**Region:** Upper Extremity # Radial Forearm Flap ## Anatomy - Pedicle: - Main artery: radial artery (mean arterial caliber 1.5–2.0 mm; pedicle length cited up to 20 cm for free flap harvest). (Shokrollahi; Goh/Wong) - Venous outflow: paired venae comitantes (mean venous caliber 1.0–1.5 mm) and optional cephalic vein (cephalic vein caliber ~1.5–2.0 mm; mid‑forearm cephalic diameter ~2.8 mm; concomitant veins ~1.3 mm). Deep venae comitantes are the dominant drainage for free flaps; superficial cephalic system may be included to augment drainage. (Shokrollahi; Clemens; RAP chapter) - Course: radial artery originates from the brachial artery → courses under brachioradialis (BR) for most of its length; in mid‑forearm runs in the lateral intermuscular septum between BR (radial) and flexor carpi radialis (FCR) (ulnar) → becomes subcutaneous near distal forearm and passes deep to abductor pollicis longus / extensor pollicis brevis toward deep palmar arch. Retrograde (reverse) flaps rely on flow from the ulnar artery via the deep palmar arch into the distal radial artery. (Hanasono; Clemens; Shokrollahi) - Perforator pattern: - Septocutaneous perforators predominate; radial artery gives multiple cutaneous perforators roughly every 1–2 cm in the distal forearm. (Clemens; RAP chapter) - Reported counts: 6–10 septocutaneous perforators arising ~2 cm proximal to the radial styloid (reverse‑flap territory). (Hanasono) - An anatomic series found a mean ≈18.5 radial perforators per forearm (radial side ≈10.6 vs ulnar side ≈7.9); distal perforators mean number ≈7.5, proximal ≈11.0. Distal perforator mean diameter at emergence ≈0.6 ± 0.2 mm and mean length ≈9.5 ± 6.8 mm. (RAP chapter) - Inferior cubital artery (largest proximal perforator) mean diameter ≈1.1 mm; surface origin ~4 cm distal to midpoint of inter‑epicondylar line (range reported 2–5 cm). (RAP chapter; Magden) - Choke/angiosomes: robust longitudinal linking network along fascia permits reverse‑flow designs and capture of adjacent perforator vascular territories; distal perforators can capture territory of superficial branch of radial nerve perforator allowing reverse elevation. (RAP chapter; Clemens) - Nerves: - Lateral antebrachial cutaneous nerve (LABC) / lateral cutaneous nerve of forearm runs with cephalic vein; may be harvested for sensate flap (e.g., coaptation to digital nerves); sensate RRFF static two‑point discrimination reported ~11 mm in series where LABC was transferred. (Hanasono; Clemens) - Superficial branch of radial nerve lies dorsally and must be preserved when possible to avoid painful neuroma and dorsal sensory loss. (Clemens; Shokrollahi) - Posterior cutaneous nerves (arm/forearm) relevant for lateral arm variants (for completeness: see lateral arm chapter). (Lateral arm chapter) - Included tissues / flap types: - Fasciocutaneous (skin + subcutis + fascia), adipofascial, fascia‑only, or suprafascial elevations are described. Fasciocutaneous commonly used; adipofascial or fascial with STSG provides thinner coverage for dorsal hand. (Hanasono; Clemens) - Composite options: include palmaris longus tendon (vascularized tendon graft), palmaris longus ± BR for tendon reconstruction, vascularized radius segment for osteocutaneous flap (segments up to 12 cm described). (Hanasono; Clemens) - Limits for bone harvest: described limits vary by source (examples in the literature attached: recommendations range from “≤25% cross‑section” as a conservative limit to other reports citing up to ~40% in osteocutaneous designs); osteocutaneous harvest increases fracture risk — minimize percentage and consider prophylactic plating when large segments removed. (Clemens; Shokrollahi) - Thickness & arc: - Flap is thin and pliable in distal forearm; proximal forearm skin tends to be thicker. Design location (proximal vs mid vs distal forearm) chosen to match desired thickness and arc. Reverse (distally rotated) RRFF pivot at radial styloid; arc of rotation usually limits including very distal forearm in the pedicled reverse flap. (Hanasono; Shokrollahi) - Common variants / anomalies: - Variable origins of inferior cubital artery; perforator number and diameter decrease distally; radial artery dominance must be excluded preoperatively (Allen test/Doppler). Anatomical bifurcations and anomalous branches can change pedicle anatomy—exercise care proximally at antecubital fossa. (RAP chapter; Shokrollahi) ## Dissection Steps 1. Positioning, markings, landmarks. - Position: supine, arm supinated on hand table or arm board; tourniquet applied to upper arm (some prefer without). Palpate radial artery in interval between FCR and BR at wrist; mark course proximally to antecubital fossa with Doppler as required. Mark radial styloid (pivot), wrist crease (distal limit), and inter‑epicondylar midpoint for inferior cubital landmark (~4 cm distal). (Hanasono; Clemens; Shokrollahi) - Size planning: templates from defect; RRFF designs reported up to 35 × 15 cm; flap axis usually centered over radial artery or with radial margin over artery. Test arc of rotation before committing to full proximal extension. (Hanasono) - Donor