Mechanical Fixation of Meniscal Tears
Abstract & commentary
Synopsis: Suture repair offers the best mechanical strength for meniscal repairs. Bioabsorbable arrows can be used for arthroscopic (all-inside) technique, but certain pitfalls should be avoided.
Source: Boenisch UW, et al. Pull-out strength and stiffness of meniscal repair using absorbable arrows or Ti-Cron vertical and horizontal loop sutures. Am J Sports Med 1999;27: 626-631.
Boenisch and colleagues compiled a mechanical analysis of meniscal repair fixation. They tested pull-out strength and linear stiffness (ability to resist deformation) of suture repair vs. bioabsorbable meniscal arrows. They also compared vertical vs. horizontal sutures, different arrow lengths, and different angles of arrow insertion. The data presented demonstrate a mechanical advantage of suture fixation, and the strongest fixation is a vertical loop suture. The mean pull-out strengths of different repairs were recorded: vertical loop suture (2-0 Ti-Cron), 72N; horizontal loop suture (2-0 Ti-Cron), 68N; 16 mm arrows, 53N; 13 mm arrows, 39N; 10 mm arrows, 19N. The relative stiffness of the repairs was also recorded: vertical suture, 12 N; 16 mm arrows, 11 N; 13 mm arrows, 10N; horizontal sutures, 8N; and 10 mm arrows, 7N. Boenisch et al also noted that arrows placed on an angle or with only a few barbs crossing the tear were weaker. Boenisch et al conclude that a vertical loop suture has the highest pull-out strength and that "arrows most likely provide adequate stability for meniscal healing." This conclusion is based upon the stiffness of the longer meniscal arrows that were properly placed, as well as on unpublished clinical data.
Comment by Stephen B. Gunther, MD
This study highlights some well-known facts about meniscal repair and provides some important new data as well. It is well known that meniscal repair can be performed through arthroscopic, open, or arthroscopically assisted (outside-in, inside-out) techniques. It is also well known that the ideal host for meniscal repair is a peripheral, medial meniscal tear at the meniscosynovial junction (red-red zone) that is vertically oriented and associated with an anterior cruciate ligament (ACL) tear, which is then reconstructed.1 It is also well known that vertical sutures provide stronger fixation than horizontal sutures.2 This study, however, provides data comparing classic suture fixation techniques with a bioabsorbable meniscal arrow. Boenisch et al conclude that vertical loop suture fixation is the strongest, but they also surmise that properly placed arrows are probably sufficient for in vivo meniscal healing.
In this study, the pull-out strength of the vertical sutures was not significantly stronger than horizontal loop sutures. Also, the stiffness of vertical sutures was not significantly greater than 13 mm or 16 mm arrows. Thus, some of these differences are not statistically significant. The most important variable, however, is the necessary pull-out strength and stiffness for in vivo meniscal healing. Since there are no data that quantify the minimum pull-out strength and stiffness for healing of a meniscal tear, the clinician must use these mechanical data as an adjunct to current clinical results.
References
1. Cannon WD Jr, Vittori JM. The incidence of healing in arthroscopic meniscal repairs in anterior cruciate ligament reconstructed knees versus stable knees. Am J Sports Med 1992;20:176-181.
2. Raunest J, Derra E. Experimentelle Ergebnisse zur Biomechanischen Belastbarkeit der Meniscusnaht im Bereich der zone II. Unfallchirurg 1990;93:197-201.
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