In vivo heterotopic culturing of prefabricated tendon grafts with mechanical stimulation in a sheep model M. Petri a, ⁎, P. Lu a , M. Omar a , M. Ettinger b , C. Krettek a , C. Neunaber a,1 , M. Jagodzinski c,1 a Trauma Department, Hannover Medical School (MHH), D-30625 Hannover, Germany b Department of Orthopedic Surgery, Hannover Medical School (MHH), Hannover, Germany c Department of Orthopedic Trauma, Agaplesion Ev. Hospital Bethel, Bückeburg, Germany article info abstract Article history: Received 11 November 2017 Received in revised form 21 January 2018 Accepted 19 February 2018 Available online xxxx Background: The goal of this study is to investigate the biomechanical and histological properties of in vivo heterotopically prefabricated cruciate ligament replacement grafts with and without mechanical stimulation. The clinical goal is to heterotopically prefabricate a bone–tendon–bone graft for anterior cruciate ligament reconstruction, which allows rapid ingrowth and early full weight bearing. Methods: In a sheep model, eight quadriceps tendon grafts were harvested and introduced into culture chambers at their proximal and distal ends. In group S, four tendon-chamber constructs were mechanically stimulated by direct attachment to the quadriceps tendon and patella. In group NS, the same constructs were cultured without proximal attachment. All sheep were sacrificed six weeks postoperatively and the constructs were examined biomechanically and histologically. The healthy contralateral ACL and quadriceps tendon were used as controls. Results: Macroscopically, no obvious ossification could be observed at the ends of the tendon- chamber constructs six weeks postoperatively. Histologically, the tendon tissue from the mechan- ically stimulated constructs revealed higher counts of cells and capillaries. However, there was less regular cell distribution and collagen fiber orientation compared to the control group. In addition, osteoblasts and osteogenesis were observed in the prefabricated constructs both with and without mechanical stimulation. Biomechanically, there were no significant differences in stiffness, elongation and ultimate failure load between the groups. Conclusion: In vivo heterotopic culture of prefabricated tendon grafts may have the potential to stimulate osteoblasts and induce osteogenesis. Future studies with longer follow-up and modifications of the surgical technique and culture conditions are desirable. © 2018 Published by Elsevier B.V. Keywords: Heterotopic culturing Prefabricated tendon grafts Anterior cruciate ligament reconstruction Mechanical stimulation Tendon-chamber construct 1. Introduction The anterior cruciate ligament (ACL) plays an important role in maintaining knee joint stability and is the most commonly injured ligament in the knee, particularly in association with sports-related injuries [1]. Episodic pain and instability of knee, chondral and meniscal impairment, and early osteoarthritis have been reported in patients who were subjected to chronic ACL The Knee xxx (2018) xxx–xxx ⁎ Corresponding author. E-mail address: petri.maximilian@mh-hannover.de (M. Petri). 1 C. Neunaber & M. Jagodzinski contributed equally to this study. THEKNE-02583; No of Pages 11 https://doi.org/10.1016/j.knee.2018.02.006 0968-0160/© 2018 Published by Elsevier B.V. Contents lists available at ScienceDirect The Knee Please cite this article as: Petri M, et al, In vivo heterotopic culturing of prefabricated tendon grafts with mechanical stimulation in a sheep model, Knee (2018), https://doi.org/10.1016/j.knee.2018.02.006