Multimodal evaluation of donor site morbidity in transgender individuals after phalloplasty with a free radial forearm flap: a case-control study

Summary Background In phalloplasty, there is a lack of standardized follow-up examinations of motor function and strength after harvesting oversized radial forearm free flaps (RFFF). Methods We evaluated the donor site of 20 transmen after phalloplasty, using a multimodal, standardized approach, assessing the following parameters: opposition of the thumb, composite range of motion of the finger joints, grip strength, mobility of the wrist, lesion of the superficial branch of the radial nerve, the dorsal branch of the ulnar nerve, the sensation of pain, and cold intolerance. The contralateral, nonoperated forearm was used as a control. Results No impairment of the mobility of the thumb (Kapandji score median 10, range 5–10) or fingers (all fingers at both sides pulp-to-palm 0 cm, nail-to-table 0 cm) were detected. Grip strength (median 36,3kg, p=0.629) and wrist extension (62.5°vs.70°, p=0.357), flexion (70°vs.70°, p=0.535), pronation (90°vs.90°), supination (90°vs.90°), radial (30°vs.30°, p=0.195), and ulnar deviation (40°vs.50°, p=0.125) did not statistically differ between donor and control hand. Injury of the dorsal branch of the ulnar nerve was uncommon (0% hypoesthesia, 10% positive Tinel's sign). We did not observe any persistent pain of the donor forearm (NRS median 0, range 0–9). We did observe irritation of the superficial branch of the radial nerve (hypoesthesia 40%, neuroma 45%). Conclusion The harvest of an oversized RFFF for phalloplasty does not cause any significant difference in motor function or strength between the donor and nonoperated hand. A potential risk of injuring the radial nerve branch is to be avoided. An aesthetic impairment could be addressed in future studies.