Compressive osseointegration into a custom acetabular implant masquerading as tumor recurrence: a case report.

BACKGROUND: Compressive osseointegration is a durable method of method of achieving fixation in long-bone reconstruction, and radiographic findings are well described. The radiographic appearance of integration into the pelvis is poorly defined in the available literature. CASE DESCRIPTION: We describe a 50-year-old man with a localized chondrosarcoma of the pelvis treated with wide resection and reconstruction using a custom acetabular device that used compressive osseointegration for fixation. A linear area of sclerosis was identified at the patient's 3-month followup surveillance film, which was concerning for tumor recurrence. We used PET-CT to document the absence of worrisome hypermetabolism and to support our suspicion that the abnormalities seen on a surveillance CT scan represented bony integration into the custom acetabular component rather than tumor recurrence. LITERATURE REVIEW: The use of FDG-PET for staging and surveillance of chondrosarcoma is presently evolving. Several articles suggest it may be useful in differentiating low-grade chondrosarcoma from benign lesions. PURPOSES AND CLINICAL RELEVANCE: We found PET-CT useful to differentiate the midterm radiographic appearance of the remodeling produced by compressive implant osseointegration from local recurrence.