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Clinical and electrodiagnostic abnormalities of the median nerve in army dental assistants before and after training as preventive dental specialists.

INTRODUCTION

Median mononeuropathy at or distal to the wrist or carpal tunnel syndrome is one of a number of muscle-, tendon-, and nerve-related disorders that affect people performing intensive work with their hands. During the past 20 years there has been a tremendous increase in the reported cases of CTS, (1-3) resulting in an increased focus on occupational surveillance and screening. (2) Dental hygienists reportedly have a high prevalence of upper-extremity musculoskeletal disorders, including CTS. (4-13)

OVERVIEW

Dental personnel, including dentists, dental hygienists, and dental assistants, have been reported as having a high prevalence of upper-extremity musculoskeletal disorders, including carpal tunnel syndrome (CTS). A research study was developed and implemented to determine the presence of median and ulnar neuropathies in a population of experienced dental assistants as they trained to become preventive dental specialists. Subjects completed a history form, were interviewed, underwent a physical examination, and had nerve conduction studies performed on both upper extremities during the pretraining and posttraining data collection sessions. The pretraining data collected on experienced dental assistants has been presented (14) and served as a baseline measure in this study to determine the effects of preventive dental specialist's training. Although the prevalence of clinical and electrodiagnostic abnormalities of the median nerve in this sample closely mirrors the prevalence reported for other dental professionals, the 12-week training program did not appear to further impact the electrophysiologic status of the median or ulnar nerves. Further long-term prospective research involving the impact of dental practice and techniques for reducing upper extremity injuries in dental professionals appears to be warranted.

REVIEW OF THE LITERATURE

Lalumandier and McPhee11 surveyed US Army dental personnel and stated that 75% of dental hygienists reported having hand problems, and 56% exhibited probable or classic symptoms of CTS. In a study determining the presence of hand problems in Army dental personnel, 45% of the dental personnel surveyed indicated hand problems, and 25% were determined to indicate a high probability of CTS. (12) The authors concluded that Army dental personnel are at greater risk of developing CTS than the general public. (12) In a separate investigation, Rice et al (13) reported symptoms associated with CTS were noted by 75.6% of the dental workers, 11% reported diagnosed CTS, and 53% reported back and shoulder pain. Individuals in the dental hygienists and dental assistant-expanded function group were found to be at the greatest risk for developing upper extremity symptoms, CTS, and back pain. Other investigators have reported the prevalence of CTS among dental hygienists was 3%, (9) 6%, (15) 7%,8 and 8%. (4)

Several ergonomic risk factors associated with CTS include repetitiveness of work, forceful exertions, mechanical stress, posture, temperature, and vibration. (16) These risk factors may be present for dentists and dental hygienists as dental instruments may cause contact stress over the carpal tunnel, and wrists may be held in awkward positions for prolonged periods. (17) In a study of dental hygienists, Bramson et al (17) evaluated several risk factors using hand-surface goniometry and electromyography, and concluded that dental hygienists' exposure to high-risk postures was minimal, and that the force they exerted during work was of medium risk.

Median mononeuropathy at or distal to the wrist and other musculoskeletal dysfunction of the upper extremities is a well-documented problem among dentists and dental hygienists. Unfortunately, there is a lack of information in the literature to document the presence of CTS or upper extremity musculoskeletal dysfunction in Army dental assistants (MOS * 68E) as they train to become Army preventive dental specialists (MOS 68E-X2). The job description for the preventive dental specialist is similar to that of a civilian dental hygienist, however, the training and educational requirements for the 2 positions are different. Therefore, the purpose of this study was to determine the presence of clinical and electrodiagnostic abnormalities of the median and ulnar nerves in both upper extremities in this sample of Army dental assistants during their training to become Army preventive dental specialists.

METHODS AND MATERIALS

All dental assistants (n=47) participating in the September 2007 and January 2008 preventive dental specialist classes were approached to participate in this study. Three potential subjects declined to participate, 2 volunteered but were dropped from the course prior to data collection, and 7 volunteered but were not included in the study as they had no prior clinical experience as an Army dental assistant. The 7 dental assistants without dental assistance experience had proceeded directly from completion of the dental assistant course and matriculated into the preventive dental specialist course. All participated in the study during the first and last weeks of their 12-week Preventive Dental Specialist Course. A prerequisite for admission in the Army Preventive Dental Specialist Course is completion of the Army Dental Assistant Course.

Experimental procedures, risks, and subject rights were discussed with all subjects before participation in the study. All subjects signed an institutionally-approved, written consent form. Pregnant individuals were excluded. The study was approved by the Institutional Review Board of the Brooke Army Medical Center, Fort Sam Houston, Texas.

A history, physical examination, and upper quarter neuromusculoskeletal screen were performed to determine the status of the neural integrity of the median and ulnar nerves. These assessments were performed in both the pretraining and posttraining phases of the data collection.

History

A history was taken from each patient in questionnaire format. The history included information pertaining to demographics, medical history, military background, dental assistant experience, hand dominance, and the amount of time using a computer.

Physical Examination

A physical (screening) examination was part of the evaluation process of each subject. The physical examination included assessment of active range of motion, manual muscle tests, sensory evaluation, reflex testing, and select special tests. (18,19) Specifically, active range of motion was assessed for the cervical spine, shoulders, elbows, and wrists and hands. Manual muscle testing was performed for all major muscle groups in both upper extremities. Sensory assessment was determined with both light touch and pain/pin prick assessment of both peripheral nerves and dermatomes in both upper extremities. Muscle stretch reflexes (also known as deep tendon reflexes) were obtained from the biceps brachii, brachioradialis, and triceps in the upper extremities, and the quadriceps (patellar tendon), and triceps surae (Achilles tendon), in the lower extremities. Both upper and lower extremity pathological reflexes were assessed with the Hoffman sign (upper extremity) and Babinski sign (lower extremity). Last, the special tests of Tinel's sign of median and ulnar nerves at the wrist, Tinel's sign of the ulnar nerve at the elbow, Phalen's test, and the assessment of the radial pulses during positional changes of the upper extremities and neck (Adson's maneuver) were examined. (18,19)

Nerve Conduction Studies

At the time of volunteer solicitation, potential subjects were instructed to abstain from exercising for one hour prior to testing. Skin temperature at the wrist was measured using a digital thermometer model TM99A (Cooper Instrument Corporation, Middlefield, CT), and was maintained at or above 32[degrees]C. If skin temperature fell below this value, the wrist, hand, and forearm were rewarmed with warm towels.

