Effect of single-radius design on in vivo kinematics during stair activities after total knee arthroplasty.

BACKGROUND: The single-radius design is one of the major total knee arthroplasty (TKA) designs and widely used all over the world. The objective of this study was to compare in vivo kinematics between the anteroposterior (AP) single-radius design with mediolateral (ML) single-radius (Non Restricted Geometry; NRG) and ML dual-radius (Triathlon) during stair activities. METHODS: A total of 21 knees in 18 patients (NRG group: 10 knees in 7 patients, Triathlon group: 11 knees in 11 patients) with a clinically successful posterior stabilized TKA were examined. Under fluoroscopic surveillance, each patient performed stair ascending and descending motions. In vivo kinematics were analyzed using 2D/3D registration technique. The knee flexion angle, rotation angle, varus-valgus angle, AP translation of the femorotibial contact point for both the medial and lateral sides of the knee, and post-cam engagement were evaluated. RESULTS: There were no significant differences between the two groups in rotation angle and AP translation at each flexion angle. Examining the varus-valgus angle, the NRG group showed varus position at an early flexion angle during both stair activities.Post-cam engagement was observed in both groups during both stair activities. The mean flexion angle of engagement in the NRG group, the post of which was located anterior to the Triathlon, was larger than that in the Triathlon group during both stair activities. CONCLUSION: Despite the same AP single-radius TKA, ML single-radius might affect varus motion at an early flexion angle.

In Vivo Kinematics and Cruciate Ligament Tension Are Not Restored to Normal After Bicruciate-Preserving Arthroplasty.

BACKGROUND: Whether cruciate ligament forces in cruciate-preserving designs, such as unicompartmental knee arthroplasty (UKA) or bi-cruciate-retaining total knee arthroplasty (BCR-TKA), differ from those in normal knees remains unknown. The purpose of this study was to compare the in vivo kinematics and cruciate ligament force in knees before and after UKA or BCR-TKA to those in normal knees during high-flexion activity. METHODS: Overall, twenty normal knees, 17 knees with medial UKA, and 15 knees with BCR-TKA were fluoroscopically examined while performing a squatting activity. A 2-dimensional or 3-dimensional registration technique was employed to measure tibio-femoral kinematics. Ligament strains and tensions in the anteromedial bundle of the anterior cruciate ligament and posterolateral bundle of the anterior cruciate ligament and the anterolateral bundle of the posterior cruciate ligament (aPCL) and posteromedial bundle of the posterior cruciate ligament (pPCL) during knee flexion were analyzed. RESULTS: Tension in both bundles of the anterior cruciate ligament decreased with flexion. At 60° of flexion, anteromedial bundle of the anterior cruciate ligament tension in postoperative UKA knees was greater than that in normal knees. At 30° of flexion, posterolateral bundle of the anterior cruciate ligament tension in postoperative UKA knees was greater than that in normal knees. On the other hand, aPCL and pPCL tensions increased with flexion. From 40 to 110° of flexion, the postoperative aPCL tension in UKA knees was greater than that in normal knees. At 110° of flexion, the preoperative pPCL tension in UKA knees was greater than that in normal knees. In addition, the postoperative pPCL tension in UKA knees was larger than that in normal knees beyond 20° of flexion. Furthermore, the pPCL tension of postoperative BCR-TKA knees was larger than that in normal knees from 20 to 50° and beyond 90° of flexion. CONCLUSIONS: The cruciate ligament tensions, especially posterior cruciate ligament tension in knees after UKA, were greater than those in the normal knees. Surgeons performing bi-cruciat-preserving knee arthroplasties should therefore balance cruciate ligament tension more carefully in flexion and extension.

In vivo three-dimensional kinematic comparison of normal knees between flexion and extension activities.

