The effect of external ankle support in chronic lateral ankle joint instability An electromyographic study JON KARLSSON,*† MD, PhD, AND GUNNAR O. From the
*Department of Orthopaedics,
East
ANDREASSON,‡ PhD
Hospital, Göteborg University, and the ‡Centre for
Biomechanics, Chalmers University of Technology, Göteborg, Sweden
Chronic lateral ankle instability is a common problem athletes, and several different surgical reconstructions have been described to correct the instability.4,6,8,9,1719,35 Although the results after surgical ankle joint reconstructions are satisfactory in most instances, many athletes choose other methods of treatment, such as ankle strapping or taping, either temporarily or permanently, to deal with their ankle instability. Although ankle taping is widely used among athletes, both after injury to support the weakened ankle when exposed to possible reinjury or to prevent injury, the role and mechanism behind the function of external ankle support is not exactly clear, i.e., does tape affect mechanical or functional ankle instability, or both? The aim of this study was to evaluate the effect of external ankle support (tape) on functional ankle joint instability in patients with radiologically verified mechanical instability. A reaction time for the peroneal muscle response was established and used to assess the effect of external ankle joint
ABSTRACT
among
We examined the effect of ankle taping on ankle joint stability by measuring mechanical stability using standardized stress radiographs. Anterior talar translation and talar tilt, both with and without ankle tape, were examined. The reduction of anterior talar translation and talar tilt with tape as compared to without tape was
insignificant.
The reaction time of the peroneus muscles was measured by electromyographic signal after a simulated ankle sprain on a tilting trapdoor. The reaction time was significantly slower in the unstable ankles of 20 athletes with unilateral ankle instability than in the stable contralateral ankles. With tape, the reaction time was significantly shortened, although not back to normal. The greatest improvement in reaction time was achieved in ankles with the highest degree of mechanical instability. Thus, the mechanism behind the function of ankle tape may be to restrict the extremes of ankle motion and to help shorten the reaction time of the peroneus muscles by affecting the proprioceptive function of the ankle.
support. MATERIALS AND METHODS
Twenty patients (10 men and 10 women, 10 right and 10 left ankles), all with isolated, unilateral, chronic (at least 6 months’ duration) lateral ankle instability caused by supination trauma, were selected for the study. The mean age was 24 years (range, 19 to 28). All patients had stable
Ankle joint instability can be defined either as mechanical or functional. The correlation between these two entities is not constant, although some patients with functional instability have mechanical instability as an underlying cause. Functional instability is a complex syndrome where functional, mechanical, and neuromuscular factors are all at fault. It has been shown that some patients with functional instability have peroneal muscle weakness and proprioceptive deficit.&dquo;-&dquo;-&dquo;
contralateral ankles and all had a reduced level of sports activity because of functional ankle instability, i.e., subjective complaint with no objective measurement, affecting activity level. All of the patients had mechanical instability of the func-
tionally unstable ankles verified by standardized stress radiographs. The radiographic investigation included the measurement of sagittal (anterior talar translation, ATT)
t Address correspondence and reprint requests to: Jon Karlsson MD, PhD, Associate Professor, Department of Orthopaedics, East Hospital S-416 85,
Gdteborg,
Sweden.
257
258
and lateral (talar tilt, TT) ankle instability, using the TELOS (TELOS, Weiterstadt, Germany) device for radiographic assessment. The radiographic investigations were carried out in a standardized way without pain or apprehension’,&dquo;, 17,25,31 (Fig. 1). The measurements were standardized in terms of position of the ankle joint (plantigrade), the force during the examination (150 N in both directions), the period the force was applied (30 seconds), and the method of measurements and calculations. All of the radiographic investigations were performed by the same assistant and all measurements by the same radiologist, who had no knowledge of the clinical status of the patient. An ankle inverting platform was constructed to elicit and simulate ankle sprain in the experimental situation. The platform can be tilted 30° from the horizontal plane with manual activation by pulling out a support slat (Fig. 2). The foot is held firmly on the platform to prevent it from slipping during the experiment and the subject is unaware when the tilt will occur. The other foot rests on another solid platform of the same size and height as the tilting platform. The interspace between the medial malleoli is 25 cm and the body weight is equally distributed between the two legs. The patients were instructed to relax the muscles of both legs and the platform was not tilted until the EMG signals showed a very low basal activity, indicating muscle relaxation.
