Jaap Swanenburg1, Karel H. Stappaerts2, Bart Tirez3, ... for patients to bear load on their toes, such as hallux valgus patients. Since most such patients are ...
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JOURNAL OF APPLIED BIOMECHANICS, 2003, 19, 271-278 © 2003 by Human Kinetics Publishers, Inc.
Development and Reliability of a Measurement Device for Flexion Force of the First Metatarsophalangeal Joint Jaap Swanenburg1, Karel H. Stappaerts2, Bart Tirez3, Daniel Uebelhart1, and Geert Aufdemkampe4 1
University Hospital Zurich; 2Catholic University Leuven; 3University Hospital Leuven; 4Polytechnic of Utrecht
The purpose of this study was to present a method for repeated measurement of flexion force of the hallux in the metatarsophalangeal joint. The reliability of this measurement device was also examined. This device is suitable for situations where weight-bearing is contraindicated or when it is not possible for patients to bear load on their toes, such as hallux valgus patients. Since most such patients are female, the participants in this study were 24 healthy female volunteers. Age, weight, height, and leg dominance were determined for each. Muscle strength was measured using a device with a built-in MicroFET dynamometer. The result for the left hallux was ICC(3,1) .89 (95% CI .77–.95). The result for the right hallux was ICC(3,1) .94 (95% CI .87–.97). In the Bland and Altman plots, the reliability again appeared to be sufficient. The Pearson product-moment correlations gave poor results for the association between body weight, height, age, and mean force of the four trails. The test results indicate good reliability of the measurement device as used in this study. The advantage of this testing device is that it makes it easier to standardize measurements as opposed to the MicroFET used as a hand-held dynamometer. Also, patients can be tested in a nonload situation, which makes it possible to test hallux valgus at any time, and therefore it is possible to monitor variations in progression (or regression). Key Words: hallux, aged, women, strength
1Dept.
of Rheumatology and Institute of Physical Medicine, University Hospital Zurich, Gloriastrasse 25, 8091 Zurich, Switzerland; 2Dept. of Rehabilitation Sciences, Catholic University of Leuven, Leuven, Belgium; 3Dept. of Physical Medicine and Rehabilitation, University Hospital Leuven, Belgium; 4Dept. of Physical Therapy, Polytechnic of Utrecht, Utrecht, The Netherlands.
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Introduction The first metatarsophalangeal joint is the most important joint of the forefoot. It is heavily involved in the cyclic alternations of body movements which constitute human gait pattern. This gait pattern is described as the gait cycle and has five different modes of contact: heel contact, foot contact, heel-off, push-off, and toeoff (Rose & Gamble, 1993). The first metatarsophalangeal joint plays a major role in the transfer of body weight during locomotion (Mann & Coughlin, 1993). About 40% of body weight is placed on the toes in the final stages of forefoot contact, and most of this weight affects the first toe (Stokes, Hutton, & Stott, 1979). In contrast to this finding, another study found that 60.2% of normal loading is taken through the first toe (Hughes, Clark, & Klenerman, 1990). Wyss, McBride, Murphy, et al. (1990) used a dynamic footprint to determine the course of ground reaction force during gait. These footprints showed that the weight-load moves gradually from the second toe to the first toe during pushoff. The results of Wyss et al. showed that in a normal elderly population, the weight-load on the first metatarsophalangeal joint is on average 35% of body weight, though it may be as low as 10% and as high as 90% during the push-off phase. Shiavi (1985) has shown that there is some degree of contraction of the intrinsic muscles during push-off. These muscles, however, are relatively small compared to the flexor hallicus longus. In fact, the flexor hallicus longus is the largest muscle crossing the first metatarsophalangeal joint; therefore, it is the prime flexor during push-off and prevents excessive extension of the first toe. All of the studies cited above examined the first metatarsophalangeal joint in a gait situation. Little has been published concerning the force that can be generated in the first toe in a non-body-weighted situation. The present study aims to present a method for repeated measurement of flexion force of the hallux in the metatarsophalangeal joint. Furthermore, we developed a device suitable for situations where weight-bearing is contraindicated or when it is not possible for the patient to bear a weight load on the toes, such as with hallux valgus patients. Hallux valgus is a condition involving lateral displacement of the great to. It produces deformity of the first metatarsophalangeal joint with callous, bursa, or bunion formation over the bony prominence. In our opinion, such a condition should be tested in a nonweight-bearing situation. The increase in foot problems such as hallux valgus is most prominent in middle-aged women (Coughlin & Thompson, 1995). This is the reason for our selection of female participants. This measurement device can possibly serve as an outcome measurement in future randomized controlled trials.
