PEEK Anchor

What is an anchoring suture?

Suture anchors are broadly used for attaching soft tissue (e.g., tendons, ligaments, and meniscus) to the bone and have become essential devices in sports medicine and during arthroscopic surgery. As the usage of suture anchors has increased, various material-specific advantages and challenges have been reported. As a result, suture anchors are continually changing to become safer and more efficient. In this ever-changing environment, it is clinically essential for the surgeon to understand the key characteristics of existing anchors sufficiently.

The use of suture anchors has revolutionized orthopedic surgery because it allows for simple and efficient fixation of soft tissue (e.g., tendons and ligaments) to the bone in both open and arthroscopic surgery around the shoulder, elbow, wrist, and lower limb joints.) Shoulder surgery particularly has experienced a significant change in the type of techniques used from open repair of the rotator cuff and labrum using screws, washers, transosseous sutures, and staples to arthroscopic repair using suture anchors.

The primary function of the suture anchor is to attach tissue at the proper site and maintain its position without loosening or excessive tension until physiologic healing is accomplished. An ideal suture anchor is easy to handle, maintains enough pull-out strength, prevents suture abrasion, and is absorbable without resulting in any reactions as the material dissolves.) Various types of anchors have been developed, and designs of anchors have evolved over the recent decade to maximize their effectiveness in creating a firm tendon-to-bone repair.

Polyetheretherketone

Because some biodegradable anchors can be absorbed too quickly, the development of biostable anchors was pursued. Such a biostable anchor—a polyetheretherketone (PEEK) polymer—is obtained by dialkylation of bisphenol salts )

PEEK is increasingly becoming used in tribological components because of its excellent performance. PEEK materials showed high strength, strong mechanical properties, good wear- and heat-resistance, and excellent chemical and biological resistance. Therefore, it has many other applications in engineering and medicine.) PEEK also offers advantages, such as good postoperative imaging and stable fixation, and no complications associated with polymer degradation. Importantly, the major problem with PEEK has been shown to be poor osseointegration. Overall, however, the development of PEEK anchor has led to the adoption of biocomposite materials that may support osteoconductive ingrowth.)

BIOCOMPOSITE SUTURE ANCHOR

Biocomposite suture anchors are composed of both a biodegradable polymer material and a bone formation-promoting bioceramic material. The most commonly used bioceramic is beta-tricalcium phosphate (β-TCP); others include hydroxyapatite, calcium sulfate, and calcium carbonate.) TCP is widely used in orthopedic surgery to fill bone defects because (1) it has a mineral content similar to that of human bone, (2) its macro-porosity and micro-porosity is osteoconductive, and (3) it has excellent biocompatibility and mechanical resistance. Unlike β-TCP, hydroxyapatite is a natural mineral substance with an affinity to bones and is highly biocompatible since it is similar to a mineral component of teeth and bones of mammals.) Generally, hydroxyapatite-based bone substitute materials are considered nonabsorbable or have much lower degradation rates than β-TCP (Fig. 3))

ALL-SOFT SUTURE ANCHOR

Solid type suture anchors (e.g., metal and polymer) have been studied extensively and found to be sufficient for maintaining physiologic loads at soft tissue to bone junctions. Usually, these solid type anchors need surgical preparation of the bony footprint site (decortication, punching, or drilling) that may cause bone loss because of the grounding piece's volume.)

All-soft suture anchors (ASAs) were developed to minimize complications and invasiveness related to the use of solid type anchors. These ASAs consist of one or more ultra-high-molecular-weight polyethylene (UHMWPE)-containing sutures.

The ASAs typically consist of a sleeve or tape made of suture material through which the UHMWPE-containing suture is woven. This fixation mechanism differs compared with screw-type suture anchors. When the ASA is inserted into the bone and the primary suture is pulled, the sleeve or tape is cinched up to compress against the overlying cortical bone creating a “ball” that works as the anchor. It allows the suture anchor to be placed in a tunnel with a smaller diameter (1–3 mm), thereby preserving bone and hypothetically allowing for more bone preservation, which may be particularly beneficial due to limited bone stock at the glenoid rim or acetabulum. Also, even if an anchor failure occurs, joint damage may be minimized because of the soft anchor body.)