The Cadwell Sierra LT electromyograph and stimulator (Cadwell Laboratories, Inc, Kennewick, WA) were used to measure the compound motor action potential (CMAP) and sensory nerve action potential (SNAP) latencies and amplitudes. The stimulating current was a monophasic pulse 0.1 millisecond long. The oscilloscope was set to a sweep duration of 2.0 milliseconds per division and a gain of 20 [micro]V per division for the SNAPs. For the CMAPs, the oscilloscope was set to a sweep duration of 2.0 milliseconds per division and a gain of 5 mV per division. The filter settings were 10 Hz to 10 kHz for the motor potentials and 10Hzto2 kHz for the sensory potentials. The sensory latency was measured at the negative peak of the SNAP, and the amplitude was measured from negative peak to positive peak. The motor latency was measured from the negative takeoff of the evoked CMAP, while the amplitude was measured from the baseline to the negative peak of the evoked response. The obtained results were recorded manually and on computer printout.

Specific details for performing the median and ulnar nerve conduction studies (NCS) were presented in a study by Harkins et al (20) and follow procedures previously described. (14,21-24) The median and ulnar nerve palmar and digital distal sensory latencies (DSLs), distal motor latencies (DMLs), F-wave latencies, and conduction velocities were obtained from both upper extremities. All NCS procedures included measurement of the anatomic course of the nerve: median and ulnar palmar DSLs (8 cm), median and ulnar digital DSLs (14 cm), and median and ulnar DMLs (8 cm). In addition to comparing median nerve palmar and digital DSLs, DMLs, F-wave latencies, and conduction velocities with a chart of normal values, comparison studies between median and ulnar palmar DSLs, digit DSLs (digit 2 and digit 5, digit 4 median/ ulnar), and DMLs in the same and opposite extremities were obtained. Examination of median and ulnar latencies in the same extremity and median and ulnar latencies in opposite extremities has been shown to assist in early electrodiagnosis of CTS. (14,21-24)

Data Management and Analysis

Descriptive statistics for subject demographics and nerve conduction study variables and chi square ([chi square]) analysis for NCS comparison studies were calculated using Statistical Package for Social Sciences software, version 12.0 (SPSS Inc, Chicago, IL).

Results

Pretraining Assessment

History

Thirty-five subjects participated in this study (24 female, 11 male). The age of the subjects ranged from 18 to 41 years, and the mean [+ or -] SD was 23.3 [+ or -] 5.6 years. (14) Thirty of the subjects were right-handed. The mean number of months the dental assistants had been working in a dental clinic prior to preventive dental specialist training was 13.9 months, with a range of 2 to 84 months. All subjects had been in the military for at least 4 months, had completed basic combat training, and had completed dental assistant training. When asked about warm-up exercises prior to practicing as a dental assistant, 33 subjects responded to performing no warm-up exercises, and 2 subjects responded affirmatively. Thirteen of the subjects reported that they did not take breaks when working as a dental assistant, and 22 subjects did report taking breaks from work at 30 minutes (6 subjects), 45 minutes (2 subjects), 60 minutes (5 subjects), and less frequently than every hour (9 subjects). (14)

In assessing the time the subjects spent working on a computer, the mean time was 5.9 hours per week with a range of one to 25 hours per week. Six of the subjects played video games with a mean of 1.8 hours per week. Only five of the subjects reported playing musical instruments with a mean of 0.4 hours per week (range 1-5 hours/week).

When asked to describe their general health, thirty of the subjects reported being in excellent/good health and five of the subjects failed to respond to this question. None of the subjects reported having a history of neuropathic disease, renal disease, peripheral vascular disease, thyroid disease, diabetes, or arthritis. (14) When asked if they had experienced an injury, sixteen of the subjects responded affirmatively. Twelve of the subjects responded positively to having a problem with their head, neck, or upper extremities during the previous 6 months prior to data collection. All other subjects denied having any musculoskeletal problems in the past 6 months.

When asked specifically about current pain or symptoms in the neck or upper extremity, the following information was gathered: neck or scapular pain (n=8), left arm/forearm pain (subject 24), right wrist/hand pain and/or numbness/tingling (N/T) (subjects 5, 8, 12, and 13), and left wrist/hand pain and/or N/T (subjects 12 and 14). (14)

In review of the subjects' history, the following subjects had subjective complaints suggestive of median or ulnar dysfunction: subject 5 had right wrist pain, subject 12 had N/T and pain in the right digit 3 4-5 and left digit 4, and subject 14 had N/T in the palm of the left hand. (14) Otherwise, from the information obtained in the history, there were no indicators suggesting median or ulnar nerve abnormalities in the upper extremities of these dental assistants.

Screening Examination

All subjects had normal active mobility of the cervical spine, shoulder, elbow, wrist and hand. Quadrant tests were determined to be normal without radicular symptoms in either upper extremity.

Motor Strength -Subject 19 had 4/5 strength right flexor pollicis longus and flexor digitorum profundus digit 2 (anterior interosseous nerve); subject 24 had 4/5 strength left elbow extensors, left wrist extensors, left wrist flexors, and left abductor pollicis brevis; subject 30 had 4/5 strength left/right shoulder abduction and 4/5 strength left abductor digiti minimi (ADM); and subject 39 had 4/5 strength left/right ADM. (14) Otherwise, all subjects were assessed to have normal (5/5) muscle strength for the neck flexors, extensors, and rotators (C1-5); and both upper extremities to include the scapula elevators, depressors, protractors, and retractors (C1-5); shoulder flexors, abductors, and external/internal rotators (C5-6); elbow flexors and extensors (C5-8); wrist flexors and extensors (C6-8); finger flexors and extensors (C7-T1); and hand intrinsics (C8-T1). All upper extremity peripheral nerves (motor components) and myotomes (C4-T1) were assessed during motor testing.

