INTRODUCTION

Contemporary PCL sacrificing Total Knee Arthroplasty (TKA) implants (CS) consist of symmetric medial and lateral tibial articular surfaces with high anterior lips designed to substitute for the stability of the native PCL. However, designs vary significantly across implant systems in the level of anteroposterior constraint provided. Therefore, the goal of this study was to investigate kinematics of two CS designs with substantially different constraint levels. The hypothesis was that dynamic knee simulations could show the effect of implant constraint on kinematics of CS implants.

The posterior drawer is a commonly used test to diagnose an isolated PCL injury and combined PCL and PLC injury. Our aim was to analyse the effect of tibial internal and external rotation during the posterior drawer in isolated PCL and combined PCL and PLC deficient cadaver knee.

Ten fresh frozen and overnight-thawed cadaver knees with an average age of 76 years and without any signs of previous knee injury were used. A custom made wooden rig with electromagnetic tracking system was used to measure the knee kinematics. Each knee was tested with posterior and anterior drawer forces of 80N and posterior drawer with simultaneous external or internal rotational torque of 5Nm. Each knee was tested in intact condition, after PCL resection and after PLC (lateral collateral ligament and popliteus tendon) resection. Intact condition of each knees served as its own control. One-tailed paired student's t test with Bonferroni correction was used.

The posterior tibial displacement in a PCL deficient knee when a simultaneous external rotation torque was applied during posterior drawer at 90° flexion was not significantly different from the posterior tibial displacement with 80N posterior drawer in intact knee (p=0.22). In a PCL deficient knee posterior tibial displacement with simultaneous internal rotation torque and posterior drawer at 90° flexion was not significantly different from tibial displacement with isolated posterior drawer. In PCL and PLC deficient knee at extension with simultaneous internal rotational torque and posterior drawer force the posterior tibial displacement was not significantly different from an isolated PCL deficient condition (p=0.54).

We conclude that posterior drawer in an isolated PCL deficient knee could result in negative test if tibia is held in external rotation. During a recurvatum test for PCL and PLC deficient knee, tibial internal rotation in extension results in reduced posterior laxity.

In performing posterior cruciate ligament- retaining total knee arthroplasty (CR-TKA), the original surgical instrument was devised to obtain the range of motion and stability of the knee joint adequate for daily life of Japanese people. We have presumed the tentative joint line as intercondylar notch point of the distal femur, and performed surgery using surface replacement to resect metal width of the femoral component for the distal femur by setting the knee to the original position based on understanding of the shape of anterior curvature of the distal femur in Japanese people in case of implanting the femoral component. In order to obtain stability of the knee, we have minimally released the soft tissue and resected the anterior cruciate ligament (ACL), whereas completely preserved the posterior cruciate ligament (PCL) and maintained physiological ligament balance of the knee joint by resecting the medial condyle of the tibia (genu varus). Our surgical procedure enabled deep flexion knee (knee embracing) greater than 145 degrees in 9.7% and also allowed Japanese sitting in three different designs of total knee joints

INTRODUCTION. Over the past 40 years of knee arthroplasty, significant advances have been made in the design of knee implants, resulting in high patient satisfaction. Patellar tracking has been central to improving the patient experience, with modern designs including an optimized Q-angle, deepened trochlear groove, and thin anterior flange.[1–4] Though many of today's femoral components are specific for the left and right sides, Total Joint Orthopedics’ (TJO) Klassic® Knee System features a universal design to achieve operating room efficiencies while providing all the advancements of a modern knee. The Klassic Femur achieves this through a patented double Q-angle to provide excellent patellar tracking whether implanted in the left or the right knee (Figure 1). The present study examines a prospective cohort of 145 consecutive TKA's performed using a modern universal femur and considers patients’ pre- and post-operative Knee Society Clinical Rating System score (KSS). METHODS AND MATERIALS. 145 primary total knee arthroplasties (TKA) were performed during the study using a measured resection technique with a slope-matching tibial cut for all patients. The posterior cruciate ligament (PCL) was sacrificed to accommodate an ultra-congruent polyethylene insert. The distal femur was cut at five degrees (5°) valgus; the tibia was resected neutral (0°) alignment for valgus legs and in two degrees (2°) of varus for varus alignment. The patella was resurfaced for all patients. Patients were followed annually for up to 46 months and were evaluated using the KSS score on a 200-point scale. RESULTS. The final study group comprised 127 primary TKAs. The average age was 68 years (51–90) with 45 males and 68 females. The average weight was 110kg (range: 75–151kg) for men and 88kg (range: 50–129kg) for women. One patient deceased during the follow-up period, four required manipulation under anesthesia, and two required revision for periprosthetic joint infection. There were no failures due to patellar maltracking. No special soft tissue releases were required in any patient. Average pre-operative knee score was 107, improving to 182 at average follow-up of 41 months (36–46 months). Results are summarized in Table 1. DISCUSSION. The improvement in patient clinical experience demonstrates that a universal femoral design can achieve excellent results if it incorporates modern technologies. A double Q-angle design with a deepened trochlear groove and a thin anterior flange appears to provide excellent patellar tracking for all patients in this cohort. This study is limited to the experience of a single institution. Further study would improve the extensibility of these findings. It does show, however, that a femur using a universal design with modern patellar tracking can improve patient satisfaction with their knee following TKA. For any figures or tables, please contact the authors directly

