12 Percutaneous Scaphoid Fixation: Volar Traction Approach

10.1055/b-0034-80577

12 Percutaneous Scaphoid Fixation: Volar Traction Approach

Goddard, Nicholas J.

Fractures of the scaphoid lead to significant physical and economic morbidity. Early rigid fixation has recently been advocated to promote rapid functional recovery. Open reduction and internal fixation of the scaphoid is, however, technically demanding, damages the anterior radiocarpal ligaments, violates the scaphotrapezial joint, further endangers the already compromised blood supply of the scaphoid, and not infrequently leads to troublesome hypertrophic scars. These problems can be overcome by percutaneous fixation.

▪ Rationale and Basic Science Pertinent to the Procedure

The management of scaphoid fractures still generates significant debate.1 There is no general consensus as to either the duration or the ideal position for cast immobilization. It is notoriously difficult to ensure that the fracture has united, and importantly, even in recently reported series there is an unacceptably high nonunion rate of 25%.2

Acute open reduction and rigid internal fixation of displaced or complicated scaphoid fractures is now widely accepted as the best practice. We are indebted to Tim Herbert who by introducing a reliable technique and a suitable device firmly established that screw fixation of the scaphoid was a viable treatment option.3 ^, 4

The role of surgery for minimally displaced or undisplaced fractures remains unclear. It is, however, apparent that the majority of scaphoid fractures occur in young men who may be manual workers or who may be involved in athletic activity. The avoidance of plaster immobilization in these patients is desirable. Early and stable fixation of scaphoid fractures provides the opportunity for early wrist mobilization and an earlier return to full function.

Satisfactory function following a scaphoid fracture is more likely with fractures that heal in an anatomical position. This is facilitated, though not necessarily accelerated, by stable fixation with a compression screw. Herbert and Fisher reported a far higher union rate for acutely stabilized scaphoid fractures.3 This was supported by the later work of Bunker et al,5 and Wozasek and Moser.6

The open approach to scaphoid fracture fixation is technically demanding, damages the anterior radiocarpal ligaments, violates the scaphotrapezial joint, further endangers the already compromised blood supply of the scaphoid, and not infrequently leads to troublesome hypertrophic scars.2 ^, 4 In addition Garcia-Elias et al reported carpal instability after volar approaches to the scaphoid that damage the radiocapitate and radiolunate ligaments.7

The percutaneous technique minimizes operative trauma and attempts to preserve the blood supply of the scaphoid and the integrity of its surrounding ligaments. Closed percutaneous scaphoid fixation, however, can be performed as a day case and allows for earlier mobilization and an increased rate of union and has been shown to have fewer complications.

Percutaneous screw fixation of the scaphoid was first reported by Streli in 1970 in the German literature.8 In 1991 Wozasek and Moser reported an adaptation of Streli’s technique using cannulated 2.9 mm screws via a volar percutaneous approach with an 89% union rate.6 Ledoux and colleagues reported 23 cases using percutaneous Herbert screw osteosynthesis of the scaphoid bone with union in all cases, 95% range of movement compared with the other side, and better key pinch than the contralateral hand.9

Scaphoid screw fixation has now been extensively evaluated both clinically and biomechanically.10 ^– 13 Although the Herbert screw has a long and admirable clinical track record,3 it is by no means the ideal implant. Shaw demonstrated greater compression forces using AO screws (Synthes, Paoli, PA) but accepted the biological advantages of the headless Herbert screw, which can be buried within the scaphoid without disrupting its bony architecture.10 Rankin et al later confirmed his findings.11

My preference is to use the Acutrak screw (Acumed, Inc., Hillsboro, OR), which is a headless, highly polished, tapered, self-tapping, fully threaded, cannulated device designed to provide interfragmentary compression. Variable pitch creates gradual compression with each turn of the screw. In a “bone-foam” biomechanical study, Acutrak and AO screws had higher peak compressive forces than the Herbert/Whipple screw, while the Acutrak screw had the greatest push-out resistance (Wheeler, Scott, and Shannon, pers. comm.). It could therefore be postulated that the Acutrak screw combines some of the advantages of the Herbert or Herbert-Whipple system in being headless and having a variable pitch, while also providing improved interfragmentary compression.

In 1996 we further modified and simplified the volar percutaneous technique using the cannulated Acutrak screw to stabilize minimally displaced oblique waist fractures or undisplaced waist fractures (Herbert classification B1 or B2) acute scaphoid fractures.14 In our pilot study we reported a union rate of 100% and our current experience continues to reflect this high rate of union. Encouraged by our early results, we have now expanded the indications to include displaced fractures, delayed union, and selected patterns of nonunions where we often combine screw fixation with supplementary percutaneous bone grafting.

▪ Indications

There may still be a place for nonoperative treatment, which is undoubtedly safe but with a known rate of nonunion and the associated inconvenience of plaster immobilization. Percutaneous fixation is now a justifiable alternative to cast immobilization and permits early rehabilitation with minimal risks and a high, if not guaranteed, rate of union.

