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This content will become publicly available on February 11, 2026

Title: Evaluation of Whip Stitch Reinforcement in Cadaveric Semitendinosus Grafts
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.  more » « less
Award ID(s):
2304269
PAR ID:
10640633
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
Orthopaedic Research Society
Date Published:
Format(s):
Medium: X
Location:
Phoenix, Arizona
Sponsoring Org:
National Science Foundation
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  1. ; ; ; ; (, Transactions of the annual meeting of the Orthopaedic Research Society)
    INTRODUCTION: In practice, the use of a whip stitch versus a locking stitch in anterior cruciate ligament (ACL) graft preparation is based on surgeon preference. Those who prefer efficiency and shorter stitch time typically choose a whip stitch, while those who require improved biomechanical properties select a locking stitch, the gold standard of which is the Krackow method. The purpose of this study was to evaluate a novel suture needle design that can be used to perform two commonly used stitch methods, a whip stitch, and a locking stitch, by comparing the speed of graft preparation and biomechanical properties. It was hypothesized that adding a locking mechanism to the whip stitch would improve biomechanical performance but would also require more time to complete due to additional steps required for the locking technique. METHODS: Graft preparation was performed by four orthopaedic surgeons of different training levels where User 1 and User 2 were both attendings and User’s 3 and 4 were both fellows. A total of 24 matched pair cadaveric knees were dissected and a total of 48 semitendinosus tendons were harvested. All grafts were standardized to the same size. Tendons were randomly divided into 4 groups (12 tendons per group) such that each User performed analogous stitch on matched pair: Group 1, User 1 and User 3 performed whip stitches; Group 2, User 1 and User 3 performed locking stitches; Group 3, User 2 and User 4 performed whip stitches; Group 4, User 2 and User 4 performed locking stitches. For instrumentation, the two ends of tendon grafts were clamped to a preparation stand. A skin marker was used to mark five evenly spaced points, 0.5 cm apart, as a guide to create a 5-stitch series. The stitches were performed with EasyWhip, a novel two-part suture needle which allows one to do both a traditional whip stitch and a locking whip stitch, referred to as WhipLock (Figure 1). The speed for graft preparation was timed for each User. Biomechanical testing was performed using a servohydraulic testing machine (MTS Bionix) equipped with a 5kN load cell (Figure 2). A standardized length of tendon, 10 cm, was coupled to the MTS actuator by passing it through a cryoclamp cooled by dry ice to a temperature of -5°C. All testing samples were pre-conditioned to normalize viscoelastic effects and testing variability through application of cyclical loading to 25-100 N for three cycles. The samples were then held at 89 N for 15 minutes. Thereafter, the samples were loaded to 50-200 N for 500 cycles at 1 Hz. If samples survived, they were ramped to failure at 20 mm/min. Displacement and force data was collected throughout testing. Metrics of interest were peak-to-peak displacement (mm), stiffness (N/mm), ultimate failure load (N) and failure mode. Data are presented as averages and standard deviations. A Wilcoxon signed-rank test was used to evaluate the groups for time to complete stitch and biomechanical performance. Statistical significance was set at P = .05. RESULTS SECTION: In Group 1, the time to complete the whip stitch was not significantly different between User 1 and User 3, where the average completion time was 1 min 13 sec. Similarly, there were no differences between Users when performing the WhipLock (Group 2) with an average time of 1 min 49 sec. In Group 3 (whip stitch), User 2 took 1 min 48 sec to complete the whip stitch, whereas User 4 took 1 min 25 sec (p=.033). The time to complete the WhipLock stitch (Group 4) was significantly different, where User 2 took 3 min and 44 sec, while User 4 only took 2 min 3 sec (p=.002). 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A total of 24 matched pair cadaveric knees were dissected and a total of 48 quadriceps tendons were harvested and tested. All tendon grafts were standardized to the same size. Samples were then randomized into the following groups, keeping the matched pairs together: (Group 1, n=16) consisted of Company W’s novel two-part suture needle design, (Group 2, n=16) consisted of Company A suture, and (Group 3, n=16) consisted of Company B suture. For each group, the matched pairs were categorized into subgroups to be instrumented with either a whip stitch or a locking stitch. Two fellowship-trained surgeons performed all stitching, where they each instrumented 8 tendon grafts per group. For instrumentation, the grafts were clamped to a preparation stand in accordance with the manufacturer’s recommendations for passing each suture needle. A skin marker was used to identify and mark five evenly spaced points, 0.5 cm apart, as a guide to create a 5-stitch series. 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