Anatomy of the Lateral Plantar Ligaments of the Transverse Metatarsal Arch.

BACKGROUND

While the anatomy of the Lisfranc complex is well understood, the lateral tarsometatarsal ligamentous structures, in contrast, are less well studied. Our aim in this study was to identify an anatomical explanation as to why the second to fifth metatarsals function as a unit in homolateral and divergent midfoot injuries.

METHODS

Eleven cadaveric lower limbs, preserved in formaldehyde, were examined at the University of Liverpool Human Anatomy and Resource Centre. Each of the lower limbs was dissected to identify the plantar aspect of the transverse metatarsal arch.

RESULTS

On removal of the long plantar ligament, the peroneal longus tendon was visible, as was its insertion onto the first metatarsal base. A lateral Lisfranc ligament (which was a transverse suspensory metatarsal ligament) spanned between the bases of the second and fifth metatarsals in all specimens with an average length of 33.7 mm and width of 4.6 mm. This ligament has not previously been described. It was noted that in all specimens, the long plantar ligament blended with the lateral Lisfranc ligament. In addition to the lateral Lisfranc ligament, separate intermetatarsal ligaments were identifiable connecting each metatarsal. The long plantar ligament provided a connection through the lateral Lisfranc ligament connecting the transverse and longitudinal arches of the foot.

CONCLUSION

We found a plantar ligament that provided connection through the long plantar ligament of both the transverse and the longitudinal arches. It spanned from the second to the fifth metatarsal, which we believe may explain that in some cases, lateral instability can be overcome when the middle column is stabilized.

CLINICAL RELEVANCE

We suspect that in the majority of homolateral and divergent types of tarsometatarsal injuries that the lateral Lisfranc ligament remains intact and thus it has significant clinical ramifications.