The Use of Custom 3D Anatomical Spacers in Maxillofacial Resection and Reconstruction of the Temporomandiublar Joint

Introduction: With the rise of three dimensional treatment planning, the fabrication of custom 3D joint prosthesis in infectious and pathologic surgical modalities has become widespread.   Refinements in these techniques have led to more exact fitting prostheses and improved function and durability of the reconstruction.  In infectious and failed reconstructions with retained hardware, staged surgeries can often be necessitated for clearance of infectious etiology and for ideal fabrication of the final prosthesis.  For these staged surgeries collapse of the soft tissue envelope can greatly add to secondary surgery complexity and complication rate. Through the fabrication of custom 3D anatomical spacers a soft tissue envelope can be preserved with or without antiobiotic impregnation, improving both clearance of infectious etiology and reduction of complexity in the definitive surgical reconstruction.  

Methods: Two cases over a two year period, treated with custom fabricated 3D anatomical spacers for soft tissue envelope preservation in Mandibular/Temporomandibular resection and reconstruction at Walter Reed National Military Medical Center Bethesda, were reviewed.  Definitive reconstructions were completed with TMJ Concepts® prostheses. One case was secondary to severe osteomylitis following wisdom tooth removal and the second was a failed reconstruction following segmental resection of Central Giant Cell Granuloma.  The 3D Medical Applications Center at Walter Reed National Military Medical Center was tasked with fabricating the 3D anatomical negatives which were used intraoperatively to fabricate custom spacers using polymethylmethacrylate (PMMA) with impregnated Tobramycin. Spacers were fabricated intaoperatively and placed following the initial resection and removal of the failed reconstruction respectively. Following adequate healing, a new Computed Tomography scan was completed and used for fabrication of the definitive TMJ Concepts prosthesis. The spacers were subsequently removed during definitive reconstruction.

Results:  A total of two cases were performed during this review, with both having adequate maintenance of the soft tissue envelope for definitive reconstruction.  Staged surgeries allowed for a more exact fabrication of the definitive restoration with the TMJ Concepts® prostheses being fabricated after the resection and hardware removal respectively.  Overall surgical time was decreased when compared to previous reconstructions without an anatomical spacer. In both cases the spacers were successful, including the pathologic reconstruction in which the contralateral Mandibular/TMD complex was used to fabricate a negative for the affected side. Complications included dehiscence of the intraoral mucosa with subsequent reduction of the spacer under local and heterotopic bone formation along the spacer.  There were no other complications encountered.

Conclusion:  Reconstruction of the temporomandibular complex can be a difficult procedure in the presentation of infectious and pathologic etiologies due to the complex treatment planning required.  By staging the primary resection and the reconstruction, sources of error in the definitive reconstruction can be reduced by more exact fabrication of the final prosthesis. Fabrication of a 3D anatomical spacer can improve these outcomes further by maintenance of the soft tissue envelope following initial resection as well as local antibiotic delivery for infectious etiologies.

References:

Goode RL RB. Tobramycin-impregnated methylmethacrylate for mandible reconstruction. Arch Otolaryngol Head Neck Surg. 1992 Feb;118(2):201-4. 1992.

Taft RM, Kondor S, Grant GT. Accuracy of rapid prototype models for head and neck reconstruction. J Prosthet Dent. 2011 Dec;106(6):399-408.