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). Overall, the whip stitch took on average 1 min 25 sec whereas the WhipLock took 2 min 20 sec (p=.001).
For whip stitch constructs, no differences were found between Users and all stitches were biomechanically equivalent. Correspondingly, for WhipLock stitches, no differences were found between Users and all suture constructs were likewise biomechanically equivalent. Averages for peak-to-peak displacement (mm), stiffness (N/mm), and ultimate failure load (N) are presented in Table 1. Moreover, when the two stitch methods were compared, the WhipLock constructs significantly increased stiffness by 25% (p <.001), increased ultimate failure load by 35% (p<.001) and reduced peak-to-peak displacement by 55% (p=.001). The common mode of failure for grafts with whip stitch failed by suture pullout from tendon (18/24), where a few instances occurred by suture breakage (6/24). Tendon grafts with WhipLock stitch commonly failed by suture breakage (22/24), where two instances of combined tendon tear and suture breakage were noted.
DISCUSSION: The WhipLock stitch significantly increased average construct stiffness and ultimate failure load, while significantly reducing the peak-to- peak displacement compared to the whip stitch. These added strength benefits of the WhipLock stitch took 55 seconds more to complete than the whip stitch. No statistically significant difference in biomechanical performance was found between the Users. Data suggests equivalent stitch performance regardless of the time to complete stitch and surgeon training level.
SIGNIFICANCE/CLINICAL RELEVANCE: Clinically, having a suture needle device available which can be used to easily perform different constructs including one with significant strength advantages regardless of level of experience is of benefit.
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Biomechanical Properties of Various Surgical Suture Needles in a Cadaveric Quadriceps Tendon Model
INTRODUCTION: Quadriceps tendon autografts have experienced a rapid rise in popularity for anterior cruciate ligament (ACL) reconstruction due to advantages in graft sizing and potential improvement in biomechanics. While there is a growing body of literature on use of quadriceps tendon grafts, deeper investigation into the biomechanical properties of stitch techniques in this construct has been limited. The purpose of this study was to evaluate the performance of a novel suture needle against different conventional suture needles by comparing the biomechanical properties of two commonly used stitch methods, a whip stitch, and a locking stitch in quadriceps tendon. It was hypothesized that the new device would be capable of creating both whip stitches and locking stitches that are biomechanically equivalent to similar stitch techniques performed with conventional needle products.
METHODS: This was a controlled biomechanical study. 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. For Group 1, the whip stitch as well as the locking whip stitch were performed with a novel 2-part needle. For Group 2, the whip stitch was performed with loop suture needle and the locking stitch was krackow with a curved needle. Similarly, for Group 3, the whip stitch was performed with loop suture needle and the locking stitch was krackow with a curved needle (Figure 1). Cyclical testing was performed using a servohydraulic testing machine (MTS Bionix) equipped with a 5kN load cell. A standardized length of tendon, 7 cm, was coupled to the MTS actuator by passing it through a cryoclamp cooled by dry ice to a temperature of -5°C (Figure 2). All testing samples were then 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 total elongation (mm), stiffness (N/mm), ultimate failure load (N) and failure mode. Data are presented as averages plus/minus standard deviation. A one-way analysis of variance (ANOVA) with a Tukey pairwise comparison post hoc analysis was used to evaluate differences between the various stitching methods. Statistical significance was set at P = .05.
RESULTS SECTION: For the whip stitch methods, the total elongation was found to be equivalent across all methods (W: 36 ± 10 mm; A: 32 ± 18 mm; B: 33 ± 8 mm). The stiffness of Company A (103 ± 11 N/mm) method was significantly larger than Company W (64 ± 8 N/mm; p=.001), whereas stiffness of whip stitch by Company W was equivalent to Company B (80 ± 32 N/mm). The ultimate failure load was equivalent across all whip stitch methods (W: 379 ± 31 mm; A: 412 ± 103 mm; B: 438 ± 63 mm). For the locking stitch method, the total elongation (W: 26 ± 10 mm; A: 14 ± 2 mm; B: 29 ± 5 mm), stiffness (W: 75 ± 11 N/mm; A: 104 ± 23 N/mm; B: 79 ± 10 N/mm) and ultimate load (W: 343 ± 22 N; A: 369 ± 30 N; B: 438 ± 63 N) were found to be equivalent across all methods. The failure mode for all groups is in Table 1. The common mode of failure across study groups and stitch configuration was suture breakage. However, the whip stitch from Company A and Company B had varied failure modes.
DISCUSSION: Products from the three manufacturers were found to produce biomechanically equivalent whip stitches and locking stitches with respect to elongation and ultimate failure load. The only significant difference observed was that the whip stitch created with Company A’s product had a higher stiffness than Company W’s product, which could have been due to differences in the suture material. In this cadaveric quadriceps tendon model, it was shown that when using Company W’s novel two-part suture needle, users were capable of creating whip stitches and locking stitches that achieved equivalent biomechanical performance compared to similar stitch techniques performed with conventional needle products. A failure mode limited solely to suture breakage for methods completed with Company W’s needle product suggest a reliable suture construct with limited tissue damage.
SIGNIFICANCE/CLINICAL RELEVANCE: Having a suture needle device with the versatility to easily perform different stitching constructs may provide surgeons an advantage needed to improve clinical outcomes. The data presented illustrates a strong new suture technique that has equivalent performance when compared to conventional needle devices and has promising applications in graft preparation for ligament and tendon reconstruction.
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- Award ID(s):
- 2112103
- NSF-PAR ID:
- 10398743
- Date Published:
- Journal Name:
- Transactions of the annual meeting of the Orthopaedic Research Society
- ISSN:
- 0149-6433
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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