External Adduction Moment Research Articles

The effect of prosthetic foot stiffness category on intact limb knee loading associated with osteoarthritis in people with transtibial amputation

Lower limb prosthesis users are at an increased risk of developing osteoarthritis in their intact knee. There is a scarcity of literature examining how the stiffness properties of commercially available prosthetic feet impact gait mechanics, including knee loading biomechanical variables that have been associated with the development of osteoarthritis. This study aimed to isolate the effect of commercial prosthetic foot stiffness on intact knee loading, prosthetic foot–ankle biomechanics, and user perception. Seventeen males with unilateral transtibial amputation were fit with three consecutive foot stiffness categories of a standardized energy-storing prosthetic foot in a randomized order and while blinded to foot condition. Biomechanical and self-report data were collected during level-ground walking in a motion analysis laboratory. As prosthetic foot stiffness increased, contralateral knee external adduction moment significantly decreased between stiff vs. medium and stiff vs. soft foot conditions. Prosthetic foot rollover radius increased as foot stiffness increased. However, prosthetic foot–ankle push-off peak power and work decreased as foot stiffness increased. On average, users favored the medium stiffness condition and were able to correctly identify the foot stiffness condition. Overall, these results raise questions about the relative contributions of foot stiffness and ankle push-off power to changes in contralateral knee loading. The findings contribute to our understanding of the relationships between prosthetic foot mechanical properties and gait biomechanical variables at the contralateral knee when prosthetic foot stiffness is modified without a corresponding alignment adjustment.

Are 7 MM neoprene knee sleeves capable of modifying the knee kinematics and kinetics during box jump and front squat exercises in healthy CrossFit practitioners? An exploratory cross-sectional study

ObjectiveInvestigate whether wearing 7 mm neoprene knee sleeves during the front squat and box jump CrossFit exercises change the biomechanics of the knee joint. Designa cross-sectional exploratory study. SettingLaboratory-based. ParticipantsSeventeen male healthy CrossFit participants completed front squats and box jumps with knee sleeves (KS) and without knee sleeves (WKS). Main outcomes measuresKinematic and kinetic data of the knee in the sagittal, frontal and transverse planes were obtained for the two tasks and under the two experimental situations. The maximum load lifted on 1 MR test was recorded under KS and WKS conditions. The GROC scales were applied after each exercise and condition to assess participants' self-reported perception of stability. ResultsThe KS reduced the knee range of motion in the transverse plane during box jump (p = 0.029) and the peak knee external adduction moment (p = 0.047) during front squat compared to WKS. The 1RM during front squat increased in KS compared to WKS (p < 0.001). Most participants (94%) reported that they felt better stability using KS and all participants (100%) believed that knee sleeves would avoid knee pain. Conclusionneoprene knee sleeves have little impact on the biomechanics of the knee joint during CrossFit. However, participants reported improved knee stability.

A novel pivot ankle/foot prosthesis reduces sound side loading and risk for osteoarthritis: a pragmatic randomized controlled trial.

Background:Individuals with unilateral transtibial amputation are at risk of abnormal mechanical joint loading and development of osteoarthritis on sound side joint structures.Objectives:This study describes the spatiotemporal and kinetic and kinematic parameters related to osteoarthritis in participants while using (A) a solid-ankle cushioned-heel prosthesis (SACH), (B) a conventional energy storage and return (ESAR) foot prosthesis, and (C) a novel ESAR (N-ESAR) foot prosthesis.Study design:A pragmatic randomized controlled trial.Methods:K3–K4 ambulators used three feet in a 2-week randomized cross-over order. Kinetics of vertical ground reaction forces (vGRFs) and 3D kinematics of joint angles were integrated to provide normalized parameters. Data were analyzed using one way and mixed model Analysis of variance (ANOVAs) (p < 0.05) and Cohen d statistic.Results:Twenty participants, aged 40 ± 16 years with body mass index of 24.7 ± 3.6 kg/m2, experienced minimal change in the spatiotemporal parameters between feet. Participants using the N-ESAR foot prosthesis experienced reduced peak knee external adduction moment (p = 0.030), peak vGRFs (p < 0.001), and peak loading rate of vGRFs (p = 0.030). Peak knee flexion moments only changed when using the solid-ankle cushioned-heel prosthesis, in a positive direction (p = 0.014). Using the N-ESAR prosthesis also increased peak distal shank power during late stance phase (p < 0.001).Conclusions:A novel ankle/foot ESAR prosthesis reduces loading on the sound side. With extended use of the N-ESAR foot prosthesis, these findings may provide the prosthesis user with improved outcomes related to sound side loading and development of osteoarthritis.