Sensation--Subject 10 had decreased pinprick in the palmar surface of left digit 5. (14) Otherwise, all subjects had normal peripheral nerves (sensory components) and C4-T1 dermatome sensory testing results for light touch and pain/pin prick in both upper extremities.

Muscle Stretch Reflexes and Pathological Signs-All subjects displayed present and equal muscle stretch reflexes and pathological signs (Hoffman and Babinski) were absent in all subjects in both the upper and lower extremities.

Special Tests-Ten subjects had positive findings for the special (provocative) tests (Tinel's or Phalen's) of the median or ulnar nerves (Table 1). All other subjects were noted to have negative findings with the performance of special tests.

Thoracic Outlet Tests-Subject 9 had decreased radial pulses bilaterally in the scalene, costoclavicular, and clavipectoral fascia/humeral positions. Otherwise, all subjects displayed normal radial pulses when the upper extremities were tested in the 3 thoracic outlet syndrome testing positions. (14,18,19)

Other than subjects 24, 30, and 39 (motor strength), subject 10 (sensory testing), and the 10 subjects that had positive findings on the special tests portion of the physical examination, there were no diagnostic indicators or evidence of median and ulnar nerve abnormalities in either upper extremity of the dental assistants tested during the physical examination portion of the assessment. (14)

Nerve Conduction Studies

The results of the nerve conduction studies are presented in Table 2. The values for these electrophysiological variables for each subject were compared to a chart of normal values. This chart of normal values was developed in the Clinical Electrophysiological Laboratory, Texas Physical Therapy Specialists, and revalidated at the Electrophysiological Laboratory, US Army-Baylor University Doctoral Program in Physical Therapy. The chart of normal values depicted in Table 2 is similar to other charts of normal values. (14,21-24)

When comparing the results of the study with the chart of normal values, all subjects had normal NCS values including conduction latencies, amplitudes, and conduction velocities of the median and ulnar nerves in both upper extremities. Interestingly, when comparison studies between the median and ulnar palmar DSLs, digital DSLs, and DMLs in the same and opposite extremities, and the digit 4 median/ulnar comparison study in the same extremity were assessed, there were electrodiagnostic abnormalities of the median nerve at or distal to the wrist in 9 subjects (26%) involving 14 hands (20%) (Table 3). (14) In the present study, the normal comparison values for palmar (14,21-26) and digital DSLs (14,21-28) were a difference of less than 0.5 millisecond, for DMLs (14,21-26) were a difference of less than 1.0 millisecond, and for digit 4 median/ulnar comparison a difference of less than 0.6 millisecond. (14,21-24,29) When using these comparison values, prolonged latency differences in the median-ulnar DMLs in the same extremity were observed in the right upper extremities in 4 subjects (4, 12, 32, and 38). When using these comparison values, prolonged latency differences in the median-ulnar DMLs in the same extremity were also observed in both upper extremities of 5 subjects (7, 9, 11, 25, and 39). In addition, subject 39 also had a prolonged difference of 0.7 millisecond between the digit 4 median and ulnar digital DSLs comparison study in the right hand (Table 3). (30-32)

Posttraining Assessment

The preventive dental specialist course is a 12-week course that includes both didactic and clinical learning experiences. Twenty-eight of the subjects successfully completed the training to become preventive dental specialists and were tested during their last week of training (posttraining assessment). Seven of the subjects failed to complete the training due to academic or administrative problems and were not tested during the second phase (posttraining) of data collection.

History

In review of the subjects' posttraining history, the following subjects had subjective complaints suggestive of median or ulnar dysfunction: subject 5 had right wrist pain (median, pretraining complaint); subject 7 had N/T in the right palm (median, new); subject 8 had N/T left D5 (ulnar, new); subject 9 had N/T in the palm of both hands (median, new); subject 11 had right > left hand pain (median, new); subject 12 had N/T and pain in the right digit 3-4-5 and left digit 4 (ulnar, pretraining complaint); and subject 30 had N/T right digit 1 (median, new). Otherwise, from the information obtained in the history, there were no indicators suggesting median or ulnar abnormalities in the upper extremities of these subjects that had completed the preventive dental specialty course.

Screening Examination

In the posttraining screening examination, the following subjects had findings on the physical examination to suggest median or ulnar abnormalities: subject 7 had a positive Tinel's sign over the median nerve at the wrist in both hands (median, pretraining finding); subject 8 had a positive Tinel's sign over the left ulnar nerve at the elbow and wrist (ulnar, pretraining finding) and decreased sensation to light touch and pain in the palmar surface of left D5 (ulnar, new); subject 11 had a positive Tinel's sign over the right median nerve at the wrist (median, new); and subject 12 had decreased sensation to the palmar aspect of the left D5 (ulnar, new). Other than the subjects mentioned above, there were no diagnostic indicators or evidence of median and ulnar nerve abnormalities in either upper extremity of the subjects tested during the posttraining physical examination portion of the assessment.

Nerve Conduction Studies

As in the pretraining nerve conduction evaluation, when comparing the results of the study with the chart of normal values, all subjects had normal NCS values including conduction latencies, amplitudes, and conduction velocities of the median and ulnar nerves in both upper extremities. Similarly, when comparison studies between the median and ulnar palmar DSLs, digital DSLs, and DMLs in the same and opposite extremities, and the digit 4 median/ulnar comparison study in the same extremity were assessed, there were electrodiagnostic abnormalities of the median nerve at or distal to the wrist in 6 subjects (21%) involving 10 hands (18%) (Table 4). When using these comparison values, prolonged latency differences in the median-ulnar DMLs in the same extremity were observed in the right upper extremities in 2 subjects (12 and 32). When using these comparison values, prolonged latency differences in the median-ulnar DMLs in the same extremity were also observed in both upper extremities of 4 subjects (7, 9, 11, and 39). In addition, subject 12 also had a prolonged difference of 0.7 millisecond between the digit 4 median and ulnar digital DSLs comparison study in their right hand (Table 3). (30-32)

In comparing the pretraining and posttraining nerve conduction data, six of the subjects had electrodiagnostic evidence of median abnormalities at or distal to the wrist during both phases of testing. Two of the subjects (4 and 25) with electrodiagnostic evidence of median abnormalities at or distal to the wrist in the pretraining phase of data collection failed to successfully complete the preventive dental specialist course and were not tested during the posttraining phase of data collection. One subject (38) had electrodiagnostic evidence of right median nerve abnormality during the pretraining data collection, but on posttraining assessment, results of the NCS comparison studies were normal. There was no new electrodiagnostic evidence of median nerve abnormalities during the posttraining phase of data collection in the other 22 subjects. There was no statistically significant shift of the nerve conduction values in the prevalence of median neuropathies following the 12-week training program ([chi square]=0.280, P=.60).

