Reply to Letter to the Editor: Fibroxanthoma: A Complication of a Biodegradable Screw

Abstract

Reply: I thank Dr. Bauer and appreciate his interest in our case report, “Fibroxanthoma: A Complication of a Biodegradable Screw”, published in a recent issue of the journal [7]. Most of his concerns were raised by the referees during the editorial process. I disagree with his statement that the term, fibroxanthoma, is misleading. Various synonyms have been used in the literature for fibroxanthoma such as fibrous histiocytoma [3], xanthofibroma [1, 2], nonossifying fibroma, fibrous cortical defect [8], and benign fibrous histiocytoma [6]. Use of these various terms stem from authors’ disagreements regarding the histiogenesis. Although considered by some as nonneoplastic, others believe it is a neoplastic process, and yet others think of it as a reactive process [1–3]. Second, Dr. Bauer states that we described a soft tissue swelling at the site of the tibial tunnel but that is not what we described. Rather, we observed and described a slowly progressive, painful, bony swelling (1 × 1.5 cm) at the site of the tibial tunnel. Our initial clinical impression was an ectopic bone formation, delayed allergic reaction to a screw, or disengagement and backing out of a screw. Surgery was performed with the intent to curettage the new bone and/or debride the backed-out screw. At surgery, the macroscopic appearance was that of obliteration of the tibial entry portal, and irregular thickening of the cortex around it gave the impression of a periosteal reaction to the screw. Excision and thorough curettage of the abnormal bone and debridement of the tibial tunnel with a rongeur were done. I agree with Dr. Bauer that correct diagnosis requires a correlation between clinical and histologic findings. A biopsy report of a progressively painful bony mass localized at the entry site and obliterating the tibial tunnel initially was surprising. However, the histopathologic finding of large areas of foam cells interspersed with fibrovascular septations, which were negative for S-100 and positive for anti-human macrophage marker HAM-56, was consistent with the diagnosis of a fibroxanthoma [4, 5]. Finally, I thank Dr. Bauer for providing details regarding the mechanism of degradable orthopaedic devices.