PATHOLOGY OF ACUTE COMPLETE ACROMIOCLAVICULAR DISLOCATION: WHAT IS GRADE THREE INJURY?

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1 PATHOLOGY OF ACUTE COMPLETE ACROMIOCLAVICULAR DISLOCATION: WHAT IS GRADE THREE INJURY? Fumio Kato, Hiromichi Hayashi, Kuninari Ito, Naoki Nakakoshi, Toyohiko Shoji, Miki Iwasaki* and Soichiro Tsukamoto* Tokyo Metropolitan Police Hospital and *Showa General Hospital, Tokyo, Japan Pathological changes of the anatomical structures were carefully observed and recorded during operative repair in 70 patients with acute complete acromioclavicular dislocation. We found that the coracoclavicular ligament was intact or only partially torn in 25% of the patients. We suggest that the radiological Grades and the pathological Stages are considered separately. 1. INTRODUCTION It is our custom to classify acromioclavicular injuries into three Grades according to Tossy or Allman. They defined Grade 3 injury as complete dislocation, and presumed that the coracoclavicular ligament was completely torn. But how true is their statement? When we performed open reduction for Grade 3 injuries, we sometimes found that the coracoclavicular ligament was intact or only partially torn. An example is shown in Figure 1. This patient showed complete dislocation of the acro- Fig.l. A case of Grade 3 injury with intact coracoclavicular ligament mioclavicular joint in radiological as well as clinical findings. However, when we did open reduction and examined the anatomical structures, we found that both the trapezoid and the conoid ligament were intact, only the acromioclavicular ligament being torn. 52

2 We thought it was necessary to clarify the meaning of Grade 3 injury by studying meticulously the intra-operative findings. 2. MATERIALS AND METHODS In the past 15 years, we have treated 185 patients with acute Grade 3 injury of the acromioclavicular joint. The diagnostic criteria for the Grade 3 injury were those of Allman. On the radiograph made with the stress of three kilograms, the distal end of the clavicle was above the superior surface of the acromion, and the distance between the clavicle and the coracoid process was increased. The degree of displacement of the distal end of the clavicle was expressed in percentage as shown in Figure 2. If the inferior surface of the distal end of the clavicle was in line with the superior surface of the acromion, the displacement was 100% of the thickness of the joint (or the thickness of the articular end of the acromion, when there was difference in the thickness of both articular ends). Fig.2. Degree of displacement of the distal end of the clavicle The methods of treatment were open reduction (modified Phemister technique) in 102 patients, closed reduction and percutaneous pinning in 41 patients, and conservative methods in 42 patients. In 70 of the 102 patients who underwent open reduction, the pathological changes of the anatomical structures were carefully observed during operation and recorded. These 70 cases made up the basis of this study. 3. RESULTS We classified the pathological changes into four stages (Figure 3). In Stage I, no ligament was torn. In Stage II, only the acromioclavicular ligament was torn. In Stage III, the acromioclavicular ligament and the trapezoid ligament were torn. In Stage IV, the acromioclavicular ligament, the trapezoid ligament, and the conoid ligament were all torn. 53

3 In the 70 patients studied, there were no Stage I, three Stage II, 15 Stage III, and 52 Stage IV pathological changes. This means that, in 18 out of 70, or 25% of the patients, the coracoclavicular ligament was intact or only partially torn. The degree of displacement of each case was plotted on the graph which was divided by pathological Stages (Figure 4). In the group of Stage II, all three cases showed displacement of 100%. In the group of Stage III, the average of displacement was 111%. In Stage IV, the average was 134%. 54

4 We looked at the pathological changes from the severity of displacement (Figure 5). Seven cases with displacement of 200% or more were all in Stage IV. In the group of nine cases with displacement of 150% to 199%, seven cases (78%) were in Stage IV. In 55 patients with displacement of 100 to 150%, 39 patients (71%) were in Stage IV. Thus, the severer the degree of displacement is, the higher the possibility of Stage IV changes can be. 4. DISCUSSION From our findings, we can correlate the pathological changes with the radiological classification as shown in Figure 6. Fig.6. Correlation between radiological grades and pathological stages Grade 3 radiological changes mainly correspond to Stage III and Stage IV pathological changes, but a small part of Grade 3 represents Stage II. It might be possible to add Grade 4 to the radiological classification. Then, 55

5 Grade 4, with displacement of 200% or more, would indicate that both the trapezoid and the conoid ligament are surely torn. Though not included in the present study, we operated on several cases of Grade 2 radiological changes. We found Stage III pathological changes in some cases, and Stage IV changes in one. Thus, the radiological classification of Tossy or Allman does not reflect the pathological changes to the satisfactory level of reliance. We should consider the radiological Grades and the pathological Stages as separate categories. What is the implication of this statement in clinical practice? There is no doubt that the diagnosis of complete dislocation of the acromioclavicular joint primarily depends on radiographs. However, if we can anticipate the pathological changes more accurately before treatment is begun, we would be better prepared for planning the proper method of treatment, whether conservative or operative. 5. CONCLUSION The classifications of Tossy and Allman are oversimplified and misleading. In 25% of Grade 3 injuries, the coracoclavicular ligament was intact or only partially torn. The radiological classification and the pathological stages should be considered separately. REFERENCES 1. Allman LA: Fractures and ligamentous injuries of the clavicle and its articulation. J Bone Joint Surg 1967; 49A: Kato F, et al: Treatment of acute complete dislocation of the acromioclavicular joint, in Surgery of the Shoulder, B.C. Decker, 1984, pp Tossy JD, et al: Acromioclavicular separations: Useful and practical classification for treatment. Clin Orthop 1963; 28: Urist MR: The treatment of dislocation of the acromioclavicular joint. Am J Surg 1959; 98: