Possible Transformation of Pseudotumor to Synovial Sarcoma in a Failed Metal-on-Metal Total Hip Arthroplasty

Abstract

Adverse local tissue reaction (ALTR) from the release of chromium and cobalt ions in metal-on-metal total hip arthroplasty (MoM THA) is a well-reported complication, but there is little evidence suggesting that this inflammatory reaction causes malignancy. We present a 69-year-old female with MoM THA who developed synovial sarcoma (SS). She underwent mass resection and revision THA. Postoperative pathologic analysis revealed the unanticipated diagnosis of SS. She subsequently underwent chemotherapy, sarcoma resection, and endoprosthetic reconstruction. We hypothesize that the SS developed from an ALTR in the setting of failed MoM THA. Given the paucity of data on possible malignant transformation of an ALTR to SS, we advise surgeons to consider potential malignancies when diagnosing ALTR in the setting of failed MoM THA bearings.

Keywords: Metal-on-metal; Pseudotumor; Synovial sarcoma; Total hip arthroplasty.

Figure 1

(a) Anterior-posterior (AP) and (b) frog lateral radiographs of right hip showing metal-on-metal total hip replacement without obvious evidence of peri-implant osteolysis or other acute changes. Soft tissue swelling was noted in the inguinal region.

Figure 2

(a) Coronal, (b) sagittal, and (c) axial MRI images demonstrating a lobular, irregular, large mass anterior to the proximal femoral shaft with high signal intensity on fluid-weighted sequencing.

Figure 3

(a) Anterior-posterior (AP) and (b) frog leg lateral radiographs of the right hip 1-month status postrevision to ceramic-on-polyethylene bearing.

Figure 4

(a) Low-power view and (b) higher-power view of hematoxylin and eosin-stained slides show the tumor is composed of hypercellular spindle cells with monotonous appearance. There is scant cytoplasm. The nuclei are hyperchromatic. The tumor is immunoreactive to vimentin, CD99, BCL2, and TLE1, not shown here. SS18 (SYT) rearrangement is detected by fluorescence in situ hybridization, not shown here.

Figure 5

Gross specimen after resection of the proximal femur, SS tumor, and connecting sinus.

Figure 6

(a) Right hip anterior posterior (AP), (b) right distal femur AP, (c) right hip frog leg lateral, and (d) right distal femur lateral radiographs 5-year status postproximal femur replacement and acetabular reconstruction.

Figure 7

(a) Axial and (b) coronal T2 weighted MRI 5-year status postresection and proximal femoral replacement demonstrating hyperintense soft tissue mass posterior and superior to the right hip in the gluteal musculature as well as hyperintensity of the ipsilateral ischial tuberosity, which was later found to be a biopsy-proven recurrence of synovial sarcoma as well as associated osseous metastasis to the right ischium.