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1 Original Article With Video Illustration Kim s Lesion: An Incomplete and Concealed Avulsion of the Posteroinferior Labrum in Posterior or Multidirectional Posteroinferior Instability of the Shoulder Seung-Ho Kim, M.D., Kwon-Ick Ha, M.D., Jae-Chul Yoo, M.D., and Kyu-Cheol Noh, M.D. 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. Key Words: Posterior instability Multidirectional posteroinferior instability Kim s lesion Labroplasty Arthroscopy Shoulder. From the Department of Orthopaedic Surgery, Sungkyunkwan University School of Medicine, Samsung Medical Center (S-H.K, J-C.Y., K-C.N.); and the Department of Orthopaedic Surgery, Seoul Veterans Hospital (K-I.H.), Seoul, Korea. Address correspondence and reprint requests to Seung-Ho Kim, M.D., Department of Orthopaedic Surgery, Sungkyunkwan University School of Medicine, Samsung Medical Center, 50 Ilwon-Dong, Kangnam-Ku, Seoul , Korea. smcknot@smc.samsung.co.kr 2004 by the Arthroscopy Association of North America /04/ $30.00/0 doi: /j.arthro NOTE: To access the video illustrations accompanying this report, visit the September online issue of Arthroscopy at Aredundant or insufficient posterior capsule has been considered as the main cause of posterior instability, especially in shoulders with posterior instability, when combined with multidirectional hyperlaxity. 1-3 In the literature on posterior instability, the incidence rate of the posterior labral lesion varies from 10% to 100%. 3-8 Posterior labral lesions include detachment of the posterior labrum, so-called reverse Bankart lesion, flap tear, bucket-handle lesion, chondrolabral erosion, and labral split. 2-4,7 The interesting finding is that the incidence of the posterior labral lesion is significantly higher in those studies that used arthroscopic treatment as the surgical procedure. 4,5,7 This suggests that the incidence of the posterior labral lesion is largely influenced by the diagnostic modality. 712 Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 20, No 7 (September), 2004: pp

2 KIM S LESION 713 months; range, 24 to 92 months; standard deviation, 7 months). Kim s Lesion FIGURE 1. Kim s lesion had a superficial tearing between the posteroinferior labrum and glenoid articular cartilage without complete detachment of the labrum (marginal crack). The posteroinferior labrum lost its normal height and became a flat labrum, which resulted in the retroversion of the chondrolabral glenoid. The purpose of this article is to report a new lesion, the Kim s lesion, which is a concealed avulsion of the posterior labrum, and to evaluate the results of its arthroscopic treatments. Patient Selection METHODS From 1996 to 1999, all patients who were arthroscopically treated at our institute for unidirectional posterior instability or multidirectional posteroinferior instability were prospectively evaluated for the posterior labral lesion. We found 16 patients who showed incomplete avulsion of the labrum in the posteroinferior aspect of the glenoid by arthroscopic evaluation. All patients were treated with conversion of the incomplete labral lesion into a full-thickness tear and arthroscopic repair using suture anchors along with variable degrees of capsular shift. Surgery was indicated after nonoperative treatment for at least 6 months had failed. We excluded patients who had previously undergone surgery on the affected side. Of 16 patients, 1 was lost during a follow-up period of less than 2 years. Thus this study included 15 patients who were able to return for the final evaluation after a minimum of 2 years (mean, 31 Kim s lesion is a superficial tearing between the posteroinferior labrum and the glenoid articular cartilage without complete detachment of the labrum (marginal crack). The posteroinferior labrum had lost its normal height and became a flat labrum, with subsequent retroversion of the chondrolabral glenoid (Fig 1). Probing of the lesion revealed fluctuation of the posteroinferior labrum and a loose attachment. These labral lesions were limited to the posteroinferior quadrant of the glenoid in shoulders with posterior instability, typically present at the 6- to 9-o clock position for the right shoulder and the 3- to 6-o clock position for the left shoulder. For shoulders with multidirectional posteroinferior instability, the lesion is extended to the entire inferior glenoid labrum. When the superficial portion was incised with a Liberator knife (Linvatec, Largo, FL), for 1 or 2 mm in depth, the lesion revealed detachment of the deep portion of the labrum from the medial surface of the glenoid (Fig 2, Video 1). Surgical Techniques Labroplasty was performed in all cases. The Kim s lesion was detached, freshened, and repaired on the surface of the glenoid to restore the labral height. Along with the repair, the capsule was always shifted. For unidirectional posterior instability, only the posterior capsule was shifted superiorly. For multidirectional posteroinferior instability, the labroplasty was FIGURE 2. When the superficial portion was incised with a Liberator knife, 1 or 2 mm in depth, detachment of the deep portion of the labrum from the posteroinferior rim of the glenoid was seen.