Dynamic Knee Joint Line Orientation Is Not Predictive of Tibio-Femoral Load Distribution During Walking.

Some approaches in total knee arthroplasty aim for an oblique joint line to achieve an even medio-lateral load distribution across the condyles during the stance phase of gait. While there is much focus on the angulation of the joint line in static frontal radiographs, precise knowledge of the associated dynamic joint line orientation and the internal joint loading is limited. The aim of this study was to analyze how static alignment in frontal radiographs relates to dynamic alignment and load distribution, based on direct measurements of the internal joint loading and kinematics. A unique and novel combination of telemetrically measured in vivo knee joint loading and simultaneous internal joint kinematics derived from mobile fluoroscopy (“CAMS-Knee dataset”) was employed to access the dynamic alignment and internal joint loading in 6 TKA patients during level walking. Static alignment was measured in standard frontal postoperative radiographs while external adduction moments were computed based on ground reaction forces. Both static and dynamic parameters were analyzed to identify correlations using linear and non-linear regression. At peak loading during gait, the joint line was tilted laterally by 4°–7° compared to the static joint line in most patients. This dynamic joint line tilt did not show a strong correlation with the medial force (R 2: 0.17) or with the mediolateral force distribution (pseudo R 2: 0.19). However, the external adduction moment showed a strong correlation with the medial force (R 2: 0.85) and with the mediolateral force distribution (pseudo R 2: 0.78). Alignment measured in static radiographs has only limited predictive power for dynamic kinematics and loading, and even the dynamic orientation of the joint line is not an important factor for the medio-lateral knee load distribution. Preventive and rehabilitative measures should focus on the external knee adduction moment based on the vertical and horizontal components of the ground reaction forces.

Static and dynamic abductor function are both associated with physical function 1 to 5 years after total hip arthroplasty

BackgroundA subset of total hip arthroplasty patients experience functional impairments past the first postoperative year. Poor hip abductor function is common before and in the early postoperative period. It is not known if abductor impairment is associated with long-term functional impairment. This study evaluated the relationships between static and dynamic abductor function and performance-based and self-reported function >1 year post-total hip arthroplasty. MethodsEighteen adults 1–5 years post-total hip arthroplasty participated. Static and dynamic abductor function were assessed through dynamometry and gait analysis, respectively. Subjects completed four physical performance tests and two self-report instruments. FindingsHigher peak isometric abductor strength was associated with better performance-based function (P ≤ 0.001–0.030) and with self-reported function (P ≤ 0.001–0.012). Higher peak external adduction moment was associated with better results on 3 of 4 performance tests (P = 0.007–0.026). Together, static and dynamic abductor function predicted 35–77% of the variation in physical function. Abductor strength best predicted walking test results and self-reported function, while dynamic abductor function best predicted tests involving sit-to-stand InterpretationStatic and dynamic abductor function were associated with physical function 1–5 years after total hip arthroplasty. These results support further investigation of interventions targeting abductor function for persons experiencing persistent impairments.

