Many open and arthroscopic techniques have been described for treatment of the unstable shoulder. 1–9,12,14,17–19,21–23,27,33–39 In recent years, the most popular techniques have been those that involve repair of the torn anterior inferior glenohumeral ligament complex. These procedures address the pathologic lesion and minimize the risk of stiffness postoperatively. The Bankart repair restores stability by reattaching the labrum or capsule directly to the anterior glenoid rim. 4,26 Several modifications of the Bankart repair also have been described. 1,5,16,19,27,28,32 The reported rates of recurrent instability after open Bankart repair or capsular shift procedures range from 2% to 10%. 1,15,16,24,28,29,32 These procedures can be difficult technically, especially with respect to dissection of the subscapularis from the capsule and the creation of suture holes in the anterior glenoid rim. Although redislocation rates generally are low, functionally significant loss of motion is possible because of the required disruption of the subscapularis tendon. 13
Arthroscopic Bankart repair procedures have been developed to restore stability to the shoulder while avoiding some of the morbidity associated with the open repair. Unlike some methods for arthroscopic Bankart repair, arthroscopic suture anchor repair has the appeal of using a method of fixation that is identical to that used in an open repair. 2,3,5–12,14,17–19,21–23,33–39 However, a good quality arthroscopic suture anchor repair is difficult to achieve technically. Satisfactory knot tying requires significant practice with special knot tying devices and often unfamiliar knot designs. This process can be difficult to master and time consuming to do. Arthroscopically-tied knots are bulky and may be inferior to those tied open, even with a skilled arthroscopic surgeon. 20 For these reasons, an arthroscopic suture anchor repair using standard suture anchors may not be consistently as high-quality as an open suture anchor repair.
The Knotless Suture Anchor (Mitek Products, Westwood, MA) provides a secure, low-profile suture repair with excellent and consistent capsular shift capabilities without the need for arthroscopic knot tying. Biomechanical testing shows superior suture strength compared with standard suture anchors.
Knotless Suture Anchor Design
The Knotless Suture Anchor (Fig 1) has a similar appearance to the GII anchor (Mitek Products). The Knotless Suture Anchor consists of a Ti body with two nitinol arcs. The arcs have a memory property that creates resistance to anchor pullout after insertion of the anchor into bone through small drill holes. The Knotless Suture Anchor differs structurally from the GII anchor in several ways. A channel or slot is located at the tip of the Knotless Suture Anchor. A short loop of green, Number 1 Ethibond suture (Ethicon, Inc. Somerville, NJ), called the anchor loop, is attached to the tail end of the anchor instead of the long suture strands used in the GII anchor. A second, longer loop of white Number 2–0 Ethibond suture, called the utility loop, is linked to the anchor loop and serves as a passing suture. The utility loop is used to pull the anchor loop through the soft tissue to be repaired. The anchor loop then is captured in the channel at the tip of the Knotless Suture Anchor before insertion of the anchor into bone. The sides of the anchor are flat to create space for the captured suture loop to pass without suture abrasion.
This procedure can be done with the patient in the lateral decubitus position or the beach chair position. The shoulder is examined with the patient under anesthesia. The shoulder is tested for instability by placing the humerus at 90° abduction. Anterior pressure is applied to the humerus to test for anterior instability.
Initial arthroscopic visualization is achieved via a posterior portal. This portal is located approximately 3 cm inferior to the posterolateral corner of the acromion at the posterior soft spot. The arthroscope enters the joint in the interval between the infraspinatus and teres minor muscles.
An anteroinferior portal is established. This portal should be placed as close as possible to the superior edge of the subscapularis tendon to allow access to the anterior and inferior aspect of the glenoid rim.
An anterosuperior portal also is established. This portal is placed in the rotator cuff interval, just superior and anterior to the biceps tendon. Inflow is brought through the anterosuperior portal.
Thorough arthroscopic evaluation is done with examination of the articular surfaces, labrum, biceps tendon, rotator cuff, and glenohumeral ligaments. Complete examination through the posterior and anterior portals should be done.
