Working with horses: an OWAS work task analysis.

Most work in horse stables is performed manually in much the same way as a century ago. It is the least mechanized sector dealing with large animals. People working with horses are exposed to several types of risk for developing musculoskeletal problems, but the work tasks and workload have not been investigated in detail. The aim of this study was to estimate the postural load of the work tasks performed around horses to find those that were harmful and required measures to be taken to reduce physical strain. Altogether, 20 subjects (stable attendants and riding instructors) were video recorded while carrying out their work in the stable, and preparing and conducting riding lessons. The work was analyzed with the Ovako Working posture Analysis System (OWAS) to determine the postural load and to categorize the potential harmfulness of the work postures. Three work tasks involved about 50% of the work positions in the three OWAS categories (AC2 to AC4) where measures for improvement are needed: "mucking out" (50%), "bedding preparation" (48%), and "sweeping" (48%). These work tasks involved over 60% work postures where the back was bent, twisted, or both bent and twisted. Therefore, it is important to find preventive measures to reduce the workload, which could include improved tools, equipment, and work technique.

Riding instructors, their musculoskeletal health and working conditions.

UNLABELLED: The aim of this study was to gain a deeper understanding of riding instructors' working conditions, work load, and frequency of musculoskeletal problems and to identify potential risk factors for the development of musculoskeletal problems. A questionnaire was mailed to 800 instructors in Sweden containing questions on their work environment, work tasks, work load, and musculoskeletal symptoms. The Borg CR-10 scale was used to estimate the work load, and the Standardized Nordic Questionnaire was used to analyze the occurrence of musculoskeletal symptoms. Perceived symptoms were most frequently reported to be in the shoulders (60%), lower back (56%), and neck (52%) during the past 12 months; 91% of the riding instructors had experienced symptoms from at least one of nine anatomical areas during the past 12 months and 55% in the seven days prior to answering the questionnaire. Removal of manure from the stable was considered to be the task involving the heaviest work, and 14.5% had suffered an injury at work during the past year. The risk of developing musculoskeletal problems was 50% less for those who did physical exercise at least two hours a week besides riding (OR = 0.47, CI 0.25-0.89). CONCLUSIONS: The prevalence of symptoms was high, considering the low median age (33 years). Reducing workload, guarding against injury, and performing other exercises besides riding could be important measures for the prevention of musculoskeletal symptoms in this particular group of workers.

Complications associated with segmentation of the maxilla: a retrospective radiographic follow up of 82 patients.

The aim of the present study was to retrospectively examine the clinical and radiographic incidence and frequency of injuries to teeth and their surrounding tissues adjacent to interdental osteotomies in conjunction with segmentation of the maxilla. Vertical interdental osteotomies have been performed in combination with Le Fort I osteotomy for correction of various dento-facial deformities. All our orthognathic patients are followed prospectively in a standardized manner. Eighty-two consecutive patients who underwent dento-facial correction by segmented maxillary osteotomy alone or in combination with simultaneous mandibular surgery between 1992 and 1998 were included in the study. They were followed for up to 30 months postoperatively. A total of 158 interdental osteotomies were performed, involving a total of 316 teeth. Only a small number of complications such as osteolytic processes, marginal bone destruction, root resorption or mechanical injuries to the teeth were seen.

Validity of the Children's Dental Fear Picture test (CDFP).

The validity of the Children's Dental Fear Picture test (CDFP) was investigated in 146 Swedish children aged 5-12 yr. The CDFP was compared with dental fear scores on Children's Fear Survey Schedule-Dental Subscale (CFSS-DS), selection criteria for testings (dentally fearful/not dentally fearful), and with level of general fear measured by the Short Form of Children's Fear Survey Schedule (CFSS-SF). Dental fear in the CDFP was closely related to high scores on CFSS-DS and CFSS-SF. The CDFP proved to be a valid instrument to diagnose dental fear in children with values of sensitivity up to 98.5%.

Dental behavior management problems in Swedish children.

