- Email: [email protected]
The prevalence of a large Hill-Sachs lesion that needs to be treated
J Shoulder Elbow Surg (2013) 22, 1285-1289
www.elsevier.com/locate/ymse
The prevalence of a large Hill-Sachs lesion that needs to be treated Daisuke Kurokawa, MDa, Nobuyuki Yamamoto, MD, PhDa, Hideaki Nagamoto, MDa, Yasushi Omori, MD, PhDa, Minoru Tanaka, MDb, Hirotaka Sano, MD, PhDa, Eiji Itoi, MD, PhDa,* a b
Department of Orthopaedic Surgery, Tohoku University School of Medicine, Sendai, Japan Department of Orthopaedic Surgery, Tohoku Rosai Hospital, Sendai, Japan Background: A large Hill-Sachs lesion has been considered a risk factor for postoperative recurrence of shoulder instability. However, there are few reports describing the prevalence of Hill-Sachs lesions that engage with the glenoid. The purpose of this study was to clarify the prevalence of engaging Hill-Sachs lesions using the concept of the glenoid track. Materials and methods: The computed tomography images of 100 consecutive patients with unilateral recurrent anterior shoulder dislocations were assessed. An image in the plane perpendicular to the rotator cuff attachment was reconstructed from the DICOM (Digital Imaging and Communications in Medicine) data, and the maximum distance from the medial margin of the Hill-Sachs lesion to the medial margin of the rotator cuff footprint was measured. The location of the Hill-Sachs lesion in the glenoid track was assessed, and when the Hill-Sachs lesion extended medially over the glenoid track, it was defined as an ‘‘engaging Hill-Sachs lesion.’’ Results: Engaging Hill-Sachs lesions were observed in 7 of 100 cases (7%). There were 2 types of Hill-Sachs lesions: a large and wide type (3 cases) and a narrow but medially located type (4 cases). All cases with an engaging Hill-Sachs lesion had a large bony defect of the glenoid at the same time. Conclusions: In our series of consecutive 100 cases, the prevalence of engaging Hill-Sachs lesions was 7%. There were 2 types of Hill-Sachs lesions: a wide and large type and a narrow but medially located type. Level of evidence: Basic Science, Anatomic Study, Imaging. Ó 2013 Journal of Shoulder and Elbow Surgery Board of Trustees. Keywords: Anterior shoulder instability; Hill-Sachs lesion; glenoid track; engaging Hill-Sachs lesion; glenoid bony defect
Shoulders with recurrent anterior dislocation often have bony lesions. The Hill-Sachs lesion is observed in 77% to 100% of shoulders with recurrent dislocation.5,8,9,11,12,15 The experimental protocol of this study was approved by the Ethics Committee of Tohoku University School of Medicine (study No. 2010-400). *Reprint requests: Eiji Itoi, MD, PhD, Department of Orthopaedic Surgery, Tohoku University School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan. E-mail address: [email protected] (E. Itoi).
A large Hill-Sachs lesion has been considered a risk factor for postoperative recurrence because of engagement with the glenoid rim. Previous reports have dealt with the size, diameter, or volume of Hill-Sachs lesions.1,4,9,10,13 Yamamoto et al14 introduced a new concept, the glenoid track, to evaluate which Hill-Sachs lesions engage with the glenoid. The glenoid track is a contact zone of the glenoid on the humeral head when the arm is elevated while the arm is maintained in maximum external rotation and maximum
1058-2746/$ - see front matter Ó 2013 Journal of Shoulder and Elbow Surgery Board of Trustees. http://dx.doi.org/10.1016/j.jse.2012.12.033
1286 horizontal extension. If the Hill-Sachs lesion extends more medially over the medial margin of the glenoid track, there is a risk of engagement and dislocation. According to the measurement of Yamamoto et al using cadaveric shoulders, the medial margin of the glenoid track was located at a distance equivalent to 84% of the width of the glenoid. Recently, Omori et al6 confirmed the existence of the glenoid track in vivo using magnetic resonance images. They found that the medial margin of the glenoid track was located at a distance equivalent to 85% of the glenoid width when the arm was elevated at 90 . An ‘‘engaging Hill-Sachs lesion’’ was first reported by Burkhart and De Beer.2 It was an arthroscopic finding, and the size of the lesion was not defined. The prevalence of this engaging Hill-Sachs lesion was reported to be 1.5% by Burkhart and De Beer, 27% by Pagnani,7 and 34% by Cho et al.3 This large variety in prevalence may come from a lack of precise definition of the lesion. We believe that the size of an engaging Hill-Sachs lesion needs to be more precisely defined so that we can make an apple-to-apple comparison. Using the glenoid track concept, we defined an engaging Hill-Sachs lesion as a lesion that extended medially over the medial margin of the glenoid track. The purposes of this study were (1) to clarify the prevalence of an engaging Hill-Sachs lesion, which was defined as described earlier, and (2) to determine the location of the Hill-Sachs lesion in the glenoid track.
