Introduction Zone 2 flexor tendon repairs can require ‘venting’ or partial resection of the A2 and/or A4 pulleys. We test a new technique where the pulley is divided and repaired with a V-Y plasty, increasing the pulley circumference. This allows access to perform the repair and/or permits free tendon gliding post-repair.

Methods Two groups of A2 and A4 pulleys from cadaveric fingers were divided and repaired in a V-Y fashion such that the circumference of the pulley tunnel was increased. The fingers were then mounted onto custom-made jigs and tested using a materials testing machine. One group had the A2 pulley assessed for changes in work of flexion by testing both before and after V-Y plasty. The second group had both the A2 and A4 pulleys tested for load to failure during functional loading. Biomechanical testing was performed.

Results There was a significant reduction in work of flexion after V-Y pulley expansion procedures were performed. Loads to failure for the A2 and A4 pulleys were in excess of 400% and 200% greater than one would expect in-vivo during a post-operative active mobilisation protocol. V-Y tendon pulley expansion increases the tunnel size while providing a mechanically sound pulley. It also maintains the pulley length and its coverage of the underlying tendon.

Conclusions This technique provides surgeons with an attractive alternative to simply ‘venting’ or resecting an otherwise troublesome pulley.

Introduction The four strand cruciate tendon repair has been described as the ideal technique, as it combines simplicity with the biomechanical advantages of four-strands. We wanted to determine if increasing the size of the locking loop increases the repair strength, and the gain in biomechanical integrity that various peripheral techniques provides.

Methods Forty-eight deep flexor tendons harvested from sheep hindlimbs were randomly divided into six groups of eight. All tendons were sharply transected. Initially, four groups were repaired using the cruciate core technique without a peripheral suture. The locking loops were set at 50%, 33%, 25%, or 10% of the volar CSA and then tested to failure. The final two groups of tendons were repaired using the established optimal locking loop size. These two groups were combined with either the simple running or the interlocking horizontal mattress (IHM) peripheral suture. These were then tested to failure and biomechanically assessed.

Results Repairs with locking loops of 25% had the greatest biomechanical properties; with load to two millimetre gap formation, load to failure and stiffness of 10N, 46.3 and 3.9N/mm respectively. Those with a 33%, 50% and 10% locking loops followed this. Those with 10% locking loops failed due to the suture material sliding out of the tendon. All other groups failed by suture breakage. Using the cruciate core technique with a 25% volar CSA locking loop, the load to two millimetre gap formation, load to failure and stiffness was 32.9N, 47.2N, and 7.6N/mm respectively when combined with the simple running peripheral suture and 46.4N, 79.4N and 9.9N/mm respectively when combined with the IHM repair. The IHM/cruciate combination was significantly better than the simple running/cruciate repair. Using the IHM technique in your tendon repair, this study demonstrates that the peripheral suture can provide approximately 75%, 40% and 60% of the total load to two millimetre gap formation, load to failure and stiffness respectively.

Conclusions Unlike the Kessler technique, increasing the size of the locking loop in the cruciate method decreases the repair strength. The ideal sized bite seems to be approximately 25% of the volar cross-sectional area. Additional, the peripheral suture is biomechanically vital to the integrity of the repair.

In relation to the conduct of this study, one or more of the authors is in receipt of a research grant from a non-commercial source.

Introduction Determining the extent of dynamic creep of a suture gives insight into the potential for formation of a flexor tendon repair site gap, with less creep having a positive benefit. We wanted to determine the dynamic creep of various suture materials using a cyclical testing protocol that simulates 30 days of active mobilisation.

Methods Four-strand loops, 20 mm in length, were created using Prolene, Ticron, Ethibond, and Mersilene (n=8 per group). Samples were loaded between 3.5N and 35N at 10 cycles per minute for 3000 cycles using a materials testing machine. All testing was conducted in phosphate buffered saline at 37° celsius. The dynamic creep was determined for each group. A separate group of suture loops were also created for load to failure testing. All data was analysed using ANOVA on SPSS software.

Results The loads to failure were 55.4, 65.5, 64.4 and 73.1N for Prolene, Ticron, Ethibond and Mersilene respectively. During cyclical testing, only one Prolene sample survived, with failure occurring after a mean of 1182 cycles (range 574 to 2660). Of those that failed, the mean creep was 3.80 mm (SD=0.51). In contrast, no specimens in the other groups failed, with a dynamic creep of 0.44 mm (SD=0.19), 0.32 mm (SD=0.17), and 0.28 mm (SD=0.07) for Ticron, Ethibond and Mersilene respectively.

