) with no significant differences between groups in sex, BMI, or diabetes status. Mean age of the MUA group was 61.98 years old, and 66.89 years old in the non-MUA group (p<0.005). The ratio of MUA patients with high cholesterol was 3.37% (7/208), and 1.10% (30/2717) in the non-MUA group (p=0.014). The ratio of African-American patients in the MUA group was 6.73% (14/208), and 2.94% (80/2717) in the non- MUA group (p=0.003). Of cases with device data recorded in the EMR (n=1890), MUA incidence in patients receiving a cruciate-retaining (CR) device was 14.58% (50/343), and 9.57% (148/1547) in patients receiving a posterior-stabilized (PS) device (p=0.006). A CR-device patient was 52.35% more likely to undergo MUA than a PS-device patient (95% CI, 1.13–2.05). MUA rate by surgeon training was 6.7% for joint fellowship, 6.8% for general fellowship, and 12.0% for sports medicine fellowship (p=0.015). Further analysis showed that rate of CR-device use was 13.3% for joint-fellowship trained surgeons, 10.2% for general fellowship, and 74.7% for sports medicine fellowship (p<0.001). With the numbers available for this investigation, there were no significant differences found between groups in relation to surgeon, high-volume (>150 TKAs annually) or low-volume surgeons, length of stay, discharge disposition, or smoking status. Conclusion. MUA risk factors include a lower mean age, high cholesterol, African-American, surgeon fellowship training, and receiving a cruciate-retaining device

Introduction. There is current debate concerning the most biomechanically advantageous knee implant systems, and there is also currently great interest in improving patient satisfaction after knee arthroplasty. Additionally, there is no consensus whether a posterior-stabilized (PS) total knee device is superior to a more congruent, cruciate-substituting, medially-stabilized device (MS). This study compared the clinical outcomes of two such devices. The primary hypothesis was that the clinical outcomes, and specifically the patient satisfaction as measured by the Forgotten Joint Score, would be better in the MS group. Methods. This prospective, randomized, blinded Level 1 study compared the outcomes of 100 patients who received a Medacta GMK PS device and 101 patients who received a Medacta GMK medially-stabilized Sphere device (Medacta Intl., Lugano, Switzerland). All patients undergoing elective primary total knee arthroplasty were eligible for participation. Institutional Review Board approval and informed consent from participants were obtained. The devices were implanted using an anatomic alignment/calipered- measured resection surgical approach. Clinical and radiographic assessments were performed preoperatively, 6 weeks, 6 months, and annually. Data were compared using T-test with a significance level of 0.05. Results. The minimum follow-up period is 2 years. There were no statistically significant differences in demographic characteristics and preoperative scores; tourniquet time was 7.24% longer for the PS group (40.28 min vs 37.56 min, P < .0086). Alignment was not different between the groups (preoperative or postoperative). There were significant differences between groups for the 1 year and 2 years postop Knee Society scores, Forgotten Joint Score, and ROM; in every case where there was a statistically significant difference, the results were better in the MS group. For example, the FJS was 65.72 in the MS group at 2 years, 54.33 in the PS group (p=0.02). The maximum active flexion at 2 years was 129.75º in the MS group, in the PS group it was 122.27º (p=0.03). Conclusion. The clinical outcomes of the MS group at 1 and 2 years, including the Forgotten Joint Score and flexion, were better statistically, and there was a statistically longer tourniquet time for the PS group. At the minimum 2-year follow-up, the results demonstrate superiority of the medially-stabilized device in terms of multiple clinical outcomes, including patient satisfaction as measured by the Forgotten Joint Score. These findings support the use of a medially-stabilized knee implant system, and support the conclusion that this design, in conjunction with an anatomic alignment, calipered-measured resection surgical technique, offers improved biomechanics and kinematics

