Hip Force Research Articles

Four-channel telemetry system for in vivo measurement of hip joint forces

The long-term loosening of artificial hip joints remains a serious clinical problem. Optimization of implant design and material will improve the fixation, but it requires a detailed knowledge of the forces which act on the implant. A four-channel telemetric transmitter was developed and arranged completely inside a hermetically closed artificial hip joint. This permits long term in vivo measurements of the three-dimensional forces without endangering the patient. The external telemetry system consists of an inductive power supply, an RF receiver, a microcomputer with hardware extension and a VHS video system. The personal computer offers real-time data processing of three orthogonal force components as well as slow motion analysis of recorded measurements. After several years of animal tests, two instrumented prostheses were implanted in the first patient (male) in May and August of 1988. In March 1990 a third prosthesis was implanted in a second patient (female). Joint force measurements have regularly been performed from the first post-operative day until now for several kinds of activity.

Telemeterized in vivo hip joint force data: A report on two patients after total hip surgery

Two telemeterized femoral components were implanted in two patients as part of normal total hip replacement procedures. The two components were instrumented to measure the three force components directed along: (a) the neck axis, (b) transverse to the neck axis and in the plane of the prosthesis, and (c) transverse to the neck axis and perpendicular to the plane of the prosthesis. Data were collected at multiple sessions during the early postoperative period for a number of standard activities, including gait, stair climbing, rising from a chair, single leg stance, double leg stance, ipsilateral and contralateral straight leg lifts while supine, ipsilateral flexion and extension while standing, and ipsilateral abduction while standing and lying on the contralateral side. These data are summarized and compared with the published results from analytic studies and with the results from previous studies using instrumented femoral components. Peak loads for gait during the period of study were roughly 2.7 body weights (BW) when the patients walked at their normal pace. Contact forces at the hip during stationary single leg stance approximated the peak loads during gait with values ranging from 2.1 to 2.8 BW. The highest forces recorded reached values approaching 5.5 BW and occurred during periods of instability while the patient engaged in stationary single leg stance. Our in vivo data indicate that forces generated during the above activities increase in magnitude quite rapidly during the early postoperative period and that during this period the patients have the ability to perform the activities of daily living without generating the high amplitude joint contact forces suggested by the results of dynamic studies. Joint contact forces during gait were found to depend on speed, but the high absolute magnitudes predicted by model studies were not supported by the in vivo data.

Canine intersegmental hip joint forces and moments before and after cemented total hip replacement

Intersegmental forces and moments (i.e. resultant free body forces and moments computed at the joint centers) were studied in canine hindlimbs before and after cemented total hip replacement (THR). Five large, adult, mixed-breed dogs were selected. Their gait was recorded (while leash-walked) before surgery using high-speed cinematography and a force plate. Cemented total hip replacement was unilaterally performed on each dog. Gait was again recorded at one and four months after surgery. Segmental properties (mass, center of mass, and mass moment of inertia) of the hindlimbs were experimentally determined, and an inverse dynamics approach was used to compute intersegmental forces and moments in the sagittal plane. Significant reductions in intersegmental joint forces and moments were observed in the operated hindlimb one month after surgery, although kinematic gait parameters were unaltered. Decreases of 77.0% for vertical forces, 61.9% for craniocaudal forces, and 66.2% for extension moments were determined. Four months after surgery, the joint forces and moments had returned to their preoperative values. This experiment demonstrates that the dynamics of normal walking can be restored in a canine model by four months after THR. It also shows that kinetic (rather than kinematic) parameters are more descriptive of antalgic gait in the canine.

Hip force calculations and measurements in the same patient

Hip force calculations and measurements in the same patient

Biomechanical analysis of selected principles of hip joint protection

This review article discusses the role of the hip abductor muscles in the generation of forces at the hip joint. The biomechanical rationale behind selected clinical principles of hip joint protection for the patient with hip osteoarthritis is discussed. These principles are based primarily on the benefit of reducing the magnitude of hip abductor muscle forces during walking. The specific hip joint protection principles that are analyzed are loss of body weight, walking with an antalgic limp, the use of a cane, proper methods of load carriage, and the reasons for certain orthopedic surgeries. The reduction of these myogenic hip joint forces for the patient with a painful hip and/or hip with arthritis should be considered an important component of the clinical management of the hip.

