Free Flap Donor-Site Complications and Management

Abstract

Free flap harvest will occasionally result in donor-site complications and morbidity. Most of these complications are managed simply without producing lingering effects on activities of daily living. However, some patients will sustain limb weakness, gait issues, chronic pain, and nonhealing wounds. Frank preoperative discussion between surgeon and patient is essential to maximize postoperative outcome and manage expectations. Fastidious surgical technique will help minimize the risks of hematoma, seroma, and infection, while newer techniques can help prevent some issues with wound healing, limb weakness, and sensory changes. In this article, we describe the rates of common and rare complications at free flap donor sites, as well as techniques to prevent and manage them.

Free tissue transfer is now considered standard of care for major defects of the head and neck. Total flap failure occurs in less than 5% of cases. ^{1 2} The advantages of free flap reconstruction include selection of well-matched tissue, three-dimensionality, and reliable vascularity. ² However, despite its name, free flap transfer may come at a cost. Mild postoperative deficits are somewhat common, while, more rarely, patients may experience significant donor-site morbidity. Typical donor-site complications include hematoma, seroma, infection, and dehiscence. Limb-based free flap donor sites may sustain mild loss of strength and/or mobility. In this article, we discuss both common and rare complications associated with free flap transfer and some strategies for prevention and management. Greater awareness and preoperative counseling of donor-site morbidity and complications, with operative technique modifications, can improve overall outcomes and patient experience.

Radial Forearm Donor-Site Complications

The radial forearm free flap is a thin and pliable fasciocutaneous flap based on the radial artery and associated venae comitantes. This highly versatile flap is used for buccal mucosa, oral tongue, and pharyngeal defect repair, among others. The flap is typically harvested from the nondominant forearm.

The most feared, but rare, complication of this flap harvest is radial hand and/or thumb acute ischemia, with risk of amputation. Preoperative evaluation of collateral hand circulation with the Allen test is mandatory prior to proceeding with radial forearm free flap. If there is concern about a complete superficial or deep palmar arch with the Allen test, Doppler ultrasonography may be pursued. ¹ Very rarely, patients can develop hand ischemia despite reassuring preoperative vascular testing. A case report from 1985 from Jones and O'Brien described a patient with a normal Allen test who developed hand ischemia after flap harvest. The radial artery was reconstructed with a vein graft, which restored perfusion to the hand. ³ Similarly, Heller et al described the case of a patient who developed chronic finger ischemia in the months after flap harvest; this case was also successfully treated with vein graft reconstruction of the radial artery. ⁴ These are rare vascular complications, but the flap surgeon should remain vigilant for them.

Wound-healing complications are a far more common complication. Radial forearm defects that are unable to be closed primarily are generally skin grafted. A prospective study from Ho et al ⁵ demonstrated improved take, function, and appearance of split-thickness skin graft, compared with full-thickness and split-thickness grafts with underlying acellular dermal matrix. However, delayed wound healing was described to occur at a high rate. In an early series, 20% of patients had wound healing delayed greater than 6 weeks and a third had exposed tendon. This ultimately results in tethering of the overlying skin to the tendon. Delayed wound healing also prevents return to full activities and requires regular dressing changes. ⁶

More recent studies, employing suprafascial flap harvest techniques, have demonstrated a lower rate of skin graft failure. Liu et al had a partial skin graft loss in 8 of 82 patients (9.8%) and tendon exposure in 5 patients (6.1%). ⁷ Lutz et al reported only 1 partial skin graft loss in 64 patients, and in a series from Emerick and Deschler, 3 of 54 patients had skin graft loss, only 1 of which required operative intervention for tendon coverage. ^{8 9} These authors completed suprafascial flap dissection, which leaves a more vascularized wound bed for better graft take.

