Alexandre Fuentes

Gait adaptation in chronic anterior cruciate ligament-deficient patients: Pivot-shift avoidance gait

BACKGROUND A variety of biomechanical adaptations of the knee during gait have been reported in ACL-deficient patients to cope with anteroposterior knee instability. However, strategies to prevent rotatory knee instability are less recognized. We hypothesized that ACL-deficient patients would make distinctive gait changes to prevent anterolateral rotatory knee instability. Specifically, we hypothesized that during the terminal stance phase of the gait cycle, ACL-deficient patients would reduce the internal rotation knee joint moment and exhibit a higher knee flexion angle. We call this altered gait a pivot-shift avoidance gait. We also hypothesized that patients would not be able to adapt their knee biomechanics as efficiently at a fast gait speed. METHODS Twenty-nine patients with chronic ACL deficiency and 15 healthy volunteers took part in a treadmill gait analysis. The terminal stance phase was analyzed under both comfortable and fast gait speed conditions. FINDINGS At both gait speeds, ACL-deficient patients significantly reduced the internal rotation knee joint moment and showed larger knee flexion angles during the terminal stance phase of the gait cycle than did the control group. However, the difference in the minimum knee flexion angle between groups under the fast gait speed condition was not statistically significant. INTERPRETATION ACL-deficient patients adopted the proposed pivot-shift avoidance gait, possibly to prevent anterolateral rotatory knee instability. The patients were not able to adapt their knee biomechanics as effectively during fast-paced walking. This study reinforces the pertinence of gait analysis in ACL-deficient knees to acquire more information about the function of the knee joint.

Comparison of soft tissue artifact and its effects on knee kinematics between non-obese and obese subjects performing a squatting activity recorded using an exoskeleton

BACKGROUND Rigid attachment systems are one of the methods used to compensate for soft tissue artifact (STA) inherent in joint motion analyses. RESEARCH QUESTION The goal of this study was to quantify STA of an exoskeleton design to reduce STA at the knee, and to assess the accuracy of 3D knee kinematics recorded with the exoskeleton in non-obese and obese subjects during quasi-static weight-bearing squatting activity using biplane radiography. METHODS Nine non-obese and eight obese subjects were recruited. The exoskeleton was calibrated on each subject before they performed a quasistatic squatting activity in the EOS® imaging system. 3D models of exoskeleton markers and knee bones were reconstructed from EOS® radiographs; they served to quantify STA and to evaluate differences between the markers and bones knee kinematics during the squatting activity. RESULTS The results showed that STA observed at the femur was larger in non-obese subjects than in obese subjects in frontal rotation (p = 0.004), axial rotation (p = 0.000), medio-lateral displacement (p = 0.000) and antero-posterior displacement (p = 0.019), while STA observed at the tibia was lower in non-obese subjects than in obese subjects for the three rotations (p < 0.05) and medio-lateral displacement (p = 0.015). Differences between the markers and bones knee kinematics increased with knee flexion and were similar in both groups, except for abduction-adduction: 4.9° for non-obese subjects against 2.3° for obese subjects (p = 0.011). SIGNIFICANCE This study demonstrated that STA at the femur and its impact on knee abduction-adduction using a specific exoskeleton were greater among non-obese subjects than obese subjects, which is encouraging for future biomechanical studies on pathologies such as osteoarthritis.

