When free flaps are not the first choice : is the distally based peroneus brevis still an option for foot and ankle reconstruction in the era of microsurgery ?

Aim: Soft tissue defects with or without exposed bones in the lower extremity, ankle and the foot-with or without bone defects or exposed hardware-often require coverage with vascularized flaps. Free flaps, which add healthy tissue especially to the lower extremity instead of further injuring a limb, are the first choice in high volume microsurgical centres. Nevertheless, in some instances pedicled flaps may have indications when free flaps are not suitable. Methods: The distally based peroneus brevis flap is harvested from the lateral compartment of the leg based on the distal perforating arterial supply and covered with split skin. Results: We performed a total of 69 peroneus flaps between 2003 and 2017. Minor flap necroses at the distal tip were noted in 8% of the peroneus brevis reconstructions. Total flap loss occurred in 1 peroneus flap. Defect etiology and patient age were not associated with surgical outcome. Conclusion: While nowadays the first choice of lower extremity reconstruction is an appropriate free flap solution, the peroneus brevis muscle flap can also be seen as a valuable tool to reconstruct small to medium sized defects at the ankle, distal tibia, and the heel with an acceptable donor site morbidity. Despite the easily available variety of free flaps to achieve this purpose, still proper indications remain where a local flap can be a viable option in the hand of experienced plastic surgeons. However, caution is advisable in patients with peripheral arterial occlusive disease or venous insufficiency.


INTRODUCTION
Soft tissue defects-with or without bone defects or exposed hardware-in the lower extremity, ankle and the foot often require coverage with vascularized flaps.Due to the anatomically given thin layer of soft tissue to cover vital structures and the oftentimes limited blood supply, the amount of locally available skin is very limited.
Free flaps have become a routine procedure and are a superb option in many cases, especially when large and complex defects need to be addressed.A variety of available options have been described for this problem zone [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] .However, when either the local conditions or other obstacles including systemic diseases, that limit an extended operation time or missing microsurgical expertise are hindrances to closure, local flaps may be a solid option.Proximally based pedicled local flaps have a limited arc of rotation and therefore are no good candidates to reconstruct defects in the lower third of the leg, ankle or foot.We describe the use of a distally based peroneus brevis flap for indications where free flaps were not suitable or not deemed the first priority.
In such cases distally based muscle and fasciocutaneous flaps have constantly remained an interesting alternative to free flap surgery.While the distally based peroneus brevis muscle flap (PBF) was first reported by Donski and Fodgestan [16] , it became more popular when Masquelet described the surgical procedure in detail based on of his anatomical findings [17] and by Lyle and Colborn [18] .In our clinical routine it has been implemented as a workhorse for reconstructing small full thickness defects in the distal lower leg, ankle and heel [19][20][21][22][23][24] .Later papers added their experiences and highlighted the key points that need to be taken into account McHenry et al. [25] and Eren et al. [26] .
Because the anatomy is relatively constant this flap can be quickly and reliably harvested and the donor site poses no relevant clinical or functional problem.This flap has therefore been successfully applied by various authors to reconstruct the distal lower leg, ankle and Achilles region [4,[27][28][29] .We discuss the peroneus brevis flap as a part of the surgical armamentarium and hence its specific technical aspects in this paper.

METHODS
According to the description of Nahai and Mathes [30] who had first reported the peroneus brevis flap as a proximally based tool in 1974 later on described a distally based version in 1997, we performed the distally based turnover muscle flap.Modifications and standardization of this flap [18] were popularized by Eren et al. [26] and further propagated by others as a useful muscle flap to reconstruct small defects in the lateral distal third of the leg [4,[31][32][33][34] .
In our series the peroneus brevis flap was raised as a reversed muscle flap and, following transfer into the defect, covered with a split thickness skin graft.Donor sites were closed directly in all flaps [35] .Similar to patients with sural flaps, wounds were preconditioned using topical negative pressure with or without instillation until the wound was deemed clean enough for closure.Dissection of the flap was performed under general anaesthesia with the patient supine on the operative table and a tourniquet was applied.The incision was performed straight or slightly curved depending on the localization of the defect.Preserving the distal perforating vessel, which is approximately 5 cm above the malleolus has allowed the flap to become adopted as a standard technique of limb reconstruction in our unit with 1 case of total PBF flap loss so far, requiring secondary surgery.
Skin flaps were raised with the deep fascia, and care was taken to protect the superficial branch of the peroneal nerve, which can be dissected deep to the deep fascia in the proximal calf.It pierces the deep fascia approximately 15 cm proximal to the lateral malleolus.The peroneus longus tendon is found more posterior and superficial than its brevis counterpart.The tendons were followed up to the attachments of the muscle bellies and brevis and longus tendon were identified and separated, revealing the lateral surface of the fibula between them.Any branches of the peroneal vessels that run posterior to the fibula and segmentally pierce the muscle should be protected.In our series we found usually one larger proximal vessel and another smaller one more distally.The peroneus muscle was then detached from the anterior intermuscular septum to the anterior surface of the fibula.The muscle was elevated en bloc starting from the periosteum proximally down to the pivot point, where the dissection stopped.Two thirds of the flap can usually be elevated until the perforating vascular branch enters the muscle belly.After opening the tourniquet and hemostasis the flap was turned over and was sutured into place with a drainage underneath and split skin grafts on top.If necessary near infrared fluorescent angiography with indocyanine green was performed intraoperatively to determine flap perfusion and to eventually trim the tip of the flap.Eventually the most distal tip of the peroneus flap is prone to undergo venous congestion and may necessitate secondary skin regrafting, which usually leads to complete healing [Figures 1-5].
In a previous historic comparison of reverse flow lower extremity flaps Kneser et al. [36] analyzed the morbidity of the donor site and stated that equally to a reversed sural island flap (which was used historically and is no longer a routine surgical option in our hands since free flaps have become the method of choice) the peroneus brevis flap showed appropriate to successfully close full thickness defects in the lower extremity.