Patient expectations have escalated over the past several decades with respect to demand for success with total knee arthroplasty (TKA). It is reported that 15 to 20% of TKA recipients are unsatisfied with their result. Dynamic fluoroscopic studies and gait analyses have demonstrated that patients with TKA do not exhibit normal kinematics. On the other hand, patients with partial knee arthroplasty demonstrate more normal kinematics, thought to be secondary to retention of the anterior cruciate ligament (ACL) along with the posterior cruciate ligament (PCL). While not a new concept, bi-cruciate retaining designs in TKA that preserve the natural ligament structure of the knee are drawing renewed interest as an option for patients with higher and more complex activity demand. These designs may result in a more natural kinematic feel as perceived by the patient. This surgical demonstration will outline patient selection criteria and illustrate the technique for performing ACL- and PCL-preserving, bi-cruciate retaining TKA

One of the key factors responsible for altered kinematics and joint stability following contemporary total knee arthroplasty (TKA) is resection of the anterior cruciate ligament (ACL). Therefore, retaining the ACL is often considered to be the “holy grail” of TKA. However, ACL retention can present several technical challenges, and in some cases may not be viable due to an absent or non-functional ACL. Therefore, the goal of this research was to investigate whether substitution of ACL function through an anterior post mechanism could improve kinematic deficits of contemporary posterior cruciate ligament (PCL) retaining (CR) implants. This was done using KneeSIM, a previously established dynamic simulation tool based on an Oxford-rig setup. Deep knee bend, chair-sit, stair-ascent and walking were simulated for a contemporary ACL sacrificing (CR) implant, two ACL retaining implants, and an ACL substituting and PCL retaining implant. The motion of the femoral condyles relative to the tibia was recorded for kinematic comparisons. Our results revealed that, like ACL retaining implants, the ACL substituting implant could also provide kinematic improvements over contemporary ACL sacrificing implants by reducing early posterior femoral shift and preventing paradoxical anterior sliding. Such ACL substituting implants may be a valuable addition to the armament of joint surgeons, allowing them to provide improved knee function even when ACL retention is not feasible. Further research is required to investigate this mechanism in vitro and in vivo to verify the results of the simulations, and to determine whether kinematic improvements translate into improved clinical outcomes

Introduction. Ligament reconstruction following knee soft tissue injuries, such as posterior cruciate ligament (PCL) tears, aim to restore normal joint function and motion; however, persistant pathomechanical joint behavior indicates that there is room for improvement in current reconstruction techniques. Increased attention is being directed towards the roles of secondary knee stabilizers, in an attempt to better understand their contributions to kinematics of knees. The objective of this study is to characterize the relative biomechanical contributions of the posterior oblique ligament (POL) and the deep medial collateral ligament (dMCL) in PCL-deficient knees. We hypothesized that, compared with the POL, the dMCL would have a more substantial role in stabilizing the medial side of the knee, especially in flexion (slack POL). Methods. Seven fresh-frozen cadaveric knees were used in this study (age 40–62, 4 female, 3). Specimens were potted and mounted onto a VIVO joint motion simulator (AMTI). Once installed, specimens were flexed from 0 to 90 degrees with a 10 N axial load and all remaining degrees of freedom unconstrained. This was repeated with (a) a 67 N posterior load, (b) a 2.5 Nm internal or external rotational moment and (c) a 50 N posterior load and 2.5 Nm internal rotational moment applied to the tibia. During each resulting knee motion, the relative AP kinematics of the dMCL tibial insertion (approximated as the most medial point of the proximal tibia) with respect to the flexion axis of the femur (the geometric center axis, based on the posterior femoral condyles) were calculated at 0, 30, 60 and 90 degrees of flexion. These motions were repeated following dissection of the PCL and then further dissection of either medial ligament (4 POL, 3 dMCL). The changes in AP kinematics due to ligament dissection were analyzed using three-way repeated-measures ANOVA with a significance value of 0.05. Results. Dissection of the dMCL or POL did not result in a statistically significant increase in the posterior displacement of the medial tibial point under posterior directed force, internal rotation moments, or the combined posterior force plus internal rotation moment. Interestingly, under external moment loading, there was a statistically significant increase in anterior displacement of the medial tibia at all flexion angles after POL dissection, by up to 3.0+/−2.6 mm at 0 degrees. Dissection of the dMCL, however, did not have a significant affect. Conclusion. Our results showed that neither the POL nor dMCL play a significant role in resisting posterior tibial displacements on the medial side of a PCL deficient knee. Of the two, the POL appears to have a greater contribution towards preventing anterior translations, particularly when in extension. This finding is rational based on the anatomical path of this ligament wrapping around the femoral medial condyle under external rotational moments. In contrast with our hypothesis, it was observed that the dMCL had less of an effect on medial knee stability. Contributions of these ligaments could be further investigated using more complicated loading, such as those more representative of activities of daily living

