Artificial contrasting of the hip joint in children and adolescents: X-ray anatomic study

The diagnostic capacities of currently available radiation diagnostic techniques in imaging some anatomic structures of the hip joint (HJ) were determined on the basis of studies of 70 sectional sets of HJs in children and adolescents aged 0 to 13 years through X-ray and anatomic comparisons. Magnetic resonance imaging (MRI) is the method of choice in visualizing the cartilaginous and soft-tissue structures of HJ in children and adolescents. MR-arthrography extends the capacities of the technique in imaging the articular surfaces and intraarticular structures of the joint. Contrast enhancement of the HJ cavity during X-ray study and computed tomography may be an alternative to MRI as it makes it possible to well visualize the cartilaginous head of the femur, the cartilaginous borders of the cotyloid cavity, the limbus, etc. Double contrasting enhances the capacities of detailed imaging of the articular surfaces, intraarticular structures, capsules, and ligamentous apparatus of HJ. The studies performed have specified the time course of anatomic changes during HJ growth and defined the method of choice or an alternative procedure of radiation techniques in the diagnosis of these changes, which is of great importance for early detection of pathological changes and for choice of therapeutic and diagnostic policy.     

Radiodiagnosis of pelvic injuries

The paper deals with an algorithm for the radiodiagnosis of pelvic injuries. The examination of victims with pelvic injuries allows one to state that multislice spiral computed tomography (MSCT) can define the type of pelvic ring instability and the nature of fragment displacement, visualize all types of fractures of pelvic bones and cotyloid cavity walls, and reveal intrapelvic hematomas, as well as changes in adjacent soft tissues, sacroiliac joints, intrapelvic vessels and organs. MSCT angiography is a technique that can be successfully used at different stages of diagnosis and as the first imaging method or as a pre-examination one if the diagnosis is established and as a control study. The scope and quality of obtained information are generally sufficient to make a decision on treatment policy.     

Early x-ray diagnosis of hip dysplasia in children]

The author proposes a method of differential diagnosis of hip dislocations and hip joint dysplasia in infants aged 3 months. The alpha-angle of hip dislocation with relation to trochanteric space is determined on an anteroposterior radiogram of the hip joints; 64 degrees means hip dysplasia, 65-69 degrees and more mean dislocation. This method was tested in 75 children (150 joints) aged 3 months. A mean diagnostic accuracy was 90.1%.     

Crouched postures reduce the capacity of muscles to extend the hip and knee during the single-limb stance phase of gait

Many children with cerebral palsy walk in a crouch gait that progressively worsens over time, decreasing walking efficiency and leading to joint degeneration. This study examined the effect of crouched postures on the capacity of muscles to extend the hip and knee joints and the joint flexions induced by gravity during the single-limb stance phase of gait. We first characterized representative mild, moderate, and severe crouch gait kinematics based on a large group of subjects with cerebral palsy (N=316). We then used a three-dimensional model of the musculoskeletal system and its associated equations of motion to determine the effect of these crouched gait postures on (1) the capacity of individual muscles to extend the hip and knee joints, which we defined as the angular accelerations of the joints, towards extension, that resulted from applying a 1N muscle force to the model, and (2) the angular acceleration of the joints induced by gravity. Our analysis showed that the capacities of almost all the major hip and knee extensors were markedly reduced in a crouched gait posture, with the exception of the hamstrings muscle group, whose extension capacity was maintained in a crouched posture. Crouch gait also increased the flexion accelerations induced by gravity at the hip and knee throughout single-limb stance. These findings help explain the increased energy requirements and progressive nature of crouch gait in patients with cerebral palsy.     

Biarticular hip extensor and knee flexor muscle moment arms of the feline hindlimb

Moment arms are important for understanding muscular behavior and for calculating internal muscle forces in musculoskeletal simulations. Biarticular muscles cross two joints and have moment arms that depend on the angle of both joints the muscles cross. The tendon excursion method was used to measure the joint angle-dependence of hamstring (biceps femoris, semimembranosus and semitendinosus) moment arm magnitudes of the feline hindlimb at the knee and hip joints. Knee angle influenced hamstring moment arm magnitudes at the hip joint; compared to a flexed knee joint, the moment arm for semimembranosus posterior at the hip was at most 7.4 mm (25%) larger when the knee was extended. On average, hamstring moment arms at the hip increased by 4.9 mm when the knee was more extended. In contrast, moment arm magnitudes at the knee varied by less than 2.8 mm (mean=1.6 mm) for all hamstring muscles at the two hip joint angles tested. Thus, hamstring moment arms at the hip were dependent on knee position, while hamstring moment arms at the knee were not as strongly associated with relative hip position. Additionally, the feline hamstring muscle group had a larger mechanical advantage at the hip than at the knee joint.     

