Flap physiology, classification, and applications

Muscle and musculocutaneous flaps

In 1981, Mathes and Nahai described a classification system for muscles based on the following anatomic relationships between the muscle and its vascular pedicles:

• 1.

  The regional source of the pedicle entering the muscle

• 2.

  The number and size of the pedicle

• 3.

  The location of the pedicle with respect to the muscle's origin and insertion

• 4.

  The angiographic patterns of the intramuscular vessels.

This classification system enables the surgeon to categorize the various muscle and musculocutaneous flaps into distinctly different, clinically applicable groups based on the vascular anatomy. There are five different vascular patterns by which the various muscles are categorized ( Fig. 24.7 ).

• Type I: one vascular pedicle – type I muscles are supplied by a single vascular pedicle ( Box 24.2 ).

  BOX 24.2

  Type I vascular pattern muscles

  • Abductor digiti minimi (hand)

  • Abductor pollicis brevis

  • Anconeus

  • Colon

  • Deep circumflex iliac artery

  • First dorsal interosseous

  • Gastrocnemius, medial and lateral

  • Genioglossus

  • Hyoglossus

  • Jejunum

  • Longitudinalis linguae

  • Styloglossus

  • Tensor fascia lata

  • Transversus and verticalis linguae

  • Vastus lateralis

• Type II: dominant vascular pedicle and minor pedicle – type II muscles are supplied by both a dominant and minor vascular pedicle. The larger dominant vascular pedicle will usually sustain circulation to these muscles after the elevation of the flap when the minor pedicles are divided. This is the most common pattern of circulation observed in human muscle ( Box 24.3 ).

  BOX 24.3

  Type II vascular pattern muscles

  • Abductor digiti minimi (foot)

  • Abductor hallucis

  • Brachioradialis

  • Coracobrachialis

  • Flexor carpi ulnaris

  • Flexor digitorum brevis

  • Gracilis

  • Hamstring (biceps femoris)

  • Peroneus brevis

  • Peroneus longus

  • Platysma

  • Rectus femoris

  • Soleus

  • Sternocleidomastoid

  • Trapezius

  • Triceps

  • Vastus medialis

• Type III: two dominant pedicles – type III muscles possess two large vascular pedicles from separate vascular sources. These pedicles have either a separate regional source of circulation or are located on opposite sides of the muscle. Division of one pedicle during flap elevation rarely results in loss of muscle within its vascular distribution. The muscle will usually survive on one of its two dominant vascular pedicles. This vascular pattern allows the muscle to be split, allowing the use of only part of the muscle as a muscle or musculocutaneous flap ( Box 24.4 ).

  BOX 24.4

  Type III vascular pattern muscles

  • Gluteus maximus

  • Intercostal

  • Omentum

  • Orbicularis oris

  • Pectoralis minor

  • Rectus abdominis

  • Serratus anterior

  • Temporalis

• Type IV: segmental vascular pedicles – type IV muscles are supplied by segmental vascular pedicles entering along the course of the muscle belly. Each pedicle provides circulation to a segment of the muscle. Division of more than two or three of the pedicles during elevation as a flap may result in distal muscle necrosis ( Box 24.5 ).

  BOX 24.5

  Type IV vascular pattern muscles

  • Extensor digitorum longus

  • Extensor hallucis longus

  • External oblique

  • Flexor digitorum longus

  • Flexor hallucis longus

  • Sartorius

  • Tibialis anterior

• Type V: one dominant vascular pedicle and secondary segmental vascular pedicles – type V muscles are supplied by a single dominant pedicle and secondary segmental vascular pedicles. These muscles have one large dominant vascular pedicle near the insertion of the muscle with several segmental pedicles near the origin. The internal vasculature can be supplied by either the dominant or the segmental pedicles, and therefore the muscle may be elevated as a flap on either vascular system ( Box 24.6 ).

