Vascularized Medial Femoral Condyle Corticoperiosteal Bone Flap



10.1055/b-0034-78114

Vascularized Medial Femoral Condyle Corticoperiosteal Bone Flap

Maureen C. McKenna, Theresa McKenna, and Steven L. Moran

Vascularized bone grafts have been used in reconstructive surgery for over a century for the treatment of nonunions and large bony defects. Research has shown that vascularized bone grafts have many advantages over nonvascularized bone grafts, including the preservation of osteocytes, diminished osteopenia, and accelerated graft consolidation without the need for creeping substitution. Historically, vascularized bone grafts from sources such as the fibula, rib, or iliac crest have been used when bony defects exceeds 5 cm in length. Unfortunately, nonunion sites less than 5 cm in length, particularly those that are in areas of preexisting infection, avascular necrosis, or radiation, may not be amenable to the use of nonvascularized bone grafts and may require vascularized bone graft to obtain bony union. In such situations, the classic sources of vascularized bone grafts, such as the fibula or iliac crest, are excessive in size, resulting in unnecessary donor site morbidity and prolonged rehabilitation. For these specific circumstances we have opted to use the the medial femoral condyle corticoperiosteal (MFC) flap. This flap can provide a versatile source of vascularized bone with limited donor site morbidity and requires minimal time for flap harvest.


The MFC flap was originally described by Masquelet and then popularized by Doi.14 Vascularized periosteal flaps have been shown to provide an effective approach to treating poorly vascularized nonunions in which bony structural loss is minimal. Potential sites of periosteal flap harvest can include the MFC or the humerus, ulna, radius, iliac fossa, tibia, and femur.1 Over the past two decades, the MFC has become a popular first choice for periosteal flap harvest due to its reliable anatomy, flexibility, size, and minimal donor site profile. Although all periosteal flaps can be elevated alone (without the underlying bone), disrupting the strongly adherent Sharpey fibers between the periosteum and cortex risks injury to the cambium layer; injury to this layer decreases the osteogenic potential of the graft. As such, studies have recommended including a layer of cortex when harvesting the flap, thus minimizing the risk of injury to the cambium layer.59



Indications




  • The MFC corticoperisoteal bone graft has been shown to be a reliable flap for reconstruction of bony defects of the upper extremity, including the clavicle, humerus, radius, ulnar, scaphoid, lunate, metacarpal, and phalangeal bones.1013 More recent reports have described the versatility of the flap being harvested with both skin and muscle, allowing it to be used for a variety of composite defects.13



  • The MFC flap is usually elevated in one of three major patterns:




    1. A corticocancellous block of bone of up to 3 × 3 cm for use as a structural wedge graft in cases of collapsed scaphoid nonunions, metacarpal and phalangeal defects, and (in some cases) distal radius nonunions ( Fig. 27.1a )



    2. An osteocartilaginous graft for management of articular defects in the scaphoid, radius, or lunate



    3. A thin corticocancellous sheet of bone that can be wrapped around tubular bones, such as the clavicle, humerus, or ulna, for cases of recalcitrant non-union ( Fig. 27.1b )



  • General indications for this procedure include small nonunions that have failed traditional therapy or patients at high risk for contemporary nonvascularized graft failure (such as proximal pole scaphoid non-union). Other indications would include:




    • Recalcitrant bony nonunions due to infection, radiation-induced osteonecrosis, or avascular necrosis



    • A bone defect (3 × 3 cm) with composite soft-tissue loss (a skin paddle of 3 × 3 cm or larger may be taken with the flap as well as a portion of the vastus medialis if muscle coverage is required for coverage of composite bony defects)



    • Small bony defects (up to 3 × 3 cm) where harvest of a fibular or iliac crest would be excessive (the small size of the MFC flap reduces risk of donor site morbidity and serves as an ideal flap for defects that necessitate coverage with a thin and pliable flap with minimal bulk)



Contraindications




  • Bony defects in uncomplicated nonunions should be managed initially with conventional grafting or pedicled vascularized bone grafts, prior to moving to an MFC flap. In addition, the MFC flap should not be the first choice in cases where the bony defect is larger than 3 to 5 cm. LaPierre has described using MFC grafts with dimensions as large as 13 × 8 cm.14 These findings have been further validated by Iorio, who in a cadaveric study found that the genicular system may be capable of perfusing flaps of up to 13 cm in length.15 Despite these findings, we would recommend using a graft with more structural integrity if the bony defect extends beyond 3 × 3 cm.

(a) Intraoperative image of a corticocancellous block, which is most commonly used for scaphoid and lunate reconstruction. (b) Intraoperative image of a thin corticoperiosteal flap, prior to pedicle division, which will be used to wrap around a humeral nonunion site.



  • Relative contraindications may include radiation to the region of flap harvest or significant peripheral vascular disease involving the adductor canal or popliteal area, as these may compromise the arterial pedicle to the flap.