Methods A MicroFET device (Force Evaluating and Testing, Hoggan Health Industries Inc., West Draper, Utah) was used to measure the strength of the flexion force of the hallux. The MicroFET is a dynamometer with a test range of 0.9–440 N (van Essen, Aufdemkampe, Houvast, & Nijeboer, 1995). The MicroFET was placed in an aluminium structure which was positioned vertically on a couch. A steel plate connected the MicroFET and the fixation structure of the foot. The MicroFET was secured to the structure in such a way that it was possible to both move and fixate the MicroFET in all possible positions within the structure, thus ensuring that all foot sizes could be accommodated (see Figures 1 and 2).
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MicroFET
Rail
Steel Plate
Fixation Screw
Position of the Metatarsophalangeal Joint
Fixation Screw
Fixation for the Straps
Aluminum Structure Figure 1 — Frontal view of the measurement device.
A measurement system in millimeters was added to the structure, which made exact positioning and retesting possible. It was used to restrain the participant’s foot and leg on the examination table and the measuring equipment. To reduce negative effects of the soft examination table, we placed a wooden board between the table and the measurement devices. To maintain stability to the extent possible, we had the measuring device fixed to the wooden board by means of straps, which were spun around the examination table (see Figure 3). As noted earlier, since most hallux valgus patients are female, the participants were 24 healthy female volunteers, all of whom gave written informed consent. All but two were right-leg dominant. Participant characteristics are listed in Table 1. Prior to testing, a brief interview was conducted with each participant to record age, weight, and height. Leg dominance was determined by asking each
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Fixation Screw MicroFET
MicroFET
Position of the Metatarsophalangeal Joint Fixation screw Steel Plate
Fixation Screw
Fixation for the Straps
Figure 2 — Side view of the measurement device.
one which leg she uses to kick a ball. The women were then placed supine on the examination table with the leg to be tested affixed to the table and the testing device. The knee was in full extension and the foot was in 90° dorsiflexion. The hinge of a stainless steel plate was positioned directly under the first metatarsophalangeal joint. The coordinates of the testing device in this position were read and noted. The women began with three isometric test pushes against the steel plate. After these test pushes, they were instructed to push three times with maximum strength; the results of these three contractions were recorded. There was a 30-sec break between contractions. The procedure was then performed on the other foot. The testing of each foot—three maximum contractions—represented one trial. To counterbalance any order or learning effect of the starting foot, every other participant began the session with the right foot while the alternating participants began with the left foot. The second session was started approximately 4 hours later and each participant began the second session with the alternating foot. The mean of each participant’s three runs was calculated and the data were
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Figure 3 — A foot placed against the measurement device with the fixation straps.
Table 1 Characteristics of the 24 Participants
Minimum Age Weight (kg) Height (m)
35.95 51 1.56
Maximum 56.01 90 1.75
Mean
SD
45.84 67.58 1.63
5.83 8.71 5.66
analyzed for normality with the Kolmogorov/Smirnov test. Differences between sessions were tested by means of a paired t-test. Reliability of the measurement of the hallux strength over two sessions was estimated via intraclass correlation coefficient. ICC model 3.1 was selected because of its appropriateness for testing intrarater reliability (Portney & Watkins, 1993). In addition to classical analysis of reliability using ICC, we also used Bland and Altman plots to gain more information on the reliability of our measurements (Bland & Altman, 1986).
Results All data appeared to be normally distributed. The average of the participant’s actual forces for the right hallux for the first measurement was 97.8 N, and for the second measurement it was 109.8 N. For the left hallux, the average for the first measurement was 125.1 N, and for the second measurement it was 129.2 N. There was a significant difference, p = 0.002, between the two sessions of the left hallux, but no significant difference, p = 0.451, between the two sessions of the right hallux. Results of the paired t-test are listed in Table 2.
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Table 2
Results of Paired t-Test
Variables
Left foot
Right foot
Mean difference (N) Standard deviation Standard error of the mean Lower 95% CI of difference* Upper 95% CI of difference t-value Degrees of freedom Two-tailed significance
–11.9 17 3.5 –19.2 –4.8 –3.5 23 0.002
–2.5 15.6 3.2 –9.1 –4.2 –0.8 23 0.451
* CI = confidence interval.
