... OF THE TIBIAL. INSERTION OF THE POSTERIOR CRUCIATE LIGAMENT (PCL) ALONG ... medial tibial plateaus was used as a reference for the PCL facet.
RADIOGRAPHIC QUANTIFICATION OF THE LOCATION OF THE TIBIAL INSERTION OF THE POSTERIOR CRUCIATE LIGAMENT (PCL) ALONG THE FACET Salim R, Zheng L, Carey R, Zhang X, Harner C Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA
INTRODUCTION The reported incidence of PCL injuries ranges from 3% to 37% among all knee injuries (1, 2, 3). Rupture of the PCL occurs most often as part of a multiligament injury (4, 5) and it has been shown to alter the kinematics of the knee. Interest in the reconstruction of the PCL has grown recently. As transtibial tunnel drilling is the most commonly used technique in PCL reconstruction (6), the objective of this study was to enhance recognition of the anatomical landmarks to facilitate location of the tibial tunnel intraoperatively. It has been suggested that radiographic imaging of the PCL facet can provide a reliable landmark for the anatomic insertion of the PCL (7). In our study we measured the insertion site as a percentage of the PCL facet length on X-ray images and validated our measurements using CT-based 3D knee bone models. METHODS Twenty fresh-frozen cadaveric knees were used. The joint was disarticulated and all soft tissue and the capsule were removed, leaving the tibial insertion of the PCL intact. For each knee, the centroid of the insertion site was measured using two methods as a percentage of a “PCL facet line,” which was identified on lateral knee imaging as a cortical line obliquely oriented to the tibial plateaus, with a posterior slope (Figure 1). The proximal articular extremity was defined as point 0% and the distal extremity (posterior cortical), 100% (7) (Figure 1).
X-ray measurements. A Kirschner wire was inserted in the center of the PCL under direct visualization (posterior to anterior view). Lateral radiographic images of the knees were taken with the k-wires in place and the entire PCL facet visible (Figure 1A). The entry point was measured from the center of the k-wire to the point 0% of the PCL facet, thus determining the percentage of the PCL facet. Bone model measurements. The PCL insertion site was digitized and mapped onto a CT-based 3D knee bone model (8) in a lateral view to visualize the PCL facet (Figure 1B). The centroid of the insertion site was projected onto the PCL facet and its location along the facet was measured. A Bland-Altman statistical approach was used to test for significant differences between methods. RESULTS The average insertion site location was 69.68%±4.9% of the PCL facet in the X-ray images and 71.71%±5.8% in bone models. No significant difference between methods was found (t paired test, p=0.13). DISCUSSION The central and posterior depression between the lateral and medial tibial plateaus was used as a reference for the PCL facet. The insertion site of the PCL was found at approximately 70% of the facet. We believe that locating the PCL insertion according to the facet on lateral X-ray view may be a more reliable and easily available parameter for reconstructive surgeries. REFERENCES 1. Fanelli GC, et al., (1993). Arthroscopy, 9 : 291-4. 2. Arendt E, et al., (1995). Am J Sports Med, 23: 694-701. 3. Parolie J, et al., (1986). Am J Sports Med, 14: 35-8. 4. Fowler PJ, et al., (1987). Am J Sports Med, 15(6): 553-557.
5. Kim YM, et al., (2011). Am J Sports Med, 39(2): 425-434. 6. Dennis MG, et al., (2004). J Knee Surg, 17: 133-9. 7. Moorman III, et al., (2008). Arthroscopy, 24(3): 24269-275 8. Li K, et al., (2009). J Biomech, 42(15): 2624-6.
Figure 1. A.) Lateral X-ray view of the knee demonstrating the k-wire trajectory and the entry point in the PCL facet centroid. B.) Bone model of the knee showing the PCL facet and the centroid.
