**Region:** Upper Extremity # Ulnar Artery Flap ## Anatomy - Pedicle: ulnar artery (proximal diameter reported 3.0 mm, distal ~2.5 mm); paired venae comitantes (reported caliber 2–4 mm). Dorsal branch of the ulnar artery (DUA) diameter reported 0.9–1.8 mm (1.0–1.3 mm at origin in some series). Pedicle course: ulnar artery arises from brachial artery in antecubital fossa, courses deep to flexor carpi ulnaris (FCU) and between FCU and flexor digitorum superficialis (FDS) in distal forearm; dorsal branch arises 2–5 cm proximal to pisiform and runs deep to FCU to give ascending and descending branches. The ascending branch runs proximally along ulnar border; descending branch joins dorsal carpal arch. Perforator pattern: mean 5.2 (or 7 ± 2 in other series) cutaneous perforators ≥0.5 mm arising to ulnar forearm; clusters in proximal third and distal quarter (examples of mapped distances from pisiform: 7, 11, and ~15–16 cm in multiple sources). One named scheme: A ≈7 cm proximal to pisiform (proximal), B ≈4 cm proximal to A (most consistent; present in ~95%), C ≈5 cm proximal to B. Perforator type: about 69% musculocutaneous (through FCU/FDS) and remainder septocutaneous; distal perforators are more often septocutaneous. Perforators commonly anastomose longitudinally; suprafascial direct anastomoses and subdermal choke vessels present. Pedicle length for island/propeller/free flaps based on perforators reported average 3.3 mm (range 2.5–4.0 mm) in one anatomical report (note units as reported). Flap thickness：約3 mm (thin, pliable). - Nerves: medial antebrachial cutaneous (MABC) nerve runs with basilic vein in proximal forearm and can be harvested for a sensate flap; dorsal sensory branch of ulnar nerve passes beneath FCU 5–8 cm proximal to pisiform (protect or repair if divided). Ulnar nerve lies medial to ulnar artery in distal two-thirds — take care during pedicle dissection to avoid traction or monopolar injury. - Included tissues: fasciocutaneous or adipofascial flap; variations include myocutaneous (partial FCU), osteocutaneous (ulnar cortical bone segment), adipofascial, propeller-perforator and free perforator flaps. Osteocutaneous harvest reported bone length ≈10–15 cm proximal to pisiform (one series reported ~12 cm long × 0.75 cm thick). Arc of rotation: propeller designs can rotate up to 180° around a perforator; pedicled DUA-based designs increase distal reach. Common variants/anomalies: superficial ulnar artery (SUA) variant (incidence ≈0.7–7%) runs more superficially and radially; DUA may be absent rarely (reported 1/100), or arise from anterior interosseous artery in uncommon dissections (2/26 cadavers reported). ## Dissection Steps 1. Positioning, markings, landmarks. - Supine, arm on hand table; tourniquet on upper arm. Choose nondominant arm when feasible. - Mark pisiform, medial epicondyle and FCU; draw axis from medial epicondyle to pisiform (centers most perforators). Mark expected perforator sites with handheld Doppler (examples: ~7, 11, 15–16 cm proximal to pisiform; B perforator often at junction of proximal/middle third). Mark distal limit of harvest ≈5 cm proximal to wrist crease to avoid tendon exposure for long axial flaps. - For free/proximal flaps center design over proximal/mid-forearm perforators; for DUA-based flaps design over dorsoulnar axis. 2. Plane, perforator identification. - Use tourniquet without full limb exsanguination (facilitates venous component visualization). Use handheld Doppler or color Doppler ultrasound to locate perforators preop/intraop; some teams perform sonographer-mapped perforator mapping. - Incise skin and elevate suprafascially initially to identify superficial veins and cutaneous nerves. Continue in subfascial plane toward intermuscular septum between FCU and FDS to find perforators. Preserve multiple perforators during initial dissection; select the dominant perforator (largest audible, best location for reach). - If musculocutaneous perforator encountered, perform intramuscular dissection through FCU or include small cuff of muscle as needed. 3. Pedicle dissection: exposure, control, division; transfer/inset; perfusion checks. - Skeletonize perforator retrograde toward source vessel as needed for length and rotation — dissect carefully where ulnar artery and ulnar nerve are intimate (nerve medial to artery). Avoid excessive traction and monopolar near nerve; use clips rather than cautery on muscular branches when possible. - Before dividing pedicle/sacrificing any main ulnar artery segment, perform intraoperative check of hand perfusion: clamp ulnar artery distal to pedicle and release tourniquet to confirm adequate radial perfusion (modified Allen concept). Allow a period of reperfusion (authors recommend allowing ~10 minutes of perfusion through isolated pedicle after tourniquet release before transfer when fully islanded on a single perforator). - For pedicled flaps: identify pivot point (DUA entering pedicle ≈4 cm proximal to pisiform in some descriptions), tunnel or incise skin bridge for inset, confirm orientation (mark pedicle), inset with minimal tension; when covering palmar defects splint wrist in mild flexion, for dorsal defects splint in extension. - For free flaps: harvest with venae comitantes ± basilic superficial vein if available (basilic can be traced 2–3 cm proximal to flap to permit venous supercharging). If small segment of ulnar artery taken for anastomosis, consider reanastomosis of disrupted ulnar artery in single stage or use end-to-side where appropriate. 