Background/Objective: Normal knee kinematics during flexion and extension activities over the whole range of motion remains unknown. This study aimed to clarify in vivo kinematics during knee flexion and extension activities of normal knees by comparing continuous flexion and extension activities up to a high flexion angle. Methods: Twenty knees of 10 Japanese volunteers were enrolled in this study. Each volunteer performed a continuous squatting motion under fluoroscopy, and a two- or three-dimensional registration technique was used. Rotation and anteroposterior translation of the medial and lateral sides of the femur relative to the tibia at each flexion angle were evaluated. Results: Femoral external rotation was significantly smaller from 10° to 40° flexion during extension activities than during flexion activities. However, the femoral external rotation was larger from 120° to 130° flexion during extension activities than during flexion activities. From 10° to 60° of flexion, the medial side was significantly more posteriorly located during extension activities than during flexion activities. Furthermore, the lateral side was significantly more posteriorly located at 130° of flexion during extension activities than during flexion activities. Conclusion: In vivo kinematics of normal knees during extension activities differ from those during flexion activities in early and high flexion.

In Vivo Kinematic Analysis of Mobile-Bearing Unicompartmental Knee Arthroplasty during High Flexion Activities.

Mobile-bearing (MB) unicompartmental knee arthroplasty (UKA) has high conformity between the femoral articular surface and the meniscal bearing; therefore, the surface and subsurface contact stress is reduced. Additionally, the survival rate is high. However, the in vivo kinematics of MB UKA knees during high-flexion activities of daily living remain unknown. The aim of this study was to investigate in vivo the three-dimensional kinematics of MB UKA knees during high-flexion activities of daily living. A total of 17 knees of 17 patients who could achieve kneeling after MB UKA were examined. Under fluoroscopy, each patient performed squatting and kneeling motions. To estimate the spatial position and orientation of the knee, a two-dimensional/three-dimensional registration technique was used. We evaluated the femoral rotation and varus-valgus angle relative to the tibia and the anteroposterior translation of the medial sulcus (medial side) and lateral epicondyle (lateral side) of the femur on the plane perpendicular to the tibial mechanical axis in each flexion angle. From 130° to 140° of flexion, the femoral external rotation during squatting was significantly smaller than that during kneeling. Additionally, the medial side of the femur during squatting was significantly more posteriorly located compared with that during kneeling. There was no significant difference between squatting and kneeling in terms of the lateral side of the femur and the varus-valgus position in each flexion angle. At high flexion angle, the kinematics of MB UKA knees may differ depending on the performance.

Comparison of finite helical axis of the knee joint before and after bi-cruciate-preserving knee arthroplasty.

BACKGROUND: Difference in the finite helical axis of the knee joints before and after anterior cruciate ligament-preserving knee arthroplasties such as unicompartmental knee arthroplasty and bi-cruciate-retaining total knee arthroplasty remains unknown. This study compared the knee finite helical axes before and after bi-cruciate-preserving knee arthroplasty. METHODS: Patients undergoing medial unicompartmental knee arthroplasty and bi-cruciate-retaining total knee arthroplasty were included. Under fluoroscopy, participants performed a deep knee bend before and after surgery. A two/three-dimensional registration technique was employed to measure tibiofemoral kinematics. Femoral finite helical axis was calculated in a flexion range of 0-120° using 30° windows (early-, mid-, late-, and deep-flexion phases). FINDINGS: In unicompartmental knee arthroplasty, the preoperative knee vertical angle was larger than the postoperative vertical angle in mid- and deep-flexion phases. The postoperative knee vertical angle was smaller in unicompartmental knee arthroplasty than in bi-cruciate-retaining total knee arthroplasty. In unicompartmental knee arthroplasty, the preoperative horizontal angle was smaller than the postoperative horizontal angle in the early-flexion phase. However, in bi-cruciate-retaining total knee arthroplasty, the preoperative horizontal angle was larger than the postoperative horizontal angle in mid- and deep-flexion phases. The horizontal angle was smaller before unicompartmental knee arthroplasty than that before bi-cruciate-retaining total knee arthroplasty in early-, mid-, and deep-flexion phases. However, the vertical angle was larger after unicompartmental knee arthroplasty than that after bi-cruciate-retaining total knee arthroplasty in the early-flexion phase. INTERPRETATION: The knee finite helical axes before and after unicompartmental knee arthroplasty differed from those before and after bi-cruciate-retaining total knee arthroplasty.

Bicruciate-retaining total knee arthroplasty procedure reduced tensile force in the middle and posterior components of lateral collateral ligament during deep knee flexion activities with no effect on tensile force of the medial collateral ligament.

