Postoperative ileus: This condition is a common cause of upper abdominal pain after surgery, including orthopedic procedures. It involves a temporary paralysis of the intestinal muscles, leading to a buildup of food, fluids, and gas, causing discomfort and pain.

Gastroesophageal reflux disease (GERD): Increased intra-abdominal pressure from surgery or immobility can exacerbate GERD symptoms, leading to upper abdominal pain.
Constipation: Postoperative constipation is common due to pain medications, immobility, and changes in diet, which can cause abdominal pain.
Musculoskeletal pain: Direct trauma or strain to the abdominal muscles during surgery can cause pain, as can the positioning on the operating table.

Pulmonary embolism: Although it primarily presents with respiratory symptoms, pulmonary embolism can sometimes cause upper abdominal pain, especially if it leads to right ventricular strain affecting liver capsule stretching.
Myocardial infarction: Cardiac events can manifest as upper abdominal pain, especially in women, diabetics, or the elderly, due to referred pain.
Peptic ulcer disease: Stress from surgery can lead to the development or exacerbation of peptic ulcers, causing severe abdominal pain.
Hepatic or splenic injury: Rare but possible, especially if the patient experienced trauma or had a complicated surgical procedure.

Pancreatitis: Can be triggered by various factors including certain medications, gallstones, or direct trauma during surgery.
Cholecystitis: Inflammation of the gallbladder, which could be precipitated by the surgical stress response or immobility leading to gallstone formation.
Hepatic vein thrombosis: A rare condition that could occur in the postoperative period, especially in patients with hypercoagulable states.
Abdominal compartment syndrome: A life-threatening condition that can occur after significant trauma or surgery, leading to increased pressure within the abdominal cavity.