CHAPTER 4 – Knotless Suture Anchor Fixation for Shoulder Instability

Shoulder instability has been treated by myriad arthroscopic and open techniques. It is well documented that restoration of stability can be reliably obtained by the Bankart repair. Open Bankart procedures are successful; however, there is some morbidity associated with them. In an effort to restore stability to the shoulder while avoiding these morbidities, arthroscopic Bankart repair procedures have been developed. Arthroscopic procedures are not without problems. Some of the poor results of arthroscopic repairs continue to be attributed to labral repair without adequately addressing capsular laxity. Furthermore, early fixation methods (tacks, staples, transglenoid sutures) did not achieve anatomic repairs similar to those of open methods. The use of current suture anchors and arthroscopic knot-tying techniques provides fixation comparable to that of open repair. However, arthroscopic suture anchor repair continues to have pitfalls related to the quality, consistency, and technical challenges associated with arthroscopic knots.

A knotless suture anchor technique that eliminates arthroscopic knot tying has been described and has been found to be successful in addressing shoulder instability. Knotless suture anchors provide a strong, consistent, and low-profile repair with an increased superior capsular shift while eliminating the problems associated with the use of special knot-tying devices, multiple knot designs, and time-consuming techniques of standard suture anchors.

Preoperative Considerations

History

It is essential to obtain a history that is consistent with shoulder instability, including the mechanism of injury, associated injuries, treatment history, chronicity, and disability. Younger patients, increased activity level, and participation in collision sports increase the likelihood of further dislocation and indication for subsequent surgical repair.

Typical History

	•	Shoulder injury, often an acute traumatic event typically with shoulder in abduction–external rotation and subluxation or frank dislocation of the glenohumeral joint
	•	Recurrent subluxation or dislocation events despite rehabilitation
	•	Apprehension or sensation of instability with gesturing or reaching

Physical Examination

	•	Presence of apprehension sign
	•	Positive Jobe relocation test result
	•	Range of motion: usually preserved
	•	No rotator cuff symptoms or weakness

Imaging

Radiography

	•	Anteroposterior radiograph
	•	Scapular Y radiograph
	•	Axillary radiograph to evaluate the anterior glenoid for a large bony Bankart lesion or glenoid rim fracture

Other Modalities

A history of documented recurrent dislocations precludes the need for other diagnostic studies unless an associated pathologic condition of the shoulder, such as a superior labral anterior-posterior (SLAP) lesion or rotator cuff tear, is suspected.

	•	Computed tomographic arthrography with reconstruction to assess the bony glenoid, bony Hill-Sachs lesions, and labral pathologic changes
	•	Magnetic resonance imaging with or without the administration of intraarticular contrast material to assess the glenoid labrum, superior labrum, biceps tendon, and rotator cuff

Indications and Contraindications

A typical candidate for arthroscopic shoulder stabilization has a history of multiple shoulder subluxations or dislocations, normal strength, and normal range of motion. Associated findings such as rotator cuff tears, SLAP tears, biceps tears, impingement, and acromioclavicular joint arthritis can be addressed at the same time as the index procedure. Capsular redundancy is often addressed with a capsular shift, plication, or resection as indicated.

Significant glenohumeral arthritis, rotator cuff arthropathy, glenoid deficiency, and significant glenoid fracture are contraindications to arthroscopic Bankart repair. A marked glenoid deficiency may require bone grafting. Furthermore, humeral avulsions of the glenohumeral ligament often require open repair.

Knotless Suture Anchor Design

The knotless suture anchor (
Fig. 4-1

) consists of a titanium body with two nitinol arcs. The arcs have a memory property that creates resistance to anchor pullout after insertion into bone through small drill holes. The knotless suture anchor looks similar to the GII anchor (Mitek Products, Westwood, Mass); however, it differs structurally in several ways. A channel or slot is located at the tip of the knotless suture anchor. A short loop of green No. 1 Ethibond suture (Ethicon, Somerville, NJ), called the anchor loop, is attached to the tail end of the anchor instead of the long strands used in the GII anchor. A second longer loop of white 2-0 Ethibond suture, called the utility loop, is linked to the anchor loop and serves as a passing suture.

