In Vivo Kinematic Analysis of Bicruciate-Retaining Total Knee Arthroplasty Focused on Function of the ACL

uncertain. In this study, we performed an in vivo kinematic analysis of squat motion on level ground and on a downward slope in patients treated with BCR-TKA to examine the value of anterior cruciate ligament (ACL) preservation.Methods: The subjects were ten valgus knees that underwent TKA (BCR: 5 knees, CR: 5 knees) at our hospital. We evaluated in vivo kinematics of the knee using fluoroscopy and investigated the femoral component translation relative to the tibial component from extension to maximum flexion, and the rotation angle between the components under the two conditions. Statistical analysis was conducted by Mann-Whitney U test to compare the rotational angle, the location of lateral and medial contact points per flexion angle. Differences in these parameters between the BCR and CR groups across the flexion angles were compared by repeated measures ANOVA. Results: Rotation of the femoral component to the tibial component occurred gradually as flexion continued. On level ground, lateral rotation at 0° to 120° flexion was 14.5±1.95° in the BCR group and 7.9±0.47° in the CR group. Medial translation was 4.1±1.73mm in the BCR group and 2.5±1.64mm in the CR group, and lateral translation was 13.2±1.6mm in the BCR group and 7.1±1.74mm in the CR group. On a forward slope, lateral rotation was 12.7±1.45° in the BCR group and 7.57±0.47° in the CR group. Medial translation was 5.87±1.78mm in the BCR and 2.9±0.81mm in the CR, and lateral translation was 13.6±1.84mm in the BCR and 7.4±0.96mm in the CR.Conclusion: An in vivo kinetics analysis of deep flexion motion was conducted on level ground and on a forward slope to stress the ACL. Under both conditions, kinetics close to screw home movement were found in the BCR group and rotation was significantly larger than that in the CR group. The medial contact point between components was located significantly more anterior in the BCR group. In conclusion, BCR-TKA was found to have in vivo kinetics close to those of a normal knee, in comparison with CR-TKA.

In Vivo Kinematic Analysis of Bicruciate-retaining Total Knee Arthroplasty Focused on Function of the ACL

Background: The utility of a bi-cruciate retaining total knee arthroplasty (BCR-TKA) is uncertain. In this study, we performed an in vivo kinematic analysis of squat motion on level ground and on a downward slope in patients treated with BCR-TKA to examine the value of anterior cruciate ligament (ACL) preservation.Methods: The subjects were ten valgus knees that underwent TKA (BCR: 5 knees, CR: 5 knees) at our hospital. We evaluated in vivo kinematics of the knee using fluoroscopy and investigated the femoral component translation relative to the tibial component from extension to maximum flexion, and the rotation angle between the components under the two conditions. Statistical analysis was conducted by Mann-Whitney U test to compare the rotational angle, the location of lateral and medial contact points per flexion angle. Differences in these parameters between the BCR and CR groups across the flexion angles were compared by repeated measures ANOVA.Results: Rotation of the femoral component to the tibial component occurred gradually as flexion continued. On level ground, lateral rotation at 0° to 120° flexion was 14.5±1.95° in the BCR group and 7.9±0.47° in the CR group. Medial translation was 4.1±1.73mm in the BCR group and 2.5±1.64mm in the CR group, and lateral translation was 13.2±1.6mm in the BCR group and 7.1±1.74mm in the CR group. On a forward slope, lateral rotation was 12.7±1.45° in the BCR group and 7.57±0.47° in the CR group. Medial translation was 5.87±1.78mm in the BCR and 2.9±0.81mm in the CR, and lateral translation was 13.6±1.84mm in the BCR and 7.4±0.96mm in the CR.Conclusion: An in vivo kinetics analysis of deep flexion motion was conducted on level ground and on a forward slope to stress the ACL. Under both conditions, kinetics close to screw home movement were found in the BCR group and rotation was significantly larger than that in the CR group. The medial contact point between components was located significantly more anterior in the BCR group. In conclusion, BCR-TKA was found to have in vivo kinetics close to those of a normal knee, in comparison with CR-TKA.

