Arthrodesis of the first metatarsophalangeal joint-A biomechanical comparison of four fixation techniques.

Background: Arthrodesis of the first metatarsophalangeal joint is a commonly performed orthopaedic procedure. The optimum method of fixation and joint surface preparation has yet to be determined.

Methods: This study compared four fixation techniques: Biomechanical grade sawbones were used. The dorsal plate used was a titanium, anatomically contoured locked plate. Testing was performed using an Instron machine applying force from the plantar aspect of the fused joint. Each fused sample was tested to failure. Stiffness, as calculated from the force-displacement curve, and ultimate load tolerated were recorded for each sample. The method of failure of each sample was also documented.

Results: Constructs arthrodesed using dorsal plate with separate screw groups, regardless of method of joint preparation, were the stiffest (p<0.001). The weakest construct was dorsal plate alone without interfragmenary screw. There was no difference in stiffness between planar and cup-cone joint preparation (p=0.99). Maximum load tolerated was similar when comparing Crossed Screws with dorsal plate with screw with either cup-cone or planar reaming (p=0.93, p=0.89 respectively). Dorsal plating alone tolerated a significantly lower maximum load than Plate with Screw Groups or Crossed Screws (p<0.001).

Conclusion: This study confirms that an IFS combined with a dorsally positioned locked-plate is the ideal construct, with the joint preparation technique of little consequence.