Defending the Wrist Deviation Test for Carpal Tunnel Syndrome Screening: A Comparison of Vibration Thresholds and Distal Motor Latency

Transcription

1 INTERNATIONAL JOURNAL OF OCCUPATIONAL SAFETY AND ERGONOMICS 1996, VOL. 2, NO. 4, Defending the Wrist Deviation Test for Carpal Tunnel Syndrome Sreening: A Comparison of Vibration Thresholds and Distal Motor Lateny Keith M. White Texas Instruments, USA Jerome J. Congleton Olga J. Pendleton R. Dale Huhingson Rodger J. Koppa Texas A&M University, USA This researh used distal m otor lateny (DML) and vibration thresholds (VT) to evaluate 84 hand ativity and w rist deviation ombinations to determine the best assoiation w ith arpal tunnel syndrome (CTS). Female volunteers, 2 healthy and 2 CTS diagnosed, were age mathed and operated a keyboard for 4 hrs a day. Room temperature was 28 C( ± 2). Beginning DML and VT were taken w ith a relaxed neutral posture hand. The wrist was deviated in a random ly seleted om bination, and determinations were taken at 5-min intervals. The trial ended at 20 min or when disom fort was felt. The CTS onditions were disriminated by pain four times, DML one, and VT 14 times. Vibrom etry was the most onsistent CTS disriminator. The best VT results for w rist positions were obtained w ith w rist extension and extended extension, whereas the unlenhed, lenhed, and loaded power grip ativities proved to be the most onsistent hand ativities. arpal tunnel syndrome distal m otor lateny nerve ondution vibration threshold vibrom etry 1. INTRODUCTION In 1951, George Phalen first desribed and reported a positive arpal tunnel syndrome (CTS) indiation of 80% in 484 hands with the wrist flexion test. In this test, 30 to 60 s of unfored, omplete flexion of the wrist reprodued or exaggerated the patient s CTS symptoms (Phalen, 1951). It is widely known that wrist flexion-extension and hand ativity inrease arpal anal pressures (Gelberman, Hergenroeder, Hargens, Lundborg, & Akeson, 1981; Luhetti et al., 1989; Okutsu, 1989; Rojviroj et al., 1990; Seradge, Jia, & Owens, 1995; Smith, Sontegard, & Anderson, 1977; Werner, Elmqvist, & Ohlin, 1983). Subsequent researh provoking elevated anal pressures to assist CTS sreening tehniques has been limited to a relaxed hand with passive wrist flexion or extension or dynami flexion and extension (Borg & Linblom, 1986; Dunnan & Waylonis, 1991; Gellman, Gelberman, Tan, & Botte, 1986; Koris, Gelberman, Dunan, Boublik, & Smith, 1990; Marin, Vernik, & Friedmann, 1983; Shwartz, Gordon, & Swash, 1980; Szabo & Chidgey, 1989). Additionally, flexor tendon loading during flexion and extension I would like to thank the administration of Sterling C. Evans Library, Texas A&M University for their support. I espeially thank the researh partiipants, Carolyn, Florienia, Jakie, and Melanie for their patiene and perseverane in this study. Names aknowledged with partiipant permission. Correspondene and requests for reprints should be sent to Keith M. White, P.O. Box 20788, Wao, TX 76702, USA. < KMW9@ti.om>. 315

2 316 K.M. WHITE, J.J. CONGLETON, O.J. PENDLETON, R.D. HUCHINGSON, AND R.J. KOPPA (Smith et al., 1977) and ontration of wrist and finger musles (Werner et al., 1983) were found to elevate arpal anal pressures above passive flexion or extension. This led to a more CTS-sensitive linial method using Phalen s test modified with the patient forefully pinhing the thumb against the index and middle fingers (Smith et al., 1977). Even with these modifiations, the need still exists to find better diagnosti tools or improved methods easily used by a liniian (Grant, Congleton, Koppa, Lessard, & Huhingson, 1992). Other hand ativity and wrist position ombinations may provide better information to diagnose the patient s true CTS ondition. Previous researh provides no systemati justifiation for the positions used for provoative testing. Additionally, a substantial literature searh and disussions with several orthopedi speialists have revealed no attempts to explore other ombinations. The purpose of this researh was to evaluate 84 hand ativity and wrist deviation ombinations to determine the best assoiation with CTS. This study is designed to provide a base for future researh on appliations of provoative testing. This need is essential beause eletrodiagnosti tests may provide false negative determinations in early or mild CTS ases (Kothari et al., 1995). Ultimately, two of the most promising ombinations will be tested with a larger sample size to onfirm the findings of this study. A seondary goal, established to minimize peripheral equipment and provide methods that ould be immediately used in a linial setting, was to develop these ombinations without the use of orthotis. 2. MATERIAL A ND METHODS The NervePae Eletroneurometer Model S-1 was used to determine the distal motor lateny (DML) aross the arpal anal. This devie...provides an aurate measurement of the distal motor lateny... (Osterman, Aversa, & Greenstein, 1989), is highly orrelated to standard EMG tehniques (Rosier & Blair, 1984) and has been used favorably in other studies (Feierstein, 1988; Grant, 1990). The stimulus is applied to the skin 3 m proximal to the distal flexor wrist rease over the median nerve. The nerve impulse is piked up by eletrodes plaed 4 m distal to the distal flexor wrist rease (Neurotron Medial, personal ommuniation, July, 1992) over the abdutor polliis brevis musle. Total stimulus-to-eletrode pikup is 7 m. The time between delivery of stimulus and onset of the ation potential is displayed in milliseonds (ms) on the front of the Eletroneurometer. TTie Vibratron (Physitemp Instruments, Clifton, NJ) was used to evaluate the 120-Hz vibration threshold (VT) on the pad of the third fingertip (Phalen, 1951). The vibration units shown on the front panel digital display are related to the true peak-to-peak amplitude (A) in mirons of the vibration by the formula A =.5X2 (Physitemp Instruments, 1991). The method of limits proedure was used to obtain the VT (Goldberg & Lindblom, 1979). The subliminal or supraliminal starting value was randomized for eah test session for eah partiipant. The two thresholds were averaged for the VT. Eighty-four trials, eah with a different hand ativity and wrist position ombination, were performed on 4 female volunteers. The partiipants were asked to appear for evaluations as many times a day as possible but allowing a minimum of 1 hr between evaluations. All 4 partiipants were involved in ativities that required keyboard operation for an average of 4 hrs a day during the work week. Partiipants 1 and 2 were available for testing after work hours and on Saturday and Sunday. Partiipants 1 and 2 were 33 years old, healthy, and showing no symptoms of CTS. The dominant hand of Partiipant 1 was tested, whereas the nondominant hand of Partiipant 2 was tested. Partiipant 3 was 30 years old and had been linially diagnosed in her dominant hand with a mild level of CTS 6 months prior to the study. Her treatment onsisted primarily of avoiding positions that aggravate the ondition and wearing a wrist splint as needed. Her reovery seemed to be progressing very well with rare displays of CTS symptoms. Partiipant 4 was 32 years old and had been linially diagnosed 2 weeks prior to this study with a borderline moderate level of CTS in her dominant hand. Results of her bilateral eletrodiagnosti testing inluded:

