Prognostic classification of fifth metatarsal stress fracture using plantar gap.

BACKGROUND There have been diverse results even in same Torg type of fifth metatarsal stress fractures. METHODS Eighty-six cases with a fifth metatarsal stress fracture that were treated with modified tension band wiring from January 2003 to May 2009 were evaluated retrospectively. Each case was classified according to Torg's classification and a new classification. Using the new proposed classification, cases were subdivided into complete fracture and incomplete fracture. The cases of incomplete fracture were subdivided based on presence or absence of plantar gap more than 1 mm. After surgery, bone union was determined by CT. Statistical analysis of the Torg classification and time for bone union as well as the proposed new classification and time for bone union was performed. RESULTS There was a significant difference in the time for bone union among the three Torg types (P = 0.004). The mean time for bone union in group A (complete fracture, n = 32) was 67.5 ± 28.8, and it was 103.2 ± 47.7 for group B (incomplete fracture, n = 54). There was a significant difference in time for bone union between them (P < 0.001). The mean time for bone union in group B1 (incomplete fracture, plantar gap less than 1 mm, n = 16) was 73.9 ± 26.7, and it was 115.5 ± 45.4 for group B2 (incomplete fracture, plantar gap 1 mm or more, n = 38). There was a significant difference in time for bone union between them (P < 0.001). CONCLUSION The results of this study suggest that the classification incorporating the plantar gap might be used for classification of fifth metatarsal stress fractures. LEVEL OF EVIDENCE Level III, retrospective comparative series.