The association between tibial torsion, knee flexion excursion and foot progression during gait in people with knee osteoarthritis: a cross-sectional study.

BACKGROUND: Lower limb malalignment is associated with gait kinematics, but there is limited information on the relationship between gait kinematics and tibial torsion in individuals with knee osteoarthritis (OA). This study aimed to investigate possible associations between tibial torsion and early stance kinematics during gait in people with mild and moderate medial knee OA. METHODS: Forty-seven participants (age: 62.1 ± 6.0 years; female/male: 37/10) diagnosed with medial knee OA were recruited from a regional hospital. Thirty of them had mild and seventeen had moderate knee OA. Lower limb alignment including tibial torsion and valgus/varus alignment were assessed by an EOS biplaner X-ray system with participants in weight-bearing position. Lower limb kinematics during gait was captured using the Vicon motion analysis system. The associations were estimated by partial Pearson correlation coefficient test. RESULTS: Our results indicated that external tibial torsion was related to early stance knee flexion excursion in participants with moderate knee OA (r = -0.58, p = 0.048), but not in participants with mild knee OA (r = 0.34, p = 0.102). External tibial torsion was associated with external foot progression angle (r = 0.48, p = 0.001), and knee varus/valgus alignment was associated with knee flexion excursion (r = -0.39, p = 0.010) in all participants. CONCLUSIONS: Both horizontal and frontal lower limb alignments were associated with knee flexion excursion at early stance of gait cycle in participants with medial knee OA. The distal rotational profile of lower limb would likely affect knee motion in sagittal plane. It implies that people with moderate knee OA could possibly benefit from correction of rotational alignment of lower limb.

Finite Element Analysis of Generalized Ligament Laxity on the Deterioration of Hallux Valgus Deformity (Bunion).

Hallux valgus is a common foot problem affecting nearly one in every four adults. Generalized ligament laxity was proposed as the intrinsic cause or risk factor toward the development of the deformity which was difficult to be investigated by cohort clinical trials. Herein, we aimed to evaluate the isolated influence of generalized ligament laxity on the deterioration using computer simulation (finite element analysis). We reconstructed a computational foot model from a mild hallux valgus participant and conducted a gait analysis to drive the simulation of walking. Through parametric analysis, the stiffness of the ligaments was impoverished at different degrees to resemble different levels of generalized ligament laxity. Our simulation study reported that generalized ligament laxity deteriorated hallux valgus by impairing the load-bearing capacity of the first metatarsal, inducing higher deforming force, moment and malalignment at the first metatarsophalangeal joint. Besides, the deforming moment formed a deteriorating vicious cycle between hallux valgus and forefoot abduction and may result in secondary foot problems, such as flatfoot. However, the metatarsocuneiform joint did not show a worsening trend possibly due to the overriding forefoot abduction. Controlling the deforming load shall be prioritized over the correction of angles to mitigate deterioration or recurrence after surgery.

Shoe collar height and heel counter-stiffness for shoe cushioning and joint stability in landing.

This study examined the effects of shoe collar-height and counter-stiffness on ground reaction force (GRF), ankle and knee mechanics in landing. Eighteen university basketball players performed drop landing when wearing shoes in different collar height (high vs. low) and counter-stiffness (stiffer vs. less stiff). Biomechanical variables were measured with force platform and motion capturing systems. Two-way repeated measures ANOVA was performed with α = 0.05. Wearing high collar shoes exhibited smaller peak ankle dorsiflexion and total sagittal RoM, peak knee extension moment, but larger peak knee varus moment than the low collar shoes. Stiffer counter-stiffness shoes related to smaller ankle inversion at touchdown and total coronal RoM, but larger peak knee flexion and increased total ankle and knee sagittal RoM than the less stiff counter-stiffness. Furthermore, wearing stiffer counter-stiffness shoes increased forefoot GRF peak at high collar condition, while no significant differences between counter-stiffness at low collar condition. These results suggest that although higher collar height and/or stiffness heel counter used can reduce ankle motion in coronal plane, it would increase the motion and loading at knee joint, which is susceptible to knee injuries. These findings could be insightful for training and footwear development in basketball.

Analysis of compression/release stabilized transfemoral prosthetic socket by finite element modelling method.