3 714 S-H. KIM ET AL. FIGURE 3. (A) The posterior portal was created 2 cm inferior to the posterolateral acromial angle, which was about 1 cm lateral to the standard posterior glenohumeral portal (arrow). (B) The posterior portal provided the proper angle to the posteroinferior labrum and capsule. accompanied by posterior and inferior capsular shift along with a rotator interval closure. Labroplasty Under general anesthesia, the patient was prepared for the arthroscopic procedure in the lateral decubitus position. The arm was maintained at lateral traction at 30 abduction and 10 forward flexion. The posterior portal was created 2 cm inferior to the posterolateral acromial angle. This position was 1 cm lateral to the standard posterior glenohumeral portal, and provided optimal access to the posteroinferior labrum and capsule (Fig 3). Two anterior portals (anterosuperior and anterior midglenoid) were created just below the acromioclavicular joint and above the leading edge of the subscapularis tendon while maintaining at least 1 cm distance between the 2 portals. We used a large, clear, threaded cannula (Linvatec) for the posterior and anterior midglenoid portals and a small nonthreaded cannula (Universal cannula; Linvatec) for the anterosuperior portal. Diagnostic arthroscopy was performed while special attention was being focused on the posteroinferior labrum and capsule. Associated lesions were treated first. Partial-thickness tears of the articular surface of the rotator cuff tendon were debrided. Posteroinferior labral lesions were better visualized through the anterosuperior portal. Because Kim s lesion apparently looked like an intact attachment or had a superficial crack, probing of the posteroinferior labrum was conducted in all cases. While viewing through the anterior superior portal or posterior portal, a Liberator knife was introduced through the anterior midglenoid portal, and the superficial portion of the lesion was detached. Using a shaver and Liberator knife, the labrum was completely mobilized from the glenoid until it could be brought up on the glenoid. Using a small meniscal rasp (Linvatec) and shaver, the glenoid wall was abraded until the healthy bony surface was exposed (Fig 4, Video 2). The inferior and posterior capsules were abraded to enhance the healing potential using convex rasp (Linvatec). While viewing through the anterosuperior portal, a small pilot marking was created on the rim of the glenoid by a small pituitary forceps introduced through the posterior portal. A bone punch was introduced and aimed at the medial end of the pilot marking to create an anchor hole 2 mm from the margin of the glenoid. A suture anchor (Mini- Revo; Linvatec) with No. 2 nonabsorbable sutures (Ethibond; Ethicon, Somerville, NJ) was fixed. One end of the suture was retrieved out of the anterior midglenoid portal. A 90 angled suture hook, which was loaded with Shuttle-Relay (Linvatec), was introduced through the posterior portal, piercing the posterior band of the inferior glenohumeral ligament at the same level or medial plane from the glenoid surface. The posterior band of the inferior glenohumeral ligament was always incorporated into the first suture. The suture was shifted about 1 cm proximally. Then it was passed under the posteroinferior labrum. The Shuttle-Relay was retrieved out of the anterior midglenoid portal. The suture was loaded into the eyelet of the Shuttle-Relay, then pulled back out of the posterior portal. An arthroscopic knot tying was performed. We used the SMC knot, which is a sliding knot with an internal locking mechanism. 9,10 One to 3 suture anchors were used for the repair of the lesion (Fig 5, Video 3).

