Vascularized Small-Bone Transfers for Fracture Nonunion and Bony Defects

Vascularized small-bone grafting is an efficient and often necessary surgical approach for nonunion or necrosis of several bones in particular sites of the body, including scaphoid, lunate, distal ulna, and clavicle. The medial femoral condyle is an excellent graft source that can be used in treating scaphoid, ulna, clavicle, or lower-extremity bone defects, including nonunion. Vascularized bone grafting to the small bones, particularly involving reconstruction of damaged cartilage surfaces, should enhance subchondral vascular supply and help prevent cartilage regeneration. Vascularized osteoperiosteal and corticoperiosteal flaps are useful for treating nonunion of long bones.

Key points

  • Vascularized small-bone grafting is an efficient and often necessary surgical approach for nonunion or necrosis of several bones in particular sites of the body, including scaphoid, lunate, distal ulna, and clavicle.

  • The medial femoral condyle is an excellent graft source that can be used in treating scaphoid, ulna, clavicle, or lower-extremity bone defects, including nonunion.

  • Vascularized bone grafting to the small bones, particularly involving reconstruction of damaged cartilage surfaces, should enhance subchondral vascular supply and help prevent cartilage regeneration.

  • Pedicle distal radial bone grafting is still a viable option as a technically easier way to treat scaphoid nonunion or revascularization of Kienböck disease.

  • Vascularized osteoperiosteal and corticoperiosteal flaps are useful for treating nonunion of long bones.

Introduction

Vascularized bone grafting has frequently been used in reconstruction of long-bone defects, because vascular supply to the graft will ensure better healing to the defect size. Vascularized bone grafting for small-bone defects or nonunion is necessary only in some special clinical conditions, such as nonunion of scaphoid fractures, or defects in small bones such as clavicles, radius or ulna, facial bones, and tarsal bones in the foot.

The sources of such bone grafts vary. Typically, vascularized iliac bone grafting has been used as a free transfer to many parts of the body, and pedicled bone chips taken from the distal radius have been used in the hand and wrist. The medial femoral condyle (MFC) has emerged more recently as one of the most versatile donor sites in the treatment of challenging bone reconstruction. This graft donor site, described by Sakai and colleagues in 1991, has recently gained popularity thanks to the work of Burger, Higgins, and others. The current application of small-bone grafting in 3 units in 3 countries, China, Italy, and Austria, are summarized in later discussion. The indications and applications of small-bone grafting in the 3 units are summarized in Table 1 .

Table 1
The current application of vascularized small-bone grafting in 3 units in China, Italy, and Austria
Nantong, China Florence, Italy Innsbruck, Austria
Free MFC graft Scaphoid Scaphoid Scaphoid
Ulna Ulna Tibia
Clavicle Clavicle Metacarpal
Lunate (advanced Kienböck) Navicular bone
Free iliac bone graft Scaphoid
Lunate (advanced Kienböck)
Distal radial graft a Scaphoid
Lunate (Kienbock)

a A graft based on a pedicle of the 1,2 or 2,3 intercompartmental arteries (ICSRAs) for nonunion of the scaphoid or the fourth and fifth ICSRA for Kienbock disease.

Introduction

Vascularized bone grafting has frequently been used in reconstruction of long-bone defects, because vascular supply to the graft will ensure better healing to the defect size. Vascularized bone grafting for small-bone defects or nonunion is necessary only in some special clinical conditions, such as nonunion of scaphoid fractures, or defects in small bones such as clavicles, radius or ulna, facial bones, and tarsal bones in the foot.

The sources of such bone grafts vary. Typically, vascularized iliac bone grafting has been used as a free transfer to many parts of the body, and pedicled bone chips taken from the distal radius have been used in the hand and wrist. The medial femoral condyle (MFC) has emerged more recently as one of the most versatile donor sites in the treatment of challenging bone reconstruction. This graft donor site, described by Sakai and colleagues in 1991, has recently gained popularity thanks to the work of Burger, Higgins, and others. The current application of small-bone grafting in 3 units in 3 countries, China, Italy, and Austria, are summarized in later discussion. The indications and applications of small-bone grafting in the 3 units are summarized in Table 1 .