Materials and methods Subjects The DICOM (Digital Imaging and Communications in Medicine) data of the computed tomography (CT) images of 200 shoulders of 100 patients with unilateral traumatic anterior shoulder dislocations were used in this study. There were 72 male and 28 female patients, with a mean age of 28 years (range, 15-66 years). Those with bilateral shoulder instability, those who had been operated on previously, or those with rotator cuff tears were excluded from this study. To evaluate the glenoid defect size of an involved shoulder, the normal glenoid size of the contralateral shoulder was used. Because the normal glenoids were not available in bilateral cases, they were excluded.
CT images CT images were obtained by a CT scanner (SOMATOM Definition [Siemens AG, Munich, Germany] or Brightspeed [GE Healthcare UK, Chalfont St Giles, UK]) with the patient supine in the center of the gantry table with the arm at the side of the trunk. CT images were taken with a continuous axial 1-mm slice thickness and pitch of 1 for the SOMATOM Definition scanner and with a continuous axial 0.625-mm slice thickness and pitch of 1.375 for the Brightspeed scanner.
D. Kurokawa et al.
Figure 1 Width of glenoid track. The posterior view of the humeral head and the glenoid is shown. (A) In cases without a glenoid defect, the glenoid track width was defined as 85% of the glenoid width (a). (B) In cases with a glenoid defect, the glenoid track width (b) was defined as the length obtained by subtracting the glenoid bony defect width (c) from 85% of the unaffected glenoid width. multi-planar reconstructions. First, the DICOM data of the glenoid were reconstructed in the oblique sagittal plane en face to the glenoid fossa. In this plane, an outer fitting circle of the glenoid was constructed for each case. Next, the data reconstructed 1-mm-thick slices in the axial plane perpendicular to the superoinferior diameter of the glenoid, and the maximum length from the anterior rim to the posterior rim of the glenoid was measured as the glenoid width. The glenoid width was measured in bilateral shoulders, and the difference between them was defined as the width of the glenoid bony defect.
Assessment of occupancy of Hill-Sachs lesion in glenoid track When there was no glenoid bony defect, the width of the glenoid track was defined as 85% of the glenoid width6 (Fig. 1, A). When there was a glenoid defect, the width of the glenoid track was defined as the length obtained by subtracting the width of the glenoid bony defect from 85% of the unaffected glenoid width14 (Fig. 1, B). The medial margin of the rotator cuff footprint was plotted in every 2-mm slice of the coronal and axial planes. The DICOM data of the humeral head were reconstructed to a 1-mmthick slice in the oblique coronal plane perpendicular to each line connecting the plotted dots. In these slices, the maximum distance from the medial margin of the Hill-Sachs lesion to the medial margin of the rotator cuff footprint was measured (Fig. 2). To express the occupancy of the Hill-Sachs lesion within the glenoid track, the percentage of the length between the footprint and the medial margin of the Hill-Sachs lesion to the width of the glenoid track was calculated (Fig. 3). If the medial margin of the HillSachs lesion extended medially over the medial margin of the glenoid track, this occupancy ratio was more than 100%. Such a Hill-Sachs lesion was defined as an engaging Hill-Sachs lesion.
Measurement of glenoid width and glenoid defect Repeated measurements The DICOM data of the CT images were scanned into a personal computer and were analyzed with the DICOM analyzing software ZioTerm2009 (Ziosoft, Tokyo, Japan), which allowed us to make
The measurements of the glenoid width and the distance from the Hill-Sachs lesion to the footprint in 10 shoulders were repeated
Prevalence of a large Hill-Sachs lesion
1287
Figure 2 Assessment of location of Hill-Sachs lesion. (A) The medial margin of the cuff attachment site is plotted and connected to draw a line (black line). The dotted line indicates the medial margin of the Hill-Sachs lesion. (B) The plane that is perpendicular to the cuff attachment line is shown. In this plane, the distance from the medial margin of the Hill-Sachs lesion (circles) to the medial margin of the rotator cuff attachment (squares) is measured.
Table I Location of Hill-Sachs lesion and size of glenoid bony defect in 7 cases
Figure 3 Occupancy ratio of Hill-Sachs lesion in glenoid track. The occupancy ratio was determined by the following calculation: Occupancy ratio (%) ¼ (Maximum distance from medial margin of Hill-Sachs lesion to medial margin of footprint of rotator cuff/Glenoid track width) 100.
