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RADIOGRAPHIC ANALYSIS OF BONE DEFECTS
IN CHRONIC ANTERIOR SHOULDER INSTABILITY
T.BRADLEY EDWARDS †, AZIZ BOULAHIA‡, GILLES WALCH‡
† Minneapolis Sports Medicine Center
‡ Department of Orthopaedic Surgery, Clinique Sainte Anne Lumière Lyon.
Abstract
Purpose: The purpose of this study is to describe the incidence of bony lesions accompanying chronic anterior shoulder instability using fluoroscopically controlled radiography. Type of Study: This study represents a case series of radiographic findings of patients with chronic anterior shoulder instability. Methods: Radiographs of 160 shoulders in 156 patients with recurrent anterior shoulder instability were retrospectively evaluated. One hundred thirty-two shoulders had experienced recurrent dislocations, eighteen shoulders had experienced recurrent subluxations, and ten shoulders had evidence of anterior instability at arthroscopy despite no reported instability history. Fluoroscopically controlled radiographic views included an anterior posterior view with the humeral head in three rotations and a glenoid profile view with a comparison view of the contralateral shoulder. Results: A humeral impaction fracture was identified on the anterior posterior radiographs in 117 of 160 shoulders (17.1%). The glenoid profile view demonstrated an osseous lesion of the glenoid in 126 of 160 shoulders (78.8%). The anterior posterior radiograph demonstrated an osseous lesion of the glenoid in an additional 13 shoulders (8.2%). Overall, an osseous lesion, either humeral or glenoid, was identified in 152 of 160 shoulders (95.0%). Conclusions: This study demonstrates the frequent presence of bony lesions in patients with anterior shoulder instability. Key Words: Shoulder – Instability – Radiography – Bony lesions.
Introduction
Historically, the description of anatomic lesions of the glenoid associated with chronic anterior instability of the shoulder initiated in 1890 with the work of Broca and Hartmann.1 Lesions involving the capsuloligamentous structures were of primary interest to these early investigators, with osseous lesions of the glenoid not receiving attention until some years later. The classification of anterior shoulder instability evolved as these instability lesions became better understood. As the view of anterior shoulder instability has changed into a concept that involves a spectrum of clinical situations, classification has increased exponentially in complexity. Shoulder instability has been classified clinically based on direction, frequency, degree, and etiology, making analysis of this diagnosis particularly difficult.2
In an effort to simplify the description of anterior shoulder instability, Walch and Molé described a classification system composed of three categories.3 In this system, anterior instability is described as a previously dislocated shoulder (complete loss of contact between the articular surfaces requiring a reduction maneuver by the patient or a third party), a previous subluxated shoulder (partial or transitory loss of contact between the articular surfaces not requiring a reduction maneuver), or a shoulder that is chronically painful (at least six months duration) in abduction and external rotation without a defined history of dislocation or subluxation. Using this classification system, the purpose of this study was to radiographically analyze the osseous lesions in a series of patients with chronic anterior shoulder instability.
Methods
The charts of 246 consecutive patients that presented to our clinic with instability of the shoulder over a two year period ultimately undergoing surgical treatment were reviewed. All patients with instability occurring in any direction other than anterior were excluded. Patients with only one episode of instability or lack of chronic (greater than six months duration) symptoms or that had undergone a previous shoulder procedure were excluded. Additionally, patients that could not recall a traumatic episode initiating their shoulder problems and patients older than 40 years, because of the high incidence of rotator cuff pathology, were eliminated from this population. After enforcement of these exclusion criteria, 156 patients (160 shoulders) with isolated chronic anterior shoulder instability remained for review. All shoulders underwent an initial complete shoulder evaluation including examination for instability with anterior and posterior apprehension tests, anterior and posterior drawer tests, and anterior and posterior load and shift tests. All patients in this series ultimately underwent operative intervention for either recurrent shoulder instability or a chronically painful shoulder failing all nonoperative interventions. Operative findings in these patients allowed confirmation of an isolated diagnosis of chronic anterior shoulder instability. These findings included evidence of injury to the anterior inferior portion of the glenoid rim and or labrum with or without a posterior humeral head impaction fracture. The patients included 133 males and 23 females with an average age of 27.9 years (range, eighteen years to forty years). The dominant extremity was affected in ninety-nine of the shoulders.
For the purposes of analyzing results, all shoulders were classified according the previously described classification of Walch and Molé as dislocated, subluxated, or painful based on clinical history, physical examination, and findings at surgery. One hundred thirty-two shoulders (82.5%) were classified as dislocated. The average number of dislocations was six (range, three to twenty dislocations). Some of the shoulders in the dislocated group also reported episodes of subluxation between episodes of dislocation. Eighteen shoulders (11.2%) were classified as subluxated in which all patients described the symptoms of a dislocation, which always resolved spontaneously. Ten shoulders (6.3%) were classified as painful. This last group included shoulders with no elicitable history of dislocation or subluxation, but with findings on clinical examination suggestive of anterior shoulder instability, i.e. pain with the apprehension maneuver. All ten of these patients demonstrated findings at surgery, i.e. a soft tissue or bony avulsion of the inferior glenohumeral ligament, confirming the diagnosis of anterior shoulder instability. No statistical differences existed between the groups in gender, mean age, or arm dominance.
