Anchors and Fixation Devices for Cuff Tears: What Is the State of the Art?


Chapter 10

Anchors and Fixation Devices for Cuff Tears


What Is the State of the Art?



F. Alan Barber

Introduction


Arthroscopic repair of the rotator cuff could not have advanced as rapidly as it has without improvements in the implants that allow fixation of the damaged tendon to bone. Suture anchors and high-strength sutures are essential to this technique. The suture and suture anchor’s function is to secure the tendon to the appropriate site without excessive tension or loosening until physiologic healing can occur. Conceptually, the ideal construct would perform this function in a minimally invasive manner, not create an adverse reaction in the surrounding tissue, disappear completely, and be replaced with normal bone. This ideal scenario is not currently attainable, but recent advances have made significant strides toward achieving this goal.

Brief History


Historically, rotator cuff tendons were attached to bone using bone tunnels through which the sutures were passed and tied. Awls or drills were used to create these tunnels, and the sutures were tied over the bone bridge. While applicable to open procedures, this is very difficult in arthroscopic repairs. Additionally, several studies document the superiority of suture anchors to bone tunnels in providing higher and more consistent failure loads, avoiding suture fraying, and facilitating superior knot tying.

Suture anchors were initially metal (e.g., stainless steel and titanium) and threaded with braided polyester suture. Nonmetallic implants (e.g., polyethylene, biodegradable poly L-lactic acid; PLLA) were introduced starting in the mid-1990s. Based on the success of the initial biodegradable PLLA, stereoisomers and copolymers of lactic acid were subsequently developed. The most advanced biodegradable implants are now made from biocomposite materials that combine biodegradable polymers with a bioceramic such as beta-tricalcium phosphate (β-TCP).

More dramatic than the changes and improvements in suture anchor materials is the change in suture material. Braided polyester suture, commonly associated with the initial suture anchors, has been replaced by sutures containing ultra-high-molecular-weight polyethylene (UHMWPE). The increased strength, ease of handling, and reduced breakage associated with these UHMWPE-containing sutures may be the single greatest recent advance in the arthroscopic repair of rotator cuff tendon repair.

Surgical Technique Setup


Equipment


Suture Anchors


Design




  1. • The design for an effective rotator cuff tendon suture anchor should have several characteristics. It should secure the sutures into the bone, not pull out of the bone when subjected to cyclic loading, be easy to place arthroscopically, facilitate arthroscopic knot tying or securing the suture, have at least three sutures, and not cause long-term morbidity. Designs have changed over time, and rotator cuff tendon repair suture anchors currently have several common characteristics: triple-loaded with braided, high-strength sutures, fully-threaded screw-in designs, distal eyelets, and nonmetallic materials (Fig. 10.1).
  2. • Suture anchor designs vary and must be chosen for the specific insertion site and application.
  3. • The glenoid is smaller and denser than the greater tuberosity. Consequently, an anchor designed for the glenoid will not be as effective if used in a rotator cuff repair. It is helpful to classify rotator cuff anchors as medial row rotator cuff anchors and lateral row rotator cuff anchors.
  4. • Anchor size: with screw-in designs, both the outside and core diameters of the anchor are important. Larger anchors (6.5 mm outer diameter; OD) are not any stronger than 5.5 mm OD anchors. Smaller anchors (4.5 mm OD) are often just as strong and may work better than the larger anchors, especially in denser bone sites such as the lesser tuberosity (Fig. 10.2). This is partially because of fully threaded designs, improvements in thread pitch, and the increased surface area of the threads.
  5. • Anchor eyelet: eyelet location and shape influence anchor performance. Currently the clear trend is for a distal crossbar eyelet that allows tying sliding locking knots in all three sutures (Fig. 10.3). This type of eyelet is less likely to break and allows for arthroscopically reloading of the anchor with another suture if one breaks or is mistakenly “off-loaded.” The eyelet’s rotation relative to the suture can affect suture fretting and failure load. Therefore it is important to understand the position of the suture-eyelet interface before completely inserting the anchor into bone. Sometimes it is helpful to back out or advance the anchor a half turn to align the sutures and the crossbar perpendicularly to the direction of tissue passing.


