Potential Causes of Loss of Reduction in Supracondylar Humerus Fractures

Background: Recent biomechanical studies have evaluated the stability of various pin constructs for supracondylar humerus fractures, but limited data exist evaluating these constructs with clinical outcomes. The goal of this study was to review the surgical management of Gartland type II and III supracondylar fractures to see whether certain pin configurations increase the likelihood of loss of reduction (LOR). Methods: A total of 192 patients treated with a displaced supracondylar fracture were evaluated. LOR was defined as a change >10 degrees in either plane from its intraoperative reduction. Fracture classification, comminution, and location were documented. Intraoperative films were assessed for number of pins, location of pins both medial and lateral, bicortical purchase, pin spread at the fracture site, and pin divergence. Results: Ninety-four patients had type II fractures, and 98 had type III fractures. The average patient age was 5.7 +/- 2.3 years. Extension-type injuries represented 98% of fractures. LOR was noted in 4.2% of patients. Age (P=0.48) and sex (P=0.61) were not associated with LOR. Fracture characteristics including type (P=0.85), comminution (P=0.99), and location (P=0.88) were not associated with LOR. Fractures treated with lateral-entry pins only or with 2 pins were no more likely to lose reduction (P=0.88 and 0.91). Pin spread at the fracture site was associated with LOR with less spread increasing the likelihood of failure (P=0.02). Fractures that lost reduction had an average pin spread of 9.7mm [95% confidence interval (CI), 6.3-13.2) or 28% (95% CI, 26-31) of the humerus width compared with 13.7mm (95% CI, 13-14.4) or 36% (95% CI, 13-60) of the humerus width for those that remained aligned. Conclusions: LOR after percutaneous fixation of supracondylar fractures occurs relatively infrequently at a rate of 4.2%. This study suggests that pin spread is an important factor associated with preventing LOR with a goal of pin spacing at least 13mm or 1/3 the width of the humerus at the level of the fracture. Level of Evidence: Retrospective study; level II.