Free-style Approach to the Pedicled Lower Medial Thigh Perforator Flap

Summary:

Soft tissue reconstruction around joints such as the knee requires a few additional considerations compared with other regions. The overlying skin must be pliable, with adequate distensibility to maintain the range of motion as a hinge joint, and ideally be replaced with “like-for-like” tissue to restore its delicate contour. The advent of perforator flaps has provided reconstructive surgeons with thin, pliable flaps conferring superior aesthetic results, good preservation of joint range of motion, and less donor site morbidity. Utilizing locoregional options also allows replacement with “like-for-like.” We retrospectively reviewed lower medial thigh perforator flaps performed for traumatic and debrided infected knee wounds, using a free-style approach to flap harvest. The described technique was found to be reliable, with consistent anatomy. All flaps survived and successfully covered small- to medium-sized critical defects in healthy individuals and those with multiple comorbidities.

INTRODUCTION

Fasciocutaneous flaps offer an ideal alternative to the conventional gastrocnemius workhorse flap, providing thin, pliable, and aesthetically superior soft tissue coverage. Perforator flaps from the lower medial thigh region have been described using various nomenclatures,^1–3 owing to a complex vascular network around the knee.

The lower medial thigh perforator (LMTP) flap was described by Scaglioni et al in 2015 as a free perforator flap for head and neck reconstruction, and later as a propeller flap for knee reconstruction.⁴ We present our experience with six cases, using a free-style approach to the pedicled LMTP flap for reconstruction of knee defects.

MATERIALS AND METHODS

A retrospective review was conducted for all patients with critical knee defects (eg, exposed bone, tendon, or implant requiring soft tissue coverage) requiring flap reconstruction from September 2017 to September 2020 in a single tertiary center.

Patient demographic data, defect characteristics, flap reconstruction performed, perioperative details, and outcomes were collected before analysis. Patient identifiers were not included. Institutional review board approval was obtained for the data collected.

Flap Anatomy

Perforators to the LMTP flap may arise from any four arterial sources: the superficial femoral artery, descending genicular artery (DGA), saphenous artery, and superomedial genicular artery (SMGA). The DGA originates from the superficial femoral artery at the level of the adductor hiatus (11.9–17 cm above the joint line) and has a robust branching system that includes the saphenous artery, muscular branches, and osteoarticular branches.^5,6 The superomedial genicular artery originates from the popliteal artery at an average of 4 cm above the medial condyle, 2 cm medial to the longitudinal axis of the leg. The origin of the saphenous artery is variable and may be absent. When present, it may arise as a branch of the DGA or originate directly from the femoral or popliteal artery.⁶ These serve as a reliable source of skin perforators for flaps in the medial knee and distal thigh, with a highly variable angiosome area. Furthermore, many anastomoses exist between these arteries in this region.

Surgical Technique for the Lower Medial Thigh Perforator Flap

The LMTPs were identified preoperatively using a handheld vascular Doppler. A V-Y rotation-advancement skin paddle design was then marked out around these perforators, guided by medial thigh tissue laxity (Fig. 1). The thigh was routinely positioned on a stack of surgical towels to flex the knee to about 30 degrees flexion, allowing the critical knee defect (eg, exposed bone tendon or implant requiring soft tissue coverage) to be reconstructed on stretch. Subfascial elevation of flaps was performed (Fig. 2) until the perforators could be identified in the interface between the vastus medialis and sartorius muscles, over the distal third of the medial thigh. Perforator dissection may be performed further proximally to maximize the degree of flap advancement. Suction drains were placed in the subcutaneous plane before layered closure (Fig. 3) of the flap inset and donor site.

Fig. 1.

Marked perforators and V-Y skin paddle design for anterior knee defect.

Fig. 2.

The lower medial thigh perforator flap.

Fig. 3.

Flap inset and closure.

Postoperatively, our patients were placed on an incisional negative pressure wound therapy dressing and a knee-spanning backslab for the first 5 days before conversion to a functional knee brace. Protected weight bearing was gradually allowed from 2 weeks postsurgery.