closure planning: assess pinch; small RFFF donor <2 cm may be closed primarily (Clemens); many authors recommend keeping flap width ≤6 cm if primary closure of donor is desired; donor defects >6 cm generally closed with sheet STSG. (Clemens; Hanasono; Shokrollahi) 2. Plane (suprafascial/subfascial), perforator identification (handheld/IO Doppler). - Decide suprafascial vs subfascial: suprafascial harvest preserves deep fascia for tendon glide and improves skin graft bed for donor site; however, fascia must be included radially over BR and ulnarly over FCR to capture pedicle—flap cannot be raised entirely suprafascially without fascia retrieval at pedicle region. (Hanasono; Shokrollahi) - Use handheld Doppler or color Doppler ultrasound to localize larger perforators (particularly proximal/inferior cubital perforator); distal small perforators are harder to Doppler—consider ICG or intraoperative exploration. (RAP chapter; Clemens) 3. Pedicle dissection: exposure, control, division; transfer/inset; perfusion checks. - Inflate tourniquet after marking (Clemens suggests tourniquet inflated ~50 mm Hg above systolic after exsanguination for free flap dissection); begin with ulnar border incision and elevate in chosen plane toward radial border. Preserve paratenon over tendons. Identify radial artery and venae comitantes in lateral septum between BR and FCR; ligate and divide radial artery proximally for reverse RRFF (ensure palmar arch intact prior via Allen/Doppler—modified Allen test: return of flow within 6 seconds). (Clemens; Hanasono) - When elevating fasciocutaneous paddle, secure dermis to underlying fascia with absorbable sutures to protect perforators from shear. Divide vascular branches to adjacent muscle or periosteum as microclips/bipolar to free pedicle distally. For free RFFF, proceed to microvascular division and transfer with anastomosis to recipient vessels; for pedicled RRFF, tunnel or open track flap to defect ensuring no kinking or compression. (Hanasono; Clemens) - Perfusion checks: after release of tourniquet check color, capillary refill, temperature, turgor; use Doppler/ICG as adjuncts and mark audible perforators for monitoring (6‑0 polypropylene suture at perforator point). (Hanasono; RAP chapter) - If venous congestion encountered, consider augmenting drainage by anastomosing cephalic vein (if included) or decompressing flow surgically. If hand ischemia occurs after radial artery division, reconstruct radial artery (vein graft) to restore hand inflow. (Hanasono) 4. Donor-site closure techniques. - Primary closure: possible when flap width small — sources report primary closure feasible for defects under ~2 cm in some series; many surgeons use ≤6 cm as practical maximum for primary closure by pinch testing. (Clemens; Shokrollahi; Hanasono) - STSG: sheet split‑thickness skin graft for donor defects over ~6 cm width preferred to meshed for improved appearance; pad and bolster graft; immobilize wrist with splint until bolster removal. (Hanasono; Clemens) - For osteocutaneous harvests, consider prophylactic plating and minimize radius cross‑section removed (see anatomy notes above). ## Indications and Contraindications - Indications: - Volar and dorsal hand and wrist soft tissue defects (RRFF pedicled), digital/thumb defects, first‑web contracture release and interposition, pharyngeal/oral/orbital/head & neck resurfacing (free RFFF), thin pliable coverage required, vascularized tendon graft (palmaris longus), osteocutaneous reconstruction (small mandibular or finger bone gaps), sensate reconstruction when LABC/other cutaneous nerve included. (Hanasono; Clemens) - Flap sizes: pedicled RRFF designs reported up to 35 × 15 cm; free RFFF commonly used for small‑to‑moderate head and neck defects (typical clinical sizes smaller). (Hanasono; Clemens) - Need for thin vs bulky: choose distal/midforearm for thin flap; proximal placement if more bulk desired. (Shokrollahi) - Contraindications: - Inadequate ulnar/complete palmar arch perfusion (positive modified Allen required)—if palmar arch not patent, avoid sacrificing radial artery (consider radial artery perforator flap variants or alternative donor). (Hanasono; Clemens) - Prior trauma or surgery to radial forearm that injured perforators—previous cannulation/scarring may preclude reliable flap. (Hanasono) - Diffuse peripheral vascular disease / severe atherosclerosis, vasculitis, uncontrolled diabetes or infection at donor site (relative/absolute depending on severity). (Hanasono) - Patient factors impacting donor cosmetic acceptability (visible forearm donor scar, requirement for primary closure). (Hanasono; Shokrollahi) ## Postoperative Care - Monitoring schedule/method: - Clinical checks every 2 hours in early postoperative period for pedicled RRFF; assess color, turgor, capillary refill, temperature and Doppler signal. (Hanasono) - Adjuncts: handheld Doppler, Doppler ultrasound, implantable probes not specifically discussed in these chapters for pedicled flaps; ICG angiography may be used intraoperatively for perfusion mapping. (RAP chapter; Hanasono) - Warming, antithrombotic practice: - No