Preparation of the Anterior Inferior Glenohumeral Ligament and Anterior Glenoid Rim
Preparation requirements to the anterior inferior glenohumeral ligament complex depend on the pathologic lesion that is encountered. Instrumentation via the anteroinferior and anterosuperior portals is useful. The exposed labral edge of a Bankart lesion is debrided with a motorized shaver to promote healing after repair. Care is taken to adequately release and mobilize the anterior inferior glenohumeral ligament from the glenoid and underlying subscapularis tendon. When an anterior labroligamentous periosteal sleeve avulsion lesion 25 is the cause of instability, the periosteum should be incised to release the anterior inferior glenohumeral ligament from the glenoid. This essentially converts an anterior labroligamentous periosteal sleeve avulsion lesion to a Bankart lesion. The anterior inferior glenohumeral ligament often is scarred to the subscapularis muscle requiring dissection in this area. A section of the anterior inferior glenohumeral ligament is resected to shorten the ligament when it is found to be redundant. The proper amount of anterior inferior glenohumeral ligament to resect is determined by pulling the torn anterior inferior glenohumeral ligament into proximity to the glenoid with an arthroscopic grasper while assessing capsular tension. This is a critical step in the procedure that greatly affects the final outcome.
A motorized burr is used to decorticate the anterior glenoid neck from the edge of the articular cartilage medially 1 to 2 cm.
The anteroinferior cannula then is replaced by a larger 8-mm cannula to accommodate the drill guide, suture passer, and knotless anchors. Three drill holes are created in the anterior glenoid rim using the Mitek drill guide and the Mitek 2.9-mm arthroscopic super drill (Fig 2). These drill holes are spaced as far apart as possible (1, 3, and 5 o’clock positions on a right shoulder) and at the edge of the articular cartilage. It is important to direct the drill bit medially, away from the articular surface of the glenoid, by at least a 15° angle to avoid damage to the articular surface. The drill holes are marked with a basket forceps, suction punch, or electrocautery to ease later anchor insertion.
Knotless Suture Anchor Repair Procedure
The Knotless Suture Anchor (Fig 1) is used to repair the anteroinferior glenohumeral ligament to the glenoid rim. A superior shift of the anteroinferior glenohumeral ligament also is done.
The utility loop of the knotless suture anchor assembly is passed through the anteroinferior glenohumeral ligament at a selected site via the anteroinferior portal (Fig 3). This can be achieved using various arthroscopic suture passing techniques.
The utility loop is used to pull the anchor loop through the anteroinferior glenohumeral ligament (Fig 4). As the utility loop pulls the anchor loop through the anteroinferior glenohumeral ligament, the attached anchor is passed down the anteroinferior cannula while being controlled on the threaded inserter rod.
Once the anchor loop has passed through the anteroinferior glenohumeral ligament, one strand of the anchor loop is captured or snagged in the channel at the tip of the anchor (Fig 5). The anchor then is rotated so that the arc that is positioned inside the anchor loop is rotated toward the utility loop. The utility loop is used to pull the anchor loop over one of the anchor arcs. The anchor then is inserted and tapped into the glenoid drill hole to the desired depth to achieve appropriate tissue tension (Fig 6). This process pulls the anteroinferior glenohumeral ligament to the appropriate position. The anteroinferior glenohumeral ligament shifts superiorly and securely approximates to the glenoid rim. The utility loop and inserter rod then are removed. A secure, low-profile repair is achieved, with a superior shift of the anteroinferior glenohumeral ligament (Fig 7).
Suture Loop Shuttle Technique for Arthroscopic Passage of Utility Loop
The author’s preferred technique for arthroscopic passage of the utility loop is a suture loop shuttle technique. 31 The passage of the utility loop through the ligament at a precise location using this technique allows for proper capsule shift. The location for suture loop placement is determined by grasping the ligament with the suture punch and pulling it superiorly to the drill hole site, while ligament tension is assessed. A 48-inch long, Number 2–0 Prolene (Ethicon, Inc) suture loop then is passed through the ligament using the suture punch. The Prolene suture loop serves as a suture shuttle and is used to pull the utility loop into the anteroinferior portal, through the anteroinferior glenohumeral ligament, and then out the anterosuperior portal.
Several techniques have been found to ease capture of the anchor loop. For the inferior two anchors, pass the suture loop from the intraarticular side of the ligament to the extraarticular side. For the superior anchor, pass the suture loop from the extraarticular side of the ligament to the intraarticular side.
Pull the utility loop through the anterosuperior portal to orient the anchor loop at a better angle with respect to the anchor and ease loop capture (Fig 4).
