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Biomedical subjects

C J Snijders

Publications and source records attributed to C J Snijders.

At least 19 recordsLinked to original sources
PubMed1995

The posterior layer of the thoracolumbar fascia. Its function in load transfer from spine to legs.

STUDY DESIGN: The superficial and deep lamina of the posterior layer of the thoracolumbar fascia have been studied anatomically and biomechanically. In embalmed human specimens, the posterior layer has been loaded by simulating the action of various muscles. The effect has been studied using raster photography. OBJECTIVES: To study the role of the posterior layer of the thoracolumbar fascia in load transfer between spine, pelvis, legs, and arms. SUMMARY OF BACKGROUND DATA: It has been determined whether muscles such as the gluteus maximus, latissimus dorsi, erector muscle, and biceps femoris are functionally coupled via the thoracolumbar fascia. The caudal relations of the posterior layer of the thoracolumbar fascia have not been previously studied. METHODS: Dissection was directed to the bilaminar posterior layer of the thoracolumbar fascia of 10 human specimens. The superficial and deep lamina were studied using visual inspection and raster photography. Tension to the posterior layer of the fascia was simulated by traction to various muscles and measured by studying the displacement in the posterior layer. RESULTS: Traction to a variety of muscles caused displacement of the posterior layer. This implies that in vivo, the superficial lamina will be tensed by contraction of various muscles, such as the latissimus dorsi, gluteus maximus and erector muscle, and the deep lamina by contraction of the biceps femoris. Caudal to the level of L4 (in some specimens, L2-L3), tension in the posterior layer was transmitted to the contralateral side. CONCLUSIONS: Anatomic structures normally described as hip, pelvic, and leg muscles interact with so-called arm and spinal muscles via the thoracolumbar fascia. This allows for effective load transfer between spine, pelvis, legs, and arms--an integrated system. Specific electromyographic studies should reveal whether the gluteus maximus muscle and contralateral latissimus dorsi muscle are functionally coupled, especially during rotation of the trunk. In that case, the combined action of these muscles assists in rotating the trunk, while simultaneously stabilizing the lower lumbar spine and sacroiliac joints.

Aged↗
PubMed1995

Design criteria for the reduction of shear forces in beds and seats.

Both with respect to the aspect of pressure sores and of comfort, the inclination of backrest and seat are, amongst other factors, important design criteria. In this study the combination of seat and backrest inclination which reduces shear forces on the seat in passive seating forms the centre of attention. A biomechanical model was developed to predict these combinations and a new measurement apparatus was used for verification of the model on 10 healthy subjects (age 24.4 S.D. 2.1 yr, height 1.77 S.D. 0.08 m, mass 66.3 S.D. 11 Kg). For chairs it was found that when little shear is accepted, a fixed inclination between seat and backrest can be chosen between 90 degrees and 95 degrees. For beds a parabolic relationship was found between seat and backrest inclination with a maximum seat inclination of 20 degrees at a backrest inclination of 50 degrees. When lying with the knees bent to a position with equal inclination of thighs and shanks, the model predicts a shear force on the seat that shoves the person into the bed for every combination of seat and backrest inclination.

Adult↗
PubMed1995

Stress radiography of the talocrural and subtalar joints.

The object of this investigation was to determine a possible subtalar component in a group of 33 patients with chronic ankle instability. A group of 10 subjects without ankle/foot symptoms acted as controls. A standardized radiographic assessment of talar and simultaneous subtalar tilt was made. A hinge device to stress the joints and a specific subtalar stress view (Brodén view) were used under fluoroscopic control. Radiographs were made with the feet: (1) in neutral position, (2) after inversion with moderate force until the point of fair restraint (step 1), and (3) after inverting with more force as far as the conditions would allow (step 2). An increase of talar tilt between step 1 and step 2 was only found in feet that were symptomatic. This suggests that this increase is only possible when lateral ligaments are damaged. Further research is necessary to determine whether this finding can serve as a parameter to discriminate between physiological and abnormal talar tilt. A wide range of subtalar motion was found in both symptomatic and asymptomatic feet. With the present method, practically all subtalar joints showed some loss of congruity and medial shift of the calcaneus in relation to the talus. This could not be correlated with ankle instability at the talocrural joint. The consequence of the use of different subtalar stress methods has so far received little attention and is discussed.