The effect of angle and moment of the hip and knee joint on iliotibial band hardness

Although several studies have described kinematic deviations such as excessive hip adduction in patients with iliotibial band (ITB) syndrome, the factors contributing to increased ITB hardness remains undetermined, owing to lack of direct in vivo measurement. The purpose of this study was to clarify the factors contributing to an increase in ITB hardness by comparing the ITB hardness between the conditions in which the angle, moment, and muscle activity of the hip and knee joint are changed. Sixteen healthy individuals performed the one-leg standing under five conditions in which the pelvic and trunk inclination were changed in the frontal plane. The shear elastic modulus in the ITB was measured as an indicator of the ITB hardness using shear wave elastography. The three-dimensional joint angle and external joint moment in the hip and knee joints, and muscle activities of the gluteus maximus, gluteus medius, tensor fasciae latae, and vastus lateralis, which anatomically connect to the ITB, were also measured. ITB hardness was significantly increased in the posture with pelvic and trunk inclination toward the contralateral side of the standing leg compared with that in all other conditions (increase of approximately 32% compared with that during normal one-leg standing). This posture increased both the hip adduction angle and external adduction moment at the hip and knee joint, although muscle activities were not increased. Our findings suggest that coexistence of an increased adduction moment at the hip and knee joints with an excessive hip adduction angle lead to an increase in ITB hardness.

Knee muscle strength after recent partial meniscectomy does not relate to 2-year change in knee adduction moment.

Knee muscle weakness and a greater external knee adduction moment are suggested risk factors for medial tibiofemoral knee osteoarthritis. Knee muscle weakness and a greater knee adduction moment may be related to each other, are potentially modifiable, and have been observed after arthroscopic partial meniscectomy. The aim of this exploratory study was to determine if knee muscle weakness 3 months after arthroscopic partial meniscectomy (baseline) is associated with an increase in external knee adduction parameters during the subsequent 2 years. Eighty-two participants undergoing medial arthroscopic partial meniscectomy were assessed at baseline, and 66 participants who were reassessed 2 years later were included in our study. Isokinetic muscle strength and external adduction moment parameters (peak and impulse) during normal and fast walking were measured at baseline and followup. Multiple linear regression models were used to examine the association between baseline muscle strength and 2-year change in adduction moment parameters. A post hoc power calculation showed we had 80% power to detect a correlation of 0.31 between baseline muscle strength and change in the external knee adduction, with an alpha error of 0.05 and two-sided significance. Maximal isokinetic muscle strength 3 months after arthroscopic partial meniscectomy was not associated with change in adduction moment parameters (p value range from 0.12 to 0.96). No evidence was found to suggest that improving maximal knee muscle strength after a recent arthroscopic partial meniscectomy would reduce change in knee adduction moment observed during the subsequent 2 years. As muscle function is modifiable, future investigation of other aspects of muscle function that may relate to change in knee adduction moment is warranted.

Influences of alignment and obesity on knee joint loading in osteoarthritic gait

To determine the influences of frontal plane knee alignment and obesity on knee joint loads in older, overweight and obese adults with knee osteoarthritis (OA). Cross-sectional investigation of alignment and obesity on knee joint loads using community dwelling older adults (age ≥ 55 years; 27 kg m(-2) ≥ body mass or body mass index (BMI) ≤ 41 kg m(-2); 69% female) with radiographic knee OA that were a subset of participants (157 out of 454) enrolled in the Intensive Diet and Exercise for Arthritis (IDEA) clinical trial. A higher BMI was associated with greater (P = 0.0006) peak knee compressive forces [overweight, 2411 N (2182, 2639), class 1 obesity, 2772 N (2602, 2943), class 2+ obesity, 2993 N (2796, 3190)] and greater (P = 0.004) shear forces [overweight, 369 N (322, 415), class 1 obesity, 418 N (384, 453), class 2+ obesity, 472 N (432, 513)], independent of alignment, and varus alignment was associated (P < 0.0001) with greater peak external knee adduction moments, independent of BMI [valgus, 18.7 Nm (15.1, 22.4), neutral, 27.7 Nm (24.0, 31.4), varus, 37.0 Nm (34.4, 39.7)]. BMI and alignment were associated with different joint loading measures; alignment was more closely associated with the asymmetry or imbalance of loads across the medial and lateral knee compartments as reflected by the frontal plane external adduction moment, while BMI was associated with the magnitude of total tibiofemoral force. These data may be useful in selecting treatment options for knee OA patients (e.g., diet to reduce compressive loads or bracing to change alignment).

