Glenoid Rim Morphology in Recurrent Anterior Glenohumeral Instability

Sugaya, Hiroyuki MD; Moriishi, Joji MD; Dohi, Michiko MD; Kon, Yoshiaki MD; Tsuchiya, Akihiro MD

Journal of Bone & Joint Surgery - American Volume:
Scientific Article
Abstract

Background: Knowledge regarding the morphology of the glenoid rim is important when patients with recurrent anterior glenohumeral instability are assessed. Ordinary imaging techniques are not always sensitive enough to demonstrate the morphology of the glenoid rim accurately. We developed a method of three-dimensionally reconstructed computed tomography with elimination of the humeral head to evaluate glenoid morphology. The purpose of the present study was to quantify glenoid osseous defects and to define their characteristics in patients with recurrent anterior instability.

Methods: The morphology of the glenoid rim in 100 consecutive shoulders with recurrent unilateral anterior glenohumeral instability was evaluated on three-dimensionally reconstructed computed tomography images with the humeral head eliminated. The configuration of the glenoid rim was evaluated on both en face and oblique views. Concurrently, we also investigated seventy-five normal glenoids, including both glenoids in ten normal volunteers. Shoulders without an osseous fragment at the anteroinferior portion of the glenoid were compared with the contralateral shoulder in the same patient to determine if the glenoid morphology was normal. In shoulders with an osseous fragment, the fragment was evaluated quantitatively and its size was classified as large (>20% of the glenoid fossa), medium (5% to 20%), or small (<5%). Finally, all 100 shoulders were evaluated arthroscopically to confirm the presence of the lesion at the glenoid rim that had been identified with three-dimensionally reconstructed computed tomography.

Results: Investigation of the normal glenoids revealed no side-to-side differences. Investigation of the affected glenoids revealed an abnormal configuration in ninety shoulders. Fifty glenoids had an osseous fragment. One fragment was large (26.9% of the glenoid fossa), twenty-seven fragments were medium (10.6% of the glenoid fossa, on the average), and twenty-two were small (2.9% of the glenoid fossa, on the average). In the forty shoulders without an osseous fragment, the anteroinferior portion of the glenoid appeared straight on the en face view and it appeared obtuse or slightly rounded, compared with the normally sharp contour of the normal glenoid rim, on the oblique view, suggesting erosion or a mild compression fracture at this site. Arthroscopic investigation revealed a Bankart lesion in ninety-seven of the 100 shoulders and an osseous fragment in forty-five of the fifty shoulders in which an osseous Bankart lesion had been identified with the three-dimensionally reconstructed computed tomography. In the shoulders with distinctly abnormal morphology on three-dimensionally reconstructed computed tomography, the arthroscopic appearance of the anteroinferior portion of the glenoid rim was compatible with the appearance demonstrated by the three-dimensionally reconstructed computed tomography.

Conclusions: We introduced a method to evaluate the morphology of the glenoid rim and to quantify the osseous defect in a simple and practical manner with three-dimensionally reconstructed computed tomography with elimination of the humeral head. Fifty percent of the shoulders with recurrent anterior glenohumeral instability had an osseous Bankart lesion; 40% did not have an osseous fragment but demonstrated loss of the normal circular configuration on the en face view and an obtuse contour on the oblique view, suggesting erosion or compression of the glenoid rim.

Level of Evidence: Diagnostic study, Level IV-1 (case-control study). See Instructions to Authors for a complete description of levels of evidence.

Author Information

Hiroyuki Sugaya, MD; Yoshiaki Kon, MD; Akihiro Tsuchiya, MD; Shoulder and Elbow Service, Funabashi Orthopaedic Sports Medicine Center, 1-833 Hazama, Funabashi, Chiba 2740822, Japan. E-mail address for H. Sugaya: hsugaya@nifty.com

Joji Moriishi, MD; Matsudo Orthopaedic Hospital, 1-161 Asahi-Cho, Matsudo, Chiba 2710043, Japan

Michiko Dohi, MD; Department of Radiology, Jikei University, 3-19-18 Nishishinbashi, Minato-ku, Tokyo 1058471, Japan

Article Outline

Traumatic glenohumeral dislocation may result in an avulsion or impression fracture of the anteroinferior portion of the glenoid rim in association with soft-tissue damage, causing recurrent anterior instability of the shoulder 1,2. Several authors have mentioned the importance of lesions of the glenoid rim in the pathogenesis of this condition 3-5. Major loss of glenoid bone is associated with an unfavorable outcome after arthroscopic stabilization without bone-grafting 6. According to previous reports, the prevalence of lesions of the glenoid rim ranges from <10% to >70%, and the definition of a large glenoid defect has been unclear 4,7,8. We believe that this is largely due to the lack of accurate and practical quantitative imaging techniques. Computerized tomography is recognized as a suitable imaging modality, compared with conventional radiography, for evaluating glenoid abnormalities associated with glenohumeral instability 3,9-11. The purpose of the present report is to introduce a simple practical method of quantitatively evaluating the morphology of the anteroinferior portion of the glenoid rim with use of three-dimensional computed tomography, with the humeral head eliminated, and to determine the prevalence of lesions of the glenoid rim in patients with recurrent anterior glenohumeral instability.