The role of vestibular cues in postural sway

Vestibular feedback is important for postural control, but little is known about the role of tilt cues vs. translation cues vs. rotation cues. We studied healthy human subjects with no known vestibular pathology or symptoms. Our findings showed that vestibular encoding of lateral translation correlated with medial-lateral postural sway, consistent with lateral translation cues contributing to balance control. This adds support to the hypothesis that vestibular noise contributes to spontaneous postural sway.

Imperceptible manipulation of lateral camera motion for improved virtual reality applications

We measure detection thresholds for lateral translation gains of virtual camera motion in response to the corresponding head motion under natural viewing. We propose three applications for our method, addressing three key problems in virtual reality, and validate their improvement when our manipulation technique is applied.

A Biomechanical Comparison of 2 Hip Capsular Reconstruction Techniques: Iliotibial Band Autograft Versus Achilles Tendon Allograft

Background: Several techniques for hip capsular reconstruction have been described to address gross instability or microinstability due to capsular deficiency. However, objective biomechanical data to support their use are lacking. Purpose: To compare the kinematic effect of 2 capsular reconstruction techniques (iliotibial band [ITB] graft and Achilles tendon graft). Kinematic effect encompassed rotational range of motion (ROM) as well as joint translation in the coronal, sagittal, and axial planes. Study Design: Controlled laboratory study. Methods: 8 paired, fresh-frozen hemi-pelvises (16 hips) were tested on a custom-designed joint motion simulator in the intact state and after capsulectomy. Pairs were randomly allocated to either ITB or Achilles reconstruction and retested. Testing was performed at 0°, 45°, and 90° of flexion. Internal-external rotation (IR-ER) torques and abduction-adduction torques of 3 N·m were applied to the femur via a load cell at each position, and rotational ROM and joint translation in the coronal, sagittal, and axial planes were recorded. Results: At 45° and 90°, there was a significant effect of the condition of the hip on the total IR-ER ( P = .004, effect size [ES] = 0.305; and P < .001, ES = 0.497; respectively). At 45°, mean ± SD total rotation was significantly greater for the capsulectomy (59.7°± 15.9°) state compared with intact (53.3°± 13.2°; P = .007). At 90°, reconstruction significantly decreased total rotation to 49.0°± 18.9° compared with a mean total rotation of 52.8°± 18.7° after capsulectomy ( P = .02). No difference was seen in the total abduction-adduction of the hip between conditions. Comparisons of the 2 different reconstruction techniques showed no significant differences in total IR-ER or abduction-adduction ROM or joint translation in the coronal, sagittal, or axial planes. For translation, at both 0° and 45° there was a statistically significant effect of the condition on the medial-lateral translation ( P = .033; ES = 0.204). Reconstruction, independent of technique, was successful in significantly decreasing ( P = .030; P = .014) the mean medial-lateral translation at 0° and 45° of hip flexion from 5.2 ± 3.8 mm and 5.6 ± 4.0 mm to 2.8 ± 1.9 mm and 3.9 ± 3.2 mm, respectively. Conclusion: The integrity of the native hip capsule played a significant role in rotational stability, where capsulectomy significantly increased rotational ROM. Both ITB and Achilles reconstruction techniques restored normal rotational ROM of the hip at 90° of flexion as well as coronal plane stability at 0° and 45° of hip flexion. No differences were seen between ITB and Achilles reconstruction techniques. Clinical Relevance: Both capsular reconstruction techniques provide comparable joint kinematics, restoring rotation and translation to normal values with the exception of rotational ROM at 45°, which remained significantly greater than the intact state. The most significant results were the rotational stability at 90° of hip flexion and coronal plane stability at 0° and 45° of hip flexion, which were significantly improved compared with the capsulectomy state.