The volar (distal to proximal) approach is applicable to all waist fractures and some proximal third fractures depending on the obliquity of the fracture line.

The majority of our patients are male with an average age of almost 28 and the dominant side affected in ∼75% of cases.

Having elected for percutaneous fixation there is a distinct window of opportunity. Obviously the complex fracture dislocations require immediate intervention, but for other cases surgery can be postponed until the next suitable operating list and in practice can be delayed by up to 4 weeks without reducing the chance of ultimate fracture union. Beyond this stage I would recommend supplementary measures such as cancellous bone grafting, which can be performed percutaneously, with or without arthroscopic assistance.

▪ Contraindications

Proximal pole fractures are probably best dealt with via a dorsal (proximal to distal) approach as described by Slade and Jaskwhich.15 Humpback deformities or scaphoid collapse with a dorsal intercalated segmental instability pattern (DISI) deformity usually require open treatment. Naturally local sepsis should be viewed with caution.

▪ Surgical Technique

The procedure of percutaneous scaphoid fixation using a cannulated screw can be formed under general or regional anesthesia. Although I accept that it is entirely feasible to perform the operation with the affected arm abducted on a hand table we have found it easier to use a modification of the original technique described by Wozasek and Moser.

The patient is placed supine on an operating table, the forearm and hand are prepared in a standard fashion, and the rest of the upper limb and body are covered with an extremity drape ( Fig. 12.1 ). I routinely infiltrate the proposed entry point of the guide wire with 2 mL 2% lidocaine with 1:200,000 adrenaline. The use of a tourniquet is optional.

**Fig. 12.1** Overall setup. Note that the thumb is suspended by a single trap so placing the wrist in slight ulnar deviation and extension. The C-arm is brought in horizontally across the patient’s upper body with the scaphoid at the center.

The hand is suspended by the thumb alone in a single Chinese finger trap with no countertraction. This position extends the scaphoid and ulnar deviates the wrist to improve access to the distal pole of the scaphoid. Importantly it permits free rotation of the hand throughout the operation, and the scaphoid remains in the center of the x-ray field throughout ( Fig. 12.2 ).

The image intensifier C-arm is turned to a horizontal position and positioned so that the wrist is in the central axis. With the image intensifier in this position it is then possible to screen the scaphoid continuously around the axis of the radial column. In the majority of cases there is no need for any additional measures to reduce the fracture. However, if it is felt that the position of the fracture is unacceptable then K-wires can be inserted and used as joysticks to manipulate the fragments into position. The quality of the reduction can then be checked radiographically and if necessary arthroscopically without disturbing the overall setup. As with any closed fracture fixation time spent in setting up and ensuring quality of the reduction is time well spent.

Having achieved an acceptable reduction the first, and probably most important step is to establish the entry point of the guide wire and hence ultimately the position of the screw. The ulnar deviation of the wrist allows the distal half of the scaphoid to slide out from under the radial styloid. The scaphoid tuberosity is easily palpable and is the key to the insertion point.

**Fig. 12.2** Close-up of the entry point. Note that the entry point is more proximal and more volar than one might normally have assumed. It is helpful to use a 12 or 14 gauge intravenous cannula as a trocar and aiming device, initially bringing it into the scaphotrapezial joint and then swinging it progressively vertically and anteriorly to line up the proposed direction of the guide wire aiming toward the scapholunate junction and Lister’s tubercle.

The entry point is then located using a 12 gauge IV needle introduced on the anteroradial aspect of the wrist just radial to and distal to the scaphoid tuberosity.16 This serves as a trocar for the guide wire and proves to be invaluable as a direction aid so as to establish a central path along the scaphoid.17 The needle is then insinuated into the scaphotrapezial joint, tilted into a more vertical position and the position checked on the under-image intensifier. By gently levering on the trapezium this maneuver brings the distal pole of the scaphoid more radial and thus ultimately facilitates screw insertion. It is then possible to screen the wrist by simply rotating the forearm in the x-ray beam and lining up the needle along the long axis of the scaphoid in all planes. The aim should be to have the guide wire exiting the proximal pole just radial to the scapholunate junction. I have found it helpful to have my thumb on the scaphoid tuberosity and index finger over the Lister tubercle and to aim the guide wire toward my index finger. This invariably gives the correct direction. Once I am happy with the entry point and the direction of the guide wire I lightly tap the needle into the soft articular cartilage over the distal pole of the scaphoid so that the tip does not slip during the insertion of the guide wire. Any “fine tuning” can be performed at this point by rotating the IV cannula because the effect of the bevel can change the position of the ultimate entry point by up to 1 mm.

The guide wire (0.045 in./1.1 mm) can then be passed down through the needle and drilled across the fracture, continually checking the direction on the image intensifier and correcting as necessary, aiming for the radial aspect of the proximal pole. This requires an appreciation of the obliquity of the scaphoid in both anteroposterior and lateral planes. It is extremely important not to bend the guide wire, and any adjustments in direction should be made using the needle as a guide rather than attempting to alter the line of the guide wire alone ( Figs. 12.3 and 12.4 ).

