Hip Muscle Forces Research Articles

Hip loads and muscle forces in at-risk and established hip osteoarthritis

Hip loads and muscle forces in at-risk and established hip osteoarthritis

Stabilometry in Relation to Hip and Knee Muscle Force in Children with Surgically Treated Unilateral Slipped Capital Femoral Epiphysis.

The main aim of our study was to analyze the stabilometric parameters in relation to hip and knee muscle force in children with unilateral slipped capital femoral epiphysis (SCFE) who had undergone surgical treatment. Another objective was to compare the stabilometry in three testing situations (eyes open, eyes closed, and head retroflexed). In total, 26 patients with unilateral right SCFE treated via in situ fixation with one percutaneous screw performed stabilometry assessments under three different situations (with their eyes open, with their eyes closed, and with their head retroflexed) and isometric muscle force assessment of the bilateral hip flexors, extensors, abductors and adductors and bilateral knee flexors and extensors. No significant differences between the right side (affected hip) and left side (non-affected hip) were recorded for all of the tested muscle groups. We found significant negative correlations between the 90% confidence ellipse area (eyes open condition) and left knee extensors (p = 0.028), right knee flexors (p = 0.041), and left knee flexors (p = 0.02), respectively. When performing the comparison between the eyes open and eyes closed situations, there were significant differences in CoP path length (p < 0.0001) and maximum CoP speed (p = 0.048); the parameters increased in the eyes closed situation. Better postural stability is acquired when assessed with eyes open or with the head retroflexed in contrast with eyes closed testing.

Musculoskeletal models determine the effect of a soft active exosuit on muscle activations and forces during lifting and lowering tasks

Exosuits have the potential to mitigate musculoskeletal stress and prevent back injuries during industrial tasks. This study aimed to 1) validate the implementation of a soft active exosuit into a musculoskeletal model of the spine by comparing model predicted muscle activations versus corresponding surface EMG measurements, and 2) evaluate the effect of the exosuit on peak back and hip muscle forces. Fourteen healthy participants performed squat and stoop lift and lower tasks with boxes of 6 and 10 kg, with and without wearing a 2.7 kg soft active exosuit. Participant-specific musculoskeletal models, which included the exosuit, were created in OpenSim. Model validation focused on the back and hip extensors, where temporal agreement between EMG and model estimated muscle activity was generally strong to excellent (average cross-correlation coefficients ranging from 0.84 to 0.98). Root mean square errors of muscle activity (0.05–0.10) were similar with and without the exosuit, and compared well to prior model validation studies without the exosuit (average root mean square errors ranging from 0.05 to 0.19). In terms of performance, the exosuit reduced the estimated peak erector spinae forces during lifting and lowering phases across all lifting tasks but reduced peak hip extensor muscles forces only in a squat lift task of 10 kg. These reductions in total peak muscle forces were approximately 1.7–4.2 times greater than the corresponding exosuit assistance force, which were 146 ± 19 N and 102 ± 14 N at the times of peak erector spinae forces in lifting and lowering, respectively. Overall, the results support the hypothesis that exosuits reduce soft tissue loading, and thereby potentially reduce fatigue and injury risk during manual materials handling tasks. Incorporating exosuits into musculoskeletal models is a valid approach to understand the impact of exosuit assistance on muscle activity and forces.

Psoas force recruitment in full-body musculoskeletal movement simulations is restored with a geometrically informed cost function weighting

