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Published on: November 13, 2016
Fracture-isthmus diameter ratio predicts delayed union in tibial nailing
Li-Kai Kuo1, Chun-Yu Chen1,2,3, Kai-Cheng Lin1
1Department of Orthopaedics, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan, ROC.
Background:
Intramedullary nailing is widely acknowledged as the preferred treatment for tibial shaft fractures. However, delayed union remains common in non-isthmal patterns. We aimed to assess the factors and imaging parameters associated with nonunion or delayed union following intramedullary nailing in these patients.
Methods:
This retrospective study included patients with non-isthmal tibial shaft fractures who underwent intramedullary nailing from 2015 to 2020. The fracture site diameter to the isthmus canal diameter ratio (FI ratio) was measured on pre- and postoperative anteroposterior (AP) radiographs. Delayed union was defined as no union at 6 months, with union by 12 months. The variables were tested with univariate analyses and multivariable logistic regression; receiver operating characteristic (ROC) analysis determined a cutoff.
Results:
A total of 66 patients were included, and delayed union occurred in 34 (51.5%). Forty-seven patients sustained infra-isthmal fractures, while 19 patients experienced supra-isthmal fractures. The postoperative FI ratio was higher in the delayed union group (median 1.67 vs 1.36; p = 0.001) and was the only independent predictor on multivariable analysis ( p = 0.007). A postoperative FI ratio ≥1.43 predicted delayed union with sensitivity 0.79 and specificity 0.66 (area under the curve [AUC] 0.74); delayed union was more frequent when FI ≥1.43 than <1.43 (27/39 [69.2%] vs 7/27 [25.9%], odds ratio [OR] = 6.43). Intraoperative blood loss was associated with univariate testing ( p = 0.013) but not after adjustment; nail-canal ratio, fracture length, and screw-fracture distance were not significant.
Conclusion:
The postoperative FI ratio is a feasible indicator of delayed union in patients who received intramedullary nailing for supra-isthmal or infra-isthmal tibial shaft fractures. A postoperative FI ratio ≥1.43 indicates a significantly higher risk of delayed union. In such cases, it may be recommended that patients undergo prolonged protected weight-bearing and shortened follow-up intervals.