Introduction. In total knee arthroplasty (TKA) the knee may be found to be too stiff in extension, causing a flexion contracture. One proposed surgical technique to correct this extension deficit is to recut the distal femur, but that may lead to excessively raising the joint line. Alternatively, full extension may be gained by stripping the posterior capsule from its femoral attachment, however if this release has an adverse impact on anterior-posterior (AP) stability of the implanted knee then it may be advisable to avoid this technique. The aim of the study was therefore to investigate the effect of posterior capsular release on AP stability in TKA, and compare this to the restraint from the cruciate ligaments and different TKA inserts. Methods. Eight cadaveric knees were mounted in a six degree of freedom testing rig (Fig.1) and tested at 0°, 30°, 60° and 90° flexion with ±150 N AP force, with and without a 710 N axial compressive load. The rig allowed an AP drawer to be applied to the tibia at a fixed angle of flexion, whilst the other degrees-of-freedom were unconstrained and free to translate/ rotate. After the native knee was tested with and without the anterior cruciate ligament (ACL), a cruciate-retaining TKA (Legion; Smith & Nephew) was implanted and the tests repeated. The following stages were then performed: replacing with a deep dished insert, cutting the posterior cruciate ligament (PCL), releasing the posterior capsule using an osteotome (Fig. 2), replacing with a posterior-stabilised implant and finally using a more-constrained insert. Results. In anterior drawer, only cutting the ACL caused a large increase in laxity compared to the native state (8 mm average across all flexion angles). At 0°, releasing the posterior capsule increased the laxity by 1.4 mm compared with cutting the PCL (p < 0.05), with no significance found at any other flexion angles. In posterior drawer with no compressive load, cutting the PCL significantly increased laxity at 30°, 60° and 90° (average 7 mm), however additional release of the posterior capsule only increased laxity by 1.5 mm and 0.8 mm at 0° and 30° respectively. At 30°, 60° and 90°, posterior stability was significantly restored by introducing a posterior-stabilised or more-constrained insert. When a 710 N compressive load was applied. Conclusions. The most important finding of the study was that releasing the posterior capsule did not cause a clinically large difference in AP laxity in context with cutting the PCL. Therefore, releasing the posterior capsule to restore extension during TKA surgery could be considered a biomechanically safe option. In cases of posterior instability due to PCL and capsular damage, a posterior-stabilised insert can restore stability, particularly in mid to late flexion. Future studies could compare this data to isolated implant constraints, to help investigate how much stability is provided by the different implant geometries compared to the PCL and posterior capsule

Background. To prevent excessive tension on the posterior cruciate ligament (PCL) in cruciate-retaining total knee arthroplasty (CR-TKA), some knee prosthesis-systems offer the option of creating a posterior slope for the tibial polyethylene insert. Vanguard® Complete Knee System offers two different types of tibial bearing for CR. -TKA. CR Lipped Bearing (LB) has a slightly raised posterior lip, whereas CR Standard Bearing (SB) is recessed downward at the posterior margin and has 3° posterior slope. The objective of this study was to investigate the effect of the tibial bearing slope on PCL load using the original devise in vivo conditions. Material and Methods. Twenty osteoarthritic varus knees were included in this study. After implantation of the trial components, PCL stiffness was measured using the original tension analyzer intra-operatively. Elastic modulus of PCL was calculated at 90 and 120 degrees knee flexion on two types of bearing surface. Results. Elastic modulus of PCL was 7.2±0.9 N/mm (mean±SE) at 90 degrees knee flexion, and 9.5±1.1 N/mm (mean±SE) at 120 degrees knee flexion with the Lipped Bearing (no slope). With the Standard Bearing (3 degrees posterior slope), elastic modulus decreased to 6.0±0.5 N/mm (mean±SE) at 120 degrees knee flexion. Discussion and Conclusion. Higher PCL stiffness was observed at 120 degrees knee flexion than 90 degrees knee flexion with Lipped Bearing surface (no slope), but using the Standard Bearing (3 degrees posterior slope), PCL stiffness decreased significantly at 120 degrees knee flexion. Therefore a posterior tibial slope of bearing insert prevents an excessive load on PCL at high knee flexion angles