Does Intact Limb Loading Differ in Servicemembers With Traumatic Lower Limb Loss?

The initiation and progression of knee and hip arthritis have been related to limb loading during ambulation. Although altered gait mechanics with unilateral lower limb loss often result in larger and more prolonged forces through the intact limb, how these forces differ with traumatic limb loss and duration of ambulation have not been well described. The purpose of this study was to determine whether biomechanical variables of joint and limb loading (external adduction moments, vertical ground reaction force loading rates, and impulses) are larger in the intact limb of servicemembers with versus without unilateral lower limb loss and whether intact limb loading differs between shorter (≤ 6 months) versus longer (≥ 2 years) durations of ambulation with a prosthesis. A retrospective review was conducted of all clinical and research gait evaluations performed in the biomechanics laboratory at Walter Reed Army Medical Center and Walter Reed National Military Medical Center between January 2008 and December 2012. Biomechanical data meeting all inclusion and exclusion criteria were obtained for 32 individuals with unilateral transtibial limb loss, 49 with unilateral transfemoral limb loss, and 28 without limb loss. Individuals with unilateral lower limb loss were separated by their experience ambulating with a prosthesis at the time of the gait collection, ≤ 6 months or ≥ 2 years, to determine the effect of duration of ambulation with a prosthesis. Intact limb mean and peak vertical ground reaction force loading rates (median [range; 95% confidence interval]) were larger for transtibial subjects with ≤ 6 months of experience ambulating with a prosthesis versus control subjects (mean: 12.13 body weight [BW]/s [4.45-16.79; 10.18-12.81] versus 9.03 BW/s [4.64-14.47; 8.26-9.74]; effect size [ES] = 0.40; p = 0.003; and peak: 17.23 BW/s [6.58-25.25; 15.46-19.01] versus 13.60 BW/s [9.82-19.51; 12.98-15.05]; ES = 0.43; p = 0.001), respectively. Intact limb mean and peak vertical ground reaction force loading rates were also larger in subjects with transfemoral limb loss with ≤ 6 months and ≥ 2 years of experience ambulating with a prosthesis versus control subjects (mean: 12.67 BW/s [5.88-18.15; 11.06-14.47] and 12.59 BW/s [8.08-17.39; 11.83-13.68] versus 9.03 BW/s [4.64-14.47; 8.26-9.74]; ES ≥ 0.53; p < 0.001; peak: 19.82 BW/s [11.93-29.43; 18.35-23.05] and 21.33 BW/s [16.68-36.69; 20.66-24.26] versus 13.60 BW/s [9.82-19.51; 12.98-15.05]; ES ≥ 0.68; p < 0.001, respectively). Similarly, intact limb vertical ground reaction force impulses (0.63 BW·s [0.53-0.81; 0.67-0.69] and 0.62 BW·s [0.55-0.74; 0.60-0.63] versus 0.57 BW·s [0.50-0.66; 0.55-0.58]; ES ≥ 0.53, p < 0.001) were also larger among both groups of transfemoral subjects versus control subjects, respectively. Limb loading variables were not statistically different between times ambulating with a prosthesis within groups with transtibial or transfemoral limb loss. Larger intact limb loading in individuals with traumatic transtibial loss were only noted early in the rehabilitation process, but these variables were present early and late in the rehabilitation process for those with transfemoral limb loss. Such evidence suggests an increased risk for early onset and progression of arthritis in the intact limb, especially in those with transfemoral limb loss. Interventions should focus on correcting modifiable gait mechanics associated with arthritis, particularly among individuals with transfemoral limb loss, to potentially mitigate the development and progression in this population.

Insight from direct in vivo measurements on the force distribution across the human knee in flexion: can it be modified, and can the internal loads be predicted from external measurements?

