Repairs of Partial Oblique Tendon Injuries: A Biomechanical Evaluation

Effect of Oblique Tendon Laceration on Core Suture Strength: A Biomechanical Evaluation

BACKGROUND

The effect of obliquity of tendon laceration on repair strength is not well studied. The overwhelming majority of biomechanical studies assess repair strength following a laceration that is perpendicular to the long axis of the tendon. The aim of this study was to investigate whether the angle of tendon laceration affects the core suture strength.

METHODS

In all, 110 fresh human cadaveric flexor tendons were cut at varying angles of 15°, 30°, 45°, and 60° and the control group at 90°. All tendons were repaired with 6-strand modified Tang technique. The repair strength was tested using a custom-made tensioning machine, and the initial static gap force and the ultimate breaking force were measured.

RESULTS

The mean gap force and 95% confidence interval (CI) for the 15°, 30°, 45°, 60°, and 90° groups were 15.2 N (11.4-19.0 N), 15.8 N (13.6-18.1 N), 15.6 N (13.1-18.4 N), 16.6 N (13.7-19.5 N), and 22.3 N (16.6-27.9 N), respectively. In the same respective order, the break force and 95% CI were 25.9 N (21.9-29.8 N), 26.5 N (23.2-29.7 N), 31.1 N (26.1-36.1 N), 35.6 N (28.2-43.1 N), and 51.8 N (62.5-41.0), respectively. The Fisher least significant difference demonstrated significant differences between the control group and all experimental groups for both gap force and break force.

CONCLUSIONS

Obliquity of tendon laceration affects the core suture strength when compared with a transverse cut. Flexor tendons cut at 90° demonstrated a higher overall gap force and breaking strength that were statistically significant when compared with all obliquely cut groups. These findings should be considered when repairing and starting postoperative therapy for obliquely cut tendons.

Biomechanics Study of the Holding Power between Tendon and Suture Using Different Techniques

Background: The holding power of a repaired flexor tendon injury is related to surface sutures, suture material and different techniques. Nowadays, a barbed suture material offers the possibility of knotless flexor tendon repair but many hospitals use non-barbed suture materials. The purpose of this study was to compare a barbed suture material and a non-barbed suture material for primary stability under static loading and increased knots in the non-barbed suture material (knot technique) for increased holding power of tendons in animal testing. Methods: Forty-five fresh porcine tendons were randomized into three groups: Group 1 (grasping technique group) used a four-strand core suture grasping a four-strand modified Kessler suture by non-barbed suture material [Non-absorbable monofilament polybutester 3-0] was used to repair the tendon with a surgical knot; in Group 2 (knot technique group) a four-strand core suture used the knot technique by non-barbed suture material [Non-absorbable monofilament polybutester 3-0] to repair the tendon with a continuous suture adding surgical knots in the same place as the surgical knot at the repair sites; and Group 3 (knotless technique group) used a four-strand core suture with the knotless technique in modified Kessler suture with barbed suture material [Non-absorbable monofilament polybutester 3-0] to repair the tendon without a knot. Our objective was to compare the ultimate tensile strength between the groups. Results: The mean tensile strength was 30.38 ± 5.04 N for group 1, 41.71 ± 2.62 for group 2 and 47.53 ± 4.89 for the group 3. The ANOVA test revealed a significant difference among the various techniques (p < 0.05). The highest tensile strength was found in the knotless technique using barbed suture material group. Conclusions: The knotless technique using barbed suture material demonstrated the highest tensile strength in suture repairs. The maximum tensile strength was significantly higher in this group.

[Primary flexor tendons repair in zone 2]

Primary flexor tendon repair is still challenging even in the most experienced hands. With atraumatic surgery, the goal is to suture the tendon in a way that it will be strong enough to allow for tendon gliding without the risk of rupture or adhesions during the 12 weeks needed for the tendon to heal. After reviewing the zone 2 anatomy, the authors describe the state of art for flexor tendon repair along with their personal preferences. Although suture methods and postoperative rehabilitation programs are not universal, most specialized teams now use multistrand suturing techniques with at least 4 stands along with protected and controlled early active mobilization. Although the published rates of failure of the repair or postoperative adhesions with stiffness have decreased, these complications are still a concern. They will continue to pose a challenge for scientists performing research into the mechanics and biology of flexor tendon repairs, especially in zone 2.