Simulations of musculoskeletal models are useful for estimating internal muscle and joint forces. However, predicted forces rely on optimization and modeling formulations. Geometric detail is important to predict muscle forces, and greater geometric complexity is required for muscles that have broad attachments or span many joints, as in the torso. However, the extent to which optimized muscle force recruitment is sensitive to these geometry choices is unclear. We developed level, uphill and downhill sloped walking simulations using a standard (uniformly weighted, “fatigue-like”) cost function with lower limb and full-body musculoskeletal models to evaluate hip muscle recruitment with different geometric representations of the psoas muscle under walking conditions with varying hip moment demands. We also tested a novel cost function formulation where muscle activations were weighted according to the modeled geometric detail in the full-body model. Total psoas force was less and iliacus, rectus femoris, and other hip flexors’ force was greater when psoas was modeled with greater geometric detail compared to other hip muscles for all slopes. The proposed weighting scheme restored hip muscle force recruitment without sacrificing detailed psoas geometry. In addition, we found that lumbar, but not hip, joint contact forces were influenced by psoas force recruitment. Our results demonstrate that static optimization dependent simulations using models comprised of muscles with different amounts of geometric detail bias force recruitment toward muscles with less geometric detail. Muscle activation weighting that accounts for differences in geometric complexity across muscles corrects for this recruitment bias.

Mechanical evaluation of revision surgery for femoral shaft nonunion initially treated with intramedullary nailing: Exchange nailing versus augmentation plating

IntroductionExchange nailing (EN) or augmentation plating (AP) has been employed to treat nonunions after intramedullary nailing for femoral shaft fractures. Although instability is a factor in hypertrophic nonunion, mechanical evaluations have been limited because the contribution of the callus to fracture site stability varies with healing. Our previous study illustrated the potential for evaluation using a finite element analysis (FEA) that incorporates callus material properties. This study aimed to mechanically evaluate revision surgery for nonunions using FEA. Materials and methodsA quantitative computed tomography-based FEA was performed on virtual revision models of a patient with suspected nonunion after intramedullary nailing. In addition to the initial nailing model (IN) with an 11-mm diameter (D) and 360-mm length (L), four EN models with D12mm (EN1), D13mm (EN2), D12mm-L400mm (EN3), and D13mm-L400mm (EN4) nails and three AP models with 5- (AP1), 6- (AP2), and 7-hole (AP3) plates were created. As with bone, callus was assigned inhomogeneous material properties derived from density based on an empirical formula. The hip joint reaction force and muscle forces at maximum load during the gait cycle were applied. The volume ratio of the callus at the fracture site with a tensile failure risk of ≥1 (tensile failure ratio) and bone fragment movement were evaluated. ResultsThe tensile failure ratio was 11.6 % (IN), 10.1 % (EN1), 6.3 % (EN2), 10.9 % (EN3), 6.2 % (EN4), 6.4 % (AP1), 7.2 % (AP2), and 7.7 % (AP3), respectively. The bone fragment movement showed an opening on the lateral side with the initial intramedullary nailing. However, both revision surgeries reduced the opening, leading to compression except in the EN1 model. The proximal bone fragments were internally rotated relative to the distal fragments, and the rotational instability was more suppressed in models with lower tensile failure ratio. ConclusionsFor EN, the increase in diameter, not length, is important to suppress instability. AP reduces instability, comparable to a 2 mm increase in nail diameter, and screw fixation closer to the fracture site reduces instability. This study suggest that AP is mechanically equivalent to EN and could be an option for revision surgery for femoral shaft nonunions.

Influence of femoral anteversion angle and neck-shaft angle on muscle forces and joint loading during walking.

