Arthroscopic Findings in Patients with Chronic Ankle Instability

Transcription

1 /102/ $02.00/0 THE AMERICAN JOURNAL OF SPORTS MEDICINE, Vol. 30, No American Orthopaedic Society for Sports Medicine Arthroscopic Findings in Patients with Chronic Ankle Instability Beat Hintermann,* MD, Andreas Boss, MD, and Dirk Schäfer, MD From the University of Basel, Basel, Switzerland ABSTRACT Background: There are little objective data on structural changes of the chronically unstable ankle. Such knowledge could help with preoperative planning. Hypothesis: Preoperative ankle arthroscopy provides important insights into the causes and mechanisms of ankle instability and the resulting disability. Study Design: Case series. Methods: From 1993 to 1999, arthroscopic examination was performed in the ankles of 148 patients with symptomatic chronic ankle instability that had lasted 6 months or more. All structural changes were recorded and compared with the clinical diagnosis. Results: A rupture or elongation of the anterior talofibular ligament was noted in 86% of ankles, of the calcaneofibular ligament in 64%, and of the deltoid ligament in 40%. Cartilage damage was noted in 66% of ankles with lateral ligament injuries, whereas 98% of the ankles with deltoid ligament injuries had cartilage damage. Although lateral instability could be verified arthroscopically in 127 patients, medial instability was presumed clinically in 38 patients but was actually detected in 54 patients arthroscopically. Conclusion: Preoperative ankle arthroscopy revealed an essential amount of information that would otherwise have been undetected. For instance, the ligaments showed typical abnormalities corresponding to different entities of ankle instability and different intraarticular pathologic conditions. Ankle ligament injuries are the most common injuries that occur in sports and recreational activities 11 and account for about 25% of the injuries that occur in running and jumping sports. 21 Sprains constitute 75% of all ankle * Address correspondence and reprint requests to Beat Hintermann, MD, University of Basel, Clinic of Orthopaedic Surgery, Kantonsspital CH-4031 Basel, Switzerland. No author or related institution has received any financial benefit from research in this study. injuries, 11,14 and 85% of these sprains are caused by an inversion trauma. 3 Although most of these ankle ligament injuries can be treated successfully with physical rehabilitation and nonoperative treatment, 20% to 40% of patients with these injuries go on to experience chronic instability and subsequent disability. 4,9,16 Many of these patients can be treated satisfactorily with late repair or reconstruction of the lateral ligaments. 26 Mechanical instability, deficiency of proprioception, and weakness of the peroneal muscles are thought to contribute to subsequent chronic disability. 10 However, the mechanisms that lead to these complaints are still poorly understood. 25 Research has focused mainly on the symptoms of instability confirmed by stress radiographs and the surgical observation of lateral ankle disruption. There have been few reports in which investigators have focused on ankle abnormalities seen during arthroscopic examination and correlated them with clinical symptoms and diagnosis. 22,24 This is especially true for the assessment of intraarticular lesions after repetitive ankle sprain. Taga et al. 27 found cartilage lesions in 89% of freshly injured ankles (8 of 9) and 95% of ankles with chronic injuries (21 of 22). On the basis of these findings, they concluded that the longer the time elapsed from the initial injury, the more severe the associated cartilage lesions became. They also hypothesized that these cartilage lesions are the primary cause of persistent pain in the unstable ankle. Komenda and Ferkel, 18 in contrast, found only a 25% prevalence of chondral injuries in 55 unstable ankles. Although much is known about the kinematic changes and clinical presentation of lateral ankle instability, very little objective data are available regarding the structural changes of the unstable ankle, especially for the medial ankle ligaments. Therefore, we designed an exploratory, prospective study to evaluate the arthroscopic findings of chronically unstable ankles to provide insights into the causes and mechanisms of ankle instability and the resulting disability. 402

