Transphyseal Anterior Cruciate Ligament Reconstruction Using Mesenchymal Stem Cells

Background: Conventional techniques for reconstruction of the anterior cruciate ligament in skeletally immature patients risk potential iatrogenic growth disturbance because of drilling across the physis. Animal models have demonstrated mixed results regarding growth disturbances from soft tissue grafts across the physis.Hypothesis: Mesenchymal stem cells derived from bone marrow may be effective in preventing growth arrest after intra-articular anterior cruciate ligament reconstruction.Study Design: Controlled laboratory study.Material and Methods: The anterior cruciate ligament was removed from 15 skeletally immature rabbits, which were divided into 3 groups: 5 rabbits (group 1) had only drilling of tunnels through the distal femoral and proximal tibial physes 5 (group 2) underwent drilling of the tunnels and reconstruction with an extensor digitorum communis autograft; and 5 (group 3) had drilling and reconstruction with an extensor digitorum communis autograft that had been seeded with mesenchymal stem cells. Radiographs were obtained every 3 weeks, and the animals were sacrificed 3 to 20 weeks after surgery. The surgically treated and contralateral control knees were salvaged, and each knee was examined grossly, radiographically, and histologically.Results: A bone bridge spanned the physis in all nongrafted knees (group 1) by 3 weeks after surgery. In group 2, the extensor digitorum communis autograft seemed to slow but not prevent the development of bony bridges and angular deformities. In contrast, the mesenchymal stem cell–seeded grafts (group 3) appeared to provide a marked protective effect against growth arrest and angular deformity.Conclusion: The results of this study suggest that angular deformity and growth arrest that occur after drilling across the physis during anterior cruciate ligament reconstruction can be prevented or minimized by implanting mesenchymal stem cells onto the transphyseal soft tissue graft.Clinical Relevance: These results may facilitate the development of strategies to prevent growth disturbances of the physis with intra-articular reconstructive procedures in pediatric patients.