Use the utility loop to facilitate the passage of one of the anchor arcs through the anchor loop. Pull the utility loop to hold the anchor loop safely away from the arcs during the first stages of anchor insertion. Tension on the anchor loop is relaxed once the arcs have entered the bone. Intermittently, pull the utility loop to test the tension of the anchor loop during insertion. Overtensioning can cause the anchor loop to tear through the ligament.
Several anchor loop configurations can lead to anchor loop breakage and should be avoided. One arc must be passed through the anchor loop before anchor insertion. If this is not done, the anchor loop will be cut on insertion into bone (Fig 8). The anchor loop must pass directly from the base of the anchor into the ligament. If, instead, the anchor loop is allowed to wrap around the body of the anchor, then the anchor loop will be at risk of being cut by the closing anchor arc as the anchor is inserted into bone (Figs 9, 10).
The location of passage of the utility loop and anchor loop through the anteroinferior glenohumeral ligament is very important. It should be located inferiorly with respect to the glenoid drill hole so that a superior shift of the anteroinferior glenohumeral ligament is achieved when the anchor is inserted into the drill hole. The anchors are inserted in the most inferior site first progressing to the more superior sites.
Biomechanical Testing and Data Analysis
Suture strength and anchor pull-out strength were tested for the Knotless Suture Anchor and compared with the GII anchor.
MATERIALS AND METHODS
Suture strength was measured for 30 Knotless Suture Anchors having a Number 1 Ethibond suture loop (Group I), 30 GII anchors using Number 1 Ethibond suture (Group II), 30 GII anchors using Number 2 Ethibond suture (Group III), and 30 GII anchors using a Number 5 Ethibond suture (Group IV). Each anchor was placed in a vise. The suture on each GII anchor was tied over a dowel pin. The suture loop on each Knotless Suture Anchor was passed over the dowel pin and captured in the anchor slot creating the functional construct of the knotless suture anchor. The sutures were loaded to failure in an Instron Servo-Hydraulic Materials Tester, Model 8511.20 (Instron Corporation, Canton, MA) at a constant rate of 20 inches per minute. Cyclic loading was not done.
Bone Pullout Testing
Anchor pullout strength was measured for 30 Knotless Suture Anchors (Group V) and 30 GII anchors (Group VI). A 90-lb braided spectra fiber was used instead of a suture for each anchor. Pullout force from a pig femur was measured using an Instron Testing Machine at a constant rate of 20 inches per minute.
The mode of failure for the suture strength test was suture breakage for all anchors tested. The average failure loads are shown in Table 1. The average failure load for Group I was more than twice that for Group II. The suture loop on the Knotless Suture Anchor construct creates a double suture in the repair that effectively doubles the suture strength compared with the GII suture anchor construct. This resulted in the Group I anchors having a higher failure load than even the Group III anchors that had a Number 2 Ethibond suture. The average failure load for Group I was comparable with Group IV where Number 5 Ethibond suture was used.
Bone Pullout Testing
The anchor pullout testing resulted in anchor pullout from bone in all anchors. The average pullout forces are shown in Table 2. The increased anchor pullout strength in the Knotless Suture Anchor group is not statistically significant.
Capsule Shift Data
Clinical observations suggest that the Knotless Suture Anchor provides a significant capsular shift and excellent bone fixation. The degree of shift or capsular tensioning obtained with this device was evaluated quantitatively and compared with that of several common medially-based Bankart repairs in a cadaveric study.
Four medially-based repairs were evaluated: (1) a Bankart repair using standard suture anchors and knot fixation (Bankart repair); (2) a Bankart repair using the standard suture anchors supplemented with a barrel stitch 11 (barrel stitch repair) (Fig 11); (3) a Bankart repair using standard suture anchors supplemented with an oblique capsular plication 10,37 (plication stitch repair) (Fig 12); and (4) a Bankart repair using Knotless Suture Anchors (Knotless Suture Anchor repair)(Fig 13). The superior capsular shift was measured for each repair type.
The average capsular shift and standard deviation obtained after each repair technique are shown in Table 3. All repair methods achieved some degree of superior capsular shift. The Bankart repair using standard suture anchors alone achieved the smallest capsular shift. The plication stitch group and the Knotless Suture Anchor group resulted in statistically significant superior shifts as compared with the standard Bankart repair. The shift achieved with the knotless suture anchors alone was comparable with that achieved with the supplemented repairs.
