Optimal Guidewire Starting Position for Medial Column Intramedullary Fixation.

Background: Insertion of medial column intramedullary fixation during Charcot reconstruction relies on proper guidewire placement in preparation for reaming to optimize endosteal purchase. Although fluoroscopy and jigs assist with wire placement, no anatomical relationship between the center of the intramedullary canal and metatarsal head or base has been described, which this cadaver study aimed to identify.

Methods: The first metatarsals from ten fresh-frozen cadavers were dissected. The height and width of the first metatarsal head and base as well as length were measured with digital calipers. Each metatarsal was placed in a three-dimensional printed gantry, where radiographs were taken. Image analysis software was used to identify the relationship between the metatarsal head and base and the center of the intramedullary canal.

Results: Metatarsals from six male and four female cadavers with an age of 68.6 ± 15.14 years were assessed. Metatarsal length was 62.71 ± 5.54 mm. The center point was 51.12 ± 3.51% and 66.85 ± 5.09% the height of the metatarsal head and base, respectively, with the inferior cortex as reference. Moreover, the center point was 53.40 ± 6.26% and 52.63 ± 2.90% the width of the metatarsal head and base, respectively, with the lateral cortex as reference. Longer metatarsals correlated with more superior base starting positions (r = 0.74; P = .02).

Conclusions: Guidewire entry should be slightly superior and medial to the center of the first metatarsal head and directed proximally toward the superior third of the metatarsal base. These findings may assist with surgical technique and instrument design.