A validated cadaveric model of trochlear dysplasia

Purpose Despite the high prevalence of trochlear dysplasia among patients with patellar instability, it is not well studied and is infrequently addressed surgically. The lack of a validated cadaveric model of trochlear dysplasia may be a contributing factor. The goal of this study was to develop a simple, reproducible, and realistic cadaveric model of trochlear dysplasia by surgically modifying cadaveric femora with normal anatomy and then to validate this model through the use of mechanical and fluoroscopic measurements. Methods The floor of the trochlear groove was surgically elevated using an inflatable bone tamp in eight cadaveric femora. The trochlear depth (TD) was measured with a custom-designed measuring device, and radiographic markers of dysplasia (sulcus angle, crossing sign, and prominence) were assessed before and after surgical modification. Results The average TD was 3.6 ± 1.4, 4.6 ± 1.1, and 5.1 ± 1.0 mm prior to reverse trochleoplasty (RT) and 1.0 ± 1.8, 2.3 ± 1.3, and 3.3 ± 2.5 mm following RT at 0°, 20°, and 40° of flexion, respectively. These direct measurements of TD were confirmed with fluoroscopy. The sulcus angle averaged 141° prior to RT and 157° after RT. The average prominence across all specimens was 3.3 ± 0.7 mm before RT, and 5.5 ± 1.5 mm after RT. Finally, the crossing sign was found to be absent in all knees prior to RT and present in 7 of the 8 after RT. Conclusions The results of this study show that elevation of the trochlear floor with an inflatable bone tamp can reproducibly create a simulated dysplastic trochlea. This model may be useful in biomechanical studies of treatments for patellofemoral instability.