Intraosseous rotation of the scaphoid: assessment by using a 3D CT model--an anatomic study.

OBJECTIVES

The purpose of this study was to assess intraosseous rotation as the third dimension of scaphoid anatomy on a 3D CT model using common volume rendering software to impact anatomical reconstruction of scaphoid fractures.

METHODS

CT images of 13 cadaver wrist pairs were acquired. Reference axes for the alignment of distal and proximal scaphoid poles were defined three-dimensionally. Two methods for rotation measurement-the reference axis method (RAM) and the scapho-trapezio-trapezoidal joint method (STTM)-were developed and compared by three independent observers.

RESULTS

Rotation measured by the RAM averaged 66.9° ± 7 for the right and 67.2° ± 5.8 for the left wrists. Using the STTM there was a mean rotation of 68.6° ± 6.6 for the right and 68.6° ± 6.8 for the left wrists. The overall results showed a significant variability of the measured values between different specimens (P < 0.05). There was no significant difference between left and right wrists of the same specimen, neither for the RAM (P = 0.268) nor for the STTM (P = 0.774). Repeatability coefficients between the observers were low, indicating good repeatability.

CONCLUSIONS

The presented methods are practical tools to quantify intraosseous rotation between distal and proximal scaphoid poles using common volume rendering software. For clinical application the opposite side provides the best reference values to assess malrotation in scaphoid fracture cases.

KEY POINTS: Scaphoid intraosseous rotation can be measured using common volume rendering software. The opposite uninjured side provides good reference values for rotation measurement. Assessment of malrotation may impact anatomical reconstruction of scaphoid fractures.