• Reza Firoozabadi, Timothy J O'Mara, Alan Swenson, Julie Agel, John D Beck, and Milton Routt.
• Department of Orthopaedic Surgery and Sports Medicine, Harborview Medical Center, 325 Ninth Avenue, Box 359798, Seattle, WA, 98104, USA, Rezaf2@uw.edu.
• Clin. Orthop. Relat. Res. 2014 Nov 1; 472 (11): 3383-8.

BackgroundHeterotopic ossification (HO) is a common complication of the operative treatment of acetabular fractures. Although the surgical approach has been shown to correlate with the development of ectopic bone, specific risk factors have not been elucidated.Questions/PurposesThe purposes of this study were to determine specific risk factors associated with the development of severe HO and the frequency with which patients develop severe HO after acetabular fracture fixation through an isolated Kocher-Langenbeck approach.MethodsUsing an institutional orthopaedic trauma database at a regional Level I trauma center, patients undergoing open treatment of acetabular fractures during the study period (January 2000 to January 2010) were identified. A review of medical records and imaging studies was performed on 508 patients who were treated by the senior author (MR) through an isolated Kocher-Langenbeck approach. During the study period, the senior author used indomethacin for HO prophylaxis in patients who had ipsilateral femur fracture treated with antegrade reamed medullary nailing or severe local soft tissue injury; 49 (10%) of the patients he treated with the Kocher-Langenbeck approach received prophylaxis, and they were excluded from this study, leaving a total of 459 patients who met inclusion criteria. Of those, 147 (29%) were lost to followup or did not have radiographs both before and at a minimum of 6 weeks (median, 1 week; range, 0-3 weeks), leaving 312 (61% of the patients treated with the Kocher-Langenbeck approach during this time) available for this analysis. Demographic data as well as information related to cause of injury, associated periacetabular findings, other system injuries, and treatment were gathered. Final followup radiographs were assessed for the presence of ectopic bone by two of the authors (TJO, AS) using the modified Brooker classification. Logistic regression was performed to identify possible predictors of development of severe ectopic bone.ResultsThe only predictor we identified for the development of severe HO was the need for prolonged mechanical ventilation (odds ratio, 7.1; 95% confidence interval, 2.9-17.3; p=0.001). Injury Severity Score, sex, presence of comminution, femoral head impaction, dislocation, degloving injury, debris in the joint, number of other fractures, and head and chest Abbreviated Injury Score>2 did not correlate with severe HO. Severe HO (Brooker Class III or IV) developed in 38 of 312 patients (12%).ConclusionsPatients with prolonged mechanical ventilation might benefit from HO prophylaxis given the increased risk of developing severe HO in this patient population. However, future prospective studies need to be performed to verify this finding given the fact that a considerable number of patients were prophylactically treated in this study.Level Of EvidenceLevel IV, prognosticstudy. See Guidelines for Authors for a complete description of levels of evidence.

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