Composite graft survival in allen zone II fingertip amputations: Independent predictors of graft failure

Composite grafting is a commonly used treatment option for Allen Zone II fingertip amputations; however, reported survival rates vary considerably across studies. Although several clinical and injury-related factors have been suggested to influence graft survival, independent predictors of failure and clinically meaningful ischemia duration thresholds remain insufficiently defined. This study aimed to identify independent clinical predictors of composite graft survival and to explore, secondarily, whether ischemia duration is associated with graft failure.

Forty-two patients who underwent composite grafting due to Allen Zone II fingertip amputation between December 2021 and June 2023 were retrospectively evaluated. Baseline variables were collected from hospital records and surgical notes. Ischemia duration was calculated as the number of hours between the injury and the start of surgery. Diabetes mellitus (DM) and other comorbidities were verified using diagnostic codes and patient histories. The primary outcome measure was graft survival at 6 weeks postoperatively; necrosis affecting more than 25% of the graft surface area was defined as failure. Group comparisons, univariate and multivariate logistic regression, and receiver operating characteristic (ROC) curve analysis were performed. Because of the limited number of outcome events and quasi-complete separation in the data, the multivariable model was additionally fitted using Firth's penalised likelihood method.

Graft survival was achieved in 23 cases (54.8%), while 19 cases (45.2%) resulted in failure. Factors associated with graft failure included older age, longer ischemia duration, presence of DM, and crush/avulsion type injuries. In further analysis, DM and crush/avulsion injury mechanism emerged as the most important independent predictors of graft failure, whereas age and ischemia duration were less influential when considered alongside other variables. Penalised estimates were more conservative than unpenalised ones but preserved both associations (DM, OR 12.63; crush/avulsion mechanism, OR 12.29). In exploratory ROC analysis an ischemia duration threshold of 4.3 h was associated with failure, although ischemia duration was not an independent predictor. Overall, the combined evaluation of clinical variables demonstrated strong ability to distinguish between successful and unsuccessful graft outcomes.

In cases of Allen Zone II fingertip amputations, the crush/avulsion mechanism and DM are the strongest independent predictors of composite graft failure. An ischemia duration exceeding 4.3 h was associated with failure in exploratory analysis but was not an independent predictor. Preoperative assessment of these parameters may inform patient selection, pending prospective validation.