3 WRIST DEVIATION TESTS FOR CTS Median distal motor lateny (DML) of 3.45 ms in the right (dominant) hand and 3.60 ms in the left. Ulnar DML of 2.40 ms in the right (dominant) hand and 2.60 ms in the left. Distane for eah DML was 8 m. Median motor ondution veloity was 70 m/s through the right elbow and 73 m/s through the left. Ulnar motor ondution veloity was 59 m/s through the right elbow and 70 m/s through the left. T1 plaement was 8 m, and T2 plaements were D3 and D4 proximal to the elbow. 2. Antidromi median distal sensory lateny (DSL) in the seond digit of 3.45 ms in the right (dominant) hand and 2.60 ms in the left. Antidromi ulnar distal sensory lateny (DSL) in the seond digit of 2. ms in the right (dominant) hand and 2.22 ms in the left. Distane for eah DSL was 14 m. SNAP was 8 mv right and 7 mv left. Her treatment onsisted of wearing a wrist brae periodially to relieve symptoms. The dominant, CTS positive, hand of Partiipants 3 and 4 were tested. No partiipant had or was expeted to have orretive surgery, and no partiipant had reurring parenthesia in their hands at night. As loading or tensing of the flexor tendons inrease anal pressures (Smith et al., 1977; Werner et al., 1983), hand ativities onentrated on progressive tendon loading using the power and huk key pinh grip. The hand ativities studied inluded the hand in the following postures: 1. No hand ativity: The hand is in the most relaxed state possible. 2. Unlenhed power grip: The hand is in a power grip position, but the grip fore is only enough to maintain the posture. 3. Unlenhed huk key pinh grip: The hand is in a pinh grip of the first three digits, but the pinh fore is only enough to maintain the posture. 4. Clenhed power grip: The hand is in a power grip position with a tensed grip. 5. Clenhed huk key pinh grip: The hand is in a pinh grip position with a tensed pinh. The partiipants were asked to pinh hard enough to maintain a white appearane under the ends of the nails and at the tips of the fingers. 6. Loaded power grip: A Model Hand Dynamometer (Lafayette Instrument, Lafayette, IN) was used to generate loaded gripping onditions. The partiipant was asked to maintain half the maximal neutral wrist fore. The devie grip span was adjusted to the most omfortable position determined by the partiipant. 7. Loaded huk key pinh grip: A Model PG-30 B&L Pinh Gauge (Lafayette Instrument, Lafayette, IN) was used to generate loaded pinh onditions of the first three digits. The partiipant was asked to maintain half the maximal neutral wrist fore. 8. Stati wrist with unloaded flexion and extension of the power grip: The partiipant maintained a fixed wrist deviation and flexed and extended the hand and digits in a power grip. The partiipant was asked to apply a slight amount of fore when applying the grip. 9. Stati wrist with unloaded flexion and extension of the huk key pinh grip: The partiipant maintained a fixed wrist deviation and fully flexed and extended the first three digits in a pinh grip. The partiipant was asked to apply enough fore when applying the grip to ause a white appearane under the ends of the nails and at the tips of the fingers. 10. Stati wrist with loaded flexion and extension of the power grip: The partiipant maintained a fixed wrist deviation and flexed and extended the hand while ompressing the hand dynamometer to half of the maximum resting value. 11. Stati wrist with loaded flexion and extension of the huk key pinh grip: The partiipant maintained a fixed wrist deviation and flexed and extended the first three digits while ompressing a 2.5-kg spring. 12. Dynami wrist with an unloaded power grip: The partiipant atively moved the wrist while simultaneously flexing and extending a power grip. 13. Dynami wrist with an unloaded huk key pinh grip: The partiipant atively moved the wrist while simultaneously flexing and extending a pinh grip, ompressing the hand dynamometer to half of the maximum resting value. 14. Dynami wrist with a loaded power grip: The partiipant atively moved the wrist while

