Scaphoid fixation approaches

Percutaneous Volar

Scaphoid fixation can be quite difficult due to the cashew nut shape and the need to place the screw in the midaxis of the scaphoid, without violating the radial and ulnar articular surfaces.

The dorsal approach is a simpler approach, is better for very small proximal fragments, but may interfere more with the blood supply of the scaphoid.

The volar approach avoids the dorsal blood supply and in non unions and flexed scaphoids it is easier to reduce the scaphoid and place the bone graft.

Percutaneous fixation is possible in undisplaced fractures.

Volar approach to scaphoid

Avoids dorsal blood supply.
Patient supine, tourniquet
Palpate FCR and tuberosity of the scaphoid (scaphotrapezial joint)
Begin 4 cm proximal to wrist crease centre over FCR, progress to wrist crease then angle across radially towards Scapotrapezial joint.
Open sheath FCR, can retract FCR radial or ulnar, if retract ulnar go between FCR and radial a.
Open deep fascia in bed of FCR
Expose palmar capsule over radioscaphoid joint, extend the wrist in ulnar deviation and open capsule obliquely in line of scaphoid.
Use graft if comminuted or tending to flex.
Fix with k wires or screw, close capsule and splint. (see acumed for mini accutrack technique)

Dorsal approach to the scaphoid

The volar approach is more difficult, because placement of the screw requires incision through the tough volar ligaments and exposure of the scaphotrapezial joint. Incision of the thin dorsal ligaments gives easy access to the entire carpus.

4-cm dorsal incision between the second and fourth compartments.
If wider exposure is needed for repair of other carpal injuries, then elevate extensor pollicis longus from the third compartment.
Open the wrist capsule longitudinally, evacuate the haematoma.
The fracture is easily observed after elevation of the wrist capsule.
Reduce and stabilize the fracture (temporary k wire.
Flex the wrist and insert guide wire into the scaphoid from the proximal pole to the distal pole.
Screen position from different angles to ensure accurate placement of guide wire.
Ensure the tip of the wire is 2 mm short of the distal articular surface, to ensure that the tip of the screw does not penetrate the distal cortex.
Be careful don't extend wrist while the guide wire is in the scaphoid, they are thin and break easily.
(see acumed for mini accutrack technique)

Percutaneous scaphoid fixation dorsal

Relies on surgeon's ability to target and align the scaphoid poles along their central axis using fluoroscopy
Clinical and biomechanical data suggest that the implantation of a headless cannulated screw along the central scaphoid axis increases rigidity and decreases healing time of acute fractures
The central axis of the scaphoid can be visualized with use of imaging by pronating and flexing the wrist.
The central axis of the scaphoid can be visualized with imaging. A posteroanterior view of the wrist is made, and the scaphoid is identified. The wrist is pronated until the scaphoid poles are aligned. In the imaging beam, the scaphoid shape changes from a “curved bean” to a cylinder. Flexing the wrist changes the scaphoid image from a cylinder to a circle. The poles of the scaphoid are now aligned with the imaging beam. This is the central axis of the scaphoid and the correct position for the guide-wire.
When this technique is used, the scaphoid is visualized as a circle and the centre of the circle is the central axis of the scaphoid.
If the central axis is difficult to define on imaging, it can be marked by placing a Kirschner wire in the distal scaphoid pole. On imaging, after pronation and flexion of the wrist, the tip of the wire points toward the centre of the circle
On occasion, the central axis can be difficult to define on imaging.
A double-cut 0.045-in (1.143-mm) guide-wire is introduced percutaneously at the base of the proximal scaphoid pole. The working distance between the mini-imaging unit's projection and receiving heads is approximately 14 in (36 cm) and can restrict the targeting of the scaphoid. A drill guide can be improvised by using a 12 or 14-gauge needle, which can be impaled into the proximal scaphoid pole. The wrist can then be removed from the imaging field, and the guide-wire can be introduced through the needle and driven in approximately 1 cm. The position and direction of the wire can be checked and adjusted as needed. If multiple passes are made, a track can be established, which can be difficult to change with a 0.045-in wire. However, a 0.062-in (1.575-mm) wire, with its increased stiffness, can be used to establish a new, correct track. Once the correct direction is established, this wire can be exchanged for the 0.045-in guide-wire.

To allow arthroscopic assesment of the joint after placement of the guide wire.

