Microvascular free flaps from the lower abdomen for preservation of amputation length in the lower extremity

1 Introduction

Major injuries to the lower extremity always pose a severe threat to the patient with the possibility of loss of ambulation. Although lower extremity replantation may be a possibility in the acute traumatic setting [1], amputation is often unavoidable after extensive lower limb trauma, cancer or infection [2–5]. Under such circumstances, the level of amputation becomes a critical decision. Length preservation of the amputation stump is crucial for an optimal prosthetic fitting and therefore quality of life of the amputee [6–8].

Especially in traumatic amputations, there is frequently an insufficient local soft tissue envelope for coverage of the exposed bone. The possibility of bone shortening to achieve closure and adequate soft tissue coverage always comes with the downside of sacrificing stump length and therefore impairing the patient’s rehabilitation. Thus, shortening the already damaged extremity is not an option in selected cases in order to preserve the functionality of the remaining stump.

Reconstructive options for stump coverage typically include skin grafts, local or regional flaps as well as microvascular free flaps. The soft tissue envelope over an amputation stump has to be mobile to absorb shear stress and has to have proper contour and thickness for prosthetic fit [9]. Since there is an inherent paucity of available soft tissue locally, free flaps offer a versatile solution for sufficient coverage and preservation of extremity length. There have been several reports exploring the capacity of various free flaps for coverage of exposed amputation stumps of the lower extremity including the latissimus dorsi free flap, scapular flap, anterolateral thigh flap and others [10–18]. All of these flaps have distinctive advantages and disadvantages, and none has emerged as the ideal flap for lower limb stump coverage. The goal of this report is to present our experience with free flaps from the lower abdomen for stump coverage and to highlight why this donor site is our preferred treatment option for this highly selected patient group.

2 Patients and methods

Between March 2008 and October 2010, five patients (three female and two male patients) were treated for complex wounds on amputation stumps of the lower extremity. The mean age of the patients was 50 years with a range from 15 to 72 years. The etiology of the amputations was traumatic in four patients and a Marjolin’s ulcer of the amputation stump in the fifth patient. Table 1 lists the details of the five patients.

In all patients, sufficient coverage of the exposed bones could not be achieved primarily. To avoid bone shortening, a flap with a large surface was required for closure. Therefore, we transplanted six abdominal free flaps in five patients. Due to a bilateral amputation injury in one male patient (Patient #2), a split abdominal free flap was performed. There were four deep inferior epigastric artery (DIEP-) flaps (one hemi-DIEP) and two muscle-sparing transverse rectus abdominis muscle (ms-TRAM-) flaps.

Patient and operative data were collected retrospectively by means of a chart review. Parameters recorded included age, gender, occupation, cause of defect, amputation level, type of flap used for reconstruction, flap dimensions, recipient vessels, timing (delayed vs. elective), postoperative complications, length of hospital stay, functional outcome and length of follow-up.

Despite prompt surgical revision, there was one complete flap failure (hemi-DIEP-flap in Case #2) due to thrombosis of the femoral artery. This resulted in an overall success rate of 83.3%. In the patient with bilateral defects, a split-thickness skin graft led to eventual closure.

Mean flap dimension was 13±2,4 cm by 23±7,3 cm (range: width 10–17 cm, length 15–33 cm). Five thigh stumps and one lower leg stump were covered (two stumps on the left and four stumps on the right side). Mean length of hospital stay was 41 days. Patient follow-up ranged from 18 to 75 months. In all patients, a stable long-term result was achieved with three of five patients gaining full ambulatory ability with fitting protheses. Table 1 lists patient data and intraoperative details. Postoperative complications and outcomes are described in Table 2.

Preservation of extremity length is crucial for patients with below knee amputations but even more in patients with above knee amputations. Shortening of exposed bone for achieving primary wound closure dramatically reduces walking distance and quality of life [7] while increasing the amount of energy required for ambulation [8]. Thus, avoiding further reduction of bony length, reconstruction employing different flap options has to be considered.

