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Introduction

The choices of treatment of scaphoid nonunion are numerous, varied, and often controversial. The use of a bone graft associated with an osteosynthesis has proved to be very efficient and enables union more frequently than when these two treatments were used separately.

Due to the technical difficulties encountered, vascularized bone grafts were usually reserved for when standard techniques failed. In 1965 Judet, with Roy-Camille, was the first to suggest using a bone graft harvested from the palmar aspect of the radius and vascularized by pronator quadratus fibers ⁽⁶⁾. This technique was then used by Braun ⁽²⁾ and more recently has been used by Kawai ⁽⁷⁾ with excellent results which showed union in all the cases in their series. Judet modified his technique in 1972 ⁽⁶⁾ because the graft harvested from the palmar aspect of the radius did not enable a long enough pedicle to be obtained; hyperflexion of the wrist was necessary to be able to reach the scaphoid. So he used a graft harvested from the distal tubercle and vascularized by the inserted muscle fibers. Several vascularized grafts have since been described and the results of the series have been very encouraging. (Guimberteau, Brunelli, Zaidemberg, Yuceturk, Mathoulin) (5, 3, 13, 12, 9, 10).

Anatomical background

We have taken the work of Kuhlman ⁽⁸⁾ to describe a graft harvested from the anterior aspect of the radius, vascularized by the volar carpal artery, the pedicle of which is long enough to reach the scaphoid without being strained (Mathoulin, Haerle 1998) ⁽⁹⁾ (fig1a, fig1b).

Figure 1a : Diagram showing scaphoid bone loss and the harvest zone of the graft.

Figure 1b : Diagram showing bone loss filled by the graft vascularized by the volar carpal artery

The principle of this bone graft is based on the presence of an anastomotic arterial network on the palmar aspect of the distal part of the two bones of the forearm (fig 2).

Figure 2 : Cadaveric dissection showing the volar carpal artery running along the distal edge of the pronator quadratus before anastomosing with the anterior interosseous artery and a branch of the ulnar artery (R : Radial artery, U : Ulnar artery)

Figure 4 : Magnified cadaveric dissection showing the origin of the volar carpal artery, the lateral part of which is detached from the radius.

We have performed 15 cadaveric dissections which have all shown the presence of a volar carpal artery thus confirming the work of Kuhlman. It originates from the radial artery at the level of the radial styloid and then runs along the palmar aspect of the radius. This artery follows the distal edge of the pronator quadratus and then forms anastomoses at the level of the palmar aspect of the distal radio ulnar joint with the distal branch of the anterior interosseous artery and a branch of the ulnar artery forming a vascular «T» at this level (fig 3). The anatomic dissections showed us that the volar carpal artery, after originating from the radial artery, remained slightly raised in relation to the lateral first third of the radius and then came back beside the radius with branches penetrating at the level of the radial epiphysis thus ensuring good bone vascularization (fig 4).

Figure 3 : Magnified cadaveric dissection showing the anastomosis zone forming the vascular «T». 1 – Tvolar carpal artery 2 – Distal branch of the anterior interosseous artery 3 – Branch of the ulnar artery

Technique

Preparation, installation

The patients are operated on in the supine position using a pneumatic tourniquet, the hand is in supination, the arm resting on an arm table. The anaesthetic is local regional and operations can be performed on an outpatient basis. A single approach is used for both the treatment of the pseudarthrosis and for harvesting the graft.

Surgical Approach

The surgical approach is a standard scaphoid approach that is to say the distal part of the Henry approach which can be extended either by an lateral distal extension towards the scaphoid tubercle or by a medial extension making it possible to enlarge the incision by opening the carpal tunel (fig 5a, fig 5b). Firstly the radial artery and the flexor carpi radialis are located (fig 6a, fig 6b). After freeing the superficial aponeurosis, the wrist is flexed permitting the tension in the tendons to be released. The radial artery is carefully retracted externally and the flexor carpi radialis with the flexor pollicis longus is retracted inwardly. In this way the whole of the anterior aspect of the radius and the carpus can be approached satisfactorily.

Figure 5a : Anterior surgical approach with a medial palmar extension

Figure 5b : Diagram showing the anterior surgical approach with a medial palmar extension

Figure 6a : Location of the Flexor Carpi Radialis and the radial artery.

Figure 6b : Diagram showing the location of the Flexor Carpi Radialis and the radial artery.

Scaphoid preparation

Before harvesting the graft the scaphoid is prepared so that the amount of bone loss can be determined. After having put a rolled up surgical towel under the wrist, thus putting it in extension and ulnar deviation, the anterior capsule is opened with regard to the scaphoid between the distal edge of the radius and the distal tubercle of the scaphoid. The pseudarthrosis zone is more often than not the seat of bone loss. Depending on its size there is sometimes scaphoid malunion with palmar flexion. The scaphoid reduction is performed using a chisel placed between the 2 scaphoid fragments and asking the operating assistant to pull on the thumb thus applying axial traction. The very existence of this palmar bone loss justifies the palmar surgical approach to repair the scaphoid. If there is considerable bone loss it may be necessary to use temporary k-wires to maintain the reduction, one placed between the proximal pole and the lunate, and the other between the distal tubercle and the capitatum. The pseudarthrosis zone itself is curetted. To speed up consolidation it is possible make small drill holes using a size 10 k-wire. When the scaphoid has been prepared we can focus attention on the palmar aspect of the radius with a view to harvesting the graft.

