Arch Hand Microsurg 2018; 23(4): 239-247  
Reduction Loss after Extension Block Kirschner Wire Fixation for Treatment of Bony Mallet Finger
Byungsung Kim1, Jae-Hwi Nho2, Ki Jin Jung3, Keonhee Yun1, Eunseok Park1, Sungyong Park4
1Department of Orthopedic Surgery, Soonchunhyang University Bucheon Hospital, Bucheon, Korea
2Department of Orthopedic Surgery, Soonchunhyang University Seoul Hospital, Seoul, Korea
3Department of Orthopedic Surgery, Soonchunhyang University Cheonan Hospital, Cheonan, Korea
4Department of Orthopedic Surgery, Seogwipo Medical Center, Seogwipo, Korea
Correspondence to: Sungyong Park
Department of Orthopedic Surgery, Seogwipo Medical Center, 47 Jangsu-ro, Seogwipo 63585, Korea
TEL: +82-64-730-3416, FAX: +82-64-733-4320, E-mail:
Received: July 24, 2018; Revised: September 14, 2018; Accepted: September 17, 2018; Published online: December 1, 2018.
© Korean Society for Surgery of the Hand, Korean Society for Microsurgery, and Korean Society for Surgery of the Peripheral Nerve. All rights reserved.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Purpose: We investigated occurrence of reduction loss after extension block (EB) Kirschner wire fixation or additional interfragmentary fixation (AIF) and clinical results including extension lag of the distal interphalangeal joint for treating bony mallet finger.
Methods: Forty-six patients were included with a mean follow-up of 28 months (range, 12-54 months). Twenty-seven patients were treated with EB K-wire fixation (Group A) while 19 patients were treated with AIF (Group B). We checked radiologic factors, such as amount of articular involvement, volar subluxation, mallet fragment angle, reduction loss, range of motion including extension lag, and functional outcomes using Crawford’s criteria.
Results: Reduction loss occurred in eight patients (17%). Differences in mean extension lag, age, preoperative volar subluxation and mallet fragment angle between patients with reduction loss and those with reduction maintaining were significant. However, there were no significant differences in gender, hand dominance, amount of articular involvement, AIF, or further flexion between reduction loss and reduction maintaining. As for patterns of displacement, there was a significant relationship between gap or step-off and extension lag. Using Crawford’s evaluation criteria, functional outcomes were excellent in 31, good in 10, fair in 3, and poor in 2 patients.
Conclusion: Reduction loss should be careful in older age, smaller mallet fragment angle and preoperative volar subluxation.
Keywords: Mallet finger, Extension block, Additional interfragmentary fixation, Reduction loss

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