The BioKnotless suture anchor (
Fig. 4-2

), which is an absorbable version of the knotless suture anchor, is also available. The BioKnotless suture anchor looks similar to the Mitek Panalok anchor. The BioKnotless suture anchor has a wedge-shaped, poly-l-lactic acid anchor body with a slot located at the tip. The anchor loop is white No. 1 Panacryl, and the utility loop is green 2-0 Ethibond.

The sides of both anchor designs are flat to create space for the captured suture loop to pass without suture abrasion.

Surgical Technique

Anesthesia and Positioning

This procedure can be performed under general anesthesia, interscalene block, or a combination of both. The patient can be positioned in either the lateral decubitus position with a 30-degree posterior tilt or the beach chair position. We prefer the lateral decubitus position. The arm is placed in traction in the lateral position and left free in the beach chair position. Additional distraction of the glenohumeral joint can be achieved by manually lifting the proximal humerus laterally. This increases the space between the humeral head and the glenoid, which greatly improves visualization of the anterior glenoid rim, labrum, and anterior inferior glenohumeral ligament (AIGHL).

Surgical Landmarks, Incisions, and Portals

Landmarks

	•	Acromion
	•	Posterior soft spot
	•	Humeral head
	•	Coracoid

Portals (
Fig. 4-3

)

	•	Posterior portal: 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 the teres minor muscles.
	•	Anterior inferior portal: performed under direct visualization with a spinal needle. A cannula 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.
	•	Anterior superior portal: a cannula is placed under direct visualization in the rotator cuff interval, just superior and anterior to the biceps tendon.

Structures at Risk

	•	Axillary nerve: during mobilization of the anterior inferior labrum
	•	Musculocutaneous nerve: must stay lateral to coracoid with anterior portal placement

Examination Under Anesthesia and Diagnostic Arthroscopy

Examination under anesthesia should demonstrate instability consistent with physical examination findings and the history. Testing for instability in 90 degrees of abduction with the application of anterior pressure is adequate. Diagnostic arthroscopy should be thorough. Evaluation of the articular surfaces, labrum, biceps tendon, rotator cuff, and glenohumeral ligaments should be completed through both the posterior and anterior portals. Particular attention should be specifically directed toward the anterior labrum and AIGHL.

Specific Steps (
Box 4-1

)

1. Ligament Preparation and Mobilization

Preparation of the AIGHL is determined by the pathologic findings of the ligament at diagnostic arthroscopy. Visualization is through the posterior portal and instrumentation is through the anterior portals. If visualization is inadequate from the posterior portal, then visualization can be achieved from the anterior superior portal with instrumentation through the anterior inferior portal. The exposed labral edge of the Bankart lesion is débrided with a motorized shaver or bur to promote healing of the ligament to bone after repair.

Box 4-1 

Surgical Steps

1.    Ligament preparation and mobilization    2.    Glenoid preparation    3.    Drill hole placement    4.    Suture passage    5.    Loop capture and anchor insertion    6.    Loop-anchor repair tensioning and completion    7.    Closure

Commonly, the AIGHL is released and mobilized with care from both the glenoid and the underlying subscapularis with the use of an electrocautery device. If an anterior labroligamentous periosteal sleeve avulsion (ALPSA) lesion is encountered (
Fig. 4-4

), the periosteum should be incised to release the AIGHL from the anterior glenoid (
Fig. 4-5

), essentially converting the ALPSA lesion into a Bankart lesion. Once the ligament is mobilized, a grasper is used to pull the ligament superiorly and to the articular margin while capsular tension and mobility are evaluated. Capsular laxity is also assessed at this time (
Fig. 4-6

). Complete capsular mobilization allows superior capsular shift that often corrects capsular laxity and stretch. Capsular plication is rarely needed when the capsule is mobilized and adequately shifted superiorly. If concerns about the redundancy of the tissue remain, a small section of the edge of the detached AIGHL can be resected by use of a suction punch to shorten the ligament. The proper amount of ligament to resect is determined by approximating the ligament to the glenoid. Determination of capsular laxity and appropriate tensioning is a critical step and greatly affects the final outcome of the repair.

2. Glenoid Preparation

A motorized bur is used to decorticate the anterior glenoid neck medially 1 to 2 cm through the anterior portals. Abrasion of the articular surface of the anterior glenoid 2 to 4 mm from the edge is also performed to promote appropriate healing of ligament to bone.

