Search for: All records

Background:One challenge surgeons face when using certain suture knot techniques is where the forces concentrate along the central axis of the tissue, making the suture knot prone to failure due to suture pull-through and tissue shredding. New reinforcement techniques have been developed (suture tape augmentation) and are becoming popular to minimize tissue damage. Purpose:To assess biomechanical performance of whipstitch reinforcement techniques (locking stitch method or additional suture material) in human cadaveric semitendinosus tendons (STs). Study Design:Controlled laboratory study. Methods:A total of 42 STs were harvested and divided into 6 groups consisting of a standard whipstitch and varying reinforcement techniques based on stitch pattern (whipstitch [WS], whipstitch through tag [WT], locking whipstitch [WL], or locking whipstitch through tag [WLT]), and products from varying manufacturer samples were preconditioned and then loaded from 50 to 200 N at 1 Hz for 500 cycles, followed by load to failure. Elongation, stiffness, ultimate load, and failure mode were compared across groups. Results:No significant differences were observed between whipstitch groups WS₁and WS₂. Addition of suture material for reinforcement (WT₂) significantly improved biomechanical performance across all metrics compared with WS₂. Reinforcement using a new locking whipstitch method (WL) resulted in significant increase in ultimate load compared with WS₁. All reinforcement groups (WL, WT₁, WT₂, and WLT) achieved a similar level of biomechanical performance, with no significant differences across any metric. Addition of a second reinforcement (WLT) did not significantly enhance biomechanics beyond those achieved with a single reinforcement (WL). The failure mode for no-reinforcement groups was tissue pull-through, while reinforcement groups utilizing either material or locking method failed from suture breakage. Conclusion:Whipstitch alone offers limited biomechanical security, but reinforcement with either a locking method or additional suture material significantly enhances biomechanical performance. Clinical Relevance:Reinforcement may help limit tissue damage. The locking whipstitch method offers a promising alternative to reinforce a stitch with relatively less suture material. 

INTRODUCTION: Repair and reconstruction of torn ligaments and tendons are commonly performed surgical procedures by orthopaedic surgeons, occurring at multiple locations in the body, such as the elbow or the knee for anterior cruciate ligament (ACL). Suturing is a critical step in the procedure, and although advancements in suturing have been made, residual laxity and graft failure at the suture site are challenges that still prevail. The whip stitch is one of the most popular suturing methods. However, a major drawback with this technique is that it concentrates the force along the central axis of the tissue, making it prone to failure due to suture pull-through and tissue shredding. New whip stitch reinforcement techniques have been developed, and the introduction of suture tape augmentation or “tags” have become popular to minimize tissue damage. However, the introduction of additional foreign material has increased concerns of suture burden. The purpose of this study was to assess the biomechanical performance of different whip stitch reinforcement techniques by comparing elongation, stiffness, and failure load across products developed by two different manufacturers. METHODS: This was a controlled biomechanical study that utilized 21 matched pair cadaveric knees. Specimens were dissected, and 40 semitendinosus tendons were harvested in preparation for stitching. All tendons were standardized to the same length and were randomized into six test groups varying in reinforcement techniques based on company (Arthrex [A], Winter Innovations [W]), number of reinforcements (0, 1, 2), and type of reinforcement (locking method [L], material [M]). Baseline groups had no reinforcements and consisted of a standard whip stitch (WS) method with products from both companies. For single reinforcement groups, the material consisted of a thicker suture tape that was laid on top of the tissue and stitched through. The locking method groups employed a WhipLock pattern, which creates a locking suture mechanism (like a Krackow) but requires half as many needle passes through the tissue (like a whip stitch). The final group combined both reinforcement techniques (locking method and material). Stitching was performed by a fellowship-trained orthopaedic surgeon and a physician assistant. For instrumentation, tendons were clamped to a graft