Suture Anchors— Update 1999
Abstract & Commentary
Synopsis: Screw-type suture anchors continue to have higher values for pullout strength than newer generation nonscrew designs; nonetheless, the new designs are noted to have increasing pullout strength with the difference between threaded types less distinct. New biodegradable anchors composed of poly L-lactic acid demonstrate loads to failure similar to other nonabsorbable anchors in their class.
Source: Barber FA, Herbert MA. Suture anchors—Update 1999. Arthroscopy 1999;15(7):719-725.
Suture anchors continue to be frequently used in the shoulder, knee, and ankle as well as other joints in the body. Multiple suture anchor devices, designs, and techniques of placement are available with a myriad of indications and uses. Barber and Herbert have evaluated the pullout strength of newly developed suture anchors with their well-established porcine model. They have reported on similar pullout studies in three previous publications in 1995, 1996, and 1997. This current study allows comparison to the previously tested anchors since they used the same experimental model. Load to failure was tested using tensile stress parallel to the axis of insertion with pullout applied at 12.5 mm per second using an Instron 1321 machine. Interestingly, the screw-type suture anchors continue to have greater pullout strength than most nonscrew designs but, as Barber and Herbert noted, the distinctions between these are becoming less apparent with further design modifications.
Newer, biodegradable suture anchors most commonly used poly L-lactic acid, which Barber and Herbert note is longer lasting and less inflammatory than previously used polymers. These anchors demonstrated similar strengths to metal anchors in their class. Once again, all of the suture anchors tested were stronger than the suture for which they were designed.
Comment by Robert C. Schenck, Jr., MD
This is another of a well-designed series of studies by Barber and colleagues evaluating the pullout strength of multiple suture anchors, thus allowing the clinician to compare those newly produced to those previously tested and published in the Journal of Arthroscopy.1,2,3 The study design is well detailed and the information is extremely useful for the clinician, as it allows for an independent, reproducible assessment of pullout strength of suture anchors.
Orthopaedic surgeons are bombarded by multiple implant design changes. However, this study helps the surgeon determine whether newer is indeed better. Barber and Herbert do not focus on biocompatibility of the anchors, which may be an issue for the new absorbable anchors, but instead discuss only the mechanical performance based upon pullout strength. As Barber and Herbert note, ideally the suture anchor selection should not be the weakest link in the repair of soft tissue to bone. Good pullout strength does not substitute for poor technique. Lastly, this paper provides a photographic inventory of the newer anchors available to assist the surgeon in identification.
References
1. Barber, FA, et al. The ultimate strength of suture anchors. Arthroscopy 1995;11:21-28.
2. Barber, FA, et al. Suture anchor strength revisited. Arthroscopy 1996;12:32-38.
3. Barber, FA, et al. Internal fixation strength of suture anchors—update 1997. Arthroscopy 1997;13:355-362.
Suture anchor failure strength is best related to:
a. screw vs. modular design.
b. suture strength.
c. anchor composite material.
d. screw thread taper.
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