Femoral deformities, e.g. increased or decreased femoral anteversion (AVA) and neck-shaft angle (NSA), can lead to pathological gait patterns, altered joint loads, and degenerative joint diseases. The mechanism how femoral geometry influences muscle forces and joint load during walking is still not fully understood. The objective of our study was to investigate the influence of femoral AVA and NSA on muscle forces and joint loads during walking. We conducted a comprehensive musculoskeletal modelling study based on three-dimensional motion capture data of a healthy person with a typical gait pattern. We created 25 musculoskeletal models with a variety of NSA (93°-153°) and AVA (-12°-48°). For each model we calculated moment arms, muscle forces, muscle moments, co-contraction indices and joint loads using OpenSim. Multiple regression analyses were used to predict muscle activations, muscle moments, co-contraction indices, and joint contact forces based on the femoral geometry. We found a significant increase in co-contraction of hip and knee joint spanning muscles in models with increasing AVA and NSA, which led to a substantial increase in hip and knee joint contact forces. Decreased AVA and NSA had a minor impact on muscle and joint contact forces. Large AVA lead to increases in both knee and hip contact forces. Large NSA (153°) combined with large AVA (48°) led to increases in hip joint contact forces by five times body weight. Low NSA (108° and 93°) combined with large AVA (48°) led to two-fold increases in the second peak of the knee contact forces. Increased joint contact forces in models with increased AVA and NSA were linked to changes in hip muscle moment arms and compensatory increases in hip and knee muscle forces. Knowing the influence of femoral geometry on muscle forces and joint loads can help clinicians to improve treatment strategies in patients with femoral deformities.

Simulated Increase in Monoarticular Hip Muscle Strength Reduces the First Peak of Knee Compression Forces During Walking.

Reducing compressive knee contact forces (KCF) during walking could slow the progression and reduce symptoms of knee osteoarthritis. A previous study has shown that compensating for the hip flexion/extension moment could reduce the KCF peak occurring during early stance (KCFp1). Therefore, this study aimed to identify if monoarticular hip muscle could allow this compensation while considering different walking strategies. Gait trials from 24 healthy participants were used to make musculoskeletal models, and five load-cases were examined: (I) Normal, (II) with an applied external moment compensating for 100% of the hip flexion/extension moment, and (III-V) three conditions with isolated/combined 30% increase of peak isometric strength of gluteus medius and maximus. Knee contact forces, hip muscle forces, and joint moments were computed. A cluster analysis of the Normal condition was performed with hip and knee flexion/extension moment during KCFp1 as input to examine the influence of different walking strategies. The cluster analysis revealed two groups having significantly different hip and knee moments in early-stance (p < 0.01). The reduction in KCFp1 from the Normal condition, although present in both groups, was greater for the group with the highest hip and lowest knee flexion/extension moments for all conditions tested (II: -21.82 ± 8.71% versus -6.03 ± 6.68%, III: -3.21 ± 1.09% versus -1.59 ± 0.96%, IV: -3.00 ± 0.89% versus -1.76 ± 1.04%, V: -6.12 ± 1.69 versus -3.09 ± 1.95%). This reduction in KCFp1 occurred through a shift in force developed by the hamstrings during walking (biarticular) to the gluteus medius and maximus (monoarticular), whose isometric strength was increased. The differences between the groups suggest that this reduction depends on the walking strategy.

Differences in hip musculoskeletal loads between limbs during daily activities in patients with 3D-printed hemipelvic reconstructions following tumor surgery

BackgroundAnatomical custom-made prostheses, thanks to computer-aided design and 3D-printing technology, help improve osseointegration and reduce mechanical complications in bone reconstructions following bone tumors. A recent quantitative analysis of long-term recovery in patients with 3D-printed reconstructions following pelvic tumor surgery showed asymmetries in ground reaction forces between limbs during different motor activities, while standing very good motor performance and quality of life. Research questionWe analyzed hip contact forces and muscle forces in that cohort of six patients with an innovative custom-made reconstruction of the hemipelvis, and we tested the hypothesis that asymmetries in ground reaction forces would result in more marked differences in musculoskeletal forces. MethodsState-of-the-art musculoskeletal modeling in an optimization-based inverse-dynamics workflow was used to calculate hip contact forces and muscle forces during five motor activities, and the differences between limbs were statistically evaluated across the motor activity cycles and on the force peaks. ResultsThe musculoskeletal loads were found to be not symmetric, as hip loads were generally higher in the contralateral limb. We found significant differences in considerable portions of the motor activities cycles except squat, load symmetry indices indicating a load increase (median up to 25%) on the contralateral limb, especially during stair descent and chair rise/sit, and significantly higher values in the contralateral limb at force peaks. SignificanceWe confirmed the hypothesis that residual asymmetries found in ground reaction forces were amplified when hip musculoskeletal loads were investigated, reflecting a shift of the loads toward the intact limb. Despite the general trend of higher loads found in the contralateral hip, this cannot be considered a risk of overloading, as both hips supported loads in a physiological range or lower, indicating a likely optimal recovery.

