Vibration and induction of endothelial injury.
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Endothelium, Vascular↗
Biomedical subjects
M H Pope
Publications and source records attributed to M H Pope.
The measurement of anterior cruciate ligament strain in vivo.
This article describes the use of the Hall Effect strain transducer (HEST) in a new arthroscopic technique to study the normal anterior cruciate ligament (ACL) in-vivo. Study participants were patient volunteers with normal ACLs undergoing diagnostic arthroscopic or meniscal surgery under local anaesthesia. The HEST was implanted into the Anterior Medial Band (AMB) of the ACL. Anterior shear loading of the tibia in relation to the fixed femur at 30 degrees of knee flexion (Lachman test), produced significantly greater strain values in comparison to anterior shear loading at 90 degrees (Anterior Drawer test). During isometric quadriceps contraction a significant increase in AMB strain was measured with the knee flexed to 30 degrees, while no significant change was measured at 90 degrees. For quadriceps contraction there were significantly higher values of AMB strain measured at 30 degrees of knee flexion in comparison to that observed at 90 degrees. For active range of motion (AROM) the AMB was strained between 10 degrees and 48 degrees, and unstrained between 48 degrees and 110 degrees. During passive range of motion (PROM) the AMB remained unstrained until the joint was brought into extension. There were significant differences in strain values found between AROM and PROM at the flexion angles 10 degrees, 20 degrees, 30 degrees and 40 degrees, while between 50 degrees and 110 degrees there were no significant differences. These results confirm previous studies that the Lachman test is a superior technique in comparison to the classic anterior drawer test for evaluating the AMB. They suggest that isometric quadriceps activity at 90 degrees of knee flexion can be prescribed for rehabilitation immediately after ACL reconstruction. These data indicate that AROM (between the limits of 50 degrees and 110 degrees) and PROM may also be performed with minimal risk of strain to a reconstructive replacement. The PROM data may also serve as an important standard for the reconstruction of the ACL.
Adult↗
A method for the intravital measurement of interspinous kinematics.
A novel non-radiographic technique for objectively quantifying quasi-static or dynamic intervertebral motion of a spinal motion segment in vivo in human subjects is presented here. The intervertebral motion device (IMD) is an instrumented linkage transducer system which can continuously measure over time two-dimensional sagittal plane rigid-body motion. Three custom-built omega-shaped displacement transducers are utilized. The IMD is rigidly fixed to the spinous processes of the lumbar motion segment by means of two intraosseous pins. Knowing the mechanoelectrical behavior and geometric configuration of the IMD, the relative spatial motion between the vertebral bodies can be resolved into sagittal rotation, axial translation, and anterior-posterior shear translation. Static calibrations of the IMD in the ranges of +/- 4 degrees rotation and +/- 4 mm translation determined the absolute maximum errors to be 0.2 degree and 0.07 mm for rotation and translation measurements, respectively, with corresponding variances of 0.1 degrees and 0.03 mm. For use in the vibration environment, negligible motion artifact content was detected in the IMD output signals when excited at discrete frequencies of 5.0 and 8.0 Hz. The first natural frequency of the IMD, specific for this design, was measured at 16.25 Hz. This technique may be used to study in vivo the spinal kinematics in healthy lumbar motion segments and in patients suspected of having segmental instability, and can perhaps be of clinical diagnostic significance.
Bone Nails↗
The effect of functional knee-braces on strain on the anterior cruciate ligament in vivo.
Functional knee-braces are widely used to protect injured or reconstructed anterior cruciate ligaments, despite the fact that few scientific data support their efficacy. We studied seven functional braces, representative of both the typical custom-fit and off-the-shelf designs. The braces were tested on subjects who had a normal anterior cruciate ligament and were scheduled for arthroscopic meniscectomy or exploration of the knee under local anesthesia. After the operative procedure, a Hall-effect strain-transducer was applied to the anterior cruciate ligament. Under low anterior shear loads, two braces provided some protective strain-shielding effect compared with no brace, but this strain-shielding effect did not occur at the higher anterior shear loads expected during the high-stress activities common to athletic events. The DonJoy, Townsend, C.Ti., and Lenox Hill braces demonstrated a strain-shielding effect on the anterior cruciate ligament with an internal torque of five newton-meters applied to the tibia. None of the braces had any effect on strain on the anterior cruciate ligament during active range of motion of the knee from 10 to 120 degrees or during isometric contraction of the quadriceps. Wearing of a brace did not produce an increase in the value for strain on the anterior cruciate ligament. For the activities that were evaluated in this study, none of the braces produced adverse effects on the anterior cruciate ligament, and there were no significant differences in the strain on the anterior cruciate ligament between the use of a custom-fit or an off-the-shelf brace design. There were no apparent advantages of the more expensive custom-made braces compared with the off-the-shelf designs.
Adult↗
Clinical versus instrumented knee testing on autopsy specimens.