Background. The posterior slope of the tibial component in total knee arthroplasty (TKA) has been reported to vary widely even with computer assisted surgery. In the present study, we analyzed the influence of posterior tibial slope on one-year postoperative clinical outcome after posterior-stabilized (PS) -TKA to find out the optimal posterior slope of tibial component. Materials and Method. Seventy-three patients with varus type osteoarthritic (OA) knees underwent PS-TKA (Persona PS. R. ) were involved in this study. The mean age was 76.6 years old and preoperative HKA angle was 14.3 degrees in varus. Tibial bone cut was performed using standard extra-medullary guide with 7 degrees of posterior slope. The tibial slopes were radiographically measured by post-operative lateral radiograph with posterior inclination in plus value. The angle between the perpendicular line of the proximal fibular shaft axis and the line drawn along the superior margin of the proximal tibia represented the tibial slope angle. We assessed one-year postoperative clinical outcomes including active range of motion (ROM), patient satisfaction and symptoms scores using 2011 Knee Society Score (2011 KSS). The influences of posterior tibial slope on one-year postoperative parameters were analyzed using simple linear regression analysis (p<0.05). Results. The average posterior tibial slope was 6.4 ± 2.0 °. The average active ROM were −2.4 ± 6.6 ° in extension and 113.5± 12.6 ° in flexion. The mean one-year postoperative patient satisfaction and symptom scores were 29.3 ± 6.4 and 19.6 ± 3.9 points respectively. The active knee extension, satisfaction and symptom scores were significantly negatively correlated to the posterior tibial slope (r = −0.25, −0.31, −0.23). Discussion. In the present study, we have found significant influence of the posterior tibial slope on the one-year postoperative clinical outcomes in PS-TKA. The higher posterior slope would induce flexion contracture and deteriorate patient satisfaction and symptom. We had reported that the higher tibial posterior slope increased flexion gap and the component gap change during knee flexion in PS-TKA. Furthermore, another study reported that increase of the posterior tibia slope reduced the tension in the collateral ligaments and resulted in the knee laxity at flexion. The excessive posterior slope of tibial component would result in flexion instability, and adversely affected the clinical results including patient satisfaction and symptom. Conclusion. In the PS-TKA for varus type OA knees, excessive tibial posterior slope was found to adversely affect one-year postoperative knee extension and clinical outcome including patient satisfaction and symptom. Surgeons should aware of the importance of tibial slope on one-year postoperative clinical results and pay more attentions to the posterior tibial slope angle not to be excessive

Whether it is best to retain the posterior cruciate ligament in the degenerated knee, i.e. using a cruciate-retaining (CR) total knee prosthesis (TKP), or to use a more constraint posterior-stabilized (PS) TKP is of debate. There are limited studies comparing the effect of both methods on implant fixation and clinical outcome, leaving it up to the surgeon to base this decision on anything but conclusive evidence. We assessed the effect of two different philosophies in knee arthroplasty on clinical outcome and tibial component migration measured with radiostereometric analysis (RSA), by directly comparing the CR and PS version of an otherwise similarly designed cemented TKP. Sixty patients were randomized and received a Triathlon TKP (Stryker, NJ, USA) of either CR (n=30) or PS (n=30) design. RSA measurements (primary outcome) and clinical scores including the Knee Society Score and Knee injury and Osteoarthritis Outcome Score were evaluated at baseline, at three months postoperatively and at one, two, five and seven years. A linear mixed-effects model was used to analyse the repeated measurements. Both groups showed a similar implant migration pattern, with a maximum total point motion at seven years follow-up of around 0.8 mm of migration (mean difference between groups 95% CI −0.11 to 0.15mm, p=0.842). Two components (one of each group) were considered to have an increased risk of aseptic loosening. Both groups improved equally after surgery on the KSS and KOOS scores and no differences were seen during the seven years of follow-up. No differences in implant migration nor clinical results were seen seven years after cruciate-retaining compared to posterior-stabilized total knee prostheses