The functional role of hip muscles during gait in patients with increased femoral anteversion

BackgroundFemoral anteversion affects the lever arm and moment-generating capacity of the hip abductors, while an increased hip internal rotation during walking was proposed to be a compensatory mechanism to restore the abductive lever arm. Children with isolated increased femoral anteversion, however, do not always present a deficit in the net hip abduction moment during gait, suggesting that a more comprehensive understanding of the effect of morphology and motion on muscle forces and moments is needed to aid clinical decision making. Research questionAre muscle contributions to hip joint moments and muscle forces altered in patients with increased femoral anteversion and internally rotated gait pattern compared to a control group of typically developing children? And how would the functional role of the muscle be altered if the patients walked straight? MethodsThis follow-up study compared patients with increased femoral anteversion (n = 42, 12.8 ± 1.9 years, femoral anteversion: 39.6 ± 6.9°) to controls (n = 9, 12.0 ± 3.0 years, femoral anteversion: 18.7 ± 4.1°). Muscle forces and moment contributions were calculated using personalized musculoskeletal models. Additionally, a hypothetical scenario, in which the gait of the controls was modelled with an anteverted femoral morphology, was used to understand what would happen if the patients walked straight. ResultsGluteus medius abductive contribution was lower in patients compared to controls, despite a comparable net abduction moment around the hip. Patients presented lower muscle forces. However, if modelled to walk straight, they would require higher forces as well as a larger co-contraction of both hip internal and external rotators in the transversal plane. SignificanceThis study suggests that patients with increased femoral anteversion walking with an internally rotated gait pattern present lower muscle forces, but when modelled to walk straight muscle forces increase. The current results provide important information to better understand this condition and improve treatment recommendations in these patients.

Prediction of in vivo hip contact forces during common activities of daily living using a segment-based musculoskeletal model.

Background: Quantifying in vivo hip muscle and contact forces during activities of daily living (ADL) provides valuable information for diagnosis and treatment of hip-related disorders. The objective of this study was to utilize Freebody, a segment-based musculoskeletal model, for the prediction of hip contact forces using a novel objective function during seven common ADLs and validate its performance against the publicly available HIP98 dataset. Methods: Marker data, ground reaction forces, and hip contact forces during slow, normal, and fast walking, stair ascent and descent, and standing up and sitting down were extracted for 3 subjects from the HIP98 dataset. A musculoskeletal anatomical dataset was scaled to match the dimensions of each subject, and muscle and hip contact forces were estimated by minimizing a novel objective function, which was the summation of the muscle stresses squared and body weight-normalised hip contact force. The accuracy of predictions were quantified using several metrics, and muscle forces were qualitatively compared to experimental EMGs in the literature. Results: FreeBody predicted the hip contact forces during the ADLs with encouraging accuracy: The root mean squared error of predictions were 44.0 ± 8.5, 47.4 ± 6.5, and 59.8 ± 7.1% BW during slow, normal, and fast walking, 44.2 ± 16.8% and 53.3 ± 12.2% BW for stair ascent and descent, and 31.8 ± 8.2% and 17.1 ± 5.0% BW for standing up and sitting down, respectively. The error in prediction of peak hip contact forces were 14-18%, 24-28%, 17-35% for slow, normal, and fast walking, 7-25% and 15-32% in stair ascent and descent, and around 10% for standing up and sitting down. The coefficient of determination was larger than 0.90 in all activities except in standing up (0.86 ± 0.08). Conclusion: This study has implemented a novel objective function in a segment-based musculoskeletal model, FreeBody, for the prediction of hip contact forces during a large range of ADLs. The model outputs compare favourably for all ADLs and are the best in standing up and sitting down, while muscle activation patterns are consistent with experimental EMGs from literature. This new objective function addresses one of the major limitations associated with musculoskeletal models in the literature, namely the high non-physiological predicted hip joint contact forces.