COMMENT

To our knowledge, no studies have used histories, physical examinations, and NCS to assess the status of the median and ulnar nerves in dental assistants enrolled in a preventive dental specialist course. A thorough history and physical examination are considered essential screening tools for detecting signs and symptoms of peripheral neuropathy. (14,21-24,33) Nerve conduction measurement is often performed on the median and ulnar nerves to determine whether certain entrapment neuropathies are present. (14,21-24,33-40) Nerve conduction measurement is considered the gold standard when assessing the electrophysiologic status of the peripheral nerve. (14,21-24,33-43)

As a result of the 12-week course, 5 subjects had new complaints suggestive of median or ulnar nerve abnormalities: subject 7 (right median); subject 8 (left ulnar); subject 9 (bilateral median), subject 11 (left>right median), and subject 30 (right median). Two subjects had continuing subjective complaints of a right median nerve dysfunction (subject 5) and a left ulnar and median nerve function (subject 12).

Subject 7 had N/T in the palm of the right hand on the posttraining assessment but had a positive Tinel's sign over both median nerves at the wrist and electrodiagnostic findings of bilateral median abnormalities at or distal to the wrist in both the pretraining and posttraining assessment. Subject 8 had N/T in the left digit 5 on the posttraining physical examination as well as decreased sensation in the left digit 5. Subject 8 continued to have a positive Tinel's sign at the left ulnar nerve at the wrist and elbow suggestive of a left ulnar abnormality, however, nerve conduction testing of the left ulnar nerve was normal. Subject 9 had N/T in the palms of both hands (posttraining) suggestive of bilateral median nerve dysfunction; but there were no physical examination findings to suggest a bilateral median nerve compromise. However, subject 9 had pretraining and posttraining electrodiagnostic evidence suggestive of a bilateral median nerve abnormality at or distal to the wrist.

Subject 11 had a new finding of bilateral (right>left) hand pain and a positive Tinel's sign over the right median nerve at the wrist (pretraining) but a normal physical assessment on the posttraining examination. Subject 11 also had electrodiagnostic evidence on both the pretraining and posttraining NCS testing suggestive of bilateral median nerve abnormality. Subject 30 had a new finding of N/T of the right digit (thumb) suggestive of a right median nerve abnormality but a normal physical examination and nerve conduction studies.

Two subjects had consistent complaints during both testing sessions. Subject 5 had right wrist pain but normal physical examination and nerve conduction studies on both pretraining and posttraining assessments. Subject 12 had complaints of bilateral median and ulnar nerve dysfunction on both exams and a new loss of sensation of the left digit 5. The nerve conduction studies for subject 12 were consistent for electrodiagnostic abnormalities of the right median nerve at or distal to the wrist but the bilateral ulnar nerve studies were normal.

Of the 35 dental assistants that participated in the pretraining assessment, 14 hands (20%) in 9 subjects (26%) had electrodiagnostic abnormalities of the median nerve at or distal to the wrist. (14) Six of these 9 subjects continued with electrodiagnostic abnormalities of the median nerve at or distal to the wrist (6 subjects (21%), 10 hands (18%)). Two subjects (4 and 25) did not complete the course, and subject 38 improved his nerve conduction findings from the pretraining to posttraining assessments.

There was no statistically significant shift of the nerve conduction values in the prevalence of median neuropathies following the 12-week training program ([chi square]=0.280, P=.60). It appears that the 12-week training program did not affect the median and ulnar nerve function as assessed by physical examination and nerve conduction testing. There was no electrodiagnostic evidence on either the pretraining or posttraining nerve conduction studies to suggest ulnar nerve abnormalities at or distal to the wrist, in the forearm, or at the elbow (cubital tunnel).

Of the 35 dental assistants that participated in the pretraining assessment, 14 hands (20%) in 9 subjects (26%) had electrodiagnostic abnormalities of the median nerve at or distal to the wrist. (14) Review of the number of months the 9 dental assistants with pretraining electrodiagnostic abnormalities of the median nerve at or distal to the wrist had been practicing in the dental clinic indicated that 5 subjects had been practicing in a dental clinic greater than 12 months, and 4 subjects reported practicing less than 12 months. When considering warm-up exercises, breaks during clinical practice, and amount of time per week on the computer, playing video games, or playing a musical instrument, there were no consistent factors that separated the 9 dental assistants from the group studied. All of the 9 dental assistants that had electrodiagnostic abnormalities of the median nerve at or distal to the wrist described their general health to be good or excellent, and none of these subjects had a history of neuropathic disease, renal disease, peripheral vascular disease, thyroid disease, diabetes, or arthritis.

Dental hygienists reportedly have a high prevalence of upper-extremity musculoskeletal disorders, including CTS. (4-13) In their survey of Army dental personnel, Lalumandier and McPhee (11,12) stated that 75% of dental hygienists reported having hand problems, and 56% exhibited probable or classic symptoms of CTS. Rice et al (13) reported symptoms associated with CTS were noted by 75.6% of the dental workers, 11% reported diagnosed CTS, and 53% reported back and shoulder pain. With the documented incidence of carpal tunnel syndrome in dentists and dental hygenists, there are no studies, to our knowledge, that have documented the incidence of carpal tunnel syndrome in dental assistants enrolled in a preventive dental specialist course. The present study demonstrated that electrodiagnostic abnormalities of the median nerve at or distal to the wrist or carpal tunnel syndrome is present in 9 Army subjects (26%) pretraining and 6 subjects (21%) posttraining. However, only 2 of the 9 subjects had objective findings on the clinical examination suggestive of median nerve dysfunction.