Back to Top | Article Outline

Materials and Methods

Evaluation of the Morphology of the Glenoid Rim

A consecutive series of 100 shoulders of patients (sixty-six male and thirty-four female) who had recurrent anterior glenohumeral instability (forty-three dislocations and fifty-seven subluxations) was evaluated in this study. Each of the patients had sustained an initial traumatic event that had caused anterior dislocation or subluxation of the shoulder. Patients who had bilateral involvement of the shoulder were excluded. The mean age of the patients at the time of the evaluation was 24.3 years (range, fifteen to sixty-three years). The subjects were evaluated preoperatively with three-dimensionally reconstructed computed tomography with a Somatom-Plus scanner (spiral scan, 2-mm slice thickness, pitch of 1, 1-mm reconstruction, three-dimensional-edit mode) or a Somatom volume zoom scanner (spiral scan, detective collimation of 4 × 1 mm, pitch of 4.5, 1.25-mm slice thickness, 1-mm reconstruction, three-dimensional-edit mode), both manufactured by Siemens (Munich, Germany). The humeral head was eliminated during the three-dimensional image-creation process. The configuration of the anteroinferior portion of the glenoid rim was analyzed in detail on both en face and oblique views. When a patient did not have an obvious bone fragment at the anteroinferior portion of the glenoid, the healthy, contralateral glenoid was studied for comparison. Furthermore, to confirm that a normal glenoid does not differ from the contralateral glenoid in the same patient, we analyzed three-dimensionally reconstructed computed tomography images of both shoulders of ten healthy volunteers (eight male and two female; mean age, 26.8 years) with no history of glenohumeral dislocation or subluxation. All patients and study subjects gave informed consent prior to participating in the study.

Back to Top | Article Outline
Quantification Method

On the en face three-dimensionally reconstructed computed tomography image, a healthy glenoid looks pear-shaped 6 and the inferior portion of the glenoid contour can be approximated to a true circle ( Fig. 1 ), as described by Nobuhara 12. The size of the osseous defect as a percentage of the glenoid rim was calculated as a ratio of the area of the bone fragment to the area of an assumed outer fitting circle based on the inferior portion of each glenoid. This was done with the equation: b/A × 100%, where A = the area of the outer fitting circle based on the inferior part of the glenoid contour from 3 o'clock to 9 o'clock, and b = the area of the displayed osseous fragment ( Fig. 2 ). The defect was then graded as large (>20% of the glenoid fossa), medium (5% to 20%), or small (<5%).

Back to Top | Article Outline
Arthroscopic Investigation

Following the preoperative evaluations, all 100 patients underwent arthroscopic evaluation, which was performed routinely with the patient in the beach-chair position and under general anesthesia.

Back to Top | Article Outline

Results

Morphology of the Normal Glenoids

After en face and oblique images had been made of both normal glenoids in the ten healthy volunteers, we concluded that a normal glenoid does not differ substantially from the contralateral glenoid in the same patient. The circular morphology of the anteroinferior portion of the glenoid was consistent bilaterally. In addition, we investigated the contralateral, normal glenoid, for comparison, in fifty-five subjects with instability but no distinct osseous fragment at the anteroinferior portion of the glenoid. Therefore, overall, seventy-five normal glenoids were investigated and served as normal controls. Although there were slight differences in length and width ratios among the glenoids, each pear-shaped glenoid presented a consistent morphology; the inferior portion of the glenoid contour approximated a true circle on the en face view, and the oblique view showed a sharp contour at the anteroinferior portion of the glenoid rim ( Fig. 1 ).

Back to Top | Article Outline
Morphology of the Affected Glenoids

Only ten of the 100 injured shoulders had a normal glenoid configuration. Fifty glenoids had an osseous fragment; one fragment was large, twenty-seven fragments were medium, and twenty-two were small ( Fig. 3 ; Table I ). The large fragment represented 26.9% of the glenoid fossa; the medium fragments, an average of 10.6% (range, 5.4% to 17.2%); and the small fragments, an average of 2.9% (range, 1.3% to 4.6%). Overall, the sizes of the fifty osseous fragments were an average of 7.7% (range, 1.3% to 26.9%) of the glenoid fossa. No osseous fragment was observed in the remaining forty glenoids. However, comparison of these glenoids with the contralateral, normal glenoid showed evidence of an acquired anomalous configuration of the anteroinferior portion of the glenoid rim. The anteroinferior portion either appeared straighter on the en face view ( Fig. 4 ) or appeared to bulge slightly ( Fig. 5 ) on the oblique view compared with the sharp contour of the normal glenoid rim, suggesting erosion or a mild compression fracture in this area.

