Finite element analysis of Scarf osteotomy for precise treatment of hallux valgus

The treatment of hallux valgus is currently in face of many challenges in clinical practice. Although conventional surgical procedures can correct deformities to a certain extent, some key parameters such as osteotomy displacement and angle are often difficult to determine, leading to increased uncertainty in surgical outcomes and a relatively high incidence of postoperative complications.

Hallux valgus is a common foot deformity that often leads to pain, difficulty in walking, and other health problems, seriously affecting the quality of life of patients. In order to provide patients with more precise treatment, we aimed to simulate the Scarf osteotomy for the treatment of hallux valgus using the finite element method, and comparatively analyze the mechanical performance indicators under different distal osteotomy displacements. We hoped to provide scientific and reasonable treatment plans for clinical practice and better treatment outcomes for patients.

A volunteer with moderate hallux valgus was selected as the research subject in this study. Preoperative plantar pressure test was conducted, and the CT data of the patient's affected foot was collected to create the finite element model using finite element software. After verifying the validity of the model, it was used to simulate the translational Scarf osteotomy under different settings. Specifically, the distal end of the bone fragment was pushed outwards by varying distances (2 mm, 4 mm, 6 mm, and 8 mm) and was fixed with screws. The maximum Von Mises stresses on the first to fifth metatarsal bones, the sole and the heel under four different surgical settings were compared with the preoperative values, and the changes in the maximum Von Mises stress on the screws were examined.

When the distal end of the bone fragment was pushed outwards by 6 mm, the maximum Von mises stress on the first metatarsal bone (9.4711 MPa) reached its highest value, while the maximum Von mises stresses on the second and third metatarsal bones (0.34062 MPa and 1.6246 MPa, respectively) and on the screws (40.99 MPa) were at the lowest values. The maximum plantar pressure detected during static test was 0.292 MPa, while the maximum plantar stress observed in the finite element model was 0.25733 MPa, indicating comparable values between the two.

Based on precise and customized preoperative design and finite element analysis, it was found that the Scarf osteotomy with the distal end of the bone fragment pushed outwards for 6 mm could yield the best treatment effect for hallux valgus. Under this setting, the stress on the first metatarsal bone was the highest, while the stresses on the second and third metatarsal bones were the lowest, suggesting that it can relieve the stress on lateral metatarsal bones and improve the stress distribution of the forefoot. Overall, Scarf osteotomy under 6 mm setting can effectively correct hallux valgus deformity, reduce the incidence of metastatic plantar pain and prevent the recurrence of metastatic plantar pain after surgery. By improving the patient's plantar stress distribution, this surgical setting is expected to provide better clinical outcomes.