Total knee arthroplasty with unexplained pain : New insights from kinematics

IntroductionUp to 20% of total knee arthroplasty patients remain unsatisfied post-surgery, and a large proportion of them report anterior knee pain. This study aims to verify whether patients who experience anterior knee pain after total knee arthroplasty (TKA) will exhibit kinematic characteristics similar to those associated with patellofemoral syndrome, including in the frontal and transverse planes.Materials and methodsUsing four different assessment methods [radiological, patient-reported outcome, musculoskeletal assessment with functional performance testing, and a 3D kinematic assessment during gait], the clinical and 3D knee kinematic profiles of three groups were compared: a painful and an asymptomatic TKA group and a healthy control group. All three groups underwent a three-dimensional kinematic knee assessment while walking on a treadmill. Prosthetic component rotation was assessed through a CT scan measurement performed by one experienced radiologist. Flexion/extension, ab/adduction, and tibial internal rotation curves were compared, and significant differences were highlighted through ANCOVA analysis performed on SPSS.ResultsA total of 62 knees were evaluated, 24 asymptomatic, 21 painful, and 17 control. A dynamic flexion contracture during gait was observed in the painful group, which was associated with a lack of flexibility of the thigh muscles. Moreover, painful TKA cases exhibited a valgus alignment (− 1.5°) during stance, which increases the Q angle and lateralizes the patella. Finally, CT scan evaluation of painful total knee arthroplasty patients revealed that their combined components rotation was in slight internal rotation (− 1.4°, SD 7.0°).ConclusionsPainful TKA patients presented three well-known characteristics that tend to increase patellofemoral forces and that could be the cause of the unexplained pain: a stiff knee gait, a valgus alignment when walking, and combined TKA components slightly internally rotated.

Mechanical biomarkers of medial compartment knee osteoarthritis diagnosis and severity grading: Discovery phase

OBJECTIVE To investigate, as a discovery phase, if 3D knee kinematics assessment parameters can serve as mechanical biomarkers, more specifically as diagnostic biomarker and burden of disease biomarkers, as defined in the Burden of Disease, Investigative, Prognostic, Efficacy of Intervention and Diagnostic classification scheme for osteoarthritis (OA) (Altman et al., 1986). These biomarkers consist of a set of biomechanical parameters discerned from 3D knee kinematic patterns, namely, flexion/extension, abduction/adduction, and tibial internal/external rotation measurements, during gait recording. METHODS 100 medial compartment knee OA patients and 40 asymptomatic control subjects participated in this study. OA patients were categorized according to disease severity, by the Kellgren and Lawrence grading system. The proposed biomarkers were identified by incremental parameter selection in a regression tree of cross-sectional data. Biomarker effectiveness was evaluated by receiver operating characteristic curve analysis, namely, the area under the curve (AUC), sensitivity and specificity. RESULTS Diagnostic biomarkers were defined by a set of 3 abduction/adduction kinematics parameters. The performance of these biomarkers reached 85% for the AUC, 80% for sensitivity and 90% for specificity; the likelihood ratio was 8%. Burden of disease biomarkers were defined by a 3-decision tree, with sets of kinematics parameters selected from all 3 movement planes. CONCLUSION The results demonstrate, as part of a discovery phase, that sets of 3D knee kinematic parameters have the potential to serve as diagnostic and burden of disease biomarkers of medial compartment knee OA.

Clinical and Biomechanical Evaluations of Staged Bilateral Total Knee Arthroplasty Patients with Two Different Implant Designs

Background: Various implants of total knee arthroplasty (TKA) are used in clinical practice and each presents specific design characteristics. No implant managed this day to reproduce perfectly the biomechanics of the natural knee during gait. Objectives: We therefore asked whether (1) differences in tridimensional (3D) kinematic data during gait could be observed in two different designs of TKA on the same patients, (2) if those gait kinematic data are comparable with those of asymptomatic knees and (3) if difference in clinical subjective scores can be observed between the two TKA designs on the same patient. Methods: We performed knee kinematic analysis on 15 patients (30 TKAs) with two different TKA implant designs (Nexgen, Zimmer and Triathlon, Stryker) on each knee and on 25 asymptomatic subjects (35 knees). Clinical evaluation included range of motion, weight bearing radiographs, questionnaire of joint perception, KOOS, WOMAC and SF-12. Results: Comparison between TKAs and asymptomatic knees revealed that asymptomatic knees had significantly less knee flexion at initial contact (p < 0.04) and more flexion for most of the swing phase (p between 0.004 and 0.04). Asymptomatic knees also had less varus at loading response, during stance phase and during most of the swing phase (p between 0.001 - 0.05). Transverse plane analysis showed a tendency for asymptomatic knees to be more in internal rotation during stance phase (p 0.02 - 0.04). Comparing both TKA designs, NexgenTM implant had significantly more flexion at the end of swing phase (p = 0.04) compared to knees with the TriathlonTM implant. In frontal plane, from initial contact to maximum mid stance angle and between the mean mid stance angle and initial contact NexgenTM TKA had significantly more adduction (varus, p =0.02 – 0.03). Clinical scores of both TKAs did not have significant difference. Conclusions: TKA with the tested implants did not reproduce natural knee kinematics during gait. In our cohort of patients, TKA implant design translated in limited kinematics differences during gait and on clinical results.