Purpose: An understanding of the medio-lateral distribution of the tibiofemoral (TF) contact forces and the factors influencing this distribution is essential for the targeted development and evaluation of interventions aiming to influence the progression of osteoarthritis. Mechanical models of the human knee have provided a basic understanding of the load distribution at the joint, suggesting a strong correlation between frontal plane alignment and medial loading during walking, when the knee is loaded in a rather extended position. The results obtained here are, however, sensitive to the many assumptions necessary to establish themodels, and it remains unclear whether those relationships still hold when the knee is loaded in flexion. Goal of this study was to quantify the medio-lateral force distribution in deep knee flexion using direct measurements of the in vivo knee loading conditions and to examine whether and if so by how much the load distribution can be changed in flexion. In addition, we aimed to assess whether more readily available measures such as the dynamic external knee adduction moment (EAM) or static frontal plane alignment were able to predict the internal loading conditions in deep knee flexion. Methods: Gait analysis was performed on 9 total knee replacement (TKR) patients with a post-op mechanical axis angle (MAA) ranging from 4.5 valgus to 7 varus. Telemetric implants provided access to the in vivo TF contact forces and the ratio of the medial to total contact force (MR), while kinematics and external knee moments were determined using inverse dynamics analyses based on synchronously collected ground reactions forces and skin marker data for variants of squatting. While maintaining the reference position of their feet established for the neutral squat (approximately shoulder-width apart, 9 subjects), additional data from 6 of these subjects was available where they were asked to squeeze their knees together (valgus squat) or push their knees apart (varus squat). To assess whether knee loading can be modified in deep flexion, the medial contact force (Fmed) and the MR were compared between varus and valgus squats, while linear regression analyses assessed the relation between the external adduction moment (EAM) and either Fmed or the MR and whether the MAA explained any variance in the internal forces. All subjects provided written informed consent to participate in the procedures and the study was approved by the local ethics committee. Results: The mean MR for the valgus squats (0.33 0.09) was lower (p 0.05). During the neutral squats the patients reached a similar mean peak knee flexion of 95.6 , while the mean MR and Fmed were 0.40 08 and 0.96 0.:32BW, respectively. Linear regression analysis across the 9 subjects revealed a stronger association between EAM andMR (R2 1⁄4 0.88) than between EAM and Fmed (R2 1⁄4 0.62) (Figure 1).

Can the kinematics of the pelvis and the trunk during single-leg standing predict the external adduction moment of the knee during walking?

of the medial femorotibial joint cartilage were assessed using a 3T MR system (Verio; Siemens). The whole and superficial (half of the whole cartilage) cartilage in the medial knee joint were assessed. The study was approved the Ethics Committee, and the nature of the study was explained to all participants, and written informed consent was obtained. Results: The peak knee adduction moment (external) and angle between the 20s (4.8 10z 1.9 10 z) and 40s (5.8 10z 1.7 10 z) during free gait was not significantly different (Fig. 2). Although the first peaks of knee flexionmoment in the 40s (5.7 10z 1.7 10 z) were significantly larger than the values in the 20s (3.2 10z 2.6 10 z) (Fig. 3, P < 0.05), the knee flexion angle between the 20s and 40s was not significantly different. T2 values of the femoral superficial cartilage in the 40s (34.0 1.8 msec) were significantly higher than the values in the 20s (32.2 1.4 msec) (P < 0.01). The first peak of the knee flexion moment and the T2 in the 40s were not significantly correlated (r 1⁄4 0.21). Conclusions: Knee flexion moments in the 20s were higher than the moment in the 40s during free gait. Kinematic and kinetic change of the knee joint during gait due to the ages might start on the sagittal plane. Although T2 mapping values at the medial superficial femoral cartilage in the 40s were higher than the values in the 20s, the knee flexion moment is not related to T2 mapping values of knee joint cartilage. We could not conclude that the increased knee flexion moment is the preceding knee kinetic change of the early knee OA from this crosssectional study.

