70: Medial Femoral Condyle Vascularized Bone Flap for Scaphoid Nonunion

Published on 19/04/2015 by admin

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Last modified 19/04/2015

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Procedure 70 Medial Femoral Condyle Vascularized Bone Flap for Scaphoid Nonunion

Pao-Yuan Lin, Sandeep J. Sebastin, Kevin C. Chung

imageSee Video 52: Free Medial Femoral Condyle Vascularized Bone Transfer for Scaphoid Nonunion

Indications

image The main indication is a history of previously failed bone grafting, with plain radiographic and magnetic resonance imaging (MRI) evidence of avascular necrosis associated with scaphoid foreshortening.

image If there are intraoperative findings showing no bleeding from the proximal and distal scaphoid, it is appropriate to reconstruct the defect with vascularized bone flap.

image Another indication of medial femoral condyle vascularized bone flap is atrophic nonunion of a long bone with a small bone defect that is surrounded by poorly vascularized bed.

image If the nonunion site has punctate bleeding after débridement, corticocancellous wedge bone grafting through the dorsal approach for proximal pole nonunion and through the volar approach for waist nonunion with humpback deformity should be attempted.

Examination/Imaging

Clinical Examination

image Patients present with radial-sided wrist or anatomic snuffbox tenderness.

image Patients may show decreased grip strength and wrist motion, particularly during extension.

Imaging

image Posteroanterior (PA), lateral, and oblique radiographs of the hand should be taken to assess any dorsal intercalated segment instability (DISI) deformities or scaphoid foreshortening.

image Bone scans are useful in visualizing the fracture 4 hours after injury, but not for detection of a nonunion.

image Computed tomography (CT) scans are useful in assessing pseudoarthrosis and show the extent of bone loss. Furthermore, they can pinpoint the exact position of the fractured fragments and determine whether there is any necrosis of the proximal pole. Humpback deformity may be revealed in sagittal views.

image An MRI with intravenous contrast (gadolinium) will help determine proximal pole vascularity. Cartilage erosions and osseous avascular necrosis are evaluated mainly in T1-weighted sequences.

Surgical Anatomy

Recipient Site: Vascular Anatomy of Scaphoid

image The major blood supply to the scaphoid is through the radial artery, which enters through the dorsal ridge and supplies 70% to 80% of the intraosseous vascularity to the entire proximal pole. This vessel and its branches enter distally and dorsally in retrograde fashion to the scaphoid. The dorsal vessels travel proximally along the dorsal scaphoid ridge, and the majority of vessels enter the scaphoid waist and continue as intraosseous vessels. The scaphoid proximal pole is uniquely susceptible to avascular necrosis following fracture owing to high dependence on a single dominant retrograde traveling intraosseous vessel (Fig. 70-1).

image Volar radial artery branches provide the blood supply to 20% to 30% of the bone in the region of the distal tuberosity.

image

FIGURE 70-1

Donor Site: Medial Femoral Condyle

image The superficial femoral artery gives off the descending genicular artery branch just proximal to the adductor hiatus. The descending genicular artery travels distally and gives off a saphenous branch proximally and musculare branches distally. The superior medial genicular artery arises from the superficial femoral artery more distally.

image The descending genicular artery and superior medial genicular artery continue distally, penetrate the bone, and provide the blood supply to the medial femoral condyle as intraosseous nutrient vessels.

image The saphenous branch of the descending genicular artery supplies the medial femoral condyle skin flap (Fig. 70-2).

image

FIGURE 70-2

Positioning

image The procedure is performed under general anesthesia and tourniquet control for the affected upper limb. The patient is positioned supine with the arm on a hand table. The ipsilateral knee is maintained in the position of slight flexion and abduction.

Exposures

image The scaphoid and radial artery are exposed by a palmar incision. This curvilinear incision extends proximally from the radial aspect of the thenar eminence parallel and radial to the flexor carpi radialis (Fig. 70-3).

image The medial femoral condyle of the ipsilateral medial knee and its nutrient vessels are exposed using a longitudinal lower medial thigh incision (Fig. 70-4).

image

FIGURE 70-3

image

FIGURE 70-4

Procedure

Team 1: Donor Site (Bone Graft Harvest)

Step 1

image The femur, patella, and femoral-tibial joint line at the ipsilateral lower medial thigh are marked. A skin incision line centered on the femur from the femoral-tibial joint to the proximal femur is drawn (see Fig. 70-4).

Step 1 Pearls

The incision line should be long enough (about 20 cm) to sufficiently expose the pedicle of the bone flap.

Step 2

image Skin is incised in longitudinal fashion, and the underlying subcutaneous tissues are dissected until the vastus medialis (VM) muscle fascia is exposed (Fig. 70-5).

image Hemostasis is adequately obtained with Bovie cautery during the soft tissue dissection.

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