Category: Monofilament Test

Diabetes and Footcare

Posted on Category:Monofilament Test

Diabetes and Footcare

Diabetes can cause and nerve damage. Lost sensitivity in the feet can make it difficult to know when you’re hurt or injured and even the smalleset cuts and scrapes can become difficult to heal. To help revent foot complications that can come with diabetes, it’s important to have the right information to make smart choices and connect with expert diabetes advice

 

https://diabetes.org/living-with-diabetes/preventing#caring-for-your-feet

Living with Diabetes

Posted on Category:Monofilament Test

Diabetes & Your Feet

The connection between diabetes and your feet is important because diabetes can cause nerve damage and reduced circulation, ultimately leading to limb loss and other complications. The good news is, you can lower your chances of complications by managing your blood glucose levels and taking care of your feet.

 

https://diabetes.org/living-with-diabetes/

Monofilament testing in diabetic foot

Posted on Category:Monofilament Test

Monofilament testing in diabetic foot

Last edited 06/2020 and last reviewed 11/2021

The 10 g monofilament

  • 10g monofilament was originally invented for testing for sensory loss in the hands of people with leprosy and was not made from nylon but horse hairs. Monofilaments are easy to use but there are some potential areas for incorrect use or misuse
  • (1)

How to use a 10 g monofilament

Upon initial use or after rest it is best to buckle the monofilament a few times prior to applying to the person’s skin as this will remove any residual stiffness. If this is not done the monofilament will deliver more than 10 g of force.

  • Explain what are you going to do and why. Then apply the monofilament to somewhere else on the person, for example the forearm, so that they can experience the sensation of the monofilament.

The technique for using a monofilament has been detailed (2):

DM%2520monof

Scoring system based on five sites on each foot = 10 sites; if score of 8 or less then indicative of neuropathy (2)

Monofilament technique notes:

  • The monofilament must be placed at 90 degrees to the skin surface.
  • It is applied, held and released in a controlled manner.
  • It should be applied, held and released over 1–2 seconds for each test.
  • When applied and held the monofilament should buckle at about 1 cm from the horizontal.
  • It must not “wiggle” or slide when held in place.

Inability to detect one or more sites in each foot indicates sensory deficit and increased ulcer risk.

Reference:

  • Baker N. Prevention, screening and referral of the diabetic foot in primary care. Diabetes & Primary Care 2011; 13 (4):225-34.
  • The North West London Health and Care Partnership. North West London Diabetes Guidelines (Accessed 30/6/2020).

medwoodworks.com
Semmes Weinstein 10g Sensory Tester


Diabetes Health: Monofilament Test for Neuropathy

Posted on Category:Monofilament Test

Diabetes Health: Monofilament Test for Neuropathy

612490f1fbc9791ad94d4aa4 diabeticfootexam min

If you have diabetes, you are at risk of developing nerve damage. One type of nerve damage you are at risk for is called diabetic peripheral neuropathy (DPN). DPN is a condition that impacts your toes, feet, fingers, and hands. You may feel tingling, burning, pain, or lose all sensation in those parts of the body. When you have nerve damage in these parts of the body, you may be unable to feel an injury. This is a problem because a small nick or cut can easily become infected if it goes unnoticed. Infection can then lead to worse problems like foot ulcers and amputations.

The important thing when it comes to DPN is knowing you have it, preventing it from spreading and taking steps to protect yourself. One of the ways that DPN is diagnosed is with a monofilament test.

What is a monofilament test?

A monofilament test, formally called a Semmes-Weinstein monofilament ( SWM) test, is done by a doctor, nurse or CDE to test for nerve damage. It is a small strand of nylon attached to a plastic base. Your doctor will have you sit or lay down and most likely have you close your eyes. Then, your doctor will place the monofilament on specific areas of your foot and apply pressure.

If you cannot feel this action performed by your doctor it is an indication of nerve damage in that part of your foot. It is one of many tests used by health professionals to diagnoses DPN.

61249101e4d32c3539e81ff0 Picture5555

Image: Source

What do I do if I’m diagnosed with Neuropathy?