Introduction. Modified gap technique has been reported to be beneficial for the intraoperative soft tissue balancing in posterior-stabilized (PS) -TKA. We have found intraoperative ligament balance changed depending on joint distraction force, which might be controlled according to surgeons' fells. We have developed a new surgical concept named as “medial preserving gap technique (MPGT)” to preserve medial knee stability and provide quantitative surgical technique according to soft tissue balance measurement using a tensor device. The purpose of this study was to compare 3-years postoperative knee stability after PS-TKA in varus type osteoarthritic (OA) knees between MPGT and measured resection technique (MRT). Material & Method. The subjects were 94 patients underwent primary unilateral PS-TKA for varus type OA knees. The surgical technique was MPGT in 47 patients and MRT in 47 patients. An originally developed off-set type tensor device was used to evaluate intraoperative soft tissue balance. In MPGT, medial release was limited until the spacer block corresponding to the bone thickness from proximal lateral tibial plateau could be easily inserted. Femoral component size and external rotation angle were adjusted depending on the differences of center gaps and varus angles between extension and flexion before posterior femoral condylar resection. The knee stabilities at extension and flexion were assessed by stress radiographies at 1 and 3 years after TKA; varus-valgus stress test at extension and stress epicondylar view at flexion. We measured medial and lateral joint openings (MJO, LJO) at both knee extension and flexion. MJOs and LJOs at 2 time periods were compared in each group using paired t-test. Each joint opening distance was compared between 2 groups using unpaired t-test. The significance level was set as P < 0.05. Results. The mean extension MJOs at 1 and 3 years after TKA were 2.4, 2.6 mm in MPGT and 3.2, 3.1 mm in MRT respectively. The mean extension LJOs were 3.5, 3.5 mm in MPGT and 4.6, 4.5 mm in MRT. The mean flexion MJOs were 0.95, 0.77 mm in MPGT and 1.5, 1.2 mm in MRT, and the mean flexion LJOs were 2.2, 2.1 mm in MPGT and 3.0, 2.7 mm in MRT. MJOs were significantly smaller than LJOs in each group at 2 time periods. MJOs at extension and flexion, and LJOs at extension were significantly smaller in MPGT than MRT at 2 time periods. Discussion. Medial knee stabilities had been reported to be essential for postoperative clinical results. We reported medial compartment gap was more stable during mid-to-deep knee flexion in MPGT than MRT. MPGT provided the more stable intraoperative soft tissue balance than MRT in PS-TKA. MPGT was useful to preserve the higher medial knee stability than the lateral as well as MRT, and beneficial to enhance postoperative knee stabilities as long as 3-years after PS-TKA in varus OA knees. MPGT would be an objective and safer gap technique to enhance clinical outcomes

Using a tensor for total knee arthroplasty (TKA) that is designed to facilitate soft tissue balance measurements with a reduced patello-femoral (PF) joint, we examined the influence of pre-operative deformity on intra-operative soft tissue balance during posterior-stabilized (PS) TKA. Joint component gap and varus angle were assessed at 0, 10, 45, 90 and 135° of flexion with femoral trial prosthesis placed and PF joint reduced in 60 varus type osteoarthritic patients. Joint gap measurement showed no significant difference regardless the amount of pre-operative varus alignment. With the procedures of soft tissue release avoiding joint line elevation, however, intra-operative varus angle with varus alignment of more than 20 degrees exhibited significant larger values compared to those with varus alignment of less than 20 degrees throughout the range of motion. Accordingly, we conclude that pre-operative severe varus deformity may have the risk for leaving post-operative varus soft tissue balance during PS TKA