Radius fracture can be an uncommon but severe complication. Inclusion of radius bone in the flap without prophylactic plating places the patient at significant risk of pathologic fracture. In an early study, 4 of 13 (31%) patients suffered radius fracture. ¹⁰ Harvest of less than 40% of the diameter of the radius bone and harvest in a boat shaped fashion has been suggested to minimize the risk of fracture. ¹¹ Prophylactic internal fixation and plating is now standard to prevent fracture. ¹² With plating, fracture rates are minimal: Villaret and Futran report 0 cases of forearm fracture in 34 cases (0%) of osteocutaneous radial forearm flap harvests. ¹³

Nerve injury is a significant, and potentially morbid, consideration for this donor site. Branches of the radial nerve are most at risk with this procedure. Radial sensory nerve neuroma formation has been described after this procedure but is uncommon (1%). ^{10 14} Symptomatic radial sensory neuromas produce painful burning and electric-like sensations, which radiate to the dorsum of the radial hand and/or thumb and can be very challenging to treat. More commonly patients will have dorsoradial hand numbness. In a retrospective survey study, 46% of patients reported some degree of hand numbness. ¹⁵ Suprafascial dissection and dissection close to the radial vessels aid in preservation of the superficial radial nerve and the thenar cutaneous branch of the lateral antecubital nerve. Chang et al advocate for exclusion of the cephalic vein due to anatomical variability and quality. ¹⁶ Some patients may also experience loss of wrist and hand function. de Bree et al reported that 24% of patients reported “slightly impaired function.” ¹⁵ A recent study showed that wrist flexion and grip strength were significantly decreased 3 months postoperatively: 45.7 degrees range of motion preoperatively and 40.12 degrees 3 month postoperative; 25.6 kg hand strength preoperatively and 18.6 kg 3 month postoperative. ⁷ Both outcomes improved to preoperative levels by 24 months after surgery. The authors suggest that physiotherapy is an important adjunct in these patients.

Fibula Donor-Site Complications

The fibula free flap is a reliable source for osteocutaneous reconstruction. In head and neck reconstruction, the fibula may be used for mandibular or midface reconstruction. The flap is based off the peroneal artery and associated venae comitantes. Up to 25 cm of bone may be harvested. When first described, the donor-site complications from this free flap were minimized by authors. ¹⁷ However, some patients have significant morbidity associated with this procedure. The overall donor-site complication rate has been reported at over 30%. The most common complications include prolonged wound healing and gait and musculoskeletal issues.

As with the radial forearm flap, wound-healing complications may arise with fibular flap harvest. A skin paddle is commonly harvested with the fibula, which leaves a soft-tissue defect requiring closure or coverage. Small defects may be closed primarily, but larger defects will require split-thickness skin graft coverage. One study reported 8.1% partial and 4.7% total skin graft loss. ¹⁸ Rates of wound dehiscence at this site have been reported at 7 to 8% and an infection rate of 1 to 10%. ^{18 19} As with the radial forearm site, skin graft failure requires regular dressing changes and prevents a patient from returning to full activities. ⁶ Higher donor-site complications in this site have been associated with diabetes, obesity, smokers, and alcoholics. Negative pressure wound therapy significantly decreases wound-healing time for split-thickness skin grafts. This can lead to better graft take and facilitate earlier patient mobilization. ¹

Toe flexor injury with subsequent “clawing” is also a concern. Inclusion of, or injury to, the flexor hallucis longus can result in great toe contractures. The flexor hallucis longus originates from the inferior two-thirds of the posterior surface of the fibula and lower part of the interosseous membrane and inserts on the plantar surface of the distal phalanx of the great toe. This muscle helps to plantarflex the great toe. Fibular free flap harvest can result in great toe stiffness or clawing due to detachment of the flexor hallucis longus muscle and subsequent scarring and contracture. Authors have reported a 9% rate of decreased great toe range of motion and a 6.1% rate of “claw toe.” ^{18 19} Ver Halen suggested that performing perforator dissection can preserve vascularity of the flexor hallucis longus muscle, rather than removing a significant portion of soleus and flexor muscles to maintain skin paddle blood supply. ¹⁸

“Footdrop” is a more severe complication. Rarely, the peroneal nerve may be injured with this free flap. This can result in foot drop and issues with foot dorsiflexion. In one series, 2 of 117 patients (1.7%) suffered peroneal nerve injuries. ²⁰ Ankle dorsiflexion is produced by the anterior tibialis muscle, which is segmentally innervated by the deep peroneal nerve, including high and proximally in the lower leg. Limiting dissection around the common peroneal nerve and its deep peroneal branch high in the leg (i.e., routinely achieved by planning to preserve the fibular head and neck) can limit risks of foot drop.