Table 1
The current application of vascularized small-bone grafting in 3 units in China, Italy, and Austria
Nantong, China Florence, Italy Innsbruck, Austria
Free MFC graft Scaphoid Scaphoid Scaphoid
Ulna Ulna Tibia
Clavicle Clavicle Metacarpal
Lunate (advanced Kienböck) Navicular bone
Free iliac bone graft Scaphoid
Lunate (advanced Kienböck)
Distal radial graft a Scaphoid
Lunate (Kienbock)

a A graft based on a pedicle of the 1,2 or 2,3 intercompartmental arteries (ICSRAs) for nonunion of the scaphoid or the fourth and fifth ICSRA for Kienbock disease.

Medial femoral condyle as a graft donor in reconstruction of small-bone defects

Originally described as a periosteal or corticoperiosteal flap based on the descending genicular artery (DGA), this flap has evolved into a more structural graft including a variable amount of cancellous bone and finally into an osteochondral graft, including a small amount of the articular cartilage of the MFC. From a structural point of view, this graft belongs to the family of flat bone flaps, such as the scapula and, more importantly, the iliac crest, and is therefore indicated in reconstructions of small defects that for some reason require vascularized bone.

Maxillofacial surgery and hand surgery are the 2 main fields of application of the procedure to a variety of conditions; nonunions, tumors, and infections are the most common abnormalities that benefit from an MFC graft. This flap provides a very well-vascularized bone block and a thick periosteum that may be significantly larger than the bone flap in order to overlap the junction with the host bone, improving the blood supply and the ability to heal. In addition, in the case of intraoral location of the flap, the periosteum is quickly colonized by the neighboring mucosa, providing optimal and fast integration with the surrounding tissues.

In the upper limbs, recalcitrant nonunion of the forearm bones and clavicle, scaphoid nonunion, necrosis of the proximal pole of the scaphoid, and Kienböck disease have been the pathologic conditions most frequently treated by an MFC graft. More recently, this graft has been successfully used in metacarpal and phalangeal reconstruction as well as tarsal reconstruction.

An MFC graft is actually a very versatile graft. In addition, the donor site morbidity is inconspicuous, and the harvesting technique is relatively straightforward.

Surgical Anatomy and Harvesting Technique

The surgical anatomy and the harvesting technique have been described in detail by several authors, who progressively refined the anatomic knowledge of the region and added many technical details to the procedure.

This flap is based on the DGA system. The DGA rises from the superficial femoral artery and runs distally, deep and posterior to the vastus medialis muscle. Usually it bifurcates 0.7 cm distal to its origin in 2 branches: the saphenous artery, which supplies the skin of the medial aspect of the knee, and a terminal, periosteal branch that supplies a rich periosteal network on the medial condyle. In this typical vascular configuration, the pedicle of a medial condyle flap may be up to 8 cm long. However, in about 30% of cases, the periosteal branch of the DGA is extremely small or even absent. In those circumstances, the superior medial genicular artery, a short vessel that arises directly from the popliteal artery, is the main contributor to the periosteal network and the pedicle of such a flap.

The patient is placed supine with hips extrarotated and abducted, and the knee flexed at 80°. A sterile tourniquet is suggested but not mandatory. A longitudinal incision is placed over the projection of the posterior margin of the vastus medialis muscle and extended over the MFC. The DGA may be visualized close to the femur and to the posteromedial aspect of the vastus medialis muscle. After dedicating some branches to the muscle and its tendon, the artery supplies a rich periosteal plexus on the MFC together with the superior medial genicular artery ( Fig. 1 ). The flap may be tailored in a variety of forms according to the specific need of the recipient area. It may be constituted only of periosteum and a thin layer of cortex, but it can be also a vascularized corticocancellous bone graft if a block of cancellous bone is included in the harvest. Finally, it may be an osteochondral graft when a small portion of cartilage is harvested ( Fig. 2 ). The donor site morbidity is negligible, and according to Higgins and colleagues, a graft up to 7 cm long may be safely harvested.

Fig. 1
The DGA and the periosteal vascular network on the MFC.

Fig. 2
( A ) MFC may be harvested including periosteum and a thin layer of cortex only ( A ), or as a bone block including cancellous bone ( B ). The osteochondral graft includes a small portion of cartilage ( C ).