Kinematics after Syndesmotic Injury: Assessing the Magnitude of Talus and Fibula Rotation and Displacement

Category: Ankle; Sports; Other Introduction/Purpose: High ankle sprains, or injuries to the distal tibiofibular syndesmosis, are predictive of long-term ankle dysfunction. Our objectives were to evaluate ankle mortise stability, radiographically, and kinematically, using a cadaveric model with a simulated syndesmotic injury. We also measured the ability of a suture-button system to restore natural joint motion. Methods: Eight cadaveric specimens underwent serial sectioning of the anterior-inferior tibiofibular (AITFL), interosseous (IOL), posterior-inferior tibiofibular (PITFL), and deltoid ligaments. Specimens underwent external rotation and lateral translation testing after ligament release to obtain kinematic data (using a validated infrared LED motion capture system) and radiographic measurements. We then repeated external rotation and lateral translation testing after implementing a suture-button system. Repeated measures ANOVA with a Bonferroni/Dunn post-hoc test calculated the interspecimen comparisons. Results: Sectioning of each ligament, beginning with the AITFL, significantly increased talar external rotation. After releasing the AITFL and IOL, fibular external rotation increased significantly. Posterior displacement of the fibula began following the release of AITFL. Significant radiographic widening of the medial clear space and the syndesmosis occurred only after the release of the deltoid ligament. Syndesmotic and medial clear space widening was not significantly different from the intact state under lateral translation until after the release of the deltoid ligament. Placement of the suture-button system successfully reduced the medial clear space but was unable to restore the native stability of the ankle joint. Conclusion: This project addresses rotational and kinematic changes in the ankle after syndesmotic injury by quantifying the effect of ligamentous disruption on the tibiotalar articulation. The change in joint kinematics may explain why patients with moderate-to-severe syndesmosis injuries take longer to heal and develop long-term dysfunction. Significant talar rotation and posterior fibular displacement occur during external rotation, even with moderate syndesmosis injury, and before the disruption of the deltoid ligament. Stress radiography does not appear to be a reliable indicator of mild or moderate syndesmosis injuries.

Hybrid Fixation Restores Tibiofibular Kinematics for Early Weightbearing After Syndesmotic Injury

Background: Disruption of the anterior inferior tibiofibular ligament (AITFL), posterior inferior tibiofibular ligament (PITFL), and interosseous membrane (IOM) is a predictive measure of residual symptoms after an ankle injury. Controversy remains regarding the ideal fixation technique for early return to sport, which requires restoration of tibiofibular kinematics with early weightbearing. Purpose: To quantify tibiofibular kinematics after syndesmotic fixation with different tricortical screw and suture button constructs during simulated weightbearing. Study Design: Controlled laboratory study. Methods: A 6 degrees of freedom robotic testing system was used to test 9 fresh-frozen human cadaveric specimens (mean age, 65.1 ± 17.3 years). A 200-N compressive load was applied to the ankle, while a 5-N·m external rotation and a 5-N·m inversion moment were applied independently to the ankle at 0° of flexion, 15° and 30° of plantarflexion, and 10° of dorsiflexion. Fibular medial-lateral translation, anterior-posterior translation, and internal-external rotation relative to the tibia were tracked by use of an optical tracking system in the following states: (1) intact ankle; (2) AITFL, PITFL, and IOM transected ankle; (3) single-screw fixation; (4) double-screw fixation; (5) hybrid fixation; (6) single suture button fixation; and (7) divergent suture button fixation. Repeated-measures analysis of variance with Bonferroni correction was performed for statistical analysis. Results: In response to the external rotation moment and axial compression, single tricortical screw fixation resulted in significantly higher lateral translation of the fibula compared with that of the intact ankle at 10° of dorsiflexion ( P < .05). Suture button fixation resulted in significantly higher posterior translation of the fibula at 0° of flexion and 10° of dorsiflexion, whereas divergent suture button fixation resulted in higher posterior translation at only 0° of flexion ( P < .05). In response to the inversion moment and axial compression, single tricortical screw and hybrid fixation significantly decreased lateral translation in plantarflexion, whereas double tricortical screw fixation and hybrid fixation significantly decreased external rotation of the fibula compared with that of the intact ankle at 15° of plantarflexion ( P < .05). Conclusion: Based on the data in this study, hybrid fixation with 1 suture button and 1 tricortical screw may most appropriately restore tibiofibular kinematics for early weightbearing. However, overconstraint of motion during inversion may occur, which has unknown clinical significance. Clinical Relevance: Surgeons may consider this data when deciding on the best algorithm for syndesmosis repair and postoperative rehabilitation.