The wire is driven in a dorsal-to-volar direction with the wrist flexed. The wire passes through the trapezium and exits the wrist from the radial border of the thumb. This is a safe zone devoid of neurovascular structures.
The wire is then withdrawn until the wrist can be extended without bending the wire. Once the wrist is fully extended, both the position of the wire and the alignment of the scaphoid can be carefully inspected with imaging. Any changes in the position of the wire should be made now because later changes will alter the “apparent scaphoid length” and screw length selection.
With the wrist extended, imaging is used to confirm that the wire is in the correct position along the central axis in all planes. Any deviation from this position should be corrected at this point. Also, fracture reduction is confirmed. If fracture displacement is identified, the wire can be withdrawn volarly across the fracture site and 0.062-in (1.575-mm) wires can be placed percutaneously as joysticks to reduce the fracture. Once reduction is accomplished, the guide-wire is driven across the fracture site, securing reduction.
After imaging of the wire position and the fracture alignment has been completed, an arthroscopic survey is performed to confirm fracture reduction and to identify ligament injuries.
A complete arthroscopic examination includes visualization of the radiocarpal and midcarpal joints. Scaphoid fractures are best observed through the radial midcarpal portal.
Green evaluated bone viability at surgery by looking for punctate bleeding from the proximal scaphoid pole and suspecting osteonecrosis when that bleeding was absent. Green's bone viability test can also be performed arthroscopically, which limits unnecessary vascular disruption. First, the proximal pole of the scaphoid is reamed. Then, the arthroscope is inserted into the base of the scaphoid and into the previously reamed bone tract. The tourniquet is deflated, and the cancellous bone is inspected for punctate bleeding. Inflow irrigation is momentarily stopped while the time of the first appearance of bone bleeding is recorded.
With small-joint arthroscopy, the viability of the proximal scaphoid pole can be determined without risking further vascular injury from an open exploration. A tourniquet has been placed and elevated on a previously exsanguinated arm. A guide-wire is placed along the central axis, and the proximal scaphoid pole only is drilled. A small-joint angled arthroscope can then be introduced into the previously reamed portal, and fluoroscopy is used to guide its position to the scaphoid base. Alternately, the arthroscope can be introduced into the radiocarpal portal, and the drill hole at the scaphoid base is located. With the arthroscope seated, cancellous bone of the proximal scaphoid pole is identified. Arthroscopic inflow irrigation is halted, and the tourniquet is deflated. If the bone is viable, punctate bleeding will soon appear. With arthroscopic washings of the bone, one can often identify the exact location of the punctate bleeding.
After arthroscopic assesment is completed, the scaphoid length is determined. The wrist is removed from traction and flexed. The guide-wire is driven from volar to dorsal and is slowly withdrawn dorsally with the wrist maintained in a flexed position to prevent bending of the wire. With use of imaging, the trailing end of the wire is located and is withdrawn until its end reaches the distal scaphoid cortex. A second wire is placed at the base of the proximal pole of the scaphoid, next to the exit point of the dorsal wire. The difference in length between these two wires is the scaphoid length. With the wrist maintained in a flexed position, the guide-wire is again advanced volarly until it is exposed on both surfaces. A limited dorsal incision is made next to the wire, and the soft tissue is gently separated to the level of the wrist capsule. A standard cannulated Acutrak hand drill (Acumed, Beaverton, Oregon) is used to drill the scaphoid to within 2 mm of the opposite cortex. It is key not to overdrill the scaphoid because doing so risks the loss of fracture compression. A screw that is 4 mm shorter than the length of the scaphoid is selected. This permits 2 mm of clearance on both sides of the screw. If a screw is too long, it should be removed and replaced with a shorter one. Attempting to bury a longer screw will result in stripping of the bone cortex distally and create fracture separation.
A standard cannulated Acutrak hand drill is used, and the scaphoid is drilled not closer than 2 mm to the opposite distal scaphoid cortex. It is important to not overdrill the scaphoid. Damage may risk loss of fracture compression.
A standard-size screw, 4 mm shorter than the length of the scaphoid, is selected. This permits 2 mm of clearance on both sides of the screw. The most common pitfall in percutaneous screw implantation is selection of a screw that is too long; a too-proud screw risks cartilage injury. If an attempt is made to seat the screw by overdriving it against the opposite, unreamed cortex, the distal scaphoid fragment is stripped of bone and the proximal fragment will gradually separate from the distal fragment, creating a gap that decreases the opportunity for bone union.
Rigid fixation is achieved with implantation of a standard- size Acutrak screw, which is a cannulated headless implant that applies compression across the fracture site. With acute fractures, the native architecture is intact and supports screw fixation to provide a stable construct that permits early motion. In scaphoid nonunions, osteoporotic and necrotic bone may reduce the ability to obtain rigid fixation with the screw. If rigid fixation cannot be obtained by screw implantation alone, additional constructs are required. Temporarily locking the midcarpal row reduces the bending forces on the distal scaphoid pole and reduces microshear at the fracture site. This is accomplished by placement of a 0.062-in wire from the distal scaphoid pole into the capitate.
Postoperative care of scaphoid nonunions is sometimes different from that of acute fractures. For nonunions of the scaphoid waist, rigid fixation can often be achieved with a stout intramedullary device and does not require additional immobilization. Nonunions of the proximal pole or nonunions in osteoporotic bone in the waist are at a mechanical disadvantage, and rigid fixation can be difficult to achieve. These injuries are protected with a splint or a short arm cast for four to six weeks, until bone union has been established. In this series, only Grade-III ligament injuries were protected for six weeks. An early strengthening program encourages early recovery of hand function and provides axial loading of the nonunion site, to potentially stimulate healing.