Five month in vivo measurement of hip joint forces

Five month in vivo measurement of hip joint forces

A comparison of hip joint forces in sheep, dog and man

The hip joint forces of sheep and dogs were measured with instrumented endoprostheses and the results were compared with reported data concerning these forces in man. In all animals load directions with 0 to 30° inclinations relative to the femoral axis predominated. The transverse components mostly acted from medio-ventral directions. While the force orientations varied little during each single stance phase, they changed rapidly during the swing phase. Strong inter-and intra-individual differences of load directions were found in all animals. Irregular forces, acting upwards or transverse to the femur, were frequently observed. Maximum joint forces were up to 110% of body weight and depended more on the postoperative time than on the walking speed. Load orientations in the animals were similar to those reported for man. In this regard sheep and dogs appear equally well suited for tests of hip endoprostheses for man.

ヒトの随意運動にみられる筋活動電位の抑制現象に関する研究第II報 2関節同時運動時,二関節筋に現われる抑制現象について

Electrical silence which appeared in bifunctional leg muscles during simultaneous hip and knee extensions under isometric condition was investigated in terms of the neurophysiological and dynamical features in the biarticular movement.Subjects employed in the experim ents were healthy adult males ranging in age from 19 to 40, and they have no special training experiences for sports activity. Experimental posture was supine with both hip and knee joints kept at 90 degree angles. Electromyograms (EMGs) were recorded by conventional method using surface electrodes.Part 1. Electrical inhibition in the bifunctional knee extensor during simultaneous extensions of hip and knee jointsSimultaneous hip and kn ee extensions were performed along two distinctly different functional force directions, so that the resultant force output was limited by the hip joint force in one direction, and by the knee joint force in another. EMGs were recorded from the Rectus lemons (Rf), the Vastus medialis (Vm) and the Semimembranosus (Sm), and potentials evok ed by the patella tendon jerk were recorded from the Rf and the Vm. The total leg extension force exerted at the sole and the mechanical impact of the tendon tapping were recorded simultaneously with the EMGs and the evoked potentials.When the total leg extension force was limited by the hip extension force, the amplitude of the evoked potential from the Rf decreased while the leg extension force gradually increased. The Sm showed a marked discharge in this case. The results obtained in the experiment suggested that there was an inhibitory input to the a-motoneurone pool innervating the Rf, and this was probably due to an antagonistic inhibition induced by the increased activity in the hamstring muscles like the Sm. When the total leg extension force was limited by the knee extension force, the evoked potential from the Rf remained unchanged, and no discharge was observed in the Sm. The amplitude of the evoked potential from the Vm tended to increase with the increases in the resultant leg extension forces exerted along both functional force directions. Thus, the appearance of the electrical inhibition in the Rf was depending on whether or not the hip joint force was limiting the resultant leg extension force.Part 2. Electrical inhibition in bifunctional muscles and its effects on recruitment of monofunctional muscles during voluntary biarticular leg movementDischarges of the hip extensors, the Gluteus maximus (Gm), the Adductor magnus (Am), the Biceps femoris (Bf), the Semitendinosus (St) and the Sm, and those of the knee extensors, the Vm, the Vastus lateralis (Vl), the Rf and the Tensor fasciae latae (Tfl) were integrated through the Miller Circuit and recorded with their raw EMGs. A constant load (60 max.)was applied isometrically at the distal end of the thigh against the hip extension during application of graded load (10∼60% max. ) at the ankle joint against the knee extension (Exper.1). A constant load (60% max. ) was applied against the knee extension, and graded loads (10∼60% max.) were applied against the hip extension (Exper.2). Individual hip extension (Exper.3-A) and knee extension (Exper.3-B) were performed against constant loads (60%max.) as references to the Expers.1 and 2.Although the constant load was applied against the hip extension, the integrated EMGs (IEMGs) of the bifunctional hip extensors of the Bf, the St and the Sm decreased with the increasing load against the knee extension in the Exper.1. Also in the Exper.2, the IEMGs of the bifunctional knee extensors of the Rf and the Tfl decreased with the increasing load against the hip extension. These decreases in the IEMGs of the bifunctional muscles might be due to an antagonistic inhibition induced by the increase in activities of the antagonistic muscles.While the constant load was applied, the monofunctional agonistic extensors of the Vm and the Vi increased their activities.