Introduction:. Proper component orientation and soft tissue balancing are essential for longevity of total knee arthroplasty (TKA), especially in young and active patients. The aim of this study was to evaluate long-term results and quality of TKA in young and active patients with extension first gap balancing technique, in 2 Posterior-Stabilized (PS) total knee designs with identical femoral component. Material and Methods:. 43 consecutive Rotating-Platform (RP-PS, 33 patients) and 38 Fixed-Bearing (FB-PS, 29 patients) with University of California Los Angeles (UCLA) activity score of 5 or above and mean age was 53 ± 1.5 years were followed prospectively for a minimum of 10 years. 18 random TKAs were analyzed for component rotation using MRI. Results:. The majority of patients (77%, 24 patients in RP-PS and 65%, 25 patients in FB-PS) were still participating in recreational activities at final follow-up. There was no case of early or late mid flexion instability causing spinout. There was no malalignment or patellofemoral maltracking. Non-progressive radiolucency was seen at the tibial zone 1 in one of the RP-PS and 3 of the FB-PS knees. The mean femoral rotation was 2 and 3 degrees of external in relation to the transepicondylar axis in RP-PS and in FB-PS, respectively. Two patients in the FB-PS were revised (one for per-prosthetic fracture and one for osteolysis and loosening). There were no revisions in the RP-PS group. Kaplan-Meier survivorship at 10 years was 100% in RP-PS and 97% in FB-PS. Discussion and Conclusions:. Extension first gap balancing technique is a safe, accurate, and reproducible with excellent alignment and long-term durability and high quality of function in young, active patients

Purpose. To investigate the tibiofemoral rotational profiles during surgery in navigated posterior-stabilized (PS) total knee arthroplasty (TKA) and investigated the effect on postoperative maximum flexion angles. Materials and Methods. At first, twenty-five consecutive subjects (24 women and 1 man; age: mean, 77 years; range, 58–85 years) with varus osteoarthritis treated with navigated PS TKA (Triathlon, Stryker, Mahwah, NJ) were enrolled in this study. Kinematic parameters, including the tibiofemoral rotational angles from maximum extension to maximum flexion, were recorded thrice before and after PCL resections, and after implantation. The effect of PCL resection and component implantation on tibiofemoral rotational kinematics was statistically evaluated. Then, the effect of tibiofemoral rotational alignment changes on the postoperative maximum angles were retrospectively examined with 96 subjects (84 women, 12 men; average age, 76 years; age range, 56–88 years) who underwent primary TKA. Results. The tibiofemoral kinematics revealed a significant tibial internal rotation after PCL resection, which further increased after implantation compared with that before PCL resection (p < 0.01 and p < 0.001, respectively). Furthermore, the tibial internal rotations at 60° and 90° flexion after PCL resection and implantation were significantly increased compared with those before PCL resection (p < 0.05). The amount of tibial internal rotation from 90° flexion to maximum flexion was significantly decreased after PCL resection and implantation compared with that before PCL resection (p < 0.05). Furthermore, multi-linear regression analysis found that the internal changes of the rotational alignment was independent factor for the worse improvement of the postoperative maximum flexion angles (R2=0.078, p=0.0067). There was a positive correlation between preoperative tibial external rotational alignment and the internal changes of the postoperative rotational alignment (R2=0.172, p<0.0001), however, no correlation was found between the preoperative rotational alignment and the improvement of the maximum flexion angles. Discussion and Conclusion. The study revealed that PCL resection changed the tibial rotational alignment and decreased the amount of tibial internal rotation. The implantation of PS components further increased the internal rotational alignment and could not compensate for the tibiofemoral rotation. Finally, the internal changes of rotational alignment affected the improvement of the maximum flexion angles, suggesting that rotational alignment is one of important factors to achieve better postoperative maximum flexion angles. Although the factors which affect the rotational alignment remains unknown in this study, these results suggest that further development of PS TKA, including the surgical technique and implant design, are needed to achieve better knee kinematics, following better clinical outcomes