Adolescent↗
PubMed1995

Potential for recurrence of hallux valgus after a modified Hohmann osteotomy: a biomechanical analysis.

On the basis of a biomechanical model the present study investigates whether a foot-widening effect, which may result in recurrence of bunions, can be demonstrated in operated patients. Therefore, the medial deviation of the first metatarsal head as a result of flexion forces on the hallux was measured in eight patients with clinical idiopathic hallux valgus, who underwent a modified Hohmann osteotomy, and in eight "normal" persons. We found that (1) before osteotomy, all forefeet broadened while pressing the big toe downward, and (2) after surgery, widening of the forefeet on average had significantly diminished, but still existed, which might explain the development of recurrences. (3) After surgery, the patients showed a slight, but statistically nonsignificant, decrease (from 37 N to 25 N) of the isometrically determined average maximal applicable flexion force. These abnormal hallux loads may cause, or result from, a deviation in gait pattern.

Adult↗
PubMed1995

Prevention of fracture at the distal locking site of the gamma nail. A biomechanical study.

To investigate the origin of fractures at the distal locking site of the Gamma nail, we loaded ten paired human cadaver femora fixed with a Gamma nail in torsion until they fractured. When an awl was hammered in to start the hole for distal locking a fissure appeared in the lateral cortex of all the femora, and the mean torsional load to create a fracture was reduced by 57.8% compared with that in a control group in which the distal locking hole had been started with a centre drill. When an additional drill hole was made, the mean failure load in torsion decreased by 35.7%. We strongly recommend that an awl should not be used at the distal locking site of the Gamma nail; we recommend the use of a centre drill. Additional drill holes should be avoided because they act as stress raisers.

Femoral Fractures↗
PubMed1994

[2 patients with autosomal recessive generalized myotonia].

Two men aged 20 and 18 years complained of transient muscle stiffness of 4 and 2 years' duration, respectively. Symptoms had started in the legs. Gradually, arm muscles and eventually facial and pharyngeal muscles became affected. Neurological examination revealed myotonia without any associated symptoms. Myotonia was confirmed by electromyography. Laboratory investigations, ECG, chest X-rays, slit lamp examination in both patients, and muscle biopsy in one, revealed no abnormalities. History, physical examination and electromyography of family members disclosed no evidence of myotonic dystrophy. Based on the findings mentioned, the diagnosis of autosomal recessive generalised myotonia was made.

Adolescent↗
PubMed1994

A comparison of working postures of parcel sorters using three different working methods.

The postures of the trunk of eight parcel sorters were measured continuously under three different working conditions, during whole shifts. The working methods used were two different sorting tables and a hydraulic lifting platform on which the carts were to be placed. The question posed by the PTT-Post occupational health service was whether the latter method proved to be the better one with respect to the load on the musculoskeletal system. This study will help them to make a well-considered decision on which working method to choose for the new distribution centre in Rotterdam. The method used for measuring the working postures and movements of the trunk is the Portable Posture Registration Set (PPRS). This method was developed at the department of Biomedical Physics and Technology of the Erasmus University Rotterdam. While using the lifting platform, the subjects stood 8-11% more erect compared to the work at the sorting tables, thereby reducing the load on the lumbar spine. For this reason the lifting platform is preferred, although sagittal flexion of the back was somewhat more. It is stressed that the way in which sorters use the lifting platform is very important.

Adult↗
PubMed1994

Forces acting on the maxillary incisor teeth during laryngoscopy using the Macintosh laryngoscope.