Case No.
Location of medial margin of Hill-Sachs lesion) (%)
Glenoid defecty (%)
1 2 3 4 5 6 7
120.5 118.6 118.5 117.1 116.7 108.5 100.2
22.9 27.1 26.5 21.5 17.3 15.0 12.0
)
Ratio of distance between medial margin of footprint and medial margin of Hill-Sachs lesion to width of glenoid track. y Ratio of glenoid defect to width of unaffected glenoid.
Results
Figure 4 Location of medial margin of Hill-Sachs lesion. In 7 of 100 cases, the most medial margin of the Hill-Sachs lesion extended medially over the glenoid track (shaded bars).
3 times by the same examiner (D.K.) to assess the reliability of the measurements. Pearson correlation coefficients and the coefficients of variation were used for the assessment of reliability. The interval between the initial and second CT measurements for intraobserver reliability was 1 month. The correlation coefficients of the repeated measurements ranged from 0.971 to 0.998. The coefficients of variation were between 0.3% and 3.6%.
A Hill-Sachs lesion was observed in 94 cases (94%). The glenoid width of the unaffected and affected sides was 27 3 mm and 25 2 mm, respectively. A glenoid bone defect was observed in 86 cases (86%), and its average width was 3 2 mm, which was equivalent to 9% 6% of the unaffected side’s glenoid width. The most medial margin of the Hill-Sachs lesion was located 15 4 mm (range, 6-26 mm) medial from the footprint, which was equivalent to 69% 20% (range, 30%-121%) of the glenoid track width (Fig. 4). In 7 cases, the medial margin of the Hill-Sachs lesion extended medially over the glenoid track. The prevalence was 7% in 100 consecutive shoulders with recurrent anterior shoulder dislocations. In these 7 cases, the Hill-Sachs lesion was located in 114% 7% (range, 100%-121%) of the glenoid track width and its glenoid bone defect was 20% 6% (range, 12%-27%) of the unaffected glenoid width (Table I).
Discussion In our series of 100 cases, the prevalence of a Hill-Sachs lesion that extended medially over the glenoid track
1288
D. Kurokawa et al.
Figure 5 Two types of engaging Hill-Sachs lesions (dotted lines): a wide and large Hill-Sachs lesion (A) and a narrow but medially located Hill-Sachs lesion (B).
(engaging Hill-Sachs lesion) was 7%. Burkhart and De Beer2 analyzed the results of 194 arthroscopic Bankart repairs and reported that the prevalence of engaging HillSachs lesions was 1.5%. Pagnani7 and Cho et al3 reported that the prevalence of engaging Hill-Sachs lesions was 27% among 119 shoulders and 33% among 107 shoulders, respectively, in their arthroscopic surveys. These values are greater than ours. It is believed that this is because Pagnani and Cho et al assessed the engaging Hill-Sachs lesion before repairing the Bankart lesion. When a dislocation occurs, a Bankart lesion and a Hill-Sachs lesion are usually created as a result of the dislocation. Therefore, all HillSachs lesions would theoretically engage with the glenoid if the Bankart lesion is kept untreated. This is the reason why the Hill-Sachs lesion in their series engaged with the glenoid far more often than in our series. Focusing on the 7 cases with Hill-Sachs lesions that extended medially over the glenoid track, we found that they could be divided into 2 types: a wide and large Hill-Sachs lesion (3 cases) and a narrow but medially located Hill-Sachs lesion (4 cases) (Fig. 5). This clearly tells us that the risk of engagement does not depend on the width of the Hill-Sachs lesion but depends on the location of its medial margin. Interestingly, all 7 cases had a large glenoid defect (20% of the unaffected glenoid width). If there is a large glenoid defect, the risk of engagement increases accordingly because the width of the glenoid track decreases with an increase of the glenoid defect. For example, in case 2 in Table I, the size of the glenoid defect was 27% of the unaffected glenoid width, and as a result, the Hill-Sachs lesion came out of the glenoid track. If there had been no glenoid defect in this case, the width of the glenoid track would have been 81% of the glenoid width and this Hill-Sachs lesion would have stayed within the glenoid track. This was true in all the other cases: without glenoid defects, all engaging Hill-Sachs lesions would have stayed inside the glenoid track or would have been non-engaging. This finding suggests a hint for treatment. In these 7 cases
with engaging Hill-Sachs lesions, we performed only Latarjet procedures to increase the width of the glenoid track without any treatment to the Hill-Sachs lesions. After the coracoid transfer, the Hill-Sachs lesions were totally covered by the glenoid track, and thus they became non-engaging. Remplissage is sometimes performed for a large Hill-Sachs lesion, but the true indication for this procedure is as yet unknown. This study had several limitations. First, only cases with unilateral instability were included. We used the data of bilateral shoulders with unilateral instability to measure the glenoid defect precisely. Those with bilateral instability might have a different prevalence of engaging Hill-Sachs lesions. Second, 85% of the glenoid width was used as the width of the glenoid track in our study. However, the magnitude of the width of the glenoid track may vary according to the range of shoulder motion.6 Third, we used CT scans to assess the Hill-Sachs lesion, which enabled us to detect a bony lesion. However, we may have missed a lesion that involved only the articular cartilage of the humeral head.