RESULTS

Twenty flap reconstructions for critical knee defects were performed during the study period. Of these 20 flaps, there were 10 pedicled gastrocnemius (medial or lateral) muscle flaps, six pedicled LMTP flaps, and four local flaps.

The average age of patients who underwent LMTP flaps was 58.5 years. The most prevalent comorbidities within each patient group were smoking, diabetes, and ischemic heart disease.

Most wounds were a result of either trauma from motor vehicle accidents (40%) or infection (55%). The majority (90%) were moderate- to large-sized defects. Twenty percent of the defects extended to involve the distal thigh or proximal tibia.

All flaps survived and provided successful soft tissue coverage of critical knee defects. Overall complication rate was 5% (1 of 20): One gastrocnemius flap was complicated by superficial infection requiring debridement. Time taken to complete wound healing and length of hospital stay was expectedly shortest for local flaps (21 days and 5.5 days) and longest for gastrocnemius flaps (41.2 days and 20 days). This is likely reflective of more severe injuries and larger wound sizes in the gastrocnemius flap group.

DISCUSSION

With the reintroduction of fasciocutaneous flaps by Pontén in 1981 and subsequent perforator vascular studies by Nakajima et al, a new paradigm in flap selection protocols emerged for lower extremity reconstruction.⁷ Furthermore, the concept of free-style flaps by Wei and Mardini⁸ has been extrapolated to applications in perforator flap harvest in the upper medial thigh,⁹ termed “upper medial thigh perforator flap” to reflect the heterogeneity of perforators in this region. Similarly, the angiosomes over the lower medial thigh are highly variable, and a free-style approach to raising flaps in this region would likewise be applicable.

In our series of cases, the LMTPs were found to be reliably present, allowing safe flap elevation up to the mid-thigh. Most of the identified perforators were found to arise from the DGA arterial system (Fig. 4). Laxity of tissue around the thigh allowed easy mobilization of the flap, tension-free inset, and primary closure of the donor site. In contrast, the use of a more conventional gastrocnemius flap and skin graft would have resulted in two donor sites (calf and thigh), some functional loss from the harvest of a muscle, and a poorer color match.

Fig. 4.

Knee reconstruction algorithm.

Knee Reconstruction Algorithm

Despite its advantages, the LMTP flap is not a “one-size-fits-all” option, and we recognize that some situations still warrant a conventional muscle flap. Main defect-related considerations in flap selection included the (1) wound etiology, (2) size of the critical defect and whether this extended beyond the knee to involve the distal thigh or proximal tibia region, and (3) availability of the LMTP and skin as a donor site.

Taking these factors into consideration, our observations suggest that the vast majority of defects around the knee can be reconstructed using one of the three techniques: LMTP flap, pedicled gastrocnemius muscle flap, or local flap. The LMTP flap can be safely used for moderate-sized (10–50 cm²) knee defects arising from both trauma and infection. Our series has also proved its efficacy in patients with multiple comorbidities. However, large defects may still require the conventional gastrocnemius muscle flap, which was the favored option in half of our cases.

SUMMARY

Soft tissue reconstruction around joints such as the knee requires a few additional considerations compared with other regions. The overlying skin must be pliable with adequate distensibility to maintain the range of motion as a hinge joint, and ideally replaced with “like-for-like” tissue to restore its delicate contour.

The advent of perforator flaps has provided reconstructive surgeons with thin pliable flaps conferring superior aesthetic results, good preservation of joint range of motion, and less donor site morbidity. Utilizing locoregional options also allows replacement of like with like tissue. Furthermore, donor sites are limitless as long as a significant perforator can be identified, and can be fashioned locally as a pedicled rotation, advancement, or propeller flap.¹⁰

The LMTP flap is a reliable alternative to the conventional gastrocnemius muscle flap for knee reconstruction, worthy to be included in the reconstructive armamentarium. It is simple to perform, obviates the need for two donor sites, does not require muscle harvest, and allows primary closure of the donor site with a scar inconspicuously placed in the medial thigh. As the evolution of lower extremity reconstruction continues in this new paradigm of perforator flaps, this represents yet another step forward in our quest to balance simplicity and reliability to find the “best flap” for various lower extremity wounds.