How is the ML measurement calculated in a transfemoral quad style socket?

In the context of transfemoral quad style sockets, the ML (mediolateral) measurement is important for ensuring proper fit and comfort. The correct method is to take the ischial level circumference, divide it by 3, and then subtract 6mm. This process helps in acquiring the appropriate mediolateral dimension that accommodates the anatomy of the residual limb, particularly the ischial tuberosity and other bone structures.

The rationale behind dividing by 3 is associated with the biomechanical considerations of weight distribution and the need to balance the socket's fit with enough space for soft tissue without causing excessive pressure. Subtracting 6mm helps to account for deformation and movement, ensuring that the socket fits snugly during function while allowing for some soft tissue compression and movement during use.

Understanding the significance of these adjustments is crucial for prosthetic fitting, as they contribute to stability and comfort, minimizing the risk of pressure sores or discomfort during daily activities.