A 53 yo was placed in stirrups and underwent total abdominal hysterectomy, bilateral salpingo-oophorectomy and lymph node dissection for endometrial cancer. A wound protector/retractor was used to provide exposure. She has a BMI of 62, diabetes and hypertension. On post-op day 2, she has difficulty walking. Her foot is limp and she cannot dorsiflex. She has no other symptoms. The measure that could have prevented this injury is: