The scaphoid is the most commonly fractured carpal bone, accounting for between 60% and 70% of all carpal fractures. Approximately 80% of the surface of the scaphoid is covered by cartilage, which limits its ligamentous attachment and vascular supply. The majority of scaphoid fractures occur at the waist. Acute stable fractures or incomplete fractures of the scaphoid may be treated nonoperatively, resulting in a high rate of fracture union. Although closed treatment of stable fractures of the scaphoid is associated with a high rate of healing, this method requires prolonged cast immobilization, which may lead to muscle atrophy, possible joint contracture, disuse osteopenia, and potential financial hardship. Because of this, internal fixation of minimally displaced fractures of the scaphoid has become popular. There is a consensus that scaphoid nonunions and fractures of the proximal pole of the scaphoid should be treated operatively. What's hot in the management of scaphoid fractures is the development of percutaneous arthroscopic techniques of scaphoid stabilization that minimize surgical morbidity. In addition, what's hot in scaphoid fracture treatment is a significant improvement in the treatment of difficult scaphoid nonunions with use of vascularized bone grafts. What's not hot in scaphoid fracture treatment is prolonged immobilization for unstable fractures when surgical stabilization may have been the best option. This discussion will describe percutaneous, arthroscopic reduction, mini dorsal and open volar approaches to the scaphoid, and vascularized bone-grafting for resistant scaphoid fracture nonunions.
Prevalence of Scaphoid Fractures
The scaphoid is the most commonly fractured carpal bone and accounts for 60% to 70% of all carpal fractures. The majority of scaphoid fractures are relatively low-energy injuries and usually occur in young men.
Scaphoid Anatomy
The scaphoid bone is the only carpal bone that bridges both the proximal and distal rows, thereby being subjected to continuous shearing and bending forces. Approximately 80% of the surface of the scaphoid is covered by cartilage, which limits ligamentous attachments and vascular supply.
Gelberman and Menon studied the blood supply of the carpus in fifteen fresh cadaver specimens by injection techniques1. They found the primary blood supply to the scaphoid was from the radial artery. Seventy to eighty percent of interosseous vascularity in the entire proximal pole is from branches of the radial artery entering along the dorsal ridge of the scaphoid along the scaphoid waist. Because of the dependence of the scaphoid on a single dominant artery, the proximal pole is uniquely susceptible to osteonecrosis following injury.
The majority of scaphoid fractures occur at the waist as the result of wrist hyperextension to >95°. The wrist placed in extreme dorsiflexion and ulnar deviation produced fractures to the scaphoid waist as the scaphoid impinged on the dorsal rim of the radius2. Fractures of the proximal pole of the scaphoid were the result of dorsal subluxation during forced hyperextension2. Heinzelmann et al., using microcomputed tomography (micro CT), found that the scaphoid bone is most dense at the proximal pole where the trabecular bone is thickest and more tightly packed2. The trabeculae are thinnest and more sparsely distributed at the scaphoid waist, and this is where the majority of fractures occur.
Scaphoid Classifications
Scaphoid fractures have been classified by many methods, including stability, location of the fracture site, and fracture plane. Russe classified fractures of the scaphoid as horizontal oblique, transverse, and vertically oblique3. He noted that oblique fractures were unstable and were difficult to control with cast immobilization. Herbert and Fisher classified scaphoid fractures according to their stability4. Type-A fractures were considered stable and included incomplete fractures or fractures of the scaphoid tubercle. Type-B fractures were unstable acute fractures, with Type B1 being a distal oblique fracture; Type B2, a complete fracture at the waist; Type B3, a proximal pole fracture; and Type B4, a trans-scaphoid perilunate fracture dislocation. Type C fractures resulted in delayed union, and Type D fractures represented established nonunions, including Type D1 fibrous union and Type D2 pseudarthrosis. They noted that all other fractures except Type A were potentially unstable.
Cooney et al. further defined unstable fracture patterns5. These include fractures displaced >1 mm, a lateral intrascaphoid angle >35°, bone loss or comminution, perilunate-fracture dislocation, dorsal intercalated segmental instability (DISI) alignment, and proximal pole fractures.
Geissler and Slade published a radiographic classification of scaphoid nonunions (Table I)6.
