LANDMARKS USED IN MEDIAL PATELLOFEMORAL LIGAMENT RECONSTRUCTION HAVE VARIABLE TOPOGRAPHY
Figure 1 - Dissection of specimens for identification of medial landmarks performed by (A) palpation and verification of osseous landmark location by intact soft tissue (AT, MCL, MGT) and (B) reflection on the extensor mechanism after lateral parapatellar arthrotomy and identification of the medial patellofemoral ligament band under tension. The MPFL is dissected from the retinaculum and followed to its femoral footprint. (AT, adductor tubercle; GT, gastrocnemius tubercle; MCL, medial collateral ligament; ME, medial epicondyle; MGT, medial gastrocnemius tendon; MPFC, medial patellofemoral complex; MPFL, medial patellofemoral ligament; sMCL, superficial medial collateral ligament; VMO, vastus medialis oblique.)
Purpose: To describe the morphology of the adductor tubercle (AT), medial epicondyle (ME), and gastrocnemius tubercle (GT); to quantify their relationships to the medial patellofemoral ligament (MPFL) footprint location; and to classify the reliability of each landmark based on measurement variability.
Methods: Eight cadaveric specimens were dissected to expose the following landmarks on the femur: MPFL footprint, AT, ME, and GT. Using the MicroScribe 3D digitizer, each landmark was projected into a 3-dimensional coordinate system and reconstructed into a complex, closed polygon. For each specimen tubercle, the base surface area, volume, height, base:height ratio, sulcus point, and distance from the MPFL footprint center were calculated. Levene's test was performed to evaluate differences in variance of the morphologic parameters between the three osseous structures.
Figure 2 - Schematic representation of base:height ratio, which quantifies the tubercle topographical contrast with local environment.
Figure 3 - Representative figure of osseous landmarks with heatmap view of base footprints with mean area, placed relative to the medial patellofemoral ligament (MPFL) footprint center (black dot), as well as heatmap of MPFL footprint area relative to the average peak points of the osseous landmarks. Darker color indicates greater overlap between specimens. (AT, adductor tubercle; GT, gastrocnemius tubercle; ME, medial epicondyle.)
Figure 4 - Plot of major landmark peaks relative to the medial patellofemoral ligament footprint center (origin, blue dot) demonstrating projected sulcus point. (AT, adductor tubercle; GT, gastrocnemius tubercle; ME, medial epicondyle.)
Results: The ME had significantly greater variance in volume than the GT (P = .032), and the AT (17.5 ± 3.9) and GT (19.5 ± 3.6) were significantly less variable in base:height ratio than the ME (95.3 ± 19.2; P < .001). The GT was the closest to the MPFL footprint center (7.1 ± 3.1 mm) compared with the AT (13.4 ± 3.6 mm, P = .002) and ME (13.2 ± 2.7 mm, P = .003). However, the tubercles were equally variable in terms of distance to the MPFL footprint center (P = .86). Lastly, the sulcus point was estimated to be on average 1.9 ± 2.9 mm distal and 2.0 ± 2.0 mm posterior to the MPFL center point.
Conclusions: The 3 major osseous landmarks of the medial femur have significantly different variances in volume and base: height ratio. Specifically, the variability and elongated morphology of the ME differentiated this landmark from the AT and GT, which demonstrated the most consistent morphology.
Figure 5 - Density plots representing the relative distributions and variance of each anatomic parameter between landmarks. Dots represent individual specimen data points. σ2 = variance. (AT, adductor tubercle; GT, gastrocnemius tubercle; ME, medial epicondyle.)
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Published October 18, 2022 in Arthroscopy, Sports Medicine, and Rehabilitation (Volume 4 - Issue 6).