Low back pain in schoolchildren. A study of familial and psychological factors

STUDY DESIGN

The results of a survey organized in the school system of the Swiss canton of Fribourg. An original questionnaire was developed for this study are reported.

OBJECTIVES

The goal of this study was to evaluate the possible role of familial or psychological factors in schoolchildren reporting nonspecific low back pain.

SUMMARY OF BACKGROUND DATA

Previous surveys have shown a high prevalence of nonspecific low back. pain among schoolchildren, particularly teen-agers. The reported familial incidence raises, among others, the question of a possible role of psychological or behavioral factors.

METHODS

This survey was performed with a validated 43-item self-administered questionnaire eliciting information about back pain history, family characteristics, children's activities, and psychological parameters. All schoolchildren (n = 615), ages 12-17 years, in two secondary schools (Fribourg, Switzerland) were surveyed. The response rate was 98%.

RESULTS

Reported lifetime prevalence of back pain was 74%. Lumbar pain was the most frequent localization of pain (69% of back pain). The measured psychological factors were significantly associated with reported nonspecific low back pain and its consequences as well as with sibling history of low back pain.

CONCLUSIONS

The study suggests that psychological factors play a role in children's reporting of nonspecific low back pain.

Physical and psychological workload in men with and without low back pain

Current and retrospective physical and psychological workload was studied in 148 mean, 45-55 years old. The men represented three groups with respect to low back health status: Healthy low back (Group 1, n = 36), intermittent low back pain (LBP) (Group 2, n = 91) and chronic LBP (Group 3, n = 21). The methods used were a self administered questionnaire, a rating scale of perceived exertion, and blind expert assessment built on a classification of job titles. Group 1, the back-healthy subjects, had been less exposed to heavy physical work than subjects with intermittent LBP (Group 2) and chronic LBP subjects (Group 3) through their whole working-career and in their present work (p < or = 0.05, p < or = 0.01). Group 2 tended to be significantly less exposed in their present work than Group 3 (p < or = 0.06). Non-neutral working postures were reported more often in Groups 2 and 3 than in Group 1 (p < or = 0.05, p < or = 0.001). Both groups 2 and 3 perceived present and earlier work to be more strenuous than Group 1, with respect to the low back (p < or = 0.000). Subjects in the healthy low-back group had lower values in the qualitative demand index ("too difficult working tasks" and "too great responsibility") than subjects in Groups 2 and 3 (p < or = 0.01). This study indicates that more attention should be given to the individual's perception of physical workload.

Health care utilization for low back pain in Belgium. Influence of sociocultural factors and health beliefs

STUDY DESIGN

A population-based survey was undertaken.

OBJECTIVES

To describe health care utilization for low back pain (LBP) in a culturally diverse society with universal access to health care; to describe how LBP chronicity influences health care utilization; and to describe how sociocultural and demographic factors and health beliefs influence health care utilization.

METHODS

A probability sample of approximately 5,000 Belgian adults stratified by gender, age, social class, and habitat was surveyed by trained interviewers. Information on demographics, health beliefs, frequency of LBP, and health care utilization was elicited. Statistical analysis was conducted by means of univariate and multivariate logistic regression. Analysis was restricted to 2,660 respondents with history of LBP.

RESULTS

Of subjects with LBP, 38% reported daily LBP. Sixty-three percent had seen a health professional for the most recent episode; 11% had been on bed rest. Forty-four percent had at sometime undergone radiography; three and a half percent had ever undergone spinal surgery. Eighty-six percent considered themselves in good health. Controlling for LBP frequency, all forms of health care utilization examined were associated with health beliefs.

CONCLUSIONS

LBP frequency, health beliefs, and sociocultural factors influence health care behaviors and utilization among adults with a history of LBP in a society with universal access to health care. The association of history of spinal surgery with reports of daily LBP suggests that spinal surgery has failed, at least partly, to relieve LBP.

Endotoxaemia and inflammatory mediators in febrile patients with haematological disease

OBJECTIVES

To study the pattern of plasma levels of endotoxin, tumour necrosis factor alpha (TNF-alpha), interleukin 6 (IL-6) and C-reactive protein (CRP) in febrile neutropenic patients and to assess the potential diagnostic value of these analyses.

DESIGN

Consecutive prospective study.

SETTING

Patients treated at the haematology ward at Danderyd Hospital, Sweden.

SUBJECTS

Ninety-four patients with fever and haematological disease entered the study (male/female: 59/35) with 176 febrile episodes.

INTERVENTIONS

Blood samples were drawn at days 0, 1, 2 and 6 after onset of fever for analysis of, endotoxin, TNF-alpha, IL-6 and CRP.

RESULTS

Infectious aetiology was established in 62.5% of the febrile episodes. Blood cultures showed significant growth in 71/176 (40.3%) febrile episodes. Nonbacteraemic bacterial infections were diagnosed in 34/176 (19.3%) episodes. Endotoxin was detected in plasma in 40% of febrile episodes regardless of aetiology. TNF-alpha was detected in 61% and IL-6 in 94% of all febrile episodes. The initial TNF-alpha and IL-6 levels were significantly higher in patients with Gram-negative bacteraemia than in patients with other causes of fever (P < 0.001). In episodes evaluated as successful after empirical antibiotic treatment, a significant (P < 0.001) decrease in CRP concentrations were found on day 6 after onset of fever.

CONCLUSIONS

The sustained, low-grade endotoxaemia and persistently elevated levels of TNF-alpha and IL-6 found in febrile patients may reflect a failing mucosal barrier that allows endogenous bacterial products to reach the circulation. The diagnostic value of endotoxin, TNF-alpha, IL-6 and CRP to discriminate between bacteraemic and nonbacteraemic febrile episodes was very limited. The study supports the present policy of broad, empirical antibiotic treatment in patients with haematological disease and fever.