2 Vol. 30, No. 3, 2002 Arthroscopic Findings in Patients with Chronic Ankle Instability 403 MATERIALS AND METHODS Clinical Material Of the 523 arthroscopic procedures performed on ankles between January 1993 and July 1999 at our institution, 148 were performed as a first diagnostic step during surgical reconstruction of the ankle ligaments. All of these patients had a diagnosis of symptomatic chronic ankle instability that had persisted for at least 6 months. There were 88 men and 60 women with a mean age of 34.4 years (range, 15 to 57). Distribution of right (80, 54%) and left (68, 46%) ankles was unequal. The mean time from the initial sprain was 22.2 months (range, 15 to 60) and from the last sprain, 12.1 months (range, 6 to 32). Ninety-four ankle sprains (64%) occurred during sporting events. The other cases involved work-related injuries (27, 18%), injuries in the home (24, 16%), and injuries that occurred in traffic accidents (3, 2%). None of these patients had undergone prior surgery. All patients were continuing to have pain and instability despite initial use of an orthotic and a rehabilitation program for a mean duration of 4.9 months (range, 3 to 12). The preoperative diagnosis was made on the basis of the history and the results of a physical examination, including special maneuvers, and plain radiographs. While the patient was standing, the form and position of both feet were inspected for potential malalignment, deformity, asymmetry, or swelling. A 14-point examination was used to assess potential tenderness and pain of the ankle ligaments (anterior talofibular ligament, calcaneofibular ligament, anterior inferior tibiofibular ligament, bifurcate ligament, talonavicular ligament, spring ligament, tibionavicular ligament, and the deep portion of the deltoid ligament), the ankle joint (sinus tarsi, the anterior border of the fibula, tibia, and medial malleolus), and tendons (posterior tibial tendon, peroneal tendon). A clinical stress investigation was then performed. While the patient was seated on a table with his or her feet hanging, the examiner held the heel with one hand and the tibia with the other hand. First, a varus and then a valgus tilt stress was applied to the heel, and the result was compared with the result of the same test on the contralateral side. Next, anterior drawer stress was applied, and again the result was compared with that of the contralateral side. Plain radiography was used to exclude pathologic conditions of bone. When a talocalcaneal coalition or bony fragmentation that involved the articular surfaces was suspected, CT was performed. Stress radiographs, MRI, and CT investigation were not performed routinely. Stress radiographs were obtained in 58 ankles (39%), MRI scans in 32 ankles (22%), and CT investigation in 6 ankles (4%). A history of chronic instability, manifested by recurrent inversion injuries with pain, tenderness, and sometimes bruising over the lateral ligaments, was considered an indication of lateral instability of the ankle. Medial instability was suspected on the basis of the patient s sensation of giving way, especially toward the medial side, when walking on even ground, down hill, or down stairs; pain at the anteromedial aspect of the ankle; and sometimes pain on the lateral ankle, especially during dorsiflexion of the foot. When the symptoms and findings were present on both the medial and lateral sides, they were considered to indicate rotational instability of the talus in the ankle mortise. The diagnosis of anterior impingement syndrome was based on a history of chronic ankle pain aggravated by dorsiflexion movement of the foot or internal rotation of the tibia (single-legged squat test). 8 On physical examination, findings included palpable tenderness, primarily along the lateral aspect of the ankle joint but frequently involving the entire anterior ankle joint. The diagnosis of medial impingement syndrome was made when a similar pain was noted along the anterior gutter of the medial malleolus. Operative Technique The arthroscopic procedure was performed as a measure of preoperative evaluation and planning immediately before the surgical stabilization of the ankle. The arthroscopic procedure was performed in all patients by the same surgeons, including the authors and one other surgeon experienced in arthroscopy. Four arthroscopies (3%) were performed with the patient under general anesthesia, and 144 (97%) were performed with the patient under regional anesthesia. The patient was placed in a supine position with a tourniquet around the upper thigh. A leg holder applied to the thigh was used to hold the knee in a flexion position of 