Considerations in the surgical use of the flexor sheath and pulley system

The incidence and shape of the digital pulleys: a study of 192 fingers in 48 cadaveric hands

We dissected 192 fingers in 48 fresh cadaveric hands (23 right and 25 left hands from 26 female and 22 male donors) and analysed the incidence, location, length and structure of the five annular and three cruciform pulleys. No statistically significant differences were found between left and right or between male and female hands. The A1, A2 and A4 pulleys were present in all fingers, while the incidence of other pulleys varied. We found 32 different patterns of pulley combinations. The structure of the pulleys also varied. Most important was the variation of A1, which consisted of one to four separate rings. In 18% there was no gap between the A1 and A2 pulleys. A greater understanding of the anatomical variation of the pulley system is beneficial for hand surgeons performing open or percutaneous trigger finger releases and for radiologists examining the area sonographically.

Clinical results of releasing the entire A2 pulley after flexor tendon repair in zone 2C

We report the results of complete release of the entire A2 pulley after zone 2C flexor tendon repair followed by early postoperative active mobilization in seven fingers and their comparisons with 33 fingers with partial A2 pulley release. In seven fingers, release of the entire A2 pulley was necessary to allow free gliding of the repairs in five fingers and complete release of both the A2 and C1 pulleys was necessary in two. No bowstringing was clinically evident in any finger. Two fingers required tenolysis. Using Tang's criteria, the function of two digits was ranked as excellent, four good and one fair; there was no failure. The functional return in these seven fingers was similar with that in 33 fingers with partial A2 pulley release; in these patients only one finger required tenolysis. Our results support the suggestion that release of the entire A2 pulley together with the adjacent C1 pulley does not clinically affect finger motion or cause tendon bowstringing, provided that the other pulleys are left intact.

LEVEL OF EVIDENCE

IV.

Outcomes of release of the entire A4 pulley after flexor tendon repairs in zone 2A followed by early active mobilization

We report the outcomes of repair of the flexor digitorum profundus tendon in zone 2a in 22 fingers. The tendon was repaired with a six-strand repair method and the A4 pulley was completely released. Release of the C2 pulley combined with the A4 pulley was necessary in 12 fingers, nine fingers underwent a complete release of the A3, C2, and A4 pulleys, and one finger underwent a release of the C1, A3, C2, and A4 pulleys. The mean total active motion of the three finger joints was 234° at 5 to 12 months of follow-up. No bowstringing was noted in these fingers. The good and excellent recovery of active digital motion was in 20 (91%) out of 22 fingers according to Strickland's criteria or Tang's criteria. Our results suggest that release of the A3, C2, and A4 pulleys makes the repair surgery easier and does not cause tendon bowstringing.

Vein grafts to augment flexor tendon repairs: a biomechanical study on strength and gap resistance

The ultimate tensile repair strength and gap formation of the pig extensor tendons repaired with a standard 4-strand Savage with epitendinous suture repair, was compared with a new technique of adding a vein sleeve. Force and displacement data were recorded, and video images during linear cyclic loading up to failure. At 35 N, video-graphic observation detected significantly smaller gap lengths in the standard and vein repair specimens compared with standard repair specimens (p = 0.047). The incidence of 3 mm gaps between the repaired tendon ends in the standard repair group was 20 %, but no 3 mm gaps were seen in the standard and vein specimens. The addition of a vein sleeve increased the ultimate tensile strength of the standard repair from 50.4 N (4.5) to 55.4 N (4.5); this was statistically significant (p = 0.03). This study demonstrated that the addition of a vein graft prevented gap formation and increased ultimate tensile strength of tendon repair.

Surgical adhesive BioGlue™ does not benefit tendon repair strength: an ex vivo study

Surgical adhesives are useful supplements in surgery, but their benefit in tendon repair is uncertain. The purpose of this study was to evaluate the effect of BioGlue™ on strength of flexor tendon repair. A total of 60 porcine flexor tendons were divided into three groups. In group one, a conventional core and peripheral suture repair was used. In group two, a core suture and BioGlue™ were used. In group three, a conventional core and peripheral suture repair and BioGlue™ were used. We performed static and cyclic axial load testing and measured diameter of the repair site. We found that BioGlue™ did not improve the tensile strength when added to a core and peripheral suture and that there was an increase in bulk at the repair site. We conclude that BioGlue™ application cannot replace a peripheral suture as tensile strength significantly decreases without a peripheral suture, and it does not benefit a tendon already repaired with a core and peripheral suture.

LEVEL OF EVIDENCE

n/a.

Flexor digitorum superficialis repair outside the A2 pulley after zone II laceration: gliding and bowstringing

PURPOSE

To evaluate the changes in maximum flexion angle, gliding coefficient, and bowstringing after a combined repair of both flexor tendons with the flexor digitorum superficialis (FDS) rerouted outside the A2 pulley in cadaveric hands.

METHODS

We performed 4 different repairs on cadaveric hands, with each repair tested on 9 unique digits. In total, 12 cadaveric hands and 36 digits were used. The thumb and little finger were removed from each hand and excluded from testing. Group 1 was sham surgery. Group 2 combined flexor digitorum profundus (FDP) and FDS laceration and repair with both slips of the FDS repaired inside the A2 pulley. Group 3 was FDP repair with one slip of the FDS repaired inside A2 and the other slip left unrepaired. Group 4 was FDP repair with both slips of the FDS rerouted and repaired outside the A2 pulley. Maximum flexion angle, gliding coefficient, and bowstringing were measured in simulated active digital motion for each group.

RESULTS

Rerouting and repairing the FDS outside the A2 pulley (group 4) significantly lowered gliding coefficient compared with repairs with both slips inside A2, with values similar to sham surgery. We observed no significant differences in maximum flexion angle among the 4 groups. Increased bowstringing was observed with both slips of the FDS repaired and rerouted outside the A2 pulley.

CONCLUSIONS

In this cadaveric model, repair of both slips of the FDS outside the A2 pulley improved the gliding coefficient relative to repair within the A2 pulley, which suggests decreased resistance to finger flexion. Repair of the FDS outside the A2 pulley led to a slight increase in bowstringing of the FDS tendon.

CLINICAL RELEVANCE

We describe a technique for managing combined laceration of the FDP and FDS tendons that improves gliding function and merits consideration.