The aim of this study was to investigate the residual limb stress of a transfemoral amputee's Compression/Release Stabilized (CRS) socket by finite elemental modelling. The model was constructed from magnetic resonance images of the left residual limb of a 48-year-old male transfemoral amputee. Two conditions were simulated. In the donning condition, the prosthetic socket under the residual limb moved proximally until it reached the required donned position. The weight-bearing condition was subsequently simulated by applying body weight (800N) at the femoral head while keeping the distal end of the socket fixed. The maximum contact pressure was concentrated at the proximal anterior-medial regions of the residual limb surfaces in both conditions. In the donning condition, the maximum von Mises stress and the maximum contact pressure were 277.7 kPa and 254 kPa respectively. The respective values were 191.9 kPa and 218.5 kPa when body weight was applied. The stress and contact pressure did not exceed the suggested threshold value of pain. Our findings provide important biomechanical information on the CRS socket that may help future design optimization.

Effect of Red Arch-Support Insoles on Subjective Comfort and Movement Biomechanics in Various Landing Heights.

Red is perceived as a "winning color", which may influence actual and perceived performances in sports, but little effort has been done to assess the added value on colored foot insoles in basketball movements. This study examined if colored foot insole would influence perceived comfort and lower extremity biomechanics during drop landing. Nineteen male basketball players performed drop landing trials with different insoles (red arch-support, white arch-support, and white-flat) and landing heights (0.45 and 0.61 m). Two-way (Insole x Height) ANOVAs with repeated measures were performed on each of the knee and ankle angles and moments variables. Wearing red arch-support insoles induced better perception of forefoot and rearfoot cushioning and overall comfort but smaller plantarflexion moment than the white-flat insoles (p < 0.05). Increased landing height was related to higher ground reaction loading, sagittal flexion angles, range of motion, and joint moments but smaller ankle eversion (p < 0.05). Findings indicate that foot insoles might have influenced comfort perception and joint kinetics, but not joint kinematics. The use of red color in foot insoles could potentially maximize the effectiveness of foot insoles in a way that alters comfort perception and motor control during landing, with implications for risk of injury.

Effects of arch-support orthoses on ground reaction forces and lower extremity kinematics related to running at various inclinations.

While foot orthoses are commonly used in running, little is known regarding biomechanical risk potentials during uphill running. This study investigated the effects of arch-support orthoses on kinetic and kinematic variables when running at different inclinations. Sixteen male participants ran at different inclinations (0°, 3° and 6°) when wearing arch-support and flat orthoses on an instrumented treadmill. Arch-support orthoses induced longer contact time, larger initial ankle dorsiflexion, maximum ankle eversion, and knee sagittal range of motion (RoM) (p < 0.05). As incline slopes increased, vertical impact peak and loading rate, stride length, and ankle coronal RoM decreased, but contact time, stride frequency, initial ankle dorsiflexion and inversion, maximum dorsiflexion, initial knee flexion, and ankle sagittal RoM increased (p < 0.05). Furthermore, knee sagittal RoM was lowest when running at an inclination of 3°. The interaction effect indicated that in arch-support condition, participants running at 6° induced higher maximum ankle eversion than running at 0° (p < 0.05), while no differences were found in flat orthosis condition. These findings suggest that the use of arch-support orthoses would influence running biomechanics that is related to injury risks. Running at higher inclination led to more alterations to biomechanical variables than at lower inclination.

Finite element simulation on posterior tibial tendinopathy: Load transfer alteration and implications to the onset of pes planus.

BACKGROUND: Posterior tibial tendinopathy is a challenging foot condition resulting in pes planus, which is difficult to diagnose in the early stage. Prior to the deformity, abnormal internal load transfer and soft tissue attenuation are anticipated. The objective of this study was to investigate the internal load transfer and strain of the ligaments with posterior tibial tendinopathy, and the implications to pes planus and other deformities. METHODS: A three-dimensional finite element model of the foot and ankle was reconstructed from magnetic resonance images of a 28-year-old normal female. Thirty bones, plantar fascia, ligaments and tendons were reconstructed. With the gait analysis data of the model subject, walking stance was simulated. The onset of posterior tibial tendinopathy was resembled by unloading the tibialis posterior and compared to the normal condition. FINDINGS: The load transfer of the joints at the proximal medial column was weaken by posterior tibial tendinopathy, which was compromised by the increase along the lateral column and the intercuneiforms during late stance. Besides, the plantar tarsometatarsal and cuboideonavicular ligaments were consistently over-stretched during stance. Particularly, the maximum tensile strain of the plantar tarsometatarsal ligament was about 3-fold higher than normal at initial push-off. INTERPRETATION: Posterior tibial tendinopathy altered load transfer of the medial column and unbalanced the load between the proximal and distal side of the medial longitudinal arch. Posterior tibial tendinopathy also stretched the midfoot plantar ligaments that jeopardized midfoot stability, and attenuated the transverse arch. All these factors potentially contributed to the progress of pes planus and other foot deformities.

