Biomedical subjects

M L Hull

Publications and source records attributed to M L Hull.

119 records · Page 7Linked to original sources

PubMed1980

A biomechanical model for actively controlled snow ski bindings.

Active control of snow ski bindings is a new design concept which potentially offers improved protection from lower extremity injury. Implementation of this concept entails measuring physical variables and calculating loading and/or deformation in injury prone musculoskeletal components. The subject of this paper is definition of a biomechanical model for calculating tibia torsion based on measurements of torsion loading between the boot and ski. Previous control schemes have used leg displacement only to indicate tibia torsion. The contributions of both inertial and velocity-dependent torques to tibia loading are explored and it is shown that both these moments must be included in addition to displacement-dependent moments. A new analog controller design which includes inertia, damping, and stiffness terms in the tibia load calculation is also presented.

Accidental Falls↗

PubMed1976

Fundamental considerations in ski binding analysis.

1. The static adjustment of a ski binding by hand or by available machines is only an adjustment and is neither a static nor a dynamic evaluation of the binding design. Bindings of different design with identical static adjustments will perform differently in environments in which the forces are static or dynamic. 2. The concept of binding release force is a useful measure of binding adjustment, but it is inappropriate as a criterion for binding evaluation. First, it does not direct attention toward the injury causing mechanism, strain, or displacement in the leg. Second, it is only part of the evaluation in dynamic problems. 3. The binding release decision in present bindings is displacement controlled. The relative displacement of the boot and ski is the system variable. For any specified relative displacement the binding force can be any of an infinite number of possibilities determined by the loading path. 4. The response of the leg-ski system to external impulses applied to the ski is independent of the boot-ski relative motion as long as the boot recenters quickly in the binding. Response is dependent upon the external impulse plus system inertia, damping and stiffness. 5. When tested under half sinusoidal forces applied to a test ski, all bindings will demonstrate static and impulse loading regions. In the static region the force drives the binding to a relative release displacement. In the impulse region the initial velocity of the ski drives the binding to a release displacement. 6. The transition between the static and impulse loading regions is determined by the binding's capacity to store and dissipate energy along the principal loading path. Increased energy capacity necessitates larger external impulses to produce release. 7. In all bindings examined to date, the transmitted leg displacement or strain at release under static loading exceeds leg strain under dynamic or impact loading. Because static loading is responsible for many injuries, a skier should be able to release his bindings in every mode by simply pulling or twisting his foot outward. If that cannot be done without injury, the skier has identified for himself one type of fall that will result in injury. 8. And lastly, a little advice from Ben Franklin--"Carelessness does more harm than a want of knowledge."

Athletic Injuries↗

PubMed1975

Pulse code modulation telemetry in ski injury research. II. Preliminary results.

The excitation between the boot and the ski was measured in maneuvers skied over a variety of snow conditions. A precision pulse-code modulation (PCM) - frequency modulation (FM) telemetry system was custom built to transmit data from strain-gage force transducers mounted inside the test ski to a receiving station about 3 km distant. Field tests gathered cruising data from three basic maneuvers - snowplow, stem christiana, and parallel christiana. Some classic falls resulting from inadvertent release of the ski bindings were also recorded. For comparative purposes, the maneuvers were skied over a standard five-turn slalom course. Examination of the loading histories reveals that: (1) the data are nonstationary random; (2) boot compression for the test binding system exceeds 500 N and is caused by ski flexure; (3) an 80 Hz resonance of the particular toe binding mechanism is excited; (4) combined impulsive loading is significant; (5) the loading is related to the maneuver type; (6) bending components during forward falls exceed the tibia flexural strength even though heel binding release occurs at the laboratory setting, and (7) torsion and bending components exceed tibia fracture levels during elementary ski maneuvers.

Athletic Injuries↗

PubMed1974

Pulse code modulation telemetry in ski injury research. I. Instrumentation.

Measurement problems can be classified into instrumentation, data transmission and recording, and analysis. This paper focuses on the transmission of multichannel, high-volume, high-frequency, high-accuracy data. Boot-ski dynamometer and skier velocity anemometer data provide 13 channels of max. 8-mV signals requiring 8-microvolt resolution or 4.45-Newton dynamometer resolution. The data transmission system features durability, power consumption approx. 10 Watts, weight 4.54 kp, range greater than 3,500 m, frequency response 250 Hz, accuracy 1 per cent, temperature stability, dynamic range plus or minus 2 inches. The transducer signals are ampflified to plus or minus 10 V for the 100-kbps PCM system. Special AC amplifiers, driven by an amplitude-stabilized power oscillator, were designed for elimination of radio frequency interference (RFI), improved stability and high signal/noise. Sixteen words are sequentially sampled at 521/sec-13 data, 2 frame counters, and 1 sync. The ground station consists of the PCM decoder with real-time capability and an analog tape recorder. Data is subsequently buffered and formatted onto digital tape by mini-computer.

