Summary

We classified shapes of Hill-Sachs lesion into 4 types using computed tomographic images and found that the size of HSL was related to age and the number of subluxation/dislocation.

Abstract

Background

Hill-Sachs lesion (HSL) is strongly associated with recurrent anterior shoulder instability. It still remains unclear about progression of HSL. The purpose of this study was to analyze factors related to shapes of HSL.

Methods

Between April 2012 and April 2013, 210 consecutive patients underwent arthroscopic stabilization for recurrent anterior shoulder instability in our institute. All patients had a minimum of two anterior subluxations or dislocations, demonstrated clinical signs of anterior instability with positive apprehension or relocation tests, and underwent computed tomography (CT) prior to surgery. Exclusion criteria are: (1) previous stabilization surgery (13 shoulders), (2) concomitant rotator cuff tear (4 shoulders), (3) no evidence of Bankart lesion (8 shoulders), (4) unreported number of prior dislocations and subluxations (5 shoulders), (5) combined anterior and posterior instability (3 shoulders), and (6) humeral avulsion of the glenohumeral ligament (2 shoulders). Thus, 175 shoulders (135 men and 40 women) with a mean age of 26 years (range, 13-68) were included in this study. We classified shapes of HSL into 4 types using axial and 3D CT images as follows: type 1, cyst-type, an undersurface defect; type 2, gutter-type, a linear defect with < 5mm width; type 3, fossa-type, a round-shape defect with = 5mm width separated from the bare area; type 4, extensive type, a vast defect merging with the bare area . We investigated differences in age, gender, glenoid morphology, and the number of subluxation/dislocation between the types of HSL. Kruscal-Wallis test and a post-hoc test were used for statistical analyses.

Results

HSLs were classified as type 1, 9 shoulders; type 2, 55 shoulders; type 3, 53 shoulders; type 4, 58 shoulders. The mean ages were 19 (range,15-21 ), 22 (range,15-50 ), 25 (range,13-68 ), and 32 (range,16-60 ) for types1-4, respectively, and the differences were significant (P<0.001). Post-hoc test found that extensive type had higher age than the other types (P<0.001 for each). The mean numbers of shoulder subluxations and dislocations were 4 (range,2-7 ), 5 (range,2-40 ), 9 (range, 2-70), and 22 (range,2-100 ) for types1-4, respectively, and the differences were significant (P<0.001). Post-hoc test revealed that there were significant difference between extensive type and the other types (P<0.001 for each). Significance was also detected between gutter and fossa type (P=0.001). There were no significant differences in gender and glenoid morphology.

Conclusion

The shape of HSL was related to age and the number of subluxation/dislocation. HSL may expand with time after initial injury.