Biomechanical consequences of subtalar joint arthroereisis in treating posterior tibial tendon dysfunction: a theoretical analysis using finite element analysis.

Subtalar joint arthroereisis (SJA) has been introduced to control the hyperpronation in cases of flatfoot. The objective of this study is to evaluate the biomechanical consequence of SJA to restore the internal stress and load transfer to the intact state from the attenuated biomechanical condition induced by posterior tibial tendon dysfunction (PTTD). A three-dimensional finite element model of the foot and ankle complex was constructed based on clinical images of a healthy female (age 28 years, height 165 cm, body mass 54 kg). The boundary and loading condition during walking was acquired from the gait experiment of the model subject. Five sets of simulations (conditions) were completed: intact condition, mild PTTD, severe PTTD, mild PTTD with SJA, severe PTTD with SJA. The maximum von Mises stress of the metatarsal shafts and the load transfer along the midfoot during stance were analyzed. Generally, SJA deteriorated the joint force of the medial cuneonavicular and calcaneocuboid joints during late stance, while that of the metatarsocuneiform joints during early stance were over-corrected. Only the calcaneocuboid joint force at 45% stance demonstrated a trend of improvement. Besides, SJA exaggerated the increased stress of the metatarsals compared to the PTTD conditions, except that of the first metatarsal. Our study did not support the hypothesis that SJA can restore the internal load transfer and midfoot stress. SJA cannot compensate the salvage of midfoot stability attributed by PTTD and could be biomechanically insufficient to restore the biomechanical environment. Additional procedures such as orthotic intervention may be necessary.

Is passive metatarsophalangeal joint stiffness related to leg stiffness, vertical stiffness and running economy during sub-maximal running?

This study examined whether passive metatarsophalangeal joints (MPJ) stiffness was associated with leg stiffness (Kleg) vertical stiffness (Kvert) and running economy (RE) during sub-maximal running. Nine male experienced runners underwent passive MPJ stiffness measurements in standing and sitting positions followed by sub-maximal running on an instrumented treadmill. With the individual foot position properly aligned, the MPJ passive stiffness in both sitting (MPJsit) and standing positions (MPJstand) were measured with a computerized dynamometer. Data were collected at a running speed of 2.78m/s, representing a stabilized level of energy expenditure. Pedar pressure insole was used to determine the contact time (tc) and peak reaction force for the calculation of Kleg and Kvert. A respiratory gas analysis system was used to estimate the RE. Bivariate correlation test was performed to examine the correlation among MPJ stiffness, contact time, Kleg, Kvert, and RE. The results showed that MPJsit and MPJstand were inversely correlated with RE (p=0.04, r=-0.68 to -0.69), suggesting that stiffer MPJ improves RE. In addition, MPJsit was correlated positively with Kleg (p<0.01, r=0.87),Kvert (p=0.03, r=0.70) but inversely with tc (p=0.02, r=-0.76), while MPJstand was correlated positively with the Kvert (p=0.02, r=0.77). These findings suggested that strength of toe plantar flexors provides stability and agility in the stance phase for more effective and faster forward movement.

Reliability of metatarsophalangeal and ankle joint torque measurements by an innovative device.

The toe flexor muscles maintain body balance during standing and provide push-off force during walking, running, and jumping. Additionally, they are important contributing structures to maintain normal foot function. Thus, weakness of these muscles may cause poor balance, inefficient locomotion and foot deformities. The quantification of metatarsophalangeal joint (MPJ) stiffness is valuable as it is considered as a confounding factor in toe flexor muscles function. MPJ and ankle joint stiffness measurement is still largely depended on manual skills as current devices do not have good control on alignment, angular joint speed and displacement during measurement. Therefore, this study introduces an innovative dynamometer and protocol procedures for MPJ and ankle Joint torque measurement with precise and reliable foot alignment, angular joint speed and displacement control. Within-day and between-day test-retest experiments on MPJ and ankle joint torque measurement were conducted on ten and nine healthy male subjects respectively. The mean peak torques of MPJ and ankle joint of between-day and within-day measurement were 1.50±0.38Nm/deg and 1.19±0.34Nm/deg. The corresponding torques of the ankle joint were 8.24±2.20Nm/deg and 7.90±3.18Nm/deg respectively. Intraclass-correlation coefficients (ICC) of averaged peak torque of both joints of between-day and within-day test-retest experiments were ranging from 0.91 to 0.96, indicating the innovative device is systematic and reliable for the measurements and can be used for multiple scientific and clinical purposes.

