Perforator Flaps For Patellar Defects
Overview
This study explores the use of pedicled fascio-cutaneous perforator flaps, specifically the descending genicular artery perforator (DGAP) flap, for reconstructing complex peripatellar defects. While free flaps and pedicled muscle flaps are more commonly employed for this purpose, the DGAP flap is presented as a viable and often overlooked option due to its thin and pliable tissue, making it an ideal choice for ‘like with like’ reconstruction of peripatellar soft tissue defects.
The study conducted a retrospective cohort analysis of complex peripatellar defect reconstructions with DGAP flaps from January 2011 to December 2018. The research involved a review of patient demographics, medical comorbidities, defect characteristics (size, location, etiology), and an assessment of flap, donor site, and overall surgical outcomes. The results were analyzed using descriptive statistics through IBM SPSS Statistics 23.
The study included five consecutive cases, with complex peripatellar defects ranging from 5×8 to 8×10 cm in size. The patient group consisted of two males and three females, with an average age of 38.4 years. Four cases were due to trauma, while one was related to an oncological condition. Notably, the study found consistent patterns of descending genicular artery (DGA) perforators and terminal branches.
In the course of the surgeries, one patient required a split-thickness skin graft to address secondary defects. Encouragingly, all the DGAP flaps survived, and the patients were monitored over an average follow-up period of 24 months.
The study concludes that the DGAP flap represents a dependable alternative to free flaps for reconstructing large and complex peripatellar defects. By including the proximal long saphenous vein and carefully selecting DGA perforators and terminal branches, the DGAP flap can be safely harvested and utilized, even in cases involving high-velocity impact on the knee. This research demonstrates the effectiveness of the DGAP flap and provides valuable insights into its use for peripatellar defect reconstruction.
Introduction
The human knee, being the largest hinge joint in the body and vital for bipedal locomotion, often faces complex issues such as peripatellar defects resulting from various factors, including high-speed trauma, chronic wounds, burns, and oncological resections. These defects present as intricate wounds, often contaminated, with substantial soft tissue damage. They may also involve bony and vascular injuries, and in oncological cases, the wound bed could be irradiated before or after surgery. Peripatellar defect reconstruction is thus a challenging task for reconstructive surgeons.
For ideal peripatellar reconstruction, several factors come into play. The reconstructed tissue should be thin and pliable to allow for knee flexion, extension, and rotations. Moreover, it needs to be durable and well-vascularized to resist infection and cover orthopedic prostheses. Traditionally, pedicled muscle flaps, especially pedicled medial gastrocnemius flaps, have been the primary choice for these reconstructions since their introduction in 1978. While these muscle flaps are robust and easy to raise, they are criticized for their post-reconstruction aesthetics and donor site morbidity due to muscle sacrifice.
In contrast to pedicled muscle flaps, fascio-cutaneous flaps are thinner and more pliable, offering tailored flap design with less donor site morbidity. Free perforator-based fascio-cutaneous flaps, such as the anterolateral thigh (ALT) flap and thoracodorsal artery perforator (TDAP) flap, have become preferred options for lower limb reconstruction in major trauma cases. Using a distant flap, when necessary, reduces the risk of harvesting tissue based on damaged perforators within the trauma zone or radiation area. However, free flap reconstructions are more technically demanding, require longer operation times, and leave an additional distant scar. Moreover, characteristics of distant soft tissue may not be as well-matched as those from locoregional flaps.
The pedicled perforator flap (PPF) has brought innovation to lower limb reconstruction by providing more flexibility in flap design, liberating it from the constraints of width-to-length ratios and enabling true “like with like” reconstruction. Dissecting the perforators further enhances the flap’s movement and design flexibility. Among the various PPF options for peripatellar reconstruction, the pedicled reverse ALT flap, medial sural perforator (MSAP) flap, and descending genicular artery perforator (DGAP) flap are commonly used.
The DGAP flap, initially described as the saphenous neurovascular free flap, can be raised as a pedicled or free flap. The descending genicular artery is a branch of the superficial femoral artery (SFA) and plays a vital role in the extensive peripatellar vascular network. It gives rise to saphenous, muscular, osteoarticular branches, and their respective perforators, making the DGAP flap versatile and suitable for various applications, including fascio-cutaneous or composite/chimeric flaps with bone, cartilage, tendon, and muscle components.
Despite early success with DGAP flaps, they haven’t been widely popularized, primarily due to anatomical variations in arterial branching patterns. This study aims to showcase the versatility of pedicled DGAP flaps for peripatellar reconstruction in patients with complex defects and shares surgical insights through a case series, contributing valuable knowledge to this field of reconstructive surgery.