3. Drill Hole Placement

The anterior inferior cannula is then replaced by a larger 8-mm cannula to accommodate the drill guide, suture passer, and knotless or BioKnotless suture anchors. Three drill holes are made in the anterior glenoid rim with use of the Mitek drill guide and the Mitek 2.9-mm arthroscopic superdrill (
Fig. 4-7

). The drilling of the holes is completed in one step because drilling after each anchor is placed is difficult secondary to poor visualization once the shift has been performed. These drill holes are spaced as far apart as possible (1, 3-, and 5-o’clock positions in the right shoulder) and at the edge of the articular cartilage. It is important to avoid damage to the articular cartilage; as such, the drill bit must be directed medially away from the articular surface of the glenoid by at least a 15-degree angle. Furthermore, it is critical not to torque the drill in determining hole placement, as this can cause difficulty in placing the anchor; undue tissue tension could distort the inserter rod and lead to an inability to line up the anchor with the drilled hole. The drill holes are marked with a basket forceps, suction punch, or electrocautery to ease hole identification during anchor insertion.

4. Suture Passage

Before implant placement, the utility loop of the knotless suture anchor assembly is passed through the AIGHL at a selected site through the anterior inferior portal (
Fig. 4-8

). This can be achieved by use of various arthroscopic suture-passing instruments and techniques. Our preferred technique for arthroscopic passage of the utility loop is a suture loop shuttle technique (
Fig. 4-9

). A Shutt suture punch (Linvatec, Largo, Fla) is used in grasping the ligament and pulling it superiorly to the drill hole site while ligament tension is assessed at the most inferior glenoid hole. This allows precision placement of the utility loop through the ligament and simultaneous assessment of proper capsular shift. A 2-0 polypropylene (Prolene) suture loop 48 inches long is then passed through the ligament, by use of the suture punch, and pulled out the anterosuperior portal. The Prolene suture loop then serves as a suture shuttle and is used to pull the utility loop into the anteroinferior portal, through the AIGHL, and then out the anterosuperior portal. For the inferior two anchors, passing the Prolene suture loop from the intraarticular side of the ligament to the extra-articular side positions the utility loop similarly after shuttling. This helps orient the anchor loop at a better angle and facilitates easy anchor capturing of the anchor loop.

The utility loop is then used to pull the anchor loop through the AIGHL (
Fig. 4-10

). As the utility loop pulls the anchor loop through the AIGHL, the attached anchor is brought down the anterior inferior cannula while being controlled with the threaded inserter rod.

5. Loop Capture and Anchor Insertion

After the anchor loop has passed through the AIGHL, one strand of the anchor loop is captured or snagged in the channel at the tip of the anchor (
Fig. 4-11

). When the metallic knotless anchor is used, the anchor is rotated so the arc positioned inside the anchor loop is facing the utility loop. The anchor is then inserted and tapped into the glenoid drill hole to the desired depth to achieve appropriate tissue tension (
Fig. 4-12

).

6. Loop-Anchor Repair Tensioning and Completion

Depth of anchor insertion is determined by observing the ligament approximation to the glenoid and by intermittently pulling the utility loop to test the tension of the anchor loop during insertion. The anchor should not bottom out in the drill hole. Overtensioning can cause the anchor loop to tear through the ligament. Once this has been completed, the AIGHL is noted to shift superiorly and securely approximate to the glenoid rim in a low-profile manner (
Fig. 4-13

). The inserter rod is removed, and suture passage, anchor insertion, and tensioning are repeated for the remaining glenoid drill holes.

7. Closure

Standard closure of the portals is performed.

