Helical 6-Strand Cruciate Tenorrhaphy: Description of a New Technique and Biomechanical Comparative Analysis With 2 Standard Techniques

A 3-Dimensional Suture Technique for Flexor Tendon Repair: A Biomechanical Study

PURPOSE

Flexor tendon injury continues to pose a number of challenges for hand surgeons. Improving mechanical properties of repairs should allow for earlier and unprotected rehabilitation. A 3-dimensional (3D) 4-strand suture technique has been proposed to combine high tensile strength and low gliding resistance without causing suture pullout due to tendon delamination. Our hypothesis is that the 3D technique can result in better mechanical properties than the Adelaide technique.

METHODS

Four groups of 10 porcine flexor tendons were sutured using the 3D or Adelaide technique with a 3-0 polypropylene or ultrahigh molecular weight polyethylene (UHMWPE) suture. The axial traction test to failure was performed on each tendon to measure 2-mm gap force and ultimate tensile strength.

RESULTS

The mean 2-mm gap force was 49 N for group A (3D + polypropylene), 145 N for group B (3D + UHMWPE), 47 N for group C (Adelaide + polypropylene), and 80 N for group D (Adelaide + UHMWPE). Failure mode was caused by suture breakage for group A (10/10) and mainly by suture pullout for the other groups (8/10 up to 10/10). With the UHMWPE suture, the mean ultimate tensile strength was 145 N for the 3D technique and 80 N for the Adelaide technique.

CONCLUSIONS

Porcine flexor tendons repaired using the 3D technique and UHMWPE suture exceeded a 2-mm gap force and tensile strength of 140 N. The ultimate tensile strength was superior to that of the Adelaide technique, regardless of the suture material.

CLINICAL RELEVANCE

This in vitro study on porcine flexor tendon suture highlights that the mechanical properties of 3D repair are better than those of 3D repair using the Adelaide technique when a UHMWPE suture is used.

Comparison of Six-strand and Four-strand Techniques on the Repair of Injured Deep Flexor Tendons of Zone II of the Hand: A Randomized Controlled Clinical Trial

Background

Hand zone II flexor tendon repair had been associated with many complications thereby it was previously called no man's land. Although there is some agreement on the primary repair of flexor tendons in this area, it is challenging due to certain complications. We compared the six and four-strand techniques in the repair of flexor digitorum profundus (FDP) tendons of zone II.

Methods

This randomized controlled clinical trial was registered with the Iranian Registry of Clinical Trials (IRCT20130812014333N139). Fifty patients with damaged FDP in zone II of the hand who were referred to Taleghani Hospital, Kermanshah, Iran in 2020 were included and divided into two groups (n=25). In group 1, the damaged tendons were repaired using the four-strand technique and prolene suture while in group 2, the six-strand technique was used. Postoperatively, the patients were examined every week for the first three weeks. In the second and third weeks, sutures were removed. At the end of 3rd month, the outcomes of surgery were compared in the groups.

Results

Fifty patients (74% male) with 85 damaged fingers were investigated. Based on Buck-Gramcko criteria, the outcomes of surgery were excellent in 78%, good in 16%, fair in 4%, and bad in 2%. Complications after surgery were adhesion (8%) and 2 cases of rupture. There was no significant difference between 4 and 6-strand sutures regarding tendon adhesion and range of motion.

Conclusion

Both 4 and 6-strand sutures were associated with favorable outcomes in patients with damaged FDP in zone II of the hand.

Biomechanical analysis of a new 8-strand technique for flexor tendon repair

We sought to compare the strength and rupture sites of a new 8-strand suture technique with those of an established 6-strand flexor tendon repair through biomechanical analysis. This new 8-strand suture pattern places minimal suture material in the remodeling zone and focuses on protecting the knot, a well-known weak point of the suture construct. The knot was buried within the tendon so as to not interfere with tendon gliding. In a biomechanical simulation, strength and rupture sites were compared with those of the 6-strand repair. We repaired a total of 54 porcine flexor tendons using one of the two techniques (n=27 each). Tensile strength at 2-mm gap formation and ultimate failure load were determined. Afterwards, we dissected the tendons to identify the rupture site of the suture material. The new 8-strand suture had a significant higher ultimate load to failure (87.7N) and 2-mm gap load (71.6N) compared to the 6-strand technique (57.7N and 45.9N) (P<0.001). Whereas the rupture site of the core suture in the 6-strand technique was mainly located next to the knot (81.5%), the suture seemed to fail independently from this weak spot in the 8-strand technique (11.1%). This new 8-strand technique achieves a strong flexor tendon repair in a biomechanical model. Additional cross-locking on either side of the knot seems to contribute to the repair's strength. The resulting higher ultimate failure load and 2-mm gap load may allow more aggressive active motion-based postoperative rehabilitation.