It is a well-known fact that total knee arthroplasty is a soft tissue operation. Soft tissue balancing is the key to success in total knee arthroplasty. It is paramount importance to preserve the maximal amount of bone on both the femur and tibial side. In Indian scenario, majority of the patients present relatively late with varus or valgus deformity. Adding to this problem is poor bone quality due to osteoporosis. Our technique of Posterior cruciate ligament (PCL) retaining TKA with tibial end plate resection facilitates soft tissue balancing, preserves PCL and maximizes bone preservation on both tibial and femoral side achieving good results in minimum seven year follow up. We retrospectively analyzed seven year outcomes of 120 knees (110 patients), mean age was 65 years (range 55 to 75 years), who received contemporary cruciate-retaining prostheses with tibial end plate resection technique. The diagnosis was osteoarthritis in 96%, Rheumatoid arthritis in 2% and posttraumatic arthritis in 2% cases. There were more number of flexible varus knees as compared to flexible valgus knees. All the patients were followed up for minimum of 84 months with average follow up of 96 months. They were followed up at 3mths, 6mths, 1,3,5,7,9 and 10 years. The functional assessment was done using knee society knee and function scores. Radiographic analysis was done to rule out subsidence and aseptic loosening. The statistical significance was assessed using chi square test. Survival analysis was done using the Kaplan Meier analysis with revision taken as the endpoint. The average ROM was 100 degrees preoperatively and 120 degrees at last follow-up. The average knee society knee score improved from 45 points preoperatively to 90 points at last follow-up. The average knee society functional score improved from 48 points preoperatively to 84 points at last follow-up (p<0.05). Radiolucency was observed in 20 knees but all except four were non-progressive lesions smaller than 2 mm. None of the implants were revised for subsidence or aseptic loosening of tibial component. The technique of PCL retaining total knee arthroplasty with tibial end plate resection in arthritic knees with flexible varus or valgus deformity yields good functional outcome in medium term follow up with relatively low incidence of subsidence of the tibial implant. This technique appears promising for total knee arthroplasty in osteoporotic bones where retaining the strong subchondral bone increases the longevity of the implant

Introduction. There is little information available to surgeons regarding how the lateral soft-tissue structures prevent instability in knees implanted with total knee arthroplasty (TKA). The aim of this study was to quantify the lateral soft-tissue contributions to stability following cruciate retaining (CR) TKA. Methods. Nine cadaveric knees with CR TKA implants (PFC Sigma; DePuy Synthes Joint Reconstruction) were tested in a robotic system (Fig. 1) at full extension, 30°, 60°, and 90° flexion angles. ±90 N anterior-posterior force, ±8 Nm varus-valgus and ±5 Nm internal-external torque were applied at each flexion angle. The anterolateral structures (ALS, including the iliotibial band, anterolateral ligament and anterolateral capsule), the lateral collateral ligament (LCL), the popliteus tendon complex (Pop T) and the posterior cruciate ligament (PCL) were then sequentially transected. After each transection the kinematics obtained from the original loads were replayed, and the decrease in force / moment equated to the relative contributions of each soft-tissue to stabilising the applied loads. Results. In the CR TKA knee, the LCL was found to be the primary restraint to varus laxity (Fig. 2, an average 56% across all flexion angles), and was significant in internal-external rotational stability (28% and 26% respectively) and anterior drawer (16%). The ALS restrained 25% of internal rotation (Fig. 3), whilst the PCL was significant in posterior drawer only at 60° and 90° flexion. The Pop T was not found to be significant in any tests. Conclusion. This study has for the first time delineated the relative contributions of lateral structures to stability in the implanted knee. It was confirmed that the LCL is the major lateral structure in CR TKA stability throughout the arc of flexion. In the event of LCL deficiency, stability of the knee may only be restored by either changing to a more constrained implant or performing a reconstruction of the ligament. Furthermore, care should be taken when releasing the LCL to correct a valgus deformity as it may result in a combined rotational laxity pattern that cannot be overcome by the other passive lateral structures or the PCL. For figures, please contact authors directly

