Does ambulation immediately following an episode of deep vein thrombosis increase the risk of pulmonary embolism?

A 68-year-old woman who had no known musculoskeletal or neuromuscular impairments fell in her home and sustained a fracture of the left femoral neck. The fracture was treated surgically by replacement of the femoral head and neck (hemiarthroplasty), and the patient began physical therapy in her hospital room the day after surgery. The initial physical therapy interventions included exercises to increase range of motion of the hip and to increase force of the quadriceps femoris and hip abductor muscles. In preparation for ambulation, standing and weight-shifting activities also were instituted at the bedside on the day after surgery. On the second day after surgery, I saw the patient in the physical therapy department, where she began ambulation using parallel bars, with weight bearing to tolerance on the left lower extremity. By the third postoperative day, she was ambulating with a walker for distances of up to 12 meters (40 feet). She did not need any support or assistance, but I provided instruction occasionally to ensure proper technique and safety. The patient continued to progress well until she developed sharp pain in her left calf. Subsequent testing using Doppler ultrasound revealed a deep vein thrombosis (DVT). Following surgery, the patient had been receiving a prophylactic dose of the antithrombotic medication enoxaparin (Lovenox) (30 mg administered subcutaneously every 12 hours). When she developed the DVT, the dose of enoxaparin was increased according to her body weight (75 kg) so that she was receiving an antithrombotic treatment dose of 75 mg every 12 hours (ie, 1 mg of enoxaparin per kg of body weight administered subcutaneously every 12 hours). The patient also was supposed to be wearing lower-extremity compression stockings after surgery, but she had apparently been removing the stockings from time to time because they were uncomfortable. She therefore was informed about …