4. Donor-site closure techniques. - Primary closure acceptable for narrow flaps; commonly reported thresholds: flap widths ≤6 cm closed primarily in many series (some authors prefer ≤5 cm). Wider defects require split-thickness skin graft (STSG). Suprafascial harvest leaves a graftable bed over muscle bellies (better graft take than over tendons). Bolster graft with foam tie-over and immobilize in short-arm plaster; graft check commonly on postoperative day 5. ## Indications and Contraindications - Indications: - Local pedicled coverage of ulnar wrist and dorsoulnar/palmar hand defects (dorsal and volar), distal forearm and small finger coverage with propeller designs; DUA-based propeller flaps for ulnar hand and dorsal defects. - Free-proximal UAP flap for finger resurfacing, small-to-medium head and neck defects (intraoral lining), lateral tongue, oral cavity; sizes reported from 3.5 × 2 cm up to 24 × 4 cm in case reports/series. Proximal ulnar free flap is an alternative to radial forearm flap when donor characteristics favor ulnar. - Osteocutaneous flap for small metacarpal defects (ulnar cortical bone segment). - Adipofascial UAP flap for coverage under STSG or treatment of neuromas/carpal tunnel. - Size limits: - Reliable single-stage pedicled coverage commonly cited up to ~10 × 5 cm; larger flaps reported (up to 20 × 9 cm) but with higher venous congestion risk; middle/proximal free flaps up to ~10 × 15 cm reported as harvestable. - Sensate flap: - MABC can be included and coapted to recipient sensory nerves for sensate reconstruction. - Contraindications: - Preoperative ulnar-dominant hand circulation (positive Allen test for ulnar dominance) — avoid sacrificing a dominant artery; perforator-only flaps preserve major vessel but if harvesting ulnar artery segment (flow-through or harvest) should be avoided if ulnar dominance present. - Local trauma/fracture of ulna or prior surgery in ulnar forearm that likely injured perforators. - Active infection or unprepared wound bed until debrided. - Severe peripheral vascular disease affecting forearm vasculature, or irradiated, scarred, previously operated donor area that has unreliable perforators (relative contraindication). - Medical comorbidity precluding microsurgery for free flap variants. ## Postoperative Care - Monitoring schedule/method: - Frequent clinical monitoring (color, turgor, capillary refill) in immediate postop period; use handheld Doppler if required. Some centers monitor hourly in first 24 hours, then less frequently as stable. - Keep flap uncovered for observation (dressings with antibiotic-impregnated gauze over incisions; flap left exposed in many protocols). - Consider using superficial vein for supercharging if venous congestion noted intraop or postop. - Warming/positioning: - Keep the hand elevated to reduce edema and pedicle compression. Apply well-padded splint to protect flap and decrease tension. - For palmar coverage splint wrist in mild flexion; for dorsal coverage splint in extension. - Antithrombotic practice: - Standard institutional protocol for microsurgical thrombosis prophylaxis (heparinization/ASA) per local practice; specific regimens not mandated in sources—follow institutional microsurgery protocols. - Drains/mobilization/nutrition/analgesia: - Drains may be placed under flap or donor site at surgeon discretion. Start passive ROM of uninvolved joints intraop to assess tension. Begin guided ROM with hand therapy at ~1 week postoperatively (earlier passive motion for uninvolved joints allowed). Discharge timing reported as postoperative day 3 in one clinical series; first clinic visit at 1 week for dressing change. - Return-to-OR thresholds and time windows: - Immediate dressing removal and urgent return to OR for any signs of compromised arterial inflow or progressive venous congestion, expanding hematoma, pedicle kinking or external compression. Early re-exploration recommended rather than delayed salvage attempts; 10-minute observation of reperfusion intraop after tourniquet release recommended when fully islanded on single perforator. ## Complications (rates & management) - Reported anatomic/frequency data: - Ulnar artery gives off seven ± two perforators to ulnar forearm with diameter ≥0.5 mm (series data). B perforator present in ~95% of individuals in one mapping series. About 69% of ulnar