Biomechanical Comparison of a Locking Plate with Intraplate Compression Screw Versus Locking Plate with Plantar Interfragmentary Screw for Lapidus Arthrodesis: A Cadaveric Study

Lapidus arthrodesis (first metatarsal cuneiform arthrodesis) has become an accepted procedure for hallux abducto valgus. Several variations of fixation have been described. Earlier weightbearing postoperatively has been one reported benefit of using locking plates for fixation. Additionally, studies have demonstrated that fixation placed on the plantar or tension side of the arthrodesis increases the biomechanical advantage. We performed a biomechanical cadaveric study of the Lapidus procedure, comparing a previously reported technique using a low profile locking plate with an intraplate compression screw versus the same locking plate with a plantar interfragmentary screw (PIFS) placed on the tension side of the arthrodesis in 10 fresh, paired, cadaver limbs. The mean ultimate load of the plate with a PIFS was 383.2 ± 211.5 N, and the mean ultimate load of the plate with an intraplate compression screw was 205.5 ± 97.2 N. The mean ultimate load of the LPS Lapidus plate with a PIFS was statistically greater (p = .027) than that with the plate intraplate compression screw. Our results indicated that changing the orientation of the compression screw to a PIFS significantly increased the stability of the Lapidus arthrodesis fixation construct. The modified construct with the PIFS might decrease the incidence of nonunion and, ultimately, allow patients to bear weight faster postoperatively.