4 318 K.M. WHITE, J.J. CONGLETON, O.J. PENDLETON, R.D. HUCHINGSON, AND R.J. KOPPA simultaneously flexing and extending the hand as she ompressed the hand dynamometer to half of the maximum resting value. 15. Dynami wrist with a loaded huk key pinh grip: The partiipant atively moved the wrist while simultaneously flexing and extending the first three digits and ompressing a 2.5-kg spring. Eah hand ativity and wrist deviation ombination were unfored, but to maximum extent possible by the partiipant. In a preliminary study using simple unfored deviations, the partiipant often unonsiously allowed the wrist to move or reep to a more omfortable position. Assuming reep dereases anal pressures, two extended wrist positions were added to the protool. The extended wrist deviations required the partiipant to push with the untested hand on the dorsal or volar portion of the distal segments of the seond and third metaarpal area of the tested hand. Speifially, extended extension required the partiipant to push on the volar portion of the seond or third metaarpal area. Extended flexion required the partiipant to push on the dorsal portion of the seond or third metaarpal area. Dynami wrist flexion and extension have demonstrated high anal pressures (Szabo & Chidgey, 1989). For dynami ativities, the partiipant atively moved the wrist in a radial/ulnar or flexion/extension fashion while simultaneously performing a hand ativity. The rate of motion was about 1 yle per s. The wrist deviations ombined with the hand ativities inluded: 1. Neutral (no deviation) 2. Radial deviation 3. Ulnar deviation 4. Flexion 5. Extension 6. Extended flexion 7. Extended extension The matrix of hand ativity by wrist position (Table 7) indiates 84 of the possible 105 trials were tested. The no hand ativity by neutral posture is the traditional VT determination posture and, therefore, not an ativity of onern for the purpose of this artile. The remaining 20 ombinations not tested inluded dynami wrist (DW) ativities. Of these, the neutral wrist posture is not possible beause the DW requires wrist movement. The remaining DW ativities are movements between stati posture assignments, and thus only one is used for reporting results. Speifially, the DW ativity alternates between radial to ulnar deviations. The results only need reporting one and are found in the olumn for radial wrist position. Extension and flexion share the same reasoning. Extended wrist positions were not possible beause the yle time of the dynami ativity did not permit partiipant loading of the hand to keep it from reeping to a more omfortable posture. Beause testing was onduted with a room temperature of 28 C ( ± 2), skin temperature was not reorded (Kimura, 1983). After 20 min alimation to the ambient temperature, the test was administered to the seated researh partiipant. The test began with DML and VT determinations with a relaxed hand and neutral posture wrist. The wrist was then deviated in a randomly seleted hand ativity and wrist deviation ombination. The DML and VT determinations were taken at intervals of 1,5,10,15, and 20 min. Eah determination was taken with a relaxed hand while the partiipant maintained as muh of the wrist deviation as possible. The DML determinations were not possible in flexion or extended flexion as the stimulus probe ould not be appropriately positioned to the stimulus site. For this position, DML determinations were taken immediately at the onlusion of the trial with a neutral posture wrist. The VT readings with a deviated wrist were aomplished by rotating the vibrating post on a side suh that the vibrating post was oriented to the finger. The trial ended upon ompletion of 20 min of the ativity or until disomfort was felt in the wrist or hand, at whih time readings were taken. The time, type, and loation of disomfort were reorded.

5 WRIST DEVIATION TESTS FOR CTS 319 The study was approved by the Texas A&M University Institutional Review Board Human Subjets in Researh, and informed onsent was obtained from eah partiipant. 3. RESULTS 3.1. Symptom Onset Partiipants 1,2,3, and 4 experiened CTS symptoms of pain, disomfort, or parenthesia in 49, 46, 42, and 67 times, respetively, of the 84 trials. This indiates that using symptoms, as in Phalen s (1951) test, may not be benefiial for CTS disrimination, espeially sine the CTSmild partiipant had the fewest number of symptom reports. Furthermore, in only four trials, the CTS partiipants experiened the symptoms prior to any of the healthy partiipants. Table 1 provides the time of onset and symptoms reported by eah partiipant in these trials. Further testing with the positions in these trials may improve CTS disriminability. For eah partiipant, the extended flexion wrist position had the highest frequeny of pain ourrenes, whereas the neutral wrist position had the lowest frequeny. As ould be expeted, the no hand, stati unlenhed power grip, and stati unlenhed pinh grip hand ativities had the fewest ourrenes of symptom onset. Phalen s (1951) position, wrist flexion with no hand ativity, was not signifiant. In this position, numbness was provoked in Partiipant 4 at 15: min, whereas the other partiipants experiened no symptoms. Regardless of wrist position, all partiipants experiened pain in eah of the 32 loaded power and pinh grip ombinations exept Partiipant 3 who experiened no symptoms during the loaded flexion and extension of a pinh grip in dynami wrist flexion and extension. The hand ativities with flexion and extension experiened pain an average of 2:03 (min:s) into the trial. With further testing, the average time of about 2 min using these hand ativities with flexion and extension may prove a better CTS disriminator than 1 min of flexion Distal Motor Lateny The mean DML determinations by trial interval for eah partiipant are provided in Table 2. If a test ended between time intervals, the value was reorded on the higher time of the interval. The one-way ANOVA for eah partiipant s DML values by time indiated a signifiant differene in Partiipants 3 and 4. Least signifiant differene (LSD; a =.05) omparison of treatment means revealed differenes within Partiipants 3 and 4. TABLE 1. Positions With Symptoms Disriminating CTS Levels in Partiipants Time of Onset and Symptom by Partiipant CTS Level Position 1 None 2 None 3 Mild 4 Moderate No hand ativity in an extended extension wrist position Unloaded flexion and extension of a pinh grip in a stati neutral w rist position Loaded flexion and extension of a power grip in a stati extended w rist position Unloaded flexion and extension of a power grip in a dynami extended wrist position atime in minis. None None 4:40a W rist pain None None 6:28 Palm pain 2:33 W rist pain 3:58 Finger pain 0:41 W rist pain None None 3:32 Thum b pain 10: W rist numb 15: W rist pain 1: W rist pain 15:41 W rist pain