Percutaneous fixation from volar

Place patient supine with the arm abducted on a radiolucent arm-board.

Place a towel roll under the supinated wrist to allow for adequate wrist extension.

Insert guide wire volarly, entering the distal scaphoid tuberosity, and directed proximally, dorsally, and ulnarly.

Use Image intensifier The image intensifier was used to confirm that the wire was placed along the longitudinal axis of the scaphoid and across the fracture site. Extension of the wrist assisted in translation of the trapezium dorsal to the path of the guide-wire. Screw length was measured indirectly with a second guide-wire or, alternatively, with the measuring device available in the screw set. An anti-rotation wire was placed parallel to the first guide-wire, so that it crossed the fracture site and was away from the initial guide-wire and thus did not interfere with the drill or screw (Figs. 3-A and 3-B).

The wrist is placed supine over a towel roll and extended in order to assist in translation of the trapezium dorsal to the path of the guide-wire. The guide-wire (0.035 in [0.889 mm] in diameter) is introduced volarly; it enters the distal scaphoid tuberosity and is directed proximally, dorsally, and ulnarly across the fracture site.

After the initial guide-wire is satisfactorily placed under fluoroscopic guidance, a second guide-wire is placed across the fracture site to prevent rotation of the fracture fragments during tapping and screw placement. Placement of the second wire is confirmed with fluoroscopy. Anteroposterior (Fig. 3-A) and lateral (Fig. 3-B) static fluoroscopic images are shown.

A 3-mm incision was made around the initial guide-wire to allow passage of the drill and screw. Blunt dissection around the guide-wire was accomplished with a fine hemostat. The scaphoid was then drilled by hand with the graduated cannulated drill, while the depth was monitored with fluoroscopy. The cannulated screw was placed under fluoroscopic guidance to ascertain the quality of the fracture reduction and screw position. The anti-rotation guide-wire was removed, and the wound was irrigated and then closed with a nylon suture. A well-padded short-arm thumb-spica plaster splint was applied.

The postoperative dressing was maintained for seven to ten days. After that time, a removable custom-fabricated Orthoplast short-arm thumb-spica splint was worn except during bathing or during the early active range-of-motion protocol and strength-maintenance program. Use of the splint was discontinued when the fracture united

References

Chung, Kevin C. M.D. A Simplified Approach for Unstable Scaphoid Fracture Fixation Using the Acutrak Screw. Plastic & Reconstructive Surgery. 110(7):1697-1703, December 2002.

SLADE, JOSEPH F. III MD; GEISSLER, WILLIAM B. MD; GUTOW, ANDREW P. MD; MERRELL, GREG A. MD PERCUTANEOUS INTERNAL FIXATION OF SELECTED SCAPHOID NONUNIONS WITH AN ARTHROSCOPICALLY ASSISTED DORSAL APPROACH. Journal of Bone & Joint Surgery - American Volume. 85-A SUPPLEMENT 4:20-32, 2003.

Bond, Charles D. MD; Shin, Alexander Y. MD; McBride, Mark T. MD; Dao, Khiem D. MD Percutaneous Screw Fixation or Cast Immobilization for Nondisplaced Scaphoid Fractures. Journal of Bone & Joint Surgery - American Volume. 83-A(4):483-488, April 2001.

Scaphoid fixation approaches

Volar

Dorsal