Of men and sheep — Comparison of their hip joint forces

Of men and sheep — Comparison of their hip joint forces

A new approach towards hip-prosthesis design.

A new femoral prosthesis with a stemless design, different from conventional types, has been conceived in an effort to preserve the physiological stress distribution in magnitude and direction within the living bone as far as possible. The most important feature is that the hip joint forces are transmitted directly to the cortical bone of the resected femoral neck by means of a thrust plate, which maintains the physiological stress an the proximal end of the femur. The prosthesis, the instruments required for its implantation and the surgical technique are described in detail. Up to now, 3 patients have received this new prosthesis.

Direct measurement of hip joint forces in sheep

Direct measurement of hip joint forces in sheep

Reconstruction of the hip. A mathematical approach to determine optimum geometric relationships.

The normal mechanical function of the hip is substantially altered by a variety of disorders. The surgical treatment of such conditions, particularly total hip replacement, offers the opportunity not only to replace the articular surfaces of the joint, but also to improve long-term mechanical function by reducing the loads on the joint. A mathematical model of the hip was developed to evaluate the effects of such surgically achievable mechanical alterations as acetabular placement, femoral shaft-prosthetic neck angle, neck length of the femoral prosthesis, and transfer of the greater trochanter. The loads on the hip were lowered significantly by placing the center of the acetabulum as far medially, inferiorly, and anteriorly as was anatomically feasible. Minimum joint contact forces occurred when the femoral shaft-prosthetic neck angles were small, while the minimum moments about the prosthesis stem-neck junction were found when the angles were 130 to 140 degrees. A neck length of the femoral prosthesis of thirty-five millimeters resulted in moments that were lower than those for a neck length of forty-five millimeters. Lateral transfer of the greater trochanter reduced hip-joint forces and moments but distal transfer had little mechanical effect.

A photoelastic study of a model of the proximal femur. A biomechanical study of unstable trochanteric fractures I.

In attempt to standardize an experimental model for biomechanical studies of unstable trochanteric fractures, acrylic models of the proximal femur were investigated by the photoelastic technique. By matching the stress distribution in the acrylic models to those calculated by Pauwels, it was found that the optimal femoral shaft and resultant hip joint force angles were 5 degrees and 6 degrees to the vertical, respectively. The abductor muscle pull was determined to be 55 per cent of the resultant hip joint force at 15 degrees medial inclination to the vertical.

Total Replacement of the Elbow Joint

Biomechanical factors that are important in reconstructive procedures of the hip have been presented. The significance of the lever arm system in reducing hip joint forces has been emphasized as well as restoration of leg length and normal physiological muscular tension.

A Three Dimensional Model For Sress DistributionIn The Hip Joint Articular Surface

The magnitude and direction of the resultant hip joint force are generally different in different body positions. Therefore the stress distribution in the hip joint is also affected. The aim of this work is to calculate the stress distribution in the hip joint articular surface for various directions and magnitudes of the resultant hip joint force. For this purpose a simple three-dimensional mathematical model of the hip joint is developed. The articular stress integrated over the weight bearing area yields the resultant hip joint force. The value of stress at the pole and coordinates of the pole are determined by solving this vector equation. It is shown that inclination of the resultant hip joint force with respect to the frontal plane of the body increases the maximal value of stress in the articular surface.