Hip joint forces in sheep.

Testing orthopaedic implants at the proximal femur of sheep requires knowledge of the contact forces acting on this joint. Telemeterized implants were used for long-term measurements of these forces in four sheep, mostly during treadmill walking. Joint forces in the same sheep varied widely from day to day and interindividual differences were also pronounced. Forces during walking were mostly higher than in previous short-term measurements. At medium walking speed, loads in the range of 65-140% of the body weight were typical. Fast walking increased the forces by only 20%, compared to slow speed. Stomping on the ground at the beginning of the stance phase and starting to run freely led to very high forces. The highest values observed were nearly four times the body weight. As in humans, the directions of high forces varied only slightly in the frontal plane throughout the whole stance phase but much more in the transverse plane. With regard to the force magnitudes and their directions, sheep seem to be a good model for testing human implant at the proximal femur.     

Chromosome studies in four species of Ratitae (Aves)

Chromosomes were studied in female specimens of the ostrich, Struthio camelus L., cassowary, Casuarius casuarius (L.), emu, Dromiceius novaehollandiae (Lath.) and rhea, Rhea americana L. by means of blood and feather pulp culture techniques. Male karyotypes were also studied in the emu and rhea. The diploid chromosome number was most likely 80 in the ostrich and rhea and 82 in the emu, while the exact number could not be determined in the cassowary. Karyotypes of the 4 species were strikingly similar and apparently interchangeable with one another with slight modifications of the centromeric position in one or two pairs of macrochromosomes. No heteromorphic macrochromosomal pair was found either in female specimens or in male ones of the ratite species so far examined, except for a female rhea. This specimen was found to possess an acrocentric chromosome which was evidently a member of nos. 4–6, but considerably smaller than any other chromosome of the group. ³H-thymidine autoradiography provided no more information than the straightforward morphological analysis with regard to the differentiation of the sex-chromosomes.Contributions from the Chromosome Research Unit, Hokkaido University. Dedicated to Emeritus Professor Sajiro Makino on the occasion of his retirement, in honor of his 40 years' service with the University. Supported by a grant from the Scientific Research Fund of the Ministry of Education (No. 584099).     

Hip joint replacement surgery for idiopathic osteoarthritis aggregates in families

In order to determine whether there is a genetic component to hip or knee joint failure due to idiopathic osteoarthritis (OA), we invited patients (probands) undergoing hip or knee arthroplasty for management of idiopathic OA to provide detailed family histories regarding the prevalence of idiopathic OA requiring joint replacement in their siblings. We also invited their spouses to provide detailed family histories about their siblings to serve as a control group. In the probands, we confirmed the diagnosis of idiopathic OA using American College of Rheumatology criteria. The cohorts included the siblings of 635 probands undergoing total hip replacement, the siblings of 486 probands undergoing total knee replacement, and the siblings of 787 spouses. We compared the prevalence of arthroplasty for idiopathic OA among the siblings of the probands with that among the siblings of the spouses, and we used logistic regression to identify independent risk factors for hip and knee arthroplasty in the siblings. Familial aggregation for hip arthroplasty, but not for knee arthroplasty, was observed after controlling for age and sex, suggesting a genetic contribution to end-stage hip OA but not to end-stage knee OA. We conclude that attempts to identify genes that predispose to idiopathic OA resulting in joint failure are more likely to be successful in patients with hip OA than in those with knee OA.     

Hip joint replacement surgery for idiopathic osteoarthritis aggregates in families

In order to determine whether there is a genetic component to hip or knee joint failure due to idiopathic osteoarthritis (OA), we invited patients (probands) undergoing hip or knee arthroplasty for management of idiopathic OA to provide detailed family histories regarding the prevalence of idiopathic OA requiring joint replacement in their siblings. We also invited their spouses to provide detailed family histories about their siblings to serve as a control group. In the probands, we confirmed the diagnosis of idiopathic OA using American College of Rheumatology criteria. The cohorts included the siblings of 635 probands undergoing total hip replacement, the siblings of 486 probands undergoing total knee replacement, and the siblings of 787 spouses. We compared the prevalence of arthroplasty for idiopathic OA among the siblings of the probands with that among the siblings of the spouses, and we used logistic regression to identify independent risk factors for hip and knee arthroplasty in the siblings. Familial aggregation for hip arthroplasty, but not for knee arthroplasty, was observed after controlling for age and sex, suggesting a genetic contribution to end-stage hip OA but not to end-stage knee OA. We conclude that attempts to identify genes that predispose to idiopathic OA resulting in joint failure are more likely to be successful in patients with hip OA than in those with knee OA.     

