Abstract
Category:
Midfoot/Forefoot; Trauma
Introduction/Purpose:
Proximal (zone 2 and 3) fifth metatarsal fractures are common fractures. Due to poor blood supply, these fractures are generally treated operatively due to an increased risk of nonunion. A recent study by this group used 3D CT imaging to determine guidelines for choosing the optimal screw. The study found that the screw length should stop short of the bow of the metatarsal and the screw diameter should be larger than the commonly used 4.5 mm screw to ensure endosteal fixation. The purpose of this study is to determine how well these guidelines translate to surgical outcomes, measured using Patient Reported Outcomes Measurement Information System (PROMIS) Physical Function (PF) and Pain Interference (PI) surveys.
Methods:
A retrospective review yielded 24 patients with zone 2 or 3 fractures between 2013 and 2016. Twenty-three patients met inclusion criteria and 18 patients completed preoperative and postoperative PROMIS PF and PI surveys. Radiographic measurements included pitch angle, metatarsus adductus angle, AP talo-1st metatarsal angle, Meary’s angle, and medial cuneiform height. Length of the fifth metatarsal, width of the medullary canal at the bow, and distance of fracture from the proximal tip of the fifth metatarsal were also measured. Correlation coefficients were calculated between postoperative PROMIS scores and repair characteristics (radiographic measurements, screw length, and screw diameter). Correlation coefficients were also calculated comparing change in PROMIS scores from preoperative baseline and repair characteristics. T-tests were used to determine the relationship between repair characteristics, PROMIS scores, and incidence of surgical complications - re-fractures (n=3) and non- unions (n=3).
Results:
The average screw parameters adhered to the guidelines established by our previous study. Average screw length was 42.17+-4.96mm and screw diameter was 5.38+-0.28mm. Preoperatively, PROMIS PI = 57.26+-11.03 and PROMIS PF = 42.27+- 15.45 after injury. Postoperatively, PROMIS PI = 44.15+-7.36 and PROMIS PF = 57.22+-10.93. Patients who had complications had significantly lower postoperative PROMIS PF scores (p=0.0432) compared to patients without complications. There was no significant difference (p>0.05) in other repair characteristics between those with and without complications. Metatarsus adductus angle (MAA) correlated inversely with postoperative PROMIS PF scores (r=-0.478; p=0.045). AP talo--1st metatarsal angle (r=- 0.611; p=0.007), medial cuneiform height (r=-0.59; p=0.01), and screw diameter (r=-0.525; p=0.025) had significant inverse relationships with change in PROMIS PF scores from baseline.
Conclusion:
Patients treated according to guidelines from our prior study achieved excellent outcomes as measured by PROMIS PI and PF scores. Patients with complications or excessive lateral column loading on radiograph had worse functional outcomes. Larger diameter screws may not be as important clinically as thought in radiographic/cadaveric studies, perhaps because slightly smaller diameter screws allow sufficient endosteal fixation while allowing more functionality through the metatarsal. Future studies should better characterize how screw diameter affects outcomes and whether patients with excessive lateral column loading benefit from an off-loading cavus orthotic or plantar-lateral plating.
