Kim's lesion: An incomplete and concealed avulsion of the posteroinferior labrum in posterior or multidirectional posteroinferior instability of the shoulder

Purpose: The purpose of this article is to report a new clinical entity of posterior instability of the shoulder and the results of its treatment. Type of Study: Case series. Methods: The Kim's lesion, which is an incomplete and concealed avulsion of the posteroinferior labrum, was arthroscopically identified in 15 patients who presented with posterior or multidirectional posteroinferior instability. Patients were treated by arthroscopic labroplasty and capsular shift. At a minimum follow-up of 2 years, the outcome was evaluated using subjective (pain and function visual analogue scale) and objective (UCLA, ASES, and Rowe scores) measurements. Results: When visualized under an arthroscope, Kim's lesion apparently had an intact labral attachment and appeared to have a superficial crack at the junction between the articular cartilage of the glenoid and the posteroinferior labrum. However, probing of the lesion revealed detachment of the deep portion of the posteroinferior labrum. The posteroinferior labrum was flat with loss of normal height, which resulted in the retroversion of the chondrolabral glenoid. Incision of the superficial portion of the lesion exposed a loose deep portion of the labrum. Labroplasty was performed to restore the labral height, as well as capsular shift with or without rotator interval closure. The surgical outcome was satisfactory in 14 patients and unsatisfactory in 1 patient. Shoulders were stable in all patients with unidirectional posterior instability. There was 1 recurrence of multidirectional posteroinferior instability. Conclusions: Kim's lesion is an incomplete avulsion of the posteroinferior labrum, which is concealed by apparently intact superficial portion. The clinical significance of this lesion is the need for surgeons to convert this concealed incomplete lesion to a complete tear and repair it with the posterior band of the inferior glenohumeral ligament. A failure to address this lesion may result in persistent posterior instability. Level of Evidence: Level IV, therapeutic, Case Series.