Site dependent elastic property of human iliotibial band and the effect of hip and knee joint angle configuration

Time-dependent effects of ethanol-glycerin embalming on iliotibial band biomechanics

When conducting biomechanical testing or clinical training using embalmed human soft tissues, it is essential to understand their impact on biomechanical properties and their time dependence. Previous studies have investigated this influence, but specific variations over different embalming durations have not been thoroughly addressed to date. Ninety-seven human iliotibial band specimens were obtained from nine donors. All specimens were embalmed in ethanol-glycerin for varying durations: one day, eight days, and fourteen days. Prior to the mechanical trials, the specimens underwent osmotic water adjustment, tapering and standardized clamping. Uniaxial tensile tests were conducted to determine elastic modulus, ultimate tensile strength, and ultimate strain. Surface strain measurements were performed using a digital image correlation system. Ethanol-glycerin embalming of soft tissues significantly affects ultimate strain after one day of submersion time, elastic modulus after eight days, and the ultimate tensile strength after fourteen days. For applications requiring consistent and reliable material properties reflecting a (supra-)vital state, caution is advised against using embalmed tissues even following short submersion durations in ethanol-glycerin.

Design, implementation and effectiveness of human fascia lata biomechanics for tissue engineering

The fascia lata (FL) is a multi-layered connective tissue with anisotropic mechanical behavior due to its fiber organization. It plays a key role in musculoskeletal functionality, making it important in tissue engineering. Understanding its mechanical response to stimuli like movement or applied pressure is crucial, as the elastic and viscoelastic behavior can vary significantly based on morphological characteristics, harvesting site, and load direction. Thus, the aim of this review is to summarise through a gap analysis the scientific literature on the biomechanical properties of the human FL, identifying all those features (from the experimental set up to its inherent structural variability) that could affect its biomechanical behaviour, and thus unveiling these emerging correlations. Our research reported key mechanical properties of the FL, such as Young's modulus, Ultimate Tensile Strength, failure strain, and anisotropic response, which are crucial for designing and applying obtained allografts and autografts in soft tissue repair. These insights can help surgeons optimize graft applications-selecting the proper harvesting location, technique, graft type, and suture size-and guide clinicians in rehabilitation for personalized medicine.

What mechanical and proprioceptive structures are involved in quadriceps stretching? Why is it important for patella travel?

OBJECTIVE

Ely's, Ober's, and modified Thomas' tests are widely used. Stretching the front thigh involves two layers of tissue: the rectus femoris and its overlying fascia lata (FL). However, to our knowledge, no biomechanical study has analyzed these tests. Therefore, this study tries to determine the structures affected during the stretching of the front thigh.

METHODS

An observational study of the front thigh was conducted. The directions and intensities of the reaction forces were recorded. The patellar travel was used to determine the average coordinates of the stretched structures at hip level in the horizontal plane. The participants indicated the stretched area. The stretch of a patient with a complete tear of his left rectus femoris was recorded.

RESULTS

The reaction force of the thigh was oriented at 33° (standard deviation [SD]: 6°) sideways and its intensity was 60 N m (SD: 19 N m). The centroid coordinates of all stretched structures were stable. The registered average external rotational torque of 6 N m (SD: 3.7 N m) could only be mediated by the FL. The stretched area indicated by the participants could be anywhere on the FL. The tolerated reaction force increased in the same way on the disinserted rectus femoris thigh and on the uninjured thigh.

CONCLUSION

Ober's, Modified Thomas', and Ely's tests are three potential means of assessing FL extensibility. A lateral patellar tilt may be triggered by the FL's reaction force to stretching. Stretch tolerance seems to be limited by the FL, the fascia profundis of the thigh.

Hot-pack therapy increased gliding function of the iliotibial band during passive knee motion: An exploratory study

INTRODUCTION

Quantifying soft tissue dynamics during joint motion is important for the valid assessment and development of effective therapeutic interventions for the soft tissues. This study aimed to examine the immediate effect of thermotherapy on gliding of the iliotibial band (ITB), including the subcutaneous tissue, and vastus lateralis (VL) muscle during passive knee joint motion.