Conclusions The Hill-Sachs lesion that extended medially over the glenoid track was observed in 7% of 100 shoulders with recurrent anterior instability. There were 2 types of HillSachs lesions: a wide and large Hill-Sachs lesion and a narrow but medially located lesion.
Disclaimer The authors, their immediate families, and any research foundations with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article.
Prevalence of a large Hill-Sachs lesion
References 1. Buhler M, Gerber C. Shoulder instability related to epileptic seizures. J Shoulder Elbow Surg 2002;11:339-44. http://dx.doi.org/10.1067/mse. 2002.124524 2. 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 HillSachs lesion. Arthroscopy 2000;16:677-94. 3. Cho SH, Cho NS, Rhee YG. Preoperative analysis of the Hill-Sachs lesion in anterior shoulder instability: how to predict engagement of the lesion. Am J Sports Med 2011;39:2389-95. http://dx.doi.org/ 10.1177/0363546511398644 4. Hardy P. Bony lesions influence on the result of the arthroscopic treatment of gleno-humeral instability. Presented at the Symposium on Shoulder InstabilitydLimits of Arthroscopic Surgery: Bone Deficiency, Shrinkage, Acute Instability at the Fifth International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine Congress; Auckland, New Zealand; 2003. 5. Norlin R. Intraarticular pathology in acute, first-time anterior shoulder dislocation: an arthroscopic study. Arthroscopy 1993;9:546-9. 6. Omori Y, Yamamoto N, Koishi H, Tanaka M, Futai K, Goto A, et al. Measurement of the glenoid track in vivo, investigated by the 3D motion analysis using open MRI. Presented at the 78th Annual Meeting of the American Academy of Orthopaedic Surgeons; San Diego; 2011. 7. Pagnani MJ. Open capsular repair without bone block for recurrent anterior shoulder instability in patients with and without bony defects of the glenoid and/or humeral head. Am J Sports Med 2008;36:180512. http://dx.doi.org/10.1177/0363546508316284
1289 8. Resch H, Povacz P, Wambacher M, Sperner G, Golser K. Arthroscopic extra-articular Bankart repair for the treatment of recurrent anterior shoulder dislocation. Arthroscopy 1997;13:188-200. 9. Rowe CR, Patel D, Southmayd WW. The Bankart procedure: a long-term end-result study. J Bone Joint Surg Am 1978;60: 1-16. 10. Rowe CR, Zarins B, Ciullo JV. Recurrent anterior dislocation of the shoulder after surgical repair. Apparent causes of failure and treatment. J Bone Joint Surg Am 1984;66:159-68. 11. Savoie FH III, Miller CD, Field LD. Arthroscopic reconstruction of traumatic anterior instability of the shoulder: the Caspari technique. Arthroscopy 1997;13:201-9. 12. Spatschil A, Landsiedl F, Anderl W, Imhoff A, Seiler H, Vassilev I, et al. Posttraumatic anterior-inferior instability of the shoulder: arthroscopic findings and clinical correlations. Arch Orthop Trauma Surg 2006;126:217-22. http://dx.doi.org/10.1007/s00402005-0006-4 13. Voos JE, Livermore RW, Feeley BT, Altchek DW, Williams RJ, Warren RF, et al. Prospective evaluation of arthroscopic Bankart repairs for anterior instability. Am J Sports Med 2010;38:302-7. http://dx.doi.org/10.1177/0363546509348049 14. Yamamoto N, Itoi E, Abe H, Minagawa H, Seki N, Shimada Y, et al. Contact between the glenoid and the humeral head in abduction, external rotation, and horizontal extension: a new concept of glenoid track. J Shoulder Elbow Surg 2007;16:649-56. http://dx.doi.org/ 10.1016/j.jse.2006.12.012 15. Yiannakopoulos CK, Mataragas E, Antonogiannakis E. A comparison of the spectrum of intra-articular lesions in acute and chronic anterior shoulder instability. Arthroscopy 2007;23:985-90. http://dx.doi.org/ 10.1016/j.arthro.2007.05.009
www.elsevier.com/locate/ymse
The prevalence of a large Hill-Sachs lesion that needs to be treated Daisuke Kurokawa, MDa, Nobuyuki Yamamoto, MD, PhDa, Hideaki Nagamoto, MDa, Yasushi Omori, MD, PhDa, Minoru Tanaka, MDb, Hirotaka Sano, MD, PhDa, Eiji Itoi, MD, PhDa,* a b
