displacement of the ankle was measured at 30 and 60 N of anterior load in 14 patients with acute ... Ankle ligament injuries are extremely common; approxi-.
0363-5465/103/3131-0226$02.00/0 THE AMERICAN JOURNAL OF SPORTS MEDICINE, Vol. 31, No. 2 © 2003 American Orthopaedic Society for Sports Medicine
Anterior Drawer Test for Acute Anterior Talofibular Ligament Injuries of the Ankle How Much Load Should be Applied During the Test? Harukazu Tohyama,*† MD, PhD, Kazunori Yasuda,* MD, PhD, Yasumitu Ohkoshi,‡ MD, PhD, Bruce D. Beynnon,§ PhD, and Per A. Renstrom,储 MD, PhD From the *Division of Medical Bioengineering and Sports Medicine, Department of Advanced Surgery, Hokkaido University School of Medicine, Sapporo, the ‡Department of Orthopaedic Surgery, Hakodate Central General Hospital, Hakodate, Japan, the §Department of Orthopaedics and Rehabilitation, University of Vermont College of Medicine, Burlington, Vermont, and the 储Section of Sports Medicine, Department of Surgical Science, Karolinska Institute, Stockholm, Sweden
Background: There is a lack of consensus regarding the magnitude of load for performing the anterior drawer test in evaluating acute ankle injuries. Purpose: To determine how much load should be applied during the anterior drawer test to detect the integrity of the anterior talofibular ligament. Methods: First, the anterior-posterior load-displacement response of nine cadaveric ankles was measured. Second, anterior displacement of the ankle was measured at 30 and 60 N of anterior load in 14 patients with acute tears of the anterior talofibular ligament. Results: In the cadaver study, the increased displacement by sectioning of the ligament measured at 10, 20, 30, and 40 N of anterior load were significantly greater than those measured at 60 N. In vivo examination of the subjects without anesthesia demonstrated that the injured-to-normal displacement value at 30 N of anterior load was significantly greater than the value at 60 N. Conclusions: This study suggests that a large magnitude of anterior load is not necessary to detect the integrity of the ligament during the anterior drawer test. Clinical Relevance: When evaluating the integrity of the anterior talofibular ligament in cases of acute ankle ligament injury, a relatively low-magnitude load should be applied. © 2003 American Orthopaedic Society for Sports Medicine
uate the integrity of the anterior talofibular ligament of the ankle.4, 6, 8, 11, 12, 14 –18 Integrity of the ligament is determined by the amount of anterior talar displacement produced in the sagittal plane. Many studies of the anterior drawer test have been reported, some of which have demonstrated its value for evaluating the integrity of the anterior talofibular ligament.6, 7, 12, 13, 16, 17 Investigators in other studies, however, have found this test to be unreliable.5, 9, 14 This divergence may be attributed to the fact that an optimal magnitude of load for performing the anterior drawer test has yet to be defined. In particular, it is difficult to examine the ankle in acutely injured patients because they protect their ankles by muscular contraction during the examination, thereby stiffening their ankle joint.2, 16
Ankle ligament injuries are extremely common; approximately 23,000 ankle injuries occur in the United States each day.2 The anterior talofibular ligament is the most frequently injured ligament in lateral ankle sprains.3 It is important that a clinician correctly evaluate the extent of injury to apply the proper method of treatment.4, 8, 15 To establish a correct diagnosis, clinicians frequently use stress tests. Among these, the anterior drawer test is the most common mode of clinical examination used to eval-
† Address correspondence and reprint requests to Harukazu Tohyama, MD, PhD, The Department of Orthopaedic Sports Medicine, Hokkaido University School of Medicine, Kita-15 Nishi-7 Kita-ku, Sapporo 060-8638, Japan. No author or related institution has received any financial benefit from research in this study.
