Knee Chondral Shear Injury Repair: A Biomechanical Laboratory Comparison of Suture Bridge to Chondral Pin Fixation.

Abstract

BACKGROUND Delamination of chondral fragments in pediatric patients is common and is usually caused by osteochondritis dissecans (OCD) or patellar dislocations. For fragments with minimal to no bone, fixation with screws may not be ideal due to hardware prominence on the cartilage or suboptimal screw purchase, which can result in hardware migration and loss of fixation. Lower-profile chondral fixation devices may be ideal in these circumstances, such as the suture bridge fixation construct and bioabsorbable chondral pin fixation. HYPOTHESIS Suture bridge constructs would provide superior fixation over chondral pins for chondral shear injury fragments. STUDY DESIGN Controlled laboratory study. METHODS Seven pediatric cadaveric femurs were utilized. Circular lesions, 15 mm in diameter, were created on both femoral condyles. One lesion was randomized to chondral pin repair, while the other received suture bridge repair using 2-0 suture fixated with suture anchors. Each specimen was then potted before undergoing biomechanical testing on a materials testing frame. Each construct underwent precyclic rotational shear testing, cyclic loading, and postcyclic rotational shear testing. The stiffness (N·m/deg) of each repair during pre- and postcyclic rotational shear testing was recorded and compared using paired t tests. RESULTS Suture bridge fixations, compared with chondral pin fixations, demonstrated significantly higher precycle stiffness (0.0113 vs 0.0067 N·m/deg; P = .0359) and postcycle stiffness (0.0215 vs 0.0089 N·m/deg; P = .0421). While all suture bridge repairs remained intact, 5 of 7 chondral pin repairs fully detached by the end of biomechanical testing. CONCLUSION Suture bridge repair demonstrated significantly higher fixation stiffness and durability compared with chondral dart repair in the pediatric cadaveric model. CLINICAL RELEVANCE This study attempts to find the biomechanically superior construct for pediatric chondral shear injuries.