Peroneus Brevis Muscle Flap for a 20-year-old Neuroischemic Diabetic Ulcer Induced by Traumatic Injury: A Case Report Detailing the Efficacy of Advanced Combined Treatment Modalities for Chronic Wound Closure

The lower leg is the most common site of chronic posttraumatic osteomyelitis.¹ Orthoplastic techniques have been utilized in the lower extremity to cover posttraumatic defects and diabetic foot ulcers, including local cutaneous flaps, fasciocutaneous flaps, muscle flaps, and free flaps.^2-4 Despite the advancement in plastic surgery techniques, many of these methods have provided unsatisfactory cosmetic and functional results when used in the lower extremity. This is largely due to the inherent bulk that is added when a fasciocutaneous or free flap is performed, creating obstacles for the patient regarding ambulation and shoe gear.^1,4 However, muscle flaps have the inherent property of auto thinning as the muscle atrophies.⁵

The application of the distally based PB muscle flap to cover soft tissue defects of the lower extremity was first mentioned by Mathes and Nahai in 1997,⁶ with the first clinical series being introduced by Eren et al in 2001.⁷  The PB muscle flap’s blood supply has been recently reclassified as type IV, meaning it has no dominant vascular pedicles but numerous segmented pedicles instead.^2,6,8,9 The PB muscle receives its blood supply proximally from the anterior tibial artery and distally from the peroneal artery.^2,10 Preserving the PB muscle attachment in the distal 6 cm of the fibula is needed to maintain adequate blood supply, as cadaveric studies have demonstrated the most distal pedicle is approximately 4.3 cm from the tip of the lateral malleolus.^2,6,11 Therefore, it is recommended that the distal perforator must be present and peroneal artery runoff be intact to maintain flap viability.

The purpose of this case report is to demonstrate the use of a distally based PB flap to provide immediate soft tissue defect coverage for a complex, traumatically induced diabetic foot wound to the lateral heel after nearly 20 years of failed local wound care efforts complicated by the presence of calcaneal osteomyelitis and vascular disease.

A 55-year-old male patient first presented to the authors’ wound care center 18 years following ORIF of the right calcaneus with a lateral extensile approach. Post-operatively, there was wound dehiscence with exposed bone, and the patient required multiple courses of IV antibiotics and wound debridement with hardware removal following the initial fixation. The patient now had a hard-to-heal wound to the lateral heel. Medical history was significant for tobacco use, peripheral vascular disease, and diabetes. The wound to the lateral right heel measured 3.5 cm × 2.5 cm, and the calcaneus was exposed (Figure 1). The patient was neuropathic and had weakly palpable pulses.

Noninvasive vascular studies were obtained, and the right leg ABI was 1.11 and toe brachial index TBI was 0.48. Arterial duplex ultrasound demonstrated stenosis of the right superficial femoral artery and proximal popliteal artery. An MRI showed no osteomyelitis of the right calcaneus.

The patient underwent angioplasty with multiple stent revascularization. Following the procedure, 2 vessel runoffs to the right foot (posterior tibial and peroneal) were found. The patient was followed postoperatively by vascular surgery to ensure patency of these revascularized vessels.

A bone biopsy was also obtained and sent for microbiology and pathology workup. Pathologic evaluation confirmed acute and chronic osteomyelitis. Cultures from the biopsy specimen grew Pseudomonas aeruginosa; after consultation with Infectious Disease, the patient was placed on an 8-week course of oral ciprofloxacin.  Following the course of antibiotics, both the anterior and posterior calcaneus had no pathologic abnormality.

The patient then proceeded with the PB muscle flap. A multilevel external fixator, skin substitute, and negative pressure wound therapy were utilized at the time of the flap reconstruction.  Continuous negative pressure at 75 mm Hg was applied; it was removed 7 days postoperatively, after which the patient was discharged from the hospital with a wet-to-dry bolster dressing.