90 to 100 to allow for investigation of the foot in a quasi-hanging position. The ankle joint was inflated with physiologic saline solution. After incision of the skin from a central approach (between the anterior tibial and extensor hallucis longus tendons), the capsule was distended bluntly to avoid damage to the neurovascular structures. Then, the 5-mm 30 standard arthroscope was introduced into the ankle joint through the prepared anterior portal. The liquid was evacuated and the cavum was filled with carbon dioxide gas. No traction device and no tourniquet were used during the arthroscopic procedure. Enough distension of the ankle was normally achieved by the hanging position of the foot and the intraarticular gas pressure; if not, additional distension was achieved by manual traction on the heel. A 2-mm hook was inserted into the joint through an additional anteromedial portal. A systematic arthroscopic examination was performed to visualize the internal structures by using a 10-point examination for the anterior ankle (deltoid ligament, medial gutter, medial talus, anterocentral talus, lateral talus, talofibular articulation, lateral gutter, anterior inferior tibiofibular ligament, anterior talofibular ligament, and calcaneofibular ligament) and a 5-point examination for the central and posterior ankle (mediocentric talus, medial tibial talus, lateral tibial talus, posteroinferior tibiofibular ligament, and transverse tibiofibular ligament). In some ankles, an elevator was inserted through the existing anteromedial or an additional anterolateral portal to visualize the central and posterior structures. Articular cartilage lesions were graded according to the

3 404 Hintermann et al. American Journal of Sports Medicine depth of the lesion, as assessed by inspection and probing: grade 1, superficial lesion; grade 2, fissuring or degeneration of less than one-half the thickness of the articular cartilage; grade 3, fasciculation or degeneration of more than one-half the thickness of the articular cartilage; and grade 4, erosion of the cartilage down to the subchondral bone. Ligament lesions were graded as distended if the ligament was thinned or elongated or both and as ruptured if the continuity was lost. Most ligament tears were located at the proximal insertion; therefore, they were best identified by a completely free insertion area of the ligament on the fibula (Fig. 1) or the medial malleolus (Fig. 2). Stretching or tearing of the calcaneofibular ligament was difficult to appreciate arthroscopically from the anterior view because the anterior talofibular ligament and the capsular structures obstructed the view. Thus, tearing of the calcaneofibular ligament could only be detected when the anterior tibiofibular ligament was ruptured (Fig. 1). Lateral instability was considered to be present when talar tilting occurred by supination stress of the foot (Fig. 3). If as the foot was everted or pronated the deltoid ligament was not tensioned, thus not creating a strong medial buttress of the ankle, the ligament was considered incompetent (Fig. 4). An excessive lifting away of the talus from the medial malleolus by pulling the foot anteriorly was also considered an indicator of incompetence of the deltoid ligament. After visual evaluation and probing of the ligaments, lateral and medial ligament stability was tested by applying varus, valgus, and anterior pull stress to the ankle Figure 2. Anterior view of the medial malleolus (M) showing a completely free insertion area of the ligament (*). The deltoid ligament (DELT) is attenuated, allowing a view into the posteromedial aspect of the ankle. TA, talus. Figure 3. Lateral tilt of the talus (TA) during inversion-supination stress. There is some posterior dislocation of the fibula (F) with respect to the tibia (TI). Figure 1. Anterior view of the lateral malleolus showing a completely free insertion area of the ligament (*) on the fibula (F). The anterior talofibular ligament (ATFL) is ruptured, and there is a complete avulsion of the calcaneofibular ligament (CFL) from the fibula that allows a view of the peroneal tendons (Per) in the ruptured tendon sheath. The posterior talofibular ligament (PTFL) is intact. TA, talus. joint under arthroscopic control. The lateral ankle joint was graded as follows: Stable: Some translocation of the talus but not enough to open the tibiotalar joint by more than 2 mm, as measured by the 2-mm hook, and not enough to introduce the 5-mm arthroscope into the lateral tibiotalar space.