Hip joint centre localisation with an unscented Kalman filter

The accurate estimation of the hip joint centre (HJC) in gait analysis and in computer assisted orthopaedic procedures is a basic requirement. Functional methods, based on rigid body localisation, assessing the kinematics of the femur during circumduction movements (pivoting) have been used for estimating the HJC. Localising the femoral segment only, as it is usually done in total knee replacement procedure, can give rise to estimation errors, since the pelvis, during the passive pivoting manoeuvre, might undergo spatial displacements. This paper presents the design and test of an unscented Kalman filter that allows the estimation of the HJC by observing the pose of the femur and the 3D coordinates of a single marker attached to the pelvis. This new approach was validated using a hip joint mechanical simulator, mimicking both hard and soft tissues. The algorithm performances were compared with the literature standards and proved to have better performances in case of pelvis translation greater than 8 mm, thus satisfying the clinical requirements of the application.     

Hip joint centre location: An ex vivo study

The human hip joint is normally represented as a spherical hinge and its centre of rotation is used to construct femoral anatomical axes and to calculate hip joint moments. The estimate of the hip joint centre (HJC) position using a functional approach is affected by stereophotogrammetric errors and soft tissue artefacts. The aims of this study were (1) to assess the accuracy with which the HJC position can be located using stereophotogrammetry and (2) to investigate the effects of hip motion amplitude on this accuracy. Experiments were conducted on four adult cadavers. Cortical pins, each equipped with a marker cluster, were implanted in the pelvis and femur, and eight skin markers were attached to the thigh. Recordings were made while an operator rotated the hip joint exploiting the widest possible range of motion. For HJC determination, a proximal and a distal thigh skin marker cluster and two recent analytical methods, the quartic sphere fit (QFS) method and the symmetrical centre of rotation estimation (SCoRE) method, were used. Results showed that, when only stereophotogrammetric errors were taken into account, the analytical methods performed equally well. In presence of soft tissue artefacts, HJC errors highly varied among subjects, methods, and skin marker clusters (between 1.4 and 38.5 mm). As expected, larger errors were found in the subject with larger soft tissue artefacts. The QFS method and the distal cluster performed generally better and showed a mean HJC location accuracy better than 10 mm over all subjects. The analysis on the effect of hip movement amplitude revealed that a reduction of the amplitude does not improve the HJC location accuracy despite a decrease of the artefact amplitude.     

Hip endoprosthesis for in vivo measurement of joint force and temperature.

Friction between the prosthetic head and acetabular cup increases the temperature in hip implants during activities like walking. A hip endoprosthesis was instrumented with sensors to measure the joint contact forces and the temperature distribution along the entire length of the titanium implant. Sensors and two inductively powered telemetry units are placed inside the hip implant and hermetically sealed against body fluids. Each telemetry unit contains an integrated 8-channel telemetry chip and a radio frequency transmitter. Force, temperature and power supply data are transmitted at different frequencies by two antennas to an external twin receiver. The inductive power supply is controlled by a personal computer. Force and temperature are monitored in real time and all data are stored on a video tape together with the patient's images. This paper describes the design and accuracy of the instrumented implant and the principal function of the external system components.     

An open source lower limb model: Hip joint validation

Musculoskeletal lower limb models have been shown to be able to predict hip contact forces (HCFs) that are comparable to in vivo measurements obtained from instrumented prostheses. However, the muscle recruitment predicted by these models does not necessarily compare well to measured electromyographic (EMG) signals. In order to verify if it is possible to accurately estimate HCFs from muscle force patterns consistent with EMG measurements, a lower limb model based on a published anatomical dataset (Klein Horsman et al., 2007. Clinical Biomechanics. 22, 239-247) has been implemented in the open source software OpenSim. A cycle-to-cycle hip joint validation was conducted against HCFs recorded during gait and stair climbing trials of four arthroplasty patients (Bergmann et al., 2001. Journal of Biomechanics. 34, 859-871). Hip joint muscle tensions were estimated by minimizing a polynomial function of the muscle forces. The resulting muscle activation patterns obtained by assessing multiple powers of the objective function were compared against EMG profiles from the literature. Calculated HCFs denoted a tendency to monotonically increase their magnitude when raising the power of the objective function; the best estimation obtained from muscle forces consistent with experimental EMG profiles was found when a quadratic objective function was minimized (average overestimation at experimental peak frame: 10.1% for walking, 7.8% for stair climbing). The lower limb model can produce appropriate balanced sets of muscle forces and joint contact forces that can be used in a range of applications requiring accurate quantification of both. The developed model is available at the website https://simtk.org/home/low_limb_london.     