4 KIM S LESION 715 FIGURE 4. Mobilization of Kim s lesion for labroplasty. (A) Kim s lesion showing loose attachment. (B) Complete detachment of incomplete lesion into full-thickness tear. (C) Mobilization of the labrum up on the glenoid. Posterior Capsular Shift For the area of the intact labral attachment superior to the Kim s lesion, the posterior capsule was shifted continuously in the superior direction without a suture anchor. The suture hook was introduced through the posterior portal and passed through the posterior capsule. The suture hook was shifted superiorly for 1 cm and passed under the labrum. A No. 2 Ethibond suture was passed with Shuttle-Relay and the SMC knot was made. Posterior capsular shift was repeated one after another and progressed proximally until the last suture of the shift passed the posterosuperior labrum just behind the root of the biceps insertion. As the last step, the posterior portal was closed by an Ethibond suture while blindly tying the knot outside of the portal. A catheter for a self-controlled pain pump (Accufuser Plus; Woo Young Medical, Seoul, Korea) was inserted through the anterior skin with the aid of a spinal needle. Inferior Capsular Shift and Rotator Interval Closure For patients with multidirectional posteroinferior instability, inferior capsular shift was also conducted. After completion of posterior capsular shift, the arthroscope was inserted through the posterior portal. The inferior and anterior capsule, as well as corresponding glenoid labrum, were abraded by the arthroscopic rasp. Starting at the 6-o clock position, a suture hook was introduced through the anterior midglenoid portal, and pierced the inferior capsule 1 cm away from the labrum. The suture hook was superiorly shifted and passed under the labrum. The Shuttle- Relay was retrieved through the anterosuperior portal and a No. 2 Ethibond suture was engaged in the eyelet of the Shuttle-Relay. The Shuttle-Relay with the suture was pulled back through the anterior midglenoid portal and arthroscopic knot tying was performed. Proximal shift of the inferior capsule was repeated at

5 716 S-H. KIM ET AL. FIGURE 5. Labroplasty: (A) A Mini-Revo suture anchor with No. 2 Ethibond is fixed. The posterior band of the inferior glenohumeral ligament was always incorporated into the first suture. (B) The suture was shifted about 1 cm proximally and then it was passed under the posteroinferior labrum. The SMC arthroscopic knot tying was performed. a 1-cm distance between each suture until the last suture ends at the anterior base of the biceps root. To perform arthroscopic closure of the rotator interval, the arthroscope was maintained in the posterior portal while the anterosuperior cannula was retrieved slightly out of the capsule. A penetrating suture retriever (Smith & Nephew, Andover, MA), loaded with a No. 2 Ethibond suture, was introduced through the anterosuperior cannula to pierce the superior capsule. Another penetrating suture retriever was inserted into the joint through the anterior midglenoid cannula. The cannula and suture retriever were then slowly withdrawn from the joint to lie just anterior to the capsule. The penetrating suture retriever was used to pierce the anterior capsule and the middle glenohumeral ligament (capsular tissue overlying the superior edge of the subscapularis tendon). The suture in the penetrating suture retriever of the anterosuperior cannula was handed out to the other suture retriever. One or 2 additional sutures were repeated in the same manner using sutures of different colors. By directly viewing from the subacromial portal or in a blind manner, one end of the suture in either portal was passed to the other portal under the deltoid muscle and the FIGURE 6. Rotator interval closure. (A) The penetrating suture retriever was used to pierce the anterior capsule and middle glenohumeral ligament (capsular tissue overlying the superior edge of the subscapularis tendon). The suture in the penetrating suture retriever of the anterosuperior cannula was handed out to the other suture retriever. (B) One or 2 additional sutures were repeated in the same manner using suture of different colors.

6 KIM S LESION 717 SMC sliding knots 9,10 were created while maintaining the arms at about 40 abduction and 30 external rotation (Fig 6). Evaluation Radiographic examinations included anteroposterior and axillary lateral plane radiographs, and magnetic resonance (MR) arthrogram using gadolinium. T1- and T2-weighted axial images of the MR arthrogram were obtained and intra-articular lesions were evaluated. Two of the authors (S-H.K. and K-C.N.) who had experience in shoulder examinations and arthroscopic procedures examined patients blindly. Patients were evaluated for active and passive range-of-motion, anterior instability tests (fulcrum test 11 ), posterior instability test (jerk test 12 ), subacromial sulcus sign, 13 impingement sign (Neer 14 and Hawkins signs 11 ), manual muscle testing, generalized ligamentous laxity, 11,15 three objective shoulder scores (the University of California at Los Angeles scoring system, 16 American Shoulder and Elbow Surgeons Standardized Shoulder Assessment, 17 and Rowe score 18 ), and two subjective measurements (pain 19 and function 20 visual analogue scales). The visual analog scale 19 is widely used as a self-report measure of pain. The scale consists of a 100-mm line that pictorially represents 2 behavioral extremes at either end of a continuum: no pain (score of 0) and extreme pain (score of 100). Subjective measurement of shoulder function was evaluated by a modified method from Kim et al. 8,20 At the