70: Medial Femoral Condyle Vascularized Bone Flap for Scaphoid Nonunion

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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.

image

FIGURE 70-5

Step 3

image The VM muscle is elevated and retracted to the anterior side of the thigh, and the nutrient vessel of the medial femoral condyle bone graft is identified (Fig. 70-6).

image

FIGURE 70-6

Step 3 Pearls

It is easy to elevate the VM muscle from the distal-posterior aspect of the muscle in the loose areolar tissue plane between the VM muscle and medial femoral condyle.

Step 4

image Determine the sizable nutrient pedicle (usually the descending genicular artery) of the medial femoral condyle bone graft and dissect the pedicle proximally until an adequate length (5 cm) of vascular pedicle is mobilized (Fig. 70-7).

image

FIGURE 70-7

Step 4 Pearls

The pedicle length of the descending genicular artery is about 13.7 cm, and of the superior medial genicular artery, 5.2 cm. If anastomoses are planned at the radial artery in the wrist, a 5-cm pedicle length should suffice.

Step 5

image Based on the size of the defect, a rectangular medial femoral condyle bone graft is selected at the area where the distal nutrient branches of the descending genicular artery penetrate into the bone.

image The size of the bone graft should be sufficient to fill the defect. Bone graft from this location has sufficient cortical bone to provide a strong strut to correct the humpback deformity of the scaphoid. The distal radius bone graft typically does not have sufficient cortical bone strong enough to buttress the bone defect. The bone graft is usually 10 to 12 mm in thickness.

Step 5 Pearls

The medial collateral ligament of the knee is near the area of the bone graft and should be identified and protected.

Step 6

image The periosteum is sharply incised using a no. 15 blade, and the bone is cut with a small osteotome along the marking line (Fig. 70-8).

image

FIGURE 70-8

Step 6 Pearls

It is effective to elevate the pedicle from the more proximal bone with meticulous dissection before making the bone cuts.

To assist removal of the bone graft with less risk for fracture, an additional cut is made, angled 45 degrees just distal to the bone graft.

Step 6 Pitfalls

Care should be taken to protect the nutrient vessels while cutting the bone.

Step 7

image The vascular pedicle is ligated and divided.

image The bone graft is prepared and transferred to the recipient site for filling the scaphoid defect and performing microvascular anastomosis (Fig. 70-9A and B).

image

FIGURE 70-9

Step 7 Pearls

The length of the pedicle depends on the need of recipient site; usually 5 cm is enough.

Additional cancellous bone graft can be harvested to fill any defect in the proximal pole.

Step 8

image The defect created in the medial femoral condyle is filled with artificial bone graft.

image A suction drain is inserted, and the wound is closed in a layered fashion with absorbable sutures.

Step 9

image The patient’s knee is protected with a soft bulky dressing.

image A knee immobilizer is typically useful for patient comfort in the immediate postoperative period.

Team 2: Recipient Site Preparation and Microanastomosis

Step 1

image The skin and subcutaneous tissue are dissected along the incision line.

Step 1 Pitfalls

If the incision is too close to the thenar crease, it is easy to injure the palmar cutaneous branch of the median nerve.

Step 2

image The FCR sheath is opened, the tendon retracted ulnarly, and the floor of the FCR tunnel sharply incised longitudinally to expose the radiocarpal joint at the level of the scaphoid (Fig. 70-10).

image

FIGURE 70-10

Step 2 Pearls

The radioscaphocapitate (RSC) and long radiolunate (LRL) ligaments are identified and incised. Much of the LRL and a portion of the RSC are left intact to help stabilize the proximal pole.

Preserving this ligamentous support also helps maintain fracture reduction.

Volar capsulotomy in the scaphotrapezial joint is performed to improve the visualization of the scaphoid.

Step 3

image The scaphoid is then examined, paying attention to the articular cartilage of the radioscaphoid and midcarpal joints.

image A Freer elevator is used to define the location of the nonunion and the borders of the scaphoid.

image Fibrous and/or necrotic tissues at the proximal and distal poles are examined carefully. A small curet or rongeur is used for débridement and removal of intervening fibrotic tissue (Fig. 70-11).

image

FIGURE 70-11

Step 3 Pitfalls

The articulation between the scaphoid and capitate is carefully exposed to facilitate visualization during reduction.