Your doctor will work with you to develop a treatment plan to help you work to prevent complications and nerve damage from spreading. Some of the things you can do to prevent injury and protect your feet include:

  • Daily Foot Exams
  • Wearing socks every day
  • Never walking barefoot
  • Wear proper fitting shoes
  • See a podiatrist (foot doctor) once a year or more depending on your risk factors
  • Clean your feet daily
  • Change your socks daily

Semmes Weinstein 10g Sensory Tester

www.medwoodworks.com

Semmes-Weinstein Monofilament Testing

Posted on Category:Monofilament Test

What is the role of Semmes-Weinstein monofilament testing in the diagnosis of electrophysiologically graded carpal tunnel syndrome?

Abstract

[Purpose] The aim of the study was to investigate the ability of Semmes-Weinstein Monofilament testing to detect carpal tunnel syndrome, as well as moderate-to-severe carpal tunnel syndrome using varying thresholds and methods. [Subjects] Clinical and electrophysiological data of 62 patients (124 hands) with a mean age of 49.09±10.5 years were evaluated in this study. [Methods] Sensitivity and specificity were calculated according to two threshold values (2.83 and 3.22) and two methods, a conventional method and an internal comparison method. A threshold value of 3.22 was also used to determine sensitivity and specificity in the diagnosis of electrophysiologically moderate-to-severe carpal tunnel syndrome. Data of the first three digits were averaged to reveal the mean strength value of the monofilaments for each hand. [Results] The criteria of 2.83-conventional method yielded a sensitivity of 98% and a specificity of 17% in the diagnosis of carpal tunnel syndrome. The threshold value of 3.22 using a conventional method was found to detect moderate-to-severe carpal tunnel syndrome with high sensitivity (80%) and excellent specificity (93%). A statistically significant difference was observed in the mean strength values of the monofilaments in moderate-to-severe carpal tunnel syndrome hands and hands without carpal tunnel syndrome. [Conclusion] The current study demonstrated that Semmes-Weinstein monofilament testing might be a valuable quantitative method for detecting moderate-to-severe carpal tunnel syndrome.

Key words: Semmes-Weinstein monofilaments, Sensitivity and specificity, Carpal tunnel syndrome

INTRODUCTION

Carpal tunnel syndrome (CTS) is a common and well-known entrapment neuropathy. A variety of physical exams involving clinical examinations and tests have addressed one or more characteristics of the syndrome, such as sensory or motor loss). The Semmes-Weinstein monofilament (SWM) testing is one of the clinical tests that measures the response to a touching sensation of the monofilaments using a numerical quantity. This testing was developed for the detection of patients at risk of neuropathic ulceration, and it is a clinical tool used in the evaluation of peripheral nerve injuries and compression syndromes before and/or after recovery).

Previous studies comparing clinical standards in diagnosing CTS provided inconsistent results, and there is no consensus on the sensitivity and specificity of the SWM testing,,,,). It is generally accepted that CTS is diagnosed by clinical and electrodiagnostic examinations; however, there is still controversy about how valuable some of the clinical examination tools are, such as sensory testing). Gellman et al. suggested that SWM testing would be a beneficial part of the sensory examination to diagnose CTS patients with high sensitivity and specificity). On the other hand, Pagel et al. reported that SWM testing was useless as a screening tool in patients with CTS-compatible symptoms).

A systematic review reported that additional studies detailing test methodologies are required to define the role of SWM testing in the clinical assessment of CTS). However, to our knowledge, studies describing the methods and threshold abnormalities of SWM testing for the diagnosis of CTS, as compared with electrophysiological severity, are not yet available.

Thus, the aim of this study was to determine the value of SWM testing as a clinical examination tool using two different threshold abnormalities and two different methods, as well as the relationship between threshold abnormality and electrophysiological CTS grade.