More commonly, patients may suffer from sensory issues such as paresthesia and dysesthesia related to peroneal nerve injury. ¹ The superficial peroneal nerve runs deep in the lateral compartment of the leg, innervating the peroneus longus and brevis muscles high in the compartment and then becoming more superficial distally in the leg as it approaches the dorsum of the foot to provide sensation. Deep subfascial approaches distally in the leg on the anterior side (where the superficial peroneal nerve lives in the lateral compartment) can jeopardize dorsal foot and toe sensation and risk painful neuroma formation.

Gait issues are an uncommon but important complication of fibula flaps. In a systematic review, Ling and Peng reported that 3.9% of patients have chronic gait abnormality after fibular free flap transfer. ¹⁹ Classically, 5 cm of proximal and 7 cm of distal fibular bone are said to preserve knee and ankle stability. Chronic ankle instability is reported in 4 to 5.8% and decreased ankle mobility is reported in 11.5 to 12% of patients. ^{18 19} Debate exists in the literature regarding timing of weight bearing after surgery. Some authors suggest weight bearing as tolerated as early as postoperative day 1 or 2, while others advocate for non–weight bearing with splinting for extended periods of time postoperatively. Ver Halen reported no association between time to ambulation and complications and promote early postoperative ambulation. Fortunately, rates of significant functional disability following this procedure are low. Ninety-six percent of patients are able to return to preoperative ambulatory activity levels, while one study reported that 39% of patients were able to run or engage in athletic activity before surgery and 37% were able to do so postoperatively. ¹⁸

Anterolateral Thigh Donor-Site Complications

The anterolateral thigh (ALT) free flap is a fasciocutaneous or musculocutaneous flap based off the descending branch of the lateral circumflex femoral artery. This flap can be used for multiple areas in head and neck reconstruction including glossectomy and midface defects. Donor-site morbidity with the ALT free flap is low.

The most common complication associated with the ALT free flap donor site is thigh numbness or paresthesia related to injury to the lateral femoral cutaneous nerve. This nerve provides sensation to a 5 by 13 cm area in the inferolateral surface of the thigh. It is generally sacrificed as it is included in the skin paddle. ²¹ A wider skin paddle will confer greater amounts of numbness. One study reported 87.5% of patients with sensory disturbance. ¹ In a prospective study, 6% of patients had cold intolerance of the thigh after this procedure and 6% had chronic pain. A majority of patients postoperatively showed decreased or minimal sensory conduction velocity of the lateral femoral cutaneous nerve. ²² Patients should be counseled about sensory changes in this area prior to the procedure.

Leg weakness has more recently been described after the ALT. Bai et al reported that the donor leg had a significant decrease in most isokinetic muscle strength values 1 year postoperatively. Interestingly, the contralateral nondonor side showed a compensatory increase. The authors suggested this weakness is due to dissection and removal of the vastus lateralis cuff. ²² Injury to the femoral nerve motor branches within the vastus lateralis can exacerbate this. Other reports suggested that donor-site limb weakness is reversible after 6 months and had no effect on activities of daily living. ^{1 21} Other more rare reports of complications in this donor site include compartment syndrome, arteriovenous hemangiomas, and neuroma formation.

Scapula Donor-Site Complications

The scapula free flap is unique in its soft-tissue mobility relative to the bone. ²³ The flap is based off the circumflex scapular vessels and can be used for reconstruction of a variety of bony and soft-tissue defects. The scapula is vital to shoulder function, and patients should expect some functional deficit postoperatively. A recent study by Patel et al showed a decreased range of motion on the operated side for shoulder abduction, flexion, and external rotation. Strength was reduced for shoulder flexion, shoulder abduction, and external rotation. ²⁴ Clark et al ²⁵ showed similar functional deficits, but these resolved within 6 months of surgery.

