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Grégoire P. Chatain and Michael Finn

Reconstruction of the spinopelvic continuity after sacral resection for primary sacral tumors remains challenging. Complex anatomical and biomechanical factors of this transition zone may be addressed with the advancement of 3D-printed implants. Here, the authors report on a 67-year-old patient with a sacral chordoma who initially underwent total en bloc sacrectomy followed by standard spinopelvic reconstruction. Pseudarthrosis and instrumentation failure of the lumbosacral junction construct subsequently developed. A custom 3D-printed sacral prosthesis was created using high-resolution CT images. Emergency Food and Drug Administration approval was obtained, and the custom device was implanted as a salvage reconstruction surgery. Made of porous titanium mesh, the custom artificial sacrum was placed in the defect based on the anticipated osteotomic planes and was fixed with a screw-rod system along with a fibular bone strut graft. At the 18-month follow-up, the patient was disease free and walking short distances with assistance. CT revealed excellent bony incorporation into the graft.

The use of a custom 3D-printed prosthesis in spinal reconstruction has been rarely reported, and its application in sacral reconstruction and long-term outcome are novel. While the implant was believed to be critical in endowing the region with enough biomechanical stability to promote healing, the procedure was difficult and several key learning points were discovered along the way.

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Grégoire P. Chatain, Nicholas Patronas, James G. Smirniotopoulos, Martin Piazza, Sarah Benzo, Abhik Ray-Chaudhury, Susmeeta Sharma, Maya Lodish, Lynnette Nieman, Constantine A. Stratakis and Prashant Chittiboina

OBJECTIVE

Accurate presurgical localization of microadenomas in Cushing’s disease (CD) leads to improved remission rates and decreased adverse events. Volumetric gradient recalled echo (3D-GRE) MRI detects pituitary microadenomas in CD in up to 50%–80% cases as a focus of hypointensity due to delayed contrast wash-in. The authors have previously reported that postcontrast FLAIR imaging may be useful in detecting otherwise MRI-negative pituitary microadenomas as foci of hyperintensity. This reflects theoretically complementary imaging of microadenomas due to delayed contrast washout. The authors report on the diagnostic accuracy and clinical utility of FLAIR imaging in the detection of microadenomas in patients with CD.

METHODS

The authors prospectively analyzed imaging findings in 23 patients (24 tumors) with biochemically proven CD who underwent transsphenoidal surgery for CD. Preoperatively, the patients underwent pituitary MRI with postcontrast FLAIR and postcontrast 3D-GRE sequences.

RESULTS

Postcontrast FLAIR hyperintensity was detected in macroadenomas, and in 3D-GRE–positive or –negative microadenomas. Overall, 3D-GRE was superior in detecting surgically and histopathologically confirmed, location-concordant microadenomas. Of 24 pituitary adenomas, 18 (75%; sensitivity 82%, positive predictive value 95%) were found on 3D-GRE, and 13 (50% [1 was false positive]; sensitivity 55%, positive predictive value 92%) were correctly identified on FLAIR. The stand-alone specificity of 3D-GRE and FLAIR was similar (50%). These results confirm the superiority of 3D-GRE as a stand-alone imaging modality. The authors then tested the utility of FLAIR as a complementary tool to 3D-GRE imaging. All 5 patients with negative 3D-GRE MRI displayed a distinct focus of FLAIR enhancement. Four of those 5 cases (80%) had location-concordant positive histopathological results and achieved postsurgical biochemical remission. The remaining patient was not cured, because resection did not include the region of FLAIR hyperintensity.

CONCLUSIONS

This study suggests that delayed microadenoma contrast washout may be detected as FLAIR hyperintensity in otherwise MRI-negative CD cases. The authors propose adding postcontrast FLAIR sequences to complement 3D-GRE for surgical planning in patients with CD.

Clinical trial registration no.: NIH protocol 03-N-0164, NCT00060541 (clinicaltrials.gov)