SUBJECTS AND METHODS

Clinical data of patients who applied to the outpatient clinic of a university with symptoms suggesting CTS were assessed retrospectively. Two physicians independently performed the clinical and electrophysiological evaluations of the patients. The first physician performed clinical assessments and routine physical examinations, including Tinel’s sign, Phalen’s maneuver, and SWM testing. The patients were then referred to a second physician (unaware of the physical exam results) for electrodiagnostic testing. The exclusion criteria were the presence of a neurologic disease; prior nerve injuries, trauma, or a surgical procedure in the upper extremities; thenar atrophy; pregnancy; or acute/subacute cervical radiculopathy. Patients who had clinical or electrophysiological findings suggesting other pathologies, such as polyneuropathy, ulnar, and/or radial neuropathy, were also excluded. All of the patients were informed about the study, and their written informed consent was obtained. The research protocol was reviewed and approved by the Clinical Research Ethics Committee of the university, and it was carried out in accordance with the principles of the Declaration of Helsinki.

The electrodiagnostic measures were performed in the electrophysiology laboratory at a university hospital. All electrophysiological examinations were conducted at room temperature with a skin temperature of >31 °C. The instrument used was a Medelec Sapphire 4 ME. The filter settings were 3 Hz–5 kHz for the motor nerve conduction study (NCS) and 20 Hz–2 kHz for the sensory NCS. The sweep durations were 50 ms for the motor NCS and 20 ms for the sensory NCS. The sensitivity was 1 mV and 20 µV for the motor and sensory NCSs, respectively. Supramaximal stimulation was used in the motor NCS. Bilaterally median motor and sensory nerve conduction potentials were recorded using standard techniques according to the practice parameters for the electrodiagnosis of CTS outlined by the American Academy of Neurology, the American Association of Neuromuscular and Electrodiagnostic Medicine, and the American Academy of Physical Medicine and Rehabilitation). Bilaterally motor/sensory ulnar and radial nerve conduction studies were also performed for the differential diagnosis. Abnormal electrophysiological findings suggesting CTS were categorized into three grades according to Stevens’ classification: mild, prolonged median sensory distal latency (>3.5 ms); moderate, abnormal median sensory latency (>3.5 ms) and prolonged median motor distal latency (>4.2 ms); and severe, the absence of median sensory nerve action potential or low amplitude of thenar compound muscle action potential (<5 mV)). After removing the data for SWM testing from the clinical data, the patients were considered to have CTS if they had both clinical and electrophysiological findings. The electrophysiological data of these patients for each hand were then grouped into mild CTS and moderate-to-severe CTS groups according to the electrophysiological grades described.

Measurements were obtained through the application of a force-calibrated SWM to each digit except the ring finger, with the wrist in a neutral position. Testing was performed in a silent room using a standard technique: the monofilaments were applied three times to the tip of each finger. The heaviest monofilament that a patient could feel was used; thus, a numeric value was recorded that the logarithm of 10 times the force in milligrams require to bow the monofilament).

Sensitivity and specificity were calculated according to two threshold values (2.83 and 3.22) and two methods, a conventional method (CM) and an internal comparison method (IM). A test was considered positive if the recorded threshold value of any radial digit was higher than 2.83 (2.83-CM), the recorded threshold value of digit 3 was higher than both 2.83 and the threshold value of digit 5 (2.83-IM), the recorded threshold value of any radial digit was higher than 3.22 (3.22-CM), the recorded threshold value of digit 3 was higher than both 3.22 and the threshold value of digit 5 (3.22-IM).

All these criteria were used in the calculations to determine the sensitivities and specificities of non-CTS and CTS hands. The last two criteria (3.22-CM and 3.22-IM) were also investigated to determine sensitivity and specificity using the recorded data of non-CTS and moderate-to-severe CTS hands.

Mean monofilament value of each hand: The threshold value for each digit corresponded to a theoretical monofilament strength in SWM testing. These logarithms were converted into actual pressure applied, and the strength values of the monofilament for the first three digits of the patients were averaged to reveal the mean strength value of each hand. These data were used to compare non-CTS and CTS hands, as well as non-CTS and moderate-to-severe CTS hands. The highest monofilament strength value for the first three digits of the patients was used for the receiver operating characteristic (ROC) curve.