4505 Swedish children aged 4-11 yr were surveyed regarding dental behavior management problems (BMP) and dental health. Dental charts were retrieved from clinics in the Public Dental Service in Göteborg, and data were then compiled regarding BMP, action against BMP, caries, fillings, use of local anesthetics, and number of missed appointments. Behavior management problems were found in 10.5% of the children, and were more common in the younger children, among children who missed appointments, and in children who received restorative treatment without local anesthetics. The BMP children had more carious and fewer filled surfaces. In 43.4% of the cases with BMP the strategy chosen was postponement of dental treatment or no measure taken.

Acoustic trauma in extracranial magnetic brain stimulation.

The effects of the magnetic coil acoustic artifact (MCAA) associated with extracranial magnetic field stimulation (EMFS) of the brain were studied in normal hearing rabbits. Spectral and intensity analyses showed that the MCAA is a high intensity transient signal with peak energy between 2 and 5 kHz, and peak amplitudes in the first 100-200 mu sec. At EMFS levels of 50-100% of maximum output (2.0 Tesla), the corresponding MCAA levels were 131-142 dB sound pressure level (peak hold) at the outer ear and amplified by the external meatus to reach 145-157 dB sound pressure level (SPL) at the position of the tympanic membrane in rabbits. Measurements of the acoustic middle ear muscle reflex (AMR) in non-anesthetized rabbits indicated that exposure to EMFS levels of 50-100% resulted in correspondingly increasing compound threshold shifts (CTS) and permanent threshold shifts (PTS) in the unprotected ears of the experimental animals. Auditory brain-stem responses (ABR) measures on the same and additional animals corroborated these findings. Morphological studies showed evidence of substantial cochlear trauma at EMFS levels as low as 50%, with increasing severity up to 100% EMFS. Morphological examination of inner ear structures following exposure to the MCAA in the acute preparation (fixed within hours after exposure) showed ruptures between pillar cells and a detached organ of Corti. Preparations examined 3 or more weeks after exposure showed damaged pillar cells, a widespread loss of outer hair cells, fused and fractured inner hair cell stereocilia, and kinocilium outgrowth on inner hair cells. Although this extremely short impulse contains approximately 2 orders of magnitude less acoustic energy than a continuous noise exposure of 131 dB for 15 min, it is substantially more injurious to the cochlea. The present findings suggest that the acoustic artifact produced by the EMFS coil in some clinical instruments may pose a potential risk for temporary and permanent hearing loss in patients and clinicians when held in close proximity to the unprotected ear. Initial studies suggest that the magnetic field alone did not appear to cause permanent hearing impairment. We recommend the use of ear protectors for the patient and clinician during EMFS as a precautionary measure to prevent possible hearing loss from the MCAA.

Hearing loss from the acoustic artifact of the coil used in extracranial magnetic stimulation.

The stimulating coil used in extracranial magnetic field stimulation (EMFS) emits a high intensity impulse sound artifact that causes permanent threshold shifts in the unprotected ears of experimental animals. At magnetic stimulation levels of 50 to 100%, the magnetic coil acoustic artifact (MCAA) ranged from 145 to 157 dB peak sound pressure level at the eardrum. The magnetic field alone did not appear to cause hearing impairment since no threshold shifts were observed in ears that were plugged with ear protectors during exposure to the MCAA. These findings suggest that the acoustic artifact produced by EMFS in the clinic may pose some risk for hearing loss in patients and clinicians when held in close proximity to the unprotected ear. We recommend the use of ear protectors for the patient and clinician during EMFS as a precautionary measure to prevent hearing loss.

Some considerations on caloric test results.

The caloric test procedure as suggested by Fitzgerald & Hallpike is still widely used. With a carefully standardized procedure it is well suited to identify the affected side in patients with unilateral vestibular impairments. By repeated testing it is also possible to follow the course of a vestibular affection.

The stapedius reflex test studied with laboratory and commercial equipment in acoustic neurinomas.