Hip joint range of motion improvements using three different interventions

The purpose of this study was to analyze the effect of 3 different exercise interventions plus a control group on passive hip range of motion (ROM). Previous research studies into the methods of improving passive hip mobility have focused on stretching protocols aimed specifically at the hip joint. The effect of core stabilization, motor training, and myofascial stretching techniques on hip mobility in a selected asymptomatic group with limited hip mobility is unclear. In this study, 24 young men with limited hip mobility (<50th percentile) were randomly assigned to 4 groups: stretching, stretching with motor control exercises for the hip and trunk, core endurance with motor control exercises, and the control group. Six-week home exercise programs were individually prescribed based on the assigned group, hip ROM, movement patterns, and timed core endurance. Two-way analyses of variances were conducted to analyze the effect of group assignment on hip ROM improvements. Both stretching groups demonstrated significant improvements in hip ROM (p < 0.05), attaining hip mobility levels at or above the 75th percentile, with rotation improving as much as 56%. The group receiving core endurance and motor control exercises with no stretching also demonstrated a moderate increase in ROM but only significantly so in rotation. Average core endurance holding times improved 38-53%. These results indicate that stretches aimed at the myofascial components of the upper body, in addition to the hip joint, resulted in dramatic increases in hip ROM in a group of young men with limited hip mobility. Hip ROM also improved in the group that did no active stretching, highlighting the potential role of including stabilization or "proximal stiffening training" when rehabilitating the extremities.     

Hip joint moments in symptomatic vs. asymptomatic people with mild radiographic hip osteoarthritis

Our primary objective was to examine external hip joint moments during walking in people with mild radiographic hip osteoarthritis (OA) with and without symptoms and disease-free controls. Three groups were compared (symptomatic with mild radiographic hip OA, n = 12; asymptomatic with mild radiographic hip OA, n = 13; OA-free controls, n = 20). Measures of the external moment (peak and impulse) in the sagittal, frontal and transverse plane during walking were determined. Variables were compared according to group allocation using mixed linear regression models that included individual gait trials, with group allocation as fixed effect and walking speed as a random effect. Participants with evidence of radiographic disease irrespective of symptoms walked 14–16% slower compared to disease-free controls (p = 0.002). Radiographic disease without symptoms was not associated with any altered measures of hip joint moment compared to asymptomatic OA-free controls once speed was taken into account (p ≥ 0.099). People with both mild radiographic disease and symptoms had lower external peak hip adduction moment (p = 0.005) and lower external peak internal rotation moment (p < 0.001) accounting for walking speed. Among angular impulses, only the presence of symptoms was associated with a reduced hip internal rotation impulse (p = 0.002) in the symptomatic group. Collectively, our observations suggest that symptoms have additional mechanical associations from radiographic disease alone, and provide insight into potential early markers of hip OA. Future research is required to understand the implications of modifying walking speed and/or the external hip adduction and internal rotation moment in people with mild hip OA.     

Hip joint degeneration due to cam impingement: a finite element analysis

The goal of this study was to investigate the impact of cam impingement, a biomechanical risk factor, on hip joint degeneration and ultimately coxarthrosis. 3D finite element solid models of a healthy and a pathologic hip were developed based on clinical reports. The biphasic characteristics of cartilaginous tissues were considered to identify localised solid matrix overloading during normal walking and sitting down (SD). Localised femoral intrusion at the anterior-superior pelvic horn was revealed in the pathologic hip during SD, where the radial and meridional solid stresses in the acetabular cartilage and circumferential solid stresses within the acetabular labrum increased by 3.7, 1.5 and 2.7 times, respectively. The increased solid-on-solid stresses, reduction in fluid-load support and associated higher friction during articulation may result in joint wear and other degenerative changes in the hip.     