Predicting the hip joint centre in children: New regression equations, linear scaling, and statistical shape modelling

Determination of the hip joint centre (HJC) is important to accurately estimate hip joint motion, moments and muscle forces. The most accurate method for HJC estimation without medical imaging is an area of interest in the biomechanics community, especially in a paediatric population, which has not been widely evaluated. HJC locations were calculated by sphere-fitting to the acetabulum of three-dimensional pelvises segmented from 333 CT scans of children aged 4 to 18 years old. Three methods for determining the HJC were compared: regression equations, linear scaling, and shape model prediction. The new regression equations developed in this study produced Euclidean distance errors of 6.23 mm ± 2.90 mm. Linear scaling of paediatric bone produced errors of 3.90 mm ± 2.52 mm and adult bone scaling of 5.45 mm ± 3.26 mm. Prediction of the HJC using a paediatric statistical shape model produced mean Euclidian distance errors of 2.95 mm ± 1.65 mm. Overall, shape model prediction of the HJC produced the lowest errors, with linear scaling of a mean paediatric pelvis providing better estimates than regression equations.

Biomechanical compensations during a stand-to-sit maneuver using transfemoral osseointegrated prostheses: A case series

BackgroundPatients with transfemoral amputation and socket prostheses are at a heightened risk of developing musculoskeletal overuse injuries, commonly due to altered joint biomechanics. Osseointegrated prostheses, which involve direct anchorage of the prosthesis to the residual limb through a bone anchored prosthesis, are a novel alternative to sockets yet their biomechanical effect is largely unknown. MethodsFour patients scheduled to undergo unilateral transfemoral prosthesis osseointegration completed two data collections (baseline with socket prosthesis and 12-months after prosthesis osseointegration) in which whole-body kinematics and ground reaction forces were collected during stand-to-sit tasks. Trunk, pelvis, and hip kinematics, and the surrounding muscle forces, were calculated using subject-specific musculoskeletal models developed in OpenSim. Peak joint angles and muscle forces were compared between timepoints using Cohen's d effect sizes. FindingsCompared to baseline with socket prostheses, patients with osseointegrated prostheses demonstrated reduced lateral trunk bending (d = 1.46), pelvic obliquity (d = 1.09), and rotation (d = 1.77) toward the amputated limb during the stand to sit task. This was accompanied by increased amputated limb hip flexor, abductor, and rotator muscle forces (d> > 0.8). InterpretationImproved lumbopelvic movement patterns and stabilizing muscle forces when using an osseointegrated prosthesis indicate that this novel prosthesis type likely reduces the risk of the development and/or progression of overuse injuries, such as low back pain and osteoarthritis. We attribute the increased muscle hip muscle forces to the increased load transmission between the osseointegrated prosthesis and residual limb, which allows a greater eccentric ability of the amputated limb to control lowering during the stand-to-sit task.

Artificial Neural Network Detects Hip Muscle Forces as Determinant for Harmonic Walking in People after Stroke.

Many recent studies have highlighted that the harmony of physiological walking is based on a specific proportion between the durations of the phases of the gait cycle. When this proportion is close to the so-called golden ratio (about 1.618), the gait cycle assumes an autosimilar fractal structure. In stroke patients this harmony is altered, but it is unclear which factor is associated with the ratios between gait phases because these relationships are probably not linear. We used an artificial neural network to determine the weights associable to each factor for determining the ratio between gait phases and hence the harmony of walking. As expected, the gait ratio obtained as the ratio between stride duration and stance duration was found to be associated with walking speed and stride length, but also with hip muscle forces. These muscles could be important for exploiting the recovery of energy typical of the pendular mechanism of walking. Our study also highlighted that the results of an artificial neural network should be associated with a reliability analysis, being a non-deterministic approach. A good level of reliability was found for the findings of our study.