After-effects on stiffness and stretch reflexes of human finger flexor muscles attributed to muscle thixotropy

1. While the subject maintained a weak contraction in his finger flexor muscles, holding the metacarpophalangeal joints in 45 deg flexion, test torque pulses were applied which caused rapid finger extension movements and electromyographic (EMG) stretch reflex responses. Before each test pulse the fingers were passively flexed or extended ('post-short' and 'post-long' trials) for about 10 s. The EMG and joint deflection responses in the two types of trial were compared after averaging. 2. In the 'post-long' trials, the EMG reflex response showed a comparative increase in latency, with a reduction of the short-latency (M1) component and an enhancement of the medium-latency (M2) component. 3. The angular deflections were larger, and the turning points of the deflections, which indicated the start of the mechanical reflex responses, occurred later in the 'post-long' trials. These differences were not seen when the torque pulse was immediately preceded by a strong, brief isometric finger flexor contraction in the test position. 4. Immediately following the return to the test position the background finger flexor EMG activity was larger in the 'post-long' trials, a difference which gradually subsided over 15-20 s. A strong, brief contraction in the test position also eliminated this inter-trial difference. 5. The results are interpreted as manifestations of thixotropic after-effects in intra- and extrafusal muscle fibres. It is proposed that the M1 component of the stretch reflex is largely a response to the 'initial burst' of impulses in primary spindle afferents.(ABSTRACT TRUNCATED AT 250 WORDS)

Non-specific low-back pain among schoolchildren: a field survey with analysis of some associated factors

A study population composed of 1,755 children 8-16 years of age were surveyed using a 15-item, self-administered questionnaire. The response rate was 97.7%. The purpose of the survey was to evaluate the possible association between low-back pain and certain social factors and predicaments. Descriptive statistics and logistic regression analysis showed that parental history of treated low-back pain (adjusted odds ratio 2.10; p < 0.001), competitive sports activity (adjusted odds ratio 1.73; p = 0.003), and time spent watching television (adjusted odds ratio 1.23; p = 0.05) significantly increased the risk for low-back pain among children, controlling for the child's age and gender.

Intrafascicular recordings of afferent multi-unit activity from the human supraorbital nerve

Intrafascicular recordings of afferent multi-unit activity were obtained from the supraorbital nerve in 40 healthy human volunteers, using tungsten micro-electrodes inserted percutaneously at the eyebrow. Seventy-seven fascicular receptive fields were mapped; their area ranged from 2 to 76 cm2, with a median of 19 cm2. The smallest fields were found in the eyebrow region, and the largest on the scalp. In response to non-painful electrical intradermal stimulation, the conduction velocity of the fastest nerve fibres was calculated to be 40 +/- 2 m s-1 (mean +/- SEM), and the later part of the afferent volley corresponded to a velocity of 20 +/- 1 m s-1. The responses to skin indentation indicated that the density of mechanoreceptive innervation was higher in the lower part of the forehead than in the upper/posterior part of the innervation territory of the nerve. A rapid mechanical tap on the forehead and scalp evoked two major afferent volleys corresponding to the on- and off-phase of the stimulus. Manipulation of hairs resulted not only in dynamic responses to hair movement, but also in a static discharge during sustained hair displacement. When a fascicular field included the eyebrow region, skin stretching during blinking movements evoked distinct afferent activity. Following mechanical and electrical stimuli there were no signs of 'trigeminal antidromic potentials' of the type described in the cat and monkey.

The hand in neck manoeuvre as a tool to analyze pain-generating mechanisms in the subacromial impingement syndrome

A scoring system for a standardized composite movement of the shoulder--the Hand in Neck (HIN) manoeuvre--is presented. The EMG activity of the supraspinatus muscle was studied in 5 healthy subjects at different performance levels of this test. It is shown that the supraspinatus muscle is about four times more active during normal performance than at the subnormal levels, which among themselves do not differ. EMG activity was also studied during normal performance of another standardized manoeuvre--the Pour out of a Pot (POP) test. Based on a comparison of the EMG data with clinical data from patients with the subacromial impingement syndrome it is suggested that an abnormal HIN test indicates the presence of a traction responsive pain generator in the supraspinatus tendon. In the same patient group, the combination of a normal HIN test and an abnormal POP test indicates pain generated by compression of subacromial structures.

Sociocultural factors and back pain. A population-based study in Belgian adults

A population-based survey of approximately 4000 adults in Belgium, a bi-cultural country with a uniform health care system, explored the relationships of socio-cultural and employment factors to the reported experience of low back pain (LBP). Predictors of 1) history of LBP, 2) first LBP, and 3) daily LBP were examined by multiple logistic regression analysis. Thirty-three percent of the population had current LBP, including 5% experiencing their first episode; 26% had past but not current LBP, and 41% had never had LBP. Increasing age (OR > 2.0, P = .000) and female gender (OR 2.16, P = .000) were associated with history of LBP; only gender (OR 1.40, P = .02) was associated with first episode; neither was associated with daily LBP. Language was associated with history (OR 1.80, P = .000) and first occurrence (OR 1.77, P = .000) but not daily LBP. Among those employed, work dissatisfaction was associated with history of LBP (OR > 2.4, P = .02) and daily LBP (OR 3.85, P = .02), but not with first episode. The results suggest that sociocultural factors influence the expression of LBP, but not the risk of chronicity once LBP is reported, and that work satisfaction may not be causally related to LBP, but may intervene along with type of occupation in the possibility of continuing employment once LBP is present. Prospective studies are needed to confirm these results and elucidate causal relationships.

Isometric maximal and submaximal trunk extension at different flexed positions in standing. Triaxial torque output and EMG

Thirty-one healthy men were tested for the effects of trunk-flexion positions (0 degrees, 15 degrees, and 35 degrees) in standing on triaxial torques and electromyogram of 10 trunk muscles during voluntary maximal and submaximal isometric trunk extension. At a more flexed position, both erector spinae and latissimus dorsi showed significantly higher RMS-EMG. The abdominal obliques were coactivated only during 100% maximum voluntary exertion at each posture. In all tests, the rectus abdomini were quiet. Mean maximum extension torque increased significantly at 15 degrees and 35 degrees of trunk flexion. The ratio of extension torque over RMS-EMG of the trunk extensor muscles, called the neuromuscular efficiency ratio (NMER), also increased in the more flexed posture. However, NMER has to be interpreted with caution because it is affected both by posture and exertion levels. The effects of posture on the torque generation capability of the trunk question the validity of the current lifting recommendations.