Surface EMG signals were recorded using bipolar surface electrodes (silver/silver chloride) with orientation along the muscles. The electrodes were centered over the muscle bellies of the peroneus longus and peroneus brevis muscles and were placed in exactly the same position on both sides, using the medial and lateral malleoli and the anterior tibial border as landmarks. Signals were amplified and filtered by a firstorder band-pass filter (20 to 500 Hz). The start of the tilting triggered the start of the EMG recording. The first 100 ms were registered in all cases. Two muscles, the peroneus brevis and peroneus longus, were tested in each leg, on both the stable and unstable side. The reaction time was established as the time difference between the start of the tilting of the platform and the first muscular response registered on the EMG. The recording was repeated 10 times on each side and the results and the calculations were based on the mean values. The patients were tested with and without the ankles taped and both ankles were tested in all cases. An inelastic tape (Johnson & Johnson, Minneapolis, MN) was used with the closed Gibney technique without heel lock. There was no special preparation of the skin, such as shaving or spraying. The taping was done on both the stable and the unstable ankle by a professional athletic trainer in a similar way on each occasion.
RESULTS The results
expressed as mean ± SD. The stability by standardized stress radiographs, both the ATT and the TT, are presented in Table 1. There are
measurements obtained
Figure 1. The measurements of ankle joint stability were performed with the TELOS device. All variables of the radiographic investigation were standardized, i.e., position of the ankle, force, duration of stress, and calculations. Top, measurement of anterior talar translation (ATT). The ATT was measured in millimeters as the shortest distance between the posterior lip of the tibia and the talus after the provocation force was applied. Bottom, measurement of talar tilt (TT). The TT was measured in degrees as the angle between the tibia and talus after the provocation force was applied.
259 TABLE 1 Measurements of mechanical instability in stable and unstable ankles, with and without tape
TABLE 2 Measurement of reaction times in stable and unstable ankles, with and without tape
significantly (P < 0.001) shorter than in unstable ankles for both the peroneus longus and peroneus brevis. There was no significant difference between the right and left ankles, and no significant difference between men and women (Table 2). The reaction time was significantly (P < 0.05) shortened in unstable ankles when measured with tape compared to without tape (Table 2). However, this shortening of the reaction time was not found in all cases. In six ankles, the reaction time with tape was insignificantly shortened for the peroneus longus and in five of these for the peroneus brevis also. These were the ankles with the lowest degree of mechanical instability. The reaction time in stable ankles was not shortened with tape. DISCUSSION Of all time-loss
Figure 2. A trap-door mechanism was constructed to elicit and simulate ankle joint sprain. The EMG electrodes were placed over the muscle bellies of the peroneus brevis and peroneus longus muscles. Top, before tilting of the platform; bottom, after the platform has been tilted. was a statistically significant difference in mechanical ankle joint stability, both ATT and TT (P < 0.001) and between stable and unstable ankle joints. An insignificant reduction of mechanical instability, both ATT and TT, was found with tape compared to without (Table 1).
The reaction time was measured in milliseconds and defined as the time difference between the starting of the simulated ankle sprain to the first muscular response of the peroneus longus and peroneus brevis muscles registered by the EMG signals. The reaction time in stable ankles was
injuries in running and jumping sports, 20%
to 25% involve the ankle.22 The treatment of lateral ankle ligament injuries is designed to prevent chronic functional instability. The exact pathologic factors responsible for this subjective but complex syndrome are not known.’