4 Vol. 30, No. 3, 2002 Arthroscopic Findings in Patients with Chronic Ankle Instability 405 Figure 4. Anterior view into the medial ankle as the foot is everted/pronated. The deltoid ligament (DELT) is tensioned, but obviously no strong medial buttress is created with this maneuver. M, medial malleolus ; TA, talus. Figure 5. Central view into the anterior ankle showing an osteophytosis along the anterior tibia (TI) with hypertrophic synovial thickening (S). TA, talus. Moderately Unstable: The talus moved to some extent out of the ankle mortise, allowing the introduction of the 5-mm arthroscope into the lateral tibiotalar space, but not enough to open the tibiotalar joint by more than the necessary 5 mm. Typically, there was no free view into the posterior aspect of the ankle joint. Severely Unstable: The talus moved easily out of the ankle mortise, typically allowing a clear view into the posterior aspect of the ankle joint without significant pulling stress on the heel. The medial ankle joint was graded as follows: Stable: Some translocation of the talus but not enough to open the medial tibiotalar joint by more than 2 mm, as measured by the 2-mm hook, and not enough to introduce the 5-mm arthroscope into the medial tibiotalar space. Moderately Unstable: The talus moved to some extent out of the ankle mortise, allowing introduction of the 5-mm arthroscope into the medial tibiotalar space, but not enough to open the tibiotalar joint by more than the necessary 5 mm. Typically, there was a free view from the tibiotalar space of half the surface of the medial malleolus but not enough to visualize the posteromedial border of the tibia. Severely Unstable: The talus moved easily out of the ankle mortise, typically allowing for a free view from the tibiotalar space of the whole medial malleolus and visualization of the posteromedial border of the tibia. The diagnosis of impingement was confirmed arthroscopically by the presence of an osteophyte along the anterior tibia with hypertrophic synovial thickening or scar tissue or both (Fig. 5). The important dates from the history, the preoperative clinical and radiological assessment, and the arthroscopic findings were systematically recorded. Additionally, video and photo documentation was routinely performed. RESULTS A history of chronic ankle instability, manifested by recurrent injuries with pain, tenderness, and sometimes bruising over the lateral or medial ligaments was found in all 148 patients. Between the injuries, 102 ankles (69%) were asymptomatic, whereas 46 patients (31%) had chronic pain, tenderness, swelling, or induration, causing them great difficulties in sports and daily activities. Eighty-eight patients (59%) had daily giving way, 40 (27%) had monthly episodes of instability, and 20 (14%) reported weakness. Sixty-five patients (44%) had pain at rest and 38 (26%) continually used analgesics for chronic pain. Ninety-two patients (62%) reported pain and instability during walking, and 130 (88%) experienced pain and instability during sports. Thirty-eight patients (26%) had more instability than symptoms of pain. All of the patients had pain to an appreciable degree. Eighty patients (54%) stated that both instability and pain conditions were equally disabling. On physical examination, 26 patients (18%) had isolated tenderness in the region of the anterior talofibular ligament (lateral gutter), and 16 patients (11%) had isolated tenderness on the anterior border of the medial malleolus (medial gutter). Fifty-seven patients (39%) had tenderness on both the lateral and the medial side of the ankle, and 45 other patients (30%) had tenderness in multiple areas. Four patients (3%) had no tenderness, and 15 patients (10%) had tenderness along the posterior tibial tendon. Of the 11 patients (7%) who had tenderness along the pero-

5 406 Hintermann et al. American Journal of Sports Medicine TABLE 1 Findings of Ankle Arthroscopy (N 148) Findings No. % Synovitis Ventral scarring 7 5 Synovial plica Anterior talofibular ligament Elongation Rupture a Calcaneofibular ligament Elongation Rupture a Deltoid ligament Elongation Rupture 13 9 Syndesmosis Elongation 11 7 Rupture 2 2 Cartilage lesions, talus Grade Grade Grade Grade Cartilage lesions, tibia Grade Grade Grade Grade a Including bony avulsion. neal tendon, some instability of the peroneal tendon was found in 7 cases. The arthroscopic findings are summarized in Table 1. There were 42 cases (28%) in which the calcaneofibular ligament was not visible, and 4 ankles (3%) in which the anterior talofibular ligament was not visible. A combined lesion of the anterior talofibular and the calcaneofibular ligament was found in 95 ankles (64%) (Table 2). A lesion of the deltoid ligament, found in 59 ankles (40%), was always associated with a lateral ligament injury that included in most cases both the anterior talofibular and the calcaneofibular ligaments (Table 3). Cartilage lesions of the talus were found in 81 ankles (55%). The cartilage lesions were noted to be isolated on the talus in 68 ankles (47%) and isolated on the tibia in 4 ankles (3%); whereas in 9 ankles (6%) they were noted on both the talus and tibia (Table 4). Although