Reconstruction of traumatic and non-traumatic lower extremity defects with local or free flaps

Reconstruction of the distal lower extremity remains challenging despite continuous advances in surgical techniques. Limb preservation, early ambulation, and optimized functional outcomes are therapeutic goals that often require a multistep surgical approach in patients presenting with complex lower extremity defects with exposed vital structures or bones [1]. The mechanisms leading to extensive lower extremity wounds are diverse, including trauma, oncological resection, peripheral arterial disease, diabetes, and chronic venous stasis [2]. The size and anatomical location, as well as the comorbidities and acute state of the patient, are considered in the selection of reconstructive concept [2]. Large, complex defects in the distal third of the leg with exposed skeletal structures, tendons, nerves, and vessels often require microsurgical free flap reconstruction. Local and regional flaps are used for the reconstruction of small to moderately size defects. Local flaps provide similar tissue characteristics, thickness, and weight-bearing capacity to the reconstructed areas [3]. Microsurgical free flap reconstruction is widely established in traumatic and non-traumatic lower extremity defects and was proven to be safe in patients of advanced age, although the patients suitability to undergo extended surgeries needs to be explored [4‐6]. The timing of reconstructive surgery is influenced by multiple factors including the patients’ general state and the contamination of the wound; however, in traumatic defects, early free tissue transfer was associated with less complications than delayed reconstruction [7]. Postoperative complications and long-term limb salvage need to be considered when evaluating complex lower extremity reconstructions [2]. Lower extremity preservation leads to improved survival rates in multimorbid patients suffering from non-traumatic defects [8]. If the patient is stable enough for reconstruction, limb salvage and functional restoration should be the treatment goal [1]. The challenges of foot and distal lower extremity reconstruction are not only coverage of soft tissue and bone defects, but also the restoration of motor function and sensation, as well as achievement of acceptable aesthetic results in terms of contour and tissue texture [9]. Flap selection is driven by the extent of tissue damage, the anatomical subunit that requires reconstruction, the vascularity of the leg, and comorbidities of the patient [10]. Local flap reconstructions, if available and suitable for the defect size, have been associated with less reoperations and shorter hospitalization times compared to free flap reconstruction [11].

The aim of this retrospective study was to assess distal lower extremity reconstruction with local flaps and microsurgical free tissue transfer. Postoperative complications and limb preservation rates were analyzed and compared by reconstructive concept.

The local ethics committee granted approval of this retrospective analysis (ethics approval number 1726/2019). All data assessed for the current study were obtained from the patients’ charts and operative reports.

Patients included in this study were subdivided by treatment concepts. The first group included patients treated with local tissue transfer and the second group patients with microsurgical free flap reconstructions.

In this retrospective study, lower extremity reconstruction with local flaps and free tissue transfer was assessed. Patients with complex lower extremity defects due to traumatic and non-traumatic etiologies were included in this analysis. Overall, the most common etiology was lower extremity trauma in approximately one third of patients. Peripheral vascular disease and diabetes were the following most common causes of distal lower extremity defects. These patient characteristics are representative of the spectrum of comorbidities described for complex lower extremity reconstructions in previous studies [1, 5, 12].

Flap selection is driven by a multitude of factors. The defect size, anatomical location, and exposed vital structures are crucial in determining the reconstructive concept and flap design. In this study, distal lower extremity defects were included, as proximal defects in the thigh region are often closed primarily or with locoregional reconstruction due to the abundance of soft tissue [2]. The focus on the distal lower extremity has been implemented in comparable studies in the literature [1, 2].

The most common defect locations included in this study were the plantar surface of the foot, the lateral malleolus, and the proximal tibia. The specific tissue properties of the reconstructed location are to be considered, as the anatomical subunits of the distal lower extremity vary greatly in terms of weight-bearing function, skin thickness, and soft tissue contour. Subunit reconstruction for defects in the foot and ankle region was described to achieve both optimal functional and aesthetic results [13]. The reconstruction algorithm to cover complex defects involving the calf and tibia included the division into proximal, middle, and distal thirds [1]. Depending on the size of the defect, the proximal third and knee region can be covered with a gastrocnemius muscle flap with split-thickness skin grafts [14]. Pedicled soleus and gastrocnemius muscle flaps are also reconstructive options for the middle third of the calf [1]. Traditionally, free tissue transfer was most commonly indicated for complex defects of the distal third of the lower extremity [1, 15]. However, improvements in microsurgical techniques, risk assessment, and perioperative patient management have increased the variety of defects reconstructed with free flaps in recent years [2]. The detailed understanding of flap perfusion, perforators, and the subsequent design of perforator flaps further improved the reconstructive repertoire, as fasciocutaneous perforator flaps may be used as local flaps to reconstruct “like with like” tissue or as free flaps, while minimizing donor site morbidity [10, 16‐19].

Free flap reconstruction enables the coverage of larger wounds and avoids additional local donor site trauma in the distal lower extremity [20]. Free tissue transfer is an integral part of the reconstructive ladder, with improved microsurgical techniques and perioperative patient management rendering it a safe and effective option for lower extremity reconstruction [15]. The most common free flaps used in this study were latissimus dorsi and gracilis muscle flaps, both workhorses in microsurgical practice [15, 20, 21]. Free tissue transfer has proven effective in both traumatic and non-traumatic cases of lower extremity reconstruction [1, 7, 22]. Patient factors, timing of the reconstruction, and the vascularity of the leg, as well as defect characteristics, determine flap selection. In traumatic cases, longer vascular pedicles are often required to place the microvascular anastomoses outside of the zone of injury [1]. Reconstruction with well-vascularized free tissue transfer for lower extremity reconstruction after oncological resection proved safe and effective in patients undergoing postoperative radiation therapy [6, 23]. Free flap reconstruction has led to advances in limb-sparing resection of tumors of the lower extremities [24]. Flap design and tissue composition are variable due to the defect size and specific requirements of the reconstructed region. Free tissue transfer was even proven to be effective in plantar reconstruction, providing stable weight-bearing soft tissue coverage [25].

Extremity preservation may be achieved with both local and free flap reconstruction [11]. However, distal lower extremity reconstruction remains challenging as it is associated with a relatively high percentage of postoperative complications [12, 26]. Patients presenting with lower extremity defects often suffer from multiple comorbidities, which impact postoperative healing [26‐28]. Careful selection of the reconstructive concept to accommodate the patients’ functional goals and consider possible risk factors is therefore necessary.

Limitations of the current study are the low case numbers and the retrospective study design. Future prospective investigations should include patients’ quality of life and patient-based functional assessments. Age- and gender-specific differences should also be addressed in future studies.