Clin Orthop Surg.  2012 Mar;4(1):83-90. 10.4055/cios.2012.4.1.83.

Evaluation of the Sigmoid Notch Involvement in the Intra-Articular Distal Radius Fractures: The Efficacy of Computed Tomography Compared with Plain X-ray

• Heo YM
• Roh JY
• Kim SB
• Yi JW
• Kim KK
• Oh BH
• Oh HT

• KMID: 1245403
• DOI: http://doi.org/10.4055/cios.2012.4.1.83

Abstract

BACKGROUND
The purpose of this study is to evaluate the efficacy of computed tomography (CT) scans compared with plain radiographs on detecting the involvement of the sigmoid notch.
METHODS
This study involved 121 cases diagnosed as the intra-articular distal radius fracture and performed post-reduction CT scans. We determined the presence of the sigmoid notch involvement with both plain radiographs and CT scans and compared findings of plain radiographs with CT scans about the incidence and the pattern of injuries. And the differences of results between arbeitsgemeinschaft fur osteosyntheses (AO) type C2 and C3 were compared.
RESULTS
The incidences of sigmoid notch involvement detected in plain radiographs were 81 cases (66.9%), whereas CT scans were 99 cases (81.9%). The sensitivity of plain radiographs compared with CT scans was 74.7%, the specificity was 68.2%, the positive predictive value was 91.4%, the negative predictive value was 37.5%, the false negative value was 25.3%, and the false positive value was 31.8%. In comparison between AO type C2 and C3, the incidence of sigmoid notch involvement was not a significant difference, but the displacement of fracture fragment showed a significant difference.
CONCLUSIONS
The intra-articular distal radius fracture usually accompanies the sigmoid notch involvement. Considering that the evaluation of sigmoid notch involvement by plain radiography often results in misinterpretation or underestimation, performing CT scan in intra-articular distal radius fracture is thought to be beneficial.

Keyword

Distal radius; Intra-articular fracture; Sigmoid notch; Computed tomography

MeSH Terms

Adolescent
Adult
Aged
Aged, 80 and over
Female
Humans
Intra-Articular Fractures/*radiography
Male
Middle Aged
Predictive Value of Tests
Radius Fractures/*radiography
Sensitivity and Specificity
*Tomography, X-Ray Computed
Young Adult

Figure

• 

  Fig. 1 Axial computed tomography image of the distal radius showing a displaced fracture of the sigmoid notch (SN). Point A and B were marked at subchondral fracture margins of SN. First line was drawn between the dorsal corner of SN and point B. Second line through point A was perpendicular to first line. The intersection of two lines was point C. Step-off of SN was measured as the distance between point A and C. Gap displacement was measured as the distance between point B and C.

• 

  Fig. 2 Sagittal computed tomography image of the radiocarpal joint. Point A and C were marked at subchondral fracture margin of lunate facet of distal radius. A circle matching curvature of remaining articular surface of distal radius was traced and passed through point A. First line was drawn from center of circle to point C. The intersection between circle and first line was point B. Step displacement is measured as the distance between points B and C. Gap displacement is measured as the distance between points A and B.

• 

  Fig. 3 Radiographs of 57-year-old woman with left distal radius fracture. Initial radiographs (A-C) were showing intra-articular fracture line (black arrow on image (A)) and metaphyseal comminution. But, authors misinterpreted the involvement of the sigmoid notch presented because of overlaps of ulnar head and lunate facet on lateral view (B) or dorsal-ulnar corner of distal radius on oblique view (C). The fracture of the sigmoid notch with displaced fragment was confirmed on axial computed tomography image (D).

• 

  Fig. 4 Initial radiographs (A-C) of 79-year-old man were showing intra-articular fracture of left distal radius fracture. The authors interpreted the disruption of the sigmoid notch with displacement of fracture fragment on image A-C. But, the sigmoid notch was intact and intra-articular fracture line was located near the sigmoid notch on axial computed tomography image (D).

• 

  Fig. 5 Distal radius fracture involved the articular surface of radiocarpal and distal radioulnar joint. This case was classified as arbeitsgemeinschaft für osteosyntheses type C3 and Ronzental type 3a. Axial-plane fracture line of the sigmoid notch can be easily found in coronal computed tomography image (C) than pre-reduction (A) or post-reduction (B) radiographs.

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  Fig. 6 Initial radiographs (A and B) and axial CT image (C) showing intra-articular distal radius fracture. This case was classified as arbeitsgemeinschaft für osteosyntheses type C2 and Rozental type 1b. Dorso-ulnar cortical corner fracture of the distal radius was not found on postero-anterior view (A) but oblique view (B). And minimal involvement of the sigmoid notch was confirmed on axial computed tomography image (C).

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  Fig. 7 Comminuted distal radius fracture was classified as arbeitsgemeinschaft für osteosyntheses type C3 and Rozental type 3b. An accurate assessment is difficult about sigmoid notch in plane radiograph (A). Axial (B) and sagittal (C) computed tomography image shows comminuted fracture of articular surface of the sigmoid notch.

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