Step 4

image The tourniquet is deflated to assess punctate bleeding from the nonunion site.

image The absence of punctate bleeding suggests avascularity, and further débridement is performed until punctate bleeding is confirmed (Fig. 70-12).

image The size of the bony defect is measured after débridement.

image A slow-speed bur is helpful to débride the fibrous nonunion, but the scaphoid must be constantly irrigated during burring to prevent additional bone necrosis.

image

FIGURE 70-12

Step 5

image The DISI deformity is corrected by flexing the wrist under fluoroscopic imaging until the radiolunate angle is neutral (Fig. 70-13A and B).

image The scaphoid is then prepared to accept the graft.

image

FIGURE 70-13

Step 6

image Recipient vessels (radial artery, concomitant vein, or cephalic vein) are dissected and prepared for anastomosis.

Step 7

image The bone graft harvested from the medial femoral condyle is further shaped to fit the defect.

image The flap is inserted into the defect, and Kirschner wires (or headless cannulated screws) are passed through the scaphoid and bone flap for fixation under fluoroscopic imaging to confirm correction of the scaphoid shortening and DISI deformity (Fig. 70-14).

image The K-wires should be left under the skin and removed when the bone has healed, typically 3 months after surgery.

image

FIGURE 70-14

Step 7 Pearls

It is better to place the periosteal surface (cortical surface) palmarly to preserve the vascularity of the bone flap, allowing the cortical bone to correct the humpback deformity.

Step 8

image The recipient artery (descending genicular artery or superior medial genicular artery) is anastomosed to the radial artery in an end-to-side fashion using 9-0 nylon sutures under microscopic magnification.

image The venae comitantes of the descending genicular artery or superior medial genicular artery is anastomosed to the venae comitantes of the radial artery or to the cephalic vein in an end-to-end fashion by 9-0 nylon sutures (Fig. 70-15).

image

FIGURE 70-15

Step 9

image After microanastomosis, the wound is closed with 4-0 nylon sutures (Fig. 70-16).

image A hand-held Doppler is used to detect the signal of arterial anastomosis, and the location is marked for postoperative monitoring.

image A thumb spica dorsal short-arm splint is applied to keep the thumb abducted and the wrist in slight flexion.

image

FIGURE 70-16

Step 9 Pitfalls

If the wound is closed too tightly, it is possible to compress the vessels.

Postoperative Care and Expected Outcomes

image The splint maintains the thumb in abduction and the wrist in slight flexion for 2 weeks.

image The stitches are removed 2 weeks after surgery, and thumb spica short-arm cast or splint (for a reliable patient) is applied for 8 to 12 weeks until the vascularized bone graft is united. CT scan can confirm healing of the scaphoid before allowing the patient to initiate unrestricted activities.

image The thigh is immobilized for a few days postoperatively until the patient feels comfortable.

Evidence

Doi K, Hattori Y. Vascularized bone graft from the supracondylar region of the femur. Microsurgery. 2009;29:379-384.

Thirty-three patients received medial femoral condyle vascularized bone grafts. Thirty-one of theses patients had achieved bony union. Eleven of the 33 patients were treated for scaphoid nonunions. In this study, the authors mentioned that this flap can achieve good results when used to treat the long bone with small bone defects, avascular necrosis of the talus, and scaphoid nonunions. (Level IV evidence)

Jones DBJr, Burger H, Shin AY, et al. Treatment of scaphoid waist nonunions with an avascular proximal pole and carpal collapse: a comparison of two vascularized bone grafts. J Bone Joint Surg [Am]. 2008;90:2616-2625.

Retrospective review of two vascularized bone graft (medial femoral condyle and distal radial pedicle graft) reconstructive groups from two different institutions. For distal radial pedicle grafts, 6 of the 10 cases failed, and the mean union time of success for the remaining 4 cases was 19 weeks. There was no significant change in the revised carpal height ratio or the carpal angles between preoperative and postoperative radiographs. In the medial femoral condyle bone graft group, all 12 cases united. The mean union time was 13 weeks. Comparing the preoperative and postoperative radiographs showed that the average decrease of lateral intrascaphoid angle and scapholunate angle was 25 degrees and 5 degrees, respectively, showing marked improvement. However, all medial femoral condyle graft group patients reported knee pain that persisted about 6 weeks postoperatively. (Level III evidence)

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