Effect of Side Struts on the Strength of Long Arm Plaster Splints: A Biomechanical Study.

BACKGROUND: There are multiple methods of achieving upper extremity immobilization after pediatric elbow injuries; however, no biomechanical study has established an optimal construct. The goal of this study was to compare the strength of commonly used long arm splints and to evaluate the effect of reinforcing plaster splints with side struts.

METHODS: Five categories of long arm posterior slab splints were tested: 4-inch plaster without side struts, 4-inch plaster with a medial side strut, 4-inch plaster with medial and lateral side struts, 5-inch plaster without side struts, and 4-inch fiberglass splint material without side struts. There were 4 splints in each group. As a control, 4 half fiberglass long arm casts were also tested. Each splint or cast was mounted on a single-column tensile tester and a 3-point bending load was applied to simulate an extension moment at the elbow. The maximum load before failure was measured and an ANOVA model was used to analyze the differences between groups. Additionally, a retrospective chart review was performed of pediatric patients who were immobilized postoperatively in a long arm plaster splint with side struts. We collected data on patient age, type of fracture, time from splint application in the operating room to removal in clinic, length of follow-up, and any complications.

RESULTS: The 4-inch plaster splints reinforced with 2 struts had the highest average maximum load to failure (731±143 N), which was significantly higher than the 4-inch plaster splints with one strut (505±48 N) (P=0.01) and the 4-inch plaster splints without struts (100±10 N) (P<0.001). The half fiberglass casts failed at an average maximum load of 655±96 N, however there was no statistically significant difference compared with 4-inch plaster splints with 2 struts (P=0.10). The 5-inch plaster splints without side struts failed at a greater average maximum load (341±110 N) compared with the splints constructed with fiberglass material without side struts (233±61 N) (P=0.03). A total of 140 patients were identified in the retrospective review. Splint-related complications occurred in 2 patients.

CONCLUSIONS: The addition of both 1 and 2 side struts to a 4-inch long arm plaster splint significantly increased the load to failure. The strength of 4-inch plaster splints with 2 side struts was comparable to that of half fiberglass casts.

LEVEL OF EVIDENCE: NA (biomechanical study).