PURPOSE: To analyse the effects of bicruciate-retaining total knee arthroplasty (BCR-TKA) on the tensile force of the collateral ligaments during two deep knee flexion activities, cross-leg sitting and squatting. METHODS: Thirteen patients (15 knees) treated using bicruciate-retaining total knee arthroplasty (BCR-TKA) for knee joint osteoarthritis were analysed. Knee joint kinematics during cross-leg sitting (open-chain flexion) and squatting (closed-chain flexion) were evaluated through fluoroscopy. The tensile force was calculated in vivo based on the change in the distance between the femoral and tibial attachment areas for the anterior, middle, and posterior components of the superficial (sMCL) and deep (dMCL) medial collateral ligament and the lateral collateral ligament (LCL). Differences in the calculated tensile forces of the collateral ligaments were evaluated using repeated measures of analysis of variance, with post hoc pairwise comparison (Bonferroni test). Statistical significance was set at P ≤ 0.05. RESULTS: The correction of the coronal alignment was related to the surgical technique, not to the implant design. No significant change in the tensile force in all three components of the sMCL from pre- to post-TKA (n.s.) was observed. For dMCL, a pre- to post-TKA change in the tensile force was observed only for the anterior dMCL component (p = 0.03). No change was observed in the tensile force of the anterior LCL with increasing flexion, with no difference in pre- to post-TKA and between activities (n.s.). In contrast, tensile force in the middle LCL slightly decreased with increasing flexion during squatting, pre- and post-TKA. After surgery, lower forces were generated at 40° of flexion (p = 0.04). Tensile force in the posterior LCL was higher in extension than flexion, which remained high in the extension post-TKA. However, after surgery, lower tensile forces were generated at 10° (p = 0.04) and 40° (p = 0.04) of flexion. CONCLUSIONS: The in vivo change in tensile forces of the collateral ligaments of the knee before and after BCR-TKA can inform the development of appropriate ligament balancing strategies to facilitate recovery of deep knee flexion activities after TKA, as well as for continued improvement of BCR-TKA designs. LEVEL OF EVIDENCE: III.

Mechanistic insights into glenohumeral kinematics derived from positional relationship between the contact path and humeral tuberosity.

Although three-dimensional (3D) glenohumeral (GH) motion has generally been expressed only by rotational elements, its mechanistic details, including GH rotations, remain unknown owing to a lack of geometric investigations. This study aims to investigate the positional relationship between the contact path and humeral tuberosities at the GH joint during arm elevation and to consider the mechanism of GH kinematics. Shoulder kinematics were captured using two-dimensional and 3D single-plane image registration techniques in 15 young healthy subjects during flexion, scaption, and abduction. The glenoid movement relative to the humeral head was calculated to describe the contact path on the humeral head. From the start to 45° of flexion, scaption, and abduction, the glenoid center moved from the anteromedial to the anterior, central, and posterior portions of the humeral head, respectively, as the GH joint rotated externally. From 45° to the maximal elevation for all elevation planes, the glenoid center moved upward to the humeral head and came close to the bicipital groove (BG) at maximal elevation, while the glenoid maintained a constant inclination at 20°-40° relative to the humerus. To investigate this mechanism, the position of humeral tuberosities relative to the glenoid was calculated, and the BG was found to face the supraglenoid tubercle, the attachment site of the long head of biceps (LHB). GH external rotation mainly occurred depending on the elevation planes in the early phase of elevation, and it might be kept constant by the LHB and rotator cuff in the mid- to end range of elevation.

Anterior cruciate ligament-deficient knee induces a posterior location of the femur in the medial compartment during squatting.