In a population such as the dental assistants studied here, it is reasonable to expect that subclinical upper extremity mononeuropathies secondary to repetitive overuse may be present. In the early stages of a mononeuropathy of this type, many individuals with a clinically detectable problem are not aware that their neural function has been impaired. (44) Atroshi et al (44) examined 125 asymptomatic controls with NCS of the median nerves and reported that 18% (n=23) had electrophysiological evidence of carpal tunnel syndrome.

Atroshi et al (44) have stated that the estimation of the prevalence of carpal tunnel syndrome in a general population may contribute to the early diagnosis and effective treatment of subjects and provide useful data for the interpretation of results that estimate the prevalence of carpal tunnel syndrome in specific occupational groups. Franzblau and Werner (45-47) further suggest that performing NCS of individuals without symptoms of carpal tunnel syndrome is important because it permits the assessment of the overall relationship between the electrophysiological properties of the nerve and other clinical features of carpal tunnel syndrome. Although no strong evidence exists regarding the prevention or progression of CTS, it makes sense, theoretically, to identify a problem early, where a minor intervention, such as a resting night splint or ergonomic changes in the work environment, might rectify the dysfunction. (45-47)

A valuable extension of this study would be evaluations of these preventive dental specialists as they progress through their dental health careers, and to reevaluate them in 5 to 10 years to determine whether the individuals who presented with early electrodiagnostic abnormalities of median nerve at or distal to the wrist later develop symptomatic carpal tunnel syndrome.

CONCLUSION

This study examined a sample of35 Army dental assistants during their training to become preventive dental specialists for the presence of clinical and electrodiagnostic abnormalities of the median and ulnar nerves. All electrophysiological variables were normal for motor, sensory, and F-wave (central) values when compared to a chart of normal values in both the pretraining and posttraining assessments. Based on comparison studies of median and ulnar motor latencies in the same hand, 14 hands (20%) among 9 subjects (26%) were found to have electrodiagnostic abnormalities of the median nerve at or distal to the wrist at the pretraining assessment. (14) During post-training assessment, there were no new cases of electrodiagnostic median nerve abnormalities and no statistically significant shift of the nerve conduction values in the prevalence of median neuropathies following the 12-week training program. Ulnar nerve electrophysiological function was within normal limits for all subjects examined. Nerve conduction comparison studies may provide sensitive measures and early indicators for the detection of early median nerve compromise at or distal to the wrist. Additional long-term prospective studies examining the prevalence and prevention of upper extremity disorders, to include carpal tunnel, appear to warrant further investigation.

Acknowledgement

The authors thank COL Robert Lutka, SFC Charles A. Aponte, SFC Heide C. Mayberry, SFC Michael C. Mason, and SSG Gerald M. Bradford (AMEDD Center and School, Fort Sam Houston, Texas) for their support of this study and their assistance in recruiting the dental assistants who participated.

References

(1.) Franklin GM, Haug J, Heyer N, Checkoway H, Peck N. Occupational carpal tunnel syndrome in Washington State, 1984-1988. Am J Public Health. 1991;81(6):741-746.

(2.) Hanrahan LP, Higgins D, Anderson H, Haskins L, Tai S. Project SENSOR: Wisconsin surveillance of occupational carpal tunnel syndrome. Wis Med J. 1991;90(2):80-83.

(3.) Stockstill JW, Harn SD, Strickland D, Hruska R. Prevalence of upper extremity neuropathy in a clinical dentist population. J Am Dent Assoc. 1993;124(8):67-72.

(4.) Anton D, Rosecrance J, Melino L, Cook T. Prevalence of musculoskeletal symptoms and carpal tunnel syndrome among dental hygienists. Am J Ind Med. 2002;42(3):248-257.

(5.) Conrad JC, Conrad KJ, Osborn JB. A short-term, three-year epidemiological study of median nerve sensitivity in practicing dental hygienists. J Dent Hyg. 1993;67(5):268-272.

(6.) Corks I. Occupational health hazards in dentistry: musculoskeletal disorders. Ont Dent. 1997;74(6):27-30.

(7.) Guay AH. Commentary: ergonomically related disorders in dental practice. J Am Dent Assoc. 1998;129(2):184-186.

(8.) Osborn JB, Newell KJ, Rudney JD, Stoltenberg JL. Carpal tunnel syndrome among Minnesota dental hygienists. J Dent Hyg. 1990;64(2):79-85.

(9.) Werner RA, Hamann C, Franzblau A, Rodgers PA. Prevalence of carpal tunnel syndrome and upper extremity tendinitis among dental hygienists. J Dent Hyg. 2002;76(2):126-132.

(10.) Cherniack M, Brammar AJ, Nilsson T, et al. Nerve conduction and sensorineural function in dental hygienists using high frequency ultrasound handpieces. Am J Ind Med. 2006;49(5):313-326.

(11.) Lalumandier JA, McPhee SD. Prevalence and risk factors of hand problems and carpal tunnel syndrome among dental hygienists. J Dent Hyg. 2001;75(2):130-134.

(12.) Lalumandier JA, McPhee SD, Riddle S, Shulman JD, Daigle WW. Carpal tunnel syndrome: effect on Army dental personnel. Mil Med. 2000;165(5):372-378.

(13.) Rice VJ, Nindl B, Tentikis JS. Dental workers, musculoskeletal cumulative trauma, and carpal tunnel syndrome. Who is at risk? A pilot study. Int J Occup Saf Ergon. 1996;2(3):218-233.

(14.) Greathouse DG, Root RM, Carrillo CR, Jordan CL, Pickens BB, Sutlive TG, Shaffer SW, Moore JS. Clinical and electrodiagnostic abnormalities of the median nerve in dental assistants. J Orthop Sports Phys Ther. 2009;39(9):693-701.

(15.) Macdonald G, Robertson MM, Erickson JA. Carpal tunnel syndrome among California dental hygienists. Dent Hyg. 1988;62:322-327.

(16.) Werner RA, Armstrong TJ. Carpal tunnel syndrome: ergonomic risk factors and intracarpal canal pressure. Phys Med Rehabil Clin N Am. 1997;8(3):555-569.

(17.) Bramson JB, Smith S, Romagnoli G. Evaluating dental office ergonomics: risk factors and hazards. J Am Dent Assoc. 1998;129(2):174-183.

