Synovial osteochondromatosis (SOC) rarely occurs in the hip joint (4.8% reportedly). Three cases of SOC including an atypical variety are presented. In case one (32 year-old female), multiple loose bodies were revealed by the arthrogram, and extirpation of the free bodies and partial synovectomy were performed. Seven years postoperatively, osteoarthrosis is suspected.
In case two (63 year-old female), erosion of the femoral neck and a synovial tumor were observed by MRI. The invasive chondroma originating from the synovia was confirmed as SOC by biopsy. Total synovectomy and bipolar endoprosthetic replacement were performed, and the patient was rated at ninety three points according to the JOA scoring system eleven months postoperatively.
In case three (40 year-old female), enlargement of the femoral head with osteoarthrosis was observed with loose bodies. Total synovectomy and bipolar endoprosthetic replacement was performed, and the patient was rated as having ninety points by JOA scoring.
Milgram proposed synovectomy in phase I for patients such as case one, or only extirpation of loose bodies in phase II for cases two and three. However, endoprosthetic replacement was indicated for advanced osteoarthrosis or for erosion of the femoral neck for the treatment of SOC, while synovectomy should be limited in SOC of the Hip joint.
