1 Diagnosis top
Navicular fractures are often the result of high-energy injuries. In athletic injuries, they are most common in jumping sports, like basketball. The patient presents with either immediate or delayed pain.
In the multiply-injured patient, navicular fractures are often overlooked. These injuries are often picked up on the secondary survey. The unconscious patient should be carefully examined for unusual swelling or crepitus. If suspected, foot x-rays are indicated.
Often there is swelling and point tenderness. The split or stress fractures are as a rule not associated with any deformity. The higher-energy injuries (MVA or industrial/crush) are associated not only with marked soft-tissue trauma, but also with other injuries to the foot and deformity is more likely to be present.
Plain x-rays often show a linear fracture line in the central portion of the navicular.
If a fracture is clinically suspected, but not evident on the x-ray, then proceed to other means of imaging. The TC99 bone scan may show an area of increased uptake and a CT and an MRI may give you a more definitive answer.
2 Principles topenlarge
Talonavicular joint function
The talonavicular (TN) joint allows for hindfoot motion in all planes. Loss of TN motion results in loss of complex hindfoot circumduction. It is therefore extremely important to retain TN function as it has a protective function for the adjacent joints. Loss of TN motion leads to adjacent joint degeneration (DJD). Retaining even a small amount of motion is thought to be protective for the adjacent joint function. The TN joint, because of its extensive range of motion, is also known as the “coxa pedis”.
Simple fracture – maintain navicular concavity
When treating fractures of the navicular, it is important to maintain the concavity of the navicular.
In simple fractures, reduction compression devices may lead to overcompression and loss of shape and congruency. This affects talonavicular (TN) joint motion, if the tips of the reduction clamp are positioned to far proximally, a malreduction is usually the result. The tips should be positioned in such a way as to provide even compression across the fracture.
As described above, the shape of the TN joint is important. In comminuted fractures of the navicular, there is great danger of losing the normal geometry. Every attempt should be made to reconstruct the shape of the navicular while maintaining soft-tissue attachments and blood supply.
The navicular has an oval shape on cross-section. Small branches of the posterior tibial and dorsalis pedis 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.
Maintain medial column length
Medial column length is crucial in maintaining the shape of the medial arch of the foot.
If the navicular injury has resulted in comminution with loss of length, in reconstruction we must regain length, as well as normal geometry. Bridging the hardware distally and using bone graft will assure proper length of the medial column, overall shape and alignment of the foot.
The form and function of the foot is dependent on the normal relationship between the medial and lateral columns. If the relative lengths of the medial and lateral columns are not maintained, foot deformity such as cavus or planus results.
Relative shortening of the medial column leads to cavus whereas relative shortening of the lateral column leads to flat foot.
3 Reduction topenlarge
Preparation of the fracture site
A dorsomedial approach is made directly over the fracture without peripheral dissection and undermining. This maintains the blood supply. The fracture is then entered directly and dealt with as necessary.
A medial-column distractor can be used to assist in inspection and reduction of the joint surface.
Distraction is particularly important if one is dealing with comminution or if a delay has occurred between the injury and the definitive reduction. Care must be taken to maintain medial column length and alignment.
Insert the pointed reduction forceps through two small stab incisions placed dorsomedially and dorsolaterally. Remember to place the tips in the center of the fragments, since a proximal positioning of the tips may lead to malreduction.
Reduce the fracture carefully. Do not overcompress, since this will destroy the anatomical concavity of the joint surface.
Provisional fixation can be done using K-wires. If solid screws are to be used, be sure to place the K-wires so that they will not interfere with the subsequent screw placement.
If cannulated screws are used, the guide wires can be used for provisional fixation.
Take care not to penetrate the joint with the K-wires, or screws.
Ensure that the joint is anatomically reduced. Check reduction, if possible, under direct vision or by palpating the articular surface with an elevator. Use image intensification to check your reduction. Remember that the resolution of the image intensifier may not be sufficient to appreciate small joint incongruities. If in doubt, get intraoperative x-rays.