Although an anterior cruciate ligament (ACL) deficiency induces knee osteoarthritis, particularly in the medial compartment, the kinematics remains partially unclear. This study investigated the in vivo knee kinematics of ACL-deficient and normal knees by comparing them during squatting. This prospective comparative study included 17 ACL-deficient knees and 20 normal knees. The kinematics was investigated under fluoroscopy using a two- to three-dimensional registration technique. The anteroposterior (AP) translation of the medial and lateral sides of the femur, axial rotation of the femur relative to the tibia, and kinematic pathways were evaluated and compared. At first, the medial AP position of the femur translated anteriorly from 0° to midflexion, afterward it translated posteriorly in both ACL-deficient and normal knees. However, the medial AP position of the femur in the ACL-deficient knees was located significantly posteriorly compared with normal knees at 0-110° flexion. The lateral AP position of the femur translated posteriorly from 0° to 150° flexion in both ACL-deficient and normal knees. The lateral AP position of the femur in the ACL-deficient knees was located significantly posteriorly compared with that in normal knees at 0-10° flexion. The femur showed external rotation from 0° to 150° flexion in both ACL-deficient and normal knees. A medial pivot motion and subsequent bicondylar rollback were observed in both knees in the kinematic pathway. In conclusion, the AP position of the femur relative to the tibia was altered due to ACL deficiency, particularly in the medial compartment.

The influence of three-dimensional scapular kinematics on arm elevation angle in healthy subjects.

BACKGROUND: We often clinically observe individual differences in arm elevation angles, but the motion producing these differences remains unclear, partly because of the difficulty of accurately measuring scapular motion. The aim of this study was to determine whether the scapular or glenohumeral (GH) motion has more influence on differences in the arm elevation angles by capturing not only the humerus and scapula but also the trunk using two- (2D) and three-dimensional (3D) shape-matching registration techniques. METHODS: Fifteen healthy subjects (13 male and 2 female; mean age: 27.7 years) were instructed to elevate their arms in the sagittal, scapular, and coronal planes. They were divided into high and low groups based on the average of arm elevation angle measured by a goniometer. The 3D scapular, thoracohumeral, and glenohumeral motions were evaluated using 2D/3D single-plane registration. To compare 3D motions between groups, we performed a two-way repeated measures analysis of variance. RESULTS: Eight subjects were assigned to the high group, while seven subjects were assigned to the low groups based on an average elevation angle of 172°. The low group demonstrated a significant larger scapular protraction during elevation in all planes (P = 0.0002 for flexion; P = 0.0047 for scaption; P = 0.0314 for abduction), and smaller posterior tilting only during flexion (P = 0.0157). No significant differences occurred in scapular upward rotations or the glenohumeral positions and rotations. CONCLUSIONS: This study revealed that insufficient scapular retraction and posterior tilting results in lower arm elevation angles, suggesting that improving the flexibility and activation of muscles surrounding the scapula may be important to achieve complete arm elevation.

In vivo kinematic comparison of medial pivot total knee arthroplasty in weight-bearing and non-weight-bearing deep knee bending.

BACKGROUND: This study aimed to determine the kinematics of medial pivot total knee arthroplasty by comparing weight-bearing and non-weight-bearing deep knee bending and to evaluate the effect of the weight-bearing state on the kinematics. METHODS: The kinematics of 19 knees were investigated under fluoroscopy during squatting (weight-bearing) and active-assisted knee bending (non-weight-bearing) using two- to three-dimensional registration technique. Accordingly, range of motion, anteroposterior translation for the medial and lateral low contact points, axial rotation of the femoral component relative to the tibial component and kinematic pathway were evaluated. FINDINGS: There was no difference in range of motion between the two states. The medial anteroposterior translation showed no significant movement with no anterior translation in both the weight-bearing and non-weight-bearing from 0° to 90° of flexion. Regarding the lateral anteroposterior translation, a posterior translation was observed during weight-bearing, whereas a slight anterior translation from 0° to 30° of flexion and subsequent posterior translation were found in the non-weight-bearing. Femoral external rotation was observed in the weight-bearing, whereas femoral internal rotation was seen from 0° to 30° of flexion and subsequent femoral external rotation was observed in the non-weight-bearing. The kinematic pathway showed medial pivot motion and subsequent bicondylar rollback in the weight-bearing, whereas only medial pivot motion was observed in the non-weight-bearing. INTERPRETATION: The medial anteroposterior translation of the femur during deep knee bending showed no anterior motion in the two states. The lateral anteroposterior translation and femoral rotation were different in the mid-flexion range between the two states.

Femoral rollback at high-flexion during squatting is related to the improvement of sports activities after bicruciate-stabilized total knee arthroplasty: an observational study.