(18.) Dutton M. Orthopaedic Examination, Evaluation, & Intervention. New York, NY: McGraw-Hill Medical Publishing Division; 2005.

(19.) Magee DJ. Orthopaedic Physical Assessment. Philadelphia: W.B. Saunders; 1992.

(20.) Harkins G, Jayne D, Masullo L, et al. Effects of gender and handedness on neural conductions in humans. J Clin Electrophysiol. 1989;1:10-13.

(21.) Jablecki CK. Practice parameter for electrodiagnostic studies in carpal tunnel syndrome: summary statement: American Association of Electrodiagnostic Medicine, American Academy of Neurology, American Academy of Physical Medicine and Rehabilitation. Muscle Nerve. 1993;16(12):1390-1391.

(22.) Dumitru D, Amato A, Zwarts M. Electrodiagnostic Medicine. 2nd ed. St. Louis, MO: Hanley & Belfus; 2002.

(23.) Kimura J. Electrodiagnosis in Diseases of Nerve and Muscle: Principles and Practice. 3rd ed. New York: Oxford University Press; 2001.

(24.) Oh SJ. Clinical Electromyography in Nerve Conduction Studies. Baltimore, MD: Williams & Wilkins; 1993.

(25.) Daube JR. Percutaneous palmar median nerve stimulation for carpal tunnel syndrome. Electroencephalogr Clin Neurophysiol. 1977;43:139-140.

(26.) Felsenthal G. Carpal tunnel syndrome diagnosis. Arch Phys Med Rehabil. 1979;60-90.

(27.) Felsenthal G. Median and ulnar distal motor latencies in the same normal subject. Arch Phys Med Rehabil. 1977;58:297-302.

(28.) Felsenthal G, Spindler H. Palmar conduction time of median and ulnar nerves of normal subjects and patients with carpal tunnel syndrome. Am J Phys Med Rehabil. 1979;58:131-138.

(29.) Johnson EW, Kukla RD, Wongsam PE, et al. Sensory latencies to the ring finger. Normal values and relation to carpal tunnel syndrome. Arch Phys Med Rehabil. 1981;62:206-208.

(30.) Uncini A, Lange DJ, Solomon M, et al. Ring finger testing in carpal tunnel syndrome: a comparative study of diagnostic utility. Muscle Nerve. 1989;12:735-741.

(31.) Uncini A, DiMuzio A, Cutarella R, et al. Orthodromic median and ulnar fourth digit sensory conductions in mild carpal tunnel syndrome. Neurophysiol Clin. 1990;20:53-61.

(32.) van Dijk JG. Multiple tests and diagnostic validity. Muscle Nerve. 1995;18:353-355.

(33.) MacDermid JC, Doherty T. Clinical and electrodiagnostic testing of carpal tunnel syndrome: a narrative review. J Orthop Sports Phys Ther. 2004;34:565-588.

(34.) Jablecki CK, Andary MT, So YT, et al. Literature review of the usefulness of nerve conduction studies and electromyography for the evaluation of patients with carpal tunnel syndrome. Muscle Nerve. 1993;16:1392-1414.

(35.) Jablecki CK, Andary MT, Floeter MK, et al. Practice parameter: electrodiagnostic studies in carpal tunnel syndrome. Report of the American Association of Electrodiagnostic Medicine, American Academy of Neurology, and the American Academy of Physical Medicine and Rehabilitation. Neurology. 2002;58:1589-1592.

(36.) Jackson DA, Clifford JC. Electrodiagnosis of mild carpal tunnel syndrome. Arch Phys Med Rehabil. 1989;70(3):199-204.

(37.) MacDermid JC, Wessel J. Clinical diagnosis of carpal tunnel syndrome. A systematic review. J Hand Ther. 2004;17:309-319.

(38.) Melvin JL, Schuchmann JA, Lanese RR. Diagnostic specificity of motor and sensory nerve conduction variables in the carpal tunnel syndrome. Arch Phys Med Rehabil. 1973;54:69-74.

(39.) Moore J. Carpal tunnel syndrome. Occup Med. 1992;7(4):741-763.

(40.) National Institute of Occupational Safety and Health. Carpal tunnel syndrome. In: Bernard BP, ed. Musculoskeletal Disorders and Workplace Factors. Washington, DC: US Department of Health and Human Services; 1997:1-29. DHHS publication 97-144.

(41.) Redmond MD, Rivner MH. False positive electrodiagnostic tests in carpal tunnel syndrome. Muscle Nerve. 1988;11(5):511-518.

(42.) Salerno DF, Franzblau A, Werner RA, Bromberg MB, Armstrong TJ, Albers JW. Median and ulnar nerve conduction studies among workers: normative values. Muscle Nerve. 1998;21:999-1005.

(43.) Scelsa SN, Herskovitz S, Bieri P, Berger AR. Median mixed and sensory nerve conduction studies in carpal tunnel syndrome. Electroenceph Clin Neurophysiol. 1998;109:268-273.

(44.) Atroshi I, Gummesson C, Johnsson R, Ornstein E, Ranstam J, Rosen I. Prevalence of carpal tunnel syndrome in a general population. JAMA. 1999;292 (2):153-158.

(45.) Franzblau A, Werner RA, Valle J, Johnston E. Workplace surveillance for carpal tunnel syndrome. J Occup Rehabil. 1993;3(1):1-14.

(46.) Franzblau A, Werner RA, Albers JW, Olinski D, Johnston E. Workplace surveillance for carpal tunnel syndrome using hand diagrams. J Occup Rehabil. 1994;4(4):185-198.

(47.) Franzblau A, Werner R. What is carpal tunnel syndrome?. JAMA. 1999;282:186-187.

David G. Greathouse, PhD, PT

1LT Tiffany M. Root, SP, USA

CPT Carla R. Carrillo, SP, USA

1LT Chelsea L. Jordan, SP, USA

1LT Bryan B. Pickens, SP, USA

Thomas G. Sutlive, PhD, PT

LTC Scott W. Shaffer, SP, USA

COL Josef H. Moore, SP, USA

* Military occupational specialty.

Dr Greathouse is Director, Clinical Electrophysiology Services, Texas Physical Therapy Specialists, New Braunfels, Texas, and Adjunct Professor, US Army-Baylor University Doctoral Program in Physical Therapy, Fort Sam Houston, Texas.

