J Korean Orthop Assoc.  2012 Feb;47(1):9-14. 10.4055/jkoa.2012.47.1.9.

Optimal Pelvic Inlet and Outlet Radiograph Angles in Korean Patients

• Park DY
• Kim JH
• Nair SG
• Won YY

• KMID: 1439986
• DOI: http://doi.org/10.4055/jkoa.2012.47.1.9

Abstract

PURPOSE
Until now, pelvic injuries have been evaluated with 45degrees inlet and 45degrees outlet radiographs. Following these customary guidelines may not produce the best plane to evaluate pelvic injury due to variability of pelvic anatomy. Recent data based on the American population suggested 25degrees and 60degrees as the optimal angle for each inlet and outlet views, respectively. We hypothesized that inlet and outlet radiographic views to examine the clinically relevant landmarks vary from routine 45degrees inlet and outlet views and aimed to find optimal angles for Korean patients.
MATERIALS AND METHODS
One hundred consecutive patients, aged between 30 to 60 years (50 male and 50 female patients), without pelvic ring disruption or fractures who had undergone routine axial pelvic computed tomography scans were retrospectively identified. The optimal inlet and outlet angles required to profile the clinically relevant pelvic anatomy were quantified for each patient.
RESULTS
The optimal inlet angle to profile the anterior body of S1 and S2 required an average caudal tilt of 24.2degrees and 27.9degrees, respectively. The average outlet angle perpendicular to the body of S1 was 54.8degrees and perpendicular to S2 was 52.3degrees. The optimal angles were the same for male and female patients and were independent of patient age.
CONCLUSION
Screening inlet and screening outlet radiographs made at 25degrees and 55degrees, respectively, are recommended for viewing clinically relevant osseous pelvic anatomy in Koreans.

Keyword

pelvis; pelvic inlet view; pelvic outlet view

MeSH Terms

Aged
Bays
Female
Humans
Male
Mass Screening
Pelvis
Retrospective Studies

Figure

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  Figure 1 The inlet angle required to profile the anterior body of S1 is the angle formed between the line tangent to the anterior cortical margin of S1 and a line in the anteroposterior plane. These measurements were made with use of sagittal computed tomography reconstructions taken in the midline (inset).

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  Figure 2 The inlet angle required to profile the pubic rami is the angle formed between the line bisecting the rami and a line in the anteroposterior plane. These measurements were made with use of sagittal computed tomography reconstructions taken 1 cm from the midline (inset).

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  Figure 3 Because of the trapezoidal shape of the S1 body, the outlet angle required to be perpendicular to the S1 body was found by first defining perpendiculars to the anterior and posterior cortical margins of S1. The line that bisected the angle formed by these perpendiculars was used to define the 'average' perpendicular to the S1 body. The angle formed between the average perpendicular and a line in the anteroposterior plane defined the S1 body outlet angle. These measurements were made with use of midline sagittal computed tomography reconstructions.

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  Figure 4 The outlet angle required to profile the S1 neural foramina is the angle formed between the line collinear with the neural foramen and a line in the anteroposterior plane. These measurements were made with use of paramedian sagittal computed tomography reconstructions through the S1 neural foramina.

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