A Biomechanical Study of a Novel Asymmetric 6-Strand Flexor Tendon Repair Using Porcine Tendons

Strength, bulk and surgery time of ex situ versus in situ flexor tendon repair in a cadaveric model

The purpose of this study was to compare strength, bulk and time of repair of human cadaveric flexor digitorum profundus tendons repaired in situ versus ex situ. Ninety-six human cadaveric flexor digitorum profundus tendons were transected 5 mm distal to the A2-pulley and randomized to 2-strand, 4-strand or 6-strand repairs. We found no significant differences in repair strength between in situ and ex situ repairs, but repair strength increased with increasing number of strands. The cross-sectional area of the repair was not significantly related to the number of strands, but 4- and 6-strand in situ repairs were bulkier than ex situ repairs. In situ repair took longer, and repair time increased with increasing number of strands. We suggest that cadaveric studies of flexor tendon repair should be performed in situ in order to better mimic the clinical reality of tissue handling and repair bulkiness.

A Biomechanical Comparison of Gliding Resistance between Modified Lim Tsai and Asymmetric Tendon Repair Techniques in Zone II Flexor Tendon Repairs

Background: Early active motion protocols have shown better functional outcomes in zone II flexor tendon lacerations. Different techniques of tendon repair have different effects on gliding resistance, which can impact tendon excursion and adhesion formation. For successful initiation of early active mobilisation, the repair technique should have high breaking strength and low gliding resistance. Previous studies have shown the Modified Lim-Tsai technique demonstrates these characteristics. The Asymmetric repair has also shown superior ultimate tensile strength. This study aims to compare the gliding resistance between the two techniques. Methods: FDP tendons from ten fresh frozen cadaveric fingers were randomly divided into two groups, transected completely distal to the sheath of the A2 pulley and repaired using either the Modified Lim-Tsai or Asymmetric technique. The core repair was performed with Supramid 4-0 looped sutures and circumferential epitendinous sutures were done with nylon monofilament Prolene 6-0 sutures. The gliding resistance and ultimate tensile strength were then tested. Results: The gliding resistance of the Asymmetric and Modified Lim-Tsai repair techniques were 0.2 and 0.95 N respectively. This difference was significant (p = 0.008). The Modified Lim-Tsai technique had a higher ultimate tensile strength and load to 2 mm gap formation, though this was not significant. Conclusions: Gliding resistance of the Asymmetric repair is significantly less than that of Modified Lim-Tsai. Ultimate tensile strength and load to 2 mm gap formation are comparable.

Ex Vivo Biomechanical Assessment of a Novel Multi-Strand Repair of Canine Tendon Lacerations

OBJECTIVE

 This study aimed to evaluate the effect of increasing the number of suture strands traversing the transection site, level of suture purchase and depth of suture penetrance on the biomechanical properties of repaired gastrocnemius tendons.

STUDY DESIGN

 Thirty-eight adult cadaveric gastrocnemius tendons were randomized, transected and repaired with either two-, four- or six-strand locking multi-level repair. Tensile loads required to create a 1 and 3 mm gap, yield, peak and failure loads and failure mode were analysed. Significance was set at p < 0.05.

RESULTS

 Mean ± standard deviation yield, peak and failure force for six-strand repairs was 90.6 ± 22.1 N, 111.4 ± 15.2 N and 110.3 ± 15.1 N respectively. This was significantly greater compared with both four-strand (55.0 ± 8.9 N, 72.9 ± 7.8 N and 72.1 ± 8.2 N) and two-strand repairs (24.7 ± 8.3 N, 36.5 ± 6.0 N and 36.1 ± 6.3 N) respectively (p < 0.001). Occurrence of 3 mm gap formation was significantly less using six-strand repairs (p < 0.001). Mode of failure did not differ between groups with all repairs (36/36; 100%) failing by suture pull-through.

CONCLUSION

 Pattern modification by increasing the number of suture strands crossing the repair site, increasing points of suture purchase from the transection site and depth of suture penetrance is positively correlated with repair site strength while significantly reducing the occurrence of gap formation in a canine cadaveric model. Additional studies in vivo are recommended to evaluate their effect on tendinous healing, blood supply and glide resistance prior to clinical implementation.