Backgrounds. In order to permit soft tissue balancing under more physiological conditions during total knee arthroplasties (TKAs), we developed an offset type tensor to obtain soft tissue balancing throughout the range of motion with reduced patella-femoral (PF) and aligned tibiofemoral joints and reported the intra-operative soft tissue balance assessment in cruciate-retaining (CR) and posterior-stabilized (PS) TKA [1, 2]. However, the soft tissue balance in unicompartmental knee arthroplasty (UKA) is unclear. Therefore, we recently developed a new tensor for UKAs that is designed to assist with soft tissue balancing throughout the full range of motion. The first purpose of the present study is to assess joint gap kinematics in UKA. Secondly, we attempted to compare the pattern in UKA with those in CR and PS TKA with the reduced PF joint and femoral component placement, which more closely reproduces post-operative joint alignment. Methods. Using this tensor, we assessed the intra-operative joint gap measurements of UKAs performed at 0, 10, 30, 45, 60, 90, 120 and 135° of flexion in 20 osteoarthritic patients. In addition, the kinematic pattern of UKA was compared with those of CR and PS TKA that were calculated as medial compartment gap from the previous series of this study. Results. While the joint gap measurements of UKAs increased from full extension to extension (10 degrees of flexion), these values remained constant throughout the full range of motion. Of note, the gap values of CR TKA were significantly smaller from midrange to deep flexion compared with PS TKA, and furthermore UKA showed a significantly smaller gap from extension to midrange flexion compared with CR TKA. Conclusions. Accordingly, we conclude that the intra-operative joint gap kinematic pattern in UKA differs from the pattern in TKA

INTRODUCTION. Although several meta-analyses have been performed on total knee arthroplasty (TKA) using computer-assisted orthopaedic surgery (CAOS) [1], understanding the inter-site variations of the surgical profiles may improve the interpretation of the results. Moreover, information on the global variations of how TKA is performed may benefit the development of CAOS systems that can better address geographic-specific operative needs. With increased application of CAOS [2], surgeon preferences collected globally offers unprecedented opportunity to advance geographic-specific knowledge in TKA. The purpose of this study was to investigate geographic variations in the application of a contemporary CAOS system in TKA. Materials and Methods. Technical records on more than 4000 CAOS TKAs (ExactechGPS, Blue-Ortho, Grenoble, FR) between October 2012 and January 2016 were retrospectively reviewed. A total of 682 personalized surgical profiles, set up based on surgeon's preferences, were reviewed. These profiles encompass an extensive set of surgical parameters including the number of steps to be navigated, the sequence of the surgical steps, the definition of the anatomical references, and the parameters associated with the targeted cuts. The profiles were compared between four geographic regions: United States (US), Europe (EU), Asia (AS), and Australia (AU) for cruciate-retaining (CR) and posterior-stabilized (PS) designs. Clinically relevant statistical differences (CRSD, defined as significant differences in means ≥1°/mm) were identified (significance defined as p<0.05). Results. For resection parameters, CRSDs were found between regions in posterior tibial slope (PTS), tibial resection depth, as well as femoral flexion for both CR and PS profiles (marked in Table 1). Regarding anatomical references, US was the only region using posterior cruciate ligament (PCL) as the reference for CR resection depth (Table 1). Differences in percentage of preference were found in the anatomical references for tibial varus/valgus, tibial resection depth, femoral varus/valgus, femoral axial rotation, and ankle center (Table 1,2). For surgical steps, EU and AU were found to apply gap balancing technique as a common practice for the PS designs, while for the CR designs, EU and AU considerably adopted this technique (Table 2). For PS designs, EU and AU profiles preferred tibial first in the resection workflow, compared to a more balanced preference for other regions. For CR designs, US profiles were in favour of performing the femoral resection first in the workflow, compared to a strong favouring of tibial first resection workflow in EU and AS Am regions. Discussion. This study demonstrated clinically significant geographic differences may exist in the surgeons' preference of surgical parameters, anatomical references, and surgical workflow steps during TKA. These differences may reflect the geographic variations of surgeon training, surgical philosophy, or the specific characteristics of the patient population, which warrants further investigation. The strength of this study was that it is the first study to date that covered all the available surgical profiles spanning the application history of a specific CAOS system. As such, variation due to the operational differences of multiple systems was avoided. For any figures or tables, please contact authors directly (see Info & Metrics tab above).