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

Variations in the pivot shift test have been proposed by many authors, though, a test comprised of rotatory and valgus tibial forces with accompanied knee range of motion is frequently utilised. Differences in applied forces between practitioners and patient guarding have been observed as potentially decreasing the reproducibility and reliability of the pivot shift test. We hypothesise that a low-profile pivot shift test (LPPST) consisting of practitioner induced internal rotatory and anterior directed tibial forces with accompanied knee range of motion can elicit significant differences in internal tibial rotation and anterior tibial translation between the anterior cruciate ligament (ACL) deficient and ACL sufficient knee. Fresh, frozen cadaver knees were used for this study. Four practitioners performed the LPPST on each ACL sufficient knee. The ACL of each knee was subsequently resected and each practitioner performed the LPPST on each ACL deficient knee. Our quantitative assessment utilised computer assisted navigation to sample (10Hz) the anterior translation and internal rotation of the tibia as the LPPST force vectors were applied. We subsequently pooled and averaged data from all four practitioners and analysed the entrance pivot (tibial reduction with knee range of motion from extension into flexion) and the exit pivot (tibial subluxation with knee range of motion from flexion into extension). We observed a significant difference in anterior tibial translation and internal tibial rotation in the ACL deficient vs. ACL sufficient knees during both the entrance and exit pivot phases of the LPPST. The entrance pivot (n=140) was found to have an average maximum anterior tibial translation of 7.83 mm in the ACL deficient knee specimens compared to 1.23 mm in the ACL sufficient knee specimens (p<0.01). We found the ACL deficient knees to exhibit an average maximum internal tibial rotation of 12.38 degrees compared to 11.24 degrees in the ACL sufficient specimens during the entrance pivot (p=0.04). The exit pivot (n=120) was found to have an average maximum anterior tibial translation of 7.82 mm in the ACL deficient knee specimens compared to 1.44 mm in the ACL sufficient knee specimens (p<0.01). The ACL deficient knees exhibited an average maximum internal tibial rotation of 12.44 degrees compared to 11.13 degrees in the ACL sufficient knee specimens during the exit pivot (p=0.02). Our results introduce a physical exam maneuver (LPPST) consisting of practitioner induced internal rotatory and anterior directed forces, with notable absence of valgus force, on the tibia while applying knee range of motion. Our results demonstrate that the LPPST can elicit significant anterior translation and internal rotary differences in an effort to differentiate between the ACL deficient and ACL sufficient knee. Our work will next seek to explore the clinical reproducibility of this physical exam maneuver

INTRODUCTION. Multiple video fluoroscopic analyses have been performed to determine the in vivo kinematic patterns of total knee arthroplasty (TKA) and non implanted knees. Unfortunately, many of these studies were not correlated with bearing surface forces and possible failure modes that could be detected with a sound sensor. Therefore, the objective of the present study was to conduct a comparative analysis of the kinematic data derived for all subjects having a TKA who were analyzed over the past seventeen years at our laboratory and to determine how these patterns correlate with bearing surface forces and joint sound. METHODS. Initially, femorotibial contact positions and axial rotation magnitudes were derived for subjects having either a non implanted or implanted knee. Non implanted knees consisted of normal and anterior cruciate ligament (ACL) deficient knees (ACLD). Implanted knees consisted of posterior stabilized (PS) fixed (PSF) and mobile (PSM) bearing, posterior cruciate ligament retaining (PCR) fixed (PCRF) and mobile (PCRM) bearing, posterior cruciate sacrificing mobile (PCSM) bearing and ACL retaining fixed (ACRF) bearing TKA. Each subject, while under fluoroscopic surveillance, performed a weight-bearing deep knee bend and/or normal gait. Using a three-dimensional (3D) model fitting approach, the relative pose of knee implant components were determined in 3D from a single-perspective fluoroscopic image by manipulating a CAD model in three-dimensional space. Anterior/posterior (A/P) contact positions for both the medial and lateral condyles and axial rotation of the femoral component relative to the tibial component were assessed. Then, a subset of these subjects were further analyzed to determine their in vivo bearing surface forces and joint sound using a more recently derived protocol for analyzing audible signals. RESULTS. During gait, subjects having a ACRF TKA experienced the most normal-like kinematic patterns, where the femoral condyles were more anterior than other TKA designs. Subjects having a PCSM TKA experienced the least amount of femoral head sliding during gait, whereas the medial and lateral condyles remained near the midline of the tibia in the sagittal plane. Subjects having a mobile bearing TKA did seem to experience axial rotation during this activity. Subjects having a normal knee experienced posterior motion of the lateral condyle from full extension to maximum knee flexion (maximum = 27 mm), while their medial condyle experienced less motion (maximum 12 mm). Similar to the subjects with a normal knee, all subjects having an ACRF TKA experienced posterior motion of their lateral condyle, albeit less than the normal knee, and less medial condyle motion. Subjects having a PCRF or PCRM TKA experienced highly variable kinematic patterns. Many of these subjects experienced an anterior sliding motion with increasing knee flexion. Subjects having either a PSF or PSM TKA experienced a higher incidence and magnitude of posterior condylar motion, but less in magnitude when compared with the normal knee. Not all PS TKA knees produced similar results and some experienced poor weight-bearing range-of-motion and more erratic kinematic patterns. Subjects having a PCSM TKA experienced a contact position that remained centralized during the deep knee bend activity, often leading to posterior impingement and less weight-bearing range-of-motion. Subjects having a mobile bearing TKA experienced greater contact area and less contact stress than subjects having a fixed bearing TKA and subjects having a high flexion TKA experienced less contact stress in deep flexion than subjects having a more traditional-type TKA design. The sound sensor revealed various sounds related to cam/post mechanism engagement, condylar lift-off, patellofemoral interaction and other sounds that at present, having not yet been correlated to identifiable mechanics parameters. DISCUSSION. The magnitudes of posterior femoral rollback during deep flexion in all TKA designs tested were less than in the normal knee. This may explain, at least in part, why knee flexion following TKA is reduced when compared to the normal knee. During gait, PSF and PSM TKA designs experienced similar kinematic patterns as those designs that lacked a cam and post mechanism. Subjects having a TKA experienced significantly less axial rotation when compared to the normal knee (p<0.001). Reversing axial rotation patterns where of high incidence in subjects having a TKA. Additionally, it is clear that surgeon variability can play a significant role in eventual knee mechanics patterns. Bearing surface mechanics related to contact force, area and stress varied considerably between subjects and TKA designs. Bearing surface sounds may play a significant role in the future when attempting to assess failure modes as various sounds were detected for subjects having a TKA design