What Happens When Absorbable Meniscal Repair Devices Resorb?
Abstract & Commentary
Synopsis: PDS-based implants lost holding strength by 12 weeks, while PLA-based devices retained the same strength over 24 weeks.
Source: Arnoczky SP, Lavagnino M. Tensile fixation strengths of absorbable meniscal repair devices as a function of hydrolysis time. Am J Sports Med. 2001;29(2):118-123.
All-inside meniscal repair techniques have been popularized by the availability of various absorbable implants. However, little is known about how these implants behave as they start to resorb. Dr. Arnoczky, who is well known for his studies on pull-out strength for repairs of the meniscus, performed an experiment assessing the effects of hydrolysis on these various devices.
All of the commonly used and currently available implants were compared in a bovine, fresh, meniscal model. A standardized tear was made and then repaired, with one of the implants before being soaked in a saline buffer in vitro for various time points up to 24 weeks. Load to failure was assessed at each time point and compared to the initial fixation strength.
Arnoczky and Lavagnino found that the initial repair strength of the Bionx meniscal arrow was basically equal to that of the vertical mattress suture. This implant maintained its strength over the entire testing period of 24 weeks. The same was said for the other PLA-based implants including the Linvatec BioStinger and the Innovasive Clearfix screw, although both of these had only approximately two-thirds of the holding strength of the Bionx arrow. The S-D-sorb staple had the weakest holding power, and this was nearly completely gone shortly after 12 weeks. Similarly, the PDS-based implants, including the Mitek Meniscal Repair System and the 2-0 PDS suture, both lost all holding power by 12 weeks as they more rapidly absorbed. Also, they noted that culture time did not affect the integrity of the meniscal tissue, as initial load to failure was the same for a new tear in a meniscus that had been soaked for the same 24 weeks.
Comment by David R. Diduch, MS, MD
Science is gradually catching up with the popularity for all-inside meniscal repair techniques. There is still a paucity of clinical papers or animal studies with results for all of these implants that are available. Arnoczky is to be congratulated for objectively evaluating these implants and specifically examining how they behave as they start to resorb. As they are all designed to resorb, this is an important issue that needs to be addressed.
An important finding is that the PDS-based implants are basically gone before 3 months. This may be inadequate for healing. Another important finding is that the PLA-based implants do not lose strength up to basically 6 months. This is another important finding but has to be balanced against concerns that these implants remain in the joint an extended period of time and can cause secondary problems if they became loose or brush up against the chondral surface. The pull-out strength for the arrow was superior to the other implants tested and basically equivalent to the vertical mattress suture. Whether this is clinically significant is unproven. A major unanswered question is how strong is strong enough to hold the meniscus repair and allow healing. Other unanswered questions are: how long does healing take and how long must these devices be present? Certainly, the answer to that varies for an isolated meniscal repair in which the tear may only partially heal at best, and permanent implants such as suture should be optimal, compared to concurrent ACL reconstruction with the ideal healing environment. One previous study demonstrated that the repair strength of the meniscus is only 26% of normal at 12 weeks.1 This prompts me to move toward permanent, nonabsorbable suture material for isolated meniscal repairs when the healing environment is suboptimal. In my mind, these absorbable and easy-to-use all-inside devices are best reserved for when an ACL reconstruction is performed concomitantly and the healing environment is optimal.
Reference
1. Roeddecker K, et al. Meniscal healing: A biomechanical study. J Surg Res. 1994;56:20-27.
You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content