Patellar facet maturation and trochlear depth in the early pediatric age group: A 3D laser scanning analysis of developmental interplay

Background: The progression and timing of patellar development have been minimally investigated and the reciprocal influence of patellar and trochlear morphology remains poorly understood. A detailed characterization of age-related surface anatomy is essential to understand the developmental interplay between these structures. The objectives of this study were as follows: (1) to characterize the geometric development of the patellar articular surface and its facets in relation to age and (2) to define the age-based progression of soft tissue footprints on the patella. Methods: Fifty-seven immature cadaveric knees (age: 1 month to 11 years; 63% male) underwent standardized dissection by fellowship-trained orthopaedic surgeons. A coordinate-measuring device with integrated laser scanning recorded 3D cartilaginous, bony, and soft tissue anatomy. Trochlear cartilage sulcus angles (SAs) were analyzed at 30°, 60°, and 90° of flexion. Results: The average number of patellar facets increased significantly with age (p < 0.001). All specimens with a deep sulcus (SA <150°) demonstrated multiple medial and lateral facets. While the absolute dimensions of the quadriceps insertion (r = 0.69; p < 0.001), patellar tendon insertion (r = 0.65; p = 0.001), and medial patellofemoral ligament insertion (r = 0.45, p = 0.032) increased significantly with age, their proportional relationship to the total patellar cartilage surface area remained isometrically stable across all age groups (p > 0.05). Conclusions: Patellar facet complexity is an active developmental process emerging early and directly influenced by trochlear depth. Although soft tissue footprints expand in absolute size with age, they maintain a constant proportional relationship to the maturing articular surface. These findings provide normative data for patellar stabilization procedures in the early pediatric population.