The extended SMAS lift and the deep plane facelift use the same natural glide plane between the SMAS and the parotid-masseteric fascia. In both techniques the facial ligaments are disrupted or resected to achieve full mobilisation of the SMAS.
The difference is that in the extended SMAS lift, the skin of the face is detached from the underlying SMAS in a first step before mobilising the SMAS, then SMAS and skin are lifted separately. In a deep plane facelift the facial skin is hardly separated from the underlying SMAS and both layers, SMAS and skin are mobilised and lifted together as a composite flap.