Arthur Steindler and orthopaedic research.
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Austria↗
Biomedical subjects
R A Brand
Publications and source records attributed to R A Brand.
Mechanoreceptors in joint function.
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Anterior Cruciate Ligament↗
Testing the daily stress stimulus theory of bone adaptation with natural and experimentally controlled strain histories.
Theories of bone adaptation generally consider that a departure in some feature of the normal homeostatic mechanical stimulus governs mechanical adaptation. Specifically, the 'daily stress stimulus' theory commonly used in computational models of bone adaptation suggests that the mechanical stimulus arises from a synthesis of the peak magnitudes from each loading event during a day. In this study, the homeostatic daily strain history of the adult turkey ulna was established by categorizing and counting the natural wing activities of adult male turkeys over a full 24h period. Strain signals were recorded in vivo for each activity type at three mid-diaphysis sites using stacked rosette strain gages. Following surgical isolation and transverse metaphyseal pinning of the ulnae, additional strain signals were recorded during controlled axial and torsional loading regimens associated with documented maintenance, loss, or addition of bone mass. When the present data were incorporated into the daily stress stimulus formulation, the theory did not consistently discriminate maintenance versus formation regimens, i.e., some maintenance regimens were associated with a substantially higher daily stimulus than some regimens causing bone formation.
Adaptation, Physiological↗
Pelvic muscle and acetabular contact forces during gait.
Locations, magnitudes, and directions of pelvic muscle and acetabular contact forces are important to model the effects of abnormal conditions (e.g., deformity, surgery) of the hip accurately. Such data have not been reported previously. We computed the three-dimensional locations of all pelvic muscle and acetabular contact forces during level gait. The approach first required computation of the intersegmental joint resultant forces and moments using limb displacement history, foot-floor forces, and estimated limb inertial properties from one subject. The intersegmental resultant moments were then distributed to the muscles using a 47-element muscle model and a non-linear optimization scheme. Muscle forces were vectorally subtracted from the intersegmental resultants to compute the acetabular contact forces. While the peak joint force magnitudes are similar to those reported previously for the femur, the directions of pelvic contact forces and muscle forces varied considerably over the gait cycle. These variations in contact force directions and three-dimensional forces could be as important as the contact force magnitudes in performing experimental or theoretical studies of loads and stresses in the periacetabular region.
Acetabulum↗
Sensory innervation of the cat knee articular capsule and cruciate ligament visualised using anterogradely transported wheat germ agglutinin-horseradish peroxidase.
Wheat germ agglutinin-horseradish peroxidase conjugate (WGA-HRP) was injected into the dorsal root ganglia (L5-S1) of the cat and used as an anterograde tracer substance for intra-axonal labelling of peripheral nerve endings in joint capsule and cranial (anterior) cruciate ligament (CCL). We believed that the high specificity of WGA-HRP for neural tissue along with the high visibility of its reaction product could help resolve controversies concerning the sensory innervation of the cruciate ligaments. Substantial amounts of WGA-HRP were transported in tibial nerve axons to the level of the knee. However, using standard HRP histochemistry we found that the capsular tissue and ligament synovia disintegrated during the incubation reaction. This problem was avoided by air drying the tissue slices on glass slides prior to reaction. Abundant labelling occurred in the posterior capsule with dense filling of axons and terminal endings. Sensory endings displayed features consistent with Ruffini endings and pacinian corpuscles. Sensory endings were located throughout the CCL in its sagittal plane, in the subsynovial layers and between collagen fascicles. In each CCL we observed 5-17 ovoid and elongated endings with dense terminal arborisations. These endings were between 100 and 150 microns long, were encapsulated, and gave rise to 1 or 2 axons. Large (up to 1.5 mm in maximum extent) elongated regions of dense, inhomogeneous labelling were found in the body of several CCLs. These resembled Golgi tendon-like endings, with the exception of their large size. We conclude that anterograde transport of HRP to the knee is a useful technique for labelling mechanoreceptors and axons in knee tissue. However, recently developed immunohistochemical analysis of peripheral tissue using protein gene product 9.5 appears to be the method of choice and should be employed for further study of human and animal cruciate ligament innervation.
Animals↗
Popliteus function in ACL-deficient patients.