One month later, there was evidence of flap compromise with duskiness to the flap periphery. The patient underwent split-thickness skin grafting and began hyperbaric oxygen therapy, which was continued for 4 months for a total of 30 sessions. An additional split-thickness skin graft was applied 2 months after the first. The external ring fixator was removed after 10 weeks.

The wound was completely healed 9 months following the PB flap surgery, 20 years following the initial ORIF of the calcaneus (Figure 2). The patient remains healed and fully functioning at his baseline 32 months following the reconstruction.

Patient was placed on the operating table in a supine position with a lateral hip bump. The lateral calcaneal wound was excised full thickness, followed by debridement of underlying calcaneal bone with a curette. All nonviable soft tissue and bone was debrided down to healthy bleeding tissue. The wound was then irrigated with sterile normal saline.

Following wound debridement, the perforating vessels of the peroneal artery were identified by Doppler ultrasonography (Figure 3). The distal-most perforator was clearly identified. The preparation for the flap was performed with a tourniquet. Landmarks were drawn and marked, specifically the head and the tip of the fibula, with a longitudinal lateral line connecting the two. A skin incision was then made approximately 1 cm anterior to this line to access the PB at its origin. This incision was extended distally to 3 cm proximal to the tip of the fibula. The superficial peroneal nerve was identified and reflected. The peroneus longus tendon was first identified and carefully retracted to expose the PB muscle belly and tendon (Figure 4). The PB muscle belly was then reflected upwards to separate it from the lateral surface of the fibula (Figure 5). Care was taken to identify and ligate the proximal segmental arteries and not violate the most distal segmental perforating artery. The muscle belly was then rotated distally, starting at 2 cm proximal to where the distal-most Doppler signal had been heard, approximately 5 to 6 cm from the lateral malleolus. The muscle belly was then prepared for transposition to the defect (Figure 6). Complete coverage of the lateral calcaneal wound was achieved. The muscle was secured to the underlying wound surface utilizing 3-0 monofilament synthetic, absorbable sutures.

The incision to the lateral leg was then closed in anatomic layers with absorbable, synthetic braided sutures and skin staples (Figure 7). An acellular dermal matrix skin substitute was applied over the muscle flap and secured with staples, then a nonadherent oil-emulsion dressing was applied and secured with skin staples. Continuous negative pressure was applied at 75 mm Hg followed by a static multi-ring external fixator.

A thorough knowledge of anatomy is necessary when discussing PB muscle flaps. The PB muscle is within the lateral compartment of the leg, deep to the peroneus longus. The PB takes its origin from the distal two-thirds of the lateral surface of the fibula and primarily attaches to the tuberosity at the base of the 5th metatarsal. The length of the PB has been found to vary. Barbera et al found that the length of the muscle belly as seen on MRI (average, 14.44 cm) accurately correlated to the intraoperative measurements in 30 of 32 patients.¹² Primary innervation is from the superficial peroneal nerve, which also courses superficially across the peroneus longus muscle belly.

Most of the PB muscle blood supply arises from the peroneal artery, with some supply proximally from anterior tibial artery perforators. McHenry et al performed anatomic dissection of 10 fresh cadaveric leg specimens.¹³ Dissected specimens had an average of 3.5 vascular pedicles, with most arising from the peroneal artery. Of particular interest, the distal-most pedicle was located an average of 6.7 cm proximal to the tip of the lateral malleolus.¹³ Other anatomic studies have demonstrated that the distal-most pedicle is located 4.3 cm from the tip of the lateral malleolus.^7,9 The location of the distal vascular pedicle limits the reach of the flap, as there should not be tension on the blood supply. While the PB flap is ideal for coverage of lateral ankle and heel wounds, it does not have the reach to cover medially located or more distal wounds.