The accuracy, reliability, and reproducibility of the Genucom Knee Analysis System and Knee Signature System (KSS) for anteroposterior knee laxity evaluations were compared. The devices detected the same relative change in laxity between normal and anterior cruciate ligament-deficient specimens during Lachman and drawer testing; however, the absolute values differed. In a clinical study, two examiners performed three independent Lachman and drawer tests using the Genucom, KSS, and a subjective clinical examination on ten patients. The Genucom demonstrated interexaminer differences during the Lachman test. The clinical examination proved to be more reliable than either instrumented device for both Lachman and drawer testing. The intraexaminer variability of the Genucom and KSS was large, with the average 95% confidence limits about the mean for the Genucom and KSS equal to +/- 4.2 and +/- 2.8 mm, respectively. These findings question the accuracy, reliability, and reproducibility of the instrumented methods.
Adolescent↗
Functional outcomes of low back pain: comparison of four treatment groups in a randomized controlled trial.
The revised Oswestry Low Back Pain Questionnaire (ROLBPQ) and Roland-Morris Activity Scale (RMAS) were compared in a randomized controlled trial of chiropractic manipulation, stroking massage, corset and transcutaneous muscular stimulation (TMS). This trial employed specific inclusion and exclusion criteria, including nonspecific low back pain for a duration of 3 wk to 6 months and ages between 18 and 55. We had the opportunity to ask 85 patients to answer the questionnaires. Sixty-three patients, who completed the initial and final evaluations, were used for data analysis. Both ROLBPQ and RMAS showed good internal consistency with alpha coefficients ranging from .77 to .93. Both instruments showed a significant difference between the chiropractic manipulation and massage groups (p less than .05). RMAS was able to further show significant differences between the chiropractic manipulation and TMS groups, and between the corset and massage groups, but the ROLBPQ failed to do so. RMAS also showed that chiropractic manipulation had a better but nonsignificant result than corset, possibly due to insufficient sample size and/or duration of treatment. We conclude that both instruments are reliable for measuring low back pain disability, and chiropractic manipulation has a superior short-term benefit when compared to stroking massage and TMS in subacute low back pain patients. In addition, it appears that RMAS is preferable in a clinical trial situation for subacute low back pain because it is more sensitive than ROLBPQ to detect changes.
Adolescent↗
Vibration of the spine and low back pain.
There are now many studies suggesting a positive relationship between both low back pain and spinal degeneration and exposure to whole body vibration. Such relationships appear to be particularly marked in drivers of tractors, earth-moving equipment, and trucks. There is a tendency toward a greater incidence of complaints as exposure increases. Vibration affects the spine by exciting a 4-6-Hz resonance that is related to the biologic "soft spring" between S-1 and the seat. The muscle nerves fire sequentially under vibration and fatigue. In animals, vibration exposure leads to pronounced creep, increased disk pressure, and changes in the levels of neuropeptides in the dorsal root ganglia.
Animals↗
External fixator pin design.
The integrity of the bone-pin interface is the critical link in the stability of external fixation systems. External fixation pins placed in cancellous metaphyseal bone frequently loosen over time, resulting in fixation failure and an increased risk of infection. To design an external fixation pin with optimal bone-metal interface strength in cancellous bone, a systematic study of various thread design features was performed. Combinations of pitch, tooth profile, and minor diameter in 5 mm self-tapping half pins were evaluated in coaxial pullout testing using a fresh bovine cancellous bone. A significant increase in pullout strength was found with a decrease in minor diameter. No statistical differences were found in pullout strength attributable to thread profile and pitch. There were no significant interactions between minor diameter and tooth profile or minor diameter and pitch. The data obtained suggest significantly greater holding power in cancellous bone can be achieved by using an external fixation pin with a smaller minor diameter or a larger interference. Additional pullout testing of five commercially available external fixator pins was performed. Of these, the two pins with the largest interference demonstrated greater pullout strength. Therefore, within a range of acceptable major diameters and adequate minor diameters for the torsional strength requirements, an optimal interference for cancellous pin application may exist and it may well be larger than that present in currently available external fixation pins.
Animals↗
Biomechanics of lumbar disk disease.
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Biomechanical Phenomena↗
Diagnosing instability.
The various definitions of instability are reviewed and preference is given to the definition of instability as a loss of stiffness. This definition fits with current laboratory observations. Roentgenographic changes, particularly those associated with degeneration, have no relationship to instability. Multiple roentgenographic images can be of use, but accuracy is limited, and often valuable information at midmotion range or in other planes is missing. Stereoroentgenography appears to offer some promise, but implanted metallic markers are necessary to attain adequate accuracy. Ionizing radiation dose levels are of concern in these techniques. External fixation techniques appear to be of use in some patients. Kinematic linkages and frames containing infrared light emitting diodes are extremely promising, because they give kinematic information in detail.
Humans↗
The impact response of the seated subject.
An impact method for establishing the dynamic response of the seated subject is introduced. The method employs a pendulum to apply the impact to the suspended seat. Pins are placed in the spinous process at L3. Highly reproducible results are obtained. The results were not affected by the amplitude of impact, implying a linear system. A marked peak of transmissibility is found in the 4-5 Hz range and an attenuation peak is found close to 8 Hz. Both muscle contraction and postural changes affect the dynamic response. A relaxed posture shows greater gain and attenuation peaks. A valsalva stiffens the system and reduces the effective damping. The vertical response of the body probably shows in the 5-6 Hz peak, while the rotational response is probably encompassed in the 8 Hz attenuation peak.