The scapular body may fracture following free flap harvest. In a recent retrospective review of 208 patients, Harada et al ²⁶ reported 6 cases of scapular body fracture (3.9% rate). The authors suggested that harvesting the tip is the safest location to prevent body fracture. If fracture does occur, open reduction internal fixation is likely unnecessary and conservative management with a sling and rest can result in bony healing. Authors have also reported seroma formation (3.5%), hematoma (2%), wound dehiscence (3.5%), and infection (3.5%) related to this donor site. ^{22 27 28}

Latissimus Dorsi Donor-Site Complications

The latissimus dorsi free flap is a large muscle flap that may be harvested with a skin paddle and is based off the thoracodorsal artery. The latissimus is commonly used for major scalp and breast reconstruction. Patients may lose shoulder and arm function following surgery, and this donor site has a high rate of seroma and hematoma formation.

The latissimus free flap is associated with musculoskeletal deficits in some patients. The latissimus functions to adduct, internally rotate, and extend the humerus. In a retrospective review, Adams et al described up to 39% of patients reporting at least moderate weakness after free flap harvest. For example, many patients will experience some difficulty with movements requiring reaching overhead such as cleaning windows, high dusting, and taking objects down from cabinets. Other examples of activities that may be affected are vacuuming, lifting groceries, and playing golf and tennis and swimming. ²⁹

The latissimus flap donor site is associated with high rates of seroma formation. Seroma rates of 22 to 79% are reported in the literature. ³⁰ Progressive tension or quilting sutures in the wound have been suggested as a way to obliterate dead space. Fibrin glue has also been reported by some authors to decrease seroma formation. Hematoma formation is a risk at all free flap donor sites, but late hematomas have been described to uniquely develop in the latissimus dorsi donor site. Several authors have described hematoma formation 12 months following the initial surgery. ³¹ Shear stress between the subcutaneous fat and fascia of the donor site has been proposed as a mechanism. ³²

Rectus Abdominis (Vertical Rectus, Transverse Rectus, and/or DIEP Perforator Flap) Donor-Site Complications

The rectus abdominis donor site is commonly used for breast reconstruction and is a reconstructive option for head and neck defects such as glossectomy or scalp. The transverse rectus abdominis muscle (TRAM) and vertical rectus abdominis muscle (VRAM) flaps are based off the deep inferior epigastric artery and can be harvested with a variable amount of rectus muscle, fascia, subcutaneous tissue, and skin.

A main disadvantage of the TRAM and VRAM flaps is the sacrifice of parts of the rectus abdominis muscle. Weakness of the abdominal wall can lead to loss of function, abdominal bulging, asymmetry of the umbilicus, and hernias. ³³ In a large retrospective study, Chang et al reported an overall donor-site complication rate of 14.8% ( n  = 106 of 718). Obese patients had a significantly greater rate of donor-site complications. ³⁴ Donor-site complications include abdominal flap necrosis (1.5%), umbilical necrosis (5.4%), hematoma (0.6%), infection (1.4%), seroma (2.1%), bulge (2.9%), and hernia (2.8%). Perforator flaps (deep inferior epigastric perforator) based on paraumbilical perforators avoid inclusion of rectus muscle in the flap. The deep inferior epigastric perforator (DIEP) flap utilizes perforator dissection to preserve the musculature of the abdominal wall. DIEP flaps result in fewer abdominal wall aesthetic issues and trunk flexion is better preserved compared with TRAM flaps. ³³

Conclusion

It is nearly inevitable that a patient will be left with some sort of free flap donor-site deficit as a trade-off for their primary reconstruction. The potential for donor-site wound-healing complications should be discussed. Patients should be counseled to expect sensory changes and possible limb weakness at the donor site. Similarly, the surgeon should discuss expected cosmetic outcomes and scars at the donor site. Fortunately, in most cases functional and cosmetic deficits at the donor site are minimal and well tolerated. Rarely, severe complications such as compartment syndrome can occur. Surgeons should similarly be vigilant for the omnipresent risk of hematoma and seroma. Donor-site complications are a reality associated with free flaps and necessitate preoperative discussion between patient and surgeon. As mentioned, evidence-based modifications to traditional techniques can help limit donor-site complications and improve overall outcomes.