  • Previous knee surgery that has injured or ligated the genicular arterial system, which feeds the MFC flap, obviously will prevent the successful use of the flap.


Other patient-specific contraindications in cases of scaphoid nonunion, Preiser disease, or Kienböck disease would be the existence of radiocarpal arthritis.



Preoperative Examination and Imaging


There are few requirements for preoperative imaging when using this flap. The anatomy (discussed below) is very reliable. Attention instead is given to the nonunion site to verify the size of the defect, the bony dimension required for reconstruction, and to rule out evidence of ongoing infection. In general, imaging is performed for the following:




  • Preoperative assessment of nonunions and carpal collapse can be assessed with a CT scan. In addition, preoperative CT scans of the nonunion site allow for templating of the required graft dimensions. An MRI with gadolinium contrast is used to rule out avascular necrosis of the involved carpal bone.



  • CT angiography or an MR angiogram can be considered in patients with previous knee surgery, significant atherosclerosis, or previous knee trauma to verify the patency of the genicular arterial system.



Anatomy




  • The anatomy of the MFC flap has been studied extensively and most recently by Yamamoto and Iorio.15,16 The bone flap is located over the medial femoral condyle and is bound by three borders: posteriorly by the border of the femur, anteriorly by the medial patellar facet, and distally by the medial collateral ligament.



  • The flap is nourished from two sources: the descending genicular artery (DGA) and the medial superior genicular artery (SGA). The DGA originates from the femoral artery just distal to the adductor hiatus. It lies just deep or lateral to the adductor magnus tendon along the posterior aspect of the medial intermuscular septum.



  • The DGA has three branches, including an articular branch, a muscular branch, and a saphenous branch. The articular branch feeds the periosteum, the muscular branch nourishes the vastus medialis muscle, and the saphenous branch supplies the overlying skin. Yamamoto and colleagues studied the arterial anatomy to the medal femoral condyle in 19 cadavers. They discovered the DGA was present in 89% of the specimens, with the artery originating on average 13.7 cm from the articular surface of the knee. At its origin, the vessel had an average internal diameter of 1.5 mm (range 1 to 2 mm). An osteoarticular branch was present in 89% of specimens, branching from the DGA ~ 11.3 cm (range 5.5 to 15 cm) from the knee joint, and this branch had an average internal diameter of 1.1 mm (range 0.63 to 1.5 mm). Seventy-nine percent of specimens had an identifiable saphenous branch perfusing the skin; this branch travels with the saphenous nerve16 ( Fig. 27.2 ).



  • The SGA originates from the proximal portion of the popliteal artery. In Yamamoto′s anatomic study, this vessel was present in 100% of the specimens, with the origin of the vessel just 5.2 cm from the articular surface. The vessel has an average internal diameter of 0.78 mm at its origin, with a range of 0.38 to 1.4 mm. The vessel crosses from behind the adductor magnus tendon to anastomose with the osteoarticular branch of the DGA contributing to the perforating vessels over the condyle. The superior medial genicular artery was the dominant vessel supplying the medial femoral condyle in two of the specimens in Yamamoto′s study16 ( Fig. 27.2 ).

Schematic of the anatomy of the descending genicular artery (DGA) and medial superior genicular arterial (SGA) system. The DGA has perforators to the bone (via the osteoarticular branch), skin (via the saphenous branch), and the muscle. The superiomedial genicular branch has a shorter pedicle length and smaller internal diameter than the DGA.



  • The preferred vascular supply to the flap is the DGA, as it has a longer pedicle length (5–10 cm) and larger internal diameter than the SGA, facilitating microvascular anastomosis.



  • The SGA, while smaller in diameter than the DGA, is still a very reasonable option when longer pedicle length is not required, as in cases of Kienböck′s disease and some cases of scaphoid nonunion. In addition, the SGA has a good diameter vessel match when performing an end-to-end anastomosis to side branches of the radial artery ( Fig. 27.3a–c ).



  • An average of 30 arterial perforators to the medial femoral condyle have been reported. The perforating vessels run perpendicular to the cortex and extend to an average depth of 13 mm. The majority of perforators lie in the posterior medial quadrant of the condyle.16 Care should be taken to identify these perforators and include them within the bone flap.



  • Finally, if a skin paddle is to be taken with the flap, it is necessary to separate the saphenous nerve from the saphenous branch of the DGA. Injury to this nerve will result in paresthesia or dysesthesias over the anterior medial aspect of the parapatellar/pretibial region of the leg.

(a) Clinical example of a bone flap based on the SGA; note the short length of the pedicle. The flap was used to revascularize the lunate in a 21-year-old woman with Kienböck′s disease. (b) The patient was noted to have stage 3a disease prior to surgery. (c) A wrist AP radiograph at 3 years following surgery showing stabilization of lunate with clinical resolution of wrist pain.

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Jun 28, 2020 | Posted by in PHYSICAL MEDICINE & REHABILITATION | Comments Off on Vascularized Medial Femoral Condyle Corticoperiosteal Bone Flap

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