Back to Top | Article Outline
Arthroscopic Investigation

Arthroscopic investigation revealed a Bankart lesion, evidence of injury to the anteroinferior portion of the labrum, in ninety-seven of the 100 shoulders. The glenoid morphology in the remaining three shoulders had been classified as normal preoperatively with use of the three-dimensionally reconstructed computed tomography. An osseous fragment was observed in forty-five of the fifty shoulders that had been classified as having an osseous Bankart lesion on the three-dimensionally reconstructed computed tomography scan. Arthroscopic visualization of the osseous fragment was not possible initially since each fragment was covered by or embedded in the surrounding soft tissue. Only after separation of the labroligamentous complex from the glenoid neck during preparation did the fragments become visible. The five fragments that had been detected preoperatively but were not seen arthroscopically had been classified as small (average percentage of the glenoid rim, 2.3%). In the shoulders that had been seen to have a distinctly abnormal morphology on three-dimensionally reconstructed computed tomography, regardless of the presence of an osseous fragment, the arthroscopic appearance of the anteroinferior portion of the glenoid rim was compatible with the appearance demonstrated by the three-dimensionally reconstructed computed tomography. However, small morphologic changes of the glenoid rim observed with three-dimensionally reconstructed computed tomography were not identifiable with arthroscopy.

Back to Top | Article Outline

Discussion

Conventional radiography is widely used to detect osseous abnormalities in patients who have glenohumeral instability, and a variety of specialized views have been developed 11. However, although conventional radiography is simple and useful for the majority of shoulders, it is not always reliable for detecting abnormalities of the glenoid in patients with traumatic glenohumeral instability 3. Stevens et al. showed the superiority of computed tomography scans, including three-dimensionally reconstructed images, over conventional plain radiographs for detecting osseous abnormalities, especially of the glenoid 11. We have been able to detect only large or distinct osseous defects, or fragments, of the glenoid on radiographs. Therefore, we believe that plain radiography is neither adequate for quantification of glenoid defects nor reliable for surgical planning because it does not provide detailed information about the glenoid rim.

According to previous reports, the prevalence of lesions of the glenoid rim in shoulders with traumatic anterior glenohumeral instability is quite variable 3,6-8. It is our belief that this apparent variability results from a limitation in the ability to detect abnormal morphology of the glenoid rim with ordinary imaging techniques such as plain radiography 7, plain computed tomography 9,11, computed tomography-arthrography 3,10, and even direct visualization during surgery 3,6. We have found that three-dimensionally reconstructed computed tomography with the humeral head eliminated is a more reliable, noninvasive way to detect the morphology of the glenoid rim in patients with traumatic anterior glenohumeral instability. Moreover, the information obtained with this modality may be even more accurate than information obtained arthroscopically because, in the majority of shoulders, the glenoid neck is covered by soft tissue and scar tissue, limiting visualization of this area during arthroscopy. Edelson investigated 500 skeletons of mature individuals, without access to their medical history, and found that twenty-seven had a fracture of the glenoid rim 13. This suggests that the prevalence of glenoid rim lesions may be higher than has been reported in clinical studies 3,6-8. Bigliani et al. first proposed the term glenoid rim lesions in 1998 3. However, the prevalence of such lesions, which they identified at the time of open surgery, was only 11% in their series of 200 patients.

In the present study, the prevalence of glenoid rim lesions was 90%, with an osseous Bankart lesion in 50% of the glenoids and 40% of the glenoids showing an anomalous configuration. It is true that we had difficulty in distinguishing a small osseous fragment from an erosion in some shoulders. It is possible that erosion is a small marginal fracture that has smoothed out. However, clinically these differences have no effect on surgical planning. We believe that the most important information derived from this study is that 90% of the glenoid rims had morphologic changes, a fact that may influence surgical decision-making and outcomes 14-16.

Quantitative evaluation of the morphology of the glenoid rim is difficult with the use of ordinary imaging techniques or simple visualization since osseous fragments are often covered by soft tissue. After studying normal healthy glenoids on en face three-dimensionally reconstructed computed tomography images with the humeral head eliminated, we realized that the inferior portion of the pear-shaped glenoid contour can be approximated to a true circle. Our method of quantifying the glenoid bone defect is simple but not completely accurate as it depends on manual work to some extent. However, we believe that it is more accurate than other imaging methods and that it is simple and practical enough for clinical use. We believe that definition of glenoid morphology prior to surgery is important in terms of surgical decision-making. On the basis of previous work 4, we think that when a patient has a large osseous Bankart lesion, as defined with our classification system, bone-grafting should be one of the treatment options. For shoulders with a medium or small osseous Bankart lesion, our first choice is arthroscopic reconstruction with fixation of the osseous fragment to restore glenoid morphology 16-18. Thus we believe that evaluation of the glenoid morphology and quantification of the size of the defect with three-dimensionally reconstructed computed tomography provides useful information for preoperative decision-making and may contribute to better surgical outcomes.

