The Optimal Position for Arthrodesis of the Proximal Interphalangeal Joints of the Border Digits.

This study aimed to determine the functional characteristics of various arthrodesis angles of the proximal interphalangeal (PIP) joints of the border fingers. The dominant hands of 48 volunteers were tested using custom orthoses to simulate PIP joint arthrodesis. For the index finger (IF), orthoses were made in 25°, 40°, and 55° of flexion (IF25, IF40, and IF55). For the little finger (LF), orthoses were made in 30°, 55°, and 70° of flexion (LF30, LF55, and LF70). Twenty-three volunteers performed grip and pinch (key, tripod, and pulp) strength testing with and without simulated arthrodeses and 25 volunteers performed the Jebsen Hand Function Test (JHFT) with and without simulated arthrodeses. Simulated conditions of arthrodesis were compared with the unrestricted state and with each other within the same finger. For grip and pinch strength, there were no significant differences between simulated arthrodesis angles. Compared with baseline, grip was significantly weaker for all 6 simulated arthrodesis angles. Pinch was tested with simulated IF arthrodesis only; key pinch was significantly weaker for all tested angles and tripod pinch for IF25 and IF40. For JHFT, the 3 experimental angles for the index or ring finger did not show any statistically significant differences for any subtest. Volunteers were slower at completion times for all simulated arthrodesis angles compared to baseline times. This was significant in 5 of 7 tasks for IF25, 3 of 7 tasks for IF40, and 4 of 7 tasks for IF55. Index finger angle of flexion of 40° was significantly faster than IF55 for writing and IF25 for lifting large, light objects. For the LF, LF30 was significantly slower than baseline for 6 of 7 tasks, LF55 for 3 of 7 tasks, and LF70 for 5 of 7 tasks. Index finger angle of flexion of 55° was significantly faster than LF70 for simulated feeding and IF30 for lifting large, heavy objects. No border digit PIP joint arthrodesis angle was superior for grip and pinch strength. Based on JHFT, IF40 and LF55 might be preferred arthrodesis angles. Intermediate arthrodesis angles may provide the best function for patients undergoing PIP joint arthrodesis of the IF and LF.

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