Statistical analyses were performed using the Statistical Package for the Social Sciences (SPSS, Inc., Chicago, IL, USA) version 15.0. The data were analyzed using two by two tables to determine the sensitivity, specificity, positive predictive value, and negative predictive value. The Kolmogorov-Smirnov test was used to test the normality of the data distribution. The Mann-Whitney U test was used for between-group comparisons due to the data not showing a normal distribution. The ROC curve was used to determine the accuracy. Accordingly, the optimal cutoff point was calculated for diagnosis of CTS and for diagnosis of moderate-to-severe CTS. Significance was set at p<0.05.

RESULTS

In total, data of 62 patients (57 females, 5 males) with a mean age of 49±10.5 (20–72) years were evaluated in this study. Figure 1 shows a flowchart of the study population.

An external file that holds a picture, illustration, etc. Object name is jpts-27-3749-g001.jpg

Flowchart of the study population

Of 124 hands in 62 patients, 49 hands (39%) had abnormal clinical and electrophysiological findings related to CTS. According to electrophysiological severity, 19 patients had mild CTS, 18 patients had moderate CTS, and 12 patients had severe CTS.

It was observed that the criteria of 2.83-CM yielded a sensitivity of 98% and a specificity of 17%. When the criterion of 2.83-IM was used, a sensitivity of 39% and a specificity of 83% were achieved. Specificities of 93% (CM) and 97% (IM) were obtained when the threshold value was increased to 3.22. Using the criteria of 3.22-CM and 3.22-IM, the sensitivity results were found to be 49% and 29%, respectively. The numbers of positive and negative tests and the positive and negative predictive values are shown in Tables 1 andand 2Table 2.

Table 1.

Positive and negative tests in total CTS hands
Positive Negative Total

(No.) (No.) (No.)
2.83-CM CTS (+) 48 62 110
CTS (–) 1 13 14
2.83-IM CTS (+) 19 13 32
CTS (–) 30 62 92
3.22-CM CTS (+) 24 5 29
CTS (–) 25 70 95
3.22-IM CTS (+) 14 2 16
CTS (–) 35 73 108
Total 49 75 124

CTS: carpal tunnel syndrome; CM: conventional method; IM: internal comparison method

Table 2.

Sensitivity and specificity of criteria for CTS
Sensitivity Specificity Accuracy PPV NPV

(%) (%) (%) (%) (%)
2.83-CM 98 17 49 44 93
2.83-IM 39 83 65 59 67
3.22-CM 49 93 76 83 74
3.22-IM 29 97 70 88 68

CTS: carpal tunnel syndrome; CM: conventional method; IM: internal comparison method; PPV: positive predictive value; NPV: negative predictive value

The criterion of 3.22-CM was found to detect moderate-to-severe CTS with a sensitivity of 80% and a specificity of 93%. The positive predictive value was 83%, and the negative predictive value was 92%. When the criterion of 3.22-IM was used, the sensitivity was 47%, and the specificity was 97% (Tables 3 and and4Table4).

Table 3.

Positive and negative tests in moderate-to-severe CTS hands
Positive Negative Total

(No.) (No.) (No.)
3.22-CM CTS (+) 24 5 29
CTS (–) 6 70 76
3.22-IM CTS (+) 14 2 16
CTS (–) 16 73 89
Total 30 75 105

CTS: carpal tunnel syndrome; CM: conventional method; IM: internal comparison method

Table 4.

Sensitivity and specificity of criteria for moderate-to-severe CTS
Sensitivity Specificity Accuracy PPV NPV

(%) (%) (%) (%) (%)
3.22-CM 80 93 90 83 92
3.22-IM 47 97 83 88 82

CTS: carpal tunnel syndrome; CM: conventional method; IM: internal comparison method; PPV: positive predictive value; NPV: negative predictive value

Data for the strength values of each hand demonstrated statistically significant differences in moderate-to-severe CTS hands compared with non-CTS hands. The median strength value of the monofilament was 407.3 mg (133.2–2041.7 mg) in moderate-to-severe CTS hands, and 166 mg (27.5–1309.3 mg) in non-CTS hands (p<0.001). There was no significant difference between non-CTS hands and mild CTS hands for these assessment values (p=0.566). The median strength value of the monofilament was 166 mg (67.6–166 mg) in mild CTS hands. A strength value of the monofilament > 288.4 mg had 80% sensitivity and 93.3% specificity for diagnosis of moderate-to-severe CTS, as identified by the ROC curve. The area under the ROC curve was 0.889 (95% confidence interval=0.810–0.968).