the complete lateral ligament injuries were nearly evenly distributed between ankle joints with and without cartilage damage (49 compared with 46 ankle joints), all complete tears of the deltoid ligament were associated with damage of the TABLE 3 Lateral Ligament Lesions in the Presence of Deltoid Ligament Lesions Deltoid ligament lesion talar cartilage (Table 5). No correlation was found between the severity of cartilage lesions and the duration of the instability syndrome. In Table 6 we compare the preoperative diagnosis with the arthroscopic findings. Forty-five ankles (30%) were diagnosed preoperatively as having impingement symptoms. This diagnosis was confirmed in 43 ankles (29%). Of these, 18 ankles (12%) were noted to have osteophytes of the tibia, and 25 ankles (17%) were noted to have hypertrophic synovial thickening. Both osteophytes and hypertrophic synovial thickening were located more on the lateral side when lateral instability was predominant and more on the medial side when medial instability was predominant. Although lateral instability could be verified arthroscopically in all 127 cases with clinical diagnosis (86%), medial instability was presumed clinically in 38 patients (26%) but was actually detected in 54 patients (36%) arthroscopically. Eighteen patients (12%) were thought to have rotational instability of the ankle preoperatively; of these, all 18 were confirmed as having rotational instability, but 20 other patients were found to have rotational instability during the arthroscopic examination. DISCUSSION Anterior talofibular ligament Calcaneofibular ligament Elongation deltoid ligament (N 46) Intact 1 Elongation Rupture Inconclusive 1 Rupture deltoid ligament (N 13) Intact Elongation 6 9 Rupture 7 4 Inconclusive An arthroscopic procedure was used in this prospective study of patients with recurrent ankle sprains to assess the presence of intraarticular lesions that might cause chronic pain, disability, and instability. More anatomic Anterior talofibular ligament TABLE 2 Ligament Lesions of the Lateral Complex Calcaneofibular ligament Intact Elongation Rupture Avulsion a Inconclusive Intact 7 Elongation Rupture Avulsion a 1 2 Inconclusive 4 a Bony avulsion (osteoligamentous injury).

6 Vol. 30, No. 3, 2002 Arthroscopic Findings in Patients with Chronic Ankle Instability 407 TABLE 4 Cartilage Lesions of the Talus Location Grade 1 Grade 2 Grade 3 Grade 4 Total N (%) Medial (62) Central (4) Lateral (17) Ventral (16) Complete talus (1) Total (100) TABLE 5 Association of Ligament Lesions with Cartilage Damage of the Talus Ligament injury N Grade 0 Grade 1 Grade 2 Grade 3 Grade 4 Anterior talofibular ligament Elongation Rupture Calcaneofibular ligament Elongation Rupture Deltoid ligament Elongation Rupture TABLE 6 Preoperative Versus Postoperative Diagnosis (N 148) Diagnosis Preoperative Postoperative Ventral impingement Synovialitis 2 47 Lateral instability Medial instability Rotational instability Ruptured syndesmosis 4 2 Cartilage lesion Talus 6 78 Tibial pilon 0 13 Medial malleolus 0 17 Lateral malleolus 0 4 Corpus liberum 2 5 Osteochondritis dissecans 4 5 Arthrosis 3 2 abnormalities and structural changes were found than we expected, including lesions of the cartilage and the lateral and medial ligaments. These findings corresponded well with the complexity and variety of clinical findings and support our belief that there are various entities of chronic ankle instability. The incidence of degenerative arthritis after chronic lateral instability of the ankle has been reported to be from 13% 20 to 78%. 13 One explanation of the cause of degenerative arthritis may be possible cartilage lesions caused by the repetitive sprain injuries. The overall incidence of talar cartilage lesions found in this study (55%) indicates that cartilage damage is common in the chronically unstable ankle joint. We found 62% of the cartilage lesions in the medial part of the talus and only 17% in the lateral aspect of the joint (Table 4). These results may be explained by the observations made by Noguchi. 23 In his three-dimensional model of the human ankle joint, he was able to show that an increase of stress distribution on the medial side of the ankle joint occurred when the lateral ligaments were released. Harrington, 13 on the other hand, suggested unbalanced loading of the medial joint space to be the primary cause for the development of degenerative arthritis. In an arthroscopic study of 22 chronically unstable ankle joints, Taga et al. 27 found an incidence of cartilage damage of 95%. The severity and extent of cartilage lesions increased with the duration of symptoms but did not correlate with the number of ligaments involved. The authors concluded that even single ligament lesions should be treated to prevent further cartilage damage. However, this conclusion was not supported by the findings of the present study. We showed no correlation between the severity and extent of cartilage lesions and the duration of ankle instability, but we did find an increased incidence of cartilage lesions in the presence of deltoid ligament rupture. The conclusions of Taga et al. were also not supported by the findings of