Walking Pole Gait to Reduce Joint Loading post Total Knee Athroplasty: Musculoskeletal modeling Approach.

Excessive knee contact loading is precursor to osteoarthritis and related knee ailment leading to knee athroplasty. Reducing contact loading through gait modifications using assisted pole walking offers noninvasive process of medial load offloading at knee joint. In this paper, we evaluate the efficacy of different configuration of pole walking for reducing contact force at the knee joint through musculoskeletal (MSK) modeling. We have developed a musculoskeletal model for a subject with knee athroplasty utilizing in-vivo implant data and computed tibio-femoral contact force for different pole walking conditions to evaluate the best possible configuration for guiding rehabilitation, correlated with different gait phases. Effect of gait speed variation on knee contact force, hip joint dynamics and muscle forces are simulated using the developed MSK model. Results indicate some interesting trend of load reduction, dependent on loading phases pertaining to different pole configuration. Insights gained from the simulation can aid in designing personalized rehabilitation therapy for subjects suffering from Osteoarthritis.

Quantifying Muscle Forces and Joint Loading During Hip Exercises Performed With and Without an Elastic Resistance Band.

An increase in hip joint contact forces (HJCFs) is one of the main contributing mechanical causes of hip joint pathologies, such as hip osteoarthritis, and its progression. The strengthening of the surrounding muscles of the joint is a way to increase joint stability, which results in the reduction of HJCF. Most of the exercise recommendations are based on expert opinions instead of evidence-based facts. This study aimed to quantify muscle forces and joint loading during rehabilitative exercises using an elastic resistance band (ERB). Hip exercise movements of 16 healthy volunteers were recorded using a three-dimensional motion capture system and two force plates. All exercises were performed without and with an ERB and two execution velocities. Hip joint kinematics, kinetics, muscle forces, and HJCF were calculated based on the musculoskeletal simulations in OpenSim. Time-normalized waveforms of the different exercise modalities were compared with each other and with reference values found during walking. The results showed that training with an ERB increases both target muscle forces and HJCF. Furthermore, the ERB reduced the hip joint range of motion during the exercises. The type of ERB used (soft vs. stiff ERB) and the execution velocity of the exercise had a minor impact on the peak muscle forces and HJCF. The velocity of exercise execution, however, had an influence on the total required muscle force. Performing hip exercises without an ERB resulted in similar or lower peak HJCF and lower muscle forces than those found during walking. Adding an ERB during hip exercises increased the peak muscle and HJCF but the values remained below those found during walking. Our workflow and findings can be used in conjunction with future studies to support exercise design.

Subject-Specific Modeling of Femoral Torsion Influences the Prediction of Hip Loading During Gait in Asymptomatic Adults.