Effect of articular cartilage resection on the growth and formation of the femoral and acetabular epiphyses]

Different parts of the articular cartilage were resected in 46 rabbits at the age of 2.5 months. The resected narrow stripe of the articular cartilage completely restored by the 60--90th day and the growth of the condyles was not disturbed. Resection of considerable areas of the articular cartilage on the condyles and on the femoral head was accompanied by a certain disturbance of the osseous tissue growth in these areas with resulted impression of the condyles, deformation of the head and further formation of coxa vara. The removal of 1/3 of the articular cartilage of the cotyloid cavity resulted in a certain increase of its diamter, uneven development at the site of resection; the femoral head of this joint increased, its spherical shape was altered. The restored cartilage did not restore its original structure characteristic for a growing bone. The newly formed articular cartilage lost its ability to participate in endochondral bone formation during the growth of the animal.     

Ultrasonographic Features of Hip Joints in Mucopolysaccharidoses Type I and II

Objectives

The primary aim of this study was to assess the ultrasonographic features of hip joints in patients with mucopolysaccharidosis (MPS) type I and II in comparison with healthy population. The secondary aims were to correlate these features with clinical measures and to evaluate the utility of ultrasound in the diagnosis of MPS disease.

Materials and Methods

Sixteen MPS I (n = 3) and II (n = 13) patients were enrolled in the present study and underwent clinical and radiological evaluation, and bilateral high-resolution ultrasonography (US) of hip joints. The distance from the femoral neck to joint capsule (synovial joint space, SJS), joint effusion, synovial hyperthrophy, and local pathological vascularization were evaluated. The results were compared to the healthy population and correlated with clinical and radiological measures.

Results

1. There was a difference in US SJS between children with MPS disease and the normative value for healthy population (7mm). Mean values of SJS were 15.81 ± 4.08 cm (right hip joints) and 15.69 ± 4.19 cm (left joints). 2. No inflammatory joint abnormalities were detected in MPS patients. 3. There was a clear correlation between US SJS and patients’ age and height, while no clear correlation was observed between SJS and disease severity.

Conclusions

1. Patients with MPS I and II present specific features in hip joint ultrasonography. 2. The data suggests that ultrasonography might be effective in the evaluation of hip joint involvement in patients with MPS and might present a valuable tool in facilitating the diagnosis and follow up of the disease.     

An induced acceleration index for examining joint couplings

A muscle produces moments at the joints it crosses, but these moments can also cause accelerations at joints not crossed by the muscle. This phenomenon, the acceleration of a joint caused by a muscle not crossing the joint, is referred to as induced acceleration. For a system of rigid bodies this study examines how system configuration, and segmental inertial properties dictate the potential of one joint to cause the acceleration of other joints in the system. From the equations of motion for a series of rigid bodies, an induced acceleration index (IAI) was developed. The IAI permits quantification of the relative potential of moments produced at joints in the kinematic chain to accelerate other joints in the kinematic chain. The IAI is a function of system orientation, segment lengths, and inertial properties. The IAI was used to examine the roles of the ankle and hip joints in quiet standing. The ankle joint had over 12 times the ability to accelerate the hip joint, than the hip had to accelerate the ankle joint. These results in part explain the relative merits of the two strategies predominantly used to maintain upright stance: the ankle and hip strategies. This index permits an understanding of how the induced accelerations are dependent on system configuration and inertial properties. The IAI is also useful in situations where the inertial properties of the system under investigation changes, for example due to the fitting of a new prostheses to a trans-tibial amputee.     