Anterior cruciate ligament (ACL) injuries commonly result in anterolateral rotary instability and a 'pivot shift' phenomenon. Since popliteus muscle stimulation causes a pivot shift, some postulate the popliteus muscle plays a role in causing pivot shifts. To see if patients with pivot shifts exhibited excessive popliteus muscle activity, we studied fine-wire EMGs of the popliteus in 16 normal subjects and 10 ACL-deficient subjects. Subjects performed six activities (level walking and jogging, ascending walking and jogging, and descending walking and jogging). Except for minor timing differences in ascending treadmill and ascending jogging, the signals were similar for injured and uninjured limbs; similar variance ratios suggested similar pattern variability. Thus, we observed only minor popliteus EMG signal differences in this group of patients. We conclude that the popliteus muscle does not actively contribute to instability in the studied activities.
Anterior Cruciate Ligament Injuries↗
A cell strain system for small homogeneous strain applications.
A cell culture system has been developed that enables application of well characterized, homogeneously distributed cyclic strains to monolayer cell cultures. Optically clear silicone culture dishes atop Plexiglas base plates are deformed by four-point bending of flexible silicone culture wells driven in user specified strain cycle patterns using computer controlled electromagnetic linear actuators. Cyclic mechano-transduction can be induced in amplitudes of 0 to 3000 mustrain, in frequencies of 0 to 30 Hz and in any specified strain cycle pattern. The cell culture system, which contains six simultaneously driven culture wells, has been mechanically characterized by holographic interferometry, laser displacement sensor recordings of the dish surfaces, strain gauge monitoring of the base plates, and finite element modeling of the dishes on the base plates. The standard deviation of the strain amplitudes among the six simultaneously stimulated culture wells is less than 5%. The cell culture system allows accurate generation of small magnitudes of well characterized, homogeneous strain, easy handling of the culture wells, flexible setting of cyclic strain pattern parameters, simultaneous stimulation of 6 culture wells, and light microscopic observation of the cell cultures.
Animals↗
What do tissues and cells know of mechanics?
Many tissues and cells adapt to their mechanical environment, i.e. the stresses and strains to which the tissues are exposed during daily activities. Simple mechanical explanations of such adaptation naturally provide appeal, yet fail to predict accurately tissue appearance and behaviour. Continuum mechanics, the field from which our concepts of stress and strain arise, assumes a solid continuous structure, an assumption that does not apply at cell level. Merely correlating a given stress or strain magnitude with tissue behaviour does not per se account for the time over which responses occur. Tissues undoubtedly 'temporally process' mechanical signals, responding to some portion of the mechanical environment, and ignoring others. Further, the deformation that cells experience will depend upon their nonrigid connections to the matrix, so that the strains in the tissue may not be those experienced by the cell (and those causing the adaptation). Relatively simple mechanical models incorporating temporal features may adequately predict tissue adaptation, but the noncontinuum nature of tissues suggests that such models cannot adequately explain either tissue adaptation or the responses leading to adaptation.
Adaptation, Physiological↗
Quantifying osteoarthrotic hip incongruence. An approach to optimizing osteotomies.
Osteoarthrosis of the hip may be treated by osteotomy, but surgeons report variable results, and there is no consensus regarding which method to use in choosing the type of osteotomy. The authors defined three biomechanical measures of hip incongruence (characteristic point locus, joint space, and contact region) and developed a two-dimensional frontal plane model to compute joint incongruence over the joint range of motion during normal activities of daily living. The preoperative measures were calculated for 38 patients who had undergone osteotomy at least 5 years earlier. The authors calculated the measures throughout a functional range of motion after 13 stimulated varus or valgus osteotomies. A logistic regression analysis determined which, if any, of the three measures, in conjunction with other clinical variables, correctly predicted outcome. The average values for the characteristic point locus, joint space, and contact region measures ranged from 0.260 cm to 2.127 cm, 0.963 cm2 to 9.327 cm2, and 0.063 cm to 4.230 cm, respectively. Unimodal behavior between two of the three measures (joint space and contact region) and osteotomy angle were observed, suggesting these two would be the most useful in predicting an optimal osteotomy. The most significant independent variable predicting clinical outcome was the joint space measure. This supports the potential of an optimization approach for determining the best angle for a hip osteotomy.
Acetabulum↗
Effects of anisotropy and material axis registration on computed stress and strain distributions in the turkey ulna.
Finite element stress and strain distributions were studied parametrically for a curved long bone using several common material simplifications. A new technique is presented whereby local material axes conforming to local surface topology were automatically computed. Linearly elastic stress/strain solutions were evaluated as a function of the manner in which principal material directions are defined. The simplifications inherent in assumptions of local isotropy or globally registered transverse isotropy led to appreciably different solutions, particularly for some of the lesser-magnitude components of the strain tensor.
Algorithms↗
The sensitivity of joint afferents to knee translation.
