LAUSR

Abstract Background Fractures of the proximal fifth metatarsal are common, and often they are classified using a three-part scale first proposed by Lawrence and Botte. A clear consensus on prognosis and treatment for these fractures is lacking, particularly for fractures in the middle classification, Zone 2; the reliability of the classification scheme itself may be partly at fault for this. The intra- and interrater reliability of the classification itself has never been established, and it remains unclear whether the three-part classification of fifth metatarsal fractures can be applied consistently enough to guide treatment. Questions/purposes When used by experienced orthopaedic surgeons, (1) What is the overall interrater reliability of the three-part Lawrence and Botte classification of fifth metatarsal base fractures? (2) What is the overall intrarater reliability of the three-part Lawrence and Botte classification of fifth metatarsal base fractures? (3) What are these same metrics for the individual transitions within the classification (Zone 1-2 and Zone 2-3)? Methods Thirty sets of initial presentation radiographs representing an equal number of fractures originally diagnosed by treating clinicians as Zone 1, Zone 2, and Zone 3 were evaluated and classified by three orthopaedic surgeons specializing in foot and ankle surgery and eight foot and ankle fellows to determine interrater reliability. Two weeks later, the same set of radiographs were reevaluated in random order to determine intrarater reliability. Kappa values for interrater and intrarater reliability were calculated. Additionally, the individual transitions between zones were separately analyzed by calculating kappa values for a hypothetical two-part classification based on each transition. Results The three-part Lawrence and Botte classification of fifth metatarsal fractures demonstrated an overall interrater agreement of κ = 0.66 (observed agreement 77% versus chance agreement 33%). Intrarater reliability for the 11 surgeons ranged from κ = 0.60 to κ = 0.90. A two-part scheme divided by the transition between Zone 1 and Zone 2 demonstrated an interrater agreement of κ = 0.83, and a two-part scheme divided by the transition between Zone 2 and Zone 3 demonstrated a much lower interrater reliability of κ = 0.66. Conclusion The three-part Lawrence and Botte classification system demonstrated a concerningly low level of interrater reliability with an observed agreement of 77% compared with a chance agreement of 33%. The primary source of concern is the assessment of the interface between Zone 2 and Zone 3, which proved much less reliable than that between Zone 1 and Zone 2. This suggests that previous studies of isolated Zone 1 fractures likely contain a homogeneous fracture cohort, whereas studies of Zone 2 or Zone 3 fractures are likely to include a mixture of fracture types. In practice, the consensus treatment of fifth metatarsal fractures differs based on whether they represent a more proximal, avulsive injury or a more distal injury from indirect trauma. Our data suggest that the Lawrence and Botte classification should be abandoned. Further work should focus on developing a new classification scheme that demonstrates improved interobserver reliability and more directly corresponds to this treatment paradigm. Level of Evidence Level III, diagnostic study.