**Region:** Lower Extremity # Medial Femoral Condyle and Descending Genicular Artery Flap ## Anatomy - Pedicle: descending genicular artery (DGA) with venae comitantes. DGA typically arises from the superficial femoral artery (SFA) approximately 15 cm proximal to the knee joint. The DGA runs distally 0.5–2 cm before dividing into musculoarticular, osteoarticular, and saphenous branches. The saphenous artery branch (SAB) diameter at origin: 1.5–1.8 mm. Venae comitantes join proximally into the descending genicular vein which runs ~1.5 cm before joining the SFA. (Source: Ch. 47) - Course: after origin the DGA passes deep to the roof of the adductor canal and sartorius muscle, then courses in the fascial plane bounded by sartorius (superficial), adductor tendon (posterior) and vastus medialis (anterolateral). The osteoarticular branch penetrates the periosteum of the medial femoral condyle (MFC) and gives a longitudinal trunk (parallel to femur) and a transverse trunk (toward trochlea) supplying periosteum, cortex and potentially the articular cartilage (medial femoral trochlea). - Perforator pattern: cutaneous perforators originate from either the osteoarticular branch (distal, perfusion area ~70 cm2) or more proximally from the saphenous artery branch (SAB) which can perfuse a larger territory (mean area reported 361 cm2) and may pass anterior or posterior to sartorius. The cutaneous perforator to the MFC region is typically a single discrete perforator capable of sustaining a ~3 × 5 cm skin island in many cases. The DGA may be absent in ~5–10% of specimens; the superior medial geniculate artery (SMGA) can supply the MFC if DGA is absent—SMGA is always present. - Nerves: the chapter does not define a consistent named sensory or motor nerve included with the MFC flap. Cutaneous branches may accompany saphenous arterial branches; if a cutaneous nerve is encountered, it can be preserved to create a sensate skin component, but no dominant sensory nerve is described as reliably included in the MFC osteocutaneous flap. - Included tissues: corticocancellous bone (unicortical or corticoperiosteal), periosteum, optional small cuff of vastus medialis or adductor magnus tendon, and an optional skin paddle (DGAP) based on cutaneous perforators (chimeric configuration). The flap is thin when skin-only but when bone is included it provides a small block of vascularized corticocancellous bone useful for small structural defects and recalcitrant nonunions. Donor-site reparative bone regrowth is minimal radiographically up to 18 months; donor-site fracture and knee dysfunction reported rates are low (0.8% and 0.4%, respectively). (All numeric data from source) ## Dissection Steps 1. Positioning, markings, landmarks - Position: supine with the thigh accessible; palpate/identify sartorius and vastus medialis to plan incision just above sartorius anterior border. Audible Doppler may locate a cutaneous perforator over medial condyle; mark perforator if planning a skin paddle. For bone-only harvest a straight incision parallel to long axis of femur along posteromedial border of femur is acceptable. (See schematic incision line over posteromedial femur.) 2. Plane and perforator identification - Use audible Doppler or imaging (preferred if available) to map perforators. Make anterior exploratory incision; dissect in the loose areolar plane above deep fascia. When a skin paddle is planned, identify the largest caliber perforator (either from osteoarticular branch or SAB) and leave other perforators intact until pedicle explored. - Elevation plane: elevate skin/fascia to expose vastus medialis fascia. For bone harvest reflect interval between vastus medialis and sartorius to expose periosteum over MFC. 3. Pedicle dissection: exposure, control, division; transfer/inset; perfusion checks - Expose DGA pedicle by dissecting along adductor tendon toward its origin from SFA distal to the adductor hiatus. Preserve SMGA until DGA anatomy proven absent/unusable. - Ligate muscle branches to vastus medialis encountered during approach (two muscle branches typically at 12.5 ± 2.0 cm and 9.8 ± 1.9 cm from the joint line) to mobilize pedicle. - If chimeric flap: retain cutaneous perforator branch (osteocutaneous/chimeric configuration) or retain SAB if present. Dissect pedicle to sufficient length; avoid tension or torsion on branches to bone and skin components. - Bone harvest: leave periosteum over the intended bone flap intact except at margins; outline recipient-template on periosteum. Use predrilled K-wire holes at osteotomy margins to avoid stress risers, then use sagittal saw/straight osteotomes to make straight cuts; use curved osteotomes to elevate posterior margin and avoid corticocancellous delamination. Preserve vascular attachments to periosteum and pedicle. - Confirm perfusion after tourniquet release (if used) by observing bleeding or standard microvascular checks; if chimeric, use skin paddle as sentinel. Complete pedicle division only once ready for inset and microanastomosis. 4. Transfer/inset - Inset bone flap with rigid fixation (plate or K-wires) as required. Unicortical MFC flap often requires adjunct fixation and is not usually sufficient for immediate unrestricted weight bearing—plan for fixation. 