METHODS

Ten participants (age, 20.4 ± 0.7 years; height, 172.0 ± 8.9 cm; weight, 64.1 ± 9.7 kg; BMI, 21.6 ± 1.7 kg/m2) with no history of lower extremity surgery or neuromuscular disease participated in the study. An electrothermal hot pack with an internal temperature of 65 °C was applied to one of the lateral thighs, followed by measuring its stiffness using a durometer. Movements of both the ITB and VL were recorded using ultrasound imaging during isokinetic knee motion. The Farneback method and optical flow algorithm analysis software were adapted to create the movement velocity from ultrasound imaging. Gliding coefficient was calculated using the coefficient of correlation for each velocity in the proximal-distal direction during knee motion. The mean velocity during knee motion was calculated using absolute values. The differences between the pre-intervention values and between the pre- and post-intervention values were examined.

RESULTS

After applying the hot pack, the stiffness significantly decreased (p = 0.01), and the mean velocity of the ITB significantly increased (p = 0.03). The gliding coefficient and VL mean velocity did not significant differ (p = 0.65 and p = 0.80, respectively) between pre- and post-hot-pack applications.

CONCLUSIONS

Hot-pack therapy might increase gliding function of the ITB during passive knee motion.

Biomechanical assessment of gastrocnemii and Achilles tendon using MyotonPRO: in vivo measurements, and preliminary in situ measurements using formalin-fixed tissues

PURPOSE

This study aims to evaluate the reliability and validity of using MyotonPRO to quantify the mechanical properties of the muscle-tendon unit through in vivo measurements and preliminary in situ measurements using formalin-fixed tissues.

MATERIALS AND METHODS

The mechanical properties of gastrocnemii and the Achilles tendon of 12 healthy adults (six males and six females, 34.9 ± 5.8 years) were examined for in vivo test twice within a day and once post-24 hours using MyotonPRO, while nine human cadavers (formalin-fixed, 3 males and 6 females, 89.9 ± 5.1 years) were assessed for preliminary in situ test with identical time schedule to evaluate the within-day and inter-day reliability and validity.

RESULTS

In vivo tests had very high within-day (ICC: 0.96-0.99) and inter-day reliability (ICC: 0.83-0.96), while in situ tests (formalin-fixed tissues) showed high within-day (ICC: 0.87-0.99) and inter-day reliability (ICC: 0.76-0.98) for the results of tone and stiffness. There was no significant difference in the stiffness of the free part of the Achilles tendon between in vivo and in situ conditions. The stiffness of the lateral gastrocnemius (r = 0.55, p = 0.018), proximal part of the Achilles tendon (r = 0.56, p = 0.015), and free part of the Achilles tendon (r = 0.47, p = 0.048) before removing the skin was significantly correlated with that after removing the skin condition.

CONCLUSIONS

The findings of the current study suggest that MyotonPRO is reliable and valid for evaluating tendon stiffness both in vivo and in situ (formalin-fixed tissues).

Experimental Ultrasound Approach for Studying Knee Intra-Articular Femur-Tibia Movements under Different Loads

The purpose of the present study was to develop an experimental model for the study of intra-articular knee movements depending on the function of the knee joint and involved muscle groups under isometric stretching conditions with different loads. The experimental procedure included an ultrasound examination of a knee joint after isometric stretching in healthy men (n = 32). The changes (in millimeters) in the distances between the femur and tibia were measured using an ultrasound sonographer at three stages. The first stage was performed on ten (n = 10) healthy men in five different sitting and upright positions. In the second and third experimental model stages, lower limbs loading was applied to 22 participants. Our hypothesis, which was confirmed, was that as a result of increased loads on the participant's back, an intra-articular decrease in the femur-tibia cartilage surface distance would be observed. The accuracy of the created experimental model was improved over its three stages from 30% to 9%. Quantitative model data can help to create a mathematical model of the mechanical effects during the deformation of knee joint bone cartilage and it can also help outline some future tasks: increasing loading weights, enlarging participant groups, performing comparisons of men and women, and performing comparisons of healthy and pathological individuals.

Stretch tolerance and elastic passive reaction of the quadriceps femoris seem to depend more on the fascia profundis taut surfaces than on the underlying stretched muscle

The rectus femoris and its covering, the fascia lata (i.e., fascia profundis), are two anatomical structures involved in anterior thigh stretching. This study aimed to identify the role of strain changes in the fascia lata in limiting stretch tolerance. The reaction force intensity of 11 men and 5 women was assessed during passive stretching of the anterior thigh at 130, 110, 90, and 70° of knee flexion. Recent data suggest that the fascia lata strain field is modified with knee flexion. Therefore, the relationship between knee flexion angle and stretch tolerance was assessed. We found that the reaction force of the anterior thigh increased almost linearly with the degree of knee extension between 130° and 70°. The fascia lata stretched surface proprioceptive information seems responsible for stretch tolerance. Fascia profundis strain field must be considered during stretching experiments.