The operative technique used to create a PB muscle flap is well described in the literature. The technique described by Eren et al has been cited by many authors as their guide.⁷ Troisi et al developed a 5-step technique that follows similar principles for creating a successful PB flap.¹⁴ The authors of the current report also followed this technique. Eren et al advocated for a split-thickness skin graft to cover the muscle flap following its fixation to the soft tissue defect.⁷ Although no graft was applied at the time of the PB muscle flap creation, the patient in the current study did undergo split-thickness skin grafting twice to assist in full closure of the wound.

Many orthoplastic techniques can be utilized to cover lateral heel wounds, such as an abductor digiti minimi flap or a local skin flap.^15-17 The authors of the current report felt that the PB flap was more appropriate given the size of the defect, the presence of known osteomyelitis, and the need to create a robust vascular wound bed for delivery of antibiotics. A digiti minimi flap is best suited for small to medium defects and would have been inadequate to completely fill the defect and provide tissue coverage over underlying bone in this case. There was also some concern about the survivorship of an intrinsic muscle flap due to patient’s history of peripheral vascular disease and diminished blood supply distally, even
after revascularization with diminutive
anterior tibial and posterior tibial artery flow into the foot. There was extensive skin atrophy with scar contracture due to multiple previous surgical procedures in the same area, therefore making a local skin advancement flap inadequate to achieve soft tissue coverage.

External fixation was added in this case to offload any direct pressure on the flap site and eliminate shear forces that would be created by joint motion or pressure and could be detrimental to flap survival.  Offloading is one of the most important factors to flap survival in the postoperative period.^18-21 Motion along a joint, pressure, and shear forces are undesirable and are often responsible for flap failure.²² Immobilization of the joints can also prevent flap contractures, which could affect survivorship and function. Excessive ankle dorsiflexion and plantarflexion transmit shear forces to complex flaps and increase intracompartmental pressures in the limb, which can promote venous congestion and lead to flap failure.²³ External fixation allows for strict immobilization of joints, especially the ankle joint.

The current patient also benefited from the use of negative pressure wound therapy. In a 2016 study of 74 patients reported by Erne et al, half the patients received a 7-day course of negative pressure wound therapy and half did not.²⁴ Continuous negative pressure at 75 mm Hg was applied. The group receiving negative pressure therapy had significantly fewer complications (18.6% vs 80.6%, respectively), including a lower rate of skin graft necrosis and a lower rate of partial flap loss.²⁴

PB flaps have demonstrated promising results. Nguyen et al followed 17 patients for a year and a half; of these, 12% had partial flap tip necrosis, but all flaps survived with local wound care.²⁵ Sahu et al followed 25 patients, none of whom had total flap necrosis, and 20% had marginal tip necrosis.²⁶ Malahias et al reported similarly encouraging findings; of 21 followed patients, all flaps survived in their entirety without any necrosis, and every wound was closed by 9 weeks postoperatively.²⁷

Overall, entire flap necrosis has been reported to affect 0.0% to 8.3% of patients,^4,24-27 and flap survival rate without need for secondary grafting has been reported to be between 72.5% and 100%.^{4,12, 24-27} It should be remembered that patients who are receiving these muscle flaps have hard-to-heal wounds to their lower extremities. Whether acute, traumatic, or chronic, this is a limb salvage effort, which should be taken into consideration when evaluating results of research on the topic.

This study is limited in that it is a case study representing the technique and opinion of a single surgeon. Furthermore, it should be remembered that patients should be treated individually, and many patients with similar chronic neuroischemic wounds may or may not heal with the treatments noted in this review.

The patient featured in the present study had a 20-year-old traumatically induced neuroischemic wound complicated by calcaneal osteomyelitis. The PB muscle flap provided soft tissue coverage, and, through multiple advanced treatment modalities, the wound was successfully healed. Negative pressure wound therapy, static ring external fixation, and split-thickness skin grafting aided in the healing process. In conclusion, the authors recommend the PB muscle flap to physicians dealing with difficult-to-heal wounds complicated by wound dehiscence or osteomyelitis.