11.1 Surgical Closure, Skin Grafts, Flaps & Amputation Levels
Key Takeaways
- Primary closure suits clean wounds with tension-free edges, delayed primary closure lets a contaminated wound be closed after about 3 to 5 days once it is clean, and secondary intention is used when infection, wound shape, or patient risk makes closure unwise.
- Split-thickness grafts need a vascularized bed, heal donor sites from retained adnexa, and contract more after placement; full-thickness grafts contract less after placement but need a primarily closed donor site, which makes them useful over joints, hands, and the face.
- Graft take depends on plasmatic imbibition (about the first 48 hours) and inosculation (about 48 to 72 hours); hematoma, seroma, shear, and infection are the main causes of graft loss, so bolsters or NPWT are usually left in place for about 5 to 7 days.
- Exposed cortical bone without periosteum, tendon without paratenon, open joints, and hardware generally need vascularized flaps: soleus for the middle third of the tibia, gastrocnemius for the proximal third and knee, and reverse sural flaps for the distal leg, ankle, and heel.
- Amputation level balances healing and function: transmetatarsal and Lisfranc amputations risk equinus or equinovarus, Chopart amputations need Achilles and tibialis anterior procedures, Syme amputations preserve the heel pad, and transtibial amputation costs far less walking energy than transfemoral amputation.
11.1 Surgical Closure, Skin Grafts, Flaps & Amputation Levels
Core Clinical Principle: Surgical closure turns a prepared wound into a healed one faster than secondary intention, but only when the bed can support it: adequate perfusion, controlled infection and bioburden, removal of necrotic tissue, and a plan for offloading or edema. The reconstructive ladder runs from primary closure through grafts to local, regional, and free flaps, and in the diabetic or ischemic foot it includes choosing the most distal amputation level that will heal and keep the patient walking.
The CWSP content outline lists surgical closure and tissue transfer under patient management. Wound specialists do not have to perform every procedure, but they must recognize when a wound is ready, which option matches the defect, and what makes each option fail.
Methods of Wound Closure
| Closure Method | How It Works | Best Suited For | Main Risks |
|---|---|---|---|
| Primary intention | Edges are approximated in layers at the time of surgery | Clean surgical incisions and clean lacerations with healthy, tension-free edges | Dehiscence under tension, hematoma, surgical site infection |
| Delayed primary closure (tertiary intention) | Wound is left open and cleaned, then closed after about 3 to 5 days when it looks clean | Contaminated wounds, bites, debrided infected wounds, fasciotomy sites | Closing too early over residual infection |
| Secondary intention | Wound heals by granulation, contraction, and epithelialization | Infected or irregular wounds, and patients unfit for surgery | Slow healing, larger scars, contracture |
| Skin graft | Epidermis with partial or full dermis moved to a vascular bed | Large surface defects with a vascularized bed | Graft loss from hematoma, seroma, shear, or infection |
| Flap | Tissue moved with its own blood supply | Exposed bone, tendon, joint, or hardware, and pressure injury reconstruction | Flap necrosis, dehiscence, donor-site morbidity |
Principles of Primary Closure
- Tension: Closure under tension reduces edge perfusion and invites dehiscence; undermining, relaxing incisions, or a flap may be needed.
- Dead space: Close dead space in layers or with drains to prevent seroma and hematoma, which are culture media for infection.
- Host factors: Smoking, poor glycemic control, malnutrition, corticosteroids, obesity, and radiation all raise the risk of surgical site infection and dehiscence.
- Suture removal timing: Roughly 5 days on the face, 7 to 10 days on the scalp and trunk, and 10 to 14 days on the extremities; longer over joints and in patients with poor healing.
