How does ulnar shortening osteotomy influence morphologic changes in the triangular fibrocartilage complex?

BACKGROUND: Ulnar shortening osteotomy often is indicated for treatment of injuries to the triangular fibrocartilage complex (TFCC). However, the effect of ulnar shortening osteotomy on the changes in shape of the TFCC is unclear. In our study, quantitative evaluations were performed using MRI to clarify the effect of ulnar shortening on triangular fibrocartilage (TFC) thickness attributable to disc regeneration of the TFC and TFC angle attributable to the suspension effect of ulnar shortening on the TFC.

QUESTIONS/PURPOSES: The purposes of this study were (1) to compare preoperative and postoperative TFC thickness and TFC angle on MR images to quantitatively evaluate the effect of ulnar shortening osteotomy on disc regeneration and the suspension effect on the TFC; and (2) to assess whether changes in TFC thickness and TFC angle correlated with the Mayo wrist score.

METHODS: Between 1995 and 2008, 256 patients underwent ulnar shortening osteotomy for TFCC injuries. The minimum followup was 24 months (mean, 51 months; range, 24-210 months). A total of 79 patients (31%) with complete followup including preoperative and postoperative MR images and the Mayo wrist score was included in this retrospective study. Evaluation of the postoperative MR images and the Mayo wrist score were performed at the final followup. The remaining 177 patients did not undergo postoperative MRI, or they had a previous fracture, large tears of the disc proper, or were lost to followup. Two orthopaedists, one of whom performed the surgeries, measured the TFC thickness and the TFC angle on coronal MR images before and after surgery for each patient. Correlations of the percent change in the TFC thickness and the magnitude of TFC angle change with age, sex, postoperative MR images, extent of ulnar shortening, preoperative ulnar variance, and postoperative Mayo wrist score were assessed.

RESULTS: Stepwise regression analysis showed a correlation between the percent change in TFC thickness and preoperative ulnar variance (R2=0.21; β=-0.33; 95% CI, -0.11 to 0.01; p=0.01) and between the magnitude of change in the TFC angle and the extent of ulnar shortening (R2=0.18; β=-0.29; 95% CI, -5.8 to 0.29; p=0.03). The Mayo wrist score was not correlated with the percent change in TFC thickness or the magnitude of change in the TFC angle.

CONCLUSIONS: These results suggest that, in patients with TFCC injury with a smaller preoperative ulnar variance, a high residual potential for regeneration in the disc proper was seen after ulnar shortening osteotomy, and correlated with the extent of ulnar shortening and the suspension effect on TFC. However, there was no correlation between disc regeneration or the suspension effect on TFC and the Mayo wrist score.

LEVEL OF EVIDENCE: Level IV, therapeutic study. See the Instructions for Authors for a complete description of levels of evidence.