Biomechanical analysis of intrinsic tendon healing in vitro and the effects of vitamins A and E

Optimizing the Pulvertaft Weave Technique: A Comprehensive Systematic Review of Comparative Biomechanical Studies

PURPOSE

The Pulvertaft weave continues as a staple technique for tendon coaptations. Many have proposed minor alterations to the original technique to improve its strength, though a lack of consensus exists. Our aim was to explore how the number of weaves and suture characteristics contribute to the overall strength of the coaptation.

METHODS

A comprehensive electronic search was conducted using PubMed, Cochrane Library, and Scopus. Criteria for inclusion consisted of cadaveric human or animal biomechanical studies evaluating ultimate failure load (Newtons, N) as well as number of weaves, suture characteristics, tendon source, and number of coaptations. Weaves with minimum averages of 75 N were deemed successful, and those with >120 N were considered high performing.

RESULTS

A total of 347 tendon transfers from 15 studies met inclusion criteria. Average strength by number of weaves was 36.4 N (n=52) for 1 weave; 54.2 N (n=58) for 2 weaves; 115.9 N (n=174) for 3 weaves; and 81.7 N (n=63) for 4 weaves. Statistical differences were observed between 1 and 2 weaves (p<0.0001); 2 and 3 weaves (p<0.0001); 3 and 4 weaves (p<0.003); and 2 and 4 weaves (p<0.0001). High performing tendon transfers utilized 3 weaves, 3-0 or 4-0 braided sutures, and figure-of-eight or mattress core sutures.

CONCLUSIONS

Contrary to the current dogma of 'the more the better', our findings show that Pulvertaft weave strength is optimized when 3 weaves are used to combine donor and recipient tendons. Braided sutures with either figure-of-eight or mattress sutures were associated with highest strength of repair.

Single-stage reconstruction of flexor tendons with vascularized tendon transfers

The reconstruction of finger flexor tendons with vascularized flexor digitorum superficialis (FDS) tendon grafts (flaps) based on the ulnar vessels as a single stage is not a popular technique. We reviewed 40 flexor tendon reconstructions (four flexor pollicis longus and 36 finger flexors) with vascularized FDS tendon grafts in 38 consecutive patients. The donor tendons were transferred based on the ulnar vessels as a single-stage procedure (37 pedicled flaps, three free flaps). Four patients required composite tendon and skin island transfer. Minimum follow-up was 12 months, and functional results were evaluated using a total active range of motion score. Multiple linear regression analysis was performed to evaluate the factors that could be associated with the postoperative total active range of motion. The average postoperative total active range of motion (excluding the thumbs) was 178.05° (SD 50°). The total active range of motion was significantly lower for patients who were reconstructed with free flaps and for those who required composite tendon and skin island flap. Age, right or left hand, donor/motor tendon and pulley reconstruction had no linear effect on total active range of motion. Overall results were comparable with a published series on staged tendon grafting but with a lower complication rate. Vascularized pedicled tendon grafts/flaps are useful in the reconstruction of defects of finger flexor tendons in a single stage, although its role in the reconstructive armamentarium remains to be clearly established.

History and performance of implant materials applied as peritendinous antiadhesives

Peritendinous fibrotic adhesions after tendon surgery are still a problem up-to-date. Approaches to overcome or at least minimize adhesion formation include implantation of barrier materials, application of lubricants or combinations of materials and functionalized drugs that are controllably released and support the healing tendon to glide and achieve the full range of motion after regeneration. Although a huge amount of different materials have been experimentally tested, the optimal strategy with respect to material and method has not yet been determined. In this review, we present a historical overview of physical barriers as well as liquid agents that have been used in order to prevent peritendinous adhesion formation. The materials are divided according to their first publication into two time frames; before and after 1980. There is no claim to include all materials tested neither will the "best" material be chosen; however, we present several materials that were experimentally tested in different animal trials as well as in clinical trials in contrast to other materials that were only tested once and disappeared from the assortment of anti-adhesives; which as such is a valuable information about its applicability for this purpose.