Department of Orthopaedic Surgery, Tohoku University School of Medicine, Sendai, Japan Department of Orthopaedic Surgery, Tohoku Rosai Hospital, Sendai, Japan Background: A large Hill-Sachs lesion has been considered a risk factor for postoperative recurrence of shoulder instability. However, there are few reports describing the prevalence of Hill-Sachs lesions that engage with the glenoid. The purpose of this study was to clarify the prevalence of engaging Hill-Sachs lesions using the concept of the glenoid track. Materials and methods: The computed tomography images of 100 consecutive patients with unilateral recurrent anterior shoulder dislocations were assessed. An image in the plane perpendicular to the rotator cuff attachment was reconstructed from the DICOM (Digital Imaging and Communications in Medicine) data, and the maximum distance from the medial margin of the Hill-Sachs lesion to the medial margin of the rotator cuff footprint was measured. The location of the Hill-Sachs lesion in the glenoid track was assessed, and when the Hill-Sachs lesion extended medially over the glenoid track, it was defined as an ‘‘engaging Hill-Sachs lesion.’’ Results: Engaging Hill-Sachs lesions were observed in 7 of 100 cases (7%). There were 2 types of Hill-Sachs lesions: a large and wide type (3 cases) and a narrow but medially located type (4 cases). All cases with an engaging Hill-Sachs lesion had a large bony defect of the glenoid at the same time. Conclusions: In our series of consecutive 100 cases, the prevalence of engaging Hill-Sachs lesions was 7%. There were 2 types of Hill-Sachs lesions: a wide and large type and a narrow but medially located type. Level of evidence: Basic Science, Anatomic Study, Imaging. Ó 2013 Journal of Shoulder and Elbow Surgery Board of Trustees. Keywords: Anterior shoulder instability; Hill-Sachs lesion; glenoid track; engaging Hill-Sachs lesion; glenoid bony defect
Shoulders with recurrent anterior dislocation often have bony lesions. The Hill-Sachs lesion is observed in 77% to 100% of shoulders with recurrent dislocation.5,8,9,11,12,15 The experimental protocol of this study was approved by the Ethics Committee of Tohoku University School of Medicine (study No. 2010-400). *Reprint requests: Eiji Itoi, MD, PhD, Department of Orthopaedic Surgery, Tohoku University School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan. E-mail address: [email protected] (E. Itoi).
A large Hill-Sachs lesion has been considered a risk factor for postoperative recurrence because of engagement with the glenoid rim. Previous reports have dealt with the size, diameter, or volume of Hill-Sachs lesions.1,4,9,10,13 Yamamoto et al14 introduced a new concept, the glenoid track, to evaluate which Hill-Sachs lesions engage with the glenoid. The glenoid track is a contact zone of the glenoid on the humeral head when the arm is elevated while the arm is maintained in maximum external rotation and maximum
1058-2746/$ - see front matter Ó 2013 Journal of Shoulder and Elbow Surgery Board of Trustees. http://dx.doi.org/10.1016/j.jse.2012.12.033
1286 horizontal extension. If the Hill-Sachs lesion extends more medially over the medial margin of the glenoid track, there is a risk of engagement and dislocation. According to the measurement of Yamamoto et al using cadaveric shoulders, the medial margin of the glenoid track was located at a distance equivalent to 84% of the width of the glenoid. Recently, Omori et al6 confirmed the existence of the glenoid track in vivo using magnetic resonance images. They found that the medial margin of the glenoid track was located at a distance equivalent to 85% of the glenoid width when the arm was elevated at 90 . An ‘‘engaging Hill-Sachs lesion’’ was first reported by Burkhart and De Beer.2 It was an arthroscopic finding, and the size of the lesion was not defined. The prevalence of this engaging Hill-Sachs lesion was reported to be 1.5% by Burkhart and De Beer, 27% by Pagnani,7 and 34% by Cho et al.3 This large variety in prevalence may come from a lack of precise definition of the lesion. We believe that the size of an engaging Hill-Sachs lesion needs to be more precisely defined so that we can make an apple-to-apple comparison. Using the glenoid track concept, we defined an engaging Hill-Sachs lesion as a lesion that extended medially over the medial margin of the glenoid track. The purposes of this study were (1) to clarify the prevalence of an engaging Hill-Sachs lesion, which was defined as described earlier, and (2) to determine the location of the Hill-Sachs lesion in the glenoid track.