PURPOSE. Total knee arthroplasty (TKA) is a successful technique for treating painful osteoarthritic knees. However, the patients' satisfaction is not still comparable with total hip arthroplasty. Basically, the conditions with operated joints were anterior cruciate ligament (ACL) deficient knees, thus, the abnormal kinematics is one of the main reason for the patients' incomplete satisfaction. Bi-cruciate stabilized (BCS) TKA was established to reproduce both ACL and posterior cruciate ligament (PCL) function and expected to improve the abnormal kinematics. However, there were few reports to evaluate intraoperative kinematics in BCS TKA using navigation system. Hence, the aim in this study is to reveal the intraoperative kinematics in BCS TKA and compare the kinematics with conventional posterior stabilized (PS) TKA. Materials and Methods. Twenty five consecutive subjects (24 women, 1 men; average age, 77 years; age range, 58–85 years) with varus osteoarthritis undergoing navigated BCS TKA (Journey II, Smith&Nephew) were enrolled in this study. An image-free navigation system (Stryker 4.0 image-free computer navigation system; Stryker) was used for the operation. Registration was performed after minimum medial soft tissue release, ACL and PCL resection, and osteophyte removal. Then, kinematics including tibiofemoral rotational angles from maximum extension to maximum flexion were recorded. The measurements were performed again after implantation. We compared the kinematics with the kinematics of paired matched fifty subjects who underwent conventional posterior stabilized (PS) TKA (25 subjects with Triathlon, Stryker; 25 subjects with PERSONA, ZimmerBiomet) using navigation statistically. Results. Preoperative tibiofemoral rotational kinematics were almost the same between the three implants groups. Kinematics at post-implantation found that tibia was significantly internally rotated compared to the kinematics at registration in all three implants at maximum extension position (p<0.05), however the tibial rotational position with BCS TKA was significantly externally rotated at maximum extension position, compared to the other two implant position (p<0.05). The tibial rotational position with Triathlon PS TKA was externally rotated at 60 degrees of flexion compared to the other two implant position, however the results were not statistically significant. Discussion and Conclusion. Previous study found that PCL resection changed tibial rotational position and the amount of tibial internal rotation, affecting postoperative maximum flexion angles. This study found that BCS TKA can reduce the amount of rotational changes, compared to conventional PS TKA. Further studies are needed to investigate the kinematic changes in BCS TKA affect the postoperative clinical outcomes

Introduction. The purpose of this study was to determine whether the patient's perceived outcome and speed of recovery differs between a posterior cruciate ligament (PCL) substituting (cam-post type) and PCL sacrificing (ultracongruent polyethylene) total knee arthroplasty (TKA). Methods. Thirty eight patients (mean age, 65 years) underwent bilateral TKA using a PCL substituting and a PCL sacrificing prosthesis on each side. At each follow-up, the stability of anteroposterior and mediolateral laxity using stress radiographs, range of motion, quadriceps muscle power recovery using isokinetic dynamometer and radiographs were evaluated. At the 1-year evaluation, we asked, “Which is your better knee overall?” to determine the patients' preferences. Results. The mean varus/valgus laxities were 1.6Ë�/3.9Ë� in the PCL sacrificing side and 2.3Ë�/5.9Ë� in the PCL substituting side, and the mean anterior/posterior laxities were 6.4 mm/14.2 mm and 3.0 mm/7.3 mm at the 1-year follow up, respectively. Isokinetic peak torque at 60°/sec and 180°/sec in extension was 130% and 113% compared to the preoperative value in the PCL sacrificing side and 109% and 110% in the PCL substituting side, respectively. The differences in the posterior laxity and isokinetic peak torque at 60°/sec were significant statistically. Sixty-one percent preferred PCL sacrificing side to PCL substituting side. Conclusion. PCL sacrificing TKA showed more posterior laxity and better quadriceps muscle power at the time of short-term follow-up. Patients with bilateral TKA preferred PCL sacrificing TKA to PCL substituting TKA. Longer follow-up is needed to determine whether there will be an advantage in terms of longer-term function

