Objective: To determine whether radiographic measurements are predictive of involvement of the distal tibia articular surface in tibial shaft fractures.

Design: Retrospective review.

Setting: Academic level-I trauma hospital.

Patients: Two-hundred seventeen patients with tibial shaft fractures distal to the isthmus (AO/OTA: 42-A1-3;42-B1-3;42-C1-3;43-A1-3).

Intervention: Analysis of AP and lateral radiographs. The following parameters were measured: 1) Angle between the predominant fracture line and the plane of the tibial plafond ([alpha]-angle). 2) Length of the shaft fracture. 3) Distance from the most inferior extent of the shaft fracture to the tibial plafond (DTP). 4) Width of the tibial plafond. 5) Width of the tibial isthmus. 6) Ratio of fracture length to DTP (FTP). 7) Fibular fracture distance (FFD)

Main Outcome Measure: Distal intra-articular involvement (DIA).

Results: A total of 217 patients were identified, 56 (26%) with DIA. The FTP ratio as measured on both the AP (Odds-ratio 8.20, Confidence-interval 4.26-17.22, p<0.0001) and lateral radiographs (10.00, 4.78-23.23, <0.0001) was the most effective screening measurement for DIA. AP and lateral FTP ratios of 0.224 and 0.255 respectively achieved a negative predictive value (NPV) of 100%, eliminating the need for CT scans in 16-23% of injuries.

Conclusion: Involvement of the distal articular surface in patients with distal tibial shaft fractures is significantly associated with fracture geometry and pattern. The FTP ratio may be used as an effective screening tool to rule out of intra-articular involvement.

Level of Evidence: Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

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