  BOX 24.6

  Type V vascular pattern muscles

  • Fibula

  • Internal oblique

  • Latissimus dorsi

  • Pectoralis major

When a flap is used based on the pedicle as a local or an island flap, the dominant vascular pedicle to the flap is preserved. A factor that may prevent successful flap transposition is the flap's arc of rotation. The arc of rotation of a muscle is determined by the extent of elevation of the muscle from its anatomic bed and the ability of the muscle to reach adjacent areas without devascularization. The mobility of a muscle depends on the number of vascular pedicles and the location of the dominant vascular pedicle relative to the muscle's origin and insertion ( Fig. 24.8 ). The area covered by the arc of rotation varies among individuals. On the basis of the flap length distal to the point of rotation and the length of the vascular pedicle, a safe standard arc of rotation is measured for each flap. A modified arc of rotation is also available based on refinements in design and specific modifications of the flap. Precise knowledge of the safe standard and modified arc of rotation is necessary to avoid loss of the flap from excessive tension or damage to the pedicle from overzealous dissection.

In general, the arc of rotation is inversely proportional to the number of vascular pedicles. If a muscle has a large number of pedicles, it usually has a limited arc of rotation. Type IV muscles, such as the sartorius and tibialis anterior, are examples of muscles with multiple segmental vascular pedicles and limited arcs of rotation. Similarly, the location of the dominant vascular pedicle relative to the muscle's origin and insertion greatly determines the arc of rotation. The closer the dominant vascular pedicle is to either the origin or the insertion of the muscle, the greater the arc of rotation. The point of rotation for types I, II, III, and V muscles generally are located at one end or the proximal third of the muscle. For example, type V muscles, such as the pectoralis major and latissimus dorsi, have their major vascular pedicle near their insertion, and correspondingly have a wide arc of rotation. Certain muscles, such as type V muscles, have two arcs of rotation. The first arc of rotation is based on the dominant blood supply, while the second arc is based on the secondary segmental vascular pedicles. Reverse arc of rotation refers to the degree of transposition of a flap based on its secondary segmental vascular pedicles.

A muscle can be split and a portion in continuity with the dominant vascular pedicle can be used as a transposition flap using just a segment of the muscle. Techniques of muscle splitting to preserve tissue and function have been described. The remaining muscle with its origin and insertion is maintained to preserve function. Alternatively, the entire muscle may be split and used to cover two defects simultaneously. Frequently, only a part of the muscle in proximity to the dominant vascular pedicle is elevated for microvascular transplantation. The skin territory may also be modified and split into two separate skin islands or elevated with only a segment of the muscle flap. However, the skin territory must include vascular connections via musculocutaneous perforating vessels from the segmental flap ( Figs. 24.9 & 24.10 ).

The basis for splitting the pectoralis major muscle was demonstrated by Tobin in 1985. The pectoralis has three segmental neurovascular subunits: the clavicular, the sternocostal, and the external subunit. These can be surgically split and independently transferred on vascular pedicles from the thoracoacromial, internal mammary, and lateral thoracic vessels. Splitting of the pectoralis major muscle into segments has been performed when the segmental transfer of a single intercostal portion of the pectoralis muscle, based on a single medial perforating branch of the internal thoracic artery, is required for chest wall and neck reconstruction ( Figs. 24.11 & 24.12 ). The concept of segmental transposition of muscle allows for the transplantation of independent neuromuscular units (segments of muscle innervated by a single nerve fascicle).

Selection of the most appropriate reconstructive method can be difficult. Careful consideration must be given to all the possible methods of repair, and the advantages and disadvantages of each technique must be weighed accordingly.

The advantages of muscle or musculocutaneous flaps include the following:

• 1.

  The vascular pedicles are specific and reliable.

• 2.

  The vascular pedicle is often located outside the surgical defect, which can be particularly important for wounds with an extensive zone of injury beyond the actual wound (e.g., after irradiation, trauma).