Partitioning of knee joint internal forces in gait is dictated by the knee adduction angle and not by the knee adduction moment

Medial knee osteoarthritis is a debilitating disease. Surgical and conservative interventions are performed to manage its progression via reduction of load on the medial compartment or equivalently its surrogate measure, the external adduction moment. However, some studies have questioned a correlation between the medial load and adduction moment. Using a musculoskeletal model of the lower extremity driven by kinematics–kinetics of asymptomatic subjects at gait midstance, we aim here to quantify the relative effects of changes in the knee adduction angle versus changes in the adduction moment on the joint response and medial/lateral load partitioning. The reference adduction rotation of 1.6° is altered by ±1.5° to 3.1° and 0.1° or the knee reference adduction moment of 17Nm is varied by ±50% to 25.5Nm and 8.5Nm. Quadriceps, hamstrings and tibiofemoral contact forces substantially increased as adduction angle dropped and diminished as it increased. The medial/lateral ratio of contact forces slightly altered by changes in the adduction moment but a larger adduction rotation hugely increased this ratio from 8.8 to a 90 while in contrast a smaller adduction rotation yielded a more uniform distribution. If the aim in an intervention is to diminish the medial contact force and medial/lateral load ratio, a drop of 1.5° in adduction angle is much more effective (causing respectively 12% and 80% decreases) than a reduction of 50% in the adduction moment (causing respectively 4% and 13% decreases). Substantial role of changes in adduction angle is due to the associated alterations in joint nonlinear passive resistance. These findings explain the poor correlation between knee adduction moment and tibiofemoral compartment loading during gait suggesting that the internal load partitioning is dictated by the joint adduction angle.

C209 股関節負荷の小さい歩行動作をコンピュータシミュレーションを用いて求める研究(C2-2 生物工学,動態解析)

C209 股関節負荷の小さい歩行動作をコンピュータシミュレーションを用いて求める研究(C2-2 生物工学,動態解析)

Correlation between EMG-based co-activation measures and medial and lateral compartment loads of the knee during gait

BackgroundInappropriate tibiofemoral joint contact loading during gait is thought to contribute to the development of osteoarthritis. Increased co-activation of agonist/antagonist pair of muscles during gait has commonly been observed in pathological populations and it is thought that this results in increased articular loading and subsequent risk of disease development. However, these hypotheses assume that there is a close relationship between muscle electromyography and force production, which is not necessarily the case. MethodsThis study investigated the relationship between different electromyography-based co-activation measures and articular loading during gait using an electromyography-driven model to estimate joint contact loads. FindingsThe results indicated that significant correlations do exist between selected electromyography-based activity measures and articular loading, but these are inconsistent and relatively low. However despite this, it was found that it may still be possible to use carefully selected measures of muscle activation in conjunction with external adduction moment measures to account for up to 50% of the variance in medial and lateral compartment loads. InterpretationThe inconsistency in correlations between many electromyography-based co-activation measures and articular loading still highlights the danger of inferring joint contact loads during gait using these measures. These results suggest that some form of electromyography-driven modelling is required to estimate joint contact loads in the tibiofemoral joint.

The effects of an adopted narrow gait on the external adduction moment at the knee joint during level walking: Evidence of asymmetry

The external knee adduction moment is an accurate estimation of the load distribution of the knee and is a valid predictor for the presence, severity and progression rate of medial compartment knee osteoarthritis. Gait modification strategies have been shown to be an effective means of reducing the external adduction moment. The purpose of this study was to test narrow gait as a mechanism to reduce the external adduction moment and investigate if limb dominance affects this pattern. Fifteen healthy male participants (mean age: 23.8 (SD=3.1) years, mean height: 1.8 (SD=0.1) m, and mean body mass: 82.9 (SD=16.1kg) took part in this study. Five walking trials were performed for each of the three different gait conditions: normal gait, toe-out gait, and narrow gait. Adoption of the narrow gait strategy significantly reduced the early stance phase external knee adduction moment compared to normal and toe-out gait (p<.002). However, it was observed that this reduction only occurred in the non-dominant limb. Gait modification can reduce the external knee adduction moment. However, asymmetrical patterns between the dominant and non-dominant limbs, specifically during gait modification, may attenuate the effectiveness of this intervention. The mechanism of limb dominance and the specific roles of each limb during gait may account for an asymmetrical pattern in the moment arm and center of mass displacement during stance. This new insight into how limb-dominance effects gait modification strategies will be useful in the clinical setting when identifying appropriate patients, when indicating a gait modification strategy and in future research methodology.