All patients had undergone radiographic examination upon presentation to our clinic including anterior posterior views with the humeral head in internal rotation, external rotation, and neutral rotation and a glenoid profile view with a contralateral comparison view as described by Bernageau.4 The Bernageau view provides a profile of the glenoid by placing the arm in the air and directing the x-ray beam 20° to 30° to the horizontal (Figure 1). This technique yields an image of the glenoid containing the sharp outline of a triangle anteriorly that is very important in interpretation (Figure 2). All radiography was performed under fluoroscopic control to ensure reproducibility and matched contralateral views.
An experienced observer blinded to the patient’s clinical history, physical examination, and intraoperative findings retrospectively reviewed all radiographs. The anterior posterior radiographs with humeral head in three rotations were observed for presence of a humeral head impaction fracture as described by Malgaigne and Hill and Sachs (Figure 3).5,6 Additionally, any fracture of the glenoid rim was recorded (Figure 4).
The Bernageau glenoid profile view of the affected shoulder with the contralateral comparison view was reviewed specifically for pathology of the glenoid. Disruption of the anterior osseous triangle as compared the contralateral control was classified into three groups. Fractures were defined as an abnormality of the anterior glenoid rim characterized by a visible osseous fracture fragment (Figure 5). The “cliff” sign was defined as a loss of the normal anterior triangle without a visible osseous fracture fragment (Figure 6). The “blunted angle” sign was defined as a rounding off of the normally sharp anterior angle of the triangle (Figure 7). Evaluation of the Bernageau glenoid profile view was always performed in the presence of the contralateral comparison view (required for determination of the “blunted angle” sign). This contralateral comparison was limited in the four patients with bilateral shoulder instability.
Results
Results of the evaluation of the anterior posterior radiographs in three rotations for each of the types of instability are summarized in Table I. Overall, we found 73.1% (117 of 160) incidence of humeral head impaction fractures. These lesions were most often present in the dislocation group (75.8%) and less frequent in the subluxation group (66.7%) and in the painful group (50.0%). In all cases in which a humeral head impaction fracture could be seen, it was visible on the internal rotation view. Inferior glenoid rim fractures were apparent on the anterior posterior radiograph in 45.6% (73 of 160) of all the cases. In all cases in which a glenoid rim fracture could be seen, it was visible on the internal rotation view. These lesions followed the same trend as the humeral head impaction fractures in that they were most often present in the dislocation group (64.0%) and less frequent in the subluxation group (38.9%) and in the painful group (20.0%).
Results of evaluation of the Bernageau glenoid profile view with contralateral comparison view are exhibited in Table II. Overall, we identified osseous abnormalities of the glenoid on the Bernageau glenoid profile view in 78.8% (126 of 160) of the shoulders, 41.3% (66 of 160) of which had a fracture, 13.1% (21 of 160) of which had a “cliff” sign, and 25.0% (40 of 160) of which had a “blunted angle” sign. The percentage of shoulders with these findings was fairly evenly distributed between dislocated shoulders and subluxated shoulders; the painful shoulders demonstrated a lower percentage of overall abnormalities, “cliff” signs, and “blunted angle” signs.
If the glenoid abnormalities found on the anterior posterior views and the Bernageau glenoid profile view are combined, 87.0% (139 of 160) of the shoulders in this series demonstrated an osseous abnormality of the glenoid, including 119 of 132 (90.2%) shoulders in the dislocated group, sixteen of eighteen shoulders in the subluxated group, and five of ten shoulders in the painful group. If osseous lesions of the humeral head and the glenoid are considered, 95.0% (152 of 160) of the shoulders in this series demonstrated an osseous lesion associated with anterior shoulder instability.
Discussion
The purpose of this study was to report the radiographic findings in traumatic chronic anterior shoulder instability. We did not report the clinical results of these patients, all of who were operatively treated, because of the heterogenous nature of the procedures employed. Additionally, operative results for many of these patients have been previously published.7,8
This study demonstrates that up to 95.0% of patients with traumatic chronic anterior shoulder instability have osseous lesions of the humeral head or anterior glenoid rim. Furthermore, the incidence of these lesions is variable depending on whether the patient has had prior dislocations, prior subluxations, or a painful shoulder with an associated instability lesion. To our knowledge, this radiographic review of 160 shoulders with recurrent anterior instability represents the largest series of its kind.
Humeral head impaction fractures as described by Malgaigne and reviewed by Hill and Sachs occur in as many as 90% of patients with anterior shoulder instability.5,6,9 These lesions are caused by impaction of the posterior superior aspect of the humeral head on the anterior inferior glenoid rim with anterior excursion of the humerus during an instability episode. Our reported incidence of 73.1% is consistent with many of the reports in the literature for anterior shoulder instability.10-14 We acknowledge that the use of additional radiographic views, i.e. the Stryker notch view or Garth view, would likely increase this incidence.9,15 Like a previous investigation by Pavlov and associates,16 this study demonstrates this incidence to be more common in shoulders with a prior dislocation than in shoulders with a prior subluxation, and more common in shoulders with a prior subluxation than painful shoulders with an instability lesion.
