Factors Influencing the Nonunion Rate Following First Metatarsophalangeal Joint Arthrodesis

CATEGORY: Midfoot/Forefoot INTRODUCTION/PURPOSE: The choice of fixation, biomechanical stability, and hardware density might influence the union after the first metatarsophalangeal (MTP) arthrodesis. This study aimed to assess the influencing factors on the union rate and fixation failure after MTP-1 arthrodesis. METHODS: In this retrospective cohort study, we included 359 patients with 378 feet from the practice of two foot and ankle surgeons. The surgical technique was identical. The providers randomized patients to receive either the locking plate or cross screws, which comprised 187 (50%) plate fixation and 191 (50%) cross screw fixation. Radiographic union was assessed at three months and the final follow-up and was further categorized as symptomatic versus asymptomatic nonunion. RESULTS: Accounting for potential interaction between variables using multivariable logistic analysis, plate fixation (P=0.018), and diabetes (P=0.044) were significantly associated with a higher nonunion rate. At three month follow-up, 15 (8.3%) patients in the locking plate group and 5 (2.5%) patients in the cross screws group showed nonunion. Of 15 nonunion with plate fixation, 6 (40%) underwent a second surgery because of device failure, while none of the screw fixations required a second surgery (P<0.001). In comparison to asymptomatic nonunion, remaining symptomatic at three months follow-up was a significant risk factor for developing a nonunion with possible device failure at the final follow-up requiring intervention. CONCLUSION: Cross screw fixation is significantly associated with a lower nonunion, device failure, and secondary surgery rate than plate fixation, which might be related to contact surfaces and biomechanical stability. Besides, the cost saving is more with the cross screws than plate and screws. Diabetic patients should be counseled about the higher nonunion rate.