O243: The effect of midcarpal fusions on dart thrower’s motion: a cadaveric study

Abstract

Abstract Introduction Midcarpal osteoarthritis can be managed with several types of partial wrist fusion. Limited information is available regarding their effects on functional movement. Many daily activities require a coupled wrist movement, from radial extension to ulnar flexion, termed dart thrower’s motion (DTM). This study aimed to compare the effect of four different midcarpal fusions on DTM. Methods Twelve fresh-frozen cadaveric specimens were dissected. Sequential loading of tendons into radial extension and ulnar flexion enabled full DTM to be measured using goniometry. Specimens were tested at baseline and following each fusion, performed sequentially using Kirschner wires: (1) scaphocapitate fusion, (2) lunocapitate fusion with scaphoid excision, (3) four-corner fusion with scaphoid excision and (4) three-corner fusion with scaphoid and triquetral excision. A one-way ANOVA and Tukey test established the significance of differences in range of motion. Results Each procedure significantly decreased DTM compared with intact wrists. Scaphocapitate fusion resulted in the smallest mean reduction in movement from 78°–70° (p=0.0014). Four-corner fusion produced the greatest reduction in DTM from 78°–63° (p<0.0001). There was a significant difference in DTM between four-corner and scaphocapitate fusions (p=0.0338). There was no significant difference in the range of postoperative DTM between lunocapitate, three-corner, or four-corner fusions. Conclusion DTM was minimally affected by scaphocapitate fusion and maximally affected by four-corner fusion, with a significant difference seen between these two operations. However, as a 44°–87° range of DTM was maintained for four-corner fusions, this is felt to be adequate for function. These results could aid preoperative decision-making.