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Acute sprains of the lateral ankle ligament complex are a frequently seen injury in a general orthopaedic practice.2 Therefore, stress tests under anesthesia may be impractical. However, the optimal magnitude of anterior-directed load required to detect the integrity of the anterior talofibular ligament without producing a pain-elicited contraction of the patient’s musculature during the anterior drawer test has not been determined. The purpose of this study was to determine how much load should be applied during the anterior drawer test to detect the integrity of the anterior talofibular ligament, particularly in acutely injured patients.
MATERIALS AND METHODS Experimental Design Ex vivo and in vivo experiments were designed to determine how much load should be applied during the anterior drawer test to detect the integrity of the anterior talofibular ligmament in acute cases of injury. For the ex vivo study, we measured the anterior-posterior load-displacement responses of nine human cadaveric ankles, first with the specimens intact and then with the anterior talofibular ligament completely sectioned. By using a three degree of freedom laxity measurement device, we were able to clarify the magnitude of anterior load necessary to detect the effect of sectioning on anterior displacement without any effects of the musculature. For the in vivo study, we examined 14 patients with acute, complete tears of the anterior talofibular ligament. The examination was directed at evaluating the effects of the muscular contraction elicited by the patients in their efforts to protect themselves from the pain produced by anterior load on anterior displacement of the ankle joint. With the subjects not under anesthesia, we measured the anterior displacement of the ankle at 30 and 60 N of anterior load by using a custom-designed ankle laxity-testing device.18 These in vivo measurements were then repeated while the subject was under epidural anesthesia. Ex Vivo Experiment Specimens. Nine human ankle specimens were obtained from five male and four female cadavers and stored at –20°C. The mean age of the specimens was 52.3 years (range, 16 to 62). Each specimen was thawed at room temperature for 12 hours before testing. The skin, subcutaneous tissues, tendons, and muscles crossing the ankle and subtalar joints were removed, and the ligaments and capsular tissues were left intact. The anatomic position of the fibula relative to the tibia was preserved with a bone screw driven through the fibula and tibia. The tibia and fibula were fixed in a copper cylinder (7.5 cm in diameter) with polymethyl methacrylate. Mechanical Testing. A previously developed experimental fixture was used to simulate the anterior drawer test as it is performed clinically18 (Fig. 1). The direction of applied load was aligned parallel to the bottom of the foot and along the long axis of the second metatarsus in the
Figure 1. The schema of the experimental fixture used to apply loads to the cadaveric ankle. sagittal plane. Before testing, the fixture permitted the following rotations of the foot relative to the tibia: abduction-adduction, dorsal-plantar flexion, and internal-external rotation. During testing, all rotations were held fixed. The anterior-posterior load and corresponding displacement were monitored with a materials testing system (model 810, MTS, Prairie Eden, Minnesota). Each test consisted of seven cycles of anterior-posterior directed load applied to the limits of ⫾60 N, with use of a ramp function with a loading frequency of 0.1 Hz with the foot at neutral, 10°, or 20° of ankle plantar flexion. The load cell was zeroed electronically to compensate for the weight of the upper fixture. The zero-load value was determined as the inflection point of the load-displacement curve of the ankle produced by the first four preconditioning cycles. After the four preconditioning cycles, the next three cycles of the load-displacement response were found to be repeatable. After this test for the intact specimen, the anterior talofibular ligament was sectioned completely and the specimen was tested as previously described for the intact specimen. The load-displacement relationship was characterized by a sigmoid curve. A flat region was observed on and about the zero applied load magnitude. Therefore, we used the position at 60 N of posterior load applied as a reference, because it was difficult to determine a reference position at zero load ex vivo. For each test, the displacements from the position at 60 N of posterior load at 10, 20, 30, 40, 50, and 60 N of anterior load in the last three cycles of anterior load were respectively averaged. In Vivo Experiment Subjects. Fourteen subjects (10 men and 4 women) with acute, complete tears of the anterior talofibular ligament