The reason for an additional shift with the supplementary technique is intuitive. The reason for the knotless anchors is less intuitive. Standard suture anchors provide tissue fixation by compressing the tissue against the exterior of the drill holes on the glenoid rim, 30 whereas the design of the Knotless Suture Anchor provides fixation by pulling the tissue into these drill holes, similar to that seen with transosseous fixation. The author has observed this finding clinically and in the current experimental model. It is likely this accounts for the additional shift observed in this study with the use of the Knotless Suture Anchors.
A prospective evaluation of the first 27 consecutive patients with traumatic anterior instability of the shoulder treated with arthroscopic Bankart repair using the Knotless Suture Anchor has been done. Results at an average 29 months followup are reported (range, 24–39 months).
The study population consisted of 24 males and three females with an average age of 28 years (range, 17–59 years). Twelve of the patients were 22 years or younger. The dominant shoulder was involved in 18 of the patients (16 right shoulders, 11 left shoulders). The average duration of preoperative symptoms was 66 months (range, 3 – 192 months). All patients had an initial traumatic event. All patients had recurrent instability. Twenty-one patients had preoperative dislocations (average, four dislocations) and six patients had recurrent subluxations. Five patients underwent superior labrum anterior and posterior (SLAP) lesion repair at the time of the Bankart repair.
All of the patients reported satisfaction with the surgery. The shoulders in all patients remained stable at the time of followup and the patients did not have feelings of apprehension or episodes of subluxation or dislocation. Twenty patients (74%) regained full range of motion postoperatively. Twenty-five patients (93%) had less than 5° loss of external rotation at 90° abduction. Two patients had a 10° loss of external rotation at 90° abduction. The average loss of external rotation was 2°. One patient (3.8%) experienced a traumatic redislocation 1 year after repair. He was asymptomatic until he dislocated his shoulder when he fell skiing. His shoulder remains stable after revision arthroscopic Bankart repair using Knotless Suture Anchors.
To the author’s knowledge, the current study describes the first knotless suture anchor. Other knotless devices, such as tacks and screws, have been described.
The described technique for arthroscopic Bankart repair using the Knotless Suture Anchor is much simpler to do than other methods of suture anchor repair. Cumbersome knot tying is avoided, excellent capsular shift can be achieved, and a more secure, low-profile repair can be created.
1. Altchek DW, Warren RF, Skyhar MJ, et al: T-Plasty modifications of the Bankart procedure for multidirectional instability of the anterior and inferior types. J Bone Joint Surg 73A:105–112, 1991.
2. Arciero RA, Taylor DC, Snyder RJ, et al: Arthroscopic bioabsorbable tack stabilization of initial anterior shoulder dislocations: A preliminary report. Arthroscopy 11:410–417, 1995.
3. Bacilla P, Field LD, Savoie FH: Arthroscopic Bankart repair in a high demand patient population. Arthroscopy 13:51–60, 1997.
4. Bankart ASB: The pathology and treatment of recurrent dislocation of the shoulder joint. Br J Surg 26:23–29, 1939.
5. Benedetto KP, Glotzer W: Arthroscopic Bankart procedure by suture technique: Indications, technique, and results. Arthroscopy 8:111–115, 1992.
6. Caspari RB: Arthroscopic reconstruction for anterior shoulder instability. Tech Orthop 3:59–66, 1988.
7. Caspari RB: Shoulder arthroscopy: A review of the present state of the art. Contemp Orthop 4:523–531, 1982.
8. Coughlin L, Rubinovich M, Johansson J, et al: Arthroscopic staple capsulorrhaphy for anterior shoulder instability. Am J Sports Med 20:253–256, 1992.
9. Detrisac DA, Johnson LL: Arthroscopic shoulder capsulorrhaphy using metal staples. Orthop Clin North Am 24:71–88, 1993.
10. Elrod BF. Arthroscopic reconstruction of traumatic anterior instability. Oper Tech Sports Med 5:215–225, 1997.
11. Flatow EL: Glenohumeral Instability. In Bigliani LU (ed). The Shoulder. Operative Techniques. Baltimore, Williams & Wilkins 183–195, 1998.
12. Grana WA, Buckley PD, Yates CK: Arthroscopic Bankart suture repair. Am J Sports Med 21:348–353, 1993.
13. Green MR, Christensen KP: Arthroscopic versus open Bankart procedures: A comparison of early morbidity and complications. Arthroplasty 9:371–374, 1993.
