Osseous Injuries Associated With Anterior Shoulder Instability: What the Radiologist Should Know
Abstract
OBJECTIVE. The purpose of this article is to review the current understanding of the underlying pathophysiology of the Hill-Sachs lesion and anterior glenoid bone loss and to discuss the role of imaging in identifying and accurately describing these injuries.
CONCLUSION. Understanding the underlying mechanics of anterior shoulder instability that result in Hill-Sachs lesions and glenoid bone loss, the strengths and weaknesses of the different imaging modalities ordered for their evaluation, and the methods used to characterize these osseous injuries on imaging are essential for the radiologist in this clinical setting.
Anterior shoulder instability results in a variety of soft-tissue and osseous injuries. Injury to the anterior capsuloligamentous structures, the most common type of soft-tissue injury (i.e., Bankart lesion and variants) and its surgical management are well known and have been described extensively in both the radiologic and orthopedic literature [1–18]. The identification and quantification of the osseous injuries seen in anterior instability, namely, Hill-Sachs lesion and anterior glenoid bone loss, are playing an increasingly important role in the treatment algorithm of shoulder instability but have not received the same attention in the radiology literature as soft-tissue injuries [19–24]. Accurate evaluation of osseous injury is crucial to determinations about surgical treatment and to the success of surgery in this subset of patients, especially patients with recurrent instability after initial capsuloligamentous surgery [19–24]. The objectives of this article are to review current understanding of the underlying pathophysiologic mechanism of Hill-Sachs lesion and anterior glenoid bone loss and to discuss the role of imaging in identifying and accurately describing these injuries.
Pathophysiology and Biomechanics
The glenohumeral joint is an inherently unstable joint restrained by a coordinated effort of both dynamic and static stabilizers [25]. The capsulolabral structures (static stabilizers) maintain stability when the shoulder is at the extremes of motion—that is, in the abducted, externally rotated (ABER) position— while they remain taut, maintaining the articulation of the humeral head and glenoid [25]. In the midrange of motion, the capsulolabral structures become lax, and stability is instead provided mainly by concavity compression whereby a concave surface articulates with a convex surface [25]. Concavity compression is a product of contributions from the articular surfaces (static), the rotator cuff musculature (dynamic and static), and to a lesser degree the labrum [25, 26].
The glenoid articular surface contains the humeral head in two ways [27] (Fig. 1). First, the glenoid articular surface is wider and more concave than the humeral head surface; this configuration results in a deepening dishlike effect that maintains the humeral head in place [27]. Second, the arc length of the glenoid resists axial humeral forces through the normal range of shoulder motion until the force vector extends past the glenoid margin (i.e., in the extremes of motion) [27], at which point the adjacent capsuloligamentous structures resist the force. Any defect or deficit along the anterior glenoid margin then results in a shallower, less resistant surface with a shorter arc length, increasing the force along the adjacent capsule and labrum and predisposing the joint to dislocation (Fig. 1).
Fig. 1A —Glenoid arc length and concavity.
A, Diagram shows glenoid arc length (green line) and concave surface stabilizing humeral head while resisting axial humeral forces (orange arrows) through normal range of shoulder motion.
Fig. 1B —Glenoid arc length and concavity.
B, Diagram shows defect along anterior glenoid margin (red arrow) resulting in decreased concavity and shortened arc length (green line), which in turn result in less resistance to humeral forces (orange arrows) and increased risk of anterior instability.
Shoulder instability results from compromise or failure of the coordinated mechanism of stability of the glenohumeral joint. This failure frequently produces abnormal contact between the posterosuperior aspect of the humeral head and the anterior aspect of the glenoid. The result is characteristic injuries at each location.
Hill-Sachs Lesion
Hill-Sachs lesion results from impaction of the stronger anterior glenoid margin on the less compact posterosuperior margin of the humeral head [28]. The location of the Hill-Sachs lesion depends on the degree of abduction and external rotation of the humerus during injury: The more abducted and externally rotated the shoulder during the injury, the more superior and posterior is the position on the humeral head. The location, size, and orientation of the Hill-Sachs lesion have all been postulated to decrease stability of the glenohumeral joint [29–38].
As the size of a Hill-Sachs lesion increases, less contact area becomes available for the humeral head to articulate with the glenoid during abduction and external rotation. There is no agreed on size threshold or critical limit above which a shoulder would be predisposed to instability and merit surgical intervention. However, results of several cadaveric and clinical studies [29–36] have suggested that 12.5–40% humeral head surface involvement can lead to loss of stability and require augmentation.
