Small hook thread (Quill) and soft felt internal splint to increase the primary repair strength of lacerated rabbit Achilles tendons: biomechanical analysis and considerations for hand surgery.

BACKGROUND: For the prevention of re-rupture during early healing phase, the primary repair strength of repaired lacerated tendons in hand surgery should be maximal and the reconstructed diameter minimal. Two new repair methods (small hook thread and internal splint) were assessed for strength and reconstructed diameter characteristics.
METHODS: Achilles tendons of 43 female New Zealand White rabbits were sectioned 2 cm above the calcaneus. Specimens were divided into 7 groups and repaired as follows: Kirchmayr method 2-strand with 4.0 polypropylene thread; Becker method 4-strand; 6-strand; internal splint; Kirchmayr method small hook 2-strand; Becker method small hook 4-strand, non-modified tendon. Load until failure, load until gap formation, gap length, cross-sectional area and failure stress were determined.
FINDINGS: The small hook 2-strand suture had 1.3 fold higher loads until failure compared to a conventional 2-strand suture, P<0.05. The internal splint had a similar load until failure (22 N (SD 6)) as the conventional 2-strand suture (23 N (SD 4)); around half the load until failure of the conventional 4-strand suture (38 N (SD 9)). Load until gap formation correlated positively with load until failure (y=0.65+3.6; r(2)=0.72). The running suture increased the cross-sectional area at the repair site by a factor of 1.3.
INTERPRETATION: Using a small hook thread instead of a 4.0 polypropylene thread significantly increases the primary repair strength with the same number of strands. Internal splints may be an alternative to conventional 2-strand sutures for bridging large gaps.