Löfvenberg et al., 20 who evaluated 37 patients with chronic ankle instability 20 years after the diagnosis had been made. Only six of the patients (16%) developed degenerative changes, and the authors thus recommended primarily nonoperative treatment. When complete ligament ruptures were correlated with cartilage damage, there was a nearly even distribution of intact and altered cartilage in the presence of isolated or combined rupture of the lateral ligaments (Table 5). It is not clear why the degree of lateral ligament injury does not correlate with the degree of cartilage damage. Taga et al. 27 also found no correlation between cartilage damage and the degree of instability in patients in their arthroscopic study. They hypothesized that even minimal talar displacement can result in medial stress concentration in the tibiotalar joint and lead to cartilage damage. Such an increase of medial stress concentration could also be explained by the results of the in vitro study of Athanasiou

7 408 Hintermann et al. American Journal of Sports Medicine et al., 2 who studied 14 human cadaveric ankles and found the anterior and posterior regions of the medial side of the tibia to be 18% to 37% stiffer than the anatomically corresponding sites in the talus. In addition, they found the softest cartilage tissue to be in the posterolateral and medial regions of the talus. This disparity of mechanical properties between the articulating surfaces of the tibial and talar regions could, in fact, explain the occurrence of cartilage lesions in a repetitive overuse process in the ankle joint. This disparity could also explain the findings of Van Dijk et al., 28 who studied 30 consecutive patients who underwent repair of an acute rupture of the lateral ankle ligaments. They found a higher incidence of macroscopic cartilage damage, medially located pressure pain, and medially located complaints at the 1-year follow-up in those patients who had sustained a high-velocity injury (a faulty landing during jumping or running) than in those who had sustained a low-velocity injury (a stumble). The question of whether other factors may play a certain role in the development of cartilage lesions remains open, however. Such factors may include body weight, sex, age, muscular imbalance, malalignment of the hindfoot, or other variations of the individual anatomy of the anklejoint complex. 3 In the present study, the injury pattern in the lateral ligaments was mostly a combined rupture of the anterior talofibular ligament and the calcaneofibular ligament (69%). This percentage is higher than the usually reported 20% incidence of combined injuries compared with 60% to 70% isolated anterior tibiofibular ligament injuries. 17 The higher percentage may be due to the fact that our study included a substantial proportion of patients who had been referred from other orthopaedic surgeons and insurance companies after unsatisfactory outcome of treatment. Although the diagnosis of lateral instability was confirmed arthroscopically in all 127 patients whose condition was diagnosed clinically, the presence of medial instability was generally underestimated (Table 6). In 59 ankles (40%), a significant rupture of the deltoid ligament was noted (Table 5). The clinical relevance of such medial ligament insufficiency is not known exactly. Deltoid ligament ruptures associated with acute fibular fractures were reported in 28 patients in whom only the fibular fracture was surgically treated. 29 Eighteen months postoperatively, there was no sign of medial laxity either clinically or on eversion stress radiographs, and it was concluded that anatomic reconstruction of the medial malleolus allows for nonoperative treatment of a concomitant rupture of the deltoid ligament. Harper, 12 too, saw no evidence of the need for repair of the deltoid ligament in surgically treated ankle injuries, based on experience with 42 cases. In the present study, however, all ankles with rupture of the deltoid ligament also had lateral ligament injuries, mostly of two ligaments, indicating that these cases represented severe instability (Fig. 1). This diagnosis was supported by the clinical history of these patients; 15 were initially treated for painful and disabling tendinitis of the posterior tibial tendon and 6 for tarsal tunnel syndrome. According to the in vitro findings of Cass and Settles 5 and Hintermann et al., 15 this situation could correspond to rotational instability of the ankle and, in turn, could explain the high correlation between deltoid ligament injuries and cartilage damage of the medial talus. In contrast to the technique used by others, 18,27,28 we performed ankle arthroscopy without an external distraction device, which allowed us to recognize different instability patterns of the ankle joint. The application of invasive and noninvasive distraction devices may indeed improve the visualization of the joint, but it definitely hinders the functional investigation of the joint. In addition, the use of a distraction device is not without complications. 6,24 It has been reported that forces up to 135 N are associated with ligament damage, and manual distraction is as effective as external distraction. 