The orientation of a Hill-Sachs lesion is thought to result in shoulder instability because of the risk of engagement when the shoulder is in the ABER position [27]. Engagement is a descriptive term for abnormal contact between the humeral head and glenoid; it predisposes the shoulder to instability or the symptoms of instability. With the shoulder abducted and externally rotated, an intact posterosuperior humeral head maintains contact with the glenoid throughout the range of motion. If a Hill-Sachs lesion is present and parallel to the anterior margin of the glenoid in the ABER position, the defect loses contact with the glenoid and becomes lodged onto or engages the anterior margin of the glenoid (Fig. 2). When the patient attempts internal rotation, the humeral head becomes stuck on the glenoid, predisposing the joint to instability. Alternatively, when a Hill-Sachs lesion is oriented diagonally in relation to the anterior glenoid in the ABER position, continuous contact between the two articular surfaces during range of motion decreases the likelihood of engagement, instability, and signs of instability.
Fig. 2A —Engaging Hill-Sachs lesion. Green area represents articular cartilage; blue, labrum.
A, Diagram shows that with shoulder in abducted neutral position, there is continuous contact between humeral and glenoid articular surfaces.
Fig. 2B —Engaging Hill-Sachs lesion. Green area represents articular cartilage; blue, labrum.
B, Diagram shows that as humeral head rotates externally, Hill-Sachs lesion can engage anterior glenoid (red arrow) and become stuck. When patient attempts to internally rotate humerus, it will not and instead dislocates anteriorly.
Although contact between the anterior glenoid and posterosuperior humeral head can be achieved passively in most shoulders (for instance, if the shoulder is placed in an exaggerated abduction and external rotation position under anesthesia during arthroscopy), Burkhart and De Beer [27] described the contact as a functional engagement during a more natural range of motion defined as 90° of abduction and between 0° and 135° of extension. Those authors reported recurrent instability in 100% of patients who had this type of engagement.
The importance of the location of the Hill-Sachs lesion in predisposing to shoulder instability has been described in the form of the glenoid track theory [38]. The glenoid track is the contact area between the humeral head and glenoid during abduction and external rotation, defined as 83% of the glenoid width, the other 17% constituting the portion of the glenoid that contacts the rotator cuff insertion. A Hill-Sachs lesion within the confines of the glenoid track would result in consistent contact between the two articular surfaces and lower risk of engagement and instability. The risk of engagement and instability increases the closer the Hill-Sachs lesion is to the medial margin of the track. A Hill-Sachs lesion extending past this medial margin can lead to overriding of the articular surfaces or engagement and instability.
Anterior Glenoid Bone Loss
Injury to the anterior glenoid in patients with shoulder instability typically occurs in one of two forms [39] (Fig. 3). The anterior glenoid margin can be fractured, a result of an avulsion or shear injury, or the anterior glenoid margin can be flattened owing to chronic impaction and attritional change related to repeated humeral head contact. This differentiation may play a role in recurrent instability, because a flattened glenoid has been found to predispose a shoulder to recurrent instability more often than a fractured glenoid in patients with previous Bankart repair [40]. It is important to note that a fractured glenoid can transform into the flattened variant over time if the fracture fragment resorbs. This has been reported as occurring within the first year after the initial injury [41].
Fig. 3A —Types of glenoid bone loss.
A, 34-year-old with osseus Bankart lesion. Sagittal T1-weighted MR image shows fractured, displaced bone fragment (arrow).
Fig. 3B —Types of glenoid bone loss.
B, 27-year-old man with repeated episodes of shoulder instability. Sagittal T1-weighted MR image shows flattened, impacted anterior glenoid margin (line).
In terms of location, glenoid bone loss typically occurs in the anterior aspect along a plane parallel to the long axis of the glenoid and centered mid equator (i.e., 3-o'clock position) and not anteroinferiorly [39, 42]. Anterior glenoid bone loss and the role it plays in shoulder instability, particularly recurrent instability, has been studied extensively [27, 40, 43–49]. The degree of glenoid bone loss has been described with different parameters, including area of bone loss, percentage of bone loss in relation to glenoid length, and percentage of bone loss along the glenoid width [46, 50–52]. The most commonly reported parameter in the orthopedic and radiology literature is percentage of bone loss along the glenoid width.
