Lacerations of the FDP tendon in zone one may be reattached to bone with a modified Bunnell pullout suture or with suture anchors. Eleven cadaveric fingers were submitted to cyclical testing of five hundred cycles with either a modified Bunnell pullout suture of 3-0 polypropylene or a micro-Mitek suture anchor with 3-0 Ethibond. Gap formation was 6.6mm in the modified Bunnell group and 2.0mm in the micro-Mitek group (p< 0.001). Load to failure was 37.6N in the pullout group and 28.5N in the anchor group (p< 0.005). Gap in the pullout group and low failure load in the anchor group are of concern.

Distal zone one FDP tendon lacerations are usually re-attached to bone by a modified Bunnell pullout suture of 3-0 polypropylene. This treatment may lead to moderate to severe losses of DIP joint motion in up to 50% of patients. Suture anchors have recently been introduced as a fixation alternative. Cyclical testing simulating five days of a passive mobilisation protocol was used to compare the Micro-Mitek anchor to the modified-Bunnell pullout suture in FDP tendon fixation.

Eleven cadaveric fingers FDP tendons were repaired to bone using a modified Bunnell pullout suture of 3-0 polypropylene or a micro-Mitek anchor with 3-0 Ethibond. Testing was done from 2N to 15N at 5N/sec, for a total of five hundred cycles. Gap formation at the tendon bone interface was measured. Load-to-failure was performed on all specimens.

No specimens failed during cyclic testing. Gap formation was 6.6mm (SD 1.2, range 4.9–8.2mm) and 2.0mm (SD = 0.4, range 1.7–2.7mm) for the pullout technique and the micro-Mitek anchor repair respectively (p< 0.001). Load to failure data was 37.6N (SD 4.7, range 31.8–45.1N) for the pullout group and 28.5N (SD 4.0, range 21.8–33.4N) for the micro-Mitek group (p< 0.005).

This data suggests that both fixation techniques may be adequate to sustain five days of simulated passive rehabilitation therapy. Significant gap formation in the modified Bunnell pullout group is of concern although this needs to be correlated in the clinical setting. The lower failure rate of the micro-Mitek group may leave a narrow margin of safety for passive rehabilitation.

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.

The behaviour of two different methods of reattachment of the flexor digitorum profundus tendon insertion was assessed. Cyclical testing simulating the first 5 days of a passive mobilisation protocol was used to compare the micro Mitek anchor to the modified-Bunnell pull-out suture. Twelve fresh-frozen cadaveric fingers were dissected to the insertion of the FDP tendon. The FDP insertion was then sharply dissected from the distal phalanx and repaired using one of two methods: group 1 -modified Bunnell pullout suture using 3/0 Prolene; group 2 micro Mitek anchor loaded with 3/0 Ethibond inserted into the distal phalanx. Each repaired finger was mounted on to a material testing machine using pneumatic clamps. We cyclically tested the repair between 2N and 15N using a load control of 5N/s for a total of 500 cycles. Gap formation at the tendon bone interface was measured every 100 cycles.

No specimens failed during cyclical testing. After 500 cycles, gap formation of the tendon-bone interface was 6.6mm (SD = 1.2mm), and 2.1 mm (SD = 0.3mm) for the pullout technique and the micro Mitek anchor repair respectively. Concerns related to suture anchors, such as anchor failure or protrusion, joint penetration, and anchor-suture junction failure, were not encountered in this study.

Cyclical loading results suggest that the repair achieved with both methods of fixation is sufficient to avoid failure. However, significant gap formation at the tendon-bone interface in the modified Bunnell group is of concern, suggesting it may not be the ideal fixation method.