gms | German Medical Science

Objectives/Interrogation: Restoring carpal alignment during four-corner fusion (4CF) to neutral position has been discussed in the literature as an important factor in range of motion preservation. To date, there have been limited studies focusing on whether the amount of capitate radial overhang relative to the lunate has an impact on functional outcomes. In this study, we explored the effect of specific parameters of carpal alignment on range of motion and grip strength of patients with lunate type 1 wrists treated with 4CF.

Methods: A retrospective chart review of a single-surgeon's practice over a six-year period was conducted to identify 15 patients with 15 lunate type I wrists who underwent 4CF for SLAC or SNAC. All wrists were treated with headless compression screw fixation. Primary functional outcomes included percentages of maintained pre-operative flexion-extension arc (FEA) and grip strength. Pre- and post-operative radiographs were analyzed to obtain lunocapitate and radiolunate angles and the amount of capitate radial overhang relative to the lunate. Scatterplots of primary functional outcomes were created to visualize data distribution against carpal alignment parameters and Pearson correlation coefficients were compared.

Results and Conclusions: Pre-operative lunocapitate angle (LCA) was the strongest predictor of percentage FEA maintained post-operatively, with many patients having actually improved their range. The greater the LCA pre-operatively, the greater maintained range post-operatively (r = 0.77). Furthermore, LCA correction was positively correlated with percentage maintained FEA (r = 0.52). Reduction of capitate radial overhang relative to lunate was negatively correlated with percentage maintained FEA (r = -0.54); meaning that greater the overhang and the less this articulation was reduced, the better post-operative range of motion outcomes patients were able to achieve. The relationship between radiolunate angle and functional outcomes was negligible. Grip strength was not strongly correlated with any alignment parameters.