Quantifying scaphoid malalignment based upon height-to-length ratios obtained by 3-dimensional computed tomography.

PURPOSE: To determine if 3-dimensional height-to-length (H/L) measurements including coronal plane assessment will improve malalignment detection of scaphoid fractures and to determine if more waist than proximal pole nonunions are malaligned.

METHODS

Computed tomography scans of uninjured wrists (n = 74) were used to obtain 3-dimensional models of healthy scaphoids. These models were used to determine 95% normal ranges of the H/L ratio in standard sagittal and coronal planes in an automated fashion. Subsequently, the H/L ratios of fibrous nonunions (n = 26) were compared with these normal ranges and were classified as either aligned or malaligned.

RESULTS

The mean normal H/L ratio in the sagittal plane was 0.61 (range, 0.54-0.69) and in the coronal plane 0.42 (range, 0.36-0.48). The mean H/L ratios of the nonunions differed from those of the healthy scaphoids in these planes: 0.65 and 0.48, respectively. Based on sagittal plane evaluation of all nonunions, 46% exceeded the normal H/L range versus 54% based on combining sagittal and coronal plane measurements. More waist nonunions (71%) than proximal pole nonunions (22%) exceed the normal H/L range.

CONCLUSIONS

Evaluation of the H/L ratio in the coronal plane provided valuable additional information for the detection of scaphoid deformities. More malaligned cases were found for waist nonunions than for proximal pole nonunions.

CLINICAL RELEVANCE: This method may be a helpful diagnostic tool to detect malalignment and to choose between in situ fixation or reconstruction.