We determined the forces on the maxillary incisors during routine laryngoscopy in 65 adult patients. The forces were measured by a strain gauge based sensor positioned between the handle and the blade of the laryngoscope. The mean maximal force acting on the maxillary incisors was 49 N. In patients without maxillary incisors, the force acting on the gums was significantly lower at 21 N (p < 0.001). These results suggest that, despite traditional advice to the contrary, a levering movement of the laryngoscope, using the maxillary incisors (or gums) as a fulcrum, is common practice. Biomechanical analysis revealed that, although levering is not the preferred movement, it is an efficient way of bringing the glottis into view. These results may have implications for future laryngoscope design.

Adult↗
PubMed1994

Influence of shear on skin oxygen tension.

Since the early studies on decubitus many authors expect significant influence of shear on decubitus risk. In the study described here skin oxygen tension at the sacrum was measured with combined pressure and shear stress on a young healthy population (mean age 25.5 years, SD 3.4 years). Cut-off pressure is defined as the level of external pressure exerted on the skin at which the skin oxygen tension is 1.3 kPa. At this level ischaemia of the skin can be expected (Bar, 1988). A mean cut-off pressure of 11.6 kPa was found when no shear stress was applied vs. a significantly lower mean cut-off pressure of 8.7 kPa with a shear stress of 3.1 kPa. No significant relationship was found between cut-off pressure and systolic blood pressure, diastolic blood pressure, skin thickness at the sacrum, percentage of fat and skin oxygen tension in the unloaded situation.

Adipose Tissue↗
PubMed1994

Lowered motor conduction velocity of the peroneal nerve after inversion trauma.

To analyze the effect of inversion trauma on peroneal nerve function, motor conduction velocity was measured in 22 patients. In the injured leg, 4-8 d post trauma motor nerve conduction velocity in the knee-caput fibulae segment of the superficial peroneal nerve was significantly smaller when compared with the contralateral leg and the control group. Five weeks post trauma these values were normal again. For three segments of the deep peroneal nerve, the motor conduction velocity was significantly reduced, 4-8 d post trauma, when compared with the control group. In the caput-ankle and knee-ankle segment, motor conduction velocity was still significantly lowered 5 wk post trauma. Lowered amplitudes of the Compound Motor Action Potentials of the extensor digitorum brevis muscle were found 4-8 d post trauma. No correlation was found between motor nerve conduction velocities and subjective clinical tests (anterior drawer sign and (manually performed) talar tilt test). The results of this study support the hypothesis that inversion trauma is frequently accompanied by lesions of the peroneal nerve. Motor conduction velocity measurements can be a valuable tool in assessing more objectively functional instability of the ankle joint induced by inversion trauma.

Adolescent↗
PubMed1992

Biomechanics of the finger with anatomical restrictions--the significance for the exercising hand of the musician.

Exercise and teaching of musicians presupposes in the individual the constitutive ability to freely execute the finger movements required in the playing of the instrument. However, in the hand anatomical restrictions may exist that limit the mobility of the fingers and, thereby, the possibility to determine their movements voluntarily. In this article we investigate the kinematics of a monodigital system in which restrictions are present.

Biomechanical Phenomena↗
PubMed1992

An integrated therapy for peripartum pelvic instability: a study of the biomechanical effects of pelvic belts.

OBJECTIVES: The objectives of this study were to investigate the influence of pelvic belts on the stability of the pelvis and to discuss the treatment of peripartum pelvic instability. STUDY DESIGN: In six human pelvis-spine preparations, sagittal rotation in the sacroiliac joints was induced by bidirectional forces directed at the acetabula. Weight-bearing was mimicked by the application of a compressive force to the spine. The biomechanical effect of a pelvic belt was measured in 12 sacroiliac joints. RESULTS: The pelvic belt caused a significant decrease in the sagittal rotation in the sacroiliac joints. The effect of a 100 N belt did not differ significantly from that of a 50 N belt. CONCLUSION: The combination of a pelvic belt and muscle training enhances pelvic stability. The load of the belt can be relatively small; location is more important. The risk of symphysiodesis, especially as a result of the insertion of bone grafts, is emphasized.