Anterior glenoid bone loss has been described in as many as 90% of patients with recurrent instability and 22% of those with first-time dislocations [50, 53]. Glenoid bone loss has been found to be a predisposing factor for recurrent instability of shoulders operated on for the first time and in patients who have undergone stabilization surgery [27, 40, 46, 47]. Burkhart et al. [27, 47] found a recurrence rate of 89% in patients with 25– 27% loss of glenoid width. Boileau et al. [40] found a 75% recurrence rate among patients with at least 25% glenoid width bone loss. Several cadaveric and clinical studies have shown critical thresholds of glenoid bone loss, ranging between 20% and 30% of the glenoid width, that are thought to predispose a shoulder to instability [19, 27, 40, 45–48].
The use of a threshold for glenoid bone loss is important for proper treatment selection for patients with shoulder instability. In most cases the threshold serves as the determining factor between arthroscopic soft-tissue stabilization and an open or arthroscopic glenoid augmentation procedure, such as a Latarjet procedure, Bristow procedure, or iliac or tibial bone graft procedure [19–24]. This treatment selection emphasizes the importance of preoperative imaging and accurate identification and quantification of this bone loss.
Bipolar Bone Loss Evaluation
Although the two types of osseous injuries are typically described as individual entities, the key is to consider the Hill-Sachs lesion and glenoid bone loss as two interrelated parts in the pathologic mechanism of shoulder instability. The degree of bone loss at one site affects its articulation with the other articular surface and the overall stability of the glenohumeral joint. A greater degree of glenoid bone loss results in a narrower contact area (or glenoid track), enabling a smaller Hill-Sachs lesion to override or engage along the glenoid. The converse would also be true: A larger Hill-Sachs lesion would result in a narrower contact area and allow a smaller degree of glenoid loss to cause engagement and instability. Viewing and treating these osseous injuries as parts of the same problem can focus treatment on the major site of injury rather than on both injuries [38, 54, 55]. Augmentation of the surface with the greatest bone loss, typically along the glenoid, should effectively correct any discrepancy along the glenohumeral articulation and stabilize the joint while lessening the effect of the smaller defect along the apposing surface [38, 54].
Imaging
The typical imaging evaluation of a patient with a history of shoulder instability begins with radiography, specifically a combination of anteroposterior internal and external, scapular-Y, and axillary views. Although radio-graphs are important screening tools, the definitive imaging assessment is obtained with cross-sectional imaging, that is, MRI or CT, which is typically ordered for patients with recurrent instability, high-energy trauma, or instability at physical examination.
MRI is the usual next step in imaging in this group of patients, either by MR arthrography or conventional MRI, depending on the institution. MRI is typically ordered for the evaluation of the soft-tissue injuries found in anterior shoulder instability, such as tears of the capsulolabral structures, for which it has been found to be the reference standard [56–59]. In the evaluation of osseous injuries, MRI can be used to identify both Hill-Sachs lesions and glenoid bone loss (Figs. 3 and 4). Its role in quantification of these injuries is yet to be determined.
Fig. 4A —MRI appearance of Hill-Sachs lesions.
A, 19-year-old man with recent first-time anterior shoulder dislocation. Axial fat-suppressed T1-weighted MR arthrographic image shows focal flattening with adjacent bone marrow edema (arrow) consistent with small Hill-Sachs lesion, which was confirmed during arthroscopy.
Fig. 4B —MRI appearance of Hill-Sachs lesions.
B, 23-year-old man with history of multiple episodes of previous shoulder instability. Axial fat-suppressed T1-weighted (B) and sagittal T1-weighted (C) MR arthrographic images show large Hill-Sachs lesion with impaction of posterosuperior aspect of humeral head (arrows) confirmed during arthroscopy.
Fig. 4C —MRI appearance of Hill-Sachs lesions.
C, 23-year-old man with history of multiple episodes of previous shoulder instability. Axial fat-suppressed T1-weighted (B) and sagittal T1-weighted (C) MR arthrographic images show large Hill-Sachs lesion with impaction of posterosuperior aspect of humeral head (arrows) confirmed during arthroscopy.
