Abstract
The first MTP Joint (MTPJ) is critical in normal gait. MTPJ replacements treat the articular surface as a hemisphere, as it appears radiographically. In reality the articular surface has two grooves to accommodate sesamoids and facilitate a better range of motion. We compare a standard hemispherical and a modified grooved implant. Six cadaver feet were implanted with Toefit 1st MTPJ replacements and sequentially four different metatarsal head implants. Two of the metatarsal heads had grooves. The intact joints were used as a baseline for comparison, with their measurements taken before implantation. Each construct had a standard dorsiflexion force applied (50N).
Flexion angle was measured on lateral radiographs. Contact pressure and area were measured with a pressure transducer (Tekscan I-Scan 6900 electronic pressure sensor).
The anatomical (grooved) implants showed higher flexion angles and lower contact pressures in each case although there were too few trials to reach statistical significance.
Results suggest a tendency towards better flexion and contact pressure characteristics in a more anatomical device. This may lead to better clinical outcomes for 1st MTPJ replacements.
