A new look at the Hawkins classification for talar neck fractures: which features of injury and treatment are predictive of osteonecrosis?

Background: Osteonecrosis and posttraumatic arthritis are common after talar neck fracture. We hypothesized that delay of definitive fixation would not increase the rate of osteonecrosis, but that the amount of initial fracture displacement, including subtalar and/or tibiotalar dislocations, would be predictive. We investigated the possibility of dividing the Hawkins type-II classification into subluxated (type-IIA) and dislocated (type-IIB) subtalar joint subtypes. Methods: The cases of eighty patients with eighty-one talar neck and/or body fractures who had a mean age of 36.7 years were reviewed. The fractures included two Hawkins type-I, forty-four type-II (twenty-one type-IIA and twenty-three type-IIB), thirty-two type-III, and three type-IV fractures. Open fractures occurred in twenty-four patients (30%). Results: One deep infection, two nonunions, and two malunions occurred. After a mean of thirty months of follow-up, sixteen of sixty-five fractures developed osteonecrosis, but 44% of them revascularized without collapse. Osteonecrosis never occurred in fractures without subtalar dislocation (Hawkins type I and IIA), but 25% of Hawkins type-IIB patterns developed osteonecrosis (p = 0.03), and 41% of Hawkins type-III fractures developed osteonecrosis (p = 0.004). Osteonecrosis occurred after 30% of open fractures versus 21% of closed fractures (p = 0.55). Forty-six fractures were treated with urgent open reduction and internal fixation (ORIF) at a mean of 10.1 hours, primarily for open fractures or irreducible dislocations. With the numbers studied, the timing of reduction was not related to the development of osteonecrosis. Thirty-five patients had delayed ORIF (mean, 10.6 days), including ten with Hawkins type-IIB and ten with Hawkins type-III fractures initially reduced by closed methods, and one (5%) of the twenty developed osteonecrosis. Thirty-five patients (54%) developed posttraumatic arthritis, including 83% of those with an associated talar body fracture (p < 0.0001) and 59% of those with Hawkins type-III injuries (p < 0.01). Conclusions: Following talar neck fracture, osteonecrosis of the talar body is associated with the amount of the initial fracture displacement, and separating Hawkins type-II fractures into those without (type IIA) and those with (type-IIB) subtalar dislocation helps to predict the development of osteonecrosis as in this series. It never occurred when the subtalar joint was not dislocated. When it does develop, osteonecrosis often revascularizes without talar dome collapse. Delaying reduction and definitive internal fixation does not increase the risk of developing osteonecrosis. Level of Evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence. Peer Review This article was reviewed by the Editor-in-Chief and one Deputy Editor, and it underwent blinded review by two or more outside experts. It was also reviewed by an expert in methodology and statistics. The Deputy Editor reviewed each revision of the article, and it underwent a final review by the Editor-in-Chief prior to publication. Final corrections and clarifications occurred during one or more exchanges between the author(s) and copyeditors.