The ideal stump cover is durable, weight bearing, mobile, sensate and comfortably enables prosthetic fitting. Different reconstructive options have been described in literature including local flaps, fillet flaps –spare part surgery, free muscle flaps or free perforator flaps [10–18]. Due to the innate paucity of local tissue in the lower extremity, local options are limited in most cases. Free flaps harvested from the amputated extremity have been described as fillet flaps or spare part surgery in emergency cases [16, 19]. However, for the patient presenting in the delayed or elective setting, this choice is not available.

Free muscle flaps have been successfully used for lower extremity stump coverage, with the free latissimus dorsi muscle being the most prominent donor muscle [9, 10]. However, muscle atrophy with consequent ulceration may gradually occur [12]. Especially in patients suffering from bilateral amputations, upper extremity strength with regards to usage of crutches might be diminished by choosing the latissimus dorsi muscle flap [19]. Furthermore additional skin grafting is needed, thus adding to donor site morbidity. Additionally, if secondary shaping is indicated, fasciocutaneous flaps are superior to muscle flaps in terms of safety and ease for reelevation, excision and liposuction [20, 21].

Free fasciocutaneous flaps comfortably meet the above mentioned criteria for the ideal soft tissue cover using a muscle sparing approach. Different flaps such as the scapular- (16), lateral arm- (16), parascapular- (17), groin- (14, 18), ALT- (15), TDAP- (22), medial circumflex femoral artery perforator (12) and medial sural artery perforator flaps [12] have been successfully employed for this purpose. However, none of these has emerged as the ideal flap for this indication. Certain disadvantages of the flaps described are the limited flap size, the need for split skin grafting of the donor site in larger flaps, a short vascular pedicle or the necessity of intraoperative repositioning of the patient [12–19, 22].

In contrast, the lower abdomen provides large amounts of available tissue enabling extensive defect coverage up to 12×33 cm (see Case 1). Primary closure of the donor site can be achieved in a standard abdominoplasty procedure without the need of secondary skin grafts, which might be necessary in ALT-flaps exceeding 8–10 cm in width. Furthermore a long vascular pedicle up to 14 cm in length with adequate vessel diameter of 2-3 mm is provided, thus allowing for comfortable flap inset without tension on the pedicle and safe microvascular anastomosis. Using tissue from the lower abdomen both, the leg and the donor site, are comfortably accessible, thus obviating the need for intraoperative repositioning of the patient i.e. when using the latissimus dorsi or scapular/parascapular donor-site. This saves time and a two-team approach is facilitated.

In addition to adequate tissue volume and size of the flap, a crucial factor for surgical outcome is the selection of suitable recipient vessels for microvascular anastomosis,. In both the lower leg and thigh several options exist apart the femoral artery and its main branches in the lower leg. At the level of the knee and below, the descending geniculate artery has been described as the ideal recipient vessel for free tissue transfer [23]. The anterior tibial system is preferred by other authors [24]. Additionally, the lateral circumflex femoral artery and its descending branch has recently emerged as another valuable recipient vessel especially at the mid to lower thigh [25, 26]. These vessels are easily accessible in the space between the vastus lateralis and the rectus femoris muscle and provide an adequate caliber-match for the deep inferior epigastric vessels. If these vessels are spared by the previous trauma we prefer the LCFA for microvascular anastomosis at the thigh because of the easy approach in a relative avascular plane, the suitable vessel diameter and the possibility for an end-to-end anastomosis.

We transplanted six abdominal free flaps in five patients with a mean flap dimension of 13 by 23 cm. However, to cover those extensive defects resulting from the three-dimensional wound configuration given in a thigh amputee, flaps as big as 12×33 cm were successfully utilized. In all patients a stable long-term result was achieved with three of five patients gaining full ambulatory status using prostheses (see Table 2).

6 Conclusion

Various free flaps have been described as treatment options for amputation stumps in the lower extremity. This is, to the best of our knowledge, the first report of a series of consecutive patients with stump reconstruction by means of abdominally-based free flaps. Owing to the low donor site morbidity with a muscle sparing approach, the possibility of direct closure of the donor site without the need of secondary skin grafting, a long vascular pedicle and the large amount of available tissue, abdominally-based free flaps represent our first microvascular choice for coverage of lower extremity stumps if local options are not available.