Methods
This retrospective study involved consecutive complex peripatellar reconstructions using descending genicular artery perforator (DGAP) flaps, conducted by a single Plastic and Reconstructive Surgeon at multiple trauma centers in Melbourne, spanning from January 2011 to December 2018. The study aimed to evaluate patient demographics, medical comorbidities, and details about the defects’ causes, sizes, and locations, as well as to assess flap, donor site, and overall surgical outcomes. All procedures were carried out in compliance with the Declaration of Helsinki, with patients providing informed consent for data collection and the use of deidentified photos. Descriptive statistics were employed for data analysis using IBM SPSS Statistics 23.
The surgical technique began with patient preparation in the supine position, with the operative hip abducted, externally rotated, and the knee slightly flexed. Perforators of the descending genicular artery, located at the distal 1/3 of a line drawn from the anterior superior iliac spine (ASIS) to the medial end of the knee joint, were localized using a handheld Doppler. A tourniquet was applied but only during flap dissection to enhance the surgical field.
The posteromedial approach was adopted with the initial incision made along the posteromedial margin of the flap to optimize perforator inclusion and vascular preparation. Proximally, dissection extended until the proximal portion of the long saphenous vein was identified. Subfascial plane dissection continued postero-medially until the anterior edge of the sartorius tendon became visible. Gently retracting the sartorius tendon posteriorly revealed musculocutaneous perforators from the saphenous artery. All flaps were raised as sensate flaps with the constant inclusion of the infra-patellar branch of the saphenous nerve. The distal part of the saphenous nerve could be dissected off the flap if it hindered flap movement and inset, but the infrapatellar branch remained in the flap. The saphenous artery’s fate distal to the sartorius tendon depended on requirements. It could be dissected off or ligated if it interfered with flap movement and inset, or included with its perforators if additional blood supply was needed. If a vascularized sartorius tendon was required in the flap, the saphenous artery with its vascular pedicle to the sartorius tendon could be included. The long saphenous vein was also included in the flap to enhance venous drainage.
All identified perforators were preserved during flap harvesting, and microvascular clamps were applied to peripheral and small perforators. Flap perfusion was assessed based on selected central perforator(s). Once the circulation was deemed satisfactory, the flap was islanded, and redundant perforators were divided to facilitate flap mobilization. In cases where flap circulation was unsatisfactory, clamped perforators were released sequentially until adequate circulation was restored. Finally, the distal part of the long saphenous vein was ligated, and the flap harvesting was completed. The circulation of the flap was verified by checking bleeding from the flap edges for its color and speed, ensuring adequate circulation at all corners of the flap before the inset.
Postoperative care involved monitoring vital signs every four hours and assessing flap vascular observations, such as capillary refill, temperature, texture, and consistency through the dressings. Dressings remained intact for a week and were only to be changed by senior medical staff. Deep vein thrombosis (DVT) prophylaxis was provided with heparin 5000 units BD, and no aspirin was administered. Patients were encouraged to engage in early mobilization with a Zimmer knee splint starting from the first day post-op, unless contraindicated by associated injuries or orthopedic procedures.
Result
This study enrolled five consecutive patients for reconstructive procedures involving peripatellar defects. The patients included two males and three females, with ages ranging from 13 to 55 years (mean age = 38.4 years). Four of these cases were due to trauma, with three of them stemming from high-velocity traumas. The remaining case involved a peripatellar defect resulting from the resection of a malignant fibrous histiocytoma. In the trauma cases, computed tomography angiography (CTA) was employed for reconstructive assessments, while magnetic resonance imaging (MRI) was used for the oncological case. All five cases required reconstructive procedures, and sensate pedicled fasciocutaneous DGAP flaps were used to address peripatellar defects ranging from 5 x 8 to 8 x 10 cm in size. Four of the DGAP flaps were applied as advancement flaps, which included two keystone flaps, while one was used as a propeller flap. Intraoperatively, DGAPs were consistently present, and the descending genicular arteries (DGAs) were consistently divided into saphenous, muscular, and osteoarticular branches, along with their respective perforators. Only one patient required a split-thickness skin graft to address secondary defects. All flaps successfully survived the procedures without immediate complications, and only one patient experienced delayed wound dehiscence, which necessitated debridement and primary closure. All cases resulted in aesthetically acceptable outcomes with adequately recovered knee function. One patient reported non-specific pain over the lateral leg, despite an intact saphenous nerve observed on an MRI scan. Follow-up periods ranged from 6 to 60 months, with an average follow-up duration of 24 months.
A detailed case report is as follows:
Case 1 (Trauma Case):
A 45-year-old female with poorly controlled type 1 diabetes mellitus initially presented with a right knee defect following a fall, which later complicated into osteomyelitis and failed skin graft reconstruction. Multiple debridements, including partial patella osteectomy, were performed, with the Orthopaedic Unit addressing the knee extensor mechanisms. The patient received 6 weeks of vancomycin for methicillin-susceptible staphylococcus aureus (MSSA) coverage and improved blood glucose level control by the Endocrinology unit. A patella defect measuring 5 x 12 cm was ultimately reconstructed with an ipsilateral DGAP flap and a split skin graft for secondary defect reconstruction. No flap-related complications occurred, and the patient was advised to have strict leg rest for one week, followed by mobilization with a Zimmer knee splint. Wound healing was achieved by day 14, and she was discharged for rehabilitation on day 17. The Zimmer knee splint was replaced with a hinged knee brace in the seventh week for three months. The patient exhibited a knee movement range of 10–100 degrees at the six-month mark, and the reconstructed knee displayed satisfactory aesthetics in terms of contour and color.