The Reconstructive Ladder in Limb Salvage
Once arterial inflow is secure and tissue demarcation is complete, soft tissue reconstruction proceeds up the reconstructive ladder, choosing the simplest modality that ensures durable coverage:
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| THE RECONSTRUCTIVE LADDER |
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| [Rung 6] FREE TISSUE TRANSFER (Microvascular Free Flaps: ALT, Latissimus, Gracilis) |
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| [Rung 5] REGIONAL PEDICLED FLAPS (Reverse Sural Artery, Gastrocnemius, Soleus Flap) |
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| [Rung 4] LOCAL FLAPS (Intrinsic Vascular Pedicle: Advancement V-Y, Rotational, Z-plasty) |
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| [Rung 3] FULL-THICKNESS SKIN GRAFT (FTSG: Epidermis + Complete Dermis; Low Secondary Contracture)|
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| [Rung 2] SPLIT-THICKNESS SKIN GRAFT (STSG: Epidermis + Partial Dermis; Requires Granulating Bed)|
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| [Rung 1] SECONDARY INTENTION (Moist Dressings, NPWT, Cellular/Acellular Biologics) |
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| [Rung 0] PRIMARY CLOSURE (Direct Approximation of Tension-Free Viable Margins) |
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Split-Thickness Skin Grafts (STSG) vs. Full-Thickness Skin Grafts (FTSG)
- Split-Thickness Skin Grafts (commonly about 0.010–0.015 inch): Contain the epidermis and part of the dermis. Harvested with a powered dermatome. Deep dermal adnexal structures (hair follicle outer root sheaths, eccrine sweat ducts) remain in the donor site, allowing donor site re-epithelialization within 10 to 14 days. Meshing (1.5:1 or 2:1) allows drainage of blood/seroma and expands coverage. STSGs undergo minimal primary contracture (contains few dermal elastin fibers) but more secondary contracture (driven by wound bed myofibroblasts), which increases as graft thickness decreases.
- Full-Thickness Skin Grafts: Contains the epidermis and entire dermis. Must be meticulously defatted prior to placement. The donor site cannot re-epithelialize and requires primary suture closure. FTSGs undergo high primary contracture (immediate elastic recoil upon excision) but minimal secondary contracture, making them ideal for flexor creases, digital joints, and facial contours.
Biological Phases of Skin Graft Take
A free skin graft is entirely avascular upon placement. Incorporation occurs in three distinct phases:
- Plasmatic Imbibition (Hours 0 to 48): The graft passively absorbs plasma exudate from the capillary bed via capillary action, gaining up to about 40% in weight in the first day. A temporary fibrin glue layer fixes the graft to the bed.
- Inosculation (Hours 48 to 72): Direct end-to-end alignment and microvascular anastomosis occur between recipient capillary sprouts and pre-existing donor graft vessels ("kissing capillaries"). The graft develops an initial pink blush.
- Revascularization & Maturation (Days 4 to 7+): True ingrowth of host neo-capillaries occurs, lymphatic channels re-establish, and fibroblasts synthesize structural procollagen.
Bolster Dressings & NPWT Bolster Mechanics
Movement between the graft and the bed shears new capillary connections during inosculation and is a leading cause of graft loss, along with hematoma, seroma, and infection. Traditional tie-over bolsters or NPWT bolsters at -75 to -125 mmHg continuous pressure placed over a non-adherent contact layer (silicone or petrolatum mesh) eliminate shear, compress dead space, evacuate sub-graft hematomas through mesh slits, and have been associated with improved graft take in comparative studies.
Local & Muscle Flaps for Avascular Defects
Skin grafts generally fail over bare cortical bone stripped of periosteum, exposed tendon stripped of paratenon, open joint spaces, or metallic orthopedic hardware. These avascular beds cannot provide plasmatic imbibition or capillary buds. Such defects usually need vascularized tissue flaps (or a vascularized bed created first with granulation tissue or a dermal matrix) that carry their own intrinsic blood supply:
- Abductor Hallucis Muscle Flap: Supplied by the medial plantar artery; workhorse for exposed medial malleolar hardware and medial plantar heel defects.
- Soleus Muscle Flap: Supplied by posterior tibial and peroneal perforators; workhorse for middle-third tibial open defects with exposed cortex.
- Gastrocnemius Muscle Flap: Medial or lateral head supplied by sural arteries from the popliteal artery; workhorse for proximal tibial defects, patellar tendon exposure, and exposed total knee arthroplasty hardware.
- Reverse Sural Artery Flap: Distally based fasciocutaneous flap supplied by low peroneal artery perforators (5 cm proximal to lateral malleolus); workhorse for distal third tibial, Achilles tendon, and posterior calcaneal defects.