Healthy 3D knee kinematics during gait: Differences between women and men, and correlation with x-ray alignment

BACKGROUND Normal 3D knee kinematics during gait is still not well understood, especially regarding differences between women and men. RESEARCH QUESTION The objective of the present study was to characterize 3D knee kinematics during gait in healthy women and men with a validated tool. METHODS Knee kinematics was analysed with the KneeKG™ system in 90 healthy subjects (49 females and 41 males). 3D knee rotations were compared between women and men, and between right and left knees. Each subject underwent full-length weight-bearing x-rays. Correlations between abduction-adduction angles and lower-limb alignment measures on x-rays were assessed. RESULTS In the frontal plane, 2.0-5.0° more abduction occurred in women compared to men (0.000 ≤ p ≤ 0.015) throughout the entire gait cycle. In the transverse plane, 2.4-3.7° more external tibial rotation was seen in women than in men (0.002 ≤ p ≤ 0.041) during the initial and mid-swing phases. No difference was found between the right and left knees. Low correlations (-0.52 ≤ r≤-0.41, p < 0.001) were observed between radiographic hip-knee-ankle angle (HKA) and abduction-adduction angles throughout the stance phase. SIGNIFICANCE Kinematic differences between women and men in the frontal plane can be partly explained by their anatomical differences: women were less in varus than men (HKA of -0.8° vs. -2.6°, p < 0.001). Our study contributes to a better understanding of healthy 3D knee kinematics during gait and highlights the need for accounting of gender differences in future investigations. Better knowledge of natural knee kinematics will be helpful in assessing pathological gait patterns or determining the efficiency of conservative and surgical treatments to restore normal kinematics.

Short-term Impact of Anterior Cruciate Ligament Reconstruction in an Adolescent Population on 3D Knee Kinematics

Objectives: Gait analysis is a proven method for assessing knee biomechanical adaptations in anterior cruciate ligament deficient (ACLD) patients and to quantify the impact of the reconstructive surgery (ACLR). In an adult population, ACLR has shown partial kinematic correction, as they remain in internal tibial rotation, putting them at risk of rotational instability and develop osteoartitis. ACLD adolescents likely adopt similar gait changes to reduce knee instability, but may show quicker or more return to the normal compared to adults. The purpose of this study is to compare the tridimensional (3D) knee kinematics before and after ACLR in adolescents. Methods: 25 ACLD patients aged between 13 and 19 years old on a waiting list for ACLR were recruited. Bilateral knee 3D kinematic data was gathered during treadmill walking at comfortable self-selected speed using the KneeKGTM System before and 6-9 months after ACLR. Each participant underwent the same surgical protocol (2-strand hamstring tendon graft, hamstring harvest proximally and kept distally, transphyseal tibial tunnel and transepiphyseal femoral tunnel) by the same experienced surgeon. Three analyses were done: ACLD knee pre vs. post-surgery, contralateral healthy knee pre vs. post-surgery, and ACLR knee vs. healthy contralateral knee. Results: In the sagittal and transverse planes, kinematic patterns remained similar to the pre-op; maintaining the characteristic knee flexion gait pattern during single support phase which is well documented in adult ACLD (hamstring facilitation strategy). The ACLR knee exhibited a more valgus dynamic alignment compared to pre-surgery throughout the gait cycle. The healthy contralateral knee kinematics displayed no significant changes in the frontal and sagittal planes after surgery compared to the pre-op pattern. In the transverse plane, post-op gait analysis showed significantly more external rotation at heel-strike and through weight acceptance. While looking at the gait symmetry post-surgery, ACLR knee revealed significantly more valgus while remaining in greater flexion during single limb support. In the transverse plane, an external rotation tendency is observed in the ACLR knee throughout the gait cycle, except during weight acceptance. Conclusion: This study shows that kinematic adaptations found in ACLD adolescents are likely to endure short term after surgery. For example, the greater knee flexion gait pattern used before surgery is still used after ACLR. Interestingly, adolescents used an external tibial rotation adaptation to limit internal tibial instability before the surgery and this pattern was still present post-surgery. Even if theses protection strategies are efficient, the increased dynamical valgus movement seen could place the graft under pressure while increasing patellofemoral stresses, a common complaint after ACLR. Lastly, post-surgery, the contralateral knee seems to mimic the external tibial rotation gait pattern strategy seen in ACL-knee. This study demonstrates that gait protective strategies are still present short term after the surgery. Biomechanical assessment helps ID these adaptations to optimize post-op rehabilitation and prevent secondary injuries.