Lubricin is a proteoglycan that is a boundary lubricant in synovial joints and both a surface and collagen inter-fascicular lubricant in ligaments. The purpose of this study was to characterise the mRNA levels for lubricin in the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL) in aging and surgically-induced menopausal rabbits. We hypothesised that lubricin mRNA levels would be increased in ligaments from aging and menopausal rabbits compared with ligaments from normal rabbits. All four knee ligaments (ACL, PCL, MCL, LCL) were isolated from normal (1-year-old rabbits, n=8), aging (3-year-old rabbits, n=6), and menopausal (1-year-old rabbits fourteen weeks after surgical ovariohysterectomy, n=8) female New Zealand White rabbits. RT-qPCR was used to evaluate the mRNA levels for lubricin normalised to the housekeeping gene 18S. After removing outliers, data for normal, aging, and menopausal rabbits for each knee ligament (ACL, PCL, MCL, LCL) were compared using ANOVA with linear contrasts or Kruskal-Wallis test with Conover post-hoc analysis. For ACLs, the mRNA levels for lubricin were increased in menopausal and aging rabbits compared with normal rabbits (p<0.056). For PCLs, trends for increased lubricin mRNA levels were found when comparing menopausal and aging rabbits with normal rabbits (p<0.092). For MCLs, the mRNA levels for lubricin were increased in menopausal and aging rabbits compared with normal rabbits (p<0.050). For LCLs, no differences in lubricin mRNA levels were detected comparing the three groups. For all four knee ligaments (ACL, PCL, MCL, LCL), no differences in lubricin mRNA levels were detected comparing the ligaments from menopausal rabbits with those from aging rabbits. Lubricin plays a role in collagen fascicle lubrication in ligaments (1,2). Increased lubricin gene expression was associated with mechanical changes (including decreased modulus and increased failure strain) in the aging rabbit MCL (3). Detection of similar molecular changes in the ACL, and possibly the PCL, may indicate that their mechanical properties may also change as a result of increased lubricin gene expression, thereby potentially pre-disposing these ligaments to damage accumulation. Compared to aging ligaments, aging tendons exhibited decreased lubricin gene and protein expression, and increased stiffness (4). Although opposite changes than aging ligaments, these findings support the relationship between lubricin and modulus/stiffness. The similarities between ligaments in the aging and menopausal groups may suggest that surgically-induced menopause results in a form of accelerated aging in the rabbit ACL, MCL and possibly PCL

The posterior tibial slope angle (PTS) in posterior cruciate retaining total knee arthroplasty influences the knee kinematics, knee stability, flexion gap, knee range of motion (ROM) and the tension of the posterior cruciate ligament (PCL). The current technique of using an arbitrary (often 3–5 degrees) PTS in all cases seldom will restore native slope in cruciate retaining TKA. Questions/Purposes: The primary objective was to determine if we could surgically reproduce the native PTS in cruciate-retaining total knee arthroplasty. The second objective was to determine if reproduction of native slope was significant – ie influenced clinical outcome. We evaluated the radiographic and clinical outcomes of a series of consecutive total knee arthroplasties using the PFC sigma cruciate-retaining total knee system in 215 knees. The tibial bone cut was planned to be parallel to the patient's native anatomical slope in the sagittal plane. An “Angel Wing” instrument was placed on the lateral tibial plateau and the slope of the cutting guide adjusted to make the cutting block parallel to the patient's native tibial slope. All true lateral radiographs of the knee were measured for PTS using a picture achieving and communication system (PACS). PTSs were measured with reference to the proximal tibial medullary canal (PTS-M) and the proximal tibial anterior cortex (PTS-C). The knee ROM, Knee Society Score, Western Ontario and McMaster University Osteoarthritis Index (WOMAC) and SF-12 at the last follow-up were evaluated as clinical outcomes. The mean preoperative PTS-M was 6.9±3.3 degrees and the mean postoperative PTS-M was 7±2.4 degrees. The mean preoperative PTS-C was 12.2±4.2 degrees and the mean postoperative PTS-M was 12.6±3.4 degrees. There was no significant difference form the preoperative and postoperative PTS measurement in both techniques (p>0.05). We used an arbitrary 3 degrees as an acceptable range for PTS-M reproduction. The PTS-M was reproduced within 3 degrees in 144 knees (67%); designated as Group A. The 71 knees with a difference more than 3 degrees in (33%) were designated as Group B. Group A showed significantly larger gain in ROM compared with group B (p=0.04). Group A also had significantly better improvement in Knee society score and WOMAC score and SF-12 physical score when compare with group B (p<0.01). Our modification of standard surgical technique reliably reproduced the native tibial slope in cruciate-retaining total knee arthroplasty. More importantly, reproduction of the patient's native PTS within 3 degrees resulted in better clinical outcomes manifested by gain in ROM and knee functional outcome scores