Distal Pole Fractures
Distal pole fractures of the scaphoid are generally treated nonoperatively. The distal pole of the scaphoid is well vascularized, and distal pole fractures of the scaphoid have a high union rate after six to eight weeks of immobilization in a short arm cast. Distal pole fractures generally fall into two groups: Group I, avulsion fractures from the radial palmar lip of the scaphoid tuberosity; and Group II, impaction fractures of the radial half of the distal scaphoid articular surface. If displaced, these impacted fractures may need to be surgically stabilized.
Proximal Pole Fractures
Both displaced and nondisplaced fractures of the proximal pole are considered unstable and cannot be reliably treated nonoperatively because of their small fracture fragment size and tenuous blood supply. Because of the intra-articular location, synovial fluid can block fracture-healing, and the proximal location of the fracture leads to large lever-arm stress across the fracture site. Rettig and Raskin noted a 100% healing rate of seventeen proximal pole fractures treated acutely with screw fixation through a dorsal approach7.
Waist Fractures
Acute stable fractures or incomplete fractures of the scaphoid waist may be treated nonoperatively with a high rate of union (Table II). There is no agreement in the literature as to the position of mobilization or type of cast since truly stable fractures of the scaphoid may be treated by a variety of methods, including thumb spica cast, wrist extension cast, wrist neutral cast, and ulnar deviation cast, with nearly equivalent results. Historical literature suggests that the union rate after cast treatment approaches 85% to 95%. However, studies with radiographs made six to twelve months after injury or CT evaluation show lower rates of union. At a follow-up period of one year from injury, Terkelsen and Jepsen reported ten nonunions in ninety-two waist fractures that were treated with removable splints or long arm casts8.
Delaying treatment reduces the likelihood of union of stable scaphoid waist fractures. In a series of 285 scaphoid fractures, Langhoff and Andersen reported that, if fractures underwent treatment more than four weeks after injury, there was a substantially increased risk of delayed union or nonunion9. Up to 25% of scaphoid fractures are not visible on initial radiographs. Because failure to treat a stable scaphoid fracture for four weeks increases the nonunion rate, all clinically suspected scaphoid fractures should be treated as fractures, with the limb immobilized in a short arm cast, until the cause of symptoms is clarified. Follow-up radiographs with the cast removed are performed ten to fourteen days after the initial cast has been applied. Magnetic resonance imaging (MRI) is the most reliable modality to diagnose acute and occult fractures and is able to diagnose a scaphoid fracture within twenty-four hours of injury2.
While closed treatment of stable waist fractures of the scaphoid has a high rate of fracture union, prolonged cast immobilization may lead to muscle atrophy, joint contracture, disuse osteopenia, and potential financial hardship. Closed treatment of scaphoid waist fractures may require cast immobilization for three to six months. The economic cost of surgical versus nonsurgical treatment of stable scaphoid waist fractures has been well studied in the literature. Arora et al. compared two groups of patients with stable scaphoid fractures10. One group was treated with plaster immobilization and the other was treated with internal screw fixation. Internal screw fixation of nondisplaced scaphoid fractures was associated with a shorter time to osseous union, and patients returned to work an average of seven weeks earlier than those with cast immobilization. In this study, the cost of operative management was lower.
Davis et al. conducted a cost analysis to compare open reduction with cast immobilization for treatment of acute nondisplaced mid-waist scaphoid fractures11. A mathematical model was developed to calculate the outcomes and cost of open reduction compared with cast immobilization with use of the estimated Medicare reimbursement rates and the cost of lost productivity estimated by average wages obtained from the United States Bureau of Labor and Statistics. They found that open reduction with internal fixation offered greater quality-adjusted life years than did casting. Open reduction and internal fixation was less costly than casting ($7,940 versus $13,851 per patient, respectively) because of the longer period of lost productivity with casting.
There is strong consensus in the literature that nonunion of the scaphoid should be treated operatively (Table III). Management of scaphoid nonunion depends on the scaphoid alignment, bone loss, presence of a humpback deformity, carpal collapse, and osteonecrosis. Nonunion of the scaphoid leads to a predictable humpback deformity with flexion of the distal pole.