Aged↗
PubMed1991

A biomechanical model for the analysis of the cervical spine in static postures.

To gain a better understanding of the forces working on the cervical spine, a spatial biomechanical computer model was developed. The first part of our research was concerned with the development of a kinematic model to establish the axes of rotation and the mutual position of the head and vertebrae with regard to flexion, extension, lateroflexion and torsion. The next step was the introduction of lines of action of muscle forces and an external load, created by gravity and accelerations in different directions, working on the centre of gravity of the head and possibly a helmet. Although the results of our calculations should be interpreted cautiously in the present stage of our research, some conclusions can be drawn with respect to different head positions. During flexion muscle forces and joint reaction forces increase, except the force between the odontoid and the ligamentum transversum atlantis. This force shows a minimum during moderate flexion. The joint reaction forces on the levels C0-C1, C1-C2, and C7-T1 reach minimum values during extension, each in different stages of extension. Axial rotation less than 35 degrees does not need great muscle forces, axial rotation further than 35 degrees causes muscle forces and joint reaction forces to increase fast. While performing, lateral flexion muscle forces and joint reaction forces must increase rapidly to balance the head. We obtained some indications that the order of magnitude of the calculated forces is correct.

Biomechanical Phenomena↗
PubMed1991

The effect on sitting posture of a desk with a 10 degree inclination for reading and writing.

A pilot study was carried out on 10 subjects to examine the effect that a desk with a 10 degree inclination had on their sitting posture while reading and writing. A continuous recording of the subjects head and trunk positions was made. Each subject was studied during two periods of 1.5 h on different days. The subject worked at a flat desk on the first day and at a desk with a 10 degree inclination on the second. On average, the position of the head in the sagittal plane was found to be 6 degrees more erect and the position of the trunk 7 degrees more erect when working at a desk with a 10 degree inclination than when working at a flat desk. The maximal decrease in load observed on the cervical spine was 35% and on the thoracic spine 95%. The angle between the head and the trunk did not change significantly when using an inclined desk. Differences in posture in the frontal plane were not observed in this study.

Adult↗
PubMed1991

Posture control and the risk of industrial accident: a stabilographic investigation in a naval shipyard.

In a previous case-control study on the effect of impaired perceptual acuity on the risk of industrial injuries at a naval shipyard, three factors which might influence the perception and processing of sensory impressions--alcohol consumption, hearing loss exceeding 20 decibels (dB) and exposure to noise exceeding 82 dB(A)--were found to contribute to the risk of injury. According to recent reports, these factors can all lead to impaired posture control. Because in general about 40% of all accidents are associated with falling, tripping, slipping and the like, a supplementary study has been carried out to unravel possible confounding effects of posture control on these three risk factors. Cases (who had suffered two or more accidents during the preceding 4 years) and controls (who had been accident-free in the same period) were compared as regards posture control measured during silence or noise. No significant difference in posture control was found between cases and controls, either in silence or during exposure to heavy noise.

Accidents, Occupational↗
PubMed1991

Standardization of grip strength measurements. Effects on repeatability and peak force.

The aim of our study was to test grip strength and assess the effects of various degrees of standardization on repeatability and level of peak force. Sixteen healthy persons and eight subjects with an impaired hand function have been tested using a strain-gauge dynamometer. We compared four measurement protocols: (A) the subject is free to assume a comfortable arm position; (B) the subject is also free to assume a comfortable arm position but in addition a challenging stimulus to exceed a previous maximal effort, is given; (C) the arm was held in a predescribed and partly fixated position, as recommended by the American Society of Hand Therapists; (D) the position of the dynamometer is standardized using two reference points both on the hand and on the dynamometer. We found high test-retest reliabilities for each measurement protocol without any significant difference. There were, however, significant differences in strength level. With measurements according to protocol B the highest peak values were noted. Since the measurement protocol B combined good reliability with realistic peak forces, this procedure seems most suitable for grip strength measurements.

Adolescent↗