The Lapidus Arthrodesis: Examining the Effect of the Metatarsal Base Transfixion Screw

Abstract The modified Lapidus bunionectomy is a useful and highly powerful procedure for correcting hallux abducto valgus. Traditionally reserved for “severe” deformities, this procedure has seen a recent resurgence in the podiatric community for it's unique ability to achieve tri-planar correction of this challenging deformity. Although this procedure has been extensively studied in both biomechanical labs and the clinical arenas, no clear consensus has been achieved regarding optimal fixation for this thought-provoking procedure. The current study examined the differences in strength between commercially available five-hole locking plates with interfragmentary compression versus a crossed-screws with a third “transfixation” screw construct in a controlled setting. Ten fresh-frozen cadaveric match pair limbs (20 total limbs) were used to complete this study. Ten limbs were randomly assigned to a three-screw construct. The other 10 contralateral limbs were assigned to a commercially available five-hole locking plate (five stainless steel and five titanium alloy) with an interfragmentary lag screw construct. The first rays were then isolated and potted into a four-point bending device. The specimens were loaded to failure in a servohydraulic load frame at a controlled rate. Failure was defined as catastrophic or 3mm of plantar gapping at the arthrodesis site. The mean maximal load to failure was 310.9 ± 109.4 N for the three-screw construct. The mean maximal load to failure for the locking plate constructs was 264.1 ± 100.9 N. This difference was not statistically significant (p=0.328). These results suggest that a three-screw construct for Lapidus arthrodesis is as strong as commercially available locking plate constructs.