Fractures of the scaphoid continue to be a challenge to the surgeon. What's hot in the management of scaphoid fractures over the past two decades is the development of percutaneous and arthroscopic techniques of scaphoid stabilization that minimize surgical morbidity. However, potential complications do exist, and this discussion will describe techniques used to lower the complication rate. In addition, what's hot in scaphoid treatment is substantial improvement in the treatment of difficult scaphoid nonunions with or without deformity. This includes open and dorsal approaches to the scaphoid and vascularized bone-grafting of resistant scaphoid nonunions. What's not hot in scaphoid management is prolonged immobilization for unstable fractures when surgical stabilization may have been the best option and complications from an arthroscopic or open procedure that potentially could have been avoided. This discussion aims to help the surgeon define the indications for operative management in a patient with a fracture of the scaphoid, and furthermore, when operative fixation is indicated, to define whether an arthroscopic or open technique is the best option.
Volar Percutaneous Technique
Haddad and Goddard popularized the volar percutaneous technique12. The patient is positioned supine with the thumb suspended in a Chinese finger trap. Placing the thumb under suspension allows ulnar deviation of the wrist, which improves surgical access to the distal pole of the scaphoid. Under fluoroscopic guidance, a longitudinal 0.5-cm-long skin incision is made over the distal radial aspect of the scaphoid and a percutaneous guidewire is inserted into the scaphotrapezial joint and advanced proximally and dorsally across the fracture site. The position of the guidewire is easily checked by rotating the forearm under fluoroscopy. This technique provides an almost 360° view of the position of the guidewire within the scaphoid. The length of the guidewire within the scaphoid is determined by placing a second guidewire next to the initial one and measuring the difference between the two. A drill is then inserted through the soft-tissue protector, the scaphoid is reamed, and a headless cannulated screw is inserted.
This technique is straightforward and requires minimal specialized equipment. The disadvantage is that the screw may be placed slightly oblique to a fracture line in the mid-waist portion of the scaphoid.
Dorsal Percutaneous Approach
Slade et al. popularized the dorsal percutaneous approach13. The wrist is flexed and pronated under fluoroscopy until the proximal and distal poles of the scaphoid are aligned to form a perfect cylinder. Continuous fluoroscopy is recommended as the wrist is flexed and pronated to obtain a true ring sign as the proximal and distal poles are aligned. Under fluoroscopy, a 14-gauge needle is placed percutaneously in the center of the ring sign and parallel to the fluoroscopic beam. A guidewire is inserted through the 14-gauge needle and driven across the central axis of the scaphoid until it comes in contact with the distal cortex of the scaphoid. It is important not to extend the wrist as this may bend the guidewire. A second guidewire is then placed parallel to the first so that it touches the proximal pole of the scaphoid, and the difference in length of the two guidewires is measured to determine the length of the screw. Slade et al. recommended use of a screw 4 mm shorter than what is measured to allow compression at the fracture site. The goal is to place a screw the length of the scaphoid to compress the fracture and to resist the lever-arm bending forces.
The primary guidewire is then advanced volarly until it is flush with the proximal pole of the scaphoid dorsally and the wrist is extended.
The radiocarpal and midcarpal spaces are evaluated arthroscopically for any associated soft-tissue injuries. The arthroscope is placed in the midcarpal space to evaluate the fracture reduction and may be adjusted. The wrist is then flexed and the guidewire is advanced dorsally, exiting the skin. A portion of the guidewire is to be left outside of the volar and dorsal aspects of the wrist in case of wire breakage. Blunt dissection is continued around the guidewire dorsally to minimize the risk of soft-tissue injury to the extensor tendon as the scaphoid is reamed and the screw is inserted.
The advantage of the dorsal approach is that the screw can be inserted down the central axis of the scaphoid. The disadvantage of the dorsal approach is that, as the wrist is hyperflexed, the unstable scaphoid fracture may displace to create a humpback deformity.
Arthroscopic Reduction (the Geissler Technique)
This technique can be used both for acute scaphoid fractures and selected scaphoid nonunions14.
