Distal forearm fractures in children: Cast index as predictor of re-manipulation

Abstract

Background: Displaced distal forearm fractures in children have been treated in above-elbow plaster casts since the last century. Cast index (CI) has been proposed as a measure to indicate how well the cast is molded to the contours of the forearm. In this study the CI in post-manipulation radiographs were analyzed to evaluate its relevance to re-angulation of distal forearm fractures in children in different age-groups.

Materials and methods: Out of 174 consecutive cases treated during the study period, 156 patients (114 male and 42 female) with a mean age of 9.8 years (range: 2-15 years) were included in this retrospective radiographic analysis; 18 patients were excluded for various reasons. All patients were manipulated in the operation theater under general anesthesia and a molded above-elbow cast was applied. The CI was measured on immediate post-manipulation radiographs. Children were divided into three groups according to age: group 1: <5 years, group 2: 5-10 years, and group 3: >10 years.

Results: Angulation of the fracture within the original plaster cast occurred in 30 patients (19.2%): 22/114 males and 8/42 females. The mean CI in these 30 patients who required a second procedure was 0.92±0.08, which was significantly more than the mean CI in the other children (0.77±0.07) (P<.001). The mean CI in children who underwent re-manipulation in the group 1 was 0.96, which was significantly higher than that of the other two groups, i.e., 0.90 in group 2 and 0.88 in group 3 (P<.05). A receiver operating characteristics (ROC) curve estimated the cutoff point for intraoperative CI of 0.84 when both the sensitivity and specificity of CI was high to predict re-manipulation for re-displaced fractures of the distal forearm in children in any age-group.

Conclusion: The CI is a valuable tool to assess the quality of molding of the cast following closed manipulation of forearm fractures in children. A high CI (≥0.84) in post-manipulation radiographs indicates increased risk of re-displacement of the fracture in children, especially in those under the age of 5 years and over the age of 10 years.

Keywords: Children; cast index; conservative treatment; forearm fracture.

Figure 1

(a) Pre-manipulation lateral view; (b) pre-manipulation AP view; (c) post-manipulation AP view, with moulded cast showing coronal plane dimension; (d) post-manipulation lateral view, with moulded cast showing sagittal plane dimension (CI = 0.67); (e) 3-weeks post-manipulation showing union in good alignment

Figure 2

(a) Initial AP radiograph in a poorly moulded plaster cast showing coronal plane dimension (CI = 0.96); (b) initial lateral radiograph in a poorly moulded plaster cast showing sagittal plane dimension; (c) post-manipulation AP radiograph in well-moulded cast showing coronal plane dimension (CI = 0.74); (d) post-manipulation lateral radiograph in well-moulded cast showing sagittal plane dimension; (e) lateral radiograph at 3 weeks showing maintenance of alignment

Graph 1

Box and plot showing mean CI in different age-groups in the non-re-manipulated children

Graph 2

Box and plot showing mean CI in different age-groups in the re-manipulated children

Graph 3

Receiver operating characteristics (ROC) curve estimating the CI for the outcome variable, i.e., re-manipulation. At a CI of 0.84 the sensitivity is 85% and specificity is 81%. Area under the curve (AUC) is 0.91 (95% CI: 0.87 to 0.96; P<.001)