RESULTS
We performed a total of 69 peroneus flaps between 2003 and 2017.Minor flap necroses at the distal tip were noted in 8% of the peroneus brevis reconstructions.Total flap loss occurred in 1 peroneus flap.Defect etiology and patient age was not associated with surgical outcome.In a physical examination at time points with a minimum of at least 12 months after flap surgery all wounds were completely healed without any evidence of instable scars, chronic infections or fistulae.Patients reported a high level of satisfaction regarding the outcome of surgery without any significant statistical difference between the compared flaps.The active total range of motion was comparable in both groups without significant differences [extension/flexion 78.5% ± 20.0% (PBF peroneus flap), 66.6% ± 23.1% (DSF distal sural flap) and pronation/supination 70.9% ± 27.7% (PBF), 61.1% ± 33.3% (DSF)].No instability of the ankle joint was observed in patients from both groups.Circumference of the lower leg 15 cm below the knee joint and above the ankle joint was comparable in both groups.No significant postoperative lymphedema was observed.Hypaesthesia in the lower leg or foot region, except for the flap itself and the skin-grafted regions at the donor site, was reported by 21% of patients from the PBF and 58% of patients from the DSF group [36] .Patients did not report significant functional impairment due to these hypoaesthetic zones.Neuromas were neither observed at the donor nor at the recipient sites in this series [36] .

DISCUSSION
Soft tissue defects in the distal lower leg as well as in the foot and ankle region are not infrequent and remain challenging for plastic surgery.Methods of tissue engineering and regenerative medicine [37][38][39][40][41][42][43][44][45][46][47][48][49][50][51] to circumvent the use of autologous tissue and their inherent donor site morbidity seem promising but are not clinically available for these problems yet.Although a considerable number of local or free flaps has been successfully described to surgically reconstruct these defects [7,[52][53][54][55][56][57][58] each individual case needs the optimal indication for the most suitable flap procedure.Free flap transfer has become a routine method in high volume centers and allow free tissue transfer even to the distal lower extremity with a successful closure in more than 90%-95%, depending on the comorbidities and local and systemic conditions.This does not preclude the remaining interest in local flaps to solve the problem of small to medium-sized defects in this critical anatomical region [59,60] .
Especially the advent of perforator based flaps, such as propeller flaps, have augmented the armamentarium of problem solving techniques in the lower extremity [52] .Other than in the proximal knee region and the upper and middle third of the lower leg, where a variety of proximally based local pedicled flaps are available, the lower third and foot and ankle region demand either free flaps or reversed pedicled flaps [11,61,62] .Various modifications of the sural and peroneusbrevis flaps have been described to optimize the outcome and minimize complications [63][64][65][66][67] .The distally based peroneus brevis flap has been described as an efficient tool for the reconstruction of the distal lower leg, ankle, Achilles tendon and proximal foot region [4,65,[68][69][70][71][72][73] .This flap can be indicated to cover exposed vessels, bones, tendons, and internal fixation hardware.The surgical procedure is comparatively straight forward and basically safe, when anatomical landmarks and precautions are taken into account.Although we no longer use the distally based sural fasciocutaneous flap our group has compared the efficacy and donor site morbidity following use PBF (when compared to a sural flap) which had not been studied earlier [32] .Using the foot and ankle outcome score (FAOS) a direct comparison between the sural flap and the peroneus flap group did not show significant differences in any of the FOAS subscales [36] .Interestingly, the general quality of life (QOL) in patients with distally based flaps was more reduced in both groups than the actual function in daily living (ADL).In an attempt to exclude the influence of initial defect-related problems on ankle stability and function, subgroups of patients with defects caused by open fractures, osteomyelitis or Achilles tendon-related defects were compared with defects secondary to tumor resection or ulcers [36] .The results from the patient-administered FOAS questionnaire were confirmed by the physical examination which did not identify any significant differences in terms of ankle joint stability or range of motion [36] .Ulrasonic investigation may further enhance the safety of the procedure.As with other meta-analyses it is a commonly known problem in studying outcomes in reconstructive surgery, that most series comprise only small numbers of patients and lack randomized trials, which is a classical scenario in plastic surgery.This holds especially true for studies comparing different types of flaps, where personal experience and preferences as well as local conditions significantly influence decision-making and prevent randomization [9,36] .The use of near infrared laser angiography with indocyanine green intraoperatively might help further optimize the design and flap survival, as has been shown previously in other flaps [14,74] .
In conclusion, distally based peroneus brevis flaps remain valuable options for the reconstruction of full thickness defects in the distal lower leg when the routine use of free flaps is not indicated.Vascular integrity of the affected leg is a prerequisite, and if local perfusion is compromised by peripheral vascular disease, failure rates are higher.In such cases we strongly advocate the use of free flaps with vascular reconstructions and optimization of blood flow.Studies have shown that harvesting of PBF does not affect stability and ROM of the ankle joint.Whenever free flaps are not the first choice in distal lower leg reconstructions we therefore would recommend the peroneus brevis muscle flap as an alternative procedure to close small to medium sized defects at the distal tibia, fibula, ankle and heel.

Figure 5 .
Figure 5. Lateral aspect of the lower leg and foot 6 months after reconstruction with the distally based peroneus brevis muscle flap and split-thickness skin graft.The distal part of the flap needed secondary skin regrafting and hence healed uneventfully