Biodegradable Implants for Meniscal Repair
Abstract & Commentary
Synopsis: From the American Journal of Sports Medicine comes a report of 5 patients with complications from biodegradable "all-inside" meniscal repair systems including cyst formation, knee joint effusions, and femoral condylar injury.
Source: Tingstad EM, et al. Complications associated with the use of meniscal arrows. Am J Sports Med. 2001;29(1): 96-98.
Tingstad and colleagues describe 5 patients with complications from the use of a biodegradable (poly-L-lactic acid) meniscal repair device (Bionx—Blue Bell, Pa). Complications included 4 patients with recurrent cyst formation, including 1 patient with palpable objects noted subcutaneously along the medial joint line. All cysts resolved with aspiration and time. A fifth patient underwent an incidental arthroscopy 6 months post-repair and was noted to have femoral furrowing related to the heads of the meniscal arrows. Tingstad and colleagues note that the meniscal arrows were placed according to manufacturing guidelines (arrow length selection and impaction of the arrow), concluding that there may be a significant design problem. Tingstad et al were encouraged by the fact that the cyst formation appeared self-limiting. Clinically, the meniscal tears healed with the all-inside biodegradable devices.
Comment by Robert C. Schenck, Jr., MD
Meniscal repair has been an evolving technical process, from open, to arthroscopically assisted (inside-out, outside-in), to an all-arthroscopic "all-inside" technique. Several devices have been developed to repair a meniscus with such a technique in an attempt to avoid a posterior incision or portal. The most recent advancements have included various biodegradable arrows or tacks, which offer ease of insertion avoiding the need for intra-articular knot tying. Recently, in the October 2000 issue of Arthroscopy, 2 separate reports documented the incidence of chondral injury (reported by Tingstad et al, patient No. 5, above) due to the same meniscal arrow device with grooving of the articulating femoral condyle.1,2
To preface this discussion, I have no financial involvement with any of the meniscal repair device manufacturers. The true crux of the problem, in my opinion, lies not in the device shape or design, but in the biomaterial selection. PLLA is selected because of its stiffness and ability to produce a device that can indeed fix and hold the meniscal tear during the healing phase. In the case reports, the meniscus repair did indeed produce meniscal healing. Unfortunately, the time line of absorption has been reported to be more than 3 years for poly-L-lactic acid, and the long-term presence of the implant may be the underlying cause for joint surface injury. In a recent report by Martinek et al,3 a poly-L-lactic acid interference screw was removed 2.5 years after insertion, documenting the slow resorption of such a biodegradable material. Slow resorption time could be the Achilles heel when using such a material in which articular motion could result in hyaline cartilage contact and injury. Proper placement of any device is critical, and even the most ideal biomaterial improperly placed could scuff the knee joint. Ideally, and in my opinion, the device should resorb more quickly over a 2-4 month period to avoid such articular lesions, independent of the design. Use of other materials for meniscal repair with faster resorption times (ie, polydioxanone, PDS, Mitek Fastener System, Ethicon, Westwood, Mass: 5-week resorption time) may decrease the risk of chondral injury but may also affect mechanical properties and healing rates. Until more clinical studies are available that assess healing rates plus the incidence of complications, we really don’t know how long these devices need to stay around to do the job. Because these are case reports rather than clinical series, we also do not know the true incidence of such complications with these devices.
References
1. Anderson K, et al. Chondral injury following meniscal repair with a biodegradable implant. Arthroscopy. 2000;16(7):749-753.
2. Ross G, et al. Chondral injury after meniscal repair with bioabsorbable arrows. Arthroscopy. 2000;16(7): 754-756.
3. Martinek V, et al. The fate of the poly-L-lactic acid interference screw after anterior cruciate ligament reconstruction. Arthroscopy. 2001;17(1):73-76.
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