What shape should the inferior trim line of a LSO be when analyzing trim lines?

The inferior trim line of a lumbar-sacral orthosis (LSO) should be rounded to accommodate the natural contours of the lower back and to provide comfort while ensuring adequate support. A rounded trim line allows for better distribution of forces across the abdomen and lower back, reducing potential pressure points that can occur with rigid or straight edges. This design also helps in allowing for some flexion and extension while still providing necessary stabilization, making it more effective for patient use.

A straight or flat trim line can lead to discomfort and may restrict necessary movement, causing the patient to feel constrained. Rectangular shapes, while potentially stable, do not conform to the body's anatomy as effectively as rounded edges, which can lead to an improper fit and, ultimately, decreased compliance from the patient. Thus, the rounded inferior trim line serves both functional and comfort purposes in the design of an LSO.