Materials and methods Subjects The DICOM (Digital Imaging and Communications in Medicine) data of the computed tomography (CT) images of 200 shoulders of 100 patients with unilateral traumatic anterior shoulder dislocations were used in this study. There were 72 male and 28 female patients, with a mean age of 28 years (range, 15-66 years). Those with bilateral shoulder instability, those who had been operated on previously, or those with rotator cuff tears were excluded from this study. To evaluate the glenoid defect size of an involved shoulder, the normal glenoid size of the contralateral shoulder was used. Because the normal glenoids were not available in bilateral cases, they were excluded.
CT images CT images were obtained by a CT scanner (SOMATOM Definition [Siemens AG, Munich, Germany] or Brightspeed [GE Healthcare UK, Chalfont St Giles, UK]) with the patient supine in the center of the gantry table with the arm at the side of the trunk. CT images were taken with a continuous axial 1-mm slice thickness and pitch of 1 for the SOMATOM Definition scanner and with a continuous axial 0.625-mm slice thickness and pitch of 1.375 for the Brightspeed scanner.
D. Kurokawa et al.
Figure 1 Width of glenoid track. The posterior view of the humeral head and the glenoid is shown. (A) In cases without a glenoid defect, the glenoid track width was defined as 85% of the glenoid width (a). (B) In cases with a glenoid defect, the glenoid track width (b) was defined as the length obtained by subtracting the glenoid bony defect width (c) from 85% of the unaffected glenoid width. multi-planar reconstructions. First, the DICOM data of the glenoid were reconstructed in the oblique sagittal plane en face to the glenoid fossa. In this plane, an outer fitting circle of the glenoid was constructed for each case. Next, the data reconstructed 1-mm-thick slices in the axial plane perpendicular to the superoinferior diameter of the glenoid, and the maximum length from the anterior rim to the posterior rim of the glenoid was measured as the glenoid width. The glenoid width was measured in bilateral shoulders, and the difference between them was defined as the width of the glenoid bony defect.
Assessment of occupancy of Hill-Sachs lesion in glenoid track When there was no glenoid bony defect, the width of the glenoid track was defined as 85% of the glenoid width6 (Fig. 1, A). When there was a glenoid defect, the width of the glenoid track was defined as the length obtained by subtracting the width of the glenoid bony defect from 85% of the unaffected glenoid width14 (Fig. 1, B). The medial margin of the rotator cuff footprint was plotted in every 2-mm slice of the coronal and axial planes. The DICOM data of the humeral head were reconstructed to a 1-mmthick slice in the oblique coronal plane perpendicular to each line connecting the plotted dots. In these slices, the maximum distance from the medial margin of the Hill-Sachs lesion to the medial margin of the rotator cuff footprint was measured (Fig. 2). To express the occupancy of the Hill-Sachs lesion within the glenoid track, the percentage of the length between the footprint and the medial margin of the Hill-Sachs lesion to the width of the glenoid track was calculated (Fig. 3). If the medial margin of the HillSachs lesion extended medially over the medial margin of the glenoid track, this occupancy ratio was more than 100%. Such a Hill-Sachs lesion was defined as an engaging Hill-Sachs lesion.
Measurement of glenoid width and glenoid defect Repeated measurements The DICOM data of the CT images were scanned into a personal computer and were analyzed with the DICOM analyzing software ZioTerm2009 (Ziosoft, Tokyo, Japan), which allowed us to make
The measurements of the glenoid width and the distance from the Hill-Sachs lesion to the footprint in 10 shoulders were repeated
Prevalence of a large Hill-Sachs lesion
1287
Figure 2 Assessment of location of Hill-Sachs lesion. (A) The medial margin of the cuff attachment site is plotted and connected to draw a line (black line). The dotted line indicates the medial margin of the Hill-Sachs lesion. (B) The plane that is perpendicular to the cuff attachment line is shown. In this plane, the distance from the medial margin of the Hill-Sachs lesion (circles) to the medial margin of the rotator cuff attachment (squares) is measured.
Table I Location of Hill-Sachs lesion and size of glenoid bony defect in 7 cases
Figure 3 Occupancy ratio of Hill-Sachs lesion in glenoid track. The occupancy ratio was determined by the following calculation: Occupancy ratio (%) ¼ (Maximum distance from medial margin of Hill-Sachs lesion to medial margin of footprint of rotator cuff/Glenoid track width) 100.