• 3.

  The muscle provides bulk for deep, extensive defects and protective padding for exposed vital structures (e.g., tendons, nerves, vessels, bones, and prostheses).

• 4.

  Muscle is malleable and can be manipulated (e.g., folded on itself) to produce a desired shape or volume.

• 5.

  Well-vascularized muscle is resistant to bacterial inoculation and infection.

• 6.

  Reconstruction by use of muscle or musculocutaneous flaps is often a one-stage procedure.

• 7.

  Restoration of function, whether motor or sensory, is possible with certain flaps.

• 8.

  The reliability and availability of muscle and musculocutaneous flaps make them an excellent alternative means of reconstruction when the closure method of choice for a particular defect is unavailable or inadequate.

The disadvantages of muscle and musculocutaneous flaps include the following:

• 1.

  The donor defect may lose some degree of function.

• 2.

  The donor defect may be aesthetically undesirable.

• 3.

  Reconstruction with muscle or musculocutaneous flaps may provide excessive bulk, leaving an aesthetically unacceptable result.

• 4.

  Muscle or musculocutaneous flaps may atrophy over time and thus fail to provide adequate coverage.

• 5.

  Removal of the muscle or musculocutaneous flap may result in contour deformities at the donor site.

The preservation of function can be extremely important when nonexpendable muscles are used as flaps. The techniques of function preservation generally involve transposing part of the muscle without completely interrupting the origin or insertion of the donor muscle. For example, the transposition of the superior half of the gluteus maximus muscle for sacral coverage in the ambulatory patient can be performed without loss of thigh extension or hip stability because the remainder of the gluteus maximus is functionally intact.

Fascia and fasciocutaneous flaps

A growing knowledge of the source of skin circulation after the recognition of the muscle and musculocutaneous system led to the identification of vascular pedicles emerging between muscles (septocutaneous pedicles) and entering the deep fascia. Elevation of the skin with its deep fascia represented a new vascular basis for flap design.

A fascial flap consists of fascia detached from its normal origin or insertion and transposed to another location. Without the overlying skin and fat, this represents a delicate flap. A fasciocutaneous flap, originally called an axial flap, includes the skin, subcutaneous tissue, and underlying fascia, which may be distinct from the fascia covering the underlying muscle. The vascular supply is derived at the base of the flap from musculocutaneous perforators or direct septocutaneous branches of major arteries.

The first fascia and fasciocutaneous flaps were described by Pontén in 1981 for lower extremity reconstruction and Tolhurst in 1983 for trunk and axillary reconstruction. Investigations have shown that the fasciocutaneous system consists of perforating vessels that arise from regional arteries and pass along the fibrous septa between muscle bellies or muscle compartments. The vessels then spread out at the level of the deep fascia, both above and below, to form plexuses, which in turn give off branches to the skin. In 1975, Schafer found three major vascular systems of the deep fascia:

• 1.

  Perforating arteries from underlying muscle giving off several radiating branches, which perforate the fascia before continuing to the subdermal plexus

• 2.

  Subcutaneous arteries running in the fat and anastomosing frequently with the superficial plexus of the deep fascia and with each other

• 3.

  Subfascial arteries arising from the intermuscular septa and running in the loose areolar tissue beneath the deep fascia and adjoining the deep and superficial plexus.

These pedicles consist of an artery (generally a branch of the artery to the specific anatomic region of the fascia and regional musculature) and paired venae comitantes that drain into corresponding major regional veins. Direct cutaneous and septocutaneous pedicles are fairly constant in location. There is a greater variability in location of the musculocutaneous perforators. These pedicles provide a vascular basis for specific fascial or fasciocutaneous flaps. On this basis, Mathes and Nahai have classified fascia and fasciocutaneous flaps as types A, B, and C ( Fig. 24.13 ).

