Radiographic correlation of hallux MP fusion position and plate angle

Background: This study assessed the variability of plate bend in regard to final metatarsophalangeal (MP) fusion angles and toe-to-floor distance. We hypothesized that the final MP angle, the angle of the proximal phalanx to the floor, and the weightbearing toe-to-floor distance would be dictated solely by the magnitude of the bend in the plate. Materials and Methods: This is a retrospective analysis of 35 sequential patients who underwent MP fusion with a low-contour titanium plate. Postoperative weightbearing radiographs were analyzed for plate angle, MP fusion angle, the angle of the proximal phalanx to the floor, and the weightbearing toe-to-floor distance. Results: We found statistical correlation between plate angle and MP angle and between plate angle and the angle of the proximal phalanx to the floor. However, there was low correlation between plate angle and with toe-to-floor distance. In addition, we noted many outliers, which resulted in higher or lower correlation of the MP angle to the expected plate angle and, thus, a relationship between angles that was far from linear. Conclusion: Care needs to be taken when relying solely on the bend in the plate to determine the final position of the toe in MP fusions. Although the association between plate bend and MP angle and proximal phalanx to floor angle was strong, the association between the bend in the plate and weight bearing toe-to-floor distance was variable. This could result in the toe hitting the shoe or the need to vault over the toe. Therefore, the surgeon must match the plate to each patient's anatomy to ensure proper weight bearing toe-to-floor distance and not rely on plate angle exclusively.