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Pulvertaft Weave and Side-to-Side Techniques: A Stress-Strain Analysis on Ovine Tendons
Emily M Graham, MD
University of Michigan, Ann Arbor, MI
BackgroundRecent biomechanical studies advocate for the side-to-side technique (STS) over the traditional Pulvertaft weave technique (PT). However, current studies fail to explain these findings via mechanical means. Through stress-strain analyses, we hypothesized that the PT would demonstrate failure at similar global strains and stresses compared to the STS under uniaxial loading.
MethodsSimilarly sized fresh flexor and extensor ovine tendons were extracted from around the tibia to perform the PT and STS. A board-certified hand surgeon performed 3 coaptations of each technique and a plastic surgery resident performed 2 coaptations of each technique (10 coaptations total). PT and STS coaptations were performed with 3 cm of tendon overlap length and were secured with 3 horizontal mattress sutures using 3-0 Ethibond. The PT coaptations were performed with 3 orthogonal weaves. Repairs were timed by a nonparticipating study data recorder. All tendon coaptations were speckled with graphite for two-dimensional (2D) digital image correlation (DIC) and secured in a custom fabricated apparatus for uniaxial loading to failure. Vic2D was used for DIC analysis and linear correlations and two-sample Student's T-tests were used to compare the peak stresses and global strains.
ResultsGlobal strain, which was calculated as the total change in length over the total length between sutures, did not differ significantly between repairs. However, increased variability in the global strains from the PT technique was observed. High local shear strains appear around the sutures in both techniques, but not at the orthogonal cuts in the PT. Failure modes did not differ between repair techniques or experience level. Failure occurred around the sutures as the sutures sheared through the tendons. This was consistent with the strain analysis. Peak force correlated with the minimum tendon thickness (R
2 = 0.64). Normalizing the peak force by the minimum tendon thickness gives a proxy for shear stress, and there was no difference in the normalized force between techniques (p = 0.64) or experience level (p = 0.19). The PT required significantly more time to perform, regardless of experience (p < 0.001) and (p < 0.001).
ConclusionThe PT provides no advantage over the STS in terms of mechanical strength and requires significantly more time to perform. Shear strains concentrate around suture sites, implying that variations in repair strength are attributable to suture orientation and effectiveness.
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