From the Guidelines
Yes, a CT scan can show a midfoot union that is missed by X-rays after Lapidus surgery. The sensitivity of radiographs in detecting midfoot fractures is reported to be moderate to poor, ranging from 25% to 33% 1. This limitation is particularly relevant in the context of Lapidus surgery, where accurate assessment of bone healing is crucial for treatment decisions. CT scans offer a significant advantage over X-rays by providing detailed, three-dimensional images of bone structures, which can help identify subtle signs of fusion or non-union that may be obscured in X-ray images due to overlapping bones or limited viewing angles. In the diagnosis of acute hyperflexion injuries to the foot, studies have concluded that conventional radiographs, including weightbearing images, are not sufficient for routine diagnostic workup, and CT should serve as the primary imaging technique 1. This recommendation can be extrapolated to the postoperative assessment of midfoot union after Lapidus surgery, where the complex anatomy of the midfoot region and the need for precise evaluation of bone fusion make CT scans a valuable diagnostic tool. Key benefits of using CT scans in this context include:
- Improved visualization of the fusion site from multiple angles
- Ability to detect small gaps or incomplete fusion that may not be visible on X-rays
- Enhanced diagnostic accuracy for treatment decisions
- Particular usefulness in the complex midfoot region where multiple small bones articulate closely together.
From the Research
CT Scan vs X-Rays for Midfoot Union
- A CT scan can provide more detailed images of the midfoot area compared to X-rays, which may help identify a midfoot union that is missed by X-rays post Lapidus surgery 2.
- The study by 2 found that CT-assessed torsional rigidity and callus density are promising parameters to represent actual bone union after a fracture, arthrodesis, or osteotomy.
- Another study by 3 used CT scans to assess the incidence and characteristics of midfoot injuries, including Lisfranc and Chopart injuries, and found that CT scans can provide valuable information about the midfoot area.
Limitations of X-Rays
- X-rays may not provide sufficient detail to detect a midfoot union, especially if the union is not fully consolidated or if there is overlap of bones in the midfoot area.
- The studies by 4, 5, and 6 focused on the outcomes of Lapidus surgery, but did not specifically compare the effectiveness of CT scans and X-rays in detecting midfoot union.
Potential of CT Scans
- CT scans may be useful in detecting midfoot union post Lapidus surgery, especially in cases where X-rays are inconclusive or suspicious for nonunion 2.
- The use of CT scans in assessing bone union has been shown to be accurate and reliable, and may be considered as a follow-up imaging modality after Lapidus surgery 2.