Correlation Between Anatomic Landmarks and Bony Trough Position in Lateral Meniscal Allograft Transplant

BACKGROUND: Determining the rotational axis of the bony trough during lateral meniscal allograft transplant (MAT) is difficult. The use of anatomic landmarks may help a surgeon determine the rotational alignment of the graft during the procedure. PURPOSE: To investigate the association between the knee's anatomic landmarks and the position of the bony trough to prevent extrusion after lateral MAT. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Enrolled were 44 patients who underwent lateral MAT between July 2000 and February 2011. The patients’ mean age at the time of surgery was 30.8 years. Extrusion was measured on magnetic resonance imaging (MRI) scans at a mean of 3.6 months postoperatively, and patients were divided into an extrusion group (n = 15) and a no-extrusion group (n = 29). Three coronal MRI scans from each patient were selected, each from the region at the level of the tibial tuberosity (TT), the anterior bony trough, and the posterior bony trough. We measured the distance between the center of the anterior bony trough and the center of the TT (the TT distance) and the distance between the center of the posterior bony trough and the medial border of the lateral femoral condyle (LFC) (the LFC distance). RESULTS: The mean center of the anterior bony trough was in a more medial position relative to the center of the TT in the no-extrusion group (–2.9 ± 4.8 mm) compared with the extrusion group (1.3 ± 4.9 mm; P = .010). The mean center of the posterior bony trough was in a more medial position relative to the medial border of the LFC in the no-extrusion group (–1.7 ± 3.9 mm) compared with the extrusion group (1.0 ± 3.2 mm; P = .027). Both TT distance and LFC distance were significantly correlated with extrusion (P = .005 and .025, respectively). The cutoff value was –0.24 mm for the anterior bony trough and –0.58 mm for the posterior bony trough (negative values indicate that the trough was medial to the respective landmarks). CONCLUSION: To prevent extrusion of the allograft, the center of the anterior bony trough needs to be aligned with the center of the TT, and the center of the posterior bony trough needs to be aligned with the medial border of the LFC.