StapleS2’ described four possible causes for functional instability: mechanical instability, peroneal weakness, tibiofibular sprain, and proprioceptive deficit. No correlation can be found in the literature between functional instability and tibiofibular sprain, but the other three items have been correlated with functional instability in varying de-
grees.l’° 12,1’, 32 Various studies have shown that tape is efficient in the of ankle sprains.5,13,15,20,31 Tape has been used both as a part of the early rehabilitation treatment after ankle ligament injuries and as a prophylactic measure.31 Various taping methods have been used. Rarick et a1. 27 found that the basketweave combined with a stirrup and heel lock
prevention
260
the greatest mechanical support. Stover3° has shown that the Air-Stirrup (Aircast Inc, Summit, NJ) is effective as an alternative to ankle taping. In this study we chose to use the closed Gibney technique. This is a rather simple ankle taping. We were interested in using a semirigid ankle taping, rather than one with heel lock, to measure the functional effect of the ankle tape. With stress radiographs it has been shown that static mechanical ankle instability, both in the sagittal plane (ATT) and the frontal plane (TT), can be reduced by ankle tape.17 Vaes et a1.33,34 have shown a significant reduction of TT after ankle taping. The support was, however, insufficient to eliminate TT. The best stability was obtained in the ankles with the highest degree of mechanical instability. However, after exercise the ankle tapes were generally loose-either the supporting strips of the tape broke or the anchoring lateral strips displaced downward, affording the ankle only limited protection.1,2,23,25,28,32,34 Ankle taping is not without controversy. 14 The prophylactic value of ankle taping has been shown, 13 while other studies have pointed out some negative factors. 1,2 The mechanism behind the biomechanical function of ankle tape has not been fully explained. McCluskey et a1.24 pointed out that tape limits the extreme ranges of ankle motion, i.e., partially increases the mechanical stability. This is in line with the results of Fumich et al., 13 who measured the effect of tape on combined foot and ankle motion and found that the tape restricts motion initially, loosens with exercise, but provides residual restriction after exercise. In this study, an insignificant reduction of both ATT and TT motion was found with tape as compared to without tape. There must, therefore, be other explanations than increased mechanical stability of the ankle behind the mechanism of ankle tape function, although a part of the function might be limiting the extremes of ankle motion. Bullard et a1.6have put forward the theory that tape might help to provide for better proprioception in the injured joint capsule and ligaments after ankle injuries. The proprioceptive reflex system consists of nerve receptors in the ligaments and the joint capsule connected by afferent nerves to the central nervous system. In the central nervous system, the afferent nerves are connected to the muscles by efferent nerves. The muscles then counteract the movements, provoking impulses in the receptors of the ligaments and the ankle joint capsule receptors. Glick et a1.15 found that tape had a stimulating effect on the peroneus brevis muscle in ankles with a significant TT measured with EMG and stopaction film. In ankles with insignificant TT, the tape had no effect on the function of the peroneus brevis. Sprigings et al. 28 examined the effectiveness of external ankle support in a similar experimental setup and found that preventive ankle strapping had no significant effect on the tension developed in the peroneus longus during a quick inversion (
*Department of Orthopaedics,
East
ANDREASSON,‡ PhD
Hospital, Göteborg University, and the ‡Centre for
Biomechanics, Chalmers University of Technology, Göteborg, Sweden
Chronic lateral ankle instability is a common problem athletes, and several different surgical reconstructions have been described to correct the instability.4,6,8,9,1719,35 Although the results after surgical ankle joint reconstructions are satisfactory in most instances, many athletes choose other methods of treatment, such as ankle strapping or taping, either temporarily or permanently, to deal with their ankle instability. Although ankle taping is widely used among athletes, both after injury to support the weakened ankle when exposed to possible reinjury or to prevent injury, the role and mechanism behind the function of external ankle support is not exactly clear, i.e., does tape affect mechanical or functional ankle instability, or both? The aim of this study was to evaluate the effect of external ankle support (tape) on functional ankle joint instability in patients with radiologically verified mechanical instability. A reaction time for the peroneal muscle response was established and used to assess the effect of external ankle joint
ABSTRACT
among
We examined the effect of ankle taping on ankle joint stability by measuring mechanical stability using standardized stress radiographs. Anterior talar translation and talar tilt, both with and without ankle tape, were examined. The reduction of anterior talar translation and talar tilt with tape as compared to without tape was
insignificant.
The reaction time of the peroneus muscles was measured by electromyographic signal after a simulated ankle sprain on a tilting trapdoor. The reaction time was significantly slower in the unstable ankles of 20 athletes with unilateral ankle instability than in the stable contralateral ankles. With tape, the reaction time was significantly shortened, although not back to normal. The greatest improvement in reaction time was achieved in ankles with the highest degree of mechanical instability. Thus, the mechanism behind the function of ankle tape may be to restrict the extremes of ankle motion and to help shorten the reaction time of the peroneus muscles by affecting the proprioceptive function of the ankle.
