BACKGROUND: Involuntary cast-saw burns are attributable to poorly padded casts, cast material, or improper technique. Another factor potentially associated with the risk of injury is the distance between the inner perimeter of the cast and the patient's skin (safety distance). METHODS: Eighty computed tomographic scans of the lower limb following cast application were analyzed. Safety distance was measured above, below, and at the level of the knee and ankle joints at 4 different aspects (posterior, anterior, medial, and lateral). RESULTS: The highest safety distance measured was at the anterior aspect, 5 cm beneath the ankle joint (8.13 ± 3.73 mm). The lowest distance measured was consistently at the posterior aspect at all levels, especially 5 cm below the ankle joint (2.02 ± 1.31 mm). CONCLUSIONS: The anterior aspect of the leg is the safest area to split a cast based on safety distance measurements. Patient and limb position may also affect the safety distance at various areas along the limb.