201 © ISAKOS 2020 G. Bain et al. (eds.), Surgical Techniques for Trauma and Sports Related Injuries of the Elbow, https://doi.org/10.1007/978-3-662-58931-1_25 Synovial Chondromatosis and Pigmented Villonodular Synovitis of the Elbow Tendai Mwaturura and Gregory Bain 25.1 Introduction 25.1.1 Synovial Chondromatosis Synovial chondromatosis is an uncommon condi- tion characterized by monoarticular metaplasia of the synovial membrane. It may be intra-articular or extra-articular, occurring in bursae. Synovial chondromatosis is reported less frequently in the elbow compared to knee and hip joints. Typical symptoms when the elbow is involved include pro- gressive swelling, catching, locking, progressive loss of extension, bursitis, and peripheral nerve compression syndromes (ulnar and posterior inter- osseous nerve PIN). A few reports of presentation mimicking malignant soft tissue tumors, such as synovial sarcoma, have been reported [1]. While a cluster of cases involving mutations in chromosome 6 [2] has been identifed, the aeti- ology of synovial chondromatosis is unknown. Synovial fbroblasts undergo changes and pro- duce cartilage and/or bone, resulting in the for- mation of nodules. Some of these nodules break away to form loose bodies, which are responsible for mechanical symptoms. Radiographically, the loose bodies are similar in size (Fig. 25.1), in contrast to those that form in arthritic elbows. An MRI can help in the diagnostic process because it will identify cartilaginous loose bodies, which will be missed on plain radiographs. In a series reported from Zurich, no recur- rences were noted in the medium term after ade- quate synovectomy and removal of loose bodies, performed either arthroscopically or open [3]. No progression to arthrosis of the elbow was noted. However, from the knee and shoulder litera- ture, it is known that recurrence of the loose bod- ies and the progression to degenerative arthritis are not uncommon. Of greater concern are the reports of a few cases of progression to chondro- sarcoma after initial histological diagnosis of synovial chondromatosis [4]. These have occurred in patients that had not undergone total synovectomy. While the reports only include one elbow, this is still a concerning feature of syno- vial chondromatosis. Although it may seem a reasonable option to consider radioactive yttrium in the treatment of synovial chondromatosis or PVNS, we are con- cerned that these benign conditions may develop malignant transformation. T. Mwaturura · G. Bain (*) Department of Orthopaedic Surgery, Flinders University, Flinders Medical Centre, Adelaide, SA, Australia e-mail: admin@gregbain.com.au 25 Electronic supplementary material The online version of this chapter (https://doi.org/10.1007/978-3-662-58931- 1_25) contains supplementary material, which is available to authorized users.