support. MATERIALS AND METHODS
Twenty patients (10 men and 10 women, 10 right and 10 left ankles), all with isolated, unilateral, chronic (at least 6 months’ duration) lateral ankle instability caused by supination trauma, were selected for the study. The mean age was 24 years (range, 19 to 28). All patients had stable
Ankle joint instability can be defined either as mechanical or functional. The correlation between these two entities is not constant, although some patients with functional instability have mechanical instability as an underlying cause. Functional instability is a complex syndrome where functional, mechanical, and neuromuscular factors are all at fault. It has been shown that some patients with functional instability have peroneal muscle weakness and proprioceptive deficit.&dquo;-&dquo;-&dquo;
contralateral ankles and all had a reduced level of sports activity because of functional ankle instability, i.e., subjective complaint with no objective measurement, affecting activity level. All of the patients had mechanical instability of the func-
tionally unstable ankles verified by standardized stress radiographs. The radiographic investigation included the measurement of sagittal (anterior talar translation, ATT)
t Address correspondence and reprint requests to: Jon Karlsson MD, PhD, Associate Professor, Department of Orthopaedics, East Hospital S-416 85,
Gdteborg,
Sweden.
257
258
and lateral (talar tilt, TT) ankle instability, using the TELOS (TELOS, Weiterstadt, Germany) device for radiographic assessment. The radiographic investigations were carried out in a standardized way without pain or apprehension’,&dquo;, 17,25,31 (Fig. 1). The measurements were standardized in terms of position of the ankle joint (plantigrade), the force during the examination (150 N in both directions), the period the force was applied (30 seconds), and the method of measurements and calculations. All of the radiographic investigations were performed by the same assistant and all measurements by the same radiologist, who had no knowledge of the clinical status of the patient. An ankle inverting platform was constructed to elicit and simulate ankle sprain in the experimental situation. The platform can be tilted 30° from the horizontal plane with manual activation by pulling out a support slat (Fig. 2). The foot is held firmly on the platform to prevent it from slipping during the experiment and the subject is unaware when the tilt will occur. The other foot rests on another solid platform of the same size and height as the tilting platform. The interspace between the medial malleoli is 25 cm and the body weight is equally distributed between the two legs. The patients were instructed to relax the muscles of both legs and the platform was not tilted until the EMG signals showed a very low basal activity, indicating muscle relaxation.
Surface EMG signals were recorded using bipolar surface electrodes (silver/silver chloride) with orientation along the muscles. The electrodes were centered over the muscle bellies of the peroneus longus and peroneus brevis muscles and were placed in exactly the same position on both sides, using the medial and lateral malleoli and the anterior tibial border as landmarks. Signals were amplified and filtered by a firstorder band-pass filter (20 to 500 Hz). The start of the tilting triggered the start of the EMG recording. The first 100 ms were registered in all cases. Two muscles, the peroneus brevis and peroneus longus, were tested in each leg, on both the stable and unstable side. The reaction time was established as the time difference between the start of the tilting of the platform and the first muscular response registered on the EMG. The recording was repeated 10 times on each side and the results and the calculations were based on the mean values. The patients were tested with and without the ankles taped and both ankles were tested in all cases. An inelastic tape (Johnson & Johnson, Minneapolis, MN) was used with the closed Gibney technique without heel lock. There was no special preparation of the skin, such as shaving or spraying. The taping was done on both the stable and the unstable ankle by a professional athletic trainer in a similar way on each occasion.
RESULTS The results
expressed as mean ± SD. The stability by standardized stress radiographs, both the ATT and the TT, are presented in Table 1. There are
measurements obtained
Figure 1. The measurements of ankle joint stability were performed with the TELOS device. All variables of the radiographic investigation were standardized, i.e., position of the ankle, force, duration of stress, and calculations. Top, measurement of anterior talar translation (ATT). The ATT was measured in millimeters as the shortest distance between the posterior lip of the tibia and the talus after the provocation force was applied. Bottom, measurement of talar tilt (TT). The TT was measured in degrees as the angle between the tibia and talus after the provocation force was applied.
