Associations Between Fracture Characteristics and Surgical Outcomes in Distal Digit Replantation of Tamai Zones 1-2

Although numerous risk factors were reported for the failure of digit replantation, there was a lack of studies investigating the association between replantation outcomes and fracture characteristics. The purpose of this study was to evaluate the survival rate and functional outcomes of distal digit replantation based on the fracture patterns.

We retrospectively reviewed patients with Tamai zones I-II amputated digits who underwent replantation between 2018 and 2022. The fracture characteristics of the distal phalanx were compared to outcomes, including the survival rate, Disabilities of the Arm, Shoulder, and Hand (DASH) scores, and range of motion (ROM) of the distal interphalangeal (DIP) joint. Additionally, we compared the diagnostic performance of our proposed FIVE criteria with the mechanism of injury (MOI) and other prognostic factors in predicting replantation failure.

51 digits from 48 patients, including 38 males, met the inclusion criteria. The overall survival rate was 29/51 digits (56.9%), consisting of 18/39 digits (46.2%) in crush-degloving injuries and 11/12 digits (91.7%) in sharp-cut injuries. Comminution of fractures significantly worsened the survival rate (10% vs. 69.7%; p = 0.002), while tuft fractures also significantly deteriorated the survival rate (34.8% vs. 75.0%; p = 0.005). Crush-degloving injuries significantly decreased the survival rate (p = 0.007). The FIVE criteria demonstrated relatively overall superior diagnostic performance for replantation failure, showing the highest accuracy (83.7%), specificity (89.7%), and positive predictive value (83.3%) compared to other indicators. The ROM of the DIP joint significantly worsened in high-energy fractures (p = 0.027) and subzone 4 digits (p = 0.012). DASH scores significantly deteriorated in high-energy fractures (p = 0.003), subzone 4 digits (p = 0.013), and base fractures (p = 0.036).

In Tamai zones 1-2, comprehensive evaluations of high-risk fracture patterns, MOI, and venous anastomosis can be a useful tool for more reliable prediction of replantation failure and functional outcomes.