examination under anesthesia, anterior and posterior translations were graded based on the grading system of Altcheck et al. 21 During arthroscopic examination, any intra-articular lesion was evaluated, especially focusing on the posteroinferior labral and capsular lesions. Statistical Analysis The preoperative and follow-up range of motion (paired-sample t test), strength, shoulder scores, and pain and function scores were compared (Wilcoxon signed-rank test). Statistical analyses were performed with the alpha value set at Patient Demographics RESULTS There were 13 male and 2 female patients with an average age of 22 years (range, 16 to 31 years). Eleven patients participated in various types of sports activities. The dominant arm was involved in 9 patients TABLE 1. Variable (60%). Thirteen patients (87%) had a history of trauma before the onset of the symptoms. The predominant symptom was shoulder pain with activity in 8 patients (53%) and posterior instability in 7 patients (47%). Pain was elicited while attempting a forward elevation in the sagittal plane at 90. All patients demonstrated a positive jerk test. With the involved arm holding out at 90 abduction, simultaneous adduction and posteriorly directed axial loading applied to the glenohumeral joint produced a sudden palpable or audible clunk, as well as pain. All patients reported that this horizontal maneuver reproduced the same symptom, which occurs during daily and sports activities. Two patients showed spontaneous posterior subluxation and reduction when the arm was placed in adduction and abduction in the forward elevation to 90. Three patients had posteroinferior subluxation by muscular contraction. Based on the classification of Altcheck et al., 21 the posterior instability was subluxation (grade 2 ) in all patients. None had a complete dislocation requiring a manual reduction. Other demographic data are described in Table 1. Radiographic Findings Demographic Data Value* No. of patients 15 Age (yr) (16 31) Sex 13 M, 2 F Dominant extremity 9 (60%) Interval from injury to surgery (mo) 7 4(6 15) Cause of initial instability Contact sport 10 (67%) Overhead sport 3 (20%) Other sport 2 (13%) Sulcus sign Grade 0 7 (47%) Grade 1 5 (33%) Grade 2 2 (13%) Grade 3 1 (7%) ASPTRCT Ellman grade 1 2 (13%) Abbreviation: ASPTRCT, Articular surface partial-thickness rotator cuff tear. *The values are given as the number of patients unless otherwise indicated. Arthroscopic finding. Although none of the patients had abnormal plain radiographs, all patients had a posterior labral lesion shown on MR arthrogram. The MR arthrogram findings, which suggested a Kim s lesion, were a combination of the following: (1) incomplete avulsion or loss of contour

7 718 S-H. KIM ET AL. FIGURE 7. The MR arthrogram findings, which suggested Kim s lesion. (A) Incomplete avulsion or cystic lesion and intact junction between the glenoid articular cartilage and posterior labrum. (B) Loss of labral height and contour. of the posterior labrum, (2) loss of labral height, and (3) intact junction between the glenoid articular cartilage and the posterior labrum (Fig 7). Clinical Outcomes All patients showed improved shoulder scores (Wilcoxon signed-rank test, P.01). According to the University of California at Los Angeles shoulder rating scale, there were 12 excellent, 2 good, and 1 fair results. The patients subjective evaluation for the overall shoulder function improved postoperatively (Wilcoxon signed-rank test, P.01). All patients, except 1 who suffered a postoperative recurrence, were able to return to their prior sports activities with little or no limitation. Thirteen (86%) were graded as having more than 90% of shoulder function (grade 0 or I). One patient (7%) showed more than 80% (grade II) and 1 (7%) had 70% (grade III) of the preinjury level of function. Pain score improved from 4 to below zero point (Wilcoxon signed-rank test, P.0001). Ten patients did not have any shoulder pain and 5 had minimal pain (mean visual analogue scale, 1; range, 1-2) during sports activities. With the number available, shoulder scores and pain and function visual analogue scales were not different with respect to the type of sports activities (P.05) (Table 2). With respect to range of motion, there was no difference between the preoperative and postoperative TABLE 2. Results Variable Preoperative (95% CI) Follow-up (95% CI) P Value Mean shoulder score (points) UCLA* ( ) ( ).001 ASES ( ) ( ).001 Rowe ( ) ( ).001 Mean pain score ( ) ( ).001 Mean activity return (%) (28 50) 90 8 (86 94).001 *The rating system of the University of California at Los Angeles. 11 The American Shoulder and Elbow Surgeons Shoulder Index. 12 The rating system of Rowe et al. 18

8 KIM S LESION 719 FIGURE 8. We hypothesize that this lesion can be generated by submaximal force in the posterior direction. (A) Posterior-directed force initially exerts on the medial part of the labral attachment where the posterior band of the inferior glenohumeral ligament attaches (arrow). This force begins the tearing of the posterior labrum at the medial portion and propagates to the lateral portion of the labrum. (B) When the magnitude of the posterior-directed force is small, detachment of the labrum is limited to the inner portion without involving the chondrolabral junction. forward elevation and external rotation at the side. The mean loss of internal rotation was 2 vertebral levels. Internal rotation with the arm in 90 flexion improved from 11 of deficit to 4 (paired-sample t test, P.003). Fourteen patients were stable at the follow-up according to subjective and objective measurements. The jerk test was converted negative except for 1 patient who had recurrent subluxation. One patient who had postoperative recurrence was a collegiate butterfly swimmer with multidirectional posteroinferior instability who gradually developed recurrent posterior subluxation 12 months after the surgery. None of the patients had operative complications. DISCUSSION Posterior instability and multidirectional posteroinferior instability have been recognized mainly as the results of enlarged capsular volume and insufficient structures in the rotator interval. 