1LT Root is a staff physical therapist at Ireland Army Community Hospital, Fort Knox, Kentucky. At the time of this study, she was a student in the US Army-Baylor University Doctoral Program in Physical Therapy, Fort Sam Houston, Texas.

CPT Carrillo is a staff physical therapist at Evans Army Community Hospital, Fort Carson, Colorado. At the time of this study, she was a student in the US Army-Baylor University Doctoral Program in Physical Therapy, Fort Sam Houston, Texas.

1LT Jordan is a staff physical therapist at Madigan Army Medical Center, Fort Lewis, Washington. At the time of this study, she was a student in the US Army-Baylor University Doctoral Program in Physical Therapy, Fort Sam Houston, Texas.

1LT Pickens is a staff physical therapist at Reynolds Army Community Hospital, Fort Sill, Oklahoma. At the time of this study, he was a student in the US Army-Baylor University Doctoral Program in Physical Therapy, Fort Sam Houston, Texas.

Dr Sutlive is an Associate Professor, US Army-Baylor University Doctoral Program in Physical Therapy, Fort Sam Houston, Texas.

LTC Shaffer is an Associate Professor, US Army-Baylor University Doctoral Program in Physical Therapy, Fort Sam Houston, Texas.

COL Moore is Professor and Program Director, US Army-Baylor University Doctoral Program in Physical Therapy, Fort Sam Houston, Texas.
Table 1. Subjects with positive findings on special tests of
the upper extremities (pretraining). *

Subject  Hand   Tinel's Sign  Tinel's Sign  Tinel's Sign  Phalen's
                  at wrist      at wrist      at elbow      Test
                  (median)      (ulnar)       (ulnar)

7        Left   X
7        Right  X ([dagger])
8        Left                      X             X
10       Right  X
11       Right  X ([dagger])
14       Left                                    X
29       Left   X
32       Right                     X             X
32       Left                                    X
35       Right  X                  X             X
35       Left   X                  X             X
38       Left   X                                            X
38       Right  X                                            X
41       Right  X                                            X

* Data from Greathouse et al.14 Reproduced with permission.

([dagger]) Subjects with electrodiagnostic abnormalities of the
median nerve or distal to the wrist.

Table 2. Mean, standard deviation, and range of values for neural
conduction measurements (pretraining, n = 35). *

                                   Right upper extremity

          Median nerve             Mean      SD      Range

             Motor

DML (ms)                            3.5     0.4     2.8-4.2
Amp CMAP (mV)                       9.0     2.7     5.0-14
MNCV BE--W (meters per second)     58.4     3.6      50-68
            Sensory

Palmar DSL (ms)                     1.8     0.2     1.6-2.2
Palmar Amp SNAP ([micro]V)         78.5    36.9      24-164
2 Digit DSL (ms)                    2.9     0.2     2.5-3.5
2 Digit Amp SNAP ([micro]V)        32.8    19.9      15-110
F-Wave (ms)                        26.2     2.1    21.6-30.3

          Ulnar nerve
             Motor

DML (ms)                            2.6     0.3     2.2-3.3
Amp CMAP (mV)                       8.5     2.3       5-14
MNCV BE--W (meters per second)     60.9     5.9      50-73
MNCV AE--BE (meters per second)    67.2     8.8      52-96

            Sensory

Palmar DSL (ms)                     1.7     0.1     1.4-2.0
Palmar Amp SNAP ([micro]V)         39.0    24.1      15-110
5 Digit DSL (ms)                    2.9     0.2     2.4-3.4
5 Digit Amp SNAP ([micro]V)        36.2    34.0      15-164
F-Wave (ms)                        26.2     2.4    20.7-31.2

                                   Left upper extremity        Normal
                                                               Values
          Median nerve             Mean      SD      Range

             Motor

DML (ms)                            3.4     0.4     2.7-4.1      <4.2
Amp CMAP (mV)                       8.7     2.5     5.0-17       >5.0
MNCV BE--W (meters per second)     59.2     4.0      51-68      >50.0
            Sensory

Palmar DSL (ms)                     1.8     0.1     1.6-2.1      <2.2
Palmar Amp SNAP ([micro]V)         72.9    35.4      15-144     >15.0
2 Digit DSL (ms)                    2.8     0.2     2.5-3.3      <3.5
2 Digit Amp SNAP ([micro]V)        30.8    12.9      15-83      >15.0
F-Wave (ms)                        25.8     2.1    21.5-29.6    <32.0

          Ulnar nerve
             Motor

DML (ms)                            2.7     0.3     2.2-3.2      <3.6
Amp CMAP (mV)                       8.0     1.9       5-12       >5.0
MNCV BE--W (meters per second)     60.5     4.1      54-72      >50.0
MNCV AE--BE (meters per second)    64.4     8.0      54-92      >50.0

            Sensory

Palmar DSL (ms)                     1.7     0.1     1.5-2.1      <2.2
Palmar Amp SNAP ([micro]V)         35.0    20.0      15-99      >15.0
5 Digit DSL (ms)                    2.9     0.2     2.4-3.3      <3.5
5 Digit Amp SNAP ([micro]V)        30.6    20.6      15-101     >15.0
F-Wave (ms)                        26.2     2.1    22.5-31.3    <32.0

* Data from Greathouse et al. (14) Reproduced with permission.

AE indicates above elbow; Amp, amplitude; BE, below elbow; CMAP,
compound motor action potential; DML, distal motor latency; DSL,
distal sensory latency; MNCV, motor nerve  conduction velocity;
SNAP, sensory nerve action potential; W, wrist.