BACKGROUND: In bicruciate-stabilized total knee arthroplasty (BCS-TKA), the relationship between the postoperative kinematics and sports subscales in patient-reported outcome measures (PROMs) remains unknown. The purpose of this study was to determine the relationship between kinematics and sports subscales using the PROMs after BCS-TKA. METHODS: Sixty-one patients with severe knee osteoarthritis were examined at 13.5 ± 7.8 months after BCS-TKA. The patients performed squats under single fluoroscopic surveillance in the sagittal plane. Range of motion of the knee, axial rotation of the femur relative to the tibial component, and anteroposterior (AP) translation of the medial and lateral femorotibial contact points were measured using a 2D-to-3D registration technique. In addition, the relationship between the kinematics and improvement of the sports subscales in the Knee Injury and Osteoarthritis Outcome Score (KOOS) was evaluated. RESULTS: In rotation angle, the femoral external rotation was observed from 0 to 50° of flexion. The amount of femoral external rotation did not correlate with PROMs-SP. In medial AP translation, posterior translation was observed from 0 to 20° and 80-110° of flexion. Mild anterior translation was observed from 20 to 80° of flexion. Beyond 80° of flexion, posterior translation was positively correlated with squatting. In lateral AP translation, posterior translation was observed from 0 to 20° and 80-110° of flexion. Beyond 80° of flexion, posterior translation was positively correlated with running, jumping, twisting/pivoting, and kneeling. CONCLUSION: Femoral rollback at high flexion during squatting may be important to improve sports performance after BCS-TKA.

In Vivo three-dimensional kinematics of normal knees during sitting sideways on the floor.

BACKGROUND: The normal knee kinematics during asymmetrical kneeling such as the sitting sideways remains unknown. This study aimed to clarify in vivo kinematics during sitting sideways of normal knees. METHODS: Twelve knees from six volunteers were examined. Under fluoroscopy, each volunteer performed a sitting sideways. A two-dimensional/three-dimensional registration technique was used. The rotation angle, varus-valgus angle, anteroposterior translation of the medial and lateral sides of the femur relative to the tibia, and kinematic pathway in each flexion angle was evaluated. RESULTS: Bilateral knees during sitting sideways showed a femoral external rotation relative to the tibia with flexion (ipsilateral: 13.7 ± 3.5°, contralateral: 5.8 ± 6.8°). Whereas the ipsilateral knees showed valgus movement of 4.6 ± 2.5° from 130° to 150° of flexion, and the contralateral knees showed varus movement of -3.1 ± 4.4° from 110° to 150° of flexion. The medial side of the contralateral knees was more posteriorly located than that of the ipsilateral knees beyond 110° of flexion. The lateral side of the contralateral knees was more anteriorly located than that of the ipsilateral knees from 120° to 150° of flexion. In the ipsilateral knees, a medial pivot pattern followed by a bicondylar rollback was observed. In the contralateral knees, no significant movement followed by a bicondylar rollback was observed. CONCLUSION: Even though the asymmetrical kneeling such as sitting sideways, the knees did not display asymmetrical movement.

Effect of weight-bearing in bicruciate-retaining total knee arthroplasty during high-flexion activities.

BACKGROUND: To evaluate the effect of weight-bearing on the kinematics of the bicruciate-retaining total knee arthroplasty design during high knee flexion activities. METHODS: The kinematics of 21 bicruciate-retaining total knee arthroplasties were evaluated under fluoroscopy, with two- and three-dimensional image registrations, during squatting (weight-bearing) and active-assisted knee flexion (non-weight-bearing). The following variables were measured: knee range of motion, axis of femoral rotation and varus-valgus angle relative to the tibial component, anteroposterior translation of the medial and lateral contact points, and the kinematic pathway of the joint surfaces. FINDINGS: From 20° to 100° of flexion, the femoral external rotation during weight-bearing was larger than that during non-weight-bearing. There were no differences in the varus-valgus angles between the two conditions. From 10° to 50° of flexion, the medial contact point during weight-bearing was located posterior to the point of contact during non-weight-bearing; this difference between the two weight-bearing conditions was significant. From 0° to 90° of flexion, the lateral contact point in weight-bearing was located posterior to the contact point in non-weight-bearing; this difference between the two weight-bearing conditions was also significant. INTERPRETATION: The anteroposterior position of the medial and lateral contact points of the bicruciate-retaining total knee arthroplasty design was significantly more posterior in the mid-range of knee flexion in weight-bearing than in non-weight-bearing. However, no anterior translation of the bicruciate-retaining total knee arthroplasty design was observed. Therefore, bicruciate-retaining total knee arthroplasty appears to have good anteroposterior stability throughout the range of knee flexion, regardless of the weight-bearing condition.

