Case 2: Perforator-based soft tissue reconstruction around the knee, utilizing a D-POP ALT flap
Keywords: Distal ALT perforator, Propeller flap, Malignant melanoma, D-POP-flap
Authors: Abdullah Najib Maalouf (MD) and Peter Sinkjær Kenney (MD, PhD). Vejle Sygehus & Aarhus University Hospital, Denmark
A 73-year-old woman presented with malignant melanoma (pT2b-tumour) on her left thigh, located approximately 10 cm above the knee. The excision procedure aimed to remove the melanoma with a margin of 20 mm and perform sentinel node biopsy according to the protocols from Danish Melanoma Group (DMG). The patient had chronic obstructive lung disease, hypertension, hypercholesterolemia, ulcerative colitis, and migraine. Additionally, the patient smoked 10 cigarettes per day.
Before and after
Patient examination
The patient was seen in an outpatient setting first. She reported to have good general health and was self-reliant. The initial excision biopsy, performed in a dermatology setting with close margins, revealed a superficial spreading malignant melanoma with ulcerations but no presence of mitosis, margins were deemed clear. Adhering to the DMG-protocols, re-excision was planned to muscle fascia and a total margin of 20 mm. On examination, we found insufficient tissue for direct closure and due to functional considerations planned a flap reconstruction.
Pre-Operative Considerations
Soft tissue reconstruction in the knee region can be complex. Functionally, the aim is to restore natural mobility without any restrictions or contractions. Aesthetically, the aim is to adhere to the natural contours and achieve acceptable symmetry to the contra-lateral knee region. For functional reasons, skin-grafting is not deemed an optimal reconstructive approach as this may lead to contraction and restrictions in movement. Skin-grafting coupled with a local muscle flap, for example a gastrocnemius flap, can have untoward donor-site morbidity and a less than optimal aesthetic outcome. In more extensive cases, free flaps can be necessary, however these surgeries are not without risk for co-morbid elderly patients and also have an inherent risk of thrombosis or venous stasis. Local random flaps could be used; however, these would need significant size to be safe, especially given the patient’s active smoking status. For these reasons, a perforator-based approach was considered. A recently published case series described the use of a distal perforator-only propeller anterior lateral thigh flap (D-POP ALT) for reconstruction around the knee (1). This flap is based on the most distal perforator of the descending branch of the lateral circumflex femoral artery (LCFA). It is typically found 4-9 cm superior-lateral to the border of the patella pointing towards SIAS. In the case series, flap lengths of 25 cm and widths up to 6 cm were used. Pre-operatively, the surgeon (PSK) used Dupplex ultrasonography to identify the distal perforator. Dimensions of the flap were adjusted to ensure tension-free closure of the secondary defect, with the pivot point on the dopplered perforator. The patient was informed of the procedure, potential risks and the postoperative measures in order to best aid flap survival. Usually, the patients are discharged from the hospital on the same day. In some cases, the patient stays overnight if the flap requires close monitoring. The D-POP ALT flap both ensured satisfying reconstruction and minimal functional limitations, especially when we take the patient’s overall health status and smoking history into consideration.
Step 1: Preoperative markings
Two perforators were identified with doppler, of which the most distant is the basis for the D-POP ALT flap.
Step 2: Perioperative measurements and identification of D-POP
The soft tissue defect resulting after re-excision was located on the anterolateral part of the left thigh measured 45×45 mm in size. Flap harvest was commenced above the fascia. By the use of the handheld Doppler the signal from the perforator was closely monitored.
Step 3: Reconstructive method
The perforator can be dissected intramuscularly or intraseptally to enable sufficient flap mobilization and unrestricted propeller technique. In this case it was not necessary to dissect subfascially. Subsequently, the flap was rotated 90 degrees into the defect, while the donor site was closed directly. Suturing the flap was done using interrupted deep dermal sutures with 4-0 Vicryl followed by a running dermal suture with 4-0 Nylon. Some surgeons add Nitroglycerine ointment to further support the permeability in the flap, but it is not a standardized requirement.
Step 4: Day 1 after the surgery.
On this stage of the process meticulous precautions must be taken in order to avoid adding pressure on the flap, since this could jeopardize the flap’s vitality and thereby risk flap loss. Upon inspection, slight bruising and some swelling was seen. Flap was viable. No actions taken.
Step 5: Day 10 after the surgery.
Upon the visit in our outpatient clinic, the results were satisfying with no signs of infection, pain or any complaints from the patient. The flap was viable. Nylon was removed.
Step 6: Follow-up after 4,5 months (via cell phone).
The patient had no functional limitations and she indicated that she had full range of motion without limitation as prior to surgery. Furthermore, there were no complaints in regards to pain or aesthetics. The patient indicated sensational disturbances in the area around the flap, but stressed that it did not affect her quality of life.
Post-Operative Plan
The patient was admitted for the first 24 hours with no specific scheme for monitoring the flap. The patient was recommended to avoid flexing the knee beyond 60 degrees for the first few weeks. Furthermore, the patient was instructed to avoid pressure on the flap until removal of the sutures. The patients underwent a standard follow-up 10-14 days after the surgery. Generally, no further controls are required, except in unique cases where the surgeon schedules a 3 months follow-up after the surgery.
- The technique is simple, dependable and fairly straightforward.
- The technique ensures high-quality and cost-effective reconstruction while upholding function and aesthetics.
- The D-POP technique minimizes the risk for venous congestion due to its anterograde flow.
- A perforator based approach should be more reliable compared with a random flap design.
- Large flaps can be done, without sacrificing the main ALT pedicle, which can be used later if required.
- Thickness of the flap – can give a bulky appearance
- Careful identification of a pivot point for the flap in order to ensure complete rotation
- The perforator exhibits an uncommon yet well-recognized possibility of anatomical variation, which can pose challenges during flap harvesting. Intraseptal or intramuscular dissection can be carried out depending on the location of the perforator, here it was unnecessary.
- For medially-based knee defects a D-POP ALT may not be optimal due to the distance from the pivot point. In these cases, a free-style flap based on a perforator from the superficial femoral artery along the sartorius muscle should be considered.
References
- Distal perforator-only propeller (D-POP) anterolateral thigh flap for reconstructions around the knee: 4-year experience, Damir Kosutic, Published:December 01. 2019DOI:https://doi.org/10.1016/j.bjps.2019.11.036
- Bekarev M, Goch AM, Geller DS, Garfein ES. Distally based anterolateral thigh flap: an underutilized option for per- i-patellar wound coverage. Strat Trauma Limb Reconstr 2018;13(3):151–62.