Measurement of transverse forces between the first and second metatarsals: a cadaveric study

BACKGROUND: This study was designed to measure transverse forces between the 1st and 2nd metatarsals after reducing the intermetatarsal angle (IMA) in normal and hallux valgus (HV) feet, during non weight-bearing and weight-bearing phases of gait. METHODS: Four cadaver feet, three normal and one with hallux valgus, were used. A new suture button device (CyclaPlex™) composed of screw-type buttons connected with a wire was implanted at the mid-shaft of the 1st and 2nd metatarsals of all the feet. IMA was reduced using a tensioning device to pull the wire which was secured laterally at the 1st metatarsal. The 1st metatarsal was pulled laterally towards the 2nd metatarsal until an IMA of about 6° was achieved. The amount of force applied at this point was registered on the force indicator. Each foot attached to the tensioning device was placed in a special construct loaded with weights equal to the original body weight of the donor and positioned at 15° tilt (simulating propulsion phase of the gait cycle). The intermetatarsal force under load indicated on the tensioning device was recorded. RESULTS: The average recorded transverse intermetatarsal force was 28.5 N (SD 4.2 N) during non weight-bearing phase; the mean increase in the measured force at weight-bearing and 15° tilt was 6 N (SD 2.6 N). CONCLUSIONS: We measured the transverse forces between the 1st and 2nd metatarsals with the use of a suture button device (CyclaPlex™). The data obtained from the measurements will provide a better understanding of foot biomechanics and may therefore also facilitate the development of new devices designed to decrease IMA in HV surgery.