Investigation performed at Funabashi Orthopaedic Sports Medicine Center, Funabashi, Chiba, and the Department of Orthopaedic Surgery, Kawatetsu Chiba Hospital, Chiba, Japan

The authors did not receive grants or outside funding in support of their research or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

A commentary is available with the electronic versions of this article, on our web site (http://www.jbjs.org) and on our quarterly CD-ROM (call our subscription department, at 781-449-9780, to order the CD-ROM).

1. Aston JW Jr, Gregory CF. Dislocation of the shoulder with significant fracture of the glenoid. J Bone Joint Surg Am , 1973;55: 1531-3.
2. Kummel BM. Fracture of the glenoid causing chronic dislocation of the shoulder. Clin Orthop , 1970;69: 189-91.
3. Bigliani LU, Newton PM, Steinmann SP, Connor PM, Mcllveen SJ. Glenoid rim lesions associated with recurrent anterior dislocation of the shoulder. Am J Sports Med , 1998;26: 41-5.
4. Itoi E, Lee SB, Berglund LJ, Berge LL, An KN. The effect of a glenoid defect on anteroinferior stability of the shoulder after Bankart repair: a cadaveric study. J Bone Joint Surg Am , 2000;82: 35-46.
5. Rowe CR, Zarins B. Recurrent transient subluxation of the shoulder. J Bone Joint Surg Am , 1981;63: 863-72.
6. Burkhart SS, De Beer JF. Traumatic glenohumeral bone defects and their relationship to failure of arthroscopic Bankart repairs: significance of the inverted-pear glenoid and the humeral engaging Hill-Sachs lesion. Arthroscopy , 2000;16: 677-94.
7. Hovelius L, Eriksson K, Fredin H, Hagberg G, Hussenius A, Lind B, Thorling J, Weckstrom J. Recurrences after initial dislocation of the shoulder. Results of a prospective study of treatment. J Bone Joint Surg Am , 1983;65: 343-9.
8. Rowe CR, Patel D, Southmayd WW. The Bankart procedure: a long-term end-result study. J Bone Joint Surg Am , 1978;60: 1-16.
9. Seltzer SE, Weissman BN. CT findings in normal and dislocating shoulders. J Can Assoc Radiol , 1985;36: 41-6.
10. Singson RD, Feldman F, Bigliani LU. CT arthrographic patterns in recurrent glenohumeral instability. AJR Am J Roentgenol , 1987;149: 749-53.
11. Stevens KJ, Preston BJ, Wallace WA, Kerslake RW. CT imaging and three-dimensional reconstructions of shoulder with anterior glenohumeral instability. Clin Anat , 1999;12: 326-36.
12.     Nobuhara K. The shoulder-its function and clinical aspects. 3rd ed. Tokyo: Igaku-Shoin; 2001. Japanese.
13. Edelson JG. Bony changes of the glenoid as a consequence of shoulder instability. J Shoulder Elbow Surg , 1996;5: 293-8.
14. Gartsman GM, Roddey TS, Hammerman SM. Arthroscopic treatment of anterior-inferior glenohumeral instability. Two to five-year follow-up. J Bone Joint Surg Am , 2000;82: 991-1003.
15. Mishra DK, Fanton GS. Two-year outcome of arthroscopic Bankart repair and electrothermal-assisted capsulorrhaphy for recurrent traumatic anterior shoulder instability. Arthroscopy , 2001;17: 844-9.
16. Sugaya H. Arthroscopic stabilization for recurrent anterior glenohumeral instability using suture anchors. Seikeisaigaigeka (Orthopaedic Surgery and Traumatology) , 2002;45: 49-55. Japanese.
17. Sugaya H, Tsuchiya A, Sonoda M, Kawaguchi Y, Shimada K, Nagasawa R, Okazaki T. Arthroscopic reconstruction of acute anterior glenoid fractures associated with glenohumeral instabilities using suture anchors. Kansetsukyo (Arthroscopy) , 2001;26: 67-72. Japanese.
18. Porcellini G, Campi F, Paladini P. Arthroscopic approach to acute bony Bankart lesion. Arthroscopy , 2002;18: 764-9.
Copyright 2003 by The Journal of Bone and Joint Surgery, Incorporated