The guide wire should be advanced to stop just short of the articular surface and should not breach it at this stage. The position, alignment, and length are checked once more. If the position is felt to be satisfactory then a longitudinal incision of 0.5 cm is made at the entry point of the wire and deepened down to the distal pole of the scaphoid using a small hemostat and blunt dissection. This is a relatively safe zone with minimal risk to the adjacent neurovascular tructures.18

The length of the screw is then determined either by using the proprietary depth gauge or by advancing a second guide wire of the same length up the distal cortex of the scaphoid and subtracting the difference between the two. The correct screw size is 2 to 4 mm shorter than the measured length so as to ensure that the screw head is fully buried below the cartilage and the cortical surface. The positioning guide wire is then advanced through the proximal pole of the scaphoid so as to exit on the dorsal aspect of the wrist. This is a precautionary measure to minimize the risk of inadvertent withdrawal of the wire during the reaming process and screw insertion and to facilitate removal of the proximal portion if the wire were to break. In those rare cases where it is felt that there is a possibility of rotational instability it is recommended that a second derotation wire be inserted parallel to the first prior to drilling and reaming. Such an instance would be encountered in early stabilization of a transscaphoid perilunate fracture dislocation, for example.

**Fig. 12.3** Anteroposterior position of the guide wire. Note the entry point at the lateral border of the scaphoid tuberosity and the 14 gauge needle being used as an aiming device and trocar. The guide wire should be directed to the radial aspect of the scapholunate joint.

**Fig. 12.4** Lateral position of the guide wire. This position is just acceptable, but ideally could be a little more anterior. It is along the central axis of the bone.

Having secured the guide wire the 12 g needle is then slid off and the cannulated drill is then passed over the wire using either a power drill or a hand reamer, stopping 1 to 2 mm short of the articular surface. My preference is to drill on power to minimize the risk of repeated bending of the guide wire, there by reducing the chance of breakage. It is helpful to screen this process to ensure accurate drilling and especially to ensure that the guide wire has not been inadvertently bent ( Fig. 12.5 ).

The self-tapping screw is then advanced over the guide wire and the wire removed. Compression can then be confirmed radiographically on the image intensifier ( Fig. 12.6 ).

The skin is closed using a single Steri-Strip (3M, St. Paul, MN) or suture, which is covered with a sterile compressive dressing. The tourniquet is released and the arm elevated. Plaster immobilization is entirely optional and is not used in our unit when fixation appears stable.

The arm is elevated immediately postoperatively, and routine postanesthetic and neurovascular observations recorded.

The patients are encouraged to begin active finger exercises prior to discharge. The patients are reviewed 10 days postoperatively to exclude sepsis and ensure that early mobilization is being performed. The sutures are removed at this stage and carpal radiographs taken to confirm that screw position is satisfactory. At this stage patients are allowed to mobilize gently, but no heavy carrying or weight-bearing activity is permitted.

**Fig. 12.5** After measuring the length of the screw the guide wire is advanced through the articular surface so as to prevent inadvertent withdrawal while reaming and during screw fixation. The chosen screw must be 2 to 4 mm shorter than the measured length. Note that the reamer has stopped 2 to 3 mm short of the proximal pole.

**Fig. 12.6** AP **(A)** and lateral **(B)** views show the final position of the screw. Note the position and alignment along the central axis and that both ends are buried beneath the articular surfaces.

We review the patient 4 weeks later, and further radiographs are taken. Return to sedentary work is allowed as soon as the patient feels ready or when 75% of the contralateral range of movement is achieved. Manual work and athletic activity are deferred until there is radiographic evidence (either plain films, or ideally CT scan) of fracture union. Patients are advised to wear a supportive splint for contact sports. There is usually no need to remove the screw at a later date.

Practical Tips and Pearls for Successful Outcomes

Take time in positioning the patient to allow 360 degree visualization of the scaphoid on the image intensifier.
Establish the correct entry point, which should be just dorsal and just radial to the tip of the scaphoid tuberosity19
Aim the guide wire to exit at the tip of the proximal pole at the scapholunate junction.
Ensure that the guide wire is along the longest axis of the scaphoid and is as central as possible.
Advance the guide wire to the 3,4 arthroscopic portal to minimize the risk of accidental withdrawal and to facilitate its removal in the event of breakage.
Ensure that the screw is contained within the body of the scaphoid with both ends deep to the articular surface. The chosen screw must be 2 to 4 mm shorter than the measured length. Bear in mind that the average length of a male scaphoid is 31.3 mm (+/− 2.1 mm) and female 27.3 mm (+/− 1.7 mm).20
Place the screw with the trailing edge closest to the fracture site. Thus distal pole fractures are best treated by volar placement, proximal pole fractures by dorsal/ proximal placement, and waist fractures by whichever is most comfortable for and familiar to the operator.