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were examined for the in vivo portion of this study. The mean age of subjects was 23.2 years (range, 19 to 27). None of the subjects had a history of contralateral ankle sprains. Examinations and surgical procedures in all cases were performed by one of the authors (HT) within 1 week of the injury (average, 4.9 days; range, 1 to 7). All of the procedures were explained in advance to the subjects. Each subject signed an informed consent form. By means of an incision made posterior to the lateral malleolus, we opened the ankle joint and the peroneal tendon sheath to identify the anterior talofibular ligament and the calcaneofibular ligament. The incision was part of the standard approach for surgical repair of injured ligaments. In all cases, complete rupture of the anterior talofibular ligament combined with a capsular tear was confirmed. In three cases, there was also a partial rupture of the calcaneofibular ligament. Measurement of Anterior Ankle Laxity. The anterior displacement of the calcaneus relative to the tibia at 30 and 60 N of anterior load was objectively assessed by using a custom-designed ankle laxity testing device (Fig. 2A). The test was performed on the day of surgery, usually immediately before surgery by one of the authors (HT). Before the surgical procedure, and with the subject not under anesthesia, the anterior displacement of the ankle was measured at 30 and 60 N of anterior load. The subject was placed prone on the operating table. The lower leg was placed into a position of 90° of knee flexion, and the testing device was attached to the leg with the ankle in 15° of plantar flexion (Fig. 2B). An anterior force was manually applied to the calcaneus, with force monitored by a force gauge (Ohba Instrument Co., Tokyo, Japan) attached to the device. A 30- and 60-N anterior force was applied to the posterior side of the calcaneus in the sagittal plane. Subsequent anterior displacement was measured with a digimatic indicator (IDU-1025, Mitutoyo Co., Kawasaki, Japan; resolution, 0.01 mm) attached to the testing device. Both ankles were examined, with the uninjured ankle always examined before the injured one. Our preliminary data for 30 subjects (15 men and 15 women) without any ankle injuries confirmed that the 95% confidence limit of repeatability for our measurement technique was ⫾0.79 mm (Fig. 3). These measurements were then repeated while the subject was under epidural anesthesia and after both legs of the subject had become fully relaxed. The difference in anterior displacement between the injured and normal ankles was calculated at 30 and 60 N of anterior load with and without anesthesia. After the anterior displacement measurement, surgical repair of the injured ligaments was performed. Statistical Analysis In the ex vivo study, the effect of sectioning the anterior talofibular ligament was determined by using a paired t-test at each magnitude of anterior load. The effects of the load magnitude and the ankle flexion angle on the difference in the displacement before and after sectioning the anterior talofibular ligament were analyzed with a twoway analysis of variance with Fisher’s protected least
Figure 2. In vivo measurement of ankle laxity. A, a customdesigned ankle laxity testing device; B, patient positioning for the instrumented anterior drawer test. significant difference tests for post hoc multiple comparisons. For the in vivo study, the difference in anterior displacement between the injured and normal ankles was determined by using a paired t-test for each condition. In
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Figure 3. The repeatability analysis of the in vivo measurement of ankle laxity for 30 subjects without any ankle injuries. addition, the injured-normal differences at 30 N of anterior load were compared with those at 60 N of anterior load by using an unpaired t-test for conditions with and without anesthesia, respectively. The significance limit was set at P ⫽ 0.05 for each test.