1-3 The posterior labral lesion has been considered a minor contribution in the generation of posterior instability. Variable incidences of the posterior labral lesion between studies may be due to different methods of observation. 3-8 Invariably, the incidence is greater in those dealing with arthroscopic treatment. 3-6 This suggests that arthroscopic evaluation increases the diagnostic accuracy of the posterior labral lesion in the shoulders with posterior instability, which otherwise can be overlooked by open surgical procedures. Kim s lesion is a new lesion that can be detected by arthroscopic evaluation. This lesion appears to be intact while the deep portion is loose. Palpation with a probe is mandatory for detecting this lesion. We hypothesize that this lesion can be generated by submaximal force in the posterior direction. A posteriordirected force initially focuses its stress on the inferior portion of the labral attachment where the posterior band of the inferior glenohumeral ligament attaches. This force begins the tearing of the posterior labrum at the inferior portion and propagates to the superior portion of the labrum. When the magnitude of the posterior-directed force is small, detachment of the labrum is limited to the inner portion without involving the chondrolabral junction (Fig 8). With the loose deep portion, repetitive posterior subluxation of the humeral head may generate a shear force on the chondrolabral junction, which results in the marginal crack. With a significant force, this inner portion tear may propagate to the surface of the chondrolabral junction and become evident on the surface. Another significance of Kim s lesion is that the lesion causes a deficiency in the normal labral height. Sometimes the posterior labrum remains more medial to the glenoid articular cartilage, which results in the chondrolabral retroversion. Retroversion of the bony glenoid has been considered as a cause of posterior instability. 22,23 However, it is unclear whether the chondrolabral retroversion is a cause or consequence of the posterior instability. Nevertheless, the loss of labral height and resultant retroversion of the chon-

9 720 S-H. KIM ET AL. drolabral glenoid may produce a similar effect on the posterior stability without retroversion of the bony glenoid. The clinical significance of Kim s lesion is that a surgeon needs to convert this concealed incomplete lesion to a complete tear and then repair it with the posterior band of the inferior glenohumeral ligament. Furthermore, repair of Kim s lesion should reestablish the posterior labral height by placing the suture anchor on the surface of glenoid. Failure to address this concealed lesion and simple capsular plication may result in persistent posterior instability. The results of arthroscopic posterior capsular shift or inferior capsular shift with or without rotator interval closure were very successful in treating this lesion. However, the reported success rate of arthroscopic or open procedures varies greatly. 1-5,7,13 This may partly be due to underestimation of the Kim s lesion in the previous study. We acknowledge that we also had failed to address Kim s lesion in our previous treatments, and subsequently experienced recurrent posterior instability. The treatment of Kim s lesion includes labroplasty to restore posteroinferior labral height with suture anchors and posterior capsular shift toward the superior direction. However, superior shift of the posterior capsule and labroplasty of Kim s lesion are not the only procedures for multidirectional posteroinferior instability. The addition of the inferior capsular shift toward the anterosuperior direction and closure of the rotator interval are necessary. The clinical outcome of this study is quite superior to other reports on similar groups of instability patients. In conclusion, Kim s lesion is a previously unrecognized lesion in posterior instability that has 3 characteristics: (1) marginal crack, (2) chondrolabral retroversion, and (3) incomplete and concealed avulsion. A thorough evaluation of the posteroinferior labrum by palpating with a probe is mandatory. Conversion of this incomplete lesion to a full-thickness tear and repairing with the posteroinferior capsule will stabilize posterior or multidirectional posteroinferior shoulder instability. Appendix Supplementary data Supplementary data associated with this article can be found, in the online version, at doi: / j.arthro REFERENCES 1. Fuchs B, Jost B, Gerber C. Posterior-inferior capsular shift for the treatment of recurrent, voluntary posterior subluxation of the shoulder. J Bone Joint Surg Am 2000;82: Wirth MA, Groh GI, Rockwood CA Jr. Capsulorrhaphy through an anterior approach for the treatment of atraumatic posterior glenohumeral instability with multidirectional laxity of the shoulder. J Bone Joint Surg Am 1998;80: Bigliani LU, Pollock RG, McIlveen SJ, Endrizzi DP, Flatow EL. Shift of the posteroinferior aspect of the capsule for recurrent posterior glenohumeral instability. 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