Posttraumatic Osteoarthritis of the Distal Interphalangeal Joint: A Follow-Up Study of 12 Years After Nonsurgical Treatment of Mallet Finger Fractures.

PURPOSE: In treatment of mallet finger fractures (MFFs), the aim is to minimize residual extension lag, reduce subluxation, and restore congruency of the distal interphalangeal (DIP) joint. Failure to do so may increase the risk of secondary osteoarthritis (OA). However, long-term follow-up studies focusing on OA of the DIP joint after an MFF are scarce. The purpose of this study was to assess OA, functional outcomes, and patient-reported outcome measures (PROMs) after an MFF. METHODS: A cohort study was performed with 52 patients who sustained an MFF at a mean of 12.1 years (range, 9.9-15.5 years) previously and who were treated nonsurgically. A healthy contralateral DIP joint was used as the control. Outcomes were radiographic OA, using the Kellgren and Lawrence and Osteoarthritis Research Society International classifications, range of motion, pinch strength, and PROMs (Patient-Rated Wrist Hand Evaluation, Quick Disabilities of the Arm, Shoulder, and Hand, Michigan Hand Outcome Questionnaire, 12-item Short Form Health Survey). Radiographic OA was correlated with PROMs and functional outcomes. RESULTS: At follow-up, there was an increase in OA in 41% to 44% of the MFFs. Of all the MFFs, 23% to 25% showed a higher degree of OA than the healthy control DIP joint. Range of motion (mean difference ranging from -6° to -14°) and Michigan Hand Outcome Questionnaire score (median difference, -1.3) were decreased after MFFs but not to a clinically relevant extent. Radiographic OA was weakly to moderately correlated with functional outcomes and PROMs. CONCLUSIONS: Radiological OA after an MFF is similar to the natural degenerative process in the DIP joint and is accompanied by a decrease in range of motion of the DIP joint, which does not clinically affect PROMs. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.