6 320 K.M. WHITE, J.J. CONGLETON, O.J. PENDLETON, R.D. HUCHINGSON, AND R.J. KOPPA TABLE 2. Mean DML by Trial Interval and ANOVA Analysis by Partiipant Mean Distal Motor Lateny ANOVA Partiipant CTS Level Start 1 min 5 min 10 min 15 min 20 min F (df\ Prob > F 1 None 3.20a n = 67 n = 61 n = 38 n = 35 (5,311) A b A A A A A 2 None n = 69 n = 57 (5,310) A A A A A A 3 Mild n = 84 n = 66 n 60 n = 34 n = 31 n = 43 (5,312) ; A A B CO : C CN CO CO : C CO 4 Moderate n = 84 n = 63 n = 62 n = 10 (5,295) A A B CO : adml in milliseonds. bw ithin partiipants, means w ith the same letter are not signifiantly different (a =.05). Terraed letters provided to visualize the mean group trends. B D Beause of pain, not all partiipants were able to omplete eah trial. To ompensate for pain, eah partiipant s mean starting values were ompared to their mean ending values (Table 3). A t test revealed a signifiant differene within Partiipant 4. The differene between the CTS DML hange and healthy DML hange was used to quantify the provoative effet and determine the hand ativity and wrist deviation ombinations that disriminate CTS from healthy wrists. For eah trial, this differene onsisted of subtrating the maximum DML hange in healthy partiipants from the minimum DML hange in the CTS partiipants. Change for eah partiipant was derived by subtrating the value farthest from the start value from the starting value. This method ignores the differene of start values between partiipants and assumes the testing would provoke a measurable hange in the DML value. Ideally, the CTS partiipants would display a large hange, whereas the healthy partiipants would display little hange. A suessful trial is defined as a trial in whih the values are within 0.20 ms of eah other (Neurotron Medial, 1986). This tolerane is ompatible with 1 SD for Partiipants 1,2,3, and 4 (0.19,0.16,0.22, and 0.18 ms, respetively). The 0.20 ms tolerane was doubled to define a pratial signifiant differene in the hange. TABLE 3. Mean Starting DML and Ending DML With f Test Comparison M DML f Test Partiipant CTS Level Start n = 84 End n = 84 t (166) Prob > Ifl 1 None 3.20a None Mild Moderate adml in milliseonds.

7 WRIST DEVIATION TESTS FOR CTS 321 TABLE 4. Partiipant CTS Level Trials Produing the Highest DML by Partiipant DML Start High Duration Hand Ativity and Wrist Position Combination 1 None 3.50a min Extension w ith an unloaded power grip 2 None min Neutral w rist with a loaded power grip min Radial deviation w ith a lenhed power grip 3 Mild min Extended extension with a lenhed pinh grip 4 Moderate min Radial deviation w ith a loaded power grip adml in milliseonds. That is, the hange between partiipants must be greater than 0.40 ms for a pratial differene in values. The DML testing revealed one hand ativity and wrist deviation ombination that may assist CTS diagnosis. The unlenhed power grip in stati wrist extension had a differene in DML of 0.,0.03, -0.03, -0.74, and ms at 1,5,10,15, and 20 min, respetively. Eighty-three of the 84 ombinations were less than 0.40 ms and thus not onsidered signifiant. This supports researh indiating DML is not a disriminator for CTS (Dunnan & Waylonis, 1991) within 20 min of a provoative ativity and ontradits researh indiating DML is a disriminator for CTS (Marin et al., 1983; Shwartz et al., 1980). This is not to say that elevated DML did not our within partiipants. Table 4 provides the trials produing the highest individual DML. However, these positions need further testing with a larger sample size before a reommendation for linial use an be made Vibration Threshold Mean VT determinations by test interval are provided in Table 5. A one-way ANOVA for eah partiipant s DML values by time indiated a signifiant differene in Partiipants 3 and 4. The LSD (a =.05) omparison of treatment means revealed differenes within Partiipants 3 and 4. Comparing the starting thresholds to the ending thresholds also reveals a signifiant differene within Partiipants 3 and 4 (Table 6). The VT was evaluated in a similar fashion as the DML. Table 7 depits the differene in VT hanges. As VT had the most signifiane, all trials are provided for omparison. The 14 values in bold are the trials onsidered pratially signifiant. Pratial signifiane is defined as a positive differene of at least 0.40 vibration units. This differene is roughly equivalent to doubling 1 SD of the mean starting values. These standard deviations for Partiipants 1,2,3, and 4 were 0.21,0.20,0.22, and 0.32 vibration units, respetively. Breaking out the 14 pratially signifiant ombinations by hand ativity indiates the pinh grip was prominent in 5 trials, the power grip in 8 trials, and no hand ativity in 1 trial. The loaded power grip positions displayed sharp initial inreases but terminated at 5 min or less due to pain. By wrist position, the extension and extended extension was prominent in 10 trials, extended flexion in 2 trials, neutral wrist in 1 trial, and radial deviation in 1 trial. The largest trial differenes 0.70,0.75, and 0.75 vibration units ourred at 10,10, and 15 min, respetively, and resulted from a form of a wrist extension. Three trials, unlenhed pinh grip in extension, lenhed power grip in radial deviation, and unlenhed pinh grip in extension, had peak threshold differenes at 10 min. These positions demonstrated a onsistent inrease in threshold differene between 5 and 10 min and a derease from 10 to 15 min. For these positions, 10 min is a better CTS disriminator than 5 or 10 min. The 10-min time limit may prove to be a better time limit than the previously used 5 min or less limit (Dunnan & Waylonis, 1991; Koris et al., 1990; Marin et al., 1983; Shwartz et al., 1980).