Introduction. Measuring the step off during total knee replacement (TKR) is a newly developed operative strategy (“spacer technique”; Heesterbeek et al, KSSTA 2014;22(3):650–9) to determine the optimal contact point (CP) of the femur with the tibia postoperative and to balance the posterior cruciate ligament (PCL) in cruciate-retaining TKR. Engineers have calculated the ideal step off for every size of the TKR, for which the tibiofemoral contact point in 90° will be at the designed position. With this study we determined the postoperative CP in CR-TKA and investigated whether (adverse) clinical outcome was correlated with the CP. Methods. 23 patients presenting with non-inflammatory osteoarthritis, a good functioning PCL, and indication for surgery with a PCL-retaining TKR were selected. Intraoperative PCL balancing was performed with the spacer technique. At 3 months postoperative, a pair of mediolateral radiographs was made using a set-up used for radiostereometric analysis (RSA). The patient was positioned standing with the operated leg in 90 degrees, 50% weight-bearing, knee flexion on a 30 cm-step. Model-based RSA software (RSAcore) was used to determine the 3D positions of the femur and tibia component, that were exported to custom-written software for determining the CP. The CP was defined as the point with the smallest distance between both the medial and lateral femur condyles and tibia plateau. It is expressed as the ratio of the anterior-posterior CP distance and the maximum anterior-posterior tibia plateau size, with 0 being anterior, 1 being posterior. Patients with reduced flexion capacity at follow-up, leading to manipulation under anaesthesia and/or scopic releases, were categorized as COMP, the other patients as no-COMP. CP was compared between these groups. Results. Preliminary data show that the mean medial CP of the total group was 0.51 (sd 0.05), mean lateral CP was 0.61 (sd 0.03) (p<0.001). Six out of 23 patients had flexion-related complications and for this reason further patient inclusion was stopped. The medial CP of the COMP-group (n=6) was at 0.54 (sd 0.01), which was significantly more posterior than the medial CP of the no-COMP group (n=17) (0.50 (sd 0.05)) (p=0.004). (Figure 1) The lateral CP was similar for both groups (p=0.76). Discussion. The medial CP relates to clinical outcome; patients with reduced flexion capacity had a more posterior CP. This might be an indication for a too tightly balanced PCL, but we need to investigate this further. None of the patients had a medial CP at the theoretically optimal position

OBJECTIVE. The purpose of this study was to investigate the postoperative change of hematological values between post cam type posterior stabilized (PS) and deep dish cruciate substituting (CS) type total knee arthroplasty (TKA). MATERIALS AND METHODS. From June 1999 to December 2013, 322 patients with TKA due to osteoarthritis or rheumatoid arthritis were enrolled. In all knees, posterior cruciate ligament (PCL) were resected, and either Scorpio NRG PS knee (Stryker Orthopaedics) or Triathlon CS knee (Stryker Orthopaedics) were implanted. The PS group included 183 patients (183 knees) consisting of 4 men (4 knees) and 179 women (179 knees) with a mean age of 68.5 years (range 31 – 86 years). And the CS group included 139 patients (139 knees) consisting of 27 men (27 knees) and 112 women (112 knees) with a mean age of 75 years (range 42 – 98 years). Simultaneous bilateral TKA were excluded in this study. No case had blood transfusion in perioperative period. The changes of hemoglobin (Hb), d-dimer (DD) and c-reactive protein (CRP) were compared at pre-operative value, 1, 4, 7 and 14 days after surgery in two groups. RESULT. In both groups, Hb was lowest at 4 days after surgery. CRP was highest at 4 days after surgery, and DD bimodal change high in one day and 14 days after surgery. In comparison with PS group and CS group. The values of Hb were significantly lower in PS group at 1, 4, and 7 days after surgery. The values of CRP changes were significantly higher in PS group than CS group at 1, 4, 7 days after surgery. And the values of DD were not significantly different in two groups. CONCLUSION. In this study, PCL were resecte in all knee. The difference of surgical procedure in PS knee and CS knee was bone resection of femoral intercondylar notch. In PS knee, for the space of post cam mechanism, we had to remove some amount of the bone from the notch. In contrast, we did not have to remove the bone in CS knee. The difference of the procedure could be the causes of lower amount of bleeding and less surgical invasiveness presented by CRP changes in CS knee