Inter-segmental coordination: motor pattern in humans stepping over an obstacle with mechanical ankle joint friction

This study examined the influence of a mechanical perturbation of the ankle joint on obstacle avoidance pattern. A decoupled control between the distal joint and the combined (hip-knee) proximal joints was observed according to the task requirement. In this context, a greater mechanical friction at the ankle should be compensated at this joint (local compensation) or alternatively, by regulating more combined proximal joints (knee and/or hip). The leading limb inter-segmental coordination was evaluated in both no constraint and constraint conditions in calculating ranges of motion (ROM), moments of force and powers (from heel-off to obstacle) at the ankle, knee and hip joints. Electromyographic activities were also analyzed. With the constraint, the dorsiflexor moment and the tibialis anterior activity remained unchanged while both ROM and power bursts (absorbed and generated) decreased. The hip and knee ROM remain invariant. At heel-off the absorption by hip extensors decreased and the forthcoming generation by knee flexors increased in the constraint condition. To quantify the inter-joint coordination, principal component analysis was used and indicated a high level of inter-joint coupling (synergy) that decreased with the constraint (i.e. less inter-joint coupling). At the ankle joint, the results suggest that the central command was the same in both conditions thus, not be adapted. At both the hip and knee joints, a combined joints modulation occurred to overcome additional friction.     

Influence of figure skating skates on vertical jumping performance

The purpose of this study was to investigate the influence of wearing figure skating skates on vertical jump performance and interjoint co-ordinations described in terms of sequencing and timing of joint rotations. Ten national to international figure skaters were filmed while performing a squat jump (SJ) on a force platform. Three experimental conditions were successively realized: barefoot (BF), lifting a 1.5 kg weight (LW) corresponding to the skates' mass, attached on the distal extremity of each leg and wearing skates (SK). Jump height, angular kinematics as well as joints kinetics were calculated. Relative to the SJ height reached in the BF condition, SJ performance was significantly decreased by 2.1 and 5.5 cm in the LW and SK conditions, respectively. The restriction of ankle amplitude imposed by wearing skates was found to significantly limit the knee joint amplitude while the hip angular motion was not affected. Neither the skates' mass nor the limited ankle angular motion modified the proximo-distal organization of joint co-ordination observed when jumping barefoot. However, with plantar flexion restriction, the delay between hip and knee extensions increased while it was reduced between knee and ankle extensions. Work output at the knee and ankle joints were significantly lowered when wearing skates. The decrease of work at the knee was shown to result from an early flexing moment causing a premature deceleration of the knee and from a reduction of knee amplitude. Taken together, these results show a minimization of the participation of the knee when plantar flexion is limited. It was proposed that constraining the distal joint causes a reorganization of interjoint co-ordinations and a redistribution of the energy produced by knee extensors to the hip and ankle joints.     

Muscle recruitment strategies can reduce joint loading during level walking

Joint inflammation, with consequent cartilage damage and pain, typically reduces functionality and affects activities of daily life in a variety of musculoskeletal diseases. Since mechanical loading is an important determinant of the disease process, a possible conservative treatment is the unloading of joints. In principle, a neuromuscular rehabilitation program aimed to promote alternative muscle recruitments could reduce the loads on the lower-limb joints during walking. The extent of joint load reduction one could expect from this approach remains unknown. Furthermore, assuming significant reductions of the load on the affected joint can be achieved, it is unclear whether, and to what extent, the other joints will be overloaded. Using subject-specific musculoskeletal models of four different participants, we computed the muscle recruitment strategies that minimised the hip, knee and ankle contact force, and predicted the contact forces such strategies induced at the other joints. Significant reductions of the peak force and impulse at the knee and hip were obtained, while only a minimal effect was found at the ankle joint. Adversely, the peak force and the impulse in non-targeted joints increased when aiming to minimize the load in an adjacent joint. These results confirm the potential of alternative muscle recruitment strategies to reduce the loading at the knee and the hip, but not at the ankle. Therefore, neuromuscular rehabilitation can be targeted to reduce the loading at affected joints but must be considered carefully in patients with multiple joints affected due to the potential adverse effects in non-targeted joints.     

Direct comparison of calculated hip joint contact forces with those measured using instrumented implants. An evaluation of a three-dimensional mathematical model of the lower limb

Characterisation of hip joint contact forces is essential for the definition of hip joint prosthesis design requirements. In vivo hip joint contact force measurements have been made using instrumented hip joint prostheses. However, to allow determination of the range of values of joint contact force and their directions relative to anatomical structures in a range of subject groups sufficient to form an agreed data base it is necessary to adopt a different approach without the use of an implanted transducer. The use of mathematical models of the lower limb to examine the forces in soft tissues and at the joints has provided valuable insight into internal loading conditions. Several authors have proposed mathematical musculo-skeletal models. However, there have been only limited attempts at validation of these models. It is possible to use the results of in vivo force measurements from instrumented prostheses to validate the results calculated using the mathematical models. In this study two subjects with instrumented hip joint prostheses were studied. Forces at the hip joints were calculated using a three-dimensional model of the leg. Walking at slow, normal and fast speeds (0.97-2.01m/s), weight transfer from two to one leg and back again, and sit to stand were studied. Direct comparisons were made between the 'gold standard' measured hip joint contact forces and the calculated forces. There was general agreement between the calculated and measured forces in both pattern and magnitude. There were, however, discrepancies. Reasons for these differences in results are discussed and possible model developments suggested.     