Three-Dimensional Biomechanical Assessment of Knee Ligament Ruptures

The complex biomechanics of the human knee joint are the result of an equilibrium of forces exerted by its surrounding soft tissue structures. When one of these forces is removed, as is the case when a ligament ruptures, a redistribution of forces occurs and the biomechanical properties of the knee are altered. One of the most frequently diagnosed knee ligament ruptures is that of the anterior cruciate ligament (ACL). Such a rupture causes increased laxity of the knee joint as well as a complex rotational and translational instability whereby many patients describe a feeling that their knee is slipping, or “giving way.

3D knee kinematics variability pre-operation versus post-operation in adolescence with Anterior Cruciate Ligament injury using functional principle component analysis

Background: Anterior cruciate ligament (ACL) injuries in adolescents have increased in the past decade. The goal of ACL reconstructive surgery is to restore knee stability, however apart from subjective manual testing, there is no objective method to assess the impact of the treatment on knee stability. In clinical biomechanics, decreased variability in three dimensional (3D) kinematic angles can be associated with increased stability of the joint in performing a movement. Typically, the study of variability of 3D knee kinematics proceeds by reducing what are intrinsically functional responses to a single discrete measurement (e.g. peak flexion angle). As a result, many potentially informative data is ignored. Aim: Prospective gait variability analysis pre- and 6 months post- ACL reconstructive surgery in adolescence patients using Principle Component Analysis (FPCA). Method: FPCA is a multivariate statistical data analysis technique that focuses on treating an entire dataset as functions. Twenty eight ACL adolescent patients pre- and post-operation walked on a treadmill and the 3D knee kinematics were collected (flexion/extension, abduction/adduction and internal/external rotation angles). Functional Principle Component (FPCs) scores of the angle data were extracted to compare variability in gait. Repeated measures of ANOVA and box plots on FPC scores provided evidence of significant difference with decreased variability post-operation for both within-group and within-patients studies. Conclusion: Variability in the 3D knee kinematics have been significantly reduced six months post- versus pre-operation. The proposed functional objective assessment method suggests that ACL reconstructive surgery increases joint stability during walking in adolescents.

Biomechanical signal classification of surgical and non-surgical candidates for knee arthroplasty

The purpose of this article is two-fold : (1) to select a set of bio-mechanical features to characterize arthroplasty candidates and, (2) design a surgical and non-surgical candidate classifier via decision trees. The biomechanical features are generated from 3D knee kinematic patterns, namely, flexion-extension, abduction-adduction, and tibial internal-external rotation measurements taken during gait recordings. The selection of features is done by incremental selection of biomechanical parametes in a classification tree of cross-sectional data. These features are then used to generate decision rules for classification. The effectiveness of the classifier is evaluated by receiver operating characteristic curve analysis, namely, the area under the curve (AUC), sensitivity, and specificity. The classification accuracy is 85% for AUC, 80% for sensitivity, and 90% for specificity. These results demonstrate the effectiveness of the selected biomechanical features and decision tree classifier to perform automatic and objective classification of surgical and non-surgical candidates for arthroplasty.