Cross-sectional study of the isokinetic muscle trunk strength among school children

Our surveys have shown lifetime prevalence of L.BP. over 30% among schoolchildren. The purpose of this study was to evaluate the relationship between back and isokinetic trunk strength, anthropometric parameters, and sports activities. One hundred and seventeen healthy children aged 10-16 years were included. All these volunteers had semi-structured interview, anthropometric and dynamic strength measurements. Lifetime prevalence of back pain was 44.5% and point prevalence was 13%. In this cross-sectional study, anthropometric and strength profiles were significantly related to age and gender. Non specific low back pain was not correlated to trunk muscle strength and/or sports activities.

Body composition, endurance, strength, cross-sectional area, and density of MM erector spinae in men with and without low back pain

Thirty-six 45-55-year-old men with healthy low backs were studied with respect to body composition, isokinetic and isometric trunk strength, trunk muscle endurance, and cross-sectional area and radiological density of mm erector spinae. Results were compared to those of men in the same age group with intermittent low back pain (LBP) (n = 91) and with chronic LBP (n = 21). The back healthy group was significantly stronger and had longer trunk muscle endurance times than men with chronic LBP. Men with intermittent LBP had strength and endurance values in between the back healthy and chronic groups. There were no significant differences between any of the groups with respect to body composition and cross-sectional area of mm erector spinae. Radiological density for mm erector spinae was significantly decreased in the chronic LBP group compared to the back healthy and intermittent LBP groups. The deconditioning syndrome and its relationship to intermittent and chronic LBP is discussed.

Quantification of trunk muscle performance in standing, semistanding and sitting postures in healthy men

The purpose of this study was to determine trunk muscle performance in the sitting, semistanding, and standing postures during isometric and dynamic extension and flexion movements. Twenty-five male subject volunteers, with no previous history of back pain participated in the study. A triaxial dynamometer that measures torque, angular position, and velocity was used to measure isometric and dynamic motor output. The dynamometer allows testing in the sitting and standing postures. A custom-designed module also allowed testing in the semistanding posture. Each subject was tested in two sessions. The first session included the physical examination and three trials of isometric maximum voluntary contractions in the three postures. The second session included the dynamic performance against a resistance equal to 50% of the effort, as measured in the first session. Subjects were instructed to perform five repetitive flexion and extension cycles as fast and accurately as possible with maximum effort. An analysis of variance with repeated measures design was used to investigate the effects of the postures (standing, semistanding and sitting), the direction of exertion (flexion and extension), and the interaction effects of the isometric and dynamic parameters (maximum and average torque, velocity, power, and range of motion). The effects of direction (F = 98, P < 0.0001) and the interaction of posture and direction (F = 7.9, P < 0.001) were significant. The maximum isometric flexion strength was significantly higher in the standing posture than in semistanding and sitting. The maximum isometric extension was not affected by the posture (sitting, semistanding and standing).(ABSTRACT TRUNCATED AT 250 WORDS)

Back schools in prevention of chronicity

This chapter has reviewed the role of back school and educational programmes for the common and non-specific acute and subacute low back pain patient. The following seems to come out of this review. Education is an important part of patient care. However, several questions arise about the content of the education, the selection of patients, the patient compliance to instruction given, how the information is retained, and which outcome measures should be used. It is also important to realize that the back school is a modality or a tool that may be used as an adjunct, but as a sole treatment it seems to have less impact than in combination with other structured or goal-oriented programmes. When a back school is instituted in a hospital or in industry, it requires administrative and budgetary support and a multidisciplinary staff to successfully carry out the programme. The information given must be adapted to the needs of the participants and all members of the team must give the same information to the patient. A poorly structured back school where patients are dumped because the physician or other health care provider has nothing else to offer is a poor solution for the patient, a poor solution for the health care provider, and can only increase the patient's discomfort and health care costs.

Back pain in children and teenagers

Controversial opinions have been published concerning the frequency of LBP among children and adolescents. Studies from orthopaedics or neurosurgical departments have reported low figures for prevalence of specific LBP due to serious disorders. Field surveys, on the contrary, have shown that cumulative life prevalence of non-specific LBP in children and teenagers can be comparable to the prevalence data for adult populations. Some specific diagnoses are more common or characteristic of children complaining of LBP. Age, gender, sports activities and family history of LBP have been found to be significantly associated with an increased prevalence in non-specific LBP among children. Low back pain among children and teenagers is common and should be recognized. This chapter provides guidelines for a clinical approach and differential diagnoses. Most back pain in these age groups is benign and should be treated as such.

The DNA-binding protein P52 of human cytomegalovirus reacts with monoclonal antibody CCH2 and associates with the nuclear membrane at late times after infection

Monoclonal antibody CCH2 is commonly used for the detection of human cytomegalovirus (HCMV) infected cells in tissue sections as well as in cultured cells. The specificity of CCH2 was determined by screening a recombinant lambda-gt11 cDNA gene bank from HCMV-infected fibroblasts. By sequencing a reactive clone, the antigen was identified to be the non-structural DNA binding protein p52 of HCMV (UL44 reading frame). The viral insert from the lambda clone was recloned in bacterial expression vectors. For this, a new vector, pRos-RS, was constructed. The resulting clones were tested in immunoblot analyses. They were reactive with CCH2 as well as with reconvalescent sera positive for antibodies against HCMV, by this proving the specificity of CCH2. Using this monoclonal antibody in confocal microscopy, the subcellular localization of p52 in infected cells was analyzed. In these analyses, p52 was found to be nuclear and to be associated with the nuclear membrane at late times after infection.