The cruciate ligaments contain mechanoreceptors which putatively contribute to knee function and dysfunction. However, the interpretation of studies showing neural responses to traction loads applied to the cat cranial cruciate ligament (CCL analogous to the anterior cruciate ligament in humans) depends upon demonstrating that non-CCL periarticular receptors are not stimulated. We assessed the capability to rigidly fix the knee against traction loads applied to the feline CCL. The tibia and femur were fixed either with clamps or Steinmann pins. Motion of the bones was monitored with liquid metal strain gages (LMSG) and the activity of the posterior articular nerve (PAN) was recorded while traction loads of up to 20-30 N were applied to the CCL. Joint afferents recorded from the PAN were insensitive to the CCL loads in the rigidly fixed preparation. Motion of the proximal tibia and distal femur was less than 100 micrometers for both methods of fixation, with neither method demonstrating more rigid fixation. In contrast, we observed vigorous discharges with focused light pressure on the capsule and under conditions allowing 200-500 micrometers of tibial displacement on the femur. This suggests that clinically undetectable instability may give rise to aberrant mechanoreceptor activity contributing to dysfunction.
Afferent Pathways↗
Effects of leg length discrepancies on the forces at the hip joint.
The authors questioned whether leg length discrepancies of the magnitude ordinarily seen after total hip reconstruction (<2 cm) would substantially alter hip joint forces. Using conventional gait analysis techniques to ascertain intersegmental resultant hip forces and moments, the authors used lifts to simulate leg length discrepancies of 2.3, 3.5, and 6.5 cm in 7 normal subjects. The 2.3-cm lift produced no changes. On the side of the lift (long limb), the 3.5- and 6.5-cm lifts modestly decreased mean peak intersegmental resultant hip forces by 6% and 12%, respectively, but not moments. The changes were, however, variable, with a few subjects showing increases and the rest showing decreases in selected forces or moments. On the side opposite to the lift (short limb), the 3.5- and 6.5-cm lifts increased mean peak intersegmental resultant hip forces by 2% to 12%, but not moments except in 1 case (8%). It is concluded that leg length discrepancies of the sort commonly seen after total hip reconstruction would likely cause no substantial changes in hip forces.
Adult↗
Proliferative and phenotypic responses of bone-like cells to mechanical deformation.
Limited in vivo and in vitro experiments suggest that bone and bone-like cells respond to mechanical signals in a trigger-like rather than a dose-response fashion; i.e., they fail to respond until they have been stimulated with some given number of cycles of loading, and then once they respond, additional cycles produce little or no effect. To explore this notion, rat calvaria-derived osteoblast-like cells and the cell line MC3T3-E1 were plated at a high cell density (5,000 cells/mm2) on silicone membranes coated with type-I collagen and were allowed to attach for 24 hours. The membranes then were exposed to vacuum pressure (-1 kPa, 0.5 Hz) on a daily basis, and cultures were assayed every 2 days for 2 weeks. The proliferation of nontransformed cells increased 7-fold with as few as four daily cycles but not with one cycle per day. Furthermore, 1,800 cycles of vacuum did not result in a greater response than four cycles per day. We observed inverse phenotypic responses: the expression of osteocalcin was depressed compared with controls in the cultures of osteoblast-like cells that were strained with as few as four cycles per day. Alkaline phosphatase activity was depressed in the cultures of both the osteoblast-like cells and the MC3T3-E1 cells exposed to low vacuum pressures (-1 kPa) with four daily cycles of vacuum pressure. Increasing the vacuum magnitude did not affect the occurrence of a "trigger response" between one and four cycles of vacuum application.(ABSTRACT TRUNCATED AT 250 WORDS)
3T3 Cells↗
Three-dimensional geometric and structural symmetry of the turkey ulna.
Structural models of long-bone preparations usually assume left-right symmetry of contralateral bones under normal (baseline) conditions. To obtain insight on how this assumption affects the detection of subtle changes (as from functional adaptation), we formally examined the three-dimensional geometric and structural symmetry of paired long bones, using contemporary image reconstruction and stress analysis techniques. Nine pairs of ulnae from normal male turkeys were reconstructed computationally from serial transverse images obtained by either (a) mechanical sectioning and digital photographic imaging or (b) computed tomography. Computed tomography scans allowed greater precision in reconstruction than did digitally imaged photographs. Left-right comparisons of parameters of geometric symmetry (from computed tomography reconstructions) revealed average differences in whole bone volume and whole bone principal moments of inertia of 3.6 and 3.0%, respectively. Differences in bone curvature were indexed as noncolinearity of left compared with (mirrored) right centroidal axes, giving a disparity of 0.7 +/- 0.3 mm. Within the longitudinal central 20% of the diaphysis (the customary region for histomorphometry), average left-right differences in cross-sectional area and area principal moments of inertia for computed tomography images were 4.7 and 5.0%, respectively. The overlap of longitudinally paired cross sections of the mid-diaphysis, aligned at common centroids and oriented in the respective principal inertial directions, was greatest (as much as 95%) in the central 20% of the diaphysis. Paired three-dimensional finite element models demonstrated nearly identical left and right stress/strain fields throughout the ulnar diaphyses for both compressive and torsional loading. Our data suggest that the assumption of contralateral geometric symmetry in long bones should be judged in the context of the specific attribute of symmetry under consideration; however, we conclude that for purposes of finite element modeling the assumption of symmetry is reasonable.
