The foot’s form and function depend on the normal relationship between the medial and lateral columns.
Relative shortening of the medial column leads to cavus, whereas relative shortening of the lateral column leads to flat-foot.
If the injury has resulted in comminution with loss of medial or lateral column length, this length and normal geometry must be restored.
Bridging hardware and bone graft will assure proper column length, overall shape, and alignment of the foot.
Navicular blood supply
The navicular has an oval shape. Small branches of the posterior tibial and dorsal foot arteries comprise the blood supply of the navicular. The medial and lateral areas are more or less well supplied, while the central section has the most marginal blood supply.
2. Temporizing measures
Medial and lateral external fixation (with a distractor device to restore columnar length) should be applied as soon as possible to stabilize the foot and decrease further injury to the soft tissues.
Temporary percutaneous K-wires can be used to reduce displaced fragments and are left as temporary fixation.
Due to the high-energy injury of these fractures, the soft tissues, including the capsule and periosteum, are disrupted. Care should be taken to minimize soft-tissue stripping during the approach to maintain blood supply to the fragments.
Use a medial-column distractor to achieve the articular surface visualization needed for accurate reduction and fixation.
Distraction is essential when dealing with comminution or a delay between the injury and the definitive reduction.
The proximal pin is inserted into the neck of the talus through a stab incision. Image intensification can be used to ensure correct pin placement outside the articular surfaces. The correct insertion point is often located 1–2 cm posterior to the navicular tubercle.
The distal pin can either be inserted in the medial cuneiform (and potentially into the middle cuneiform for extra purchase or the first metatarsal).
The distraction vector must be in line with the talus and the first metatarsal in the medial plane to maintain the medial column alignment.
The fracture is distracted to allow complete visualization of either joint surface as needed.
Irrigate the fracture site using, eg, a syringe.
5. Reconstruction of the articular surface(s)
Use a curved elevator for joint surface reduction and the opposing articular surface(s) as a template.
It may be helpful to have a variety of elevators available to aid reduction.
Osteochondral fragments should be salvaged and secured with small lag screws if possible. Before screw fixation, a bone graft can be used to backfill any defect. If screw fixation is not possible, pins or K-wires can be used. K-wires can be cut and left in situ.
Ideally, joint reconstruction should be performed by inserting hardware only into the navicular.
While hardware may be inserted into the cuboid or cuneiforms for added support, mobility of the talonavicular joint should be maintained.
When adjacent joint surfaces are used as a template, verification of the reduction can become problematic if the fragments are fixed with a trans articular K-wire.
While reconstructing the joint surface, frequently check visually and radiographically to ensure no malreduction.
Reduction of dorsal dislocation
When the navicular is dorsally displaced, there will be a lateral plantar “constant” fragment still attached to the “spring ligament.” This fragment serves as a reference point for relocating the dislocated navicular.
The navicular is first reconstructed and then reduced anatomically to the "constant" fragment using reduction forceps. One tine is typically inserted dorsolaterally, and the other is inserted through the medial utility incision above the flexor tendons at the lateral plantar constant fragment. A bone graft can be used to backfill any defect to aid in osteochondral fragment reduction.
Anatomic reduction of a reconstructed navicular to the “constant” fragment ensures the correct reduction of the dorsally displaced navicular fracture.
6. Bone grafting
Once articular surface reconstruction is completed, the distraction can be adjusted to restore the length of the medial column.
It is helpful to have comparative x-rays from the uninjured side, allowing proper length and morphology to be judged.
The remaining defect can then be bone grafted using cancellous or corticocancellous bone graft for structural support harvested from the distal or proximal tibia.
While reconstructing the joint surface, frequently check to ensure no malreduction ensues.
7. Application of a navicular plate (if possible)
If the reconstructed navicular is relatively stable, plates with non-locking screws can be used.
Contour the navicular plate to match the patient’s anatomy.
When inserting screws in the proximal row adjacent to the talonavicular joint, the screws need to be directed anteriorly to prevent penetration into the concave joint.
If fixed angle locking head screws are used, additional contouring of the plate may be necessary to prevent joint penetration.
When contouring locking plates, care must be taken not to deform the screw holes.
All screws are inserted as position screws.
In dorsally displaced navicular fractures, care must be taken to insert screws through the dorsal reconstructed fragment into the constant plantar fragment. This is typically the two proximal lateral screws and the distal-most lateral screw.
If the constant fragment is too comminuted for fixation, trans-articular screws (from navicular to cuneiforms) or a bridging plate can be used to prevent the navicular from displacing dorsally.
Using intraoperative imaging, verify:
Restoration of the appropriate length of the medial column
Restoration of navicular shape
Appropriate screw placement and length
8. Temporary bridging (if needed)
A bridge plate or an external fixator may be used to supplement navicular reconstruction.
Temporary bridging with a plate
Plating can be performed through the dorsal or medial incision; however, soft-tissue stripping should be avoided.
Extensive dissection can be avoided by sliding the contoured plate subcutaneously along the medial aspect of the foot.
The plate length should allow for fixation using a minimum of two screws both proximally and distally.
The plate needs to be contoured to achieve a good fit and prevent tenting of the skin.
In-plane bending to adapt to the arch of the medial foot
Out of plane bending to adapt to the medial contour of the medial column
Torquing to fit both the neck of the talus proximally and the medial aspect of the first metatarsal distally
If possible, a screw may be inserted in the navicular to prevent late dislocation.
Temporary bridging using an external fixator
The medial column distractor can be replaced with an external fixation construct, which can be left in place while the bone heals instead of bridge plating.
Two bicortical pins are inserted in both the calcaneus and the 1st metatarsal.
Removal of bridging device
The bridging device should be removed when there is radiographic evidence of navicular healing, typically a minimum of three months.
The non-adherent antibacterial dressing is applied as a first layer. Sterile undercast padding is placed from toes to knee. Extra side and posterior cushion padding are added.
The foot should be immobilized for the first two weeks, which can be achieved using a three-sided plaster splint. The anterior area is left free of plaster to allow for swelling. Ensure that the splint’s medial and lateral vertical portions do not overlap anteriorly and that the splint does not compress the popliteal space or the calf.
The patient should be counseled to keep the leg on a cushion and elevated. Remember not to elevate the leg too much as it may impede the inflow. The foot’s ideal position is halfway between the waist and the heart when the patient is sitting. While seated, the foot should be on a cushion and elevated, but if badly swollen, the patient must be supine since elevating the foot while seated decreases swelling less effectively.
Avoid direct pressure against the heel during recumbency to prevent decubiti.
The OR dressing is usually left in place and not changed until the first postoperative visit at two weeks when x-rays are obtained once the dressing is removed. If any complication is suspected (eg, infection or compartment syndrome), the dressing must be split and, if necessary, removed to allow full inspection.
The strict non-weight bearing should be maintained until there is evidence of healing and any transfixion K-wires (6–12 weeks) or bridging devices (min 12 weeks) are removed.
Daily toe movement is encouraged.
Formal physical therapy should not begin in the early postoperative period.
A gastrocnemius release may need to be performed in cases with postoperative gastrocnemius contracture. This occurs more typically in the mid and hind-foot.