Role of physical therapy in the treatment of cervical disk disease

Table 4 summarizes how physical therapy should be implemented during the acute and chronic phase of cervical disk disease. From the outset of treatment, the patient should be encouraged to return to work or other productive activities and should be taught how to be responsible for their own recovery. If passive modalities are used, they must be an adjunct to the active modalities. As soon as the patient is able to continue with an active program without unbearable pain, the passive modalities should be discontinued gradually. If neck pain becomes chronic, the accompanying psychosocial dysfunction must be addressed through behavioral modification techniques, preferably in a multidisciplinary setting. Modification of the work place, work habits, and lifestyles must be emphasized at both the acute and chronic stages. The modalities presented in this article are commonly used by physical therapists. Unfortunately, the clinical efficacy of most of these modalities has yet to be proved. A literature search on the effectiveness of various physical therapy modalities by Sievers et al showed that only 4% of the studies published from 1979 to 1985 were controlled clinical trials. This scientific output of physical therapists needs to be corrected.

Effects of spinal flexion and extension exercises on low-back pain and spinal mobility in chronic mechanical low-back pain patients

It has been estimated that one fourth to one half of all patients treated in physical therapy clinics suffer from low-back pain. The purpose of this study was to compare the effects of spinal flexion (Group I) and extension (Group II) exercises on low-back pain severity and thoracolumbar spinal mobility in chronic mechanical low-back pain patients. Both groups had significantly less low-back pain after treatment (P less than .10). There was no significant difference, however, between the spinal flexion and extension exercises in reduction of low-back pain severity. The results indicated a significant difference between the groups in increasing the sagittal mobility (P less than .10). The results did not indicate any significant difference between and within groups in increasing the coronal and transverse mobility of the thoracolumbar spine. Either the spinal flexion or extension exercises could be used to reduce chronic mechanical low-back pain severity, but the flexion exercises had an advantage in increasing the sagittal mobility within a short period of time.

Low-threshold mechanoreceptive and nociceptive units with unmyelinated (C) fibres in the human supraorbital nerve

1. In recordings from the human supraorbital nerve with tungsten microelectrodes, eleven afferent units with unmyelinated (C) axons were identified on the basis of their conduction velocities (0.6-1.4 m/s). 2. Eight units had low mechanical thresholds (less than or equal to 0.23 g) and could be activated up to their maximal firing rates of about 100 impulses/s by weak tactile stimuli, whereas three units had higher thresholds (5.5 g) and responded vigorously to noxious stimuli only. 3. During a skin indentation the low-threshold units adapted to an irregular low-frequency discharge, and release of the stimulus elicited a prominent off-response often ending with an after-discharge. Slow stroking was a particularly effective stimulus, even when done with cotton wool, whereas rapid stroking reduced the response. All types of stroking stimuli were occasionally followed by after-discharges. Repeated mechanical stimulation at short intervals resulted in a decline of the response, indicating receptor fatigue. For two units a response to skin cooling was observed. 4. The above low-threshold C units have all the main characteristics of the C mechanoreceptors known from the cat and primates but not previously proven to exist in man. The high-threshold C units are similar to the polymodal nociceptors found in other human skin areas.

The relationship of torque, velocity, and power with constant resistive load during sagittal trunk movement

Strength and fitness studies have been used to determine the predictability of back pain episodes. Tests have demonstrated that isometric strength displays little prognostic value in the development of low-back pain. Static isometric tests have achieved widespread usage due to the simplicity and safety of protocols, the readily available technology, and the low administrative costs. Dynamic lifting models have, however, predicted significantly higher spinal loads than those derived from static models. The objectives of this study were twofold: to investigate the relationship of the torque, velocity, and power to the resistive load during trunk flexion and extension, and to develop predictive models for these relationships for the subject's performance of the 10th, 50th, and 90th percentile distribution. The results of the study found that the flexion/extension torque had a positive linear correlation with the set resistance; the velocity displayed a negative linear correlation, while power had a quadratic relationship with the resistance.

Sympathetic discharges in the human supraorbital nerve and their relation to sudo- and vasomotor responses

1. Sympathetic nerve activity occurring as bursts of multi-unit impulses was recorded with tungsten microelectrodes in the supraorbital nerve of awake healthy subjects. Within the fascicular innervation zone on the forehead, skin resistance was measured as an indicator of sweat gland activity, and skin blood flow was measured with laser-doppler flowmetry. 2. At room temperature, there was little or no background burst activity, but arousal stimuli or mental stress evoked bursts followed by a vasodilator response. Provided repeated arousal stimuli were delivered, individual bursts were followed by a decrease in skin resistance. 3. Body heating induced increasing background burst activity. After an initial period without associated electrodermal activity, there were decreases in skin resistance, which showed a positive linear correlation with the amplitude of the preceding burst. Individual bursts were followed by a vasodilator response with an average onset latency of 2.8 s and an average duration of 9.1 s, and rapid increases in blood flow coincided with a marked increase in burst activity. Arousal stimuli evoked bursts followed by both vasodilator and skin resistance responses. 4. During body cooling, there was no background burst activity, but signs of relatively weak, probably neurally mediated vasoconstriction were observed and arousal-evoked bursts were reduced or abolished, as were the associated vasodilator and skin resistance responses. 5. It is concluded that body heating induces active sympathetic vasodilatation in the skin of the human forehead, and that this is either sudomotor-mediated or caused by vasodilator fibres firing in synchrony with sudomotor fibres. A similar sympathetic mechanism probably underlies the vasodilator responses evoked by arousal stimuli and mental stress.

Environmentally induced disorders of the musculoskeletal system

The human suffering and economic cost attributable to musculoskeletal disorders cannot be overemphasized. Biomechanical principles have been introduced to explain the microtrauma and macrotrauma as mechanisms of injury. Stress-induced remodeling is a useful paradigm in the study of environmentally induced disorders. The concept of environment should include psychosocial and organizational factors with respect to musculoskeletal complaints and chronic pain. Low back pain, osteoarthritis, osteoporosis and its associated fractures, and cumulative trauma disorders are the most critical and common musculoskeletal disorders. The risk factors for low back pain have been identified, and preventive measures for reducing the chronicity of low back pain have been discussed. Preventive approaches to control or limit the fractures associated with osteoporosis and loss of bone mass are preferred to simple management of the fracture of osteoporotic patients. It can be concluded that too little or too much stress can disturb the homeostatic or the equilibrium state of health and that much remains to be researched to quantify the optimal stress levels.