Three-dimensional CT is the first-line imaging modality for the evaluation of glenoid bone loss and Hill-Sachs lesions (Fig. 5). The glenoid has a highly complex 3D anatomy that can vary between individuals [19, 60]. Three-dimensional CT has been found accurate for characterization of this complex anatomy, whereas the dimensions of the glenoid have been misrepresented at 2D imaging [60, 61]. Three-dimensional CT is thought to yield the most information in terms of the extent and magnitude of osseous injuries along the margins of the glenoid [19]. In a 2013 study, 3D CT was reported to be more accurate than 2D MRI and CT in terms of estimation of glenoid bone loss. Compared with the other imaging modalities, 3D CT was also found to facilitate the most consistent and reproducible characterization of bone loss [62]. Results of several clinical and cadaveric studies [63–66] have suggested that MRI is accurate for quantifying glenoid bone loss. None of these studies, however, showed MRI to be equal or superior to CT, specifically 3D CT reconstructions, in the evaluation of glenoid defects (Fig. 6).
Fig. 5A —32-year-old man with multiple previous episodes of anterior shoulder instability and previous anterior labral repair.
A, Three-dimensional CT reconstruction of glenoid shows flattening of anterior glenoid margin (blue arrow), stripping and medial displacement of glenoid bone (red arrow), and adjacent osseous tunnels (green arrows) secondary to anchors from previous labral repair.
Fig. 5B —32-year-old man with multiple previous episodes of anterior shoulder instability and previous anterior labral repair.
B, Three-dimensional CT reconstruction of humeral head shows large vertically oriented Hill-Sachs lesion (arrow). Findings were confirmed during revision arthroscopy.
Fig. 6A —27-year-old man with recurrent anterior shoulder instability. Example of 2D versus 3D imaging in evaluation of glenoid bone loss.
A, Sagittal T1-weighted MR image shows loss of anterior margin of glenoid (arrow) related to previous impaction. Size and extent of bone loss cannot be accurately quantified because of volume averaging on this 2D image through glenoid articular surface.
Fig. 6B —27-year-old man with recurrent anterior shoulder instability. Example of 2D versus 3D imaging in evaluation of glenoid bone loss.
B, Glenoid defect (arrow) confirmed during arthroscopy is better represented on 3D MRI reconstruction of glenoid postprocessed from imaging data acquired during initial MRI examination.
MRI data were used to generate 3D reconstructions of the shoulder in a 2013 study [67]. Using a Dixon-based 3D T1-weighted gradient-echo sequence, the authors produced 3D reconstructions of the humeral head and glenoid that were accurate in size and shape compared with corresponding 3D CT models without a substantial amount of additional imaging or postprocessing time. In addition, the degree of glenoid bone loss was accurately estimated on the reconstructions.
Imaging Report: What to Include and How to Do It
Hill-Sachs Lesions
Hill-Sachs lesions can be consistently identified at cross-sectional imaging. There is no threshold measurement or critical limit that has been determined to predispose to instability and merit augmentation. Instead, the intraoperative appearance and observed range of motion during arthroscopy typically determine treatment. A study of MRI [55] showed that there may be an association between the location of the Hill-Sachs lesion and engagement at physical examination, more medial lesions predisposing to engagement. The location of the Hill-Sachs lesion was marked using a revised biceps angle, which was defined as the angle between the center of the biceps groove and the medial margin of the lesion. This measurement determined the medial extent of the Hill-Sachs lesion, the portion of the lesion that would be the first to engage onto the glenoid in the ABER position.
Glenoid Bone Loss
Accurate estimation of glenoid bone loss plays an important role in the treatment algorithm for patients with shoulder instability. Several methods, primarily entailing CT, have been used to estimate the degree of bone loss on imaging, including the best-fit circle method, surface area method, Pico method, Bankart length measurement, and ratio method [50, 52, 68, 69]. These methods are based on the principle that in most instances the inferior portion of the glenoid has a nearly circular shape [70]. This allows the reader to estimate the dimensions of an intact glenoid in the presence of bone loss by using a best-fit circle along the intact margins of the rest of the glenoid. Difficulty may arise in centering the circle: The landmark orthopedic surgeons use to mark the inferior glenoid center during surgery, the bare area, may be difficult to identify on images. Mal-positioning of the circle can lead to an inaccurate estimate of the degree of glenoid loss [64]. A technique for estimating the location of the bare area is to use the intersection of lines drawn along the long axis and widest anteroposterior diameter of the glenoid [68].