Mechanical Characterization of Human Fascia Lata: Uniaxial Tensile Tests from Fresh-Frozen Cadaver Samples and Constitutive Modelling

Human Fascia Lata (FL) is a connective tissue with a multilayered organization also known as aponeurotic fascia. FL biomechanics is influenced by its composite structure formed by fibrous layers (usually two) separated by loose connective tissue. In each layer, most of the collagen fibers run parallel in a distinct direction (with an interlayer angle that usually ranges from 75-80°), mirroring the fascia's ability to adapt and withstand specific tensile loads. Although FL is a key structure in several musculoskeletal dysfunctions and in tissue engineering, literature still lacks the evidence that proves tissue anisotropy according to predominant collagen fiber directions. For this purpose, this work aims to analyze the biomechanical properties of ex-vivo FL (collected from fresh-frozen human donors) by performing uniaxial tensile tests in order to highlight any differences with respect to loading directions. The experimental outcomes showed a strong anisotropic behavior in accordance with principal collagen fibers directions, which characterize the composite structure. These findings have been implemented to propose a first constitutive model able to mimic the intra- and interlayer interactions. Both approaches could potentially support surgeons in daily practices (such as graft preparation and placement), engineers during in silico simulation, and physiotherapists during musculoskeletal rehabilitation, to customize a medical intervention based on each specific patient and clinical condition.

Properties of the iliotibial band and their relationships with gait parameters among patients with knee osteoarthritis

This study aimed to determine the thickness and stiffness of the iliotibial band (ITB) in patients with knee osteoarthritis (KOA) and to identify the gait parameters that are associated with ITB properties. Eighteen female patients with radiographically diagnosed medial KOA and knee pain (age: 69.7 ± 5.9 years, body mass index: 23.0 ± 3.1 kg/m² ) and 22 age-matched female individuals without knee pain (age: 69.1 ± 7.0 years, body mass index: 21.6 ± 3.6 kg/m² ) were included. Shear wave elastography images were obtained at the height of the proximal pole of the patella with the participants in the supine position, and the ITB thickness and shear wave velocity, which is a surrogate measure of stiffness, were calculated. In patients with KOA, the knee and hip joint angles and moments during walking were calculated using a motion analysis system. The shear wave velocity was significantly higher in patients with KOA than in asymptomatic adults (11.3 ± 1.0 vs. 10.0 ± 1.8 m/s, respectively; p = 0.010); however, the thickness did not differ between them (2.1 ± 0.3 vs. 2.0 ± 0.3 mm, respectively; p = 0.705). The time-integral value of the knee adduction moment (β = 0.507, p = 0.032) and maximum value of the hip flexion moment (β = 0.498, p = 0.036) were associated with the shear wave velocity. Meanwhile, no parameters were associated with the thickness. The ITB was stiffer in patients with KOA than in asymptomatic adults; such a stiffer ITB was associated with greater knee adduction and hip flexion moments during walking. Clinical Significance: Greater mechanical loading was associated with a stiffer ITB in patients with KOA.

Error analysis and reliability of zero-order Lamb mode inversion for waveguide characterization

In recent years, several fitting techniques have been presented to reconstruct the parameters of a plate from its Lamb wave dispersion curves. Published studies show that these techniques can yield high accuracy results and have the potential of reconstructing several parameters at once. The precision with which parameters can be reconstructed by inverting Lamb wave dispersion curves, however, remains an open question of fundamental importance to many applications. In this work, we introduce a method of analyzing dispersion curves that yields quantitative information on the precision with which the parameters can be extracted. In our method, rather than employing error minimization algorithms, we compare a target dispersion curve to a database of theoretical ones that covers a given parameter space. By calculating a measure of dissimilarity (error) for every point in the parameter space, we reconstruct the distribution of the error in that space, beside the location of its minimum. We then introduce dimensionless quantities that describe the distribution of this error, thus yielding information about the spread of similar curves in the parameter space. We demonstrate our approach by considering both idealized and realistic scenarios, analyzing the dispersion curves obtained numerically for a plate and experimentally for a pipe. Our results show that the precision with which each parameter is reconstructed depends on the mode used, as well as the frequency range in which it is considered.