PEARLS AND PITFALLS

Several Techniques can Facilitate Capture of the Anchor Loop    •    For the inferior two anchors, pass the suture loop from the articular side of the ligament to the extra-articular side. For the superior anchor, pass the suture loop in the opposite direction.    •    Use the utility loop through the anterior superior portal to guide and manipulate the anchor loop to the anchor notch and ease loop capture ( Fig. 4-14 ).    •    During insertion of the anchor, periodically pull the utility loop to test the tension of the anchor loop.    •    Remember, it is critical not to torque the drill in determining hole placement. This can cause difficulty in placing the anchor; undue tissue tension that did not distort the drill could distort the inserter rod and lead to an inability to line up the anchor with the drilled hole. Placement of the Utility Loop and Anchor Loop in the Aighl is Critical    •    Suture placement should be inferior to the glenoid drill hole so that a superior shift of the ligament is achieved as the anchor is inserted into the drill hole.    •    The anchors are inserted in the most inferior hole first, progressing to the most superior hole. Avoid breakage of the anchor loop    •    Several anchor loop configurations can lead to loop breakage with the metallic anchor and should be avoided.    •    One arc must be passed through the anchor loop before anchor insertion; otherwise, the anchor loop will be cut on insertion into the bone ( Fig. 4-15 ).    •    The anchor loop must pass directly from the base of the anchor into the ligament. If the loop is wrapped around the body of the anchor, the anchor loop will be at risk of being cut by the closing anchor arc as the anchor is inserted into bone (Figs. 4-16 and 4-17 [16] [17]).    •    The utility loop can be pulled on to hold the anchor loop safely away from the arc during primary anchor insertion. Tension is relaxed once the arcs have entered the bone. Figure 4-14  A, The utility loop is pulled out the anterosuperior portal to orient the anchor loop at a better angle with respect to the anchor and thus facilitate loop capture. B, Loop capture is more difficult when the loop is pulled toward the same portal as the anchor.  (Redrawn from Thal R. Knotless suture anchor fixation for shoulder instability. In Miller MD, Cole BJ, eds. Textbook of Arthroscopy. Philadelphia, Elsevier, 2004.) Figure 4-15  One anchor arc has not been passed through the anchor loop and will cut the anchor loop when the anchor is inserted into bone.  (Redrawn from Thal R. Knotless suture anchor: arthroscopic Bankart repair without tying knots. Clin Orthop 2001;390:46-47.) Figure 4-16  The anchor loop is incorrectly wrapped around the anchor.  (Redrawn from Thal R. Knotless suture anchor: arthroscopic Bankart repair without tying knots. Clin Orthop 2001;390:46-47.) Figure 4-17  The anchor loop is incorrectly wrapped around the anchor.  (Redrawn from Thal R. Knotless suture anchor: arthroscopic Bankart repair without tying knots. Clin Orthop 2001;390:46-47.)

Postoperative Considerations

Follow-up

•

7 to 10 days for initial postoperative evaluation

Rehabilitation

	•	0-4 weeks: Use of a sling, with pendulum exercises, range-of-motion exercises of the shoulder and elbow, and isometric exercises of the forearm. External rotation is limited to neutral.
	•	4 weeks: Progressive active and passive range-of-motion exercises are begun; external rotation is limited to 45 degrees; isometric deltoid and periscapular exercises are begun.
	•	6 weeks: Progression to full, active range of motion is allowed.
	•	8 weeks: Resistive training with the use of isotonic and isokinetic modalities is performed in a progressive manner with no limitation on the patient.
	•	Return to contact and overhead sports is not allowed until 5 months postoperatively.

Complications

	•	Traumatic redislocation
	•	Incomplete healing of labral repair
	•	Infection
	•	Arthrofibrosis
	•	Anchor loop breakage secondary to improper anchor loop positioning

Results

After arthroscopic Bankart repair with the knotless suture anchor, increased superior capsular shift is attained compared with a standard suture anchor, as the knotless anchor pulls the ligament into the drill hole (
Fig. 4-18

). The problems associated with tying knots, knot loosening, and complex suture management are eliminated. Suture strength is improved compared with standard suture anchors. Furthermore, satisfactory results are attained with a low recurrence rate, minimal loss of motion, and reliable functional return, even in contact and collision athletes (
Table 4-1

). The recurrence rate was higher in patients 22 years old or younger.

Clinical Results
Author	Followup	Outcome
Thal[2] (2001)	29-month average	21 of 22 (96%) successful
Thal et al[3] (2004)	2-year minimum (range: 2-7 years)	67 of 72 (93%) successful
Garafalo et al[1] (2005)	43 months (range: 36-48 months)	18 of 20 (90%) successful

Biomechanical Results
Author	Parameters Tested	Results
Thal[2] (2001)	Suture breakage	Knotless anchor with statistically higher failure load (P < .0001)
	Bone pullout of anchor	Increased anchor pullout force in knotless anchor not significant (P = .195)
	Average capsular shift	Bankart repair: 4.33 mm
		Barrel stitch repair: 6.04 mm
		Plication repair: 6.50 mm[*]
		Knotless repair: 6.79 mm[*]