The hand is initially suspended in a traction tower (Acumed, Hillsboro, Oregon) at 30° of wrist flexion. The arthroscope is initially placed in the 3-4 portal (i.e., between the extensor pollicis longus [EPL] and extensor digitorum tendons) to evaluate any associated soft-tissue injuries. The arthroscope is then transferred into the 6-R portal (Fig. 1). A 14-gauge needle is inserted through the 3-4 portal and the scapholunate interosseous ligament is palpated at its junction with the proximal pole of the scaphoid (Fig. 2). The junction of the scapholunate interosseous ligament with the proximal pole of the scaphoid along its middle third is the ideal starting point, and the needle is inserted there. The traction tower is flexed at its base, and the starting point of the needle is evaluated under fluoroscopy. The needle is simply aimed toward the thumb under fluoroscopy, and a guidewire is advanced through the needle and down the central axis of the scaphoid to abut the distal pole (Fig. 3). The position of the guidewire is evaluated under fluoroscopic guidance by rotating the forearm in the traction tower (Fig. 4). A second guidewire is placed against the proximal pole of the scaphoid to determine the length of the screw. A screw that is at least 4 mm shorter than the length measured is utilized.
The reduction of the scaphoid is evaluated with the arthroscope in the midcarpal portals. The traction tower may be flexed, extended, and deviated either radially or ulnarly to further reduce the fracture. After the fracture is reduced, the guidewire is aimed proximally into the proximal pole of the scaphoid and out the dorsum of the wrist. The scaphoid is then reamed, and a headless cannulated screw is placed (Figs. 5 and 6). It is important to arthroscopically evaluate the radiocarpal space after screw insertion to ensure that the screw is inserted completely within the scaphoid and is not protruding proximally, which would injure the articular cartilage of the distal portion of the radius.
The advantage of this technique is that it allows direct visualization and reduction of the scaphoid fracture, the precise insertion point for the guidewire is identified, and the wrist is not hyperflexed, which could displace the fracture. Associated soft-tissue injuries that may occur with a fracture of the scaphoid may be detected and can be managed at the same sitting.
Slade et al. described their use of Slade's dorsal percutaneous fixation technique in fifteen patients with stable fibrous nonunions of the scaphoid13. All patients underwent percutaneous dorsal fixation with a headless cannulated screw and no accessory bone-grafting. All fractures healed in an average of three months. Twelve of fifteen patients had excellent results according to the modified Mayo wrist scale. Dorsal percutaneous fixation without bone-grafting was recommended for patients with a stable fibrous nonunion with no signs of a humpback deformity. This technique may be utilized in scaphoid nonunion Types I to III, as proposed by Slade et al.
For patients who have a cystic scaphoid nonunion without a humpback deformity (i.e., Type IV), percutaneous cancellous bone-grafting or injection of demineralized bone matrix may be used. With the Geissler technique, a guidewire is inserted down the central axis of the scaphoid and the scaphoid is reamed through a soft-tissue protector. A bone biopsy needle filled with demineralized bone matrix putty is placed over the guidewire and inserted through the reamed scaphoid directly into the nonunion site. The demineralized bone matrix is then injected through the bone biopsy needle directly into the central hole of the scaphoid at the nonunion site. Following injection of the demineralized bone matrix, the guidewire is advanced back through the bone biopsy needle, from volar to dorsal, out the dorsum of the wrist. A headless cannulated screw is then inserted over the guidewire across the fracture site, and the radiocarpal and midcarpal spaces are reevaluated arthroscopically.
Geissler and Slade reported on the use of the Geissler technique in fifteen patients with cystic scaphoid nonunions without humpback deformity6, with fourteen of the patients obtaining fracture union.
Mini-Open Technique
The mini-open dorsal technique is a modification of the dorsal percutaneous technique that was popularized by Slade et al.15. The entry point for the guidewire is identified by an open incision, making this a simpler technique.
Indications and Contraindications
The dorsal mini-open technique can be utilized for the fixation of acute nondisplaced scaphoid waist fractures and proximal pole fractures. Augmented with bone-grafting, the technique can be utilized for treatment of delayed union and scaphoid nonunion without collapse. In displaced fractures, the percutaneous technique can only be employed if the scaphoid can be reduced by percutaneous manipulation with use of Kirschner wires. Fractures of the distal third of the scaphoid should be fixed from the volar approach to ensure more screw purchase in the smaller fragment.
