Sensory Abnormalities and Pain in the Donor Sites of Radial Forearm and Fibula Free Flaps—A Systematic Review

Background and Objectives: Free flap reconstruction is the gold standard for complex head and neck defects following oncological ablation. While surgical techniques have improved flap success rates, donor site sensory morbidity remains relatively understudied. The radial forearm free flap (RFFF) and fibula free flap (FFF) are the two most commonly used free flaps for head and neck reconstruction and sensory abnormalities at their donor sites represent a significant but underrecognized source of postoperative morbidity. Materials and Methods: The aim of this study is to systematically review and synthesize the existing evidence on the prevalence, characteristics and assessment methods of sensory abnormalities and pain at the donor sites of RFFF and FFF harvests. A systematic review was conducted according to PRISMA 2020 guidance. PubMed/MEDLINE, Scopus, Web of Science, the Cochrane Library, and Google Scholar were searched from inception to 1 October 2025, with additional gray-literature and reference-list screening. Primary studies reporting sensory abnormalities, donor-site pain, neuropathic pain, or cold intolerance after RFFF and/or FFF harvest were included; prior reviews were used for citation tracking and contextual comparison only. Risk of bias was assessed with study-design-specific Joanna Briggs Institute (JBI) checklists, and the level of evidence was classified using the Oxford Centre for Evidence-Based Medicine (OCEBM) framework. Descriptive prevalence summaries and exploratory random-effects pooled estimates were calculated when numerators and denominators could be extracted. Results: From 1247 initially identified records, 73 studies met the inclusion criteria (36 RFFF-specific, 35 FFF-specific, and 2 addressing both flap types). Most studies were observational, and sensory outcomes were frequently secondary endpoints. For RFFF, reported sensory abnormalities ranged from 0% to 100% across extractable studies (median 31.3%; IQR 13.1–55.0%), reflecting differences in definitions, follow-up, and testing; the exploratory pooled prevalence was 34.4% (95% CI 23.6–47.1%; I2 = 88.4%). General donor-site pain ranged from 0% to 36.8% (median 12.0%; pooled 16.0%, 95% CI 9.9–24.8%), whereas Douleur Neuropathique en 4 Questions (DN4)-defined neuropathic pain was 18% in the largest dedicated RFFF study and 18% in a smaller pain-focused study. Cold intolerance ranged from 0% to 40.0% (median 16.2%). For FFF, sensory abnormalities ranged from 0% to 76.3% (median 21.4%; IQR 8.2–46.8%; pooled 24.0%, 95% CI 16.5–33.6%; I2 = 88.6%). General pain ranged from 0% to 72.7% (median 17.5%; pooled 18.8%, 95% CI 13.9–24.9%), and DN4-defined neuropathic pain was 21% in the only dedicated FFF study. Objective testing (quantitative sensory testing [QST], Semmes-Weinstein monofilaments, two-point discrimination, or standardized neurological examination) was used inconsistently, and no included study systematically used nerve conduction studies or electromyography (EMG). Conclusions: Sensory abnormalities and pain after RFFF and FFF harvest appear common, but available estimates remain uncertain because of heterogeneous definitions, follow-up intervals, assessment instruments, and predominantly Level 2b-4 evidence. The literature shows a persistent gap between patient-reported symptoms and objective sensory testing. Future prospective studies would benefit from standardized neuropathic pain screening, structured neurological examination, and QST; however, current data do not support strong causal inferences or a validated treatment algorithm.