System used to describe intertrochanteric femur fractures. Type 1, stable, nondisplaced single fracture line; type 2, stable, displaced single fracture line; type 3, comminuted (not involving lesser trochanter) with possible instability; type 4, involving lesser trochanter with greater trochanter fragment attached to neck (risk of loss of reduction); type 5, unstable trochanteric fragments (highest loss of reduction).