A database of isoinertial trunk strength tests against three resistance levels in sagittal, frontal, and transverse planes in normal male subjects

Spatial joint complexes, such as the spine, require multiaxial systems to adequately assess their functional capacity. The B200 Isostation (Isotechnologies, Inc., Carrboro, North Carolina) is a triaxial system that has three hydraulic pumps under control of an IBM-XT. The transducers measure the torque, angular position, and velocity for all axes simultaneously. There is no isoinertial data base available for strength at different resistances in the sagittal, coronal, and transverse planes. A normal data base for dynamic performance against resistances equal to 30%, 50%, and 70% of the maximum isometric strength of trunk muscles in all three planes was established.

Histochemistry and morphology of erector spinae muscle in lumbar disc herniation

The purpose of this study was to detect any changes in the erector spinae muscles in patients undergoing surgery for lumbar disc herniation (LDH) and to analyze which factors (sex, age, the level and site of disc protrusion, and duration of symptoms) would be related to these changes. The percentage of mean area of the type I fibers was significantly larger in males and in the older age group (P less than 0.05), due to the decreasing size of type IIa and IIb fibers. Patients with LDH have: 1) angulated and selective atrophy of type II fibers with a higher type IIb/IIa ratio; 2) with increasing age and duration of symptoms, more marked atrophy of type II fibers; and 3) other unspecific pathologic changes.

Intrafascicular multi-unit recordings from the human infra-orbital nerve

Intrafascicular micro-electrode recordings were made from the human infra-orbital nerve close to the infra-orbital foramen. The fascicular organization was studied and multi-unit activity from low-threshold mechanoreceptive afferents was recorded during tactile stimuli, vibration and facial movements. Attempts were also made to record C-fibre activity. Innervation zones corresponding to 66 fascicles were mapped with tactile stimuli on facial hairy skin and the red zone of the lip. Most of these fields were located on the upper lip, where they overlapped, indicating a high innervation density. The fields had a median size of 3.8 cm2. Skin indentation evoked dynamic on- and off-responses and a much less pronounced static discharge. The afferent double-peaked responses to an oscillating probe applied to the peri-oral region induced similar grouping of the EMG activity during sustained lip protrusion. Contraction of facial muscles and stretching of the skin evoked on- and off-responses, whereas the static discharge was less pronounced, especially during sustained stretching. The dynamic sensitivity to minor variations in contraction and stretching was high, and during normal facial movements, as in speech, there was a barrage of impulses originating from mechanoreceptors within large facial areas. Functional implications of these sensorimotor interactions are discussed. Sympathetic C-fibre activity, frequently seen in recordings from the supra-orbital nerve, was never encountered in the infra-orbital nerve recordings, indicating a lack of such fibres. Failure to detect afferent C-fibre activity could be explained by methodological difficulties.

Mechanoreceptive units in the human infra-orbital nerve

Eighty-four low-threshold mechanoreceptive afferents innervating facial hairy skin or the red zone of the lip were recorded with micro-electrodes from the human infra-orbital nerve. Based on their responses to skin indentations, the units were classified as slowly or fast-adapting, with small or large receptive fields. The responses to hair movement, skin stretching and contraction of facial muscles were also studied. Both hairy skin and the red zone were innervated by slowly and by fast-adapting units. The innervation density was found to be highest at the corner of the mouth and on the upper lip. Slowly adapting units with small fields in hairy skin were most common and included units responding to sustained hair displacement. These units are suggested to have two types of end-organs, either pilo-Ruffini endings or Merkel cell-neurite complexes. The slowly adapting units with large fields were spontaneously active stretch receptors and may have corresponded to Ruffini corpuscles, although the possibility of other, intramuscular, receptors could not be ruled out. Only one afferent possibly innervated a Pacinian corpuscle. Most mechanoreceptors were also activated by skin stretching or contraction of facial muscles. Many of the slowly adapting units with small fields responded to the onset and release of stretch, whereas their discharge in response to sustained stretching adapted more or less completely. Spontaneously active units had the most sustained stretch response. It is concluded that several types of cutaneous mechanoreceptors can operate as sensitive proprioceptors of importance for facial kinaesthesia and motor control.

1988 Volvo award in biomechanics. The triaxial coupling of torque generation of trunk muscles during isometric exertions and the effect of fatiguing isoinertial movements on the motor output and movement patterns

Previous studies have shown that reduction of precise motor control accompanies local muscular fatigue. The effects of isodynamic fatiguing of flexion and extension trunk movements on the movement patterns and the motor output of the trunk were investigated. Twenty male subjects with no history of low-back pain for the past 6 months volunteered for the study. A triaxial dynamometer was used that simultaneously provided measurement of torque, angular position and velocity of each axis. Resistances were set independently for each axis by an interfaced computer. The subjects performed trunk flexion and extension movement against a sagittal plane resistance equal to 70% of their maximum isometric extension strength in the upright position. The minimum resistances in the coronal and transverse planes were set up at 7 Newton meters. The subjects were asked to perform trunk movement as quickly and as accurately as possible while exerting the maximum efforts until exhaustion. Analysis of variance, the MANOVA procedure with a repeated measure design, was performed among the selected parameters of the first, middle and last three repetition cycles. The selected parameters are the trunk motor output and movement patterns; the total angular excursion, range of motion, maximum and average torque and angular velocity of the trunk. All the selected parameters were significantly reduced in the sagittal plane. Subjects displayed significantly less motor control and greater range of motion in the coronal and transverse planes in performing the primary task of flexion and extension. The reduction in the functional capacity of the primary muscles performing the required task is compensated by secondary muscle groups and the spinal structure is loaded in a more injury prone pattern, as identified by finite element models. In addition it is suggested that the fatigued muscles would be less able to compensate any perturbation in the load or position of the trunk. The repetitive loading results in a weakening of the viscoelastic passive elements of the spineless structure. The loss of ability to protect these weakened passive elements makes the spine susceptible to industrial and recreational injuries.