DISCUSSION

There is a lack of studies exploring the relationship between SWM testing outcomes and electrodiagnostically classified CTS. A characteristic feature of our study is that we investigated the capability of not only the threshold values of 2.83 and 3.22 but also the threshold value of 3.22 in diagnosing moderate-to-severe CTS, as well as the correlation between SWM testing and the severity of CTS. The main results of the present study showed that SWM testing using the criterion of 3.22-CM could be a valuable quantitative method for detecting moderate-to-severe CTS.

It has been demonstrated that limb ischemia significantly increases paresthesia, and SWM testing outcomes are one of the earliest manifestations of changes in nerve function,,,,,,,,,,,,,,). Although SWM testing is theoretically identified as a part of the clinical examination for patients with suspected CTS, the sensitivity and specificity of the test measurements vary widely among studies, which may be attributed to the variations in testing techniques and the disagreement regarding the abnormality of the threshold value. Pagel et al. performed a study to investigate the value of SWM testing in patients with electrophysiologically confirmed CTS using two criteria similar to ours with a threshold value of 2.83). The sensitivity and specificity ratios in their study were very close to our results. They obtained sensitivities of 98% and 13% and specificities of 15% and 88% for the CM and IM, respectively. Based on these results, the authors concluded that SWM testing lacks utility in the diagnosis of CTS.

Similarly, Szabo et al. evaluated the utility of clinical tests including SWM testing with a threshold of 2.83 for CTS), whereas they calculated 65% sensitivity and 42% specificity. Although, sensitivity would be higher (83%) if SWM testing were combined with Phalen’s maneuver, they suggested that SWM testing alone failed to diagnose CTS. One interpretation of their findings, including lower sensitivity and higher specificity, that is different from our study is that Szabo et al. considered the test was positive if any of the radial 3 and 1/2 digits had abnormal sensations (>2.83). Distinctively, the ring finger was not tested in the present study because it has a dual innervation from the median and ulnar nerves. Additionally, Szabo et al. used a monofilament kit containing 2.83 and 3.61 monofilaments, but the kit did not include a 3.22 monofilament.

Our results showed a sensitivity of 49% and a specificity of 93% for the criterion of 3.22-CM and a sensitivity of 29% and a specificity of 97% for the criterion of 3.22-IM. However, Mac Dermid et al. found a higher sensitivity (79% and 70%, respectively) and a lower specificity (64% and 70%, respectively) for both methods at these thresholds, and they suggested that accuracy was highest when a threshold of 2.83 was used in the long finger along with the small finger (sensitivity of 82% and specificity of 86%)). In addition, they concluded that further studies must determine which protocol and threshold abnormality is the best method for diagnosing CTS. Other studies have shown conflicting results related to the sensitivity and specificity of SWM testing,,,).

No clinical test to diagnose CTS has both high sensitivity and high specificity. The data related to sensitivity and specificity to detect CTS are in agreement with the findings reported in many earlier studies. The value of 2.83-CM had excellent sensitivity (98%) but low specificity (17%), whereas the value of 3.22-CM had high specificity (93%) but low sensitivity (49%). Therefore, we think that SWM testing is not useful as a screening tool in diagnosing CTS.

In our study, the relationship between the threshold value and electrophysiologically graded CTS was investigated. Although patients with CTS have been graded electrophysiologically in some of previous studies, to our knowledge, this is the first study to assess their relationship with monofilament values. Our results showed statistically significant differences in the mean monofilament value of the first three digits between moderate-to-severe CTS hands and non-CTS hands. In addition, the threshold value of 3.22 using CM detected moderate-to-severe CTS with high sensitivity and specificity. According to the ROC curve, a strength value of 288.4 mg as a cutoff is found between the strength value for the 3.22 monofilament and the strength value for the 3.61 monofilament and is very close to the strength value for the 3.22 monofilament. Taken together, the data available from both analyses reveal that SWM testing is likely a beneficial part of the clinical exam in the presence of moderate-to-severe CTS. Our data suggests there were no statistically significant differences in terms of the mean monofilament value between non-CTS and mild CTS hands. Similarly, it is sometimes difficult to diagnose CTS using only an electrophysiological study in cases of early and mild CTS.