The Transient effects of COX-2 inhibitor on osteogenic differentiation in canine bone marrow-derived mesenchymal stem cells

s / Osteoarthritis and Cartilage 21 (2013) S63–S312 S107 differences were found between limbs for the external sagittal and frontal plane moments at the hip joint, subjects demonstrated greater external adduction moment at the knee of the SX side compared to the NSX side (MD: 0.12 0.11 Nm/Kg, p1⁄4.013, d1⁄41.09). Conclusions: The Hip Harris Score, pain level, and abductor strength suggest that the SX hip is more impaired than the NSX limb. Subjects also ambulate with a compensatory lateral trunk lean toward the affected limb, but continue to demonstrate greater adduction angles on the SX limb during single limb stance. These movement abnormalities may represent the primary movement impairments and may be related to the unilateral hip abductor weakness observed in this sample. Unilateral impairments may also contribute to the significantly larger knee adduction moment on the NSX limb. Figure 1. Average trunk lean angle (A) and hip frontal plane angle (B) during the stance phase of gait for the surgical limb (solid black line) and non-surgical limb (dashed red line). Positive angles represent lean toward the stance leg (A) and adduction (B). Black-striped area represents the standard deviation for the surgical limb. Red-squared area represents the standard deviation for the non-surgical limb. 185 THE TRANSIENT EFFECTS OF COX-2 INHIBITOR ON OSTEOGENIC DIFFERENTIATION IN CANINE BONE MARROW-DERIVED MESENCHYMAL STEM CELLS N. Oh, T. Sunaga, S. Kim, K. Hosoya, M. Okumura. Hokkaido Univ.,

Does hip implant positioning affect the peak external adduction moments of the healthy knees of subjects with total hip replacements?

After unilateral total hip replacement (THR) for hip osteoarthritis (OA), knee OA incidence or progression is common. The contralateral knee is at particular risk, and some have speculated that abnormal THR-hip biomechanics contributes to this asymmetry. We investigated the relationships between operated-hip joint geometry or gait variables and the peak external knee adduction moments-an indicator of knee OA risk-in 21 subjects with unilateral THRs. We found that the peak adduction moment was 14% higher on the contralateral versus the ipsilateral knee (p = 0.131). The best predictors of ipsilateral knee adduction moments were superior-inferior joint center position and operated-hip peak adduction moment (adj R(2) = 0.291, p = 0.017). The sole predictor of the contralateral knee adduction moment was the medial-lateral hip center position (adj R(2) = 0.266, p = 0.010). A postoperative medial shift of the hip center was significantly correlated with a lower postoperative contralateral/ipsilateral knee adduction moment ratio (R = 0.462, p = 0.035). Based on these relationships, we concluded that implant positioning could influence the biomechanical risk of knee OA progression after THR. Although implant positioning decisions are necessarily driven by other factors, it may be appropriate to assess individual THR candidate's knee OA risk and adjust perioperative management accordingly.

Effects of a powered ankle-foot prosthesis on kinetic loading of the unaffected leg during level-ground walking.