Conclusions Regardless of your chosen suture technique for flexor tendon repairs, this study suggests that the suture material itself can play an important role in the eventual outcome. These results should be kept in mind when deciding on the suture material for your repairs.

Introduction The aim of this study was to determine the biomechanical properties of various combinations of four-strand core and peripheral suture techniques used in flexor tendon repairs.

Methods Seventy-two sheep flexor tendons were randomly divided into nine groups of eight. Tendons were sharply transected and repaired using three different four-strand core techniques: cruciate, modified-Kessler, and the modified Becker. These were combined with three different peripheral techniques: simple running, cross-stitch, and the recently described interlocking horizontal mattress (IHM). Tendons from these nine groups were loaded onto a materials testing machine and tested to failure using a crosshead speed of 20 mm/min. Load to two millimetre gap formation, load to failure, and stiffness was assessed. Data was analysed using ANOVA on SPSS for Windows.

Results For any given type of peripheral suture, no significant difference in biomechanical properties was found between the three core repair techniques. The only factor causing a significant difference in strength of the tendon repair was the type of peripheral suture technique used. Repairs with an IHM technique had significantly greater loads to 2 mm gap formation, load to failure, and stiffness, compared to the cross-stitch and simple running methods.

Conclusions This study demonstrates the superior biomechanical properties of the IHM technique. Increasing core suture complexity does not appear to have a significant impact on the overall mechanical integrity of the repair. These results should be considered when adopting a preferred repair technique.

The use of plates and screws for the treatment of certain metacarpal fractures is well established. Securing plates with bicortical screws has been considered an accepted practice. However, no study has questioned this.

This study biomechanically assessed the use of bicortical versus unicortical screws in metacarpal plating. Eighteen fresh frozen cadaveric metacarpals were subject to midshaft transverse osteotomies and randomly divided into two groups. Using dorsally applied Leibinger 2.3mm 4 hole plates, one group was secured using 6mm unicortical screws, while the second group had bicortical screws. Metacarpals were tested to failure using a four point bending protocol in an apex dorsal direction on a servo-hydraulic testing machine with a 1kN load cell. Load to failure, rigidity, and mechanism of failure were all assessed.

Each group had three samples that did not fail after a 900 N load was applied. Of those that failed, the mean load to failure was 596N and 541 N for the unicortical and bicortical groups respectively. These loads are well in excess of those experienced by the in-vivo metacarpal. The rigidity was 446N/mm and 458N/mm of the uni-cortical and bicortical groups respectively. Fracture at the screw/bone interface was the cause of failure in all that failed, with screw pullout not occurring in any.

This study suggests that there may be no biomechanical advantage in using bicortical screws when plating metacarpal fractures. Adopting a unicortical plating method simplifies the operation, and avoids potential complications associated with overdrilling and oversized screws.

Introduction: The classic teaching in flexor tendon repair suggests that a 10mm bite is important for the integrity of the repair regardless of the other features of the technique. Although this has been widely accepted since Bunnell’s first descriptions of accurate flexor tendon repair there appear to be little data to support it. An extensive review of the literature showed no biomechanical data relating specifically to size of bite in flexor tendon repair. We hypothesised that decreased bite may cause less damage to the tendon during repair while still offering adequate mechanical strength.

Aim: To investigate the effect of different bite sizes on the mechanical properties of flexor tendon repairs.

Methods: Twenty fresh-frozen cadaveric flexor tendons were divided at their centres. One side of a modified Kessler repair was used on each side taking a 6mm bite on one side and a 10mm bite on the other. The tendons underwent tensile testing on a mechanical testing frame by pulling on the ends of the suture with the tendon secured in pneumatic grips. Data for stiffness and ultimate load to failure were recorded.

Results: An increased bite size made no significant difference to stiffness of the repairs. There was a difference in load to failure noted but this was not significant. The ultimate load to failure was noted after the specimens had been distracted over 2mm, which would result in clinical failure.

Conclusions: These results suggested that a 10mm bite may be excessive in flexor tendon repair and could cause more tissue damage than lesser bites. Further study of in vivo effects of decreased bite size is required.