therapeutic anticoagulation routinely for pedicled flaps; prophylactic low‑molecular‑weight heparin until mobilizing recommended for DVT prophylaxis. (Hanasono) - Positioning/splinting: - Well‑padded forearm splint applied; arm elevated to minimize edema. If flap crosses wrist, resting wrist splint maintained neutral to 20° extension for ~2 weeks; remove for ROM sessions in 2nd week then wean. (Hanasono) - Drains, mobilization, diet/analgesia: - Hemostasis before inset; drains as indicated; early ROM for uninvolved joints; gentle wrist ROM day 5–7 if flap crosses wrist and perfusion intact; discharge commonly around postoperative day 3 with clinic wound check at day 5 (Hanasono/Clemens). Analgesia per standard protocols. - Return‑to‑OR thresholds and time windows: - Urgent take‑back for any signs of arterial inflow loss or venous outflow compromise (absence of Doppler signal, pallor, coolness, increasing congestion) — explore immediately; early identification and re‑exploration yields best salvage. (Hanasono) - Hand ischemia after radial artery division: return to OR for revascularization (vein graft) urgently if required. (Hanasono) ## Complications (rates & management) - Flap loss: - Pedicled RRFF flap loss described as uncommon; free flap specific survival depends on microsurgical factors (no pooled rates given in these chapters). (Hanasono) - Venous congestion / partial epidermolysis: - RAP series reported superficial epidermolysis in ~12% in a series of forearm perforator flaps (suggests venous insufficiency risk in small perforator flaps). (RAP chapter) - Management: urgent re‑exploration to evacuate hematoma, release pedicle kinking/compression, augment venous drainage (anastomose cephalic vein if available), consider medical measures or leeching in selected venous congestion refractory to exploration — primary strategy is surgical revision. (Hanasono; RAP chapter) - Arterial thrombosis / hand ischemia: - Rare but potentially limb‑threatening after radial artery sacrifice without adequate palmar arch; management = urgent revascularization (vein graft to restore radial artery continuity). (Hanasono) - Partial necrosis / fat necrosis / infection: - Standard management: debridement ± revision; antibiotics for infection as indicated. - Donor‑site complications: - Poor scarring, STSG failure, contour deformity, tendon adhesions if paratenon violated; graft‑related morbidity (thigh donor) and aesthetic concerns. STSG donor over forearm may require serial excision for cosmesis. (Hanasono; Clemens) - Osteocutaneous harvest increases risk of donor radius fracture — limit bone harvest (see anatomy limits) and consider prophylactic plating or bone grafting when larger segments are taken. (Clemens; Shokrollahi) - Management algorithms (re‑exploration, leeching, thrombolysis): - Re‑exploration within hours for arterial or venous compromise is first line — check for kinking, compression, hematoma, pedicle twist; salvage measures include revision of anastomosis, thrombectomy, thrombolysis when appropriate in free flaps (microsurgical protocols not detailed in these chapters). - Venous congestion: re‑establish venous outflow (anastomose cephalic vein if available or perform adjunct decompression). (Hanasono; RAP chapter) ## Key Clinical Pearls - Always confirm palmar arch adequacy (modified Allen test with ulnar release flow within 6 seconds or Doppler) before planning radial artery sacrifice; if palmar arch not patent, use a perforator variant or alternate flap. (Hanasono) - The flap pivot for reverse (distally based) RRFF is the radial styloid; design mid/proximal forearm based on required reach and thickness. (Hanasono) - Expect 6–10 septocutaneous perforators clustered ~2 cm proximal to radial styloid; distal perforators are smaller (mean ≈0.6 mm) and shorter (~9.5 mm length), plan technique accordingly (supramicrosurgery or include radial artery segment if needed). (Hanasono; RAP chapter) - Preserve paratenon over tendons and maintain deep fascia over FCR and BR to optimize graft take and tendon gliding—when raising fasciocutaneous flaps secure skin to fascia to prevent shear. (Hanasono; Shokrollahi) - Donor closure planning: perform pinch test; many groups use ≤6 cm as practical maximal width for primary closure, but some free‑flap series note primary closure possible for very narrow (<2 cm) strips—use STSG (sheet graft preferred) for wider defects (>6 cm). (Hanasono; Clemens; Shokrollahi) - For free flap pedicle dissection under tourniquet, consider inflating ~50 mm Hg above systolic after exsanguination for bloodless field; deflate before inset to assess vascularity and achieve hemostasis. (Clemens) - If venous congestion occurs in a reverse flap, consider adding / anastomosing the cephalic vein included in the flap to decompress venous system — this is an effective salvage adjunct. (Hanasono; Clemens) - When planning osteocutaneous harvest, limit radial bone inclusion and preserve periosteal septal attachments; reported segment lengths up to 12 cm exist, but minimize proportion of cross‑section and consider prophylactic fixation. (Clemens; Shokrollahi)