Kinematics of bicruciate stabilized and cruciate retaining total knee arthroplasty.

Few studies have been reported about kinematic comparison between bicruciate stabilized and cruciate retaining total knee arthroplasty with the same anatomical surface geometry. The aim of this study was to demonstrate the in vivo kinematics and postoperative patient-reported outcomes of these two surgeries with the same anatomical surface geometry. We analyzed 17 bicruciate stabilized and 18 cruciate retaining total knee arthroplasties using single-plane fluoroscopic surveillance with two- to three-dimensional registration techniques during squatting from minimum to maximum flexion. Flexion angle, femoral external rotation, anteroposterior position of the medial and lateral sides, and postoperative 2011 Knee Society Scores were analyzed. Maximum flexion angles were larger for bicruciate stabilized than for cruciate retaining total knee arthroplasties. There was no significant difference in femoral external rotation between the two types. The medial and lateral femoral condyles in bicruciate stabilized type translated more posteriorly during deeper flexion and at maximum flexion angle, respectively, than those in cruciate retaining total knee arthroplasty. Both groups revealed medial pivots in early flexion, but during deep flexion, bicruciate stabilized total knee arthroplasty revealed bicondylar roll-back and cruciate retaining total knee arthroplasty revealed paradoxical anterior motion. Both groups exhibited similar results in postoperative 2011 Knee Society Scores. Bicruciate stabilized and cruciate retaining total knee arthroplasties with the same anatomical articular surfaces demonstrated different kinematics patterns during squatting. However, there were no significant differences in postoperative 2011 Knee Society Scores between the two types of surgery.

The higher patient-reported outcome measure group had smaller external rotation of the femur in bicruciate-stabilized total knee arthroplasty.

PURPOSE: The hypothesis of this study was that the kinematics of patients with higher patient-reported outcome measures (PROMs) differ from those of patients with lower PROMs after bicruciate-stabilized total knee arthroplasty (BCS-TKA). METHODS: A total of 32 patients with severe knee osteoarthritis were examined 11.2 ± 3.2 months after BCS-TKA. The patients performed squats under single fluoroscopic surveillance in the sagittal plane. To estimate the spatial position and orientation of the femoral and tibial components, a 2D-to-3D registration technique was used. This technique uses a contour-based registration algorithm, single-view fluoroscopic images and 3D computer-aided design models. Knee range of motion, varus-valgus alignment, axial rotation of the femur relative to the tibial component, anteroposterior translation of the medial and lateral femorotibial contact points, kinematic paths, and anterior and posterior post-cam engagement were measured. The patients were divided into two groups using hierarchical cluster analysis based on the 1-year postoperative Knee Injury and Osteoarthritis Outcome Score and 2011 Knee Society Score. RESULTS: The femoral component had significantly more external rotation in the low-score group than in the high-score group (5.1 ± 1.8° vs. 2.2 ± 2.7°, p = 0.02). The high-score group had a medial pivot pattern from 0 to 20° of flexion, without significant movement from 20 to 70°, and final bicondylar rollback beyond 70°. The low-score group had a medial pivot from 0 to 70° of flexion and bicondylar rollback beyond 70°. There were no significant between-group differences in the varus-valgus angle or post-cam engagement. CONCLUSION: The higher PROM group had smaller external rotation of the femur after BCS-TKA. LEVEL OF EVIDENCE: Level III.

The Association between In Vivo Knee Kinematics and Patient-Reported Outcomes during Squatting in Bicruciate-Stabilized Total Knee Arthroplasty.

