posteriorly displaced radial head fractures may represent the footprint of an elbow dislocation or subluxation as a variant of modified mason type 4

Background: the purpose of this case series is to describe surgical decision making and clinical outcomes in posteriorly displaced radial head fractures with a major fragment (more than 50% of the head) located behind the humeral condyle. we also document the outcome of open reduction and internal fixation of completely displaced radial head fractures.methods: a retrospective review of the icuc® (integrated comprehensive unchanged complete) database was performed between 2012 and 2020. patients were included if preoperative radiographs demonstrated a major radial head fracture fragment located posterior to the humeral condyle and a minimum of 2-year follow-up data was available. results: ten patients met inclusion criteria. two patients had an associated elbow dislocation whereas 8 patients did not. all patients were found to have disruption of the lateral collateral ligament complex intraoperatively. nine radial head fractures were successfully fixed with interfragmentary screws. one multi-fragmented radial head fracture could not be successfully stabilized with interfragmentary screw fixation and was resected. the average time to final followup was 4.8 years (range 2.2-8.1). at final follow-up, 6 patients demonstrated radiographic evidence of a healed radial head, 1 patient had avascular necrosis, and 2 had post-traumatic arthritis. none demonstrated radiographic instability. the average functional score was 0.64 (sd 0.81) and pain score was 0.45 (sd 0.93). the average elbow extension was 8 degrees (sd 11), elbow flexion was 139 degrees (sd 6), forearm supination was 60 degrees (sd 27), and forearm pronation was 69 degrees (sd 3).conclusion: recognition of a posteriorly displaced radial head fracture is essential, as it may be an indirect sign of elbow instability. this instability should be addressed during surgical intervention. level of evidence: iv