Population studies of Huntington's disease in Wales

Long-term surveillance of Huntington's disease families living in South Wales has been undertaken since 1973. We report the updated data on prevalence and births in 101 kindreds. The trend in the births at risk of Huntington's disease has been compared with a control population in North Wales.

Motor-unit responses in human wrist flexor and extensor muscles to transcranial cortical stimuli

1. Transcranial cortical stimuli (TCCS) were used to elicit motor responses in contralateral wrist flexor and extensor muscles of healthy adult subjects. The motor responses were assessed by surface EMG recordings, by needle recordings of single motor-unit discharges, and by measurements of wrist twitch force. Our main aim was to analyze the single-unit events underlying those changes in latency, amplitude, and duration of the compound EMG responses, which could be induced by voluntary preactivation of target muscles and by changes in stimulation strength. 2. Different stimulus strengths were tested with and without background contractions in the flexor or extensor muscles. For each test (consisting of a series of 20 stimuli) the compound EMG responses were averaged and displayed together with the averaged wrist force signals. Responses of individual flexor and extensor motor units were displayed in raster diagrams and peristimulus time histograms. For units exhibiting a background firing, the mean background interdischarge interval was calculated and compared with the subsequent poststimulus intervals. 3. In relaxed muscles, a shortening of onset latency of evoked compound EMG responses was observed when raising stimulation strength. A similar latency reduction was not seen in any of the single-unit recordings. This would be consistent with the size principle of motoneuron recruitment. 4. A shortening of onset latency of evoked EMG potentials was observed also as a result of a voluntary preactivation. Such latency shifts, which were seen also in single-unit recordings, might be attributed to variations in the time required for D and I wave temporal summation at the anterior horn cell. 5. When raising stimulation strength or when adding voluntary background contraction, the evoked compound EMG potential grew not only in amplitude but also in duration, as later peaks of activity were added to the initial ones. Under optimal conditions (strong stimulus + background contraction), the period of excitation (termed E1) had an onset latency of approximately 15 ms and a duration of approximately 35 ms and was similar for wrist flexor and extensor muscles. 6. We never saw the same flexor or extensor unit fire more than once during the E1 period. For units preactivated by a background contraction, the stimulus-triggered impulse exhibited latency shifts, which, to a large extent, depended on the timing of the stimulus in relation to a preceding background discharge and which could be influenced by a change in stimulation strength.(ABSTRACT TRUNCATED AT 400 WORDS)

Prediction of outcome after cardiac arrest

Neurologic outcome of hypoxic ischemic coma after cardiac arrest was studied in 32 patients. Observations were made and samples collected 24 and 48 h after the ischemic insult. The Glasgow-Pittsburgh coma score was assessed for its prognostic value. Other variables studied were the EEG and adenylate kinase, lactate and glutathione in the cerebrospinal fluid (CSF). Outcome was termed good if the patients resumed an independent life within a 6-month follow-up period. The closest correlations between prediction and good outcome occurred with the Glasgow-Pittsburgh coma score (94%) and the EEG (77%) at the 48-h examination, a modified coma score (96%) at 48 h, and CSF lactate (78%) at 24 h. Some simple neurologic signs (e.g., no withdrawal response to pain) at stated points in time was 100% associated with a bad outcome, although their absence was not associated necessarily with a good prognosis.

Evaluation of the workplace. An introduction

To reduce and optimize the work load imposed on the musculoskeletal system in a given situation, three main areas of interest are work technique, workplace design, and the produced work itself. Ergonomically sound work techniques should be taught early and should be repeatedly evaluated and encouraged. Workplace and tool design must be adapted and modified according to the task performed at the workplace. The work produced has to be evaluated in terms of handling comfort and discomfort by the employee: the greater the comfort, the greater the productivity will be. Especially in the rehabilitation of patients with back injuries, these factors must always be considered to avoid recurrent episodes of pain and disability.

The effect of endogenous opioids on blood pressure during stress

1. A series of experiments were conducted to investigate the effect of endogenous opioids on blood pressure of laboratory rats during stress. 2. Rats subjected to 120 min immobilization showed a significant drop in systolic pressure which could be prevented by pretreatment injections of naloxone. 3. Adrenalectomized rats subjected to the same kind of stress showed a drop in systolic pressure equivalent to only 30% of the systolic pressure drop in the intact animals. This decrease in systolic pressure could also be prevented by pretreatment injections of naloxone. 4. It was concluded that the decrease in systolic pressure in intact rats during immobilization was mostly due to endogenous opioids released from the adrenal glands, whereas opioids of other origins such as the pituitary gland, were also important.

Normal trunk muscle strength and endurance in women and the effect of exercises and electrical stimulation. Part 1: Normal endurance and trunk muscle strength in 101 women

The lack of trunk muscle strength and endurance has frequently been cited as a suspected factor in the etiology of low-back pain. Several investigators have suggested that asymptomatic patients have stronger trunk muscles than patients with low-back pain. People who are physically fit appear to have a decreased incidence of low-back pain. Increased trunk muscle endurance also have been observed to decrease the incidence of low-back pain. The objective evaluation of the strength and endurance of trunk musculature may, therefore, be significant. Part 1 of this study was designed to develop a reproducible strength-endurance screening procedure and to establish normal isometric-isokinetic trunk muscle strength and endurance parameters for women. This study showed that isometric trunk flexion varied from 19-109 Nm and trunk extension from 38-168 Nm. Peak values for isokinetic trunk flexion at two speeds (30 degrees per second and 60 degrees per second) varied from 17-191 Nm and isokinetic trunk extension from 14-208 Nm. The average endurance time for trunk extensors tested with the Sorensen test was 196 seconds.

