• Bridget DeSandis, Conor Murphy, Andrew Rosenbaum, Matthew Levitsky, Quinn O'Malley, Gabrielle Konin, and Mark Drakos.
• Hospital for Special Surgery, New York, NY, USA desandisb@hss.edu.
• Foot Ankle Int. 2016 May 1; 37 (5): 528-36.

BackgroundPercutaneous internal fixation is currently the method of choice treating proximal zone II fifth metatarsal fractures. Complications have been reported due to poor screw placement and inadequate screw sizing. The purpose of this study was to define the morphology of the fifth metatarsal to help guide surgeons in selecting the appropriate screw size preoperatively.MethodsMultiplanar analysis of fifth metatarsal morphology was completed using computed tomographic (CT) scans from 241 patients. Specific parameters were analyzed and defined in anteroposterior (AP), lateral, and oblique views including metatarsal length, distance from the base to apex of curvature, apex medullary canal width, apex height, and fifth metatarsal angle.ResultsThe average metatarsal length in the AP view was 71.4 ± 6.1 mm and in the lateral view 70.4 ± 6.0 mm, with 95% of patients having lengths between 59.3 and 83.5 mm and 58.4 and 82.4 mm, respectively. The average canal width at the apex of curvature was 4.1 ± 0.9 mm in the AP view and 5.3 ± 1.1 mm in the lateral view, with 95% of patients having widths between 2.2 and 5.9 mm and 3.2 and 7.5 mm, respectively. Average distance from apex to base was 42.6 ± 5.8 mm in the AP and 40.4 ± 6.4 mm in the lateral views. Every measurement taken in all 3 views had a significant correlation with height.ConclusionsWhen determining screw length, we believe lateral radiographs should be used since the distance from the base of the metatarsal to the apex was smaller in the lateral view. On average, the screw should be 40 mm or less to reduce risk of distraction. For screw diameter, the AP view should be used because canal shape is elliptical, and width was found to be significantly smaller in the AP view. Most canals can accommodate a 4.0- or 4.5-mm-diameter screw, and one should use the largest diameter screw possible. Larger individuals were likely to have more bowing in their metatarsal shaft, which may lead to a higher tendency to distract.Level Of EvidenceLevel III, comparative series.© The Author(s) 2015.

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