A biomechanical comparison of shape memory compression staples and mechanical compression staples: compression or distraction?

Compression staples are a popular form of fixation for osteotomy and arthrodesis. "Mechanical compression" or "shape memory" designs are commercially available. We performed a biomechanical study comparing these designs. A load cell measured compression across a simulated fusion site. The two designs available were tested and compared. The effect of altering staple limb length was also assessed. The limbs of all mechanical compression staples diverged causing inconsistent compression and distraction. Shape memory staples all achieved consistent compression across the fusion site with significantly greater maximum force when compared to mechanical compression staples (P < 0.001). Staple limb length did not appear to alter compression force generated. Mechanical compression staples cause a distractive force, and we therefore suggest alternate forms of fixation for arthrodesis. Shape memory staples do provide compression and may be suitable for arthrodesis and osteotomy.

The Achillon achilles tendon repair: is it strong enough?

BACKGROUND: Open repair of the Achilles tendon is associated with wound breakdown, infection and percutaneous methods risk sural nerve injury. The Achillon mini-incision technique can reduce these risks and may provide the opportunity for early active rehabilitation. The aim of this study was to compare the strength of the Achillon method with the commonly used Kessler method and to assess whether the strength of the repair was related to tendon diameter. MATERIALS AND METHODS: Simulated ruptures in sheep Achilles tendons were repaired using either the Achillon method or a two-strand Kessler technique with a No. 2 Ticron suture (Tyco Healthcare, UK). Each tendon diameter was measured, and matched for both groups. Specimens were loaded to failure using an Instron tensile testing machine (Instron Limited, UK). RESULTS: Mean load to failure for the Achillon repair was 153 N+/-60 (range, 65 to 270), and the mean load to failure for the Kessler Repair was 123 N+/-24 (range, 75 to 150). This difference was not statistically significant (p=0.21). There was a statistically significant higher mean load to failure for wider tendons repaired by the Achillon method (p=0.05), however mean load to failure was not related to tendon width in Kessler repairs (p=0.23). CONCLUSION: This is the first study to compare these two methods of repair. The Achillon repair has comparable tensile strength to the Kessler Repair. CLINICAL RELEVANCE: The Achillon repair appears to be a biomechanically sound method of repair for the acutely ruptured Achilles tendon.