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Chapter 11292In 2017, Roychoudhury et al.(8) published a prospective study evaluating the outcomes of TJR surgery along with the placement of AFG transplantation in 11 patients who suffered of TMJ ankylosis. They found a significant increase in MIO without adverse effects regarding the occlusion nor the QoL.DiscussionThe technique of AFG transplantation in the TMJ was first documented by Blair(1,3) in 1913 as a treatment of ankylosis and in 1992 Thomas et al.(9) first described the use of AFG transplantation as a means of prevention of fibrosis and heterotopic calcification in hip prosthesis surgery. Heterotopic bone formation can be defined as the pathological formation of osseous tissue in nonskeletal tissues. While this process is not yet fully understood, it is currently presumed that trauma, such as surgery, resulting in the activation of the inflammatory system, as well as the innate immune system and the nervous system can lead to heterotopic bone formation. Through one of these systems, the production of several osteoinductive cytokines and growth factors such as skeletal growth factor can be promoted, leading to the differentiation and proliferation of mesenchymal stem cells into osteogenic cells. This can then lead to an overactivation of the bone morphogenetic proteins cascade, which, in a permissive environment, will result in heterotopic bone formation.(7,10)While several preventive techniques such as the use of nonsteroidal anti-inflammatory drugs (NSAIDs), bisphosphonates, and extracorporeal shock-wave therapy have been described, the preferential technique for prevention of fibrosis and calcification after prosthesis placement in orthopedic surgery is postoperative low-dose radiation.(7,10) However, due to the various side effects of radiation, the increased incidence of radiation-induced sarcomas as reported by several authors, and the important anatomical structures of head and neck, this option is best avoided.(7) The use of bisphosphonates is an unattractive option for obvious reasons as well and the use of NSAIDs can lead to gastrointestinal side effects, limiting the duration of application.(10)Nikolas de Meurechy NW.indd 292 05-06-2024 10:15