8 322 K.M. WHITE, J.J. CONGLETON, O.J. PENDLETON, R.D. HUCHINGSON, AND R.J. KOPPA TABLE 5. Partiipant CTS Level Mean MVT by Trial Interval and ANOVA Analysis by Partiipant M Vibration Threshold ANOVA Start 1 min 5 min 10 min 15 min 20 min F (df) Prob > F 1 None 1.13a n = 71 n = 46 n = 39 n = 35 (5,353) A b A A A A A 2 None n = 84 n = 67 n = 42 n = 38 (5,353) «* A A A A A A 3 Mild n = 72 n = 46 (5,366) A B B CO C 4 Moderate n = 78 n = 56 n = 10 (5,343) D D 1"- CO : CO A B C C th re s h o ld s in vibration units. bw ithin partiipants, means with the same letter are not signifiantly different (a =.05). Terraed letters provided to visualize the mean group trends Correlation Between DML and VT Pearson produt-moment orrelation was used to ompare the DML values to the VT values. Table 8 indiates no orrelation between DML starting values and VT starting values. Similarly, there is no orrelation between DML ending values and VT ending values. That is, a high (low) starting or ending DML does not orrespond with a high (low) starting or ending VT, respetively Dereasing DML Trends and Inreasing VT Trends The slopes of eah partiipant s trials were established and lassified as an inreasing or dereasing trend. An inreasing trend means the values degraded, whereas a negative trend indiates improvement. Table 9 provides the trend ourrenes grouped by the four possible trend states. In general, the most ommon ourrene is a dereasing DML with an inreasing TABLE 6. Mean Starting MVT and Ending MVT With t Test Comparison M MVT t Test Partiipant CTS Level Start n = 84 End n = 84 f (166) Prob > Ifl 1 None 1.13a None Mild Moderate th re s h o ld s in vibration units.

9 T3 C qj * K a>! rr x LU s *o! </> a> <d +- +-< X X ^ o o o o T - LO T - CD od d o -o -a -a tj o -»*» <d <d <d <d if) r-_ l ) LO to o o o o O O LO O 0)0 0(1) O 1- - y - : O O O O O o o o o o Z Z Z O O, * L O t T3 T3 T3 o o o C/) CO CO CO o l o o l o o l o o o o l o i o o o o o r-ro\^r^ln<--\roqo^^^ d d d o o o d d d d d o o o o z z z z o " p <75 o CL > JD LO LD LO LO LD O LO Lf) Lf) T - C N C O C N j C N t C > t - (1) I I I a "a ~o *a p o o o o ' CO to CO IO LO o o o o o z z to o o l o o l o l o o o o ^ t r ^ ^ t r * ; 0 '^tcn'ro d o d d d d d o o o ' t o n o d d t ō TABLE 7. Minimum Vibrotatile Threshold Differenes for Eah Trial o -Q > E 3 E LO Lf) O O O r - CO CO CN CN O O O CD CD I I I O loo o o f r - T t lo r r «' * CO CO (O CO O LO O O CD O O O O O o o o o L O O L O L O O O L O O L O L O O L O O O N^-»-^NjqqooooDr-q d d d o d d d d d d d d o o i i l l o o z z T3 OOOO "DT3 T3 o LO o O CN to -t-< 4-> (J) Vi 4-1 Vi 4-t Vi O LO o o LO o o LO o LO CN CN r CN * * O d d d d o O CD d d d O O O O z z z z O T3 CO o i f CD Q) 73 o Z D O) -n * o.e a o. a "a o * o.e Q. Q. LU LU T3 -D O O a -a t o S Itss O -C O -C o.e g * o.e Q. Q. CL Q. LU LU ~o ~a o o a D D D o o sz. D~0 a -o a T3 C C o o o o CO CD <D (D tj -a o o CD CD o o 5 5 CJ CJ CO CO o o Q Q O C E o (D o E F.E A o o CD o _Q O > o o (O o o E J5 Q CD /Vofe. SW = Stati Wrist; F/E = Flexion and Extension; DW - Dynami Wrist, 323

10 324 K.M. WHITE, J.J. CONGLETON, O.J. PENDLETON, R.D. HUCHINGSON, AND R.J. KOPPA TABLE 8. Correlation Between DML and MVT Correlation Start Partiipant CTS Level n = 84 End Tf 1 None,34a.10 rt 166) = 3.27 f(166) = 0.91 p <.5 p >.1 2 None tf 166) = ) = 1.66 p <.025 p <.05 3 Mild fl166) = 2.64 rt166) = 2.44 p <.5 p <.01 4 Moderate «166) = 0.82 f< 166) = 1.75 p >.1 p <.05 C orrelation oeffiient (rho). VT, whereas the least ommon ourrene is an inreasing DML with a dereasing VT. Notably, Partiipant 4 had 70 ourrenes of a dereasing DML with an inreasing VT. This simple trend onsideration is evidene that the DML and VT funtions may operate independently under initial stages of elevated arpal anal pressure. For additional perspetive on trend behavior, trends were grouped by CTS ondition and plotted appropriately above or below individual starting averages (Figure 1). The tables on the graphs aount for the number of ourrenes of the trend (N), perent of ourrene grouped above or below the partiipant s mean (Area), and perent of ourrene of the total CTS ondition (Total). The TOTAL DML (THRESHOLD) REPRESENTATION provides a perspetive on how well the graphs represent the trend ourrene based on the total CTS ondition. For eah CTS ondition, the Opposite olumn aounts for the perent of trend ourrene that did not behave as the graph indiates, the As Represented olumn is the sum of the Total and is the perent of ourrene represented by the graph, and the No Change olumn is the perent of ourrene that had no hange from the start value. For eah CTS level, the DML effet is generally dereasing regardless of the starting threshold. The CTS partiipants displayed a onsistent inreasing trend in VT regardless of starting value. The healthy partiipants displayed an asymptoti affet to their individual means. That is, if their start VT was above their mean starting VT, then the threshold dereased TABLE 9. Trend Ourrene by Partiipants Trend Ourrene Partiipant CTS Level None None Mild Moderate Note. Dereasing DML trend and dereasing MVT trend. + - Inreasing DML trend and dereasing MVT trend. I- Dereasing DML trend and inreasing MVT trend. + + Inreasing DML trend and inreasing MVT trend.