Introduction. Compared with the cruciate-retaining (CR) insert for total knee arthroplasty (TKA), the cruciate-substituting (CS) insert has a raised anterior lip, providing greater anterior constraint, and thus, can be used in cases of posterior cruciate ligament (PCL) sacrifice. However, studies have shown that the PCL maintains femoral rollback during flexion, acts as a stabilizer against distal traction force and aids knee joint proprioception; therefore, the argument for PCL excision in CS TKA remains controversial. The purpose of this study was to analyze CS TKA kinematics and identify the role of the PCL. Methods. Seven fresh-frozen lower-extremity cadaver specimens were analyzed using Orthomap. ®. Precision Knee Navigation software (Stryker Orthopaedics, Mahwah, NJ, USA). They were surgically implanted with Triathlon. ®. components (Stryker Orthopaedics). The CS insert has a raised anterior lip, and the posterior geometry shares the same profile as the CR, so we can choose retaining or sacrificing the PCL. Six patterns were analyzed: (1) natural knee; (2) only anterior cruciate ligament excision; (3) CS TKA, PCL retention, and bony island preservation; (4) CS TKA, PCL retention, and bony island resection; (5) CS TKA and PCL excision; and (6) CR TKA and PCL excision. Center of the knee and center of the proximal tibia were registered using navigation system, and the magnitudes of the condylar translation were evaluated. And then, using trigonometric function, the magnitude of anterior-posterior translation of the femur was calculated. Results. PCL excision patterns showed that the magnitude of anterior-posterior (AP) translation was higher in mid-flexion and lower in deep flexion than in other patterns (Fig. 1). Comparing two PCL excision patterns, in CS insert, the anterior translation magnitude was a little lower in extension and 30° flexion. Comparing two PCL retention patterns, the both posterior translation magnitudes in deep flexion were comparable to that of the natural knee. Discussion. Very few studies have reported about comparison of PCL retention with PCL excision in CS TKA. Omori et al. evaluated the medial pivot type TKA, and found that the design showed no femoral rollback under the PCL-sacrificing condition. In our study, increased anterior translation magnitudes in mid-flexion indicated paradoxical roll-forward, and decreased posterior translation magnitudes in deep flexion indicated decreased rollback. In other words, PCL excision in CS TKA caused mid-flexion instability and decreased the femoral rollback, so raised anterior lip was not likely to contribute to TKA kinematics. Another research is necessary to evaluate the effects of the raised anterior lip. On the other hand, PCL retention in CS TKA maintained physiological femoral rollback. The AP translation magnitude was not dependents on the bony island. Conclusions. We had better retain the PCL in raised anterior lip type CS TKA to ensure physiological knee kinematics. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Background. Total knee arthroplasty (TKA) is the highly developed procedure for sever osteoarthritic knee, in which there are two major concepts; Cruciate Retaining design (CR) and Posterior Stabilized design (PS). The femoral roll back movement is enforced with the post-cam mechanism in the PS, however, this structure associates with the complications, i.e. wear and dislocation. The CR has been developed to obtain the knee stability with native posterior cruciate ligament (PCL) in TKA. However, the preservation of the PCL can limit knee exposure and increase the technical challenge of surgery. We hypothesized that the knee exposure was easily achieved after the PCL was released, however, the PCL was repaired and the posterior stability was re-established after the TKA with time if it was released subperiostealy. Objective. The objective of this study was to evaluate the varying of the posterior stability after the PCL-released CR TKA. Methods. Patients were performed the CR TKA with 3DKnee (DJO Global, Vista, CA), in which the entire PCL was subperiostealy released at its femoral insertion (Fig. 1). Following that, the patients were examined with the Knee Society Score and the KT-2000 knee ligament arthrometer (MedMetric Corp., San Diego, CA) firstly between 3 weeks and 7 weeks and secondly between 12 weeks and 20 weeks postoperatively. Results. There were 8 cases in 2 female and 6 male knees, and the age was 63.3 ± 11.1 (ranging from 51 to 79). Once the PCL was released, the tibia was easy to subluxate, and the knee was clearly exposed intraoperatively. The Knee Society knee score at the first evaluation was 74.4 ± 10.7 (59 to 90), which was significantly improved compared to the preoperative score of 37.0 ± 9.4 (25 to 50) (p<0.001). Then, the score increased up to 89.4 ± 11.6 (70 to 100) at the second evaluation. The function score was 35.6 ± 19.9 (5 to 55) preoperatively and decreased to 24.4 ± 12.2 (20 to 55) at the first evaluation. After that, it increased to 82.5 ± 14.1 (65 to 100) (p<0.001) at the second evaluation. The anteroposterior laxity was 5.2 ± 1.9 (3 to 7.5) mm at the first evaluation, and was improved to 3.6 ± 1.2 (2 to 5) mm (p<0.046). Therefore, the posterior stability was confirmed to be re-established. We also confirmed the re-establishment of the PCL integrity at a revision TKA, in which the original procedure had been performed 7 years ago (Fig. 2). Conclusion. The re-establishment of the posterior stability after the PCL-released CR TKA was demonstrated. This procedure to release the entire PCL subperiostealy is recommended as a means of facilitating CR 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).