Stress at the second metatarsal bone after correction of hammertoe and claw toe deformity: a finite element analysis using an anatomical model.

BACKGROUND: We used finite element analysis to evaluate three techniques for the correction of hammertoe and claw toe deformities: flexor digitorum longus tendon transfer (FDLT), flexor digitorum brevis tendon transfer (FDBT), and proximal interphalangeal joint arthrodesis (PIPJA).

METHODS: We performed a finite element analysis of FDLT and FDBT compared with PIPJA of the second toe using multislice computed tomography and 93 tomographic images of the foot obtained in a healthy 36-year-old man.

RESULTS: The PIPJA showed a significantly higher increase in traction and compressive stresses and strain at the medial aspect of the shaft of the second metatarsal bone compared with FDLT or FDBT (P < .01). Mean ± SD compressive stresses increased to -4.35 ± 7.05 MPa compared with the nonsurgical foot (-3.10 ± 4.90 MPa). It can, therefore, be hypothesized that if PIPJA is used to correct the hammertoe and claw toe deformities, it could also increase traction and compressive stresses and strain in the metatarsals during running and other vigorous activities.

CONCLUSIONS: There is a biomechanical advantage to performing FDLT or FDBT instead of PIPJA to surgically treat a hammertoe or claw toe deformity. In addition, tensile strain at the dorsal aspect of the second metatarsal bone when performing PIPJA increases the risk of metatarsalgia or stress fracture in patients at risk.