11 WRIST DEVIATION TESTS FOR CTS 325 Distal Motor Lateny % of N Area Total % 3 4 % % 3 6 % Mean % 3 4 % % 2 6 % Vibration Threshhold M e a n % of N Area Total 61 71% 36% % 3 2 % % 4 7 % % 2 6 % TOTAL DML REPRESENTATION TOTAL THRESHOLD REPRESENTATION C T S ODDOsite A s Renresented N o C h a n e e C T S Dnnnsite A s Represented N o C h a n g e 2 3 % 6 9 % 8 % " ^ * Y e s 1 2 % 8 3 % 5 % " " N o 2 6 % 6 2 % 1 2 % ^ " N o 3 0 % 5 8 % 1 2 % Figure 1. Trend behavior of DML and MVT. and osillated within a standard deviation of their mean. If their start VT was below their mean, then the threshold inreased and osillated within a standard deviation of their mean. No symptoms ourred 35, 38, 42, and 17 times in Partiipants 1, 2, 3, and 4, respetively. Again the partiipant with mild CTS sometimes behaved as a healthy wrist but at a lower frequeny than the healthy wrists. Partiipant 4, with moderate CTS, experiened the lowest rate. However, 16 of her 17 ourrenes began less than and terminated within a standard deviation of her mean. For these 16 instanes, the test duration averaged 7.7 min. Her thresholds ould have ontinued to inrease, but the onset of pain prevented further testing. 4. DISCUSSION Carpal tunnel syndrome results from ompression of the median nerve within the arpal anal. Two basi omponents of this ompression are magnitude and duration of pressure on the nerve (Lundborg & Dahlin, 1986). The umulative effet of the pressure magnitude and duration should also be basi aspets of provoative testing. The magnitude of pressure an be roughly maintained with appropriate wrist position and hand ativity. For ontrol, the test duration should be onsistent between groups to provide equal omparison time. Provoative CTS testing indues a reation of the median nerve to yield more information for a better diagnosis of the patient s true ondition. Ideally, CTS wrists display a reation quiker than healthy wrists. The fundamental theory of provoative testing is depited in Figure 2 and an be applied to symptom onset measures of pain or disomfort as well as measure of DML and VT. Initially, CTS values inrease sharply and level off at a high value, whereas healthy values take time to inrease. Eventually, the healthy wrists would approah the CTS values as the tested funtion degrades. The provoative test should onlude in the region of maximum degradation of CTS values before substantial degradation of healthy values..., Provoative testing theory is exemplified in Figure 3, whih represents eah partiipant s VT for the lenhed pinh grip in extended extension trials. This test distinguished CTS onditions even though the healthy partiipants started above their respetive means. The CTS partiipants inreased, whereas the healthy partiipants remained relatively the same with the provoative ativity.

12 326 K.M. WHITE, J.J. CONGLETON, O.J. PENDLETON, R.D. HUCHINGSON, AND R.J. KOPPA Figure 2. Model of provoative wrist flexion testing Symptom Onset The question of pain, disomfort, parenthesia, or any other reprodued or exaggerated CTS symptom is not onlusive. The healthy partiipants had a higher ourrene of CTS symptoms than Partiipant 3 who had a mild level of CTS. As 3 of the favorable ombinations that disriminate the CTS ondition involve an ativity of the seond and third digits, the modified Phalen s test with the patient forefully pinhing the thumb against the index and middle fingers may prove more sensitive when Phalen s test alone is negative (Smith et al., 1977) Distal Motor Lateny This researh indiates provoative DML testing is not benefiial for CTS disrimination. The DML trends were expeted to be positive. That is, the DML values were expeted to inrease signifiantly, indiating a degradation in motor ondution, whereas the healthy values were expeted to inrease slightly (Dunnan & Waylonis, 1991; Gelberman, Szabo, Williamson, & Dimik, 1983; Marin et al., 1983; Shwartz et al., 1980). Reviewing all 84 trials, 38 had a negative final hange, 27 had a positive hange, and 19 had no hange. In general, the trends were negative. Moreover, nerve ondution improved in the CTS partiipants greater than any hange in healthy partiipants. The negative trend indiates nerve ondution improvement not degradation disriminated mild and moderate CTS patients from healthy patients in the Test Time in Minutes 1-None O - ~ 3-Mild 2-None Moderate Figure 3. Clenhed pinh grip in extended extension.

13 WRIST DEVIATION TESTS FOR CTS 327 positions tested. This must be qualified beause it is ontrary to the expeted outome. It is also possible the hand and wrist ativity warmed the nerve tissues suffiiently to promote faster motor nerve ondution (Kimura, 1983). This implies motor ondution may be improved in affeted hands with exerise for a speified time. However, with time, the motor ondution may degrade as anal pressures overome any benefits from tissue warming. Patients with severe CTS or abnormal resting DML determinations were not studied in this researh. Severe CTS patients may display slower ondution times before mild and moderate ases whih ould disriminate levels of the syndrome in CTS patients Vibration Threshold The mean VT aross time indiates an inreasing trend in threshold degradation with a provoative ativity. The healthy partiipants displayed a mean inrease, the mild CTS partiipant displayed a sharper inrease, whereas the moderate CTS partiipant displayed the greatest inrease. This is expeted beause sensory ondution tends to be anomalous before motor ondution (Lieberman & Taylor, 1986; Marin et al., 1983). The different slopes of the inrease by ondition may assist sreening people with varying CTS onditions. Furthermore, Werner, Franyblau, and Johnston (1994), presumably using a neutral wrist posture in a ross-setional study of 130 fatory workers, did not support the use of vibrometry as a sreening tool for median nerve impairment. This finding an be understood, with reservation, beause daily VT differenes, while reliable (Roserane, Cook, Satre, Goode, & Shroder, 1994), an indiate false determinations within people who have varying degrees of CTS (Espritt, Carter, Congleton, Crumpton, & White, 1996; White, Congleton, Huhingson, Koppa, & Pendleton, 1994). It is possible that vibrometry ombined with a provoative hand ativity and wrist position may evoke a person s true CTS ondition. The VT differenes (Table 6) indiate that wrist extension provides the most onsistent ontribution to provoative CTS testing. Of the 14 pratially signifiant ombinations, 7 involved wrist extension, and 3 involved extended extension. Wrist extension is known to produe higher anal pressures than flexion (Gelberman et al., 1981; Rojviroj et al., 1990; Werner et al., 1983) and exerts this pressure on different areas of the median nerve more than wrist flexion (Armstrong 1983; Shwartz et al., 1980; Skie, Zeiss, Ebraheim, & Jakson, 1990; Smith et al., 1977). As a result, wrist extension and extended extension provide promising results for further onsideration Progressive Loading of the Carpal Canal Carpal anal pressures inrease with loading (Werner et al., 1983). This effet is evident by progressively loading the power grip hand ativity of the extension wrist position (Figure 4). The no-hand ativity in extension demonstrates an initial jump in CTS partiipants from start to 1 min before smoothly inreasing. The healthy VT initially dereased from start to 1 min then remained relatively the same for 15 min. Between 15 and 20 min, Partiipant 1 degraded and began to approah CTS values. The unlenhed power grip in extension demonstrated an initial inrease in CTS partiipants. Partiipant 3 did not signifiantly degrade until 10 min. The healthy partiipants remained relatively the same through the test duration. Similarly, the lenhed power grip in extension demonstrated an initial inrease in CTS partiipants. This inrease (1.05 vibration units) was sharpest in Partiipant 3 who began the test with her seond lowest starting value (0.50 vibration units). This is important beause she ould have been misdiagnosed as no CTS if a liniian only onsidered her starting (neutral wrist) VT. The testing provided substantial information for proper CTS sreening, however, she did not signifiantly degrade until 15 min. The healthy partiipants remained relatively the same through the test duration. The loaded power grip in extension provided both a sharp VT inrease in CTS partiipants and the most pain of these four trials. This position may have elevated the anal pressures