Normal trunk muscle strength and endurance in women and the effect of exercises and electrical stimulation. Part 2: Comparative analysis of electrical stimulation and exercises to increase trunk muscle strength and endurance

Several studies have shown positive correlations between muscle strength, flexibility, and the frequency of low-back pain. Weak trunk musculature and decreased endurance have thereby come to be identified as significant risk factors in the development of occupational back problems. Because it is widely accepted that exercise plays an important role in the conservative treatment and prevention of low-back pain, the goals of most rehabilitative programs involves improving the strength and endurance of the low-back pain patient. Whereas electrical stimulation has been shown to increase the muscle strength of the lower extremities, this effect has not been demonstrated for the trunk muscles. Part 2 is a prospective controlled study designed to document and to compare objectively the effects of electrical stimulation and exercise on trunk muscle strength. A total of 117 healthy women were divided randomly into four groups. Two groups received electrical stimulation with different electrical parameters, one group received exercises, and one group acted as a control group. The results showed that low-frequency electrical stimulation and exercises significantly (P less than .05) increased isokinetic back-muscle strength compared to the control and medium-high-frequency electrical stimulation groups. Both types of electrical stimulation, however, significantly increased (P less than .05) the endurance in the back muscles compared with the control and the exercise groups. This study showed that electrical stimulation may be a valuable treatment in the early care of low-back pain patients in maintaining and increasing strength and endurance of back muscles when a more active exercise program is too painful to perform.

Peripheral neural correlates of cutaneous anaesthesia induced by skin cooling in man

The effect of local skin cooling on the behavior of low- and high-threshold mechanoreceptive afferents innervating glabrous and non-glabrous skin was studied in microneurographic recordings on awake human subjects. Cooling with ice or ethyl chloride to a skin surface temperature below 10 degrees C caused a reduction of receptor sensitivity in 49 out of 52 studied low-threshold afferents. This effect was reversible upon warning but some reduction often persisted for a few minutes after normal skin temperature had been reached. The subjects' sensations of application and removal of von Frey hair stimuli were more resistant than had reappeared before the sensation of sustained pressure. This could be explained by shorter recovery times for fast than for slowly adapting units and by a relative preservation of the dynamic responses of the slowly adapting units. During the recovery phase some low-threshold mechanoreceptive afferents exhibited a transient 'spontaneous' discharge in the absence of external mechanical stimulation. The suppression of afferent C-fibre responses to needle strokes was more pronounced and long-lasting than the effect on A-fibre responses and largely paralleled the recovery of sensation of pain. It is concluded that the local anaesthetic effect of skin cooling is to a large extent explicable in terms of receptor desensitization although other mechanisms may contribute.

Microelectrode recordings from the facial nerve in man

Microneurographic recordings have for the first time been obtained from the human facial nerve trunk, close to its exit from the stylomastoid foramen. The aim was to search for evidence of an afferent or sympathetic component of the facial nerve at this level and to study the fascicular organization of motor fibres. Single unit discharges of motor axons were occasionally discerned, and all recordings showed multiunit motor impulses preceding the EMG activity of the appropriate facial muscles by about 5 ms during both blink reflexes and voluntary contractions. No evidence of low-threshold mechanoreceptive afferents was found. Electron microscopic studies at the level of recording showed unmyelinated axons but attempts to record nociceptive and sympathetic activity failed. However, deep facial pain evoked by intraneural stimulation suggested the presence of nociceptive afferents of non-cutaneous origin. Intrafascicular recording and stimulation showed that most fascicles were composed of motor axons innervating muscles within the whole ipsilateral half of the face.

Gamma loop contributing to maximal voluntary contractions in man

A local anaesthetic drug was injected around the peroneal nerve in healthy subjects in order to investigate whether the resulting loss in foot dorsiflexion power in part depended on a gamma-fibre block preventing 'internal' activation of spindle end-organs and thereby depriving the alpha-motoneurones of an excitatory spindle inflow during contraction. The motor outcome of maximal dorsiflexion efforts was assessed by measuring firing rates of individual motor units in the anterior tibial (t.a.) muscle, mean voltage e.m.g. from the pretibial muscles, dorsiflexion force and range of voluntary foot dorsiflexion movements. The tests were performed with and without peripheral conditioning stimuli, such as agonist or antagonist muscle vibration or imposed stretch of the contracting muscles. As compared to control values of t.a. motor unit firing rates in maximal isometric voluntary contractions, the firing rates were lower and more irregular during maximal dorsiflexion efforts performed during subtotal peroneal nerve blocks. During the development of paresis a gradual reduction of motor unit firing rates was observed before the units ceased responding to the voluntary commands. This change in motor unit behaviour was accompanied by a reduction of the mean voltage e.m.g. activity in the pretibial muscles. At a given stage of anaesthesia the e.m.g. responses to maximal voluntary efforts were more affected than the responses evoked by electric nerve stimuli delivered proximal to the block, indicating that impaired impulse transmission in alpha motor fibres was not the sole cause of the paresis. The inability to generate high and regular motor unit firing rates during peroneal nerve blocks was accentuated by vibration applied over the antagonistic calf muscles. By contrast, in eight out of ten experiments agonist stretch or vibration caused an enhancement of motor unit firing during the maximal force tasks. The reverse effects of agonist and antagonist vibration on the ability to activate the paretic muscles were evidenced also by alterations induced in mean voltage e.m.g. activity, dorsiflexion force and range of dorsiflexion movements. The autogenetic excitatory and the reciprocal inhibitory effects of muscle vibration rose in strength as the vibration frequency was raised from 90 to 165 Hz. Reflex effects on maximal voluntary contraction strength similar to those observed during partial nerve blocks were not seen under normal conditions when the nerve supply was intact.(ABSTRACT TRUNCATED AT 400 WORDS)

Thixotropic behaviour of human finger flexor muscles with accompanying changes in spindle and reflex responses to stretch