The internal comparison method was used as part of the SWM testing when aiming to determine whether a patient had CTS in previous studies,,,,,,,,). The basis of the internal comparison can be explained by the non-pathologic causes of a diminished sensation within an individual, such as an individual with skin changes due to any reason. However, the results of the previous studies show that the sensitivity of this method is markedly lower in comparison with CM. According to our data, an evaluation of the fifth finger by internal comparison did not add any benefit, including the method of using the threshold value of 3.22 in diagnosing mild-to-severe CTS. Silver et al. reported that a significant percentage of patients with CTS also have ulnar nerve abnormality). Therefore, measurement of the fifth finger may not be considered an alternative method to distinguish CTS patients from asymptomatic controls.

The present study showed that SWM testing might be a beneficial part of clinical examination for detecting moderate-to-severe CTS when the criterion of 3.22-CM is applied. It could be an option for diagnosing carpal tunnel syndrome, especially for patients in whom other diagnostic methods are non-preferred or are confusing.

The current study has some limitations. First, there were more women than men in the sample. Although gender was not considered an independent variable in this study, future research at the individual level, predominantly in men, might allow comparisons between men and women that are more direct. Second, reliability was not assessed within the current study due to the retrospective nature of the study. However, the methods performed in the study were precisely described to prevent misinterpretations.

In light of our results, it can be concluded that a threshold abnormality of 3.22 using CM may detect moderate-to-severe CTS in patients. SWM testing may be of value as a diagnostic adjunct in cases of suspected CTS, particularly if electrophysiological tests are not available for any reason. Future studies with a larger sample size (and perhaps more men), as well as further analyses of different threshold abnormalities of moderate-to-severe CTS hands, are needed. Ultimately, SWM testing is a useful complementary tool for the clinical examination of CTS patients.

Acknowledgments

This work was supported by Research Fund of the Marmara University. Project number: SAG-BGS-150107-0008.