Surgical Technique
The following landmarks are identified by palpation and are marked on the skin: scaphoid tuberosity on the palmar aspect, tip of the radial styloid on the radial aspect, and the Lister tubercle on the dorsum of the radius. These three landmarks help to identify the spatial orientation of the scaphoid on the surface and facilitate guidewire placement. A longitudinal skin incision, approximately 1 cm in length, is placed over the radiocarpal joint radial to the Lister tubercle and extending along the radial border of the third metacarpal (Fig. 7). The incision corresponds to the 3-4 wrist arthroscopy portal. The EPL tendon is identified and is released for a distance of 2 cm to allow retraction of the EPL radially. The fascia over the extensor digitorum communis tendon in the fourth compartment is incised longitudinally. By placing retractors between the EPL tendon radially and the extensor digitorum communis tendons ulnarly, the underlying radiocarpal joint capsule is exposed at the level of the scapholunate articulation.
A limited longitudinal capsulotomy is performed along the long axis of the incision, taking care to avoid plunging the scalpel blade into the scapholunate interosseous ligament. The articular surface of the scaphoid is immediately visible, and it is possible to identify the dorsal portion of the scapholunate interosseous ligament and its insertion on the scaphoid pole. The wrist is flexed over a bolster of three rolled towels. The starting point for a central guidewire is located 3 mm radial to the insertion of the proximal membranous portion of the scapholunate ligament origin. A soft-tissue protector or a 14-gauge intravenous cannula is placed at this point and directed to a point 5 mm distal to the scaphoid tuberosity. The appropriate guidewire is inserted through the cannula until it tents the skin on the palm at the intended exit point. The direction of the guidewire may be checked fluoroscopically on a lateral radiograph with the wrist pronated to 45°. A small stab incision may be necessary to facilitate the exiting of the wire on the palmar surface (Fig. 8). A second guidewire is inserted 4 mm from the first, and the more central of the two wires is selected, with the second wire used to prevent fracture displacement during drilling and screw insertion.
The wires are then withdrawn through the palmar wound until they lie flush within the articular surface of the scaphoid. The wrist is extended for imaging (Fig. 9). The more optimal wire is selected for drilling the screw track. The selected guidewire is drilled back into the scaphoid in a retrograde direction under fluoroscopic control until it lies within the scaphoid at the scaphotrapezial joint. The length of the guidewire within the scaphoid is measured. A screw that is 4 mm shorter than this measurement is selected.
The wire is driven back in an antegrade direction to exit at the palm in order to have access to both ends of the wire in case of breakage. A cannulated drill is inserted over the guidewire, and the screw track is prepared by hand or with use of power drilling. The selected cannulated screw is then manually inserted over the wire until the screw lies 2 mm beneath the articular surface.
The capsulotomy is left open, and the skin edges are approximated. The wrist is immobilized in a short arm plaster splint, and frequent digital range-of-motion exercises are initiated. The patient is fitted with a removable wrist splint and given instructions for a home-exercise program of wrist and hand mobilization to be performed several times a day, with the wrist out of the splint, starting at two weeks postoperatively (Fig. 10).
Open Treatment of Scaphoid Fractures and Nonunions
Open techniques for fixation of scaphoid fractures are indicated for the acute displaced scaphoid fracture that cannot be reduced by closed means, comminuted acute fractures, and many, but not all, scaphoid nonunions6.
Surgical Approaches
The volar approach is typically used for distal third or mid-waist fractures or nonunions of the scaphoid. This approach is particularly useful to correct a humpback deformity of the scaphoid. The important dorsal blood supply is left undisturbed, and a good view of the volar surface of the scaphoid is facilitated. Care is taken to preserve and repair the volar carpal ligaments to avoid instability. Use of a structural corticocancellous bone graft can restore carpal height and correct a humpback deformity.