Extensor hallucis longus tenorrhaphy by using the Massachusetts General Hospital repair

Extensor hallucis longus tendon injury and surgical treatment recommendations are infrequently reported. In contrast to long extensor tendon injuries to the foot, flexor and extensor tendon injuries of the hand have been extensively studied and surgical treatment protocols have been delineated. In biomechanical studies, the Massachusetts General Hospital technique has been shown to have superior strength to other tenorrhaphies and to allow for early active mobilization. The purpose of this study was to examine the use of this technique for repair of extensor hallucis longus tendon injuries to allow for early active motion with minimal risk of rupture. We performed a retrospective review of 6 extensor hallucis longus tendon repairs at the toe level. These patients all regained active motion of the great toe. None had loss of extension. There were no tendon ruptures with this technique of tendon repair. The Massachusetts General Hospital technique can be used to repair the extensor hallucis longus tendon with good functional outcome and minimal risk of tendon rupture.

Mechanical analysis of explanted silicone breast implants

Smooth-walled silicone gel breast implants (n = 25) were removed from 15 women after implantation times that varied from 23 to 216 months (mean = 117 months; SEM = 12.9). Strips of implant shells were tested to failure by computer-controlled tensiometer. Regression analysis revealed significant negative correlation between age of implantation and shell strength (p < 0.05), shell toughness (p < 0.05), and shell elasticity (p < 0.05). These data suggest that exposure to the in vivo environment weakens silicone gel breast implant shells over time.

Effects of laser versus scalpel tenolysis in the rabbit flexor tendon

The use of surgical lasers has been shown to decrease adhesion formation as compared with scalpel control groups in various surgical procedures. The potential benefits of laser technology have not been assessed in the treatment of adherent tendons. The current study was designed to first develop a reliable and reproducible model for consistent adhesion formation following flexor tendon trauma. The second goal was to compare the effects of laser tenolysis procedures on tendon gliding with those of traditional scalpel tenolysis. In phase I, the adhesion-induction model utilized bilateral standardized crush- abrasion injuries to the hind limb digital flexor tendons of New Zealand White rabbits. Following 4 weeks of immobilization, the animals were sacrificed, and peritendoneal adhesions were assessed biomechanically. A significantly higher maximal force was required to extract the adherent tendons from the foot as compared with nontraumatized control tendons. In phase II, six groups of animals underwent the same standardized tendon trauma. Four weeks later the rabbits were randomly assigned to undergo either CO2 laser or holmium:YAG laser tenolysis on one foot. Scalpel lysis was used on the contralateral foot and served as an intraindividual control. Biomechanical assessment was performed at 1, 2, and 4 weeks following tenolysis. Significantly less force was required to extract the treated tendons at 1 and 2 weeks following holmium:YAG laser tenolysis when compared with scalpel or CO2 laser tenolysis. After 4 weeks, differences between holmium:YAG and CO2 laser and scalpel treatment were no longer significant. Extracted tendons were pulled apart to failure, and no difference in breaking strength was noted between groups. We conclude that holmium:YAG laser tenolysis results in easier tendon gliding as compared with scalpel or CO2 laser tenolysis at early time points. Laser tenolysis does not affect intrinsic tendon strength.

Mechanical analysis of tendon suture techniques

The relative strengths of seven methods of tendon repair were measured by mechanical disruption in an effort to determine the quality of a technique using loaded criss-crossing sutures and a running epitenon stitch. Fifty-seven calcaneus tendons were harvested from adult New Zealand white rabbits and randomized for transection. Standardized oblique transections were repaired with nylon using modified Halsted peripheral suture; modified Kessler technique; Kessler core stitch alone; running peripheral epitenon stitch; modified Becker technique #1; modified Becker technique #2; and a new augmented Becker repair. Sixteen additional rabbits each had bilateral tendon repairs in situ, one leg by Kessler and the other by the new augmented Becker repair technique. Half were lethally injected after 2 weeks and half after 4 weeks. Tenorrhaphies were pulled apart at constant speed until a gap of 1 mm was observed. Strength (maximum stress) and toughness (energy absorption to gap formation) were calculated. At time 0 the new augmented Becker repairs were the strongest, followed by the Kessler and Becker #2 tenorrhaphies. Kessler repairs were weaker at 2 weeks and then gained in strength; new augmented Becker repairs did not weaken at the 2-week point and demonstrated significant gains in strength after 4 weeks in vivo. The new augmented Becker repair was the strongest by a significant margin at all time points.