Among the methods described earlier, the best-fit circle method appears to be the simplest technique to understand and use when attempting to quantify glenoid bone loss during imaging (Fig. 7). This method can be used to accurately estimate the degree of bone loss on both 2D and 3D images that show a sagittal or en face view of the entire glenoid. The center of the glenoid can be estimated by drawing a longitudinal line originating from the biceps tubercle toward the inferior glenoid margin. A best-fit circle is drawn along the inferior aspect of the glenoid with its borders along the intact posterior and inferior glenoid margins and its center along the longitudinal line. A horizontal line is then drawn through the center of the circle, perpendicular to the longitudinal line to represent the estimated width of the intact glenoid. A line is drawn between the anterior aspect of the remnant glenoid and anterior margin of the circle to represent the amount of bone loss, typically described in millimeters. This measurement is then divided by the estimate of the intact glenoid width and multiplied by 100% to produce the percentage of glenoid bone loss.
It is helpful to include the size (millimeters) and percentage of bone loss and an image number from the imaging study so the referring physicians can see the plane used to obtain the measurements. If the degree of bone loss is greater inferior (less commonly) or superior (rarely) to the center of the circle, then the measurement technique should be adjusted as such to give estimates of this portion of the glenoid. In these instances, care should be taken to be as specific as possible in describing the location of the greatest bone loss. A description of the location and distribution of the injury on a glenoid clock face (i.e., defect extends from the 2- to the 5-o'clock position) can be helpful. When a glenoid fracture fragment also is present, the dimensions should be measured (anteroposterior × craniocaudal × transverse), and the location of the fragment relative to the anterior remnant glenoid included in the report to help with preoperative planning (Table 1).
| Hill-Sachs Lesion | Glenoid Bone Loss |
|---|---|
| Present or absent | Present or absent |
| Location | Location (clock face) |
| Size (craniocaudal × depth × anteroposterior) / area | Percentage and size (mm) of bone loss along glenoid width |
| Type (flattening vs displaced fracture fragment) |
Measuring glenoid bone loss can be challenging, especially for beginners [64]. The glenoid is a relatively small structure, the width varying from 24 to 28 mm, corresponding to approximately 5% of bone loss for every 1.5–1.7 mm of missing bone [47]. This means that a defect as small as 6–8 mm would result in 20–25% glenoid bone loss and possibly necessitate bone augmentation surgery. Given this small margin of error, it is important to become familiar with the measuring techniques used to estimate glenoid bone loss. Reviewing the images of patients who have already undergone surgery and the reported percentages of bone loss and practicing estimation of bone loss on the available images should be helpful. Another useful practice includes communicating with surgeons to compare the preoperative assessment of the degree of bone loss with the intraoperative findings.
Treatment Options
Several techniques have been used to treat Hill-Sachs lesions either in isolation or concurrently with glenoid bone loss [48]. Humeral osteotomy, a technique for increasing the retroversion of the proximal humerus and make the Hill-Sachs lesion more posterior in location and less likely to engage the anterior glenoid, has been used [71]. Although effective in reducing the risk of recurrent instability, humeral osteotomy has been associated with high rates of reoperation for hardware removal, internal rotation deficits, and poor bone healing (nonunion, malunion) [48]. Soft-tissue and osseous augmentation has also been found effective in the management of Hill-Sachs lesions. Use of structural allograft has reduced the rate of recurrent shoulder instability with only minimal alteration of the surrounding anatomy [72]. The complexity of the surgery and the risk of poor bone healing remain limitations of this technique [72]. Transhumeral bone grafting, a less invasive technique of anatomic reconstruction of the Hill-Sachs lesion, has been effective, but concerns over its use for large lesions and in patients with poor bone quality remain [73].
The role of imaging is to assess healing and positioning of the grafts at the surgical sites and to discern whether complications, such as nonunion or malunion, hardware failure, and infection, have occurred. Given the nature of these procedures, initial evaluation with radiography followed by CT is likely the most effective imaging algorithm.
The use of soft-tissue augmentation in the form of a remplissage procedure is another common technique [74]. During a remplissage (“filling up” in French) procedure, the infraspinatus tendon is used to plug the Hill-Sachs lesion, converting an intraarticular lesion into an extraarticular lesion, which is less likely to engage. The utility of MRI for the evaluation of this type of surgery is not completely known (Fig. 8). Park et al. [75] found MRI useful for evaluating incorporation of the tendon into the defect and the state of the infraspinatus muscle 8 months after surgery.
Fig. 8A —21-year-old man with multiple previous anterior shoulder dislocations and previous remplissage procedure.