5. Donor-site closure techniques - Fill donor cortical defect with cancellous allograft when possible to encourage medial column restoration. Close soft tissues in layers. Consider prophylactic packing/grafting to reduce stress riser and fracture risk. Leave drains as indicated. Note minimal bone regrowth expected radiographically; take care to avoid creating a large osteotomy that increases fracture risk. ## Indications and Contraindications - Indications - Vascularized corticoperiosteal or corticocancellous graft for recalcitrant nonunions of small bones (upper and lower extremity), osteomyelitis reconstruction, segmental defects requiring biologic bone transfer. - Composite defects where small vascularized bone and a skin paddle are useful (chimeric DGAP + MFC) — skin paddle can serve as sentinel or provide soft-tissue coverage. - Osteochondral/trochlear reconstructions using transverse branch to harvest medial femoral trochlea when articular surface required. - Typical bone flap sizes demonstrated clinically: bone segments of ~1 × 3 cm or 1–2 cm × 3–4 cm have been used successfully. - Contraindications - Absent DGA (reported in ~5–10%); if DGA absent, SMGA may be used but requires recognition and planning. - Large structural segmental defects requiring bulkier vascularized bone — single MFC unicortical graft may be biomechanically insufficient for unprotected weight bearing without adjunct fixation. - Prior trauma/surgery that has disrupted local vascular anatomy or periosteal blood supply in donor zone. - Relative caution when harvesting large osteotomies due to increased risk of iatrogenic femur fracture and torsional instability. ## Postoperative Care - Monitoring schedule/method - Standard microvascular flap monitoring protocols apply. If chimeric skin paddle used, use as sentinel for buried bone perfusion. Clinical checks (color, capillary refill) and Doppler monitoring for pedicle patency; monitoring most intense in first 24 hours. - Warming/positioning/immobilization - Protect inset and fixation; immobilize recipient site per orthopedic fixation protocol. For lower-extremity nonunion reconstructions, restrict weight bearing until radiographic union; rigid fixation recommended at time of inset. - Antithrombotic practice - Follow institutional microvascular thromboprophylaxis protocols (not specifically detailed in source). - Drains/mobilization/diet/analgesia - Place drains beneath donor and recipient as indicated. Early but protected mobilization per fixation and reconstructive plan. Analgesia per standard post-op pathways. - Return-to-OR thresholds and time windows - Immediate re-exploration is indicated for signs of pedicle compromise (arterial inflow loss or progressive venous congestion). First 24–48 hours are highest-yield window for salvage. ## Complications (rates & management) - Reported anatomical/clinical frequencies from source - DGA absence: ~5–10% of patients. - SAB origin variability: SAB arises from DGA in ~64% of cases, from common SFA origin in ~27%, and independently in ~9%. - Donor-site iatrogenic femur fracture: reported 0.8%. Knee dysfunction: reported 0.4%. - Cutaneous perfusion areas: SAB mean perfusion area ~361 cm2; osteoarticular DGA cutaneous branch ~70 cm2 (anatomic, not complication data). - Specific complications and management - Pedicle thrombosis or venous congestion: management follows standard microvascular protocol — immediate return to OR for exploration, remove kinks/twists, revise anastomosis or convert to alternative vessels; use skin paddle as sentinel; consider thrombectomy/thrombolysis per institutional practice. (Generic microvascular management recommended; source emphasizes standard protocols.) - Donor-site femoral fracture or torsional instability: risk increases with size of osteotomy. Management: acute fixation (plate/wires) if fracture occurs; prophylactically avoid large osteotomies, predrill margins, pack donor defect with cancellous allograft to encourage structural restoration. - Insufficient structural strength of unicortical flap: always use rigid fixation at recipient site when structural load expected. - Minimal radiographic bone regrowth at donor site up to 18 months; consider grafting donor defect to enhance restoration. - Failure of included skin paddle (when chimeric): treat as free flap partial loss — debridement and cover with alternative soft-tissue option; if flap is sentinel for buried bone, loss may prompt urgent evaluation of bone perfusion and revascularization attempt. ## Key Clinical Pearls - Preoperative mapping: palpate sartorius and vastus medialis and use Doppler or duplex imaging to localize a reliable perforator before formal flap design; do not commit to skin paddle design until perforator origin is confirmed. - Pedicle anatomy: expect the DGA origin approximately 15 cm above the knee; the saphenous branch diameter ~1.5–1.8 mm at origin — this provides usable vessel caliber for microanastomosis in many cases. - Muscle branches: anticipate and ligate 2 muscle branches to vastus medialis encountered at roughly 12.5 ± 2.0 cm and 9.8 ± 1.9 cm from the joint line during exposure of pedicle. - Osteotomy technique: preserve periosteum over intended bone flap (do not elevate periosteum directly over intended flap); predrill osteotomy margins with K-wire to reduce stress riser; use curved osteotomes to elevate posterior margin and prevent delamination. - Chimeric option: when possible retain either the osteoarticular cutaneous perforator or the saphenous artery branch to harvest a skin paddle that can act as a sentinel monitor or as additional recipient-site coverage. - Donor protection: pack donor defect with cancellous allograft when feasible to encourage medial column restoration and reduce fracture risk; avoid overly large osteotomies — risk of iatrogenic femur fracture increases with osteotomy size. - Fixation and weight bearing: plan for rigid fixation of MFC bone flap at recipient site; unicortical MFC is often biologically potent but mechanically limited — protect weight bearing until fusion is documented (clinical cases achieved osteosynthesis by 8 weeks and radiographic fusion by 12 weeks). - Always preserve SMGA until DGA anatomy is clearly defined: SMGA can supply MFC if DGA is absent.