RESULTS Ex Vivo Experiment Sectioning of the anterior talofibular ligament produced a significant increase of anterior displacement at 10, 20, 30, 40, 50, and 60 N of anterior load at each angle of plantar flexion (P ⬍ 0.001) (Fig. 4). An analysis of variance demonstrated significant effects of the magnitude of applied load and the angle of plantar flexion on the differences in displacement values before and after the sectioning (magnitude of applied load: P ⫽ 0.001, power [1-] ⫽ 0.999; angle of plantar flexion: P ⫽ 0.001, power [1-] ⫽ 0.995; their interaction: P ⫽ 0.626). The increased values seen on sectioning the anterior talofibular ligament at 10, 20, 30, and 40 N of anterior load were significantly greater than those seen at 60 N (10 N, P ⫽ 0.001; 20 N, P ⫽ 0.005; 30 N, P ⫽ 0.007; 40 N, P ⫽ 0.001). However, we did not find significant differences between the increased values when the anterior talofibular ligament was sectioned at 50 and 60 N (P ⫽ 0.100, power [1-] ⫽ 0.409). The increased values seen when the ligament was sectioned at 10° and 20° of plantar flexion were significantly greater than those seen with the ankle in the neutral position (10° of plantar flexion, P ⫽ 0.001; 20° of plantar flexion, P ⫽ 0.004). However, we did not find significant differences between the increased values when the ligament was sectioned at
Figure 4. Increased displacement measured during the ex vivo experiment after sectioning the anterior talofibular ligament at 10, 20, 30, 40, 50, and 60 N of anterior load from the position at 60 N of posterior load. A, neutral plantar flexion; B, 10° of plantar flexion; C, 20° of plantar flexion.
10° and 20° of plantar flexion (P ⫽ 0.092, power [1-] ⫽ 0.389).
In Vivo Experiment In the in vivo study, examination of the subjects not under anesthesia demonstrated that the anterior displacement value of the injured ankle at 30 N of anterior load was significantly greater than the value of the contralateral ankle, whereas there was no significant difference at 60 N of anterior load (Fig. 5). The injured-to-normal anterior displacement value of the ankle at 30 N of anterior load was significantly greater than the value at 60 N of anterior load. With the subjects under anesthesia, the anterior displacement values of the injured ankle at 30 and 60 N of anterior load were significantly greater than the values of the contralateral ankle. There were no significant differences between the injured-to-normal anterior displace-
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Figure 5. Results of the in vivo experiment. The injured-tonormal anterior displacement value of the ankle at 30 and 60 N with and without anesthesia. ment values of the ankle at 30 and 60 N with the patients under anesthesia.
DISCUSSION In a general orthopaedic practice, acute sprains of the lateral ankle ligament complex are a frequently encountered patient injury.2 Therefore, stress tests under anesthesia may be impractical. The trauma may have occurred several days before examination of the patient by an orthopaedic surgeon. Often, the ankle is swollen, with generalized tenderness to palpation.4, 8, 15 It behooves the practitioner to be able to efficiently evaluate these injuries. Without the patient under anesthesia, however, it is difficult for the clinician to examine the ankle after acute sprains. This is because patients protect the ankle by contracting their musculature during the examination, thereby stiffening the ankle joint. Therefore, the present study was conducted to determine how much load should be applied during the anterior drawer test to detect the integrity of the anterior talofibular ligament. In the first portion of our study, we precisely examined load-displacement responses of human cadaveric specimens with a three degree of freedom laxity measurement device that simulated the anterior drawer test as it is performed clinically. The purpose of the ex vivo portion of this study was to determine the magnitudes of the applied load and the angle of ankle plantar flexion necessary for the in vivo measurements so that we could reduce the number of variables tested. We needed to test fewer variables in the in vivo study because measurements were performed before surgery, limiting the amount of time available for measurements.