Bicruciate-stabilized total knee arthroplasty (BCS TKA) has been developed to improve TKA kinematic performance. However, the relationship between in vivo kinematics and patient-reported outcomes (PROs) has not been well described. This study was performed to clarify the relationship between in vivo kinematics and PROs in a cohort of patients undergoing BCS TKA. Forty knees were evaluated using a two-dimensional to three-dimensional registration technique obtained from sagittal plane fluoroscopy. In vivo kinematics including anteroposterior (AP) translation and tibiofemoral rotation were evaluated. Knee Society scores (KSSs) and Knee injury and Osteoarthritis Outcome Scores (KOOSs) were assessed before and after surgery. Relationships between tibiofemoral kinematics assessed with the knee in different positions of knee flexion and PROs were evaluated using Spearman's correlation analysis. The study demonstrated a significant negative correlation (r = - 0.33) between medial AP translation from minimum flexion to 30 degrees flexion and postoperative KOOS activities of daily living subscale. A significant positive correlation (r = 0.51) was found between the femoral external rotation from minimum flexion to 30 degrees flexion and improvement of the KOOS pain subscale. No correlation was found between the lateral AP translation and PROs. Achieving medial AP and femoral external rotation stability in early flexion may be important in optimizing postoperative PROs.

Comparison of in vivo kinematics of total knee arthroplasty between cruciate retaining and cruciate substituting insert.

BACKGROUND: The decision to choose cruciate retaining (CR) insert or cruciate substituting (CS) insert during total knee arthroplasty (TKA) remains a controversial issue. We hypothesized that there are different knee kinematics between CR and CS inserts and that a raised anterior lip design would offer a potential minimization of the paradoxical movement and provide joint stability. The objective of this study was to evaluate and compare kinematics of a CR and CS TKA of the same single-radius design. METHODS: We investigated the in vivo knee kinematics of 20 knees with a CR TKA (10 knees in the CR insert and 10 knees in the CS insert). Patients were examined during deep knee flexion using fluoroscopy and femorotibial motion was determined using a 2- to 3-dimensional registration technique, which used computer-assisted design models to reproduce the spatial positions of the femoral and tibial components. We evaluated the knee range of motion (ROM), femoral axial rotation relative to the tibial component, anteroposterior translation, and kinematic pathway of the nearest point of the medial and lateral femoral condyles on the tibial tray. RESULTS: The average ROM was 121.0 ± 17.3° in CR and 110.8 ± 12.4° in CS. The amount of femoral axial rotation was 7.2 ± 3.9° in CR, and 7.4 ± 2.7° in CS. No significant difference was observed in the amount of anterior translation between CR and CS. The CR and CS inserts had a similar kinematic pattern up to 100° flexion that was central pivot up to 70° flexion and then paradoxical anterior femoral movement until 100° flexion. CONCLUSION: The present study demonstrated that there was no significant difference between the inserts in knee kinematics. These kinematic results suggested that the increased anterior lip could not control anterior movement in the CS insert.

Cruciate ligament force of knees following mobile-bearing unicompartmental knee arthroplasty is larger than the preoperative value.

We analyzed the implantation effects on cruciate ligament force in unicompartmental knee arthroplasty (UKA) and determined whether kinematics is associated with the cruciate ligament force. We examined 16 patients (17 knees) undergoing medial UKA. Under fluoroscopy, each participant performed a deep knee bend before and after UKA. A two-dimensional/three-dimensional registration technique was employed to measure tibiofemoral kinematics. Forces in the anteromedial and posterolateral bundles of both the anterior cruciate ligament (aACL and pACL) and the anterolateral and posteromedial bundles of the posterior cruciate ligament (aPCL and pPCL) during knee flexion were analyzed pre- and post-UKA. Correlations between changes in kinematics and ligament forces post-UKA were also analyzed. Preoperatively, the aACL forces were highly correlated with anteroposterior (AP) translation of the lateral condyles (Correlation coefficient [r] = 0.59). The pPCL forces were highly correlated with the varus-valgus angulation (r = - 0.57). However, postoperatively, the PCL forces in both bundles were highly correlated with the AP translation of the medial femoral condyle (aPCL: r = 0.62, pPCL: r = 0.60). The ACL and PCL forces of the knees post-UKA were larger than those of the knees pre-UKA. Kinematic changes were significantly correlated with the cruciate ligament force changes.