BackgroundPeople with a lower-extremity amputation that use conventional passive-elastic ankle-foot prostheses encounter a series of stress-related challenges during walking such as greater forces on their unaffected leg, and may thus be predisposed to secondary musculoskeletal injuries such as chronic joint disorders. Specifically, people with a unilateral transtibial amputation have an increased susceptibility to knee osteoarthritis, especially in their unaffected leg. Previous studies have hypothesized that the development of this disorder is linked to the abnormally high peak knee external adduction moments encountered during walking. An ankle-foot prosthesis that supplies biomimetic power could potentially mitigate the forces and knee adduction moments applied to the unaffected leg of a person with a transtibial amputation, which could, in turn, reduce the risk of knee osteoarthritis. We hypothesized that compared to using a passive-elastic prosthesis, people with a transtibial amputation using a powered ankle-foot prosthesis would have lower peak resultant ground reaction forces, peak external knee adduction moments, and corresponding loading rates applied to their unaffected leg during walking over a wide range of speeds.MethodsWe analyzed ground reaction forces and knee joint kinetics of the unaffected leg of seven participants with a unilateral transtibial amputation and seven age-, height- and weight-matched non-amputees during level-ground walking at 0.75, 1.00, 1.25, 1.50, and 1.75 m/s. Subjects with an amputation walked while using their own passive-elastic prosthesis and a powered ankle-foot prosthesis capable of providing net positive mechanical work and powered ankle plantar flexion during late stance.ResultsUse of the powered prosthesis significantly decreased unaffected leg peak resultant forces by 2-11% at 0.75-1.50 m/s, and first peak knee external adduction moments by 21 and 12% at 1.50 and 1.75 m/s, respectively. Loading rates were not significantly different between prosthetic feet.ConclusionsUse of a biomimetic powered ankle-foot prosthesis decreased peak resultant force at slow and moderate speeds and knee external adduction moment at moderate and fast speeds on the unaffected leg of people with a transtibial amputation during level-ground walking. Thus, use of an ankle-foot prosthesis that provides net positive mechanical work could reduce the risk of comorbidities such as knee osteoarthritis.

Lateral wedges alter mediolateral load distributions at the knee joint in obese individuals

Obesity is the primary risk factor for knee osteoarthritis (OA). Greater external knee adduction moments, surrogate measures for medial compartment loading, are present in Obese individuals and may predispose them to knee OA. Laterally wedged insoles decrease the magnitude of the external adduction moment in Obese individuals but it is unknown how they alter the center of pressure on the tibial plateau. A gait analysis was performed on 14 Obese (avg. 29.3 years; BMI range: 30.3-51.6 kg/m(2) ) and 14 lean women (avg. 26.1 years; BMI range: 20.9-24.6 kg/m(2) ) with and without a full-length, wedged insole. Computed joint angles, joint moments, and knee extensor strength values were input into a musculoskeletal model to estimate center of pressure of the contact force on the tibial plateau. Statistical significance was assessed using a two-way ANOVA to compare the main effects of group and insole condition (α = 0.05). The insole resulted in a significant (p < 0.01) lateral shift in the center of pressure location in both the Obese and Control groups (mean: 2.9 ± 0.7 and 1.5 ± 0.7 mm, respectively). The insole also significantly reduced the peak external knee adduction moment 1.88 ± 1.82 N m in the Control group (p < 0.01) and 3.62 ± 3.90 N m in the Obese group (p < 0.01). The results of this study indicate the effects of a prophylactic wedged insole for reducing the magnitude of the load on the knee's medial compartment in Obese women who are at risk for knee OA development.

Are Mechanics Different between Male and Female Runners with Patellofemoral Pain?

Patellofemoral pain (PFP) has often been attributed to abnormal hip and knee mechanics in females. To date, there have been few investigations of the hip and knee mechanics of males with PFP. The purpose of this study was to compare the lower extremity mechanics and alignment of male runners with PFP with healthy male runners and female runners with PFP. We hypothesized that males with PFP would move with greater varus knee mechanics compared with male controls and compared with females with PFP. Furthermore, it was hypothesized that males with PFP would demonstrate greater varus alignment. A gait and single-leg squat analysis was conducted on each group (18 runners per group). Measurement of each runner's tibial mechanical axis was also recorded. Motion data were processed using Visual 3D (C-Motion, Bethesda, MD). ANOVAs were used to analyze the data. Males with PFP ran and squatted in greater peak knee adduction and demonstrated greater peak knee external adduction moment compared with healthy male controls. In addition, males with PFP ran and squatted with less peak hip adduction and greater peak knee adduction compared with females with PFP. The static measure of mechanical axis of the tibial was not different between groups. However, a post hoc analysis revealed that males with PFP ran with greater peak tibial segmental adduction. Males with PFP demonstrated different mechanics during running and during a single-leg squat compared with females with PFP and with healthy males. Based upon the results of this study, therapies for PFP may need to be sex specific.