Comparisons were made of contralateral stapedius reflex recordings obtained by means of two different electroacoustic impedance devices, the commercial Grason-Stadler 1723 (G-S 1723) impedance meter and a laboratory equipment, in patients with acoustic neurinoma. With the latter, acoustically elicited reflex responses were noted in 11 of the 21 tumour ears studied. The recordings with the G-S 1723 showed deflections indicating stapedius reflex responses in all 21 cases. Three of these deflections proved to be artefacts. The stapedius reflex threshold test indicated a retrocochlear lesion in all 21 pathological ears when the laboratory equipment was used. The G-S 1723 produced recordings indicating a cochlear lesion in two of these tumour ears. Furthermore, five of 15 normal contralateral ears were classified as having a retrocochlear lesion with the G-S 1723, as opposed to one with the laboratory equipment. The reflex decay test could be applied in 15 normal and six tumour ears. Only minor discrepancies in the degree of reflex decay were found between the two instruments. As the G-S 1723 displayed a low rate of detection for acoustic neurinomas (90%) and led to a large number of false-positive interpretations (33%), it is concluded that this instrument is less useful for diagnostic purposes than the laboratory equipment in differentiating between cochlear and retrocochlear lesions.

Auditory brainstem response (ABR) to rarefaction and condensation clicks in normal and abnormal ears.

The shift in latency of wave V in ABR upon the reversal of stimulus phase was investigated in a normal-hearing reference material (65 ears) and in 20 ears of conductive hearing loss, 29 ears of steep high-frequency hearing loss and 17 ears of acoustic neurinoma or cerebellopontine angle tumor. In addition, reproducibility was studied in the reference material. The stimulus was a 2.0-kHz haversine wave at 75 or 35 dB nHL delivered at the rate of 20 Hz. 2000 responses were averaged for each stimulus phase. Electrodes were placed on the vertex and on ipsilateral mastoid. Stimulus wave form was determined in a 6-cc coupler and in a few cases with a miniature electrete microphone in the ear canal. In the reference material, a significant difference of the wave V latency between the condensation (C) and rarefaction (R) stimulus was observed. When taking the absolute difference, the mean value was 0.15 ms at 75 dB nHL. This time difference corresponds to a frequency of 3-4 kHz. In high frequency cochlear loss, the C-R difference increased in proportion to the downward shift in frequency of the high frequency slope of the audiogram. In conductive hearing loss, the C-R difference was similar to that of the reference material. In retrocochlear cases, the C-R difference was unpredictable, but was remarkably often small compared with the V latency. It was concluded that the difference in wave V latency between C and R clicks provides information about the excitation pattern in the inner ear but it is not reliable enough to give more than a rough estimate of the individual frequency of generation of ABR. The results are arguments against the use of the alternating stimulus phase as a routine procedure.

A lower audiometric limit for auditory brainstem response (ABR).

A lower audiometric frequency limit for reproducible ABR in response to 75 dB and 85 dB nHL 2.0 kHz haversine wave stimuli was defined by testing subjects with steep high-tone loss of varying cut-off frequencies. The limit between audiograms with and without reproducible ABR passed roughly through 40-50 dB HL at 500 Hz and 80-90 dB HL at 1000 Hz. Lack of ABR was not equivalent to lack of potentially useful hearing.

Brainstem response (ABR) to rarefaction and condensation clicks in normal hearing and steep high-frequency hearing loss.

ABR in response to 2.0 kHz haversine waves was obtained in normal-hearing subjects and in 27 ears with steep high frequency hearing loss. Rarefanction (R) clicks had a significantly shorter latency to wave V than condensation (C) clicks (mean = 0.13 ms SD = 0.16 ms, p less than 0.001). This value corresponds to a frequency of generation of ABR of 3-4 kHz. The latency difference between R and C clicks increased in reversed proportion to the cut-off frequency of the pure tone audiogram in the ears with steep high-frequency hearing loss. It was concluded that R-C latency difference can be used as an approximate indication of frequency of generation of ABR.

Brainstem response (ABR) in conductive hearing loss.

Results from an ongoing study were presented. The latency-intensity function for ABR was determined in subjects with unilateral pure conductive hearing loss, on the normal and the affected side. The shift of the latency-intensity function was found to correlate well (r = 0.84) to the air-bone gap at 3.0 kHz. A nomogram was constructed which allows a direct calculation of correlation factor (in ms) in pure conductive loss.