Different Internal Fixation Methods for Sanders Type II and III Calcaneal Fractures: A 5-Year Retrospective Study and Finite Element Analysis

Objective: Soft tissue defects and postoperative wound healing complications related to calcaneus fractures may result in significant morbidity. The aim of this study was to investigate whether percutaneous minimally invasive screw internal fixation (PMISIF) can change this situation in the treatment of calcaneal fractures, and aimed to explore the mechanical effects of different internal fixation methods on Sanders type III calcaneal fractures through finite element analysis.

Methods: This retrospective analysis focused on 83 patients with Sanders II and III calcaneal fractures from March 2017 to March 2022. Among them, 32 patients underwent PMISIF, 24 patients underwent tarsal sinus incision plate internal fixation (TSIPIF), and 27 patients underwent extended lateral incision plate internal fixation (ELIPIF). The present study aimed to compare various parameters, including the perioperative hospital stay, intraoperative blood loss, operative time, postoperative drainage volume, incidence of postoperative wound complications, and Gissane angle and Bohler angle data before surgery, after surgery, and at the last follow-up, among the three treatment groups. Additionally, three different finite element models were created to simulate Sanders III calcaneal fractures treated with PMISIF, TSIPIF, and ELIPIF. The models were subjected to longitudinal stresses of 350 and 700 N, and the displacement and stress distribution were analyzed to compare the stability of each model.

Results: Compared with ELIPIF and TSIPIF, PMISIF has several advantages, including shorter operative times, smaller incisions, shorter hospital stays, and lower incidences of postoperative complications. At the 12-month time point after the operation, the percentages of patients with excellent and good American Orthopedic Foot and Ankle Society (AOFAS) functional scores were 96.9%, 91.7%, and 96.2%, respectively, for the three methods, demonstrating similar outcomes. Intraoperative blood loss in the PMISIF group was comparable to that in the TSIPIF group and lower than that in the ELIPIF group. There were no significant differences in the Gissane or Bohler angles among the three groups before or after the operation. However, the differences in the Gissane and Bohler angles after the operation within each group were statistically significant compared with those before the operation. Finite element analysis revealed that stress in all three internal fixation models was primarily concentrated on the subtalar articular surface, whereas displacement was mainly observed on the medial side of the subtalar articular surface. The peak stress and displacement of bone fragments and implants in the PMISIF model were lower than those in both the TSIPIF and ELIPIF models.

Conclusion: PMISIF can achieve excellent and good rates comparable to those of TSIPIF and ELIPIF. Additionally, this approach offers the advantages of reduced operative trauma, a lower incidence of complications, and shorter preoperative preparation and hospitalization times. Furthermore, this approach can achieve a similar level of biomechanical stability.