Strength of Meniscal RepairsVarious repair systems have been devised for meniscal tears of the knee. Small tears may be repaired with sutures. In some cases, an absorbable implant such as the Stinger, Arrow, or Meniscal Screw is applied. For large tears, surgeons often use both. Sutures are used in places easy to reach. More difficult areas are repaired using the implant.
In this study, German researchers measure the strength of meniscal tears repaired using a vertical suture made out of braided steel wire. Human cadavers were used to test the distraction forces on the suture.
The study was done in a lab where the scientists could make a cut in the meniscus. The incision was designed to mimic a naturally occurring bucket-handle tear. Bucket handle tears divide the meniscus in two pieces horizontally. This leaves the outer portion able to lift up away from the rest of the cartilage. The effect is much like a bucket handle lifts up from the edge of the bucket.
Tiny load sensors were connected to a wire along the edge of the repaired meniscus. The knees were tested at different knee joint angles from zero to 120-degrees of knee flexion.
Weight load and degree of internal or external rotation were also measured. The scientists were looking for the load it would take to pull out the suture. This is called the pull-out strength.
The authors report distraction forces on the meniscus were never enough to cause damage to the repaired meniscus. The average force across the tear was never more than five N (newtons). Five newtons are equal to one pound.
The conclusion of this study was that repair systems for meniscus tears can't be tested just by relying on distraction forces. It's likely that shear forces (not measured here) are a major factor in meniscal tears. This study just looked at the medial meniscus. Future studies must measure the forces on a torn lateral meniscus as well.
Roland Becker, MD, et al. Distraction Forces on Repaired Bucket-Handle Lesions in Medial Meniscus. In The American Journal of Sports Medicine. December 2006. Vol. 34. No. 12. Pp. 1941-1947.
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