Athletic Injuries↗

PubMedDate not supplied

Contact mechanics of the medial tibial plateau after implantation of a medial meniscal allograft. A human cadaveric study.

The goal of this study was to determine how well a medial meniscal allograft restores the normal contact mechanics of the medial tibial plateau at the time of implantation. We measured maximum pressure, mean pressure, and contact area of the intact human cadaveric knee, the knee after meniscectomy, the knee with the original meniscus removed and reimplanted as an autograft, and the knee with an allograft. Measurements were made using pressure-sensitive film in 10 specimens loaded in compression to 1000 N at 0 degrees, 15 degrees, 30 degrees, and 45 degrees of flexion. The autograft and the allograft were identically implanted by cementing bone plugs attached to the meniscal horns in anatomic transtibial tunnels and suturing the outer edge of the meniscus to the remnant of the original meniscus. A medial meniscal allograft did not consistently restore normal contact mechanics because the process of implantation and the degree of match between the original and allograft meniscus affected the immediate load-bearing performance of the transplant. However, the allograft did significantly reduce the contact pressure compared with the knee after meniscectomy. If the results from this study can be extrapolated to patients, then using an allograft to restore contact mechanics to normal may require improvements in surgical technique and graft selection.

Adult↗

PubMedDate not supplied

Analysis of skiing accidents involving combined injuries to the medial collateral and anterior cruciate ligaments.

Two types of ligament injuries common in skiing are the isolated ruptures of the anterior cruciate and ruptures of the medial collateral, either with or without rupture of the anterior cruciate. Based on research related to ligament injury mechanics and two-mode release binding function, the purpose of this paper was to critically assess the ability of two-mode release bindings to prevent combined medial collateral and anterior cruciate ligament injuries. Making this assessment entailed several steps. First, I determined the loads typically transmitted by the knee during falls in which combined injuries occurred. Because more than one load was transmitted, the next step was to discern which of the loads was more damaging. Finally, heel-toe type bindings were evaluated for their potential to release in response to damaging loads. I concluded that combined medial collateral and anterior cruciate ligament injuries typically occur in forward, twisting-type falls in which the primary loads are external axial and valgus moments. An external axial moment is more damaging than a valgus moment, both to the medial collateral ligament when the joint is intact and to the anterior cruciate ligament when the medial collateral ligament is damaged. Because heel-toe type bindings offer release sensitivity to this moment, the release level of the toepiece in twist is an important factor in the prevention of these injuries.

Accidents↗

PubMedDate not supplied

Structural properties of six tibial fixation methods for anterior cruciate ligament soft tissue grafts.

This study compared the stiffness (K), yield load (YL), and slippage (SL) of six tibial fixation methods. These properties were determined from load-to-failure and cyclic tests of double-looped tendon grafts fixed to both animal and young human tissue. Tandem washers (K = 259 N/mm, YL = 1159 N, SL = 0.5 mm) and the Washerloc (K = 248 N/mm, YL = 905 N, SL = 2.0 mm) were the two best fixations. At 500 N of load, which is the estimated daily tension of an anterior cruciate ligament graft during intensive rehabilitation, slippage was significantly greater in either of the other two methods for sutures tied to a post (4.9 mm), double staples (3.3 mm), and a 20-mm spiked metal washer (3.5 mm). Interference screw fixation performed well in animal tissue (YL = 776 N), but was significantly worse in young human tissue (YL = 350 N), with 57% of the fixations failing before 500 N of load. Animal tissue should not be used to estimate the performance of interference screw fixation in human tissue. Because 57% of the interference screw fixations using human tissue failed at loads below 500 N, their ability to provide adequate fixation during intensive rehabilitation should be questioned. However, both the Washerloc and tandem washers and screws provide fixation structural properties in young human tibia that should be appropriate for intensive rehabilitation.

Adolescent↗

PubMedDate not supplied

Evaluation of the single-incision arthroscopic technique for anterior cruciate ligament replacement. A study of tibial tunnel placement, intraoperative graft tension, and stability.