A longitudinal incision is made over the flexor carpi radialis tendon (FCR). Distally, the incision is curved obliquely toward the scaphoid tubercle. The FCR is retracted ulnarly, and the dissection proceeds through the floor of the FCR sheath ulnar to the radial artery. The capsule is opened between the long radiolunate ligament and the radioscaphocapitate ligament. The fracture site is exposed for reduction or curetting and/or bone-grafting as needed. Structural bone graft may be placed for correction of a humpback deformity, or a vascularized bone graft may be used. It is sometimes helpful to insert 0.045 or 0.054-in (1.1 or 1.4 mm) Kirschner wires into the proximal and distal fragments to use as joysticks for manipulation of the fragments. The radial surface of the capitate is used as a template for reduction and, by moving the Kirschner wires divergently, the nonunion site can be exposed for curettage and preparation of the nonunion site for bone-grafting.
Several nonvascular bone-grafting techniques are noted, as follows. The Matti-Russe bone-graft technique involves creation of cavities in the proximal and distal fragments to accept placement of a strip of corticocancellous bone, which is then wedged into place. This provides intrinsic stability, which may be sufficient alone or may be augmented with Kirschner wires. This technique is not appropriate in the presence of osteonecrosis of the proximal pole or a humpback deformity16. Reported union rates have ranged from 54% to 92%. The technique described by Fernandez involves use of a wedge-shaped corticocancellous graft, usually from the iliac crest, to restore alignment in a humpback deformity5. Fixation is applied to secure the graft and nonunion site. Union rates have been reported to be >94%5.
The screw can easily be placed from distal to proximal. To improve the starting point, the proximal volar portion of the trapezium may be removed, thus allowing the surgeon to place the guide pin and screw in a more centralized starting point. A guide pin is directed in a 45° plane to the forearm in both the coronal and sagittal planes. Following completion of scaphoid bone-grafting and fixation, final radiographic images are assessed and the capsule is repaired (Figs. 11 and 12).
A dorsal approach is most useful for proximal pole fractures and preserves the volar carpal ligaments. In addition, exposure of the scapholunate ligament is facilitated to address any injury there. There are concerns about disruption of the blood supply to the scaphoid, particularly in the setting of nonunions. The incision may be longitudinal or transverse and is centered over Lister's tubercle. The surgical approach is as previously described in the mini-open technique.
Pedicled Vascularized Bone Grafts for Scaphoid Nonunions
The emergence of vascularized bone grafts has changed the treatment of scaphoid nonunions. Their use can lead to a faster rate of union, and they improve the viability of the proximal pole. They can also provide an alternative to a salvage procedure with previously failed conventional bone-grafting. A variety of grafts with a vascular pedicle from the dorsal and volar aspects of the distal part of the radius have been described, as well as a graft from the thumb metacarpal with a vascular pedicle (Figs. 13, 14, and 15).
Indications
Some general indications for the use of vascularized bone grafts are noted below, although some authors use this type of graft for any scaphoid nonunion:
Osteonecrosis of the proximal pole
Symptomatic proximal pole nonunion
Displaced proximal pole fractures
Failed traditional bone-grafting
Absolute Contraindications
The following constitute contraindications to the use of vascular pedicle flaps based on the radius and thumb metacarpal:
Radiocarpal and midcarpal arthritis due to a scaphoid nonunion advanced collapse wrist, stage II/III (i.e., radiocarpal/midcarpal arthritis)
Damage to the radial artery, first dorsal metacarpal artery, or dorsal carpal arch. Relative contraindications to the procedure include previous surgery on or injury to the dorsal aspect of the wrist or distal part of the radius, which might impair the blood supply to the dorsal capsule. Proceed carefully in patients who are smokers.
Vascularized Bone Grafts with 1,2 Intercompartmental Supraretinacular Artery
In 1991 Zaidemberg et al. described a bone-graft source from the dorsoradial aspect of the radius with a vascular pedicle based on an ascending irrigating branch of the radial artery17. That group reported a 100% union rate in eleven patients who had a scaphoid nonunion treated with this graft, at an average time to union of 6.2 weeks. The blood supply to the dorsal aspect of the carpus has been extensively described by Sheetz et al.18. They described a number of pedicles from which potential vascularized bone grafts may be harvested from the dorsum of the distal aspect of the radius. The most common of these pedicles is the 1,2 intercompartmental supraretinacular artery, which is the term now used for the ascending irrigating branch of the radial artery.