Table 3: Subjects with positive findings on neural conduction
comparison studies (pretraining). *

                 Palmar DSL (ms)

Subject   Hand   Median   Ulnar     Difference

004        R      1.7      1.8         0.1
           L      1.8      1.8         0.0
007        R      1.8      1.6         0.2
           L      2.0      1.5         0.5
009        R      1.8      1.5         0.3
           L      1.8      1.7         0.1
011        R      1.7      1.6         0.1
           L      1.7      1.7         0.0
012        R      2.0      1.6         0.4
           L      1.9      1.6         0.3
025        R      2.2      1.7         0.5
           L      1.9      1.6         0.3
032        R      2.1      1.8         0.3
           L      1.9      1.8         0.1
038        R      1.9      1.8         0.1
           L      2.0      1.8         0.2
039        R      2.0      1.6         0.4
           L      2.0      1.5         0.5

                 Digital DSL (ms)

Subject   Hand   Median   Ulnar      Difference

004        R      2.7      2.8          0.1
           L      2.7      2.7          0.0
007        R      2.8      2.4          0.4
           L      2.6      2.4          0.2
009        R      2.8      2.6          0.2
           L      2.6      2.8          0.2
011        R      2.5      2.8          0.3
           L      2.5      2.7          0.2
012        R      3.1      2.8          0.3
           L      2.8      2.7          0.1
025        R      3.2      3.1          0.1
           L      3.0      2.9          0.1
032        R      3.1      3.2          0.1
           L      2.8      2.9          0.1
038        R      3.0      2.9          0.1
           L      3.3      3.3          0.0
039        R      3.0      2.7          0.3
           L      3.0      2.6          0.4

                 DML (ms)

Subject   Hand   Median   Ulnar      Difference

004        R      3.9      2.6     1.3 ([dagger])
           L      3.6      2.9     0.7
007        R      3.9      2.3     1.3 ([dagger])
           L      3.4      2.3     1.1 ([dagger])
009        R      3.4      2.3     1.1 ([dagger])
           L      3.8      2.2     1.6 ([dagger])
011        R      4.2      2.2     2.0 ([dagger])
           L      3.8      2.3     1.5 ([dagger])
012        R      3.7      2.4     1.3 ([dagger])
           L      3.2      2.3     0.9
025        R      4.0      2.4     1.6 ([dagger])
           L      3.7      2.6     1.1 ([dagger])
032        R      4.1      3.0     1.1 ([dagger])
           L      3.7      3.1     0.6
038        R      4.0      2.7     1.3 ([dagger])
           L      3.6      3.1     0.5
039        R      3.8      2.4     1.4 ([dagger])
           L      3.9      2.6     1.3

                 D4 DSL (ms)

Subject   Hand   Median   Ulnar      Difference

004        R      2.8      2.8     0.0
           L      2.8      2.7     0.1
007        R      2.9      2.5     0.4
           L      3.1      2.6     0.5
009        R      2.8      2.5     0.3
           L      2.7      2.7     0.0
011        R      2.5      2.4     0.1
           L      2.6      2.5     0.1
012        R      3.2      2.8     0.4
           L      2.9      2.6     0.3
025        R      3.3      2.8     0.5
           L      3.2      3.0     0.2
032        R      3.4      3.0     0.4
           L      3.2      2.8     0.4
038        R      3.2      3.1     0.1
           L      3.6      3.4     0.2
039        R      3.1      2.4     0.7 ([dagger])
           L      3.3      2.9     0.4

* Data from Greathouse et al. (14) Reproduced with permission.

([dagger]) Indicates electrodiagnostic abnormalities of the
median nerve.

DSL indicates distal sensory latency; DML, distal motor latency.

NOTE: Prolonged DML difference > 1.0 millisecond (normal < 1.0
millisecond).

Prolonged D4 median/ulnar difference > 0.6 millisecond (normal <
0.6 millisecond).

Table 4: Subjects with positive findings on neural conduction
comparison studies (posttraining).

                  Palmar DSL (ms)

Subject   Hand    Median   Ulnar   Difference

007        R       1.8      1.5       0.3
           L       1.9      1.7       0.2
009        R       1.8      1.6       0.2
           L       1.7      1.7       0.0
011        R       1.7      1.7       0.0
           L       1.6      1.8       0.2
012        R       2.2      1.7       0.5
           L       2.1      1.8       0.3
032        R       2.0      1.8       0.2
           L       1.8      1.7       0.1
039        R       2.0      1.8       0.2
           L       2.0      1.7       0.3

                  Digital DSL (ms)

Subject   Hand    Median   Ulnar   Difference

007        R       2.8      2.6       0.2
           L       2.8      2.7       0.1
009        R       2.8      2.8       0.0
           L       2.6      2.8       0.2
011        R       2.7      3.0       0.3
           L       2.6      2.8       0.2
012        R       3.2      2.9       0.3
           L       3.1      3.1       0.0
032        R       2.8      2.8       0.0
           L       2.6      2.6       0.0
039        R       3.0      2.8       0.2
           L       3.0      2.7       0.3

                  DML (ms)

Subject   Hand    Median   Ulnar   Difference

007        R       3.7      2.5       1.2
           L       3.8      2.7       1.1
009        R       3.6      2.5       1.1
           L       3.6      2.1       1.5
011        R       4.2      2.9       1.3
           L       4.1      2.7       1.4
012        R       4.0      2.9       1.1
           L       3.6      3.1       0.5
032        R       3.7      2.6       1.4
           L       3.4      2.7       0.7
039        R       4.2      2.8       1.4
           L       3.9      2.5       1.4

                  D4 DSL (ms)

Subject   Hand    Median   Ulnar   Difference

007        R       2.9      2.6       0.3
           L       3.2      2.6       0.6
009        R       3.0      2.6       0.4
           L       2.8      2.7       0.1
011        R       3.0      2.9       0.1
           L       2.8      2.7       0.1
012        R       3.5      2.8       0.7
           L       3.3      3.0       0.3
032        R       2.9      2.8       0.1
           L       2.8      2.8       0.0
039        R       3.1      2.7       0.4
           L       3.2      2.6       0.6

DSL indicates distal sensory latency; DML, distal motor latency.

Prolonged DML difference > 1.0 millisecond (normal < 1.0
millisecond).

Prolonged D4 median/ulnar difference > 0.6 millisecond (normal
< 0.6 millisecond).

Subjects 004 and 025 did not complete the preventive dental
specialist training, and therefore did not participate in the
posttraining assessment.
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Author:Greathouse, David G.; Root, Tiffany M.; Carrillo, Carla R.; Jordan, Chelsea L.; Pickens, Bryan B.; S
Publication:U.S. Army Medical Department Journal
Article Type:Clinical report
Geographic Code:1USA
Date:Jan 1, 2011
Words:8078
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