Proximal Versus Joint Line Medial Collateral Ligament Trephination (Pie-Crusting): Effects on Meniscal Extrusion and Tibiofemoral Contact Mechanics in a Cadaveric Model

Background: Medial collateral ligament (MCL) trephination (ie, “pie-crusting”) is used to improve visualization and working space within the medial compartment during knee arthroscopy, but the variability in techniques raises concern for meniscotibial ligament injuries, meniscal extrusion (ME), and altered joint contact mechanics. Purpose: To evaluate the effects of proximal versus joint line MCL trephination on ME and knee contact mechanics. Study Design: Controlled laboratory study. Methods: A total of 10 fresh-frozen cadaveric knees (5 matched pairs) were allocated to 2 groups: proximal trephination and joint line trephination (n = 5 each). Measurements were obtained in the intact condition and repeated after percutaneous MCL trephination. The medial joint opening was assessed arthroscopically and radiographically. Under a 1000-N axial load applied for 30 seconds at 0° and 30° of knee flexion, ME was measured radiographically, and tibiofemoral contact pressure and contact area were recorded using an intra-articular pressure sensor. All statistical analyses were performed using commercial software. Results: The cadaveric specimens had a mean age of 61.4 years. The joint line group required more needle pokes to achieve adequate release. Both techniques increased the medial joint opening and ME relative to baseline (all P ≤ .05), while no significant changes in contact pressure or area were noted. Contact pressure was higher after joint line trephination at full extension ( P = .018) and 30° of flexion ( P = .035), although after adjusting for the number of needle pokes, a significant difference was only noted at full extension ( P = .024). Compared with proximal trephination, joint line trephination produced greater increases in ME at full extension ( P = .026) and 30° of flexion ( P < .001) as well as a greater decrease in contact area at full extension ( P = .021). Conclusion: When comparing joint line and proximal MCL trephination in a cadaveric model, both techniques increased the medial joint opening and ME; however, joint line trephination caused greater extrusion and less favorable contact mechanics than proximal trephination. Further in vivo studies are needed to determine the clinical relevance of these findings. Clinical Relevance: This research characterized the biomechanical effects of MCL trephination location on ME and joint contact mechanics. This knowledge supports favoring proximal trephination to limit iatrogenic disruption of the medial compartment.