Mechanical and Microstructural Properties of Pediatric Anterior Cruciate Ligaments and Autograft Tendons used for Reconstruction
BackgroundOver the last several decades there has been a steady increase in pediatric ACL tears, particularly in young female basketball and soccer players. Because allograft tissue for pediatric ACL reconstruction (ACLR) has shown high rates of failure, autograft tissue may be the best option for ACLR in this population. However, the differences in structure and mechanical behavior of these tissues are not clear.\n\nPurposeThis study sought to characterize mechanical and microstructural properties in pediatric ACLs and autograft tissues using a rare cadaveric cohort (mean age 9.2 years).\n\nStudy DesignDescriptive laboratory study.\n\nMethodsACLs, patellar tendons, quadriceps tendons, semitendinosus tendons, and iliotibial bands (ITBs) were harvested from five fresh-frozen pediatric knee specimens (3M, 2F) and subjected to a tensile loading protocol. A subset of contralateral tissues were analyzed using brightfield, polarized light, and transmission electron microscopy.\n\nResultsPatellar tendons exhibited values for ultimate stress (5.2{+/-}3.1 MPa), ultimate strain (35.3{+/-}12.5%), and Youngs Modulus (27.0{+/-}8.0 MPa) that were most similar to the ACL (5.2{+/-}2.2 MPa; 31.4{+/-}9.9%; 23.6{+/-}15.5 MPa). Semitendinosus tendons and ITBs were stronger but less compliant than the quadriceps or patellar tendons. ITBs exhibited crimp wavelengths (24.3{+/-}3.1 um) and collagen fibril diameters (67.5{+/-}19.5 nm) that were most similar to the ACL (24.4{+/-}3.2 um; 69.7{+/-}20.3 nm).\n\nConclusionThe mechanical properties of the patellar tendon were almost identical to that of the ACL. The ITB exhibited increased strength and similar microstructure to the native ACL. These findings are not entirely congruent to studies examining adult tissues.\n\nClinical RelevanceResults suggest that ITB tissue may be the preferable choice as an autograft tissue in pediatric ACL reconstructions.\n\nKey TermsPediatric, ACL reconstruction, mechanical properties, microstructural properties, patella tendon grafts, quadriceps tendon grafts, hamstring grafts\n\nWhat is Known about the SubjectDue to the extreme rarity of pediatric cadaveric specimens, very little is known about these tissues.\n\nWhat this Study Adds to Existing KnowledgeThis suite of data can be used to further optimize the design and selection of grafts for reconstruction and may provide insight into the development of constitutive musculoskeletal models.