REFERENCES

1. Boland RA, Kiernan MC: Assessing the accuracy of a combination of clinical tests for identifying carpal tunnel syndromeJ Clin Neurosci, 2009, 16: 929–933. [PubMed[]
2. MacDermid J: Accuracy of clinical tests used in the detection of carpal tunnel syndrome: a literature reviewJ Hand Ther, 1991, 4: 169–176. []
3. McGill M, Molyneaux L, Yue DK: Use of the Semmes-Weinstein 5.07/10 gram monofilament: the long and the short of itDiabet Med, 1998, 15: 615–617. [PubMed[]
4. Hsu HY, Kuo LC, Chiu HY, et al.: Functional sensibility assessment. Part II: Effects of sensory improvement on precise pinch force modulation after transverse carpal tunnel releaseJ Orthop Res, 2009, 27: 1534–1539. [PubMed[]
5. MacDermid JC, Kramer JF, Roth JH: Decision making in detecting abnormal Semmes-Weinstein monofilament thresholds in carpal tunnel syndromeJ Hand Ther, 1994, 7: 158–162. [PubMed[]
6. Koris M, Gelberman RH, Duncan K, et al.: Carpal tunnel syndrome. Evaluation of a quantitative provocational diagnostic testClin Orthop Relat Res, 1990, 251: 157–161. [PubMed[]
7. Buch-Jaeger N, Foucher G: Correlation of clinical signs with nerve conduction tests in the diagnosis of carpal tunnel syndromeJ Hand Surg [Br], 1994, 19: 720–724. [PubMed[]
8. Szabo RM, Gelberman RH, Dimick MP: Sensibility testing in patients with carpal tunnel syndromeJ Bone Joint Surg Am, 1984, 66: 60–64. [PubMed[]
9. Massy-Westropp N, Grimmer K, Bain G: A systematic review of the clinical diagnostic tests for carpal tunnel syndromeJ Hand Surg Am, 2000, 25: 120–127. [PubMed[]
10. Demirci S, Savas S, Sonel B: Comparison of median sensory conduction values proximal and distal to wrist segment in mild carpal tunnel syndromeJ Phys Ther Sci, 2000, 12: 87–89. []
11. Atalay NS, Sarsan A, Akkaya N, et al.: The impact of disease severity in carpal tunnel syndrome on grip strength, pinch strength, fine motor skill and depressionJ Phys Ther Sci, 2011, 23: 115–118. []
12. Gellman H, Gelberman RH, Tan AM, et al.: Carpal tunnel syndrome. An evaluation of the provocative diagnostic testsJ Bone Joint Surg Am, 1986, 68: 735–737. [PubMed[]
13. Pagel KJ, Kaul MP, Dryden JD: Lack of utility of Semmes-Weinstein monofilament testing in suspected carpal tunnel syndromeAm J Phys Med Rehabil, 2002, 81: 597–600. [PubMed[]
14. MacDermid JC, Wessel J: Clinical diagnosis of carpal tunnel syndrome: a systematic reviewJ Hand Ther, 2004, 17: 309–319. [PubMed[]
15. American Association of Electrodiagnostic Medicine, American Academy of Neurology, and American Academy of Physical Medicine and Rehabilitation: Practice parameter for electrodiagnostic studies in carpal tunnel syndrome: summary statementMuscle Nerve, 2002, 25: 918–922. [PubMed[]
16. Stevens JC,American Association of Electrodiagnostic Medicine: AAEM minimonograph #26: the electrodiagnosis of carpal tunnel syndromeMuscle Nerve, 1997, 20: 1477–1486. [PubMed[]
17. Levin S, Pearsall G, Ruderman RJ: Von Frey’s method of measuring pressure sensibility in the hand: an engineering analysis of the Weinstein-Semmes pressure aesthesiometerJ Hand Surg Am, 1978, 3: 211–216. [PubMed[]
18. Lundborg G, Gelberman RH, Minteer-Convery M, et al.: Median nerve compression in the carpal tunnel—functional response to experimentally induced controlled pressureJ Hand Surg Am, 1982, 7: 252–259. [PubMed[]
19. Szabo RM, Slater RR, Jr, Farver TB, et al.: The value of diagnostic testing in carpal tunnel syndromeJ Hand Surg Am, 1999, 24: 704–714. [PubMed[]
20. Silver MA, Gelberman RH, Gellman H, et al.: Carpal tunnel syndrome: associated abnormalities in ulnar nerve function and the effect of carpal tunnel release on these abnormalitiesJ Hand Surg Am, 1985, 10: 710–713. [PubMed[]

Articles from Journal of Physical Therapy Science are provided here courtesy of Society of Physical Therapy Science

Semmes Weinstein 10g Sensory Tester www.medwoodworks.com

Monofilaments

Posted on Category:Monofilament Test

Monofilaments 

Occupational Medicine, Volume 68, Issue 8, November 2018, Pages 559–561, https://doi.org/10.1093/occmed/kqy116
Published:
16 November 2018

 

Semmes–Weinstein monofilaments are a semi-quantitative test of sensory loss. The idea, developed by Josephine Semmes and Sidney Weinstein, was to measure touch-pressure in a standardized way by controlling the force of an applied stimulus to the skin [1]. For this they replaced the ‘hairs’ previously used by Von Frey with more durable plastic filaments of variable diameters. Applied to the skin until they bend the monofilaments deliver the same force irrespective of any difference in observer or their degree of unsteadiness. They have been mostly used by orthopaedic surgeons as a tool for sensibility testing in hand surgery rehabilitation. They most likely test the skin receptor known as the Merkel disc which responds to constant touch-pressure. The original ‘long’ test kit of 20 monofilaments was grouped by five descriptive terms which were delineated by comparing with other tests of sensibility in 200 patients with peripheral nerve problems [2]:

  • Normal light touch.

  • Diminished light touch (with retention of two point discrimination).

  • Diminished protective sensation (difficulty with manual dexterity and abnormal two point discrimination).