More than one way to be a giant: Convergence and disparity in the hip joints of saurischian dinosaurs

Saurischian dinosaurs evolved seven orders of magnitude in body mass, as well as a wide diversity of hip joint morphology and locomotor postures. The very largest saurischians possess incongruent bony hip joints, suggesting that large volumes of soft tissues mediated hip articulation. To understand the evolutionary trends and functional relationships between body size and hip anatomy of saurischians, we tested the relationships among discrete and continuous morphological characters using phylogenetically corrected regression. Giant theropods and sauropods convergently evolved highly cartilaginous hip joints by reducing supraacetabular ossifications, a condition unlike that in early dinosauromorphs. However, transitions in femoral and acetabular soft tissues indicate that large sauropods and theropods built their hip joints in fundamentally different ways. In sauropods, the femoral head possesses irregularly rugose subchondral surfaces for thick hyaline cartilage. Hip articulation was achieved primarily using the highly cartilaginous femoral head and the supraacetabular labrum on the acetabular ceiling. In contrast, theropods covered their femoral head and neck with thinner hyaline cartilage and maintained extensive articulation between the fibrocartilaginous femoral neck and the antitrochanter. These findings suggest that the hip joints of giant sauropods were built to sustain large compressive loads, whereas those of giant theropods experienced compression and shear forces.     

Effect of landing height on frontal plane kinematics, kinetics and energy dissipation at lower extremity joints

Lack of the necessary magnitude of energy dissipation by lower extremity joint muscles may be implicated in elevated impact stresses present during landing from greater heights. These increased stresses are experienced by supporting tissues like cartilage, ligaments and bones, thus aggravating injury risk. This study sought to investigate frontal plane kinematics, kinetics and energetics of lower extremity joints during landing from different heights. Eighteen male recreational athletes were instructed to perform drop-landing tasks from 0.3- to 0.6-m heights. Force plates and motion-capture system were used to capture ground reaction force and kinematics data, respectively. Joint moment was calculated using inverse dynamics. Joint power was computed as a product of joint moment and angular velocity. Work was defined as joint power integrated over time. Hip and knee joints delivered significantly greater joint power and eccentric work (p<0.05) than the ankle joint at both landing heights. Substantial increase (p<0.05) in eccentric work was noted at the hip joint in response to increasing landing height. Knee and hip joints acted as key contributors to total energy dissipation in the frontal plane with increase in peak ground reaction force (GRF). The hip joint was the top contributor to energy absorption, which indicated a hip-dominant strategy in the frontal plane in response to peak GRF during landing. Future studies should investigate joint motions that can maximize energy dissipation or reduce the need for energy dissipation in the frontal plane at the various joints, and to evaluate their effects on the attenuation of lower extremity injury risk during landing.     

Simulated hip abductor strengthening reduces peak joint contact forces in patients with total hip arthroplasty

Lower extremity muscle strength training is a focus of rehabilitation following total hip arthroplasty (THA). Strength of the hip abductor muscle group is a predictor of overall function following THA. The purpose of this study was to investigate the effects of hip abductor strengthening following rehabilitation on joint contact forces (JCFs) in the lower extremity and low back during a high demand step down task. Five THA patients performed lower extremity maximum isometric strength tests and a stair descent task. Patient-specific musculoskeletal models were created in OpenSim and maximum isometric strength parameters were scaled to reproduce measured pre-operative joint torques. A pre-operative forward dynamic simulation of each patient performing the stair descent was constructed using their corresponding patient-specific model to predict JCFs at the ankle, knee, hip, and low back. The hip abductor muscles were strengthened with clinically supported increases (0–30%) above pre-operative values in a probabilistic framework to predict the effects on peak JCFs (99% confidence bounds). Simulated hip abductor strengthening resulted in lower peak JCFs relative to pre-operative for all five patients at the hip (18.9–23.8 ± 16.5%) and knee (20.5–23.8 ± 11.2%). Four of the five patients had reductions at the ankle (7.1–8.5 ± 11.3%) and low back (3.5–7.0 ± 5.3%) with one patient demonstrating no change. The reduction in JCF at the hip joint and at joints other than the hip with hip abductor strengthening demonstrates the dynamic and mechanical interdependencies of the knee, hip and spine that can be targeted in early THA rehabilitation to improve overall patient function.     