A, Axial fat-suppressed (A) and sagittal (B) T1-weighted MR arthrographic images show evidence of previous remplissage procedure with portion of infraspinatus tendon (green arrow) extending into Hill-Sachs lesion and secured by single screw (blue arrow).
Fig. 8B —21-year-old man with multiple previous anterior shoulder dislocations and previous remplissage procedure.
B, Axial fat-suppressed (A) and sagittal (B) T1-weighted MR arthrographic images show evidence of previous remplissage procedure with portion of infraspinatus tendon (green arrow) extending into Hill-Sachs lesion and secured by single screw (blue arrow).
Glenoid bone augmentation entails use of bone graft or portions of the coracoid process to supplement bone loss. The use of structural bone graft, most commonly of iliac origin, was initially described by Eden [76] and Hybbinette [77]. Although the technique was effective in reducing the risk of recurrent instability, the graft harvesting procedure required additional operative time and was associated with high morbidity, prompting the need for a more efficient technique. The Bristow [22] and Latarjet [21] procedures are methods in which the coracoid process is used to augment the glenoid. In the Bristow procedure, which was described first, the tip of the coracoid process (the portion distal to the pectoralis tendon) along with the attached conjoint tendon is transferred to the anterior glenoid and secured by a single screw.
The occurrence of larger glenoid defects and the risk of poor fixation related to the use of a single screw led to use of a larger piece of the coracoid process in the form of the Latarjet procedure [21]. During this operation, the coracoid is cut at its angle, rotated approximately 90°, and along with the conjoint tendon brought to the anterior glenoid, where its secured by two screws. The rotation allows the long axis of the coracoid fragment to fit along the long axis of the glenoid. In both the Latarjet and Bristow procedures, the conjoint tendon serves two functions. First, it provides slinglike stability to the joint in the ABER position [78]. Second, the vascularity associated with the tendon is thought to increase the healing potential at the fixation site [79].
The combination of radiography and CT is the best means of characterization of healing and complications at the glenoid surgical site. Radiography is typically used for monitoring of healing, and CT is ordered when a complication (i.e., hardware failure, nonunion) is seen on the radiographs (Figs 9 and 10). A systemic review of Bristow and Latarjet procedures revealed an overall recurrent dislocation rate of 2.9%, subluxation rate of 5.8%, and nonunion–fibrous union rate of 9.4% [80]. Although these augmentation procedures are effective in treating shoulder instability, complications do occur, emphasizing the importance of postoperative imaging.
Fig. 9A —34-year-old man with recurrent anterior shoulder instability 6 months after Latarjet procedure.
A, Scapular-Y radiograph shows two screws (arrows) fixing portion of coracoid process along anterior margin of glenoid.
Fig. 9B —34-year-old man with recurrent anterior shoulder instability 6 months after Latarjet procedure.
B, Axillary view radiograph shows close apposition (arrow) of coracoid and anterior glenoid margin without lucency, suggesting ongoing healing.
Fig. 10A —Imaging appearance after Latarjet procedures.
A, 29-year-old man with recurrent shoulder dislocation. Anteroposterior radiograph of right shoulder shows evidence of previous Latarjet procedure with portion of coracoid process (blue arrow) secured along anterior glenoid margin by two screws in good position. Deficient coracoid process (green arrow) is evident.
Fig. 10B —Imaging appearance after Latarjet procedures.
B, 48-year-old man who underwent Latarjet procedure 1 year earlier and has had recent episode of anterior shoulder dislocation. Anteroposterior radiograph (B) and 3D CT glenoid reconstruction (C) show dislodged and displaced bone graft (arrow) related to nonunion at operative site. Patient underwent revision Latarjet surgery after imaging.
Fig. 10C —Imaging appearance after Latarjet procedures.
C, 48-year-old man who underwent Latarjet procedure 1 year earlier and has had recent episode of anterior shoulder dislocation. Anteroposterior radiograph (B) and 3D CT glenoid reconstruction (C) show dislodged and displaced bone graft (arrow) related to nonunion at operative site. Patient underwent revision Latarjet surgery after imaging.
Conclusion
Identification and quantification of the osseous injuries that occur in patients with anterior shoulder instability play an important role in treatment selection for this group of patients. Understanding the underlying mechanics that result in these osseous injuries, the strengths and weaknesses of the different imaging modalities ordered for evaluation, and the methods used to characterize them at imaging is essential for radiologists in this clinical setting.
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Submitted: August 20, 2013
Accepted: October 9, 2013
First published: May 21, 2014
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