image
FIG. 10.1 The Healix Advance BR triple-loaded suture anchor is an example of a rotator cuff tendon repair suture anchor that is triple-loaded with high-strength sutures, has a fully threaded screw-in design with a distal eyelet, and is nonmetallic. 
Copyright F. Alan Barber, MD.

image
FIG. 10.2 Rotator cuff tendon repair suture anchors typically come in various sizes. The Healix Advance anchors shown here have different diameters: 4.5, 5.5, and 6.5 mm. 
Copyright F. Alan Barber, MD.

image
FIG. 10.3 The current trend is for distal crossbar eyelets that allow the tying of sliding locking knots in all three sutures. 
Copyright F. Alan Barber, MD.

Medial Row, Lateral Row


Material Options




  1. • Currently many materials are available for the manufacture of suture anchors: metal, plastic, biodegradable, and suture. While the traditional metal anchors (stainless steel, titanium) are certainly less expensive than newer materials, they can create challenges during revision surgery and the treatment of infections, and can complicate imaging. They clearly document any adverse anchor placement. Current biodegradable anchors provide pullout strength comparable with metal anchors, will eventually degrade completely, and avoid problems during revision surgery or postoperative imaging.


  3. image
    FIG. 10.4 A double-row, suture-bridging rotator cuff repair in which the sutures from the medial row anchors are passed through the rotator cuff tendon as a mattress stitch, tied in a knot, and then fixed laterally in the knotless anchor to compress the tendon onto the greater tuberosity, restoring the footprint attachment. 
    Copyright F. Alan Barber, MD.

  4. • Biodegradable polymers currently used in suture anchors include polyglycolic acid (PGA), PLLA, stereoisomers of lactic acid including poly-D-L-lactic acid (PDLLA), and copolymers of lactide and glycolide (PLLA-co-PGA). Some degree of inflammation is inherent in any degradation process. The amount of inflammation is linked to the monomer volume released at any one time. The greater the rate of this degradation, the more clinically significant the inflammation can be. Although some reports of adverse inflammatory reactions exist, these are usually associated with the rapidly degrading stereoisomers of PLLA and not PLLA itself.

PLLA


PGA


Polyether Ether Ketone (PEEK)




  1. • PEEK, a nonabsorbable, biologically inert plastic, is also widely used in suture anchors. PEEK is a radiolucent, highly crystalline, thermoplastic material adaptable to a wide pH range from 60% sulfuric acid to 40% sodium hydroxide, melts at 343°C (662°F), and is found in many other applications including aerospace parts, pumps, and semiconductors. Confusion has developed among some surgeons regarding PEEK’s material nature because some manufacturers have misleadingly used the term “bio” in the name of PEEK anchors. These anchors are not biodegradable because they are made from PEEK.
  2. • All PEEK anchors are radiolucent and can be drilled through during a revision procedure. However, it may be difficult to remove all the small plastic shavings created during this process if they are thrown into the joint, creating concerns about the potential for abrasive injury to the articular cartilage.

Related posts:

Patient Positioning and Anesthesia for Rotator Cuff Surgery Arthroscopic Trillat Procedure for Recurrent Anterior Shoulder Instability With Associated Irreparable Rotator Cuff Tear Nonoperative Care of Rotator Cuff Disorders: Physical Therapy, Modalities, and Injectables SLAP II Tears: Evaluation and Surgical Techniques for Fixation Impingement Syndrome: Diagnosis and Management Shoulder Stiffness (Adhesive Capsulitis) With A Rotator Cuff Tear: How to Manage

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Mar 28, 2020 | Posted by in ORTHOPEDIC | Comments Off on Anchors and Fixation Devices for Cuff Tears: What Is the State of the Art?

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