Hip osteoarthritis may be caused by increased or abnormal intra-articular forces, which are known to be related to structural articular cartilage damage. Femoral torsional deformities have previously been correlated with hip pain and labral damage, and they may contribute to the onset of hip osteoarthritis by exacerbating the effects of existing pathoanatomies, such as cam and pincer morphologies. A comprehensive understanding of the influence of femoral morphotypes on hip joint loading requires subject-specific morphometric and biomechanical data on the movement characteristics of individuals exhibiting varying degrees of femoral torsion. The aim of this study was to evaluate hip kinematics and kinetics as well as muscle and joint loads during gait in a group of adult subjects presenting a heterogeneous range of femoral torsion by means of personalized musculoskeletal models. Thirty-seven healthy volunteers underwent a 3D gait analysis at a self-selected walking speed. Femoral torsion was evaluated with low-dosage biplanar radiography. The collected motion capture data were used as input for an inverse dynamics analysis. Personalized musculoskeletal models were created by including femoral geometries that matched each subject’s radiographically measured femoral torsion. Correlations between femoral torsion and hip kinematics and kinetics, hip contact forces (HCFs), and muscle forces were analyzed. Within the investigated cohort, higher femoral antetorsion led to significantly higher anteromedial HCFs during gait (medial during loaded stance phase and anterior during swing phase). Most of the loads during gait are transmitted through the anterior/superolateral quadrant of the acetabulum. Correlations with hip kinematics and muscle forces were also observed. Femoral antetorsion, through altered kinematic strategies and different muscle activations and forces, may therefore lead to altered joint mechanics and pose a risk for articular damage. The method proposed in this study, which accounts for both morphological and kinematic characteristics, might help in identifying in a clinical setting patients who, as a consequence of altered femoral torsional alignment, present more severe functional impairments and altered joint mechanics and are therefore at a higher risk for cartilage damage and early onset of hip osteoarthritis.

Effectiveness of Dry Needling Therapy on Pain, Hip Muscle Strength, and Physical Function in Patients With Hip Osteoarthritis: A Randomized Controlled Trial

ObjectiveTo investigate the short-term effects of dry needling (DN) on physical function, pain, and hip muscle strength in patients with hip osteoarthritis (OA). DesignA double-blind, placebo-control, randomized controlled trial. SettingPrivate practice physiotherapy clinic. ParticipantsPatients with unilateral hip OA (N=45) were randomly allocated to a DN group, sham DN group, or control group. InterventionsPatients in the DN and sham groups received 3 treatment sessions. Three active myofascial trigger points (MTrPs) were treated in each session with DN or a sham needle procedure. The treatment was applied in active MTrPs of the iliopsoas, rectus femoris, tensor fasciae latae, and gluteus minimus muscles. Main Outcome MeasuresPhysical function was assessed with the Western Ontario and McMaster Universities (WOMAC) physical function subscale, the timed Up and Go test, and the 40-meter self-paced walk test. Intensity of hip pain related to physical function was evaluated using the visual analog scale and WOMAC pain subscale. The maximal isometric force of hip muscles was recorded with a handheld dynamometer. ResultsSignificant group by time interactions were shown for physical function, pain, and hip muscle force variables. Post hoc tests revealed a significant reduction in hip pain and significant improvements in physical function and hip muscle strength in the DN group compared with the sham and control groups. The DN group showed within- and between-groups large effect sizes (d>0.8). ConclusionsDN therapy in active MTrPs of the hip muscles reduced pain and improved hip muscle strength and physical function in patients with hip OA. DN in active MTrPs of the hip muscles should be considered for the management of hip OA.

Hip Joint Contact Loading and Muscle Forces During Running With a Transtibial Amputation.

People with unilateral transtibial amputations (TTA) have greater risks of bilateral hip osteoarthritis, related to asymmetric biomechanics compared to people without TTA. Running is beneficial for physical health and is gaining popularity. However, people with TTA may not have access to running-specific prostheses (RSPs), which are designed for running, and may instead run using their daily-use prosthesis (DUP). Differences in joint loading may result from prosthesis choice; thus, it is important to characterize changes in peak and impulsive hip joint contact loading during running. Six people with and without TTA ran at 3.5 m/s while ground reaction forces, kinematics, and electromyography were collected. People with TTA ran using their own RSP and DUP. Musculoskeletal models incorporating prosthesis type of each individual were used to quantify individual muscle forces and hip joint contact forces (HJCFs) during running. People using RSPs had smaller bilateral peak hip joint contact forces compared to when wearing DUPs during stance and swing, and a smaller impulse over the entire gait cycle. Greater amputated leg peak hip joint contact forces for people wearing DUPs compared to RSPs occurred with greater forces from the ipsilateral gluteus maximus during stance. People with TTA also had greater bilateral peak hip joint contact forces during swing compared to people without TTA, which occurred with greater peak gluteus medius forces. Running with more compliant RSPs may be beneficial for long-term joint health by reducing peak and impulsive hip loading compared to DUPs.

