JORT Journal

Figure 2: Preoperative CT

Figure 3: Postoperative standing X-ray

Figure 4: Postoperative MRI T2 TIRM (with contrast Dotarem)

The patient was afterwards treated in the Sarcoma Center at Aarhus University Hospital in accordance with the EURO-EWING 99 protocol. She received six cycles of combination chemotherapy (Vincristine, Ifosfamide, Doxorubicin and Etoposide) followed by localized intensity-modulated radiotherapy (IMRT) delivering 45 Gy in 25 fractions to the primary tumor site (Figure 5). The radiotherapy was delivered concomitantly with Ifosfamide. This was followed by further six cycles of combination chemotherapy (Vincristine, Ifosfamide and Actinomycin D). No additional surgery was performed, and the whole oncological treatment was tolerated well and without lasting complications.

Figure 5: Raditation dose color wash histogram. The figure shows the 107%-95% dosecolor wash of the 45 Gy given by IMRT technique to the affected vertebrae. A bolus was used to give full dose to the surgical scar. The artefacts caused by the metal plate and screws could be seen Two years after the diagnosis, the patient started to complain of non-specific pain in the previous surgery area arising while loading the back. X-rays of the spine and the construct showed no changes from previously. MRI and CT confirmed a process at the level of the costovertebral joint on the left side of Th9 level (Figure 6). PET-CT showed positive activity in the area of the process verified by MRI and CT (Figure 7). Patient had no signs of infection. The findings were suspicious for possible relapse of the sarcoma. A CTguided biopsy was performed (Figure 8).

Figure 6: CT with findings of possible tumor relapse atrge level Th9, left side

Figure 7: PET-CT with findings of possible tumor relapse at thr level Th9, left side

Figure 8: CT-guided biopsy of the process suspicious for the tumor relapse

Histological tissue analyses showed non-specific reactive changes without tumor cells, leaving uncertainty as to whether the biopsy was sufficiently representative, and the patient was scheduled for revision surgery. During surgery, we found severe metallosis along cranial fixation points on the left side. Plugs in two pedicle screws were loose, making micromotion possible that generated severe metallosis from the titanium alloy construct. We performed deep dissection towards the verified process. It proved to be a well-delimited solid tumor. It looked like a lymph node with a drainage system from the area with severe metallosis. The tissue analysis revealed non-specific reactive changes and nonnecrotic granulomatosis reaction with pigment deposition. No signs of malignancy. We revised the construct, and the patient’s back pain symptoms were eliminated.

Discussion

The loose nut from the pedicle screw head caused micromovements in the screw-rod connection, leading to fretting corrosion. Metal wear debris accumulated in the tissues adjacent to the implant and in segmental lymph nodes. These metal elements elicited an inflammatory process which resulted in a granulomatous reaction in the draining lymph node. This granulomatous reaction produced a hyperintense signal in MRI and was slightly PET positive, leading to the suspicion of local recurrence of the sarcoma.

Currently, in cases where standard curved rods can accommodate the natural curve of the spine, we use PEEK (Polyetheretherketon) or carbon-based spine implants for tumor patients. ‘Artifact-free’ implants allow and facilitate post-operative CT and MRI controls as well as the use of modern high-dose radiotherapy.

References

1. Davis DL, Morrison JJ (2016) Hip Arthroplasty Pseudotumors: Pathogenesis, Imaging, and Clinical Decision Making. J Clin Imaging Sci 2016.
2. Richman SH, Razzano AJ, Morscher MA, Riley PM S (2017) Metallosis Presenting as a Progressive Neurologic Deficit Four Years After a Posterior Spinal Fusion for Adolescent Idiopathic Scoliosis: A Case Report. Spine 2017.
3. Cook GJ, Wegner EA, Fogelman I (2004) Pitfalls and artifacts in 18FDG PET and PET/CT oncologic imaging. Semin Nucl Med 2004.
4. Rosenbaum SJ, Lind T, Antoch G, Bockisch A (2006) False-positive FDG PET uptake--the role of PET/CT. Eur Radiol 2006.