A retrospective study of closed extension block pinning for mallet fractures: Analysis of predictors of postoperative range of motion

Extension block pinning is a simple and reliable technique for mallet fractures, but poor results are sometimes obtained. The predictors of postoperative range of motion after extension block pinning of mallet fingers were investigated. The outcomes for postoperative active motion of the distal interphalangeal (DIP) joint, such as flexion angle, extension loss, and total range of motion, were examined. Predictors such as age, gender, finger, fragment size, joint subluxation, the time from injury to operation, procedure, fixation angle, the time from operation to wire removal, and joint step-off were evaluated statistically. With a mean 12.2-month follow-up, according to Crawford's criteria, 49 of 116 fingers (42%) had an excellent result, 37 (32%) had a good result, 29 (25%) had a fair result, and 1 (1%) had a poor result. The mean flexion angle was 62.9 ± 13.2°, extension loss was −6.6 ± 7.3°, and total range of motion was 55.8 ± 17.0° in the DIP joint. Pin tract infections were confirmed in 7 fingers with poor results. There were no complaints about nail deformity or skin abnormality. On multivariate analysis, significant predictors of poor postoperative motion were increased age chronic case, remained joint step-off, excess flexed fixation angle, and long-term wire placement. Extremely flexed fixation and chronic case easily causes extension loss in the DIP joint. In closed extension block pinning, joint fixation with an extreme flexion angle should be avoided and the pinning wire should be removed as soon as possible after confirming bony union.