Hip joint contact force in the emu (Dromaius novaehollandiae) during normal level walking

The emu is a large, (bipedal) flightless bird that potentially can be used to study various orthopaedic disorders in which load protection of the experimental limb is a limitation of quadrupedal models. An anatomy-based analysis of normal emu walking gait was undertaken to determine hip contact forces for comparison with human data. Kinematic and kinetic data captured for two laboratory-habituated emus were used to drive the model. Muscle attachment data were obtained by dissection, and bony geometries were obtained by CT scan. Inverse dynamics calculations at all major lower-limb joints were used in conjunction with optimization of muscle forces to determine hip contact forces. Like human walking gait, emu ground reaction forces showed a bimodal distribution over the course of the stance phase. Two-bird averaged maximum hip contact force was approximately 5.5 times body weight, directed nominally axially along the femur. This value is only modestly larger than optimization-based hip contact forces reported in literature for humans. The interspecies similarity in hip contact forces makes the emu a biomechanically attractive animal in which to model loading-dependent human orthopaedic hip disorders.     

Hip and knee joint kinematics during a diagonal jump landing in anterior cruciate ligament reconstructed females

Anterior cruciate ligament (ACL) injury is a common injury encountered by sport medicine clinicians. Surgical reconstruction is the recommended treatment of choice for those athletes wishing to return to full-contact sports participation and for sports requiring multi-directional movement patterns. The aim of ACL reconstruction is to restore knee joint mechanical stability such that the athlete can return to sporting participation. However, knowledge regarding the extent to which lower limb kinematic profiles are restored following ACL reconstruction is limited. In the present study the hip and knee joint kinematic profiles of 13 ACL reconstructed (ACL-R) and 16 non-injured control subjects were investigated during the performance of a diagonal jump landing task. The ACL-R group exhibited significantly less peak knee joint flexion (P=0.01). Significant between group differences were noted for time averaged hip joint sagittal plane (P<0.05) and transverse plane (P<0.05) kinematic profiles, as well as knee joint frontal plane (P<0.05) and sagittal plane (P<0.05) kinematic profiles. These results suggest that aberrant hip and knee joint kinematic profiles are present following ACL reconstruction, which could influence future injury risk.     

Total Hip Replacement in Inflammatory Hip Disease using the Charnley Prosthesis

The Charnley low-friction arthroplasty was performed on 73 hips in 55 patients with inflammatory joint disease, usually for intolerable pain. Sixty-five of these operations were reviewed at a special clinic or by postal questionnaire; 57 hips were painfree or gave rise to only occasional discomfort, in 58 there was an increased range of movement, and in 46 of the 59 hips assessed clinically, the results were excellent or good. The most serious complication was deep infection, which occurred in 7 operations.     

Hip joint muscle forces during gait in patients with femoroacetabular impingement syndrome are associated with patient reported outcomes and cartilage composition

Femoroacetabular impingement syndrome (FAIS) consists of abnormal hip joint morphology and pain during activities of daily living. Abnormal gait mechanics and potentially abnormal muscle forces within FAI patients leads to articular cartilage damage. Therefore, there is a necessity to understand the effects of FAI on hip joint muscle forces during gait and the link between muscle forces, patient reported outcomes (PRO) and articular cartilage health. The purposes of this study were to assess: (1) hip muscle forces between FAI patients and healthy controls and (2) the associations between hip muscle forces with PRO and cartilage composition (T_1ρ/T₂ mapping) within FAI patients. Musculoskeletal simulations were used to estimate peak muscle forces during the stance phase of gait in 24 FAI patients and 24 healthy controls. Compared to controls, FAI patients ambulated with lower vasti (30% body-weight, p = 0.01) and higher sartorius (4.0% body-weight, p < 0.01) forces. Within FAI patients, lower peak gluteus medius, gluteus minimus, sartorius and iliopsoas forces were associated with worse hip joint pain and function (R = 0.43–0.70, p = 0–0.04), while lower muscle forces were associated with increased T_1ρ and T₂ values (i.e. altered cartilage composition) within the hip joint cartilage (R = −0.44 to −0.58, p = 0.006–0.05). Although FAI patients demonstrate abnormal muscle forces, it is unknown whether or not these altered muscle force patterns are associated with pain avoidance or weak musculature. Further investigation is required in order to better understand the effects of FAI on hip joint muscle forces and the associations with hip joint cartilage degeneration.