Case 2 (Oncological Case):
A 13-year-old female presented with malignant fibrous histiocytoma affecting her right knee, necessitating a 3 cm margin down to the patella tendon. The resulting defect measured 6 x 9 cm and exposed the patella tendon. Initially planned for a gastrocnemius flap and skin graft, the reconstruction approach was altered to a DGAP flap to reduce donor site morbidity and enhance post-reconstructive aesthetics. The patient had an uncomplicated recovery and was discharged on the fifth day, equipped with a Zimmer knee splint. Physiotherapy sessions commenced in the third week, and a full range of motion was achieved by two months. At the 60-month follow-up, no tumor recurrence was observed in an MRI scan.
Case 3 (Trauma Case):
A 55-year-old man presented with an exposed metal prosthesis after undergoing left total knee replacement and patella tendon repair following a motorcycle accident. Examination revealed atrophied gastrocnemius muscles, which were insufficient to provide adequate metalware coverage, thereby increasing the risk of future metalware exposure. Following debridement, the peripatellar defect measured 6 x 12 cm. A sensate pedicled fascio-cutaneous DGAP flap was used for defect reconstruction. The patient experienced an uncomplicated recovery and was discharged on the seventh day. Functional training led to good knee flexion at the three-month follow-up, and acceptable knee function with satisfactory post-reconstruction aesthetics was observed 36 months after the surgery.
Conclusion
The Pedicled Perforator Flap (PPF) has significantly revolutionized the field of Reconstructive Surgery, particularly for soft tissue resurfacing applications. This concept was first introduced by Kroll and Rosenfield and later formally named by Koshima and Soeda in 1989. PPFs offer several advantages over traditional muscle flaps. Their extended pedicles provide greater freedom in flap inset, enhancing accuracy in flap design and facilitating a more precise reconstruction. This approach also minimizes disruption to underlying muscles, reducing postoperative muscular atrophy and pain, which, in turn, enables early rehabilitation. The DGAP (descending genicular artery perforator) flap, a type of PPF, offers unique benefits for lower limb reconstructions, specifically in the upper 1/3 of the limb. These flaps offer a combination of tissues for complex defect reconstructions, matching the color and contour of the regional tissue, resulting in aesthetically superior outcomes compared to complex microsurgical free flap procedures.
One of the significant advantages of using a pedicled DGAP flap for peripatellar reconstruction is its versatility. Surgeons can tailor the design of the flap to match the shape of the defect. The case series presented in this study demonstrates the successful reconstruction of peripatellar defects of various sizes and etiologies using DGAP flaps. These flaps offer thin and pliable tissue that enables functional rehabilitation of the knee while also providing durability to cover exposed metalware and resist deep wound reinfection. Furthermore, raising a sensate pedicled DGAP flap that includes the saphenous nerve helps protect the reconstructed knee and minimizes the risk of insensate-related wound complications.
The study included cases with peripatellar defects ranging from 4 to 6 cm (moderate) to larger than 6 cm (large), stemming from chronic wounds, patella osteomyelitis, exposed metal prostheses, oncological resection, and high-velocity trauma. The DGAP flap proved efficient in covering these defects. The concept of “flap efficiency” was used to quantify the degree of defect coverage in relation to the flap size. The calculated efficiency of the DGAP flap was found to be 78%, demonstrating its high efficacy for peripatellar reconstruction compared to other pedicled perforator flaps.
While the anatomy of the descending genicular artery (DGA) and its tributaries may exhibit variations in the peripatellar region, these variations are attributed to the complex vascular network in this area. The DGAP flap is primarily based on the descending genicular branch of the superficial femoral artery (SFA). The study found that the anatomy of the DGA system in the cases analyzed remained consistent, likely due to the small sample size. Regardless of variations in DGA anatomy, the DGAP flap can be safely harvested following the described surgical approach, and, in the absence of DGA, alternative sources such as the saphenous artery or superior medial genicular artery (SMGA) can be utilized.
In summary, the DGAP flap offers a versatile and efficient solution for peripatellar reconstruction, providing excellent aesthetics, functional rehabilitation, and protective sensation over the reconstructed knee. By optimizing the selection and inclusion of available cutaneous perforators and DGA terminal branches, surgeons can successfully raise DGAP flaps, even in traumatized legs. Careful consideration of venous drainage further enhances the effectiveness of this approach and reduces the risk of complications associated with venous congestion. This study underscores the DGAP flap’s value as a reliable alternative to microsurgical reconstruction for large and complex peripatellar defects.
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