The tension in an anterior cruciate ligament graft may not be normal when the femoral tunnel is placed using the single-incision arthroscopic technique because the femoral tunnel is drilled through the tibial tunnel. We hypothesized that the in vivo tensile behavior of the double-looped semitendinosus and gracilis tendon graft can be normal or abnormal compared with the native anterior cruciate ligament, that the placement and angle of the tibial tunnel can predict the tensile behavior of the graft, that the graft with abnormal tensile behavior is associated with a nonanatomically placed tibial tunnel, and that the tensile behavior of the graft determines the stability of the reconstructed knee at 1 year. Total tension in the graft and knee flexion angle were measured in 14 subjects as the knee was flexed from 0 degree to 90 degrees. A graft force greater than 40 N at 80 degrees of flexion was considered abnormal. One year after surgery, the angle and position of the tibial tunnel were determined from roentgenograms, and knee stability was measured with a KT-1000 arthrometer. The criteria for anatomic tibial tunnel placement in the sagittal and coronal planes were derived from magnetic resonance images of uninjured knees. The tensile graft behavior was either normal (4 of 14) or abnormal (10 of 14) with the single-incision arthroscopic technique. The angle of the tibial tunnel in the coronal plane was predictive of abnormal tensile behavior. Abnormal tensile behavior occurred in anatomically placed tibial tunnels and was compatible with a stable and functional reconstructed knee at 1 year.

Adolescent↗

PubMedDate not supplied

How three methods for fixing a medial meniscal autograft affect tibial contact mechanics.

We evaluated three methods for fixing a medial meniscal autograft to determine which method restored tibial contact mechanics closest to normal. The contact mechanics (maximum pressure, mean pressure, contact area, and location of the center of maximum pressure) of the medial tibial articular surface were determined using pressure-sensitive film while knee specimens were loaded in compression to 1000 N at 0 degree, 15 degrees, 30 degrees, and 45 degrees of flexion. Pressure was measured for the intact knee, the knee after meniscectomy, and the knee with the original meniscus removed and reimplanted as an autograft using three different fixation methods. The contact mechanics of the autograft reinserted with bone plug fixation were closest to normal; however, the maximum pressure was significantly greater than in the intact knee. Adding peripheral sutures neither improved nor worsened the contact mechanics. Fixation with sutures only did not restore normal contact mechanics. We concluded that medial meniscal transplantation requires anatomic fixation of bone plugs attached to the anterior and posterior horns to restore contact mechanics closest to normal. Fixation of the meniscal horns with sutures alone cannot be recommended.

Adult↗

PubMedDate not supplied

Review of spiritual health: definition, role, and intervention strategies in health promotion.

PURPOSE OF THE REVIEW. Recognition of the spiritual dimension as a vital component of human wellness has led to an increased interest in spirituality education, yet very little progress has been made in identifying possible intervention methods for enhancing spirituality. The purpose of this article is to review current definitions of spiritual health; provide an overview of several successful intervention methods that may enhance spiritual health; and outline potential relationships between spiritual health interventions and behavioral, emotional, and physical health outcomes. SEARCH METHOD USED. Research and review articles were identified through a CD-ROM computer search of ERIC (1966 to 1994), PSYCHLIT (1974 to 1994), and MEDLINE (1991 to 1994) databases using appropriate key words. Cumulative indexes from Advances (1984 to 1993) were manually searched, and reference lists from identified studies and literature reviews were analyzed. A total of 71 articles were identified and considered. Model interventions were chosen for presentation on the basis of soundness of research design, peer-review publication, clear description of intervention method, and relationship to spiritual health components. SUMMARY OF IMPORTANT FINDINGS. Imagery, meditation, and group support activities may address various components of spiritual health such as meaning and purpose in life; self-awareness; and connectedness with self, others, and a larger reality. In turn, positive changes in health behaviors such as communication, diet activity, and treatment compliance were noted, and a variety of beneficial physical and emotional health outcomes such as heart disease reversal, decreased cancer mortality, reduced anxiety, and improved mood states were reported. MAJOR CONCLUSIONS. Health educators are in a position to develop, implement, and evaluate spiritual health interventions within the context of comprehensive programs. There is a need for training in the theoretical and methodologic foundations of interventions like meditation, imagery, and group support and a need for more evaluation research in the impact of such interventions.

Complementary Therapies↗

PubMedDate not supplied

An instrumented brace for study of Legg-Calve-Perthes disease.

The accepted clinical method for treating children with Legg-Calve-Perthes disease is by means of abduction bracing. To evaluate the effectiveness of this method, one major necessary step is solving the three-dimensional inverse dynamics problem for the intersegmental loads at the hip joint. In order to provide part of the external loading data on the lower limb required to solve this problem, an instrumented abduction brace has been designed. The instrumented brace duplicates the mechanical behavior of the Scottish Rite Atlanta treatment brace, currently a clinically popular device. Instrumentation of the actual Atlanta brace was not considered, since its complicated mechanism couples forces applied by the brace to the thighs, resulting in moments difficult to measure. The new design eliminates all moments and simply applies one single force to the center of the femur. This single force is measured by a strain gage dynamometer. To assess the utility of the instrumented brace, the brace was fitted to three test subjects and the brace force was recorded while children walked through multiple trials. Testing of the brace demonstrates that it can be considered a dependable tool in studying the mechanical interactions between the brace and patient.

Braces↗