14. Hawkins RB: Arthroscopic stapling repair for shoulder instability: A retrospective study of 50 cases. Arthroscopy 5:122–128, 1989.
15. Hovelius L, Thorling J, Fredin H: Recurrent anterior dislocation of the shoulder: Results after the Bankart and Putti-Platt operations. J Bone Joint Surg 61A:566–569, 1979.
16. Jobe FW, Giangarra CE, Kvitne RS, et al: Anterior capsulolabral reconstruction of the shoulder in athletes in overhand sports. Am J Sports Med 19:428–434, 1991.
17. Johnson LL: Arthroscopy of the shoulder. Orthop Clin North Am 11:197–204, 1980.
18. Lane JG, Sachs RA, Riehl B: Arthroscopic staple capsulorrhaphy: A long-term follow-up. Arthroscopy 9:190–194, 1993.
19. Levine WN, Richmond JC, Donaldson WR: Use of the suture anchor in open Bankart reconstruction: A follow-up report. Am J Sports Med 22:723–726, 1994.
20. Loutzenheiser TD, Harryman II DT, Yung SW, et al: Optimizing arthroscopic knots. Arthroscopy 11:199–206, 1995.
21. Matthews LS, Vetter WL, Oweida SJ, et al: Arthroscopic staple capsulorrhaphy for recurrent anterior shoulder instability. Arthroscopy 4:106–111, 1988.
22. Morgan CD, Bodenstab AB: Arthroscopic Bankart suture repair: Technique and early results. Arthroscopy 3:111–122, 1987.
23. Morgan CD: Arthroscopic transglenoid Bankart suture repair. Oper Tech Orthop 1:171–179, 1991.
24. Neer II CS, Foster CR: Inferior capsular shift for involuntary inferior and multidirectional instability of the shoulder: A preliminary report. J Bone Joint Surg 62A:897–908, 1980.
25. Neviaser TJ: The anterior labroligamentous periosteal sleeve avulsion lesion: A cause of anterior instability of the shoulder. Arthroscopy 9:17–21, 1993.
26. Perthes G. Uber operationen bei habitueller schulterluxation. Dtsch Ztschr Chir 85:199–222, 1906.
27. Richmond JC, Donaldson WR, Fu F, et al: Modification of the Bankart reconstruction with a suture anchor: Report of a new technique. Am J Sports Med 19:343–346, 1991.
28. Rowe CR, Patel D, Southmayd WW: The Bankart procedure: A long term end-result study. J Bone Joint Surg 72A:1193–1197, 1990.
29. Rowe CR, Zarins B: Recurrent transient subluxation of the shoulder. J Bone Joint Surg 63A:863–872, 1981.
30. Tamai K, Higashi A, Tanabe T, et al: Recurrences after open Bankart repair: A potential risk with the use of suture anchors. J Shoulder Elbow Surg 8:37–41, 1999.
31. Thal R: A technique for arthroscopic mattress suture placement. Arthroscopy 9:605–607, 1993.
32. Thomas SC, Matsen FA. An approach to the repair of avulsion of the glenohumeral ligaments: The management of traumatic anterior glenohumeral instability. J Bone Joint Surg 71A:506–513, 1989.
33. Warner JJP, Miller MD, Marks P, et al: Arthroscopic Bankart repair with the Suretac device. Part I: Clinical observations. Arthroscopy 11:2–13, 1995.
34. Warner JJP, Miller MD, Marks P, et al: Arthroscopic Bankart repair with the Suretac device. Part II: Experimental observations. Arthroscopy 11:14–20, 1995.
35. Warner JJP, Pagnani M, Warren FF, et al: Arthroscopic Bankart repair utilizing a cannulated absorbable fixation device. Orthop Trans 15:761–762, 1991.
36. Wolf EM: Arthroscopic anterior shoulder capsulorrhaphy. Tech Orthop 3:67–73, 1988.
37. Wolf EM, Eakin CL: Arthroscopic capsular plication for posterior shoulder instability. Arthroscopy 14: 153–163, 1998.
38. Wolf EM, Wilk RM, Richmond JC: Arthroscopic Bankart repair using suture anchors. Oper Tech Orthop 1:184–191, 1991.
39. Zuckerman JD, Matsen FA: Complications about the glenohumeral joint related to the use of screws and staples. J Bone Joint Surg 66A:175–180, 1984.
Jon J. P. Warner, MD; and Brian J. Cole, MD, Guest Editors