Location and dissection of the pedicle

As Foucher showed in the harvesting of the «Kite» flap, delicate dissection of small arteries can be dangerous. He preferred to take up a large flap around the arterial axis. This is possible when the artery has a more or less constant route. The volar carpal artery is almost always situated in the same place, between the palmar periosteum of the radius and the distal part of the superficial aponeurosis of the pronator quadratus. The dissection of the graft begins by opening the last distal centimeter of the superficial aponeurosis of the pronator quadratus until liberation of the muscular fibers proper and reaching the bone structure of the radius. This dissection is performed all the way across the radius as far as the level of the medial edge.

Using a scalpel the second part of the pedicle dissection divides the superficial aponeurosis and the periosteum on both sides of the pedicle over a width of about 1 cm. The external half of the pedicle as far as the radial artery is freed sub-periostally with the help of a scalpel and chisel. (fig 7a, fig 7b).

Figure 7a : After having flexed the wrist and retracted the F.C.R. and F.P.L. tendons the volar carpal artery running along the distal edge of the pronator quadratus can be located.

Figure 7b : Diagram showing the sub-periostal dissection of the lateral part of the pedicle.

Harvesting the graft

The graft is cut out using 10 mm chisels. The axes of the chisels are oblique on the distal and proximal part of the graft so as to come together below it to harvest a pyramid-shaped graft. For the division of the external part small 0.5 cm chisels are used so that we can go down both sides of the pedicle without damaging it. Using two chisels the graft is then opened up from the palmar aspect of the radius. (fig 8a, fig 8b).

Figure 8a : The harvesting of the graft using chisels.

Figure 8b : Diagram showing the harvesting of the graft using chisels.

Dissection of the pediculed graft

The graft and its pedicle are then dissected as far as the origin of the voalr carpal artery. The most lateral attachments of the pronator quadratus aponeurosis should be divided without hesitation in order to free up the pedicle, which will be 4 to 5 cm by the end of the operation, as much as possible.

Screwing the scaphoid

The screwing of the scaphoid is performed anteriorly from distal to proximal. The positioning of the screw is as dorsal as possible so that the placement of the graft is not hampered. The point of entry of the screw is preferably away from the scapho-trapezium joint in order to avoid any future discomfort (fig 9a, fig 9b).

Figure 9a : After having totally dissected the pedicled graft the scaphoid is screwed in a reduction position. Bone loss is present.

Figure 9b : Diagram showing the first scaphoid screwing after having properly reduced it by giving it enough height.

Placing the graft

The bone graft is placed so as to fill the bone loss on the palmar aspect of the scaphoid. The bone graft harvested is the same size as the bone loss and usually no other graft is necessary. If further grafting is necessary small cancellous bone grafts harvested at the expense of the palmar aspect of the radius are added. The fixation of the graft inside the scaphoid can de done in two ways : Either slight tightening of the screw placed in the scaphoid is sufficient to stabilize the graft between the proximal pole and the distal part of the scaphoid, or a temporary k-wire is put into place starting at the distal tubercle to «pin» the graft. This k-wire should be parallel to the screw taking care not to damage the vascular pedicle (fig 10a, fig 10b).

Figure 10a : The pedicled graft on the anterior transverse artery of the carpus fills the palmar scaphoid bone loss without straining.

Figure 10b : Diagram showing the positioning of the vascularized bone graft in the scaphoid bone loss.

End of operation : post-operative care

The capsule is sutured without compressing the pedicule by repairing in particular the radio-scapho-capitatum ligament. The closure is performed over a suction redon drain. An volar splint, leaving the elbow free and with a 40° extension of the wrist, is applied until union. This position is functionally comfortable for the patient and is made possible by the length of the pedicle. If a pin has been used to fix the graft it should be removed after 3 weeks. The screw is removed on request or if it is uncomfortable.

Conclusion

The use of a bone graft harvested from the volar aspect of the radius and vascularized by the volar carpal artery is a good treatment for moderate scaphoid bone loss (Alnot’s stage IIA, IIb and IIIa) ⁽¹⁾. If harvesting the graft can seem a little arduous at first it is in fact a simple technique which gives excellent results as shown by our average union time of 60 days in a series of 72 patients with an average follow up of 31 months (fig 11a-11f). Using a single volar surgical approach enables both the harvesting of the graft and the treatment of the pseudarthrosis to be performed during the same operation, avoiding a general anaesthetic and hospitalization. Even though this technique was first described for treating standard technique failures, the quality of the functional results obtained and the rapidity of union allows us to propose it as primary treatment for scaphoid nonunion.

Figure 11a : Clinical case : Frontal X-ray of a stage IIA (Alnot) pseudarthrosis of the scaphoid. We can note the extensive bone loss with no displacement at this stage.

Figure 11b : Per-operative view showing the harvested bone graft and the extensive palmar bone loss.

Figure 11c : Per-operative view showing the vascularized bone graft filling the bone loss. We can note the absence of any strain on the pedicle despite the extension position of the wrist.

Figure 11d : X-ray showing the union obtained at 45 days. We can see that the graft has been perfectly integrated.

Figure 11e : Tomodensitometry at 3 months after removal of a painful screw. The hole left by the passage of the screw can be seen within the perfectly reconstructed scaphoid.

Figure 11f : Frontal X-ray of the same scaphoid two years after reconstruction by vascularized bone grafting.