Anatomy
The 1,2 intercompartmental supraretinacular artery branches from the radial artery at an average of 1.9 mm proximal to the radial styloid (range, –6.3 to 3.2 mm). The internal diameter of the vessel averages 0.30 mm (range, 0.14 to 0.58 mm). The pedicle length averages 22.5 mm (range, 15 to 31 mm). The graft is located approximately 10 mm (range, 8 to 18 mm) proximal to the articular surface, where it incorporates the largest number of perforator vessels.
Advantages and Disadvantages
This graft can be used as an onlay graft to act as a vascular pedicle or a structural strut graft to maintain the scaphoid length. It has a constant artery with a long pedicle. Because it is rotated 180°, the pedicle is vulnerable to kinking. Dissection of the pedicle can be tedious, and impingement and thrombosis of the pedicle over the radial styloid can occur when attempting to pass the graft volarly. It is prudent to perform a limited radial styloidectomy to decrease tension on the pedicle and facilitate volar passage.
Volar Carpal Artery Vascularized Bone Graft
Anatomy
This vascularized bone graft was initially described by Kuhlmann et al.19 and was recently popularized by Mathoulin et al.20. The vascularized bone graft is harvested from the volar ulnar metaphysis of the distal part of the radius. It is nourished by the volar carpal artery, which has a diameter of 0.5 to 1.0 mm. This artery originates from the radial artery at the level of the radial styloid and traverses the palmar aspect of the distal part of the radius along the distal edge of the pronator quadratus muscle. It forms a “T”-shaped anastomosis with the anterior interosseous artery. The average vascular pedicle length is 3 cm (range, 2 to 4.6 cm).
Advantages and Disadvantages
This vascularized bone graft has a long pedicle that is consistently present, and harvesting the volar carpal artery does not interfere with the dorsal blood supply. It is ideal for scaphoid nonunions with a humpback deformity since the volar approach provides good access to the nonunion site for debridement and simplifies the insertion of a volar wedge-shaped graft to restore scaphoid height. It is a small graft, however, and is technically difficult to raise. It cannot be used for nonunions of the distal third of the scaphoid. Since it is immediately adjacent to the radiocarpal joint, there is the risk of fracture into the radiocarpal joint or the sigmoid notch.
Capsular-Based Vascularized Bone Graft
Anatomy
This vascularized bone graft, which was originally described by Sotereanos et al.21, is an axial pattern flap based on the fourth extra-compartment artery of the dorsal carpal arch, which extends between the anterior or posterior interosseous artery proximally and the dorsal carpal arch or fifth extra-compartment artery distally. The average pedicle diameter is 0.4 mm. The pedicle length ranges between 1 and 2 cm and easily reaches the proximal third of the scaphoid (Figs. 16, 17, and 18).
Advantages and Disadvantages
The vascularized bone graft is based on a constant artery and the flap is easy to dissect. The graft only needs to rotate 10° to 30° on the pedicle to reach the scaphoid, which lowers the risk of arterial kinking. A disadvantage is that it has a relatively short pedicle; hence the graft is only useful for proximal third nonunions. It can be used as an onlay graft only, and there is the risk of a radiocarpal articular fracture.
Vascularized Thumb Metacarpal Graft
Anatomy
This vascularized bone graft, as described by Bertelli et al.22, is based on the radial branch of the first dorsal metacarpal artery. The average vessel diameter is 1 mm. The pedicle arises from the radial artery 5 to 10 mm proximal to the trapeziometacarpal joint and continues along the radial third of the dorsal side of the thumb metacarpal. The vascularized bone graft is harvested from the metacarpal head, resulting in a pedicle length of approximately 50 mm.
Advantages and Disadvantages
The pedicle can be quite long and is based on a constant artery. It can be used as an onlay or structural graft. The pedicle is rotated 180°, which can lead to kinking. It leaves a large donor-site defect, which can lead to fracture and it is technically difficult.
Fractures of the scaphoid are common injuries. There are several treatment options available, including percutaneous, arthroscopic, and open volar and dorsal approaches. There are advantages and disadvantages associated with each technique, and the surgeon should select what is most comfortable in his or her hands. In addition, for resistant scaphoid nonunions, there are multiple vascularized bone-grafting techniques to obtain union in these difficult fractures.