Biomechanics of first ray hypermobility: an investigation on joint force during walking using finite element analysis.

Hypermobility of the first ray is suggested to contribute to hallux valgus. The investigation of first ray hypermobility focused on the mobility and range of motion that based on manual examination. The load transfer mechanism of the first ray is important to understand the development and pathomechanism of hallux valgus. In this study, we investigated the immediate effect of the joint hypermobility on the metatarsocuneiform and metatarsophalangeal joint loading through a reduction of the stiffness of the foot ligaments. A three-dimensional foot model was constructed from a female aged 28 via MRI. All foot and ankle bones, including two sesamoids and the encapsulated bulk tissue were modeled as 3D solid parts, linking with ligaments of shell elements and muscles connectors. The stance phase of walking was simulated by the boundary and loading conditions obtained from gait analysis of the same subject. Compared with the normal foot, the hypermobile foot had higher resultant metatarsocuneiform and metatarsophalangeal joint forces. The increases accounted for 18.6% and 3.9% body weight. There was also an abrupt change of metatarsocuneiform joint force in the medial-lateral direction. The predicted results represented possible risk of joint problems and metatarsus primus varus.

Development of a finite element model of female foot for high-heeled shoe design.

BACKGROUND: Wearing high-heeled shoes may produce deleterious effects on the musculoskeletal system while elevation of the shoe heel with arch insole insert is used as a treatment strategy for plantar fasciitis. Due to limitations of the experimental approaches, direct measurements of internal stress/strain of the foot are impossible or invasive. This study aims at developing a finite element model for evaluating the biomechanical effects of high-heeled support on the ankle-foot complex. METHODS: A 3D anatomically detailed FE model of the female foot and ankle together with a high-heeled support was developed and used to investigate the plantar contact pressure and internal loading responses of the bony and soft tissue structures of the foot with varying heel heights during simulated balanced standing. FINDINGS: In the balanced standing position with high-heeled support, a pronounced increase in von Mises stress at the first metatarsophalangeal (MTP) joint was predicted. The strain on plantar fascia decreased compared to the flat horizontal support and valgus deformity of the hallux was not significant. INTERPRETATION: The increased stress in forefoot especially at the first MTP segment during prolonged high-heeled standing may contribute to progressive hallux valgus (HV) deformity. However, the reduced tensile strain in the plantar fascia with heel elevation may help relieve plantar fasciitis related pain and inflammation.

Three-dimensional finite element analysis of the foot during standing--a material sensitivity study.

Information on the internal stresses/strains in the human foot and the pressure distribution at the plantar support interface under loading is useful in enhancing knowledge on the biomechanics of the ankle-foot complex. While techniques for plantar pressure measurements are well established, direct measurement of the internal stresses/strains is difficult. A three-dimensional (3D) finite element model of the human foot and ankle was developed using the actual geometry of the foot skeleton and soft tissues, which were obtained from 3D reconstruction of MR images. Except the phalanges that were fused, the interaction among the metatarsals, cuneiforms, cuboid, navicular, talus, calcaneus, tibia and fibula were defined as contact surfaces, which allow relative articulating movement. The plantar fascia and 72 major ligaments were simulated using tension-only truss elements by connecting the corresponding attachment points on the bone surfaces. The bony and ligamentous structures were embedded in a volume of soft tissues. The encapsulated soft tissue was defined as hyperelastic, while the bony and ligamentous structures were assumed to be linearly elastic. The effects of soft tissue stiffening on the stress distribution of the plantar surface and bony structures during balanced standing were investigated. Increases of soft tissue stiffness from 2 and up to 5 times the normal values were used to approximate the pathologically stiffened tissue behaviour with increasing stages of diabetic neuropathy. The results showed that a five-fold increase in soft tissue stiffness led to about 35% and 33% increase in the peak plantar pressure at the forefoot and rearfoot regions, respectively. This corresponded to about 47% decrease in the total contact area between the plantar foot and the horizontal support surface. Peak bone stress was found at the third metatarsal in all calculated cases with a minimal increase of about 7% with soft tissue stiffening.