Amputation Levels in the Diabetic and Ischemic Foot
When the foot cannot be salvaged, level selection balances healing potential (perfusion at the planned level, infection margins, soft tissue coverage) against biomechanics. Partial foot amputations preserve limb length and walking efficiency, but they change tendon balance and pressure distribution, so re-ulceration is common without offloading and footwear.
| Amputation Level | What Is Removed | Biomechanical Consequence | Common Adjunct Procedures |
|---|---|---|---|
| Toe or ray amputation | Digit, or digit with part of its metatarsal | Shifts load to adjacent metatarsal heads; first-ray loss changes push-off | Offloading insoles; watch for transfer ulcers |
| Transmetatarsal (TMA) | All metatarsals through the shafts | Shorter lever arm; tendency toward equinus and varus | Achilles tendon lengthening or gastrocnemius recession |
| Lisfranc (tarsometatarsal) | Forefoot at the tarsometatarsal joints | Equinovarus risk if tibialis anterior and peroneal insertions are lost | Tendon reattachment and Achilles lengthening |
| Chopart (midtarsal) | Foot distal to the talus and calcaneus | Strong equinus from unopposed triceps surae | Achilles tenotomy or lengthening, tibialis anterior transfer, bracing |
| Syme (ankle disarticulation) | Foot at the ankle; heel pad kept and anchored to the tibia | End-bearing stump; heel pad can migrate | Careful heel pad fixation; prosthesis |
| Transtibial (below-knee) | Leg below the knee | Preserves the knee; much lower energy cost than above-knee | Long posterior myocutaneous flap |
| Transfemoral (above-knee) | Leg above the knee | Highest energy cost; many older vascular patients never walk with a prosthesis | Reserved for unsalvageable knee-level disease |
Walking with a prosthesis costs more energy as the level rises: commonly cited estimates are roughly 20% to 40% more energy for a unilateral transtibial amputation and 60% to 100% or more for a transfemoral amputation, with larger increases in patients with vascular disease. Preserving the knee is therefore a major goal of limb salvage.
Clinical Traps
Trap 1: Grafting Over Periosteum-Stripped Cortical Bone
Placing a split-thickness skin graft directly onto white, glistening cortical bone devoid of periosteum almost always fails, because bare cortical bone cannot nourish a graft. Practice Point: Either burr the outer cortical table to expose bleeding cancellous vascular channels, granulate with NPWT, or cover the defect with a vascularized muscle flap (such as a soleus or gastrocnemius flap).
Trap 2: Premature Graft Bolster Removal
Taking down a skin graft bolster at 48 hours post-operatively to "check on the graft" can shear new capillary connections and cause graft loss. Practice Point: Leave tie-over or NPWT bolsters undisturbed for about 5 to 7 days unless signs of infection, hematoma, or pain call for earlier inspection.
Trap 3: Chopart Amputation Without Tendon Balancing
A Chopart amputation removes the insertions of the ankle dorsiflexors and evertors, leaving the Achilles tendon unopposed. Without Achilles lengthening or tenotomy, tibialis anterior transfer, and bracing, the stump drifts into equinus and the distal scar ulcerates.
A 67-year-old woman receives a meshed split-thickness skin graft to a clean, granulating 60 cm² lower-leg wound. On day 5, the bolster is removed and a central 8 cm² area of graft is pale and lifted off the bed by dark clotted fluid, while the surrounding graft is adherent and pink. What is the most likely cause of the focal graft loss?
A 48-year-old male undergoes surgical revascularization followed by extensive debridement of a traumatic wound over the middle third of the anterior tibia. The resulting soft tissue defect measures 6 x 4 cm with exposed cortical bone that has been completely stripped of periosteum. Which reconstructive option is most appropriate for durable soft tissue coverage of this defect?
A 64-year-old man with diabetes and a palpable dorsalis pedis pulse needs a partial foot amputation after extensive forefoot necrosis. The surgeon is choosing between a transmetatarsal amputation and a Chopart (midtarsal) amputation. Which statement about the biomechanical consequences is most accurate?