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As the results of our ex vivo experiment show, the increased values seen on sectioning the anterior talofibular ligament at 10, 20, 30, and 40 N of anterior load were significantly greater than those seen at 60 N. Lapointe et al.,10 using a six degree of freedom instrumented linkage in an ex vivo study, examined the flexibility characteristics of the ankle complex before and after sectioning of anterior talofibular ligament. They found that the most sensitive parameter for detecting the presence of anterior talofibular ligament injury was early flexibility during the anterior drawer test. Their results are in agreement with our findings that the largest increase in displacement seen after ligament sectioning occurs in the low-loading region. These findings suggest that a large magnitude of anterior load is not necessary to detect ligament integrity during the anterior drawer test when no muscle forces are present. Therefore, we considered that the 60 N of anterior load was enough and so we chose 30 and 60 N as magnitudes of applied anterior load in the in vivo measurements. In addition, our ex vivo data showed that the increases in the displacement after sectioning at 10° and 20° of plantar flexion were significantly greater than that at neutral plantar flexion. These findings are consistent with the results of previous studies.11, 14, 18 Therefore, we performed the in vivo measurement of the ankle laxity at 15° of plantar flexion. The present ex vivo experiment showed that the increased values seen on sectioning the anterior talofibular ligament at 60 N of anterior load were significantly lower than those seen at 10, 20, 30, or 40 N in the cadaveric ankle. We consider that this counter-intuitive phenomenon was due to the change in load-displacement characteristics of the cadaveric ankle caused by sectioning of the ligament. A steep portion was observed in a loaddisplacement curve after the ligament was sectioned, because the anterior edge of the tibial joint surface presumably carried the anterior load at this portion (Fig. 6). Therefore, joint stiffness was considered to be higher between 10 and 60 N of anterior load after sectioning of the ligament rather than before the sectioning. The high degree of joint stiffness seen after a large displacement in
Figure 6. Representative load-displacement responses of the ankle before and after the sectioning of the anterior talofibular ligament (ATFL) in the ex vivo experiment.
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the ankle after anterior talofibular ligament sectioning might reduce the increased values seen on sectioning of the ligament at 60 N of anterior load (Fig. 6). In the second, in vivo, portion of our study, we examined subjects with acute, complete ruptures of the anterior talofibular ligament. Our purpose was to evaluate the effects of the muscular contraction elicited by the patients in their effort to protect themselves from the pain produced by anterior load on anterior displacement of the ankle joint. The results of our in vivo experiment with the patients under anesthesia have demonstrated that the anterior displacement values of the injured ankle at both 30 and 60 N of anterior load were significantly greater than those of the normal ankle. The in vivo measurements made without the patients under anesthesia revealed that the anterior drawer test performed at 30 N of anterior load was more sensitive at detecting an anterior talofibular ligament tear than the anterior drawer test performed at 60 N of anterior load. This may be because, at 60 N, the subjects contracted their musculature in an effort to protect themselves from the pain produced by an excessive magnitude of anterior load. Becker et al.1 reported that anterior drawer tests on the injured ankles of patients without anesthesia showed that there was almost no laxity or less laxity than in the uninjured ankle with a load of 150 N. They also found that the displacement values at an anterior load of 150 N without anesthesia (peroneal block) during anterior drawer testing were significantly smaller than those with anesthesia. Both our study and that of Becker et al. suggest that an excessively high magnitude of anterior load produces muscular contraction around the ankle and thereby stiffens the ankle joint. In the present study, we did not attempt to compare ex vivo measurements with in vivo measurements because the laxity measurement techniques employed ex vivo and in vivo were different. However, we recognize that the differences in the conditions between ex vivo and in vivo portions of the study might have affected our results. First, the specimens used in the ex vivo portion of the study were from relatively old donors. This difference in age between the ex vivo specimens (range, 16 to 62 years) and the in vivo subjects (range, 19 to 27 years) might have affected the results. However, we could not find obvious differences in increased ankle displacement after ligament sectioning among specimens with different ages in the ex vivo experiment. For example, in specimens from cadavers less than 30 years of age, the mean increased values seen after sectioning the anterior talofibular ligament at 30 N of anterior load were 2.3, 3.2, and 2.9 mm at 0°, 10°, and 20° of ankle plantar flexion, respectively, whereas the values were 2.3, 3.2, and 2.7 mm in specimens from cadavers older than 30 years. Therefore, we believe that there was little effect of specimen age on increased ankle displacement after ligament sectioning in the ex vivo experiment. A second factor to consider is that the displacement data for ex vivo mechanical testing were obtained at ⫾60 N applied cyclic loading, whereas the data for the in vivo measurements were obtained at discrete load increments,