Case No.
Location of medial margin of Hill-Sachs lesion) (%)
Glenoid defecty (%)
1 2 3 4 5 6 7
120.5 118.6 118.5 117.1 116.7 108.5 100.2
22.9 27.1 26.5 21.5 17.3 15.0 12.0
)
Ratio of distance between medial margin of footprint and medial margin of Hill-Sachs lesion to width of glenoid track. y Ratio of glenoid defect to width of unaffected glenoid.
Results
Figure 4 Location of medial margin of Hill-Sachs lesion. In 7 of 100 cases, the most medial margin of the Hill-Sachs lesion extended medially over the glenoid track (shaded bars).
3 times by the same examiner (D.K.) to assess the reliability of the measurements. Pearson correlation coefficients and the coefficients of variation were used for the assessment of reliability. The interval between the initial and second CT measurements for intraobserver reliability was 1 month. The correlation coefficients of the repeated measurements ranged from 0.971 to 0.998. The coefficients of variation were between 0.3% and 3.6%.
A Hill-Sachs lesion was observed in 94 cases (94%). The glenoid width of the unaffected and affected sides was 27 3 mm and 25 2 mm, respectively. A glenoid bone defect was observed in 86 cases (86%), and its average width was 3 2 mm, which was equivalent to 9% 6% of the unaffected side’s glenoid width. The most medial margin of the Hill-Sachs lesion was located 15 4 mm (range, 6-26 mm) medial from the footprint, which was equivalent to 69% 20% (range, 30%-121%) of the glenoid track width (Fig. 4). In 7 cases, the medial margin of the Hill-Sachs lesion extended medially over the glenoid track. The prevalence was 7% in 100 consecutive shoulders with recurrent anterior shoulder dislocations. In these 7 cases, the Hill-Sachs lesion was located in 114% 7% (range, 100%-121%) of the glenoid track width and its glenoid bone defect was 20% 6% (range, 12%-27%) of the unaffected glenoid width (Table I).
Discussion In our series of 100 cases, the prevalence of a Hill-Sachs lesion that extended medially over the glenoid track
1288
D. Kurokawa et al.
Figure 5 Two types of engaging Hill-Sachs lesions (dotted lines): a wide and large Hill-Sachs lesion (A) and a narrow but medially located Hill-Sachs lesion (B).
(engaging Hill-Sachs lesion) was 7%. Burkhart and De Beer2 analyzed the results of 194 arthroscopic Bankart repairs and reported that the prevalence of engaging HillSachs lesions was 1.5%. Pagnani7 and Cho et al3 reported that the prevalence of engaging Hill-Sachs lesions was 27% among 119 shoulders and 33% among 107 shoulders, respectively, in their arthroscopic surveys. These values are greater than ours. It is believed that this is because Pagnani and Cho et al assessed the engaging Hill-Sachs lesion before repairing the Bankart lesion. When a dislocation occurs, a Bankart lesion and a Hill-Sachs lesion are usually created as a result of the dislocation. Therefore, all HillSachs lesions would theoretically engage with the glenoid if the Bankart lesion is kept untreated. This is the reason why the Hill-Sachs lesion in their series engaged with the glenoid far more often than in our series. Focusing on the 7 cases with Hill-Sachs lesions that extended medially over the glenoid track, we found that they could be divided into 2 types: a wide and large Hill-Sachs lesion (3 cases) and a narrow but medially located Hill-Sachs lesion (4 cases) (Fig. 5). This clearly tells us that the risk of engagement does not depend on the width of the Hill-Sachs lesion but depends on the location of its medial margin. Interestingly, all 7 cases had a large glenoid defect (20% of the unaffected glenoid width). If there is a large glenoid defect, the risk of engagement increases accordingly because the width of the glenoid track decreases with an increase of the glenoid defect. For example, in case 2 in Table I, the size of the glenoid defect was 27% of the unaffected glenoid width, and as a result, the Hill-Sachs lesion came out of the glenoid track. If there had been no glenoid defect in this case, the width of the glenoid track would have been 81% of the glenoid width and this Hill-Sachs lesion would have stayed within the glenoid track. This was true in all the other cases: without glenoid defects, all engaging Hill-Sachs lesions would have stayed inside the glenoid track or would have been non-engaging. This finding suggests a hint for treatment. In these 7 cases
with engaging Hill-Sachs lesions, we performed only Latarjet procedures to increase the width of the glenoid track without any treatment to the Hill-Sachs lesions. After the coracoid transfer, the Hill-Sachs lesions were totally covered by the glenoid track, and thus they became non-engaging. Remplissage is sometimes performed for a large Hill-Sachs lesion, but the true indication for this procedure is as yet unknown. This study had several limitations. First, only cases with unilateral instability were included. We used the data of bilateral shoulders with unilateral instability to measure the glenoid defect precisely. Those with bilateral instability might have a different prevalence of engaging Hill-Sachs lesions. Second, 85% of the glenoid width was used as the width of the glenoid track in our study. However, the magnitude of the width of the glenoid track may vary according to the range of shoulder motion.6 Third, we used CT scans to assess the Hill-Sachs lesion, which enabled us to detect a bony lesion. However, we may have missed a lesion that involved only the articular cartilage of the humeral head.