Anatomic studies demonstrate that type A fasciocutaneous flaps have a vascular pedicle to the deep fascia that emerges from a regional source coursing initially beneath the deep fascia and eventually continuing its course superficial to the deep fascia. This pedicle provides numerous fasciocutaneous perforators to the skin. Because the pedicle tends to course in a radial fashion from its regional source into its distal cutaneous distribution, the flap is often referred to as an axial flap. The long, relatively superficial course of the dominant pedicle permits evaluation by palpation or Doppler probe ( Box 24.7 ).

Type B fasciocutaneous flaps have a septocutaneous pedicle, which courses between major muscle groups in an intermuscular septum or between adjacent muscles. This pedicle is located within the intermuscular septum or the potential space between adjacent muscles and supplies a regional fascial vascular system. The largest septocutaneous pedicles are dominant pedicles to specific fasciocutaneous flaps and are fairly constant in location ( Box 24.8 ).

In certain regions, larger musculocutaneous perforators enter the deep fascia and contribute to both the deep fascia and cutaneous circulation. The design of a fasciocutaneous flap can be based on these dominant perforating vessels without incorporation of the underlying muscle; this vascular pattern represents the type C fasciocutaneous flap. However, increasing pedicle length will necessitate proximal dissection of the pedicle through muscle to its regional source or incorporation of all or part of the muscle in the flap design. Type C flaps are generally the anatomic model used for the perforator flap in microsurgical transplantation ( Box 24.9 ).

Cormack and Lamberty also classified fasciocutaneous flaps based on vascular anatomy. The type A flap is supplied by multiple fasciocutaneous perforators that enter at the base of the flap and extend throughout the longitudinal length. The flap can be based proximally, distally, or as an island. The type B flap has a single fasciocutaneous perforator, which is of moderate size and is fairly consistent. It is intended for use as a free flap. The type C flap is based on multiple small perforators that run along a fascial septum. The supplying artery is included within the flap. It may be based proximally, distally, or as a free flap. The type D flap is an osteomusculofasciocutaneous flap, and is based on multiple small perforators similar to the type C flap, but also includes a portion of adjacent muscle and bone. It may be based proximally or distally on a pedicle or used for microvascular tissue transplantation ( Fig. 24.14 ).

Nakajima et al . expanded the types of fasciocutaneous flaps and described them originating from six different types of perforators piercing the deep fascia feeding to the plexus of the skin ( Fig. 24.15 ). Type A, direct cutaneous branch of muscular vessel was described in the same manner as axial pattern flaps of McGregor and Morgan. Type B, septocutaneous perforator was the same as type B from the classification of Cormack and Lamberty. Type C, direct cutaneous branch, and type D, musculocutaneous perforator supplying the fasciocutaneous flap, were not quite described in previous classifications. These types, especially type D from the Nakajima et al . classification, further play a pivotal role for setting up the concept of true perforator flaps. Type E, direct septocutaneous, describes type C from the classification of Cormack and Lamberty and type F, perforating cutaneous branch of muscular vessel resembles traditional musculocutaneous flaps.

The fasciocutaneous flap is used as a local flap, the standard arc of rotation is determined by the extent of elevation of the deep fascia from its normal anatomic position to reach adjacent defects. The point of rotation is based on the site of entrance of the dominant vascular pedicle into the fascia. The fascia or fasciocutaneous flap is elevated to the point of entrance of the flap pedicle, and the fascia and overlying skin distal to this point are rotated into the defect.

The advantages and disadvantages of these flaps are somewhat similar to those of muscle flaps, although there are a few exceptions. The advantages include the following:

• 1.

  They are thin and pliable.

• 2.

  The blood supply is reliable and robust.

• 3.

  The donor site morbidity is minimal in regard to function.

• 4.

  They are muscle sparing.

• 5.

  They have the ability to restore sensation.

• 6.

  There are many potential donor sites.

The disadvantages of fascia, fasciocutaneous, and perforator flaps include the following:

• 1.