Efficacy of urea solution reperfusion to a formalin-embalmed cadaver for surgical skills training

Formaldehyde has been traditionally used for embalming human cadavers for gross anatomy education and surgical skills training. However, exposure to formaldehyde negatively affects human health. This study aimed to assess the efficacy of reperfusing urea solution to a formalin-embalmed cadaver for surgical skills training and then investigate the cadaver's tissue elasticity alteration after being soaked into the urea solution. Twelve surgeons evaluated the similarity of tissue characteristics between the cadaver (embalmed by formalin solution and reperfused by urea solution) and a living human body. Furthermore, the tissue formaldehyde content and mechanical properties of the formalin-fixated femoral skin and artery specimens with or without soaking into urea solution were measured. Results showed that the tactile assessment, skin incision, vessel ligation and suture, and decollement were better and more useful in the cadaver reperfused by urea solution than in the cadaver merely fixated by formalin solution. In the urea-reperfused cadaver, the volatilized, or tissue formaldehyde levels declined. The stiffness and Young's modulus of the femoral skin and artery were also lower in the specimen than in the mere formalin-fixated specimen. In conclusion, reperfusion of urea solution to the formalin-fixated cadaver makes anatomical education and surgical skills training more efficient with fewer requirements for cadaver management.

Distinct displacement of the superficial and deep fascial layers of the iliotibial band during a weight shift task in runners: An exploratory study

Motion of the fascial layers of the iliotibial band (ITB), as a reinforcement of the deep fascia lata, is likely to be relevant for its function and mechanical behaviour. This exploratory study aimed to evaluate the ITB fascial layers displacement during a weight shift task. Thirteen pain-free runners performed a 6-second standing weight shift task. B-mode ultrasound imaging using an automated fascicle tracking algorithm was used to measure proximal and distal displacement of superficial and deep ITB layers at the middle region. To study the potential contributors to individual variation of fascial motion, we recorded the activity of five hip/thigh muscles with electromyography (EMG), thigh/pelvis/trunk position with accelerometers, and centre of pressure with a force plate. Linear regressions estimated the relationship between displacement of fascial layers and hip/trunk angles. Independent t-tests or Fisher's exact tests compared EMG and movement-related parameters between participants who demonstrated motion of the fascia in the proximal and distal directions. Thickness of the ITB and the loose connective tissue between its layers were calculated. Proximal displacement was observed in six (-4.1 ± 1.9 mm [superficial]) and two (-6.2 ± 2.0 mm [deep]) participants. Distal displacement was observed for seven participants for each layer (3.1 ± 1.1 mm [superficial]; 3.6 ± 1.3 mm [deep]). Four participants did not show displacement of the deep layer. Trunk lateral flexion and gluteus medius muscle activity were determinants of proximal motion of the superficial layer. Loose connective tissue was thinner in participants without displacement of the deep layer. Displacement of the ITB fascial layers varies between individuals. Variation related to differences in joint movements and muscle activity. This study highlights the complex interaction between fascia and movement.

Conservative treatment of iliotibial band syndrome in runners: Are we targeting the right goals?

OBJECTIVE

Iliotibial band syndrome (ITBS) is presumably caused by excessive tension in the iliotibial band (ITB) leading to compression and inflammation of tissues lying beneath it. Usually managed conservatively, there is a lack of scientific evidence supporting the treatment recommendations, and high symptom recurrence rates cast doubt on their causal effectiveness. This review discusses the influence of common physiotherapeutic measures on risk factors contributing to tissue compression beneath the ITB.

METHODS

The potential pathogenic factors are presented on the basis of a simple biomechanical model showing the forces acting on the lateral aspect of the knee. Existent literature on the most commonly prescribed physiotherapeutic interventions is critically discussed against the background of this model. Practical recommendations for the optimization of physiotherapy are derived.

RESULTS

According to biomechanical considerations, ITBS may be promoted by anatomical predisposition, joint malalignments, aberrant activation of inserting muscles as well as excessive ITB stiffness. Hip abductor strengthening may correct excessive hip adduction but also increase ITB strain. Intermittent stretching interventions are unlikely to change the ITB's length or mechanical properties. Running retraining is a promising yet understudied intervention.

CONCLUSIONS

High-quality research directly testing different physiotherapeutic treatment approaches in randomized controlled trials is needed.