259 TABLE 1 Measurements of mechanical instability in stable and unstable ankles, with and without tape
TABLE 2 Measurement of reaction times in stable and unstable ankles, with and without tape
significantly (P < 0.001) shorter than in unstable ankles for both the peroneus longus and peroneus brevis. There was no significant difference between the right and left ankles, and no significant difference between men and women (Table 2). The reaction time was significantly (P < 0.05) shortened in unstable ankles when measured with tape compared to without tape (Table 2). However, this shortening of the reaction time was not found in all cases. In six ankles, the reaction time with tape was insignificantly shortened for the peroneus longus and in five of these for the peroneus brevis also. These were the ankles with the lowest degree of mechanical instability. The reaction time in stable ankles was not shortened with tape. DISCUSSION Of all time-loss
Figure 2. A trap-door mechanism was constructed to elicit and simulate ankle joint sprain. The EMG electrodes were placed over the muscle bellies of the peroneus brevis and peroneus longus muscles. Top, before tilting of the platform; bottom, after the platform has been tilted. was a statistically significant difference in mechanical ankle joint stability, both ATT and TT (P < 0.001) and between stable and unstable ankle joints. An insignificant reduction of mechanical instability, both ATT and TT, was found with tape compared to without (Table 1).
The reaction time was measured in milliseconds and defined as the time difference between the starting of the simulated ankle sprain to the first muscular response of the peroneus longus and peroneus brevis muscles registered by the EMG signals. The reaction time in stable ankles was
injuries in running and jumping sports, 20%
to 25% involve the ankle.22 The treatment of lateral ankle ligament injuries is designed to prevent chronic functional instability. The exact pathologic factors responsible for this subjective but complex syndrome are not known.’
StapleS2’ described four possible causes for functional instability: mechanical instability, peroneal weakness, tibiofibular sprain, and proprioceptive deficit. No correlation can be found in the literature between functional instability and tibiofibular sprain, but the other three items have been correlated with functional instability in varying de-
grees.l’° 12,1’, 32 Various studies have shown that tape is efficient in the of ankle sprains.5,13,15,20,31 Tape has been used both as a part of the early rehabilitation treatment after ankle ligament injuries and as a prophylactic measure.31 Various taping methods have been used. Rarick et a1. 27 found that the basketweave combined with a stirrup and heel lock
prevention
260
the greatest mechanical support. Stover3° has shown that the Air-Stirrup (Aircast Inc, Summit, NJ) is effective as an alternative to ankle taping. In this study we chose to use the closed Gibney technique. This is a rather simple ankle taping. We were interested in using a semirigid ankle taping, rather than one with heel lock, to measure the functional effect of the ankle tape. With stress radiographs it has been shown that static mechanical ankle instability, both in the sagittal plane (ATT) and the frontal plane (TT), can be reduced by ankle tape.17 Vaes et a1.33,34 have shown a significant reduction of TT after ankle taping. The support was, however, insufficient to eliminate TT. The best stability was obtained in the ankles with the highest degree of mechanical instability. However, after exercise the ankle tapes were generally loose-either the supporting strips of the tape broke or the anchoring lateral strips displaced downward, affording the ankle only limited protection.1,2,23,25,28,32,34 Ankle taping is not without controversy. 14 The prophylactic value of ankle taping has been shown, 13 while other studies have pointed out some negative factors. 1,2 The mechanism behind the biomechanical function of ankle tape has not been fully explained. McCluskey et a1.24 pointed out that tape limits the extreme ranges of ankle motion, i.e., partially increases the mechanical stability. This is in line with the results of Fumich et al., 13 who measured the effect of tape on combined foot and ankle motion and found that the tape restricts motion initially, loosens with exercise, but provides residual restriction after exercise. In this study, an insignificant reduction of both ATT and TT motion was found with tape as compared to without tape. There must, therefore, be other explanations than increased mechanical stability of the ankle behind the mechanism of ankle tape function, although a part of the function might be limiting the extremes of ankle motion. Bullard et a1.6have put forward the theory that tape might help to provide for better proprioception in the injured joint capsule and ligaments after ankle injuries. The proprioceptive reflex system consists of nerve receptors in the ligaments and the joint capsule connected by afferent nerves to the central nervous system. In the central nervous system, the afferent nerves are connected to the muscles by efferent nerves. The muscles then counteract the movements, provoking impulses in the receptors of the ligaments and the ankle joint capsule receptors. Glick et a1.15 found that tape had a stimulating effect on the peroneus brevis muscle in ankles with a significant TT measured with EMG and stopaction film. In ankles with insignificant TT, the tape had no effect on the function of the peroneus brevis. Sprigings et al. 28 examined the effectiveness of external ankle support in a similar experimental setup and found that preventive ankle strapping had no significant effect on the tension developed in the peroneus longus during a quick inversion (