Prompted by previous reports on muscle thixotropy, we have investigated changes in inherent and reflex stiffness of the finger flexor muscles of human subjects at rest, following transient conditioning manoeuvres involving contractions and/or length changes of the finger flexors. The stiffness measurements were combined with electromyographic recordings from forearm and hand muscles and with microneurographic recordings of afferent stretch responses in finger flexor nerve fascicles. Finger flexor stiffness was evaluated by measuring (a) the flexion angle of the metacarpo-phalangeal joints at which the system during rest balanced the force of gravity and (b) the speed and amplitude of angular finger extensions induced by recurrent extension torque pulses of constant strength delivered by a torque motor. In the latter case, extension drifts in the resting position of the fingers were prevented by a weak flexion bias torque holding the fingers in a pre-determined, semiflexed position against a stop-bar. Stiffness changes following passive large amplitude finger flexions and extensions were studied in subjects with nerve blocks or nerve lesions preventing neurally mediated contractions in the forearm and hand muscles. Inherent stiffness was enhanced following transient finger flexions and reduced following transient finger extensions. The after-effects gradually declined during observation periods of several minutes. Similar results were obtained in subjects with intact innervation who succeeded during the pre- and post-conditioning periods in keeping the arm and hand muscles relaxed (i.e. showed no electromyographic activity). In these subjects it was also found that the after-effects were similar for active and passive finger movements and that isometric voluntary finger flexor contractions loosened the system in a way similar to finger extensions. In some subjects electromyographic reflex discharges appeared in the finger flexors in response to the extension test pulses. When elicited by small ramp stretch stimuli of constant amplitude, the stretch reflex responses were found to vary in strength in parallel with the changes in inherent stiffness following the various conditioning manoeuvres. The strength of the multi-unit afferent stretch discharges in the muscle nerve, used as index of muscle spindle stretch sensitivity, varied in parallel with the changes in inherent stiffness. Post-manoeuvre changes in muscle spindle stretch sensitivity were seen also when the spindles were de-efferented by a nerve block proximal to the recording site. The results can be explained in terms of thixotropic behaviour of extra- and intrafusal muscle fibres.(ABSTRACT TRUNCATED AT 400 WORDS)

Surgical or conservative treatment of the acutely torn anterior cruciate ligament. A randomized study with short-term follow-up observations

In a prospective study, 90 consecutive patients with total midstructural tears of the anterior cruciate ligament (ACL) were assigned at random to surgical (Group I) or conservative (Group II) treatment. Within 18.2 months of operation, 95% of the patients in Group I and 11% of those in Group II had a stable knee. The mean knee function score in Group I was 89 points, and 75% achieved more than 84 points (good or excellent). In Group II the mean score was 85; only 53% achieved more than 84 points (p less than .05). Group II patients showed greater mean quadriceps strength than those in Group I. The ability to perform a one-leg jump and to run a figure eight was similar in both groups. Early primary suture of the acutely torn ACL usually resulted in a stable knee, whereas conservatively treated patients showed knee instability. At the 18-month interval, however, the patients' functional performance seemed to be comparable in the two groups.

Measurements of trunk movements during work

To study spinal movements during work, an instrument that measured angles and angle changes in relation to a vertical plane was adapted to continuously measure forward flexion of the trunk. The instrument, which is battery-powered and worn on the back, registers the amount of flexion and its distribution over time during a work cycle by recording the time spent in each of five 18 degrees intervals between 0 degrees and 90 degrees. Also the number of times that the angle of flexion changed from one interval to another is recorded. A total of 43 subjects from three occupations--dentistry, nurses' aide work, and warehouse work--were each tested during a 60 minute work cycle. On the average, the dentists spent most of the time (52.2 minutes) in a semi-flexed position not exceeding 36 degrees and performed eight deep forward flexions (greater than 73 degrees). The nurses' aides spent one-half of the work cycle (34.4 minutes) in an upright position (0-18 degrees) and performed 70 deep forward flexions. The warehouse workers spent less than one-half of the work cycle in an upright position (27.5 minutes) and performed 153 deep forward flexions that nearly always were associated with lifting.

The influence of a preventive educational programme on trunk flexion in janitors

The influence of a preventive educational back care programme on the movement patterns of the spine during work was assessed objectively and subjectively in six janitors. Trunk flexion was measured in the subjects using a flexion analyser before they attended a preventive educational back care programme and twice afterwards. The results show that the subjects increased the amount of time spent in an upright position by about a third after the educational programme and maintained this change two and a half to three months later. They also decreased the time spent in moderate and deep forward flexion (37-72 degrees ) by about half and also maintained this decrease at three months. These changes are consistent with a decrease of the mechanical load on the spine. The study emphasises that it is possible to alter movement patterns of the spine, and thereby decrease the load during janitorial work, by a suitably designed educational programme.

The effect of a patella brace on performance in a knee extension strength test in patients with patellar pain

The object of this study was to analyze the quadriceps muscle peak strength with the Cybex-II isokinetic dynamometer in patients with patellofemoral arthralgia with and without a patella brace. Twenty-four patients, 18 women and 6 men, were studied. All had patellofemoral arthralgia. The diagnosis was made on typical clinical findings, but was supplemented with arthroscopy in seven patients with pain also over the medial joint line. After a 2 week adaptation period with the brace, a Cybex-II test was done with and without the brace. The other leg was tested as control. Twenty-one patients (88%) improved their performance in the strength test with the brace (mean difference 13.7 +/- 9.1%). With the brace, 14 patients (58%) performed at 95% of their control leg or more compared to 6 (25%) without the brace. Patients under the age of 30 years had a better effect than patients over that age.

Analysis and quantitative myoelectric measurements of loads on the lumbar spine when holding weights in standing postures

Ten subjects executed a number of weight-holding and force-resisting work tasks while standing either upright or with their trunks in 30 degrees of forward flexion. All tasks involved sagitally symmetric body configurations and were performed isometrically. A simple calculation scheme was devised to predict the lumbar trunk muscle contraction forces and the lumbar spine compression forces required for execution of each task. The myoelectric activity was recorded quantitatively at eight sites over the lumbar trunk muscles and at four sites over the abdominal muscles. Good correlation was found between the predicted muscle contraction forces and the myoelectric activities.