Long-term posttransplant-related bone volumetric changes in eight face transplant recipients - A single-center retrospective case series.

Abstract

The long-term stability of allograft or native bone in facial vascularized composite allograft (fVCA) recipients is unclear. This study quantified long-term bone volume changes in facial transplants. Computed tomography scans of eight fVCA recipients (2011-2023) were analyzed with Materialise Mimics. Native bone (soft tissue-only VCAs, n=4) and allotransplanted bone (n=4) were compared. Median bone volumes were assessed for significance using the WilcoxonRanked-Sum Test. Mean follow-up was 10 years (range 5-13). A significant median decrease in both mandibular (-6520 mm³; p=0.0078) and maxillary (-3548 mm³; p=0.0078) bone volumes was seen in all patients, irrespective of bone origin. Median bone volume loss was -9.92% in the bony allograft cohort and -22.60% in the soft tissue-only cohort, respectively. The histopathological analysis of the limited samples (n=2) showed physiological bone even after ten years. Patients with allotransplanted bone showed less pronounced volume loss compared to those with native bone receiving soft tissue-only allografts. This finding suggests that allotransplanted vascularized bone in fVCAs may not be a primary target of chronic rejection processes that compromise bone volume stability and functionality. Bone volume changes are likely influenced by multiple factors, such as tooth loss, nutrition, chronic immunosuppression (e.g., steroids), mechanical stress/load, varying bone remodeling rates, and other medical comorbidities. Further research is needed to clarify the factors affecting bone volume and remodeling after fVCA.