perforators are musculocutaneous. DUA absent in 1/100 forearms in one report; origin variant (anterior interosseous) reported 2/26 cadavers. - Flap-specific complications and management: - Venous congestion — noted risk increases with larger flaps. Management: assess for correctable mechanical causes (hematoma, tight dressing, pedicle kinking) and return to OR urgently for evacuation of hematoma, relieve compression, revise pedicle orientation; intraoperative venous supercharging (anastomose superficial flap vein or basilic to recipient dorsal hand vein) may be used to improve outflow (technique described in sources). When mechanical cause not correctable and venous outflow marginal, medicinal leech therapy or medicinal protocols used in microvascular practice (not specifically detailed in source texts) — if used follow institutional microvascular protocols. - Arterial thrombosis/ischemia — prompt take-back for exploration and thrombectomy/revision of anastomosis; if caused by pedicle kinking, reposition and reassess. Pre-inset perfusion checks (clamping tests, 10-minute reperfusion) reduce risk. - Partial flap necrosis/fat necrosis — occurs more commonly with distal extension beyond angiosome or with large flaps; management includes debridement and local wound care or grafting as needed; consider flap delay or supercharging for borderline cases. - Infection — standard wound management and antibiotics per contamination level; debridement if needed. - Donor-site issues — partial graft loss, contour deformity, hypertrophic/sensitive scars; donor-site primary closure possible for widths ≤~5–6 cm, larger sites require STSG. Skin graft take generally favorable when placed over muscle bellies rather than tendons. Neuroma/sensory deficit when dividing dorsal sensory branch or MABC — primary nerve repair recommended; MABC harvest donor deficit reportedly minimal due to sensory overlap. - Frequencies: - Explicit numeric complication rates (percent flap loss, venous congestion rates) are not consistently reported in the attached chapters; comparative statements indicate lower venous congestion risk for UAP compared with reverse-flow forearm flaps. - Algorithmic management (what/when/how): 1. Any sign of arterial inflow failure or venous congestion → remove dressings immediately, examine flap. 2. If mechanical cause evident (hematoma, tight dressing, kink) → urgent return to OR for evacuation/relief, reposition/skeletonize pedicle as needed. 3. If thrombosis suspected at anastomosis (free flap) → urgent exploration, thrombectomy, revise anastomosis; consider use of additional vein for superdrainage. 4. If persistent venous congestion without correctable cause → consider venous supercharging (anastomose superficial vein/basilic vein to recipient vein) or conversion to venous arterialized flap if available; consider adjuncts per institutional protocol. 5. If minor distal ischemia/partial necrosis develops → conservative debridement and secondary coverage (graft/local flap) or further reconstruction as indicated. ## Key Clinical Pearls - Map perforators preoperatively with Doppler or color Doppler ultrasound; expect reliable perforators around 7, 11 and ~15–16 cm proximal to the pisiform in many patients and center flap over the B perforator (most consistent). - Use a tourniquet without full exsanguination to facilitate visualization of perforators and superficial veins; preserve superficial vein(s) (basilic) when possible as a “lifeboat” for venous supercharging. - Preserve at least a 3–4 cm wide adipofascial pedicle when raising proximally based fasciocutaneous flaps to protect suprafascial plexus; when designing propeller flaps skeletonize the chosen perforator only as needed to avoid kinking. - Before dividing/harvesting any segment of ulnar artery, confirm hand perfusion by clamping the ulnar artery and releasing the tourniquet — do not sacrifice a dominant ulnar supply (perform Allen/clinical vascular testing preop). - Flap widths ≤5–6 cm are generally amenable to primary closure; wider donor sites require STSG — grafts over muscle bellies take better than over tendons. - When using DUA-based propeller flaps, the pivot is typically near the DUA entry ≈2–5 cm proximal to pisiform; ascending branch gives longer pedicle and greater arc of rotation. - If venous outflow appears marginal intraoperatively, harvest and preserve the basilic/superficial vein 2–3 cm proximal to the flap to allow immediate venous supercharging. - If a sensate reconstruction is required, include and trace the MABC for coaptation to recipient sensory nerve (primary nerve repair for any divided dorsal sensory branches is advised to avoid painful neuroma). (Inline hints: anatomy and numeric data summarized from attached chapters on the ulnar artery perforator flap — anatomical mapping, perforator counts and distances, pedicle/vein calibers and donor-site closure thresholds are drawn from the supplied sources.)