Dysplastic hip anatomy alters muscle moment arm lengths, lines of action, and contributions to joint reaction forces during gait

Developmental dysplasia of the hip (DDH) is characterized by abnormal bony anatomy, which causes detrimental hip joint loading and leads to secondary osteoarthritis. Hip joint loading depends, in part, on muscle-induced joint reaction forces (JRFs), and therefore, is influenced by hip muscle moment arm lengths (MALs) and lines of action (LoAs). The current study used subject-specific musculoskeletal models and in-vivo motion analysis to quantify the effects of DDH bony anatomy on dynamic muscle MALs, LoAs, and their contributions to JRF peaks during early (~17%) and late-stance (~52%) of gait. Compared to healthy hips (N = 15, 16–39 y/o), the abductor muscles in patients with untreated DDH (N = 15, 16–39 y/o) had smaller abduction MALs (e.g. anterior gluteus medius, 35.3 vs. 41.6 mm in early stance, 45.4 vs. 52.6 mm late stance, p ≤ 0.01) and more medially-directed LoAs. Abduction-adduction and rotation MALs also differed for major hip flexors such as rectus femoris and iliacus. The altered MALs in DDH corresponded to higher hip abductor forces, medial JRFs (1.26 vs. 0.87 × BW early stance, p = 0.03), and resultant JRFs (5.71 vs. 4.97 × BW late stance, p = 0.05). DDH anatomy not only affected hip muscle force generation in the primary plane of function, but also their out-of-plane mechanics, which collectively elevated JRFs. Overall, hip muscle MALs and their contributions to JRFs were significantly altered by DDH bony anatomy. Therefore, to better understand the mechanisms of joint degeneration and improve the efficacy of treatments for DDH, the dynamic anatomy-force relationships and multi-planar functions of the whole hip musculature must be collectively considered.

Hip Muscle Forces and Contact Loading During Squatting After Cam-Type FAI Surgery.

The purpose of this study was to compare muscle forces and hip contact forces (HCFs) during squatting in patients with cam-type femoroacetabular impingement (cam-FAI) before and after hip corrective surgery and with healthy control participants. Ten symptomatic male patients with cam-FAI performed deep squatting preoperatively and at 2 years postoperatively. Patients were matched by age and body mass index to 10 male control participants. Full-body kinematics and kinetics were computed, and muscle forces and HCFs were estimated using a musculoskeletal model and static optimization. Normalized squat cycle (%SC) trials were compared using statistical nonparametric mapping (SnPM). Postoperatively, patients with cam-FAI squatted down with higher anterior pelvic tilt, higher hip flexion, and greater hip extension moments than preoperatively. Preoperative patients demonstrated lower anterior pelvic tilt and lower hip flexion compared with the participants in the control group. Postoperative patients showed increased semimembranosus force compared with their preoperative values. Preoperative forces were lower than the control group for the adductor magnus, the psoas major, and the semimembranosus; however, the preoperative patients showed greater inferior gluteus maximus forces than the patients in the control group, whereas the postoperative patients did not differ from the control patients. Higher posterior, superior, and resultant HCF magnitudes were identified postoperatively in comparison with the preoperative values. Preoperative posterior HCF was lower than in the control group, whereas the postoperative posterior HCF did not differ from those in the control group. Higher postoperative anterior pelvic tilt was associated with an indication of return to closer to normal pelvic motion, which resembled data from the control group. Lower preoperative anterior pelvic tilt was associated with muscle force imbalance, indicated by decreased semimembranosus and increased gluteus maximus forces. The overall increased postoperative muscle forces were associated with improved pelvic mobility and increased HCFs that were comparable with the control-group standards. Muscle forces and HCFs may be indicative of postoperative joint health restoration and alleviated symptoms.