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.

Introduction: Although a variety of fixation techniques have been reported for fixation of oblique or spiral metacarpal fractures, lag screw fixation has been reported to be the most biomechanically stable method. Lag screws are inserted following over-drilling of the proximal cortex, which provides compression at the fracture site. We believe the compression provided by the Leibinger Bow system makes over-drilling unnecessary.

Methods: Twenty fresh-frozen human cadaveric metacarpal bones (index, ring and middle) were utilised. Bones were cleared of soft tissue and the proximal ends were embedded in Wood’s metal using a Teflon mould. Long oblique osteotomies were performed with a fine oscillating saw. Bones were randomly allocated to lagged and non-lagged groups. All bones were held in the Leibinger Bow and fixed with two screws at right-angles across the fracture site. The proximal cortex of the lagged specimens was over-drilled and the non-lagged specimens were not. The bones were subjected to cantilevered bending to failure in a mechanical testing machine. The axial stress was calculated from results for load to failure and the moment of inertia for each specimen.

Results: All specimens failed through the proximal screw. Analysis of variance statistical analysis revealed no significant difference in axial stress between the two groups.

Conclusions: Minute errors during over-drilling of the proximal cortex can easily lead to inadequate fixation. These data suggest that the use of the Leibinger Bow System may eliminate the need for this over-drilling. This not only shortens the procedure, but also reduces the chance of errors leading to poor fixation.

Introduction: New flexor tendon repair techniques have been proposed to withstand the increased loads of active mobilisation. Most reports on the biomechanics of tendon repair are based on static testing. Cyclic testing more closely replicates the clinical situation and leads to gap formation at lower loads than in static testing.

Aim: To examine three types of tendon repair using a new cyclic testing protocol.

Methods: Thirty fresh-frozen cadaveric tendons were randomly assigned to three groups; Kessler repair with simple or cross-stitch epitendinous suture or Savage repair with simple epitendinous suture. All repairs were performed in situ in Verdan’s zone 2. Samples underwent tensile cyclic testing in a saline bath at a rate of 0.1Hz. Each specimen was subjected to two phases of testing replicating passive and active motion. Gap formation, stiffness and the mode of failure were recorded for each.

Results: The Savage repairs were stiffer and more resistant to gap formation than the Kessler repairs. The simple epitendinous suture seemed to be more resistant to gap formation than the cross-stitch suture although there was no significant difference in ultimate strength.

Conclusions: Cyclic testing is a more rigorous testing protocol that more closely replicates the clinical situation. This study showed that some repairs formed significant gaps at lower loads than the reported ultimate load-to-failure seen with static testing. Although cyclic testing has its limitations, we believe it is essential to assess fully tendon repair techniques, especially those considered for active mobilisation post-operatively. This study suggests the Savage repair may be a better option for active mobilisation protocols.