Conclusions The Hill-Sachs lesion that extended medially over the glenoid track was observed in 7% of 100 shoulders with recurrent anterior instability. There were 2 types of HillSachs lesions: a wide and large Hill-Sachs lesion and a narrow but medially located lesion.
Disclaimer The authors, their immediate families, and any research foundations with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article.
Prevalence of a large Hill-Sachs lesion
References 1. Buhler M, Gerber C. Shoulder instability related to epileptic seizures. J Shoulder Elbow Surg 2002;11:339-44. http://dx.doi.org/10.1067/mse. 2002.124524 2. 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 HillSachs lesion. Arthroscopy 2000;16:677-94. 3. Cho SH, Cho NS, Rhee YG. Preoperative analysis of the Hill-Sachs lesion in anterior shoulder instability: how to predict engagement of the lesion. Am J Sports Med 2011;39:2389-95. http://dx.doi.org/ 10.1177/0363546511398644 4. Hardy P. Bony lesions influence on the result of the arthroscopic treatment of gleno-humeral instability. Presented at the Symposium on Shoulder InstabilitydLimits of Arthroscopic Surgery: Bone Deficiency, Shrinkage, Acute Instability at the Fifth International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine Congress; Auckland, New Zealand; 2003. 5. Norlin R. Intraarticular pathology in acute, first-time anterior shoulder dislocation: an arthroscopic study. Arthroscopy 1993;9:546-9. 6. Omori Y, Yamamoto N, Koishi H, Tanaka M, Futai K, Goto A, et al. Measurement of the glenoid track in vivo, investigated by the 3D motion analysis using open MRI. Presented at the 78th Annual Meeting of the American Academy of Orthopaedic Surgeons; San Diego; 2011. 7. Pagnani MJ. Open capsular repair without bone block for recurrent anterior shoulder instability in patients with and without bony defects of the glenoid and/or humeral head. Am J Sports Med 2008;36:180512. http://dx.doi.org/10.1177/0363546508316284
1289 8. Resch H, Povacz P, Wambacher M, Sperner G, Golser K. Arthroscopic extra-articular Bankart repair for the treatment of recurrent anterior shoulder dislocation. Arthroscopy 1997;13:188-200. 9. Rowe CR, Patel D, Southmayd WW. The Bankart procedure: a long-term end-result study. J Bone Joint Surg Am 1978;60: 1-16. 10. Rowe CR, Zarins B, Ciullo JV. Recurrent anterior dislocation of the shoulder after surgical repair. Apparent causes of failure and treatment. J Bone Joint Surg Am 1984;66:159-68. 11. Savoie FH III, Miller CD, Field LD. Arthroscopic reconstruction of traumatic anterior instability of the shoulder: the Caspari technique. Arthroscopy 1997;13:201-9. 12. Spatschil A, Landsiedl F, Anderl W, Imhoff A, Seiler H, Vassilev I, et al. Posttraumatic anterior-inferior instability of the shoulder: arthroscopic findings and clinical correlations. Arch Orthop Trauma Surg 2006;126:217-22. http://dx.doi.org/10.1007/s00402005-0006-4 13. Voos JE, Livermore RW, Feeley BT, Altchek DW, Williams RJ, Warren RF, et al. Prospective evaluation of arthroscopic Bankart repairs for anterior instability. Am J Sports Med 2010;38:302-7. http://dx.doi.org/10.1177/0363546509348049 14. Yamamoto N, Itoi E, Abe H, Minagawa H, Seki N, Shimada Y, et al. Contact between the glenoid and the humeral head in abduction, external rotation, and horizontal extension: a new concept of glenoid track. J Shoulder Elbow Surg 2007;16:649-56. http://dx.doi.org/ 10.1016/j.jse.2006.12.012 15. Yiannakopoulos CK, Mataragas E, Antonogiannakis E. A comparison of the spectrum of intra-articular lesions in acute and chronic anterior shoulder instability. Arthroscopy 2007;23:985-90. http://dx.doi.org/ 10.1016/j.arthro.2007.05.009