Biomechanical model and evaluation of a linear motion squat type exercise

A biomechanical model of a squat exercise performed on a device using a bar that is restricted to a linear motion was developed. Hip and knee moments were evaluated at varying foot positions. The range of motion of the exercise was limited by the knee joint angle beginning at an 80 degrees angle (flexed) to a 179 degrees joint angle (extended). Variations in foot placement were evaluated for differences in torque applied about the transverse axes of the user's knee and hip joints. Because the user's feet were positioned farther forward (anterior), the moment about the knee decreased whereas the moment about the hip increased. Positive moments were those that resulted in forces to flex the knee and hip joints. Positive knee moments were determined in all conditions when the knee was flexed and became negative when the knee was at or near full extension. The model always produced positive moments about the hip. Thus, foot position is a critical factor in hip and knee moments, and therefore in the muscle groups stressed, in a linear motion squat type exercise.     

Alignment of the human body in standing

Alignment of the body in typical symmetrical standing was studied by photographing fifteen subjects in profile on a reaction board. Two aspects of alignment were studied: (1) the anteroposterior position of the body landmarks of knee joint, hip joint, shoulder joint, and ear, compared to the ankle joint; and (2) the positions of the partial centers of gravity above the knee and hip, as a measure of how the body is balanced above these joints. The knee, hip, shoulder, and ear were forward of the ankle in all subjects. On average, the knee was 3.8 (+/- 2.0), the hip 6.2 (+/- 1.3) the shoulder 3.8 (+/- 1.9), and the ear 5.9 (+/- 1.6) cm (+/-S.D.) anterior to the ankle. The positions of landmarks were positively correlated with one another but not highly. The position of the center of gravity could be predicted well from the positions of the landmarks within individual subjects' data, but not across subjects. The centers of gravity above the knee and hip were calculated by subtracting the mass and position of the segments below the joint from the whole-body center of gravity. The center of gravity above the knee was located on average 1.4 (+/- 1.1) cm in front of the joint, and that of the hip 1.0 (+/- 1.6) cm behind the trochanter. Thus, at both knee and hip in typical standing, there exist slight gravitational torques tending to extend the joints.     

The pattern of involvement of appendicular degenerative joint disease

Patterns of degenerative joint disease are investigated in the shoulder, elbow, hip, and knee joints of the macerated remains of approximately 800 individuals from 20th century American and two prehistoric populations. Age is an important contributory factor in all joints, but its effects are seen most directly in the shoulder and hip. Patterns of right-left involvement also indicate the elbow is the most susceptible area to local factors. Multiple joint involvement is seen more often in females from contemporary populations but more often in males from archeological groups. No significant association is found between degenerative involvement and osteometric measurements, and cause of death is probably only incidentally associated with degenerative disease.     

Three-dimensional measurements of the pressure distribution in artificial joints with a capacitive sensor array

A spherically folded capacitive pressure sensor array is introduced and characterized. By placing the sensor array between the ball and the cavity of artificial joints, the pressure distribution within the joint was recorded with spatial resolution for different size matching between the ball and the cavity, for different directions of loading and for joints with incomplete cavities. The performance of the sensor array is analyzed, possible fields of application as well as its limitations are discussed.     

Fatigue effects on the coordinative pattern during cycling: Kinetics and kinematics evaluation

The aim of the present study was to analyze the net joint moment distribution, joint forces and kinematics during cycling to exhaustion. Right pedal forces and lower limb kinematics of ten cyclists were measured throughout a fatigue cycling test at 100% of PO_MAX. The absolute net joint moments, resultant force and kinematics were calculated for the hip, knee and ankle joint through inverse dynamics. The contribution of each joint to the total net joint moments was computed. Decreased pedaling cadence was observed followed by a decreased ankle moment contribution to the total joint moments in the end of the test. The total absolute joint moment, and the hip and knee moments has also increased with fatigue. Resultant force was increased, while kinematics has changed in the end of the test for hip, knee and ankle joints. Reduced ankle contribution to the total absolute joint moment combined with higher ankle force and changes in kinematics has indicated a different mechanical function for this joint. Kinetics and kinematics changes observed at hip and knee joint was expected due to their function as power sources. Kinematics changes would be explained as an attempt to overcome decreased contractile properties of muscles during fatigue.