preparation stand and five evenly placed stitches were completed at the proximal end. Cyclical testing was performed using a servohydraulic testing machine (MTS Bionix) equipped with a 5kN load cell. Each sample was coupled to the MTS actuator by passing it through a cryolamp cooled by dry ice to -5ᵒC. All testing samples were pre-conditioned to normalize viscoelastic effects by cyclical loading to 25-100 N for three cycles, followed by static hold at 50N for 1 min. Samples were then loaded to 50-200 N at 1 Hz for 500 cycles. If samples survived, they were ramped to failure at 20 mm/min. Displacement and force data were collected throughout testing. Metrics of interest were stiffness (N/mm), ultimate failure load (N), peak-to-peak displacement (mm), elongation (mm), and failure displacement (mm), and failure mode (tissue pull-through vs. suture break). To characterize suture material burden, three independent synthetic grafts were prepared for each of the 0 and 1 reinforcement groups. Sutures were trimmed at the end of the tissue and then removed from the tendon. The weight of each suture construct was taken, and a pooled weight was recorded and then averaged across the 3 samples to obtain the suture weight (g) for each group. Data are presented as averages plus/minus standard deviation. A one-way ANOVA with a Tukey HSD for post hoc analysis was used to evaluate differences between groups. Statistical significance was set at P = .05. RESULTS: For the zero reinforcement groups, no significant differences were observed between W0 and A0 for elongation (p=.479), stiffness (p=.769), ultimate failure load (p=.387), or failure displacement (p=.899). However, it was determined that A0 had significantly larger peak-to-peak displacement compared to W0 (p=.00156). The addition of suture material reinforcement (A1-M) significantly improved biomechanical performance across all metrics compared to A0, where elongation was reduced (p=.001), peak-to-peak displacement decreased (p=.001), stiffness increased (p=.001), ultimate failure load increased (p=.001), and failure displacement decreased (p=.001). While the biomechanical performance of W0 improved with the addition of suture material (W1-M), only the decrease in failure displacement was found to be significantly different (p=.008). The reinforcement locking method W1-L resulted in a significant increase in ultimate failure load (p=.018) and decrease in failure displacement (p< .001) compared to W0. However, decreases in elongation, decreases in peak-to-peak displacement, and increases in stiffness were not statistically significant. When comparing across A0 and W1-L, it was determined that W1-L had significantly less elongation (p=.0019), less peak-to-peak displacement (p< .001), increased stiffness (p=.012), increased ultimate failure load (p< .001) and decreased failure displacement (p< .001). Comparing across all the reinforcement groups (W1-L, W1-M, A1-M, W2-L,M), no significant differences were concluded across elongation, peak-to-peak displacement, stiffness, ultimate failure load or failure displacement. Interestingly, no significant differences were observed across all metrics when comparing W1-L and the addition of the second reinforcement of suture material (W2-L,M). The failure mode for whip stich method with no reinforcement (W0, A0) was suture pull-through tissue across a majority of the grafts. Generally, additional reinforcement groups utilizing W1-L, W1-M, and W2- L,M failed from suture breakage, however A1-M still resulted in suture pull-through. Within 1 reinforcement groups, the locking method W1-L had approximately 40% less suture by weight (0.050g) than the material groups W1-M (0.093g) and A1-M (0.080g). DISCUSSION: The use of whip stitch reinforcement, whether it is by a locking method or additional suture material, may help reduce the rate of failure and damage to tissue. In this cadaveric semitendinosus tendon model, it was shown that performing a whip stitch without reinforcement offered limited biomechanical security. The addition of reinforcement material enhanced the biomechanical properties associated with the graft significantly minimizing the failure displacement, however the effects varied depending on manufacturer. SIGNIFICANCE/CLINICAL RELEVANCE: The WhipLock reinforcement method demonstrated similar biomechanical properties when compared to material-reinforced semitendinosus grafts but required less suture material. The novel two-part needle from company W shows promise as it enables both a traditional whip stitch and the reinforced WhipLock method, which provides reinforcement without added suture burden of reinforcement materials.