14 328 K.M. WHITE, J.J. CONGLETON, O.J. PENDLETON, R.D. HUCHINGSON, AND R.J. KOPPA No Hand Ativity in Extension a D t r Unlenhed Power GriD in Extension «5 <u L. i Clenhed Power GriD in Extension a L. Loaded Power Grip in Extension I 5 10 Test Tim e in M inutes O ' 1 -None - O *** 2-None 3-M ild 4-Moderat Figure 4. Results of progressively inreasing arpal anal pressure. suffiiently in CTS partiipants for sharp VT degradation but not enough in healthy wrist for an immediate effet. Contrary to Phalen s test, pain was exhibited in the healthy partiipants before the CTS partiipants. Provoative wrist deviation tests must balane loading and pain onsiderations to permit suffiient time for signifiant degradation in CTS patients. Eah of these trials demonstrated an initial inrease in CTS patients with relatively little effet on the healthy partiipants. With time, the CTS degradation inreased whih provided a learer piture of the partiipant s ondition. However, too muh time, as indiated by the right portion of Figure 2, permits the healthy wrists to degrade and approah the CTS VT. In time, the benefit of the provoative test diminishes. The values in Table 7 represent the peak VT differenes between CTS and healthy partiipants for the trial. A plot of the differenes by time interval (Figure 5) provides further insight to the progressive anal loading with the power grip. The no hand ativity in extension displays a slightly inreasing slope ((3 =.3, R2 =.044). A greater slope and better CTS disrimination is provided in the unlenhed and lenhed power grip positions. Ideally, the unlenhed power grip position should have had a smaller

15 WRIST DEVIATION TESTS FOR CTS " TJ CJ SJ J3 a QJ U 0> u te pfi «-» H Q o o O <> < T Q Test Time in Minutes No Hand Ativity in Extension Unlenhed Power Grip in Extension Clenhed Power Grip in Extension Loaded Power Grip in Extension O 15 y = 0.3X y = 0.035X y = 0.028X y = 0.050X r 2= R 2 = R2= R 2 = 1.0 Figure 5. Progressive anal loading evident in slopes of threshold differenes. slope ((3 =.035, R2 =.787) than the lenhed power grip position (3 =.028, R2 =.639). Between 10 and 15 min of the lenhed power grip position, Partiipant Is VT degraded suffiiently to offset inreases in the CTS partiipants. This dereased the threshold differene and subsequently dereased the slope of the linear fit. Without the offsetting value, the lenhed power grip inrease ( 3 =.056, R2 =.997) would have been steeper than the unlenhed power grip. The steepest inrease (p =.050, R2 = 1.0) ourred with the loaded power grip. The atual test duration was only 2 min as pain ended possible benefits of further testing. The position disriminated CTS, onditions but the onset of pain ended possible greater disriminability of the test. The inreased anal pressure generated by progressively tensing the power grip resulted in a progressively inreasing slope of the threshold differenes. Simply, the greater the pressure, the sooner the trial disriminated CTS onditions. With time and without pain, inreased pressures allowed the healthy VT to approah the CTS VT. However, with pain, a prominent fator of high loading, the test duration was short thereby diminishing further test benefits Chek Mark Effet During the testing proess, the healthy partiipants had a slight improvement in VT before degrading, whereas the CTS partiipants thresholds generally degraded. Of the 84 trials, Partiipants 1,2,3, and 4 displayed improved values from the start value 53,52,31, and 14 times, respetively. Interestingly, the number of improved values dereased as the CTS level inreased. The slight improvement effet before degrading resembles a hek mark (Figure 6) and may explain some behavior of the median nerve under periods of pressure. This effet is also evident in healthy partiipants (Borg & Linblom, 1986). Figure 6 does not imply all wrists exhibit an equal amount of hange, a fixed rate of hange, or a linear relationship between points of interest. Although the lines onvey a narrow threshold value, the atual individual bands of operation may be large. This hek mark model simply proposes that the sensory nerve ondution behaves in a similar fashion as it aounts for varying duration of anal pressure. The motor ondution may behave in a similar fashion, however, the general trend was dereasing. In Figure 6, Segment I represents the ideal resting value of a neutral posture wrist without an event affeting (or having had affeted) the nerve. This value may be diffiult to obtain as personal fators or oupational fators may influene the arpal anal pressure and thus