  • Loss of protective sensation (markedly decreased stereognosis and manual dexterity).

  • Loss of deep protective sensation (as above plus a risk of injury).

Each monofilament is designated by a number which represents a given force and then grouped into colour-coded ranges. Weinstein developed an enhanced version with a textured rounded tip to create a more consistent area of skin surface contact with less likelihood of slippage (Weinstein Enhanced Sensory Test [WEST]) [1]. This is available as a set of five colour-coded monofilaments, attached to a handle, representing the five levels of sensory thresholds described above. This version is the most appropriate for an occupational health practice (Table 1). There is published age- and sex-matched normative data for WEST monofilaments (men and women age <55 years, 0.035 g-f; age >55 years, women 0.15 g-f, men 0.385 g-f) [3].

 

Table 1.

WEST monofilament classification

Monofilament number Force grams (g-f) Sensory perception [2]
Green 2.83 0.07 Normal
Blue 3.61 0.2 Diminished light touch
Purple 4.31 2.0 Diminished protective sensation
Red 4.56 4.0 Loss of protective sensation
Orange 6.65 200 Untestable

What should you use it for?

It is a requirement of the UK Control of Vibration at Work Regulations 2005 (CVAWR) to provide health surveillance for workers regularly exposed at or above an exposure action value of 2.5 m/s2. This is usually undertaken by a tiered approach by occupational health practitioners to detect early cases of hand–arm vibration syndrome (HAVS). WEST monofilaments are regularly used to assess sensory perception in tier 3 and tier 4 health surveillance for large cohorts of workers. The normal practice in HAVS health surveillance is to use the 0.2 g-f monofilament as a cut-off to determine when sensory perception is reduced.

Relevance to occupational health practitioners

The guidance to the CVAWR advises on the management of cases of HAVS based on the severity of the condition and its functional effects. The severity of HAVS, as currently appears in the guidance to the CVAWR, is graded by the use of a modified Stockholm Workshop Scale (SWS). A key determinant of progression within the SWS is the development of stage 2 sensorineural (2SN). WEST monofilaments are a useful indicator of the ‘loss of sensory perception’ occurring in stage 2SN. More specialized tests at tier 5 are advocated by some, particularly when determining the suitability of ongoing vibration exposure, but these are only available in a few specialist centres and WEST monofilaments are, therefore, a key component in routine large volume HAVS surveillance.

Ease of use

Peripheral neuropathy in HAVS affects the digits so WEST monofilaments are applied to the glabrous skin of the volar surface of the fingers between the tip and the whorl. Ideally all fingertips should be tested, but at least the index and little fingers, to cover median and ulnar nerve distribution. This should be done in a quiet room with the hand supported on a flat surface or towel. The filament under test is rotated on the handle clear of the others. While the subject averts their eyes, keeping the monofilament to the perpendicular, it is slowly applied to the skin until it bends for one second at least three times until a response (two out of three positive responses indicates a normal result). It is best to start by familiarizing the test subject with the procedure and then begin at a suprathreshold level, i.e. a 0.2g-f and work towards lighter or heavier filaments. Once felt there is no need to move to heavier monofilaments. Heavier monofilaments only require one application. To ensure consistency a short click from an interval marker is used to alert the subject of the test start and finish during which they are asked to respond with a ‘yes’ when the filament is felt.

Time to master

There are a number of test protocols which have been used but a review by the Health and Safety Laboratory of the Health and Safety Executive suggested that an inability to detect a 0.2 g monofilament was suggestive of significant vibration-induced neurosensory deficit when compared to other quantitative sensory testing (sensitivity 74 and 73%, respectively) [4]. It is important not to bend the shaft too little or too excessively (a ‘C’ shape curve is too much) or ‘bounce’ the filament as it will affect the calibration. It is best to try and develop a smooth rhythm when performing the test. If the filament is removed too quickly or jerkily, it may lead to an erroneous response. The shafts should not be touched directly or left near a heat source and should be cleaned between subjects. Some also add a few sham or dummy tests if subject inconsistency is suspected.

Semmes Weinstein 10g Sensory Tester

www.medwoodworks.com