Weight-bearing knee flexion angle better correlates with patient-reported outcome measures than non-weight-bearing condition in total knee arthroplasty: a three-dimensional analysis study.

BACKGROUND: This study aims to elucidate and compare the relationship between the knee flexion angle and patient-reported outcome measures (PROM) in both non-weight-bearing (NWB) and weight-bearing (WB) conditions. METHODS: This retrospective cohort study included 61 knees (47 patients) who underwent total knee arthroplasty. The knee flexion angle was measured by three conditions: NWB in manual goniometer, NWB in fluoroscopic three-dimensional (3D) analysis and WB in the fluoroscopic 3D analysis. The PROM was evaluated by postoperative 2011 Knee Society Score (2011 KSS) and Knee injury and Osteoarthritis Outcome Score (KOOS). Correlations between the knee flexion angle and PROM was analyzed using Spearman's correlation coefficient. Additionally, whether the angular difference between NWB and WB correlated with the PROM or not was evaluated. RESULTS: The NWB knee flexion angle in a goniometer, NWB in 3D analysis, and WB in 3D analysis were 124.6° ± 8.4°, 118.0° ± 10.5°, and 109.5° ± 13.3°, respectively. The angular difference was 8.5° ± 12.8°. No PROM correlation existed in NWB using a goniometer. Moreover, significant positive correlations in 2011 KSS symptoms (r = 0.35) and 2011 KSS functional activities (r = 0.27) were noted in NWB using 3D analysis. Significant positive correlations existed in 2011 KSS symptoms (r = 0.32), 2011 KSS functional activities (r = 0.57), KOOS pain (r = 0.37), KOOS activity of daily living (ADL; r = 0.45), KOOS sports (r = 0.42), and KOOS quality of life (r = 0.36) in WB using 3D analysis. Significant negative correlations were noted in 2011 KSS functional activities (r = - 0.45), KOOS ADL (r = - 0.30), and KOOS sports (r = - 0.38) in angular difference. CONCLUSIONS: The WB knee flexion angle better correlated with PROM compared with NWB by evaluation of 3D analysis. The larger the angular difference existed between NWB and WB, the lower the PROM score.

Patellar resurfacing has minimal impact on in vitro tibiofemoral kinematics during deep knee flexion in total knee arthroplasty.

BACKGROUND: While patellar resurfacing can affect patellofemoral kinematics, the effect on tibiofemoral kinematics is unknown. We hypothesized that patellar resurfacing would affect tibiofemoral kinematics during deep knee flexion due to biomechanical alteration of the extensor mechanism. METHODS: We performed cruciate-retaining TKA in fresh-frozen human cadaveric knees (N = 5) and recorded fluoroscopic kinematics during deep knee flexion before and after the patellar resurfacing. To simulate deep knee flexion, cadaver knees were tested on a dynamic, quadriceps-driven, closed-kinetic chain simulator based on the Oxford knee rig design under loads equivalent to stair climbing. To measure knee kinematics, a 2-dimensional to 3-dimensional fluoroscopic registration technique was used. Component rotation, varus-valgus angle, and anteroposterior translation of medial and lateral contact points of the femoral component relative to the tibial component were calculated over the range of flexion. RESULTS: There were no significant differences in femoral component external rotation (before patellar resurfacing: 6.6 ± 2.3°, after patellar resurfacing: 7.2 ± 1.8°, p = 0.36), and less than 1° difference in femorotibial varus-valgus angle between patellar resurfacing and non-resurfacing (p = 0.01). For both conditions, the medial and lateral femorotibial contact points moved posteriorly from 0° to 30° of flexion, but not beyond 30° of flexion. At 10° of flexion, after patellar resurfacing, the medial contact point was more anteriorly located than before patellar resurfacing. CONCLUSION: Despite the potential for alteration of the knee extensor biomechanics, patellar resurfacing had minimal effect on tibiofemoral kinematics. Patellar resurfacing, if performed adequately, is unlikely to affect postoperative knee function.