16 330 K.M. WHITE, J.J. CONGLETON, O.J. PENDLETON, R.D. HUCHINGSON, AND R.J. KOPPA Figure 6. Model of the hek mark effet. hange the VT. As with blood pressure measures (O Brien & O Malley, 1981), several values over time would be needed to obtain an individual s resting value for a true understanding of an individual s homeostasis. Segment is the improvement exhibited in the initial stages of an ativity of a healthy partiipant s VT. Table 10 indiates Partiipant 1 generally improved at 1 min, whereas Partiipant 2 improved at 10 min. This observation is evidened in another study where VT dereased slightly from the rest value (Borg & Linblom, 1986). Segment has appliation in sensory funtion rehabilitation, however, the improvement time differs for eah person. In a rehabilitation setting, this time is ritial beause the nerve funtion may quikly degrade. Segment I is the portion of initial degradation or inrease in VT. It overs the same threshold values as Segment but displays an inreasing trend. Besides opposite slopes, time duration between these segments may also differ. For a given ativity, the slope of Segment may differ from the slope of Segment I. Segment IV indiates degradation beyond the resting value and is the major onern of this study. In CTS patients, the slope of this segment may be steeper and our sooner than in healthy patients. Segment V represents the theoretial point of absolute degradation. In essene, the nerve no longer serves a vibration-sensing funtion. The pratial limit of the VT may be reahed when parenthesia dominates the tatile sensations. Segment VI depits reovery time or the return of values to the theoretial resting value. Pratially, this would be the return of values to homeostasis and is probably between 1 and 10 min (Borg & Linblom, 1986; Gelberman, Szabo, Williamson, Hargens, et al., 1983; Gellman TABLE 10. Average Time of MVT Improvement in Healthy Partiipants Partiipant M Low Change From Time of Slope After CTS Level Value Start Ourrene Low Value 1 None 1.12* min None min 0.01 th re s h o ld s in vibration units. Note. Pearson produt-moment orrelation was used to ompare the DML values to the MVT values. Table 8 indiates no orrelation between DML starting values and MVT starting values. Similarly, there is no orrelation between DML ending values and MVT ending values.

17 WRIST DEVIATION TESTS FOR CTS 331 et al., 1986; Lundborg, 1975; Marin et al., 1983; Rydevik, Lundborg, & Bagge, 1981). Reovery an begin anytime the wrist pressure is removed or redued. If another provoative ation ours during reovery, the nerve will probably behave as if it were in Segment IV. Individual anal pressures may flutuate dramatially daily. Any fator, personal or oupational, may effet the anal pressure. The magnitude and duration of these pressures hanges the threshold along the hek mark model. In theory, Partiipants 1 and 2 generally operate on Segments I and, Partiipant 3 seems to operate on Segments and I, whereas Partiipant 4 operates along Segments I and IV. The hange in anal pressure auses a minimal hange within the healthy wrists. In mild CTS, a degradation ours sooner but some improvement may still be evidened. Moderate CTS levels reat quikly to inreased pressure as the degradation is almost immediate. Provoative testing assists distinguishing between CTS patients when their values seem normal as in Segment I. 5. FUTURE RESEARCH A goal of this researh was to systematially test various hand ativity and wrist position ombinations in order to selet two of the most promising ombinations for further testing with a larger sample size. With ontrol group and design balaning onsiderations, a total of six ombinations will be seleted for further testing. /-^r Criteria to selet the most promising ombinations inlude test duration and CTS ondition disriminability. Personal ommuniations with several orthopedi speialists indiate that they would spend no more than 10 min on a provoative test. With the desire to provide methods for immediate use in a linial setting, 10 min is the maximum test duration. This eliminates the unlenhed power grip in extension from onsideration (0.75 vibration units at 15 min). Additionally, five of the six pratially signifiant trials with a test duration of at least 10 min demonstrate peak values at 10 min. The orthopedi speialists also stated that they preferred performing the wrist provoation without any other devies suh as a hand dynamometer or pinh gauge. This preferene eliminates the loaded power and pinh grip onditions from further onsideration. The most promising hand ativity and wrist position ombinations for future testing are the lenhed power grip in extension and the lenhed pinh grip in extended extension. Referring to Table 7 for CTS ondition disriminability, these trials display the greatest CTS threshold differenes within 10 min (0.75 and 0.70 vibration units, respetively). The no-hand ativity in extension and no hand ativity in flexion serve as ontrol groups. These positions are used in other wrist deviation researh (Borg & Linblom, 1986; Dunnan & Waylonis, 1991; Marin et al., 1983; Shwartz et al., 1980) and as suh will link the researh Two other tests, a form of extension and a form of flexion, will be used to balane the experimental design. As extension and extended extension wrist positions aount for 10 of the 14 pratially signifiant trials, four forms of extension and two forms of flexion will serve as a representative sample. Beause two extension positions were seleted, an extended extension position was desired. Similarly, 2 of the 14 are with a flexion and extension hand ativity therefore one flexion and extension ativity will also be tested. The stati wrist with unloaded flexion and extension of the pinh grip will be tested as it provides the greatest disriminability within the flexion and extension ativity of the extended extension position. Finally, the hoie for a form of flexion was between the unlenhed power grip in extended flexion and the lenhed pinh grip in extended flexion. Although the unlenhed power grip in extended flexion provides greater CTS ondition disriminability, the lenhed pinh grip in extended flexion is seleted beause results an be ompared with the linhed pinh grip in extended extension.. The satter plots of the hand ativity and wrist position ombinations seleted for future researh are depited in Figure 7.

18 332 K.M. WHITE, J.J. CONGLETON, O.J. PENDLETON, R.D. HUCHINGSON, AND R.J. KOPPA I No Hand Ativity in Extension 0 5 No Hand Ativity in Flexion Vibration Threshold in Vibration Units Clenhed Power Grip in Extension Clenhed Pinh Grip in Extended Extension i i i Clenhed Pinh Grip in Extended Flexion Test Time in Minutes 1-None Mild SW=Stati Wrist 2-None Moderate F/E=Flexion&Extension Figure 7. Satterplots of hand ativities and wrist positions seleted for future researh.