Adult↗
Concepts in mathematical modeling.
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Biomechanical Phenomena↗
Intervertebral motion during vibration.
Vibration exposure is widely recognized as a risk factor for low back pain. An experimental protocol was designed to quantify the intervertebral motion response in human subjects to sinusoidal vertical vibration at 5 and 8 Hz, and at a variety of acceleration levels. Intervertebral motion in the mid-sagittal plane was measured using a transducer linkage system attached to pins placed directly into the spinous processes of adjacent vertebrae. The postures of the subjects were carefully controlled. The effects of forward flexion, arm support, gravitational load, and sitting on a cushion were evaluated. The rigid body motion of the superior vertebra with respect to the inferior vertebra was expressed in terms of relative sagittal plane rotation, axial translation, and anterior-posterior shear translation. It was found that the lumbar motion segments exhibited coupled periodic behaviour in response to sinusoidal vertical vibration, with up to 1 mm peak-to-peak displacement in the axial direction. The greatest intervertebral motion occurred when the subject was exposed to 5 Hz vibration as compared to 8 Hz. For a constant frequency of 5 Hz excitation, the peak-to-peak amplitudes of the computed motions tended to increase as the acceleration level increased. In the flexed posture, with no arm support, the active trunk musculature helped reduce the intervertebral motion. Additional gravitational load on the shoulders caused increased relative axial displacement. A polyethylene foam cushion placed on the seat reduced vibration transmission at 5 Hz excitation and consequently decreased the intervertebral motion.
Adult↗
ACL reconstruction: in vivo measurement of patellar tendon graft elongation.
The implantation of a free autogenous patellar tendon graft is the surgical technique that currently offers the best results in anterior cruciate ligament reconstruction. However, numerous aspects regarding both technique and postoperative rehabilitation can still be improved. The aim of this study was to measure the elongation of the patellar tendon in vivo in the operating room after reconstructive surgery, subjecting the knee to normal strain such as passive mobilization or anterior displacement of the tibia. Three volunteers were studied. Our results were different from those reported in a previous study conducted in vivo on a normal anterior cruciate ligament (ACL). In spite of the isometric position of the tendon, passive mobilization provoked a progressive increase in the elongation of the graft within each cycle of flexion-extension and between one cycle and the next. This also occurred during the Lachman test. These findings suggest that the graft undergoes a process of tensile adjustment when it is first put under strain. Continued elongation once this process appears stabilized raises doubts as to the reliability of isometric measuring devices.
Adult↗
Whole-body vibration exposure in subway cars and review of adverse health effects.
New York City Transit Authority subway operators have a high prevalence of back problems. To evaluate a possible dose-response relationship for whole-body vibration, we studied subway car vibrations measured and analyzed according to the International Standard Organization 2631 and Verein Deutscher Ingenieure 2057 standards. Vibration transducers in triaxial orientation were mounted in a disc pad directly on the subway operator's seat. The relatively high lateral and vertical accelerations, primarily the combined effects, may all contribute to the high rate of musculoskeletal complaints, especially of the lower back. Other factors aggravating whole-body vibrations include primitive ergonomic cab and seat design, forced body posture, high noise levels, and organizational work stress.
Back Pain↗
Dynamic lifting capacity: the relationship between peak force and weight as an indicator of effort.
Quantification of lifting capacity has become a major component in clinical and occupational evaluations of people with or at risk for low back pain. The ideal test of maximum acceptable lifting would include an index of subject effort. Heart rate response appears to have significant limitations as an indicator of effort. In this study a device that records vertical lifting force measured peak force/weight ratios (PF/W) and differences (PF-W) for individual lifts. Seventeen men without low back pain lifted the device with progressively heavier loads. The PF/W, PF-W, and heart rate responses were compared at half-maximum and maximum effort levels. The PF/Ws were higher, while the PF-Ws and heart rate responses were lower during half-maximum efforts. As an indicator of subject effort, the relationship between peak force and weight may play a key role in isoinertial lifting evaluations.
Adult↗
To drive without low-back pain.
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Automobile Driving↗
Epidemiology and prevention of skiing injuries.
Between 1972 and 1987, the authors prospectively evaluated all 5701 injuries which were reported to the injury clinic operating in the base lodge of a ski area in northern Vermont, USA. During that time approximately 1,690,000 skier visits were estimated to have occurred at the ski area. The total injury population was divided into 28 groups and sub-groups and examined by regression analysis for long term trends. Among upper body injuries, only lacerations showed a positive improvement. Among lower extremity injuries, virtually all injuries below the knee improved dramatically, some groups by more than 80%. Knee injuries, although improved as a group, showed a marked 2.7-fold increase in serious (third degree) sprains usually involving the anterior cruciate ligament. Clavicular fractures were the only upper extremity injury which increased significantly in incidence.
Athletic Injuries↗