The reliability for the left hallux was ICC(3,1) .89, with a 95% confidence interval of .77–.95. The reliability for the right hallux was ICC(3,1) .94, with a 95% confidence interval of .87–.97. Differences against mean plots were used regarding the reliability of our measurements. Since only one data point was outside ±1.96 standard deviation of the mean of the two measurements, the reliability again appears to be sufficient (see Figure 4). The 1.96 standard deviation boundaries in Figure 4 represent approximately 33 N below or above the mean. Finally, we performed Pearson product-moment correlations as a measure of association between age, body weight, height, and the mean force of the four trials. The associations between age, body weight, height, and mean force varied between rp 0.034 and –0.35 (all nonsignificant).
Discussion Our results indicate good reliability of the measurement device used in this study. Hand-held dynamometers such as the MicroFET have been used for reliability in several studies (Bohannon & Andrews, 1987; van Essen et al., 1995), but to our knowledge this was the first study using a hand-held dynamometer as part of a testing device. The advantage of this testing device is that it makes it easier to standardize measurements as opposed to the MicroFET used as a hand-held dynamometer, and secondly, patients can be tested in a non-load situation. Hallux valgus patients can be tested on this device without any pressure from lateral, medial, or dorsal sides. This makes it possible to test hallux valgus at any time and therefore to monitor variations in progression. Surprisingly, we found a significant difference between the two sessions of the left hallux. This could be explained by the fact that 22 of the 24 participants were right-foot dominant. Non-dominance may lead to greater fluctuations in muscular strength. Dereymaeker (1996) demonstrated clearly that there are differences between the left and right foot, and that there is some indication of “right-footedness” in most people. Similar differences were found between the right and left foot in the hallux valgus group. The influence that exercise may have on hallux muscular strength should be studied further. Good walking habits and appropriate training are important for post-surgical hallux valgus
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Figure 4 — Bland and Altman plot. L1 = results of first session of the left hallux; L2 = results of second session of the left hallux; R1 = results of first session of the right hallux; R2 = results of second session of the right hallux.
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patients (Dereymaeker, 1996). The limitation of our device is that it can only be used in a static non-weight-bearing situation and it is not a functional test. Combining the results of this device and those of joint reaction forces (Wyss et al., 1990), or pododynographic studies (Dereymaeker, 1996), may lead to a better understanding of human gait.
References Bland, J.M., & Altman, D.G. (1986). Statistical methods for assessing agreement between two methods of clinical measurement. Lancet I, 307-310. Bohannon, R.W., & Andrews, A.W. (1987). Interrater reliability of hand-held dynamometry. Physical Therapy, 67, 931-933. Coughlin, M.J., & Thompson, F.M. (1995). The high price of high-fashion footwear. Instructor’s Course Lecture, 44, 371-377. Dereymaeker, G. (1996). Management of hallux valgus and metatarsalgia: A comparative study of various surgical procedures for hallux valgus based on clinical and radiographic assessment and gait analysis. PhD thesis, Catholic University of Leuven. Antwerpen: HNC Agency Hughes, J., Clark, P., & Klenerman, L. (1990). The importance of the toes in walking. The Journal of Bone and Joint Surgery. British Volume, 72, 245-250. Mann, R.A., & Coughlin, M.J. (1993). Surgery of the foot and ankle. St Louis: Mosby. Portney, L.G., & Watkins, M.P. (1993). Foundations of clinical research. Applications to practice. Norwalk, CT: Appleton & Lange. Rose, J., & Gamble, J.G. (1993). Human walking. Baltimore: Williams & Wilkins. Shiavi, R. (1985). Electromyographic patterns in adult locomotion: A comprehensive review. Journal of Rehabilitation Research and Development, 22, 85-98. Stokes, I.A.F., Hutton, W.C., & Stott, J.R. (1979). Forces acting on the metatarsals during normal walking. Journal of Anatomy, 129, 579-590. van Essen, D., Aufdemkampe, G., Houvast, M., and Nijeboer, I. (1995). Reliability study of the MicroFET for pressure pain thresholds of myofascial trigger points in patients who have been operated on for herniated nucleus pulposi. Physiotherapy Theory and Practice, 11, 81-88. Wyss, U.P., McBride, I., Murphy, L., Cooke, T.D.V., & Olney, S.J. (1990). Joint reaction forces at the fist MTP joint in a normal elderly population. Journal of Biomechanics, 23, 977-984.
Acknowledgments Thanks are due to the Technical Facility Dept. of the Polytechnic of Utrecht, Dept. for Physical Therapy, for their assistance in building the frame used in this study. We also thank Prof. Dr. Louis Peeraer, Professor of Motor Rehabilitation, Catholic University of Leuven, Dept. of Physical Medicine and Rehabilitation – University Hospital Leuven, Belgium, for his technical advice, and Leanne Pobjoy for her help in preparing the manuscript.
Authors’ Note No commercial party having a direct interest in the results of research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated.