Support for partial lesions of the flexor tendons of the fingers: a retrospective study of 36 cases

The treatment of traumatic partial injuries of the flexor tendons of the fingers is seldom published. The only published clinical series states that the therapeutic approach depends on the existence or absence of a preoperative trigger. We hypothesized that the therapeutic attitude mainly depends on the percentage of the injured cross-section. Our retrospective series included 36 partial lesions of 31 fingers in 29 patients. The average age was 42 years, there were 19 men. We noted 8 lesions in zones I, 21 in zone II and 2 in zone III. The average percentage of the injured cross-section was 35% and ranged from 10% to 90%. If the lesion was less than 50% (29 tendons), a tangential resection was performed. If the lesion exceeded 50% (seven tendons), a direct suture was performed, supplemented by a running suture. At a follow-up of 34 months, the average pain on a visual analogue scale was 0.7. The average percentage of strength compared to the contralateral side was 93%. The Quick DASH score was 6.2. The range of motion averaged 214° with extremes ranging from 90° to 260°. We observed no cases of hypertrophic callus, neither through the MRI nor through the ultrasonography. Complications such as trigger finger, pseudoblocage or rupture were not observed. Based on our results, in case of partial injury of a flexor tendon, we propose to perform a tangential resection in cross-section lesions up to 50%, and a suture for those which exceeded 50%.

How much does a Pennington lock add to strength of a tendon repair?

Pennington advocated adding locking components to the Kessler-type repair to increase the repair strength, but did not actually test the repairs with this lock. Subsequent investigators have extensively cited that a Pennington lock is beneficial to the gain of repair strength. Thirty-three tendons were used to determine the exact strength differences between two grasping Kessler repairs and a Kessler repair with Pennington locks complemented with running peripheral suture. Two types of grasping repairs only had slightly lower resistance to gap formation compared with the repair with Pennington locks, and their ultimate strengths were not significantly different. We also compared the strength of four-strand Kessler repair with and without Pennington locks using 20 tendons, and found no difference in either gapping or ultimate strength. We conclude that a Pennington lock adds only a little to the capacity to gap resistance of a repair, but does not increase the ultimate strength.

Comparison of 1- and 2-knot, 4-strand, double-modified kessler tendon repairs in a porcine model

PURPOSE

To compare 1- and 2-knot, 4-strand, double-modified Kessler tendon repairs. It was our hypothesis that a 1-knot technique using an unbraided suture material would be stronger if it is possible for some movement to occur between strands on loading, redistributing forces such that the load is equally shared.

METHODS

Fifty-six porcine flexor tendons were allocated to either a 1- or 2-knot, 4-strand, double-modified Kessler repair, and tested by incremental cyclical loading in vitro.

RESULTS

The 1-knot technique was significantly stronger. Gap formation was initially greater in the 1-knot group, consistent with movement of strands, but with increasing physiological levels of applied force, there was no significant difference between the groups.

CONCLUSIONS

The 1-knot technique was significantly stronger than the 2-knot technique.

Tensile strength of modified 4-strand cruciate technique for transversely or obliquely lacerated tendons

PURPOSES

To assess the tensile strength of the modified 4-strand cruciate technique for obliquely lacerated tendons, and to compare the findings with the strength of transversely lacerated tendons repaired at various grasping depths.

METHODS

60 porcine front foot tendons were evenly divided into 4 groups. In groups 1 to 3, tendons were transversely lacerated and repaired with grasping points at both ends away from the laceration by 5 mm, 10 mm, and 15 mm respectively. In group 4, tendons were obliquely lacerated and repaired with a grasping point 5 mm away from the laceration on one end and 15 mm on the other. All tendons were repaired with a modified 4-strand core suture and continuous epitendinous suture, and then tested to failure in a tensile machine.

RESULTS

The tensile strength in group 1 was significantly lower than that in the other 3 groups (p<0.005). The tensile strength in group 4 was not significantly different from groups 2 and 3.

CONCLUSION

The tensile strength of modified 4-strand cruciate repair configuration is not weakened in obliquely lacerated tendons; the grasping point at one end of the tendon being 15 mm away from laceration provides sufficient strength to compensate for the relatively weak 5-mm end. So long as one grasping point is away from the laceration site by 10 mm, the ultimate tensile strength of the transversely lacerated tendons appears acceptable. The modified 4-strand cruciate repair is safe to use for repairing obliquely lacerated tendons.

An assessment of the tensile properties and technical difficulties of two- and four-strand flexor tendon repairs

This study compares the mechanical properties of locking Kessler and four-strand flexor tendon repairs and examines for difficulties related to technical ability. Two trainee surgeons each carried out 10 locking Kessler and 10 four-strand single-cross flexor tendon repairs on an in vitro porcine model. Outcome measures included gap formation and ultimate forces, operative time and repair bulk. Ultimate force was 81% greater for the four-strand repair compared to the Kessler (52 N, SD 5, versus 29 N, SD 6). Operating times were similar between the two techniques (Kessler 10.0 minutes, four strand 10.1 minutes). Rupture force and operating times improved slightly during the study for the Kessler repairs, but in the four strand repairs results remained stable throughout the study. We conclude that the single-cross four-strand repair tolerates superior loads yet is no more technically demanding than the modified Kessler, and can be reliably performed without additional operating time.