Short Term Evaluation of an Anatomically Shaped Polycarbonate Urethane Total Meniscus Replacement in a Goat Model

Abstract

PurposeSince the treatment options for symptomatic total meniscectomy patients are still limited, an anatomically shaped, polycarbonate urethane (PCU), total meniscus replacement was developed. This study evaluates the in vivo performance of the implant in a goat model, with a specific focus on the implant location in the joint, geometrical integrity of the implant and the effect of the implant on synovial membrane and articular cartilage histopathological condition.MethodsThe right medial meniscus of seven Saanen goats was replaced by the implant. Sham surgery (transection of the MCL, arthrotomy and MCL suturing) was performed in six animals. The contralateral knee joints of both groups served as control groups. After three months follow-up the following aspects of implant performance were evaluated: implant position, implant deformation and the histopathological condition of the synovium and cartilage.ResultsImplant geometry was well maintained during the three month implantation period. No signs of PCU wear were found and the implant did not induce an inflammatory response in the knee joint. In all animals, implant fixation was compromised due to suture breakage, wear or elongation, likely causing the increase in extrusion observed in the implant group. Both the femoral cartilage and tibial cartilage in direct contact with the implant showed increased damage compared to the sham and sham-control groups.ConclusionThis study demonstrates that the novel, anatomically shaped PCU total meniscal replacement is biocompatible and resistant to three months of physiological loading. Failure of the fixation sutures may have increased implant mobility, which probably induced implant extrusion and potentially stimulated cartilage degeneration. Evidently, redesigning the fixation method is necessary. Future animal studies should evaluate the improved fixation method and compare implant performance to current treatment standards, such as allografts.

The Ovine Model for Meniscus Tissue Engineering: Considerations of Anatomy, Function, Implantation, and Evaluation

“…Direct MCL release (Fig. 3A) with subsequent suture repair is less invasive than other release protocols, 9,19,61,62 but can deteriorate MCL kinematics, leading to instability with failure rates of 6% found in human ligament reconstruction studies. 63 Epicondylar osteotomy (Fig.…”

“…19 Others have passed sutures through intraosseous tunnels and either tied the ends together around the tibia or secured with an endobutton, with limited success. 9,11,16 Merriam et al described a unique technique for the implant fixation, where extended tails were pulled through intraosseous tunnels and fixed using interference screws. 66 This method of fixation resulted in strong adherence and the prevention of extrusion, likely due to increased stiffness and healing within the bone tunnels.…”

“…8 According to Madry et al, 8 the general requirements for large animal model experiments in translational orthopedic research are that the model needs to be comparable to the human species, comparative data must be available, the results must be transferable, and the surgery must be technically feasible. Several animal models (goat, 9,10 dog, 11,12 and pig 13,14 ) have been utilized for testing both reparative and regenerative approaches to restore the original shape and function of the meniscus, 15 with sheep being the model most used. [16][17][18][19][20][21] While studies have compared sheep and human menisci with regard to anatomy, 22,23 physiology, 24 biological composition, 25 or structural mechanics 26,27 individually, in this study, we synthesize the literature and opinions from our extensive hands-on experience to establish the sheep as the appropriate animal model for meniscus tissue engineering studies.…”

The implications of non-anatomical positioning of a meniscus prosthesis on predicted human knee joint biomechanics

“…The meniscus prosthesis consists of a stiff core embedded in a soft flexible (polymer) body. Based on cadaveric and animal experiments, proper materials for the meniscus prosthesis were selected [19][20][21]. The composite structure of the meniscus prosthesis allows for flexible articulations, while simultaneously constraining excessive prosthesis deformation.…”

“…The prosthesis polymeric horns can pivot around metallic posts to minimize torque loads to the prosthesis horns [22]. Several studies have been performed to improve the geometry, material properties, and fixation technique of the meniscus prosthesis [17][18][19][20][21]23].…”