Perhaps the more interesting findings of this study relate to the osseous abnormalities demonstrated on the glenoid rim. Multiple investigators have described the traumatic disruption of the anterior aspect of the inferior glenohumeral ligament which is now commonly referred to as a “Bankart” lesion.1,17 This lesion can exist as a soft tissue injury or as a bony avulsion of the ligament.18,19 In addition to an avulsion fracture of the inferior glenohumeral ligament, bony abnormalities of the glenoid associated with anterior instability can be represented by a loss of anterior inferior glenoid bone probably related to resorption of an avulsion fracture fragment (“cliff” sign) or a rounding off of the anterior inferior glenoid bone caused by microimpaction fractures related to multiple dislocations or subluxations (“blunted angle” sign). These glenoid bony abnormalities have been reported to occur in 11% to 90% of cases of recurrent anterior shoulder instability.4,20-26 Our overall incidence of glenoid osseous lesions of 87.0% compares most closely with the results of Patte and Bernageau’s reported incidence of 90%.24 Like with the humeral head lesions, we found a similar trend in glenoid lesions based on the Walch and Molé instability classification; the dislocated shoulders exhibited the highest percentage of lesions, and the painful group demonstrated the lowest incidence of lesions.
The variability with which osseous lesions of the glenoid are reported in anterior shoulder instability is most likely related to the radiographic views employed. Using a glenoid profile view which has become known as the West Point view, Rokous and associates identified osseous abnormalities of the anterior inferior glenoid rim in fifty-three of sixty-three patients with a history of shoulder instability.25 Similarly, Patte and Bernageau identified osseous glenoid lesions in thirty-six of forty patients using a glenoid profile view originally described by Bernageau.24 In contrast, Trillat, without the benefit of a glenoid profile view, reported a 20% incidence of osseous lesions of the glenoid in anterior shoulder instability.26 Additionally, Bigliani and associates retrospectively reviewed the surgical findings of 200 patients and discovered only an 11% incidence of glenoid rim lesions, suggesting that many of these lesions may be difficult to diagnose at the time of surgery.20 The results of our large series affirm the findings of Rokous and associates and Patte and Bernageau and emphasize the importance of the glenoid profile view in identifying these lesions.
It should be recognized that all osseous lesions of the glenoid were not recognized on the Bernageau glenoid profile view. Visibility of a fracture fragment on this view is dependent upon the position of the fragment. A very inferiorly located fracture fragment is not readily seen on the Bernageau glenoid profile view; however, an anterior posterior view will usually demonstrate this fracture. Conversely, the Bernageau glenoid profile view is more adept at demonstrating fracture fragments located slightly more superiorly which are usually not seen on the anterior posterior view (Figure 8). The inclusion of both of these projections, as demonstrated by the results of this study, will identify the majority of glenoid fractures occurring as a result of traumatic chronic anterior shoulder instability.
To our knowledge, this study represents the largest series specifically evaluating radiographic findings in traumatic chronic anterior provider, in establishing a diagnosis of anterior shoulder instability in difficult cases, such as painful shoulders caused by instability.27-29 Furthermore, radiographic findings, particularly anterior glenoid rim fractures, may change the operative procedure employed. It has been suggested that the presence of a large glenoid rim fracture may be an indication for a coracoid transfer procedure; therefore, detection of these lesions on radiographic examination could be clinically useful in therapeutic decision making.30 Burkhart and De Beer have concluded that contact athletes with anterior glenoid bony deficiency should be treated with a coracoid transfer procedure because of the high rate of failure of soft tissue procedures in this population.31
This study is not without limitations both in scientific methodology and application. While our radiograph interpreter was blinded to the patients’ clinical history, physical examination, and intraoperative findings, the only patients on whom we routinely obtain glenoid profile radiographs are those with suspected instability. Therefore, the observer was not blinded to the suspected diagnosis. Also, our radiographs were strictly quality controlled by using fluoroscopy to obtain nearly perfectly matched glenoid profile comparative views. This fluoroscopically controlled technique may not currently be available in some centers, limiting the application of this study. Lastly, bilateral shoulder pathology (four patients in this series) limits the usefulness of the Bernageau glenoid profile view secondary to lack of a contralateral control projection.
In conclusion, despite these acknowledged limitations, the results of this study accurately demonstrate the high incidence of osseous lesions (as high as 95% overall) in patients with traumatic chronic anterior shoulder instability that can be observed when employing a detailed radiographic method. These lesions occur in both the humeral head and, perhaps more importantly, the glenoid. shoulder instability and provides strong affirmation of some previously reported data. Additionally, this study demonstrates the usefulness of a glenoid profile radiograph in assisting the less experienced examiner, i.e. the primary care
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