  There is a lack of bulk for deep defects.

• 2.

  They are technically more challenging (pedicle dissection; many require microvascular anastomosis or at least microvascular techniques).

• 3.

  There are size limitations.

• 4.

  The arc of rotation is sometimes limited though often better than the similar muscle flap because of the longer pedicle.

• 5.

  Donor site may require skin graft closure, resulting in donor site deformity.

Perforator flap (skin with fat and with or without fascia)

Further refinements in flap application have led to the development of perforator flaps. Perforator flaps have evolved from musculocutaneous and fasciocutaneous flaps without the muscle or fascial carrier. It was a natural evolution as reconstruction needed fine-tuning while aiming to minimize donor morbidities. A good example of this evolution would be the change from transverse rectus abdominis muscle (TRAM) flaps to muscle-sparing TRAM to deep inferior epigastic perforator (DIEP) flaps ( Fig. 24.16 ). Transformation of these flaps has shown that neither a passive muscle carrier nor the underlying fascial plexus of vessels are necessary for flap survival. Thus, a perforator flap is a skin flap (with or without fascia) based on a single perforator. Like the angiosome concept showing the vascular territory of a source vessel, one must understand the anatomy and physiology of a single perforator territory to obtain the ideal design of the perforator flap. The perforasome theory by Saint-Cyr reported four major characteristics of a perforator flap: (1) each perforasome is linked with adjacent perforasomes by means of direct and indirect linking vessels ( Fig. 24.17 ); (2) flap design and skin paddle orientation should be based on the direction of the linking vessels, which is axial in the extremities and perpendicular to the midline in the trunk ( Fig. 24.18 ); (3) filling of the perforasomes occurs within perforasomes of the same source artery first followed by perforators of the other adjacent source arteries; (4) mass vascularity of a perforator found adjacent to an articulation is directed away from that same articulation ( Fig. 24.19 ). This theory provides insights into perforator flap vascularity and can clinically guide to the harvest of a safer free or pedicle perforator flap.

In 1989 Koshima and Soeda used the term “perforator flaps” in their harvest for paraumbilical skin and fat island flaps based on a muscular perforator. Since then, perforator-based flaps using lower abdomen skin flaps have been applied for breast reconstruction. Slowly other perforator-based flaps have been introduced from various parts of the skin.

The nomenclature of perforator flaps is confusing and oftentimes misstated. Perforator flaps have been designated by their location (e.g., anterolateral thigh flap), arterial supply (e.g., deep inferior epigastric artery perforator flap), or the muscle of origin (e.g., gastrocnemius perforator flap). Thus, a clear definition and classification for perforator flaps was needed. Hallock defines a perforator as any vessel that pierces through the fenestration in the deep fascia regardless of origin. In a consensus document for perforator flap terminology, perforators that pierce through the deep fascia without traversing any other structural tissues were called direct perforators while indirect perforators run through deeper structures such as muscles, septum and perimysium. Evolved from the six patterns of fascial perforators of Nakajima et al ., the consensus paper simplified it into five types of perforator based on the surgical approach for dissection of the perforators ( Fig. 24.20 ). Type 1: direct perfor­ators perforate the deep fascia only; type 2: indirect muscle perforators predominantly supply the subcutaneous tissues; type 3: indirect muscle perforators predominantly supply the muscle but have secondary branches to the subcutaneous tissues; type 4: indirect perimysial perforators travel within the perimysium between muscle fiber before piercing the deep fascia; type 5: indirect septal perforators travel through the intermuscular septum before piercing the deep fascia. Based on this distinction of different perforators, the consensus paper gives definitions and classification for perforator flaps as follows:

• Definition 1 : A perforator flap is a flap consisting of skin and/or subcutaneous fat. The vessels that supply the blood to the flap are isolated perforator(s). These perforators may pass either through or in between deep tissues (mostly muscle).