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that is, anterior loads of 30 and 60 N. For the ex vivo testing, we preferred the cyclic loading protocol to confirm that the load-displacement responses were repeatable during ⫾60 N applied loading. On the other hand, our portable testing device for the in vivo measurements could only measure the ankle displacement between certain magnitudes of applied load, but it was easy to set up the testing and thereby examine both legs within 10 minutes. However, the differences in loading conditions between ex vivo and in vivo measurements might have affected the ankle displacement data. In addition, secondary injuries of structures other than the anterior talofibular ligament might reflect that the injured-to-normal differences in ankle displacement in patients under anesthesia in vivo were slightly greater than the increase in ankle displacement by selective sectioning of the ligament ex vivo. We found a partial rupture of the calcaneofibular ligament in three subjects who underwent in vivo testing. Larsen11 reported that subsequent transection of the calcaneofibular ligament after cutting of the anterior talofibular ligament increased displacement during anterior loading. The capsular structures of the ankle might also have been involved in our in vivo cases with inversion injuries. In conclusion, the ex vivo portion of our study demonstrated that a high magnitude of anterior load is not necessary to detect the integrity of the anterior talofibular ligament during the anterior drawer test. Furthermore, the in vivo portion of our study revealed that the anterior drawer test performed at 30 N of anterior load is more sensitive at detecting an anterior talofibular ligament tear compared with the test performed at 60 N of anterior drawer when the subject is not under anesthesia. On the basis of these results, we recommend that approximately 30 N of anterior load be applied during the anterior drawer test to evaluate integrity of the ligament in acutely injured patients. In clinical use of the anterior drawer test, a high magnitude of anterior load should not be applied to overcome a patient’s protective response of muscular contraction. Rather, a relatively low magnitude should be applied, thereby avoiding production of this muscular contraction. A commercially available apparatus, such as the Telos stress device (Telos, Hungen-Obbornhofen, Germany), is sometimes used for stress radiographs as a diagnostic tool.9 The Telos stress device usually applies a relatively high anterior load, approximately 150 N, to the ankle joint. Therefore, when diagnosing acute anterior talofibular ligament injuries, clinicians should recognize that stress radiographs taken with the stress device have a potential false-negative error because of the muscular contraction produced.
ACKNOWLEDGMENT The authors thank Mr. Tomoya Moriguchi, Moriguchi Brace Co., for his contributions to the development of the ankle laxity-testing device.
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American Journal of Sports Medicine 10. Lapointe SJ, Siegler S, Hillstrom H, et al: Changes in the flexibility characteristics of the ankle complex due to damage to the lateral collateral ligaments. An in vitro and in vivo study. J Orthop Res 15: 331–341, 1997 11. Larsen E: Experimental instability of the ankle: A radiographic investigation. Clin Orthop 204: 193–200, 1986 12. Lindstrand A, Mortensson W: Anterior instability in the ankle joint following acute lateral sprain. Acta Radiologic Diagn 18: 529 –539, 1977 13. Rasmussen O: Stability of the ankle joint: Analysis of the function and traumatology of the ankle ligaments. Acta Orthop Scand Suppl 221: 1–75, 1985 14. Rasmussen O, Tovborg-Jensen I: Anterolateral rotational instability in the ankle joint: An experimental study of anterolateral rotational instability, talar tilt, and anterior drawer sign in relation to injuries to the lateral ligaments. Acta Orthop Scand 52: 99 –102, 1981 15. Ryan JB, Hopkinson WJ, Wheeler JH, et al: Office management of the acute ankle sprain. Clin Sports Med 8: 477– 495, 1989 16. Seligson D, Gassman J, Pope M: Ankle instability: Evaluation of the lateral ligament. Am J Sports Med 8: 39 – 42, 1980 17. Taga I, Shino K, Inoue M, et al: In vivo measurement of instability of the ankle. Trans Orthop Res Soc 17: 470, 1992 18. Tohyama H, Beynnon BD, Renstrom PA, et al: Biomechanical analysis of the ankle anterior drawer test for anterior talofibular ligament injuries. J Orthop Res 13: 609 – 614, 1995