1 Although the medial and the lateral ligament complex as well as the tibial and talar cartilage were visible in most cases, there were some exceptions. In 4 patients the anterior talofibular ligament was not clearly visible, and in 42 patients the calcaneofibular ligament was not clearly visible. The central portal, as used in the present study, allowed for good visualization of the whole medial and lateral ankle joint without changing the portal. Blunt dissection of the subcutaneous tissue minimized the risk of damage to the neurovascular structures, and the only complication we observed was additional damage to the talar cartilage in one patient, caused by the arthroscope. Ankle arthroscopy was shown to be effective for identifying impingement syndrome, ligament injuries, and cartilage lesions, and for assessing the volume and relative laxity of the capsule. As well as increasing our knowledge in correlating morphologic with functional findings, arthroscopic examination provides specific and complete information that identifies the pathologic processes and internal structures of the unstable ankle. This knowledge is mandatory for the interpretation of adjunctive diagnostic tests, such as CT and high-quality MRI. These methods have produced considerable improvements in the evaluation of pathologic conditions of the cartilage, bone, and the capsular and ligament structures. However, they do not enable the surgeon to diagnose abnormalities of the joint capsule and its ligamentous thickenings, nor do they allow dynamic assessment of stability. Therefore, these tests have significant limitations and, when not carefully interpreted, may even mislead the physician to overinterpret certain findings. One may argue that stress radiographs should have been consistently obtained in all 148 patients. Because wide variations of up to 25 of talar tilt and differences from side to side of up to 19 have been found to be present in about 5% of the population, 7 radiologic diagnosis of lateral instability is thought to be highly unreliable. This variation becomes even more evident, as it has been shown that only 40% of the patients demonstrating radiologic instability will have symptoms of an unstable ankle. 9 Approximately the same percentage of patients with symptomatic ankle instability will be shown to be stable on stress radiographs. 19 Another concern regarding the study design may be that no control group without complaints and symptoms of instability was used to contrast with the patients with

8 Vol. 30, No. 3, 2002 Arthroscopic Findings in Patients with Chronic Ankle Instability 409 pathologic findings enrolled in this study. Performance of an arthroscopic examination in a healthy patient or on the healthy contralateral ankle would probably help to better discern the pathologic processes. However, from an ethical standpoint, it would probably not be possible. What was reported here was strictly descriptive, based on the authors wide experience with ankle arthroscopy under various conditions. As long as no noninvasive diagnostic tools are available to show the condition of ligaments in more detail, it is extremely difficult to provide other evidence of how a ligament lesion is seen under arthroscopy. Magnetic resonance imaging has not been shown to be as reliable as arthroscopy in evaluating ankle ligaments. Perhaps improved imaging techniques may help to increase such information in the near future. At this moment, however, we must continue to collect all the information we can get from visualization of pathologic conditions through arthroscopy. This study provides new data about structural changes in the unstable ankle and provides a new rationale for understanding the pathologic processes in the ankle and the resulting disability with respect to diagnosis and treatment. CONCLUSIONS Abnormalities of different structures were found to be involved in chronic ankle instability, and there was no single causal entity. This was especially true for the lateral and medial ligaments. Clearly, the degree of severity of lateral ligament lesions was not correlated with cartilage lesions of the talus, whereas medial ligament lesions were associated with cartilage damage of the talus. The long-term outcome of these cartilage lesions remains unknown, which emphasizes the need for accurate diagnosis and treatment of acute ankle ligament injuries to prevent secondary problems such as chronic instability and cartilage damage. Preoperative arthroscopy can therefore give essential information about the status of the chronically unstable ankle joint with regard to the choice of surgical treatment. ACKNOWLEDGMENTS The authors thank Prof. André Gächter and Dr. Christoph Lampert of the Orthopaedic Clinic, Kantonsspital, St. Gallen, Switzerland, and Dr. Jiri Skarvan, Basel, Switzerland, for supporting this study and for their help in data collection. REFERENCES 1. Albert J, Reiman P, Njus G, et al: Ligament strain and ankle joint opening during ankle distraction. Arthroscopy 8: , Athanasiou KA, Niederauer GG, Schenck RC Jr: Biomechanical topography of human ankle cartilage. 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