• Definition 2 : A muscle perforator is a blood vessel that traverses through septum to supply the overlying skin.

• Definition 3 : A septal perforator is a blood vessel that traverses only through septum to supply the overlying skin.

• Definition 4 : A flap that is vascularized by a muscle perforator is called a muscle perforator flap.

• Definition 5 : A flap vascularized by a septal perforator is called a septal perforator flap.

• Definition 6 : A perforator flap should be named after the nutrient artery or vessels and not after the underlying muscle. If there is a potential to harvest multiple perforator flaps from one vessel, the name of each flap should be based on its anatomical region or muscle.

This terminology and the classification into indirect and direct perforator flaps and further into septal and muscle perforator flaps were set up to clearly identify the course of these small terminal branches before they pierce the deep fascia and the technical implications during the surgical procedure. Table 24.2 shows some of the popular perforator flaps based on this terminology. Recent innovations in this field have made some of the terminology and classification somewhat misleading. As with all evolution, new classification and terminology will be constantly updated.

One of the recent evolutions in perforator flaps has been in producing thinner flaps. Although post-reconstruction debulking achieves pleasing aesthetic results and is widely practiced, customized approach during elevation to achieve the ideal thickness will increase efficiency while achieving the best possible aesthetic outcome in accordance with the elevator reconstruction concept. Multiple planes for elevation have been reported along with different techniques. To date, the elevation layers can be categorized into five planes; subfascial (immediately under and including the deep fascia same as fasciocutaneous structure), suprafascial (immediately above and excluding the deep fascia), superficial fascia (also termed superthin, on the fascia-like film layer between the deep and the superficial fat), fascia-like plane within the superficial fat (also termed ultrathin) and the subdermal plane (also known as the pure skin perforator flap) ( Fig. 24.21 ). These planes all have their unique properties and challenges and the surgeon should understand the anatomy, technical aspect, and possible pitfalls to safely elevate the perforator flaps on these different planes.

When selecting the perforator flap as a free flap, multiple factors can be considered. A recent algorithm for perforator flap selection recommends to consider the patient position on the surgical table, flap size needed for coverage, thickness of the perforator flap, composition of the flap and the pedicle length required to sufficiently reach the recipient vessel. This approach can help to optimize form and function, decrease operative time, while minimizing donor site morbidity and secondary procedures.

The perforator flap concept simplified and overcame the applications and limits of classic local flaps. By identifying the perforator as the pedicle and further dissecting toward the source vessel, it allowed improved movement and better survival of flap. One form of perforator-based local flap, the propeller flap, is an island flap that reaches the recipient site through an axial rotation. When a perforator propeller flap is being elevated, the perforator is dissected free from the fascial and fat adhesions to minimize the chance of kinking. Although less rotation reduces the chance for kinking, the skin island may be safely rotated up to 180° ( Fig. 24.22 ).

Advantages of perforator flaps include:

• 1.

  Reduced donor site morbidity

• 2.

  Versatility in flap design

• 3.

  Muscle sparing (less functional deficit)

• 4.

  Improved postoperative recovery of the patient.

Disadvantages of perforator flaps may include:

• 1.

  Meticulous dissection needed to isolate the perforator vessels

• 2.

  Increased operative time, especially in muscle perforators

• 3.

  The variability in the position and size of the perforator vessels

• 4.

  Steep learning curve.

However, modifications such as the free-style approach and supermicrosurgery have further simplified the approach and increased the use of perforator flaps. The free-style approach identifies the perforator feeding the skin flap first and then dissects proximally toward the source vessel contrary to the classic approach where identification of the source vessel was made first and then dissection toward the perforator. This allows the freedom to design flaps based on any perforator as well as alleviate the risk for pedicle variation. The supermicrosurgery approach, perforator to perforator anastomosis, allows harvesting the flap as a short pedicled flap, reducing the dissection time and minimizing the risk for traumatizing the pedicle during dissection.