Applications to Different Sites of the Body

Applications of this flap to different parts of the body are illustrated in later discussion through a few cases in Plastic Surgery, University of Florence Careggi University Hospital, Florence, Italy.

Reconstruction of defects in ulna

A 45-year-old man suffered an open fracture of the radius and ulna of the left forearm. A nonunion of the ulna fracture was initially treated by conventional corticocancellous bone graft from the iliac crest. The graft united with the proximal stump of the recipient bone, but a nonunion recurred distally ( Fig. 3 A ). An MFC corticoperiosteal flap was harvested from the contralateral knee, based on the DGA. Some parallel slots were made by saw on the inner surface of the graft ( Fig. 3 B) in order to make it foldable ( Fig. 3 C) and wrap it around the site of nonunion. The plate was stable and therefore left in place. There was radiologic evidence of successful union 3 months after surgery ( Fig. 3 D).

Fig. 3
( A ) Atrophic nonunion at the distal junction of a conventional corticocancellous bone graft in the ulna. ( B ) Parallel slots were made by saw on the inner surface of the graft in order to interrupt the cortex. ( C ) Subsequently, the flap was wrapped around the bone defect. ( D ) Bone healing 3 months postoperatively.

Clavicle reconstruction

A 52-year-old woman suffered an unstable nonunion after conservative treatment of a fracture of the left clavicle. Two attempts at reconstruction by means of autologous corticocancellous bone from the iliac crest failed over the following 3 years. When the patient was referred to the authors, radiographs showed atrophic nonunion of the clavicle. Movement at the glenohumeral joint was limited and painful. A reconstruction by means of corticocancellous MFC was performed, and a new locking compression plate was used to stabilize the graft ( Fig. 4 A ). The vascular pedicle was anastomosed to the thoracoacromial artery and vein. At 4 month follow-up, the patient was pain free and had recovered functional range of motion (ROM) at the affected shoulder. Radiographs showed union of the graft on both sides 6 months after surgery ( Fig. 4 B).

Fig. 4
A patient with nonunion of the left clavicle after several attempts of reconstruction with nonvascularized bone graft. ( A ) Preplating of the MFC with a locking compression plate. ( B ) Bone healing at 4 months.

Navicular bone reconstruction

A 63-year-old man underwent multiple attempts at reconstruction of the navicular bone of the right foot after traumatic loss of the bone. The last one was an implant of a synthetic spacer, which totally failed in providing stability to the mid foot ( Fig. 5 A ). The patient was not able to load on the foot and needed crutches to walk. After removal of the spacer ( Fig. 5 B) and aggressive debridement of the defect, the authors used a free medial condyle flap to achieve a stable fusion of the mid foot. The graft was harvested as a bone block with a redundant periosteal flap and tailored according to a wax template corresponding to the tridimensional defect ( Fig. 5 C). The oversize periosteal flap was able to overlap the junction with the tarsal bones and the graft stabilized with a single screw ( Fig. 5 D). An end-to-end anastomosis was performed with the anterior tibial artery. Full and pain-free weight-bearing was possible 3 months after surgery.

Fig. 5
( A ) Navicular bone loss. ( B ) The removal of a synthetic spacer previously implanted after traumatic navicular bone loss. ( C ) The MFC is tailored according to a 3-dimensional template of the defect. ( D ) The bone healing at 3 months.

Practical Tips and Comments on the Medial Femoral Condyle Transfer

The MFC probably represents the most useful innovation in vascularized bone grafts. Over its direct competitor, the iliac crest, MFC has shown several advantages in clinical practice, including the low morbidity at the donor site and easy dissection and possibility to customize the graft according to the defect. However, a drawback of the procedure is some anatomic variability of the pedicle, because in about 30% of cases the feeding pedicle is the superior medial genicular artery, which is quite short.

Current indications for MFC grafting are “difficult” small defects that need vascularized bone such as nonunions of the clavicle or the bones of forearm, hand, and foot and situations in maxillofacial surgery that depend on the ability of the thick periosteum to be colonized by the oral mucosa. Finally, the osteochondral version of the flap has opened up new perspectives in the reconstruction of the proximal pole of scaphoid and lunate.

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Nov 21, 2017 | Posted by in Dental Materials | Comments Off on Vascularized Small-Bone Transfers for Fracture Nonunion and Bony Defects
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