Adaptation, Physiological↗
Cellular deformation reversibly depresses RT-PCR detectable levels of bone-related mRNA.
Osteoblastic cells respond to mechanical stimuli with alterations in proliferation and/or phenotypic expression. In some cases, these responses occur within only a few applications of stimuli (i.e. 'cycle-dependent trigger response') rather than in a dose-dependent manner. To explore potential mechanisms of the cycle dependent trigger response, we raised the following questions: (1) Does strain of bone cells alter gene expression; if so, how quickly does it occur and how long does it last? (2) Are alterations in message level strain magnitude dependent? (3) Are alterations in steady-state message levels cycle dependent? Cultures were evaluated for osteocalcin mRNA one week following a daily stretch application at four stretch magnitudes and four cycle numbers and compared to nonstretched controls. Steady state mRNA message was ascertained prior to and at 10, 20, 30, 60, 120, 180, and 240 min following initiation of stretch. Following mRNA isolation, first strand cDNA synthesis was performed and fluorometrically quantitated. A reverse transcriptase based PCR (RT-PCR) approach allowed assessment of osteocalcin mRNA levels from microcultures (50,000 cells per 10 microliters culture or 5000 cells mm2) of rat calvarial osteoblasts. Optimized PCR was performed using primers to the bone specific protein, osteocalcin (OC) and two 'housekeeping' genes, beta-actin and GAP-DH. PCR products were separated on 4% agarose gels and band intensities digitized with relative quantitation based on internal standards in each gel. The lowest magnitude of stretch (- 1 KPa) at 1800 cycles per day reproducibly depressed message for osteocalcin, but not beta-actin when assayed immediately following the cessation of strain application. By three hours following the initiation of stretch, message levels returned to control values. At the time of stretch cessation, the 1800 cycle stretch regimen diminished (p < 0.0001) steady-state osteocalcin message independently of the four stretch magnitudes. Stretch for 300 cycles failed to depress (p = 0.05) osteocalcin message cultures at any time, but 600 cycles depressed message by 30 min. By one and two hours, cultures stretch 600, 900, and 1800 cycles showed similar levels of message depression. Four hours following the initiation of stretch, message levels returning to nonstrained levels in all groups. We conclude that alterations in cell response to strain are in part mediated by gene expression, that alterations last 3-4 h in this system, and that the message mechanism itself exhibits a trigger-response dependency to cycle number.
Actins↗
Resection arthroplasty of the hip.
Forty-four patients with 46 resection arthroplasties performed for various indications were followed an average of 8.0 years. Pain relief was good or excellent in 77% and eradication of infection was achieved in all but one. Completeness of cement removal at the time of resection arthroplasty did not affect the results or control of infection. Patients with a history of prior septic total hip arthroplasty had results similar to those for patients with other indications for resection arthroplasty. A comprehensive review of the literature supports these results.
Activities of Daily Living↗
Characterisation of the neurosensory elements of the feline cranial cruciate ligament.
The identification and distribution of mechanoreceptors in the cranial cruciate ligament of the cat (analogous to the anterior cruciate ligament in other species) was studied histologically using a modified celloidin embedding technique to achieve serial sectioning of bone-ligament-bone preparations with gold chloride staining. We identified distinctive large elongated structures situated between the collagen bundles of the ligament (resembling endings described as Freeman and Wyke type III; also termed Golgi tendon receptors). These endings were found near the middle of the ligament well away from the bone-ligament junction. Axons seen entering only one end of each type III ending helped to confirm its neural basis. While we saw structures resembling types I and II endings (i.e. Ruffini and pacinian endings, respectively) in individual sections, serial sections failed to reveal convincing evidence of their existence. Such structures almost always appeared to be vascular in nature on adjacent sections, with vessels entering and exiting. We conclude that serial sections are critical to interpreting the presence or absence of mechanoreceptors.
Animals↗