Visceral flaps

The abdominal viscera are not easily classified; however, for the purposes of flap transposition or microvascular tissue transplantation, the colon, jejunum, and omentum fall conveniently into the muscle classification system ( Table 24.3 ). For microvascular transplantation, the segment of bowel (jejunum or colon) is elevated on one vascular arcade with a single dominant vessel, a type I pattern of circulation. In unusual circumstances where a longer segment of bowel extends beyond the vascular territory of one arcade, two vascular arcades must be included to ensure viability of this longer segment of bowel. In this instance, the pattern of circulation will be type III (two dominant arcades or pedicles). It is possible to reconstruct the esophagus from the base of the tongue to the stomach with a long segment of jejunum where one pedicle is revascularized in the upper chest or neck and the second pedicle is left intact. Additional uses of the colon or jejunum as flaps have been for vaginal reconstruction. The appendix, as a type I pattern based on the appendiceal artery and vein, has been used for reconstructing the urethra and for voice reconstruction.

The omentum may be based as a transposition flap on either the right or left gastroepiploic vessels and is thus classified as having a type III pattern of circulation. The omentum is also commonly transferred microsurgically. The omentum can be used to reconstruct a wide range of extraperitoneal defects and has been shown to have immunologic and angiogenic properties. Although useful for reconstruction, donor site complications can be significant, including abdominal wall infection and hernia. With the advances in minimally invasive surgery, the abdominal viscera can successfully be harvested laparoscopically obviating the need for a large midline incision providing a better cosmetic result and less donor site morbidity.

Bone flap (vascularized bone, osseous–periosteal flap)

Bone is vascularized through endosteal and periosteal sources ( Fig. 24.23 ). The complex blood supply of bone is based on nutrient vessels entering the bone directly and through vascular connections between muscles and bone, typically where the muscle has a large bony origin or insertion. Vascularized bone is useful in muscles suitable for microvascular transplantation or in those muscles designed for transposition when the vascular attachments to bone are distal to the point of rotation. The commonly transferred bones include the fibula based on the peroneal artery, iliac crest based on the deep circumflex iliac artery ( Fig. 24.24 ), the scapula based on the circumflex scapula or thoracodorsal arteries ( Fig. 24.25 ), and the radius based on the radial artery ( Fig. 24.26 ). The calvarial osseous flap based on the superficial temporal artery or occipital artery with partial- or full-thickness bone is also useful for reconstructing facial anomalies and deformities ( Fig. 24.27 ). The use of periosteum and part of the cortical bone as an osseous–periosteal flap is being widely used for non-union of the bone and small bone defects. The genicular osseous–periosteal flap, also known as the medial femoral condyle flap, based on the articular branch of the descending genicular artery and vein with periosteum and a thin (0.5–1.0 mm) layer of outer cortical bone, was first reported by Sakai et al . to treat fracture non-union ( Fig. 24.28 ). Further applications of this flap with or without skin and cartilage expanded to reconstructing small bone defects, avascular necrosis of the bone and other complex defects of the hand.

There is no widely accepted classification of bone flaps alone. Perhaps it is due to the complexity of the vasculature to each bone. One of the most widely used, the fibula, has vascular supply from the branches of the anterior tibial artery supplying the head, neck, and epiphysis while the peroneal artery gives rise to multiple arcuate vessels along the fibula and a nutrient vessel in the mid third of the fibula bone ( Fig. 24.29 ). Thus, depending on the portion of the fibula bone being harvested, the pedicle of the bone flap can differ not only in anatomical region but also in type of vascular supply to the bone. The fibula bone flap with or without the skin (fasciocutaneous) flap is frequently used for segmental bone defects especially after mandibular resection, long bone resection, and for pelvis reconstruction (see Fig. 24.24 ). The fibular bone including the head and epiphyseal growth plate is used in patients who need further growth of the long bone such as reconstruction after sarcoma resection of the proximal humerus.