Assessment of Posterior Cruciate Ligament Injury Using the Merchant View
Author(s): Simon M Thompson, Andrew M Williams, Jonathon Lavelle and Sam Church
Purpose: The aim of this study is to identify a radiological diagnosis of PCL injury using standard, easily obtained plain radiographs.
Methods: Between January 2009 and December 2012, 34 patients met study inclusion criteria. Retrospective evaluation was performed on radiographs with patients demonstrating a PCL injury. Findings on the merchant view were correlated with clinical examination, magnetic resonance imaging (MRI), and intraoperative findings. The exclusion criteria were other associated ligamentous injury to either knee, prior surgery to either knee or an abnormal contralateral knee. A control group of 40 patients with PCL intact knees was also assessed. Measurements were made on the merchant view to describe a radiological sign, the “tibial drop off”.
Results: Thirty four patients fulfilled the inclusion criteria. Patients with a definitive PCL rupture clearly demonstrated asymmetry in the tibial drop off between the injured knee and the normal knee. This difference was present in all injured patients. The mean PCL injured knee tibial drop off was 16.59mm (SD 2.69), compared to 3.74mm (SD 1.02) in the uninjured knee. This difference was highly statistically significant (P < .01). There was no difference in the tibial drop off between knees in the control group and no difference between the control group and the normal knee in the PCL injured group (P = .34).
Conclusion: Injury to the PCL can be identified on the merchant view obtained as part of the standard knee series radiological assessment. This investigation is readily available to all clinicians and may help guide treatment and further imaging.