Blood Clots After Surgery

Orthopaedic & Spine Center

 by Dr Jeffrey Carlson MD

Managing Partner of Orthopaedic & Spine Center, Newport News VA

Most patients undergoing orthopaedic surgery have concerns about blood clots  or deep vein thrombosis (DVT) after surgery.  There is certainly a significant risk associated with some surgeries.  Swelling due to lower extremity surgery may also decrease the flow of blood through the veins and lead to clots. The most dangerous concern about blood clots is the possibility for them to travel to the lungs.  Blood clots that travel to the lungs are called pulmonary emboli.   These clots block the blood flow to the lungs, preventing the blood from becoming full of oxygen, which can lead to death.

Hip replacement and knee replacement are both known to have risks for blood clots or that can range up to 25% after surgery if patients are not treated to prevent them. Lower extremity surgery often forces patients to stay off of their feet for a few weeks and be less active than usual.  This inactivity can cause the flow of blood through the veins in the legs to slow and can coagulate, or clot.  All patients with hip and knee replacements are now put on blood thinners for approximately 6 weeks post-surgery or until the patient is moving well enough to avoid the pooling of blood in the legs.

x-ray scan of a hip implant

Hip replacement and knee replacement do present an elevated risk of blood clotting or DVT (Deep Vein Thrombosis) occurring.

Recent Concerns and Press Coverage of DVT

More recently, concerns about risks for blood clots caused by outpatient surgery have been getting some press time. Why?  Most outpatient surgeries are done with the expectation that these patients are well enough to be mobile.  This mobility allows the blood to flow through the veins in the legs, decreasing the likelihood of developing a DVT.  However, while the risk for clots is very low during Outpatient Surgery, there are patients who are more suceptible.

A recent article from the Annals of Surgery revealed that the overall risk of blood clots for outpatient surgery is only 0.15%. The study identified several factors that may increase the risk of blood clots in outpatient surgery, including patients who are pregnant, actively battling cancer, over age 60, overweight with a Body Mass Index (BMI) of 40 or higher.  BMI is a measurement for human body fat based on a person’s height and weight. A healthy, normal BMI is 18.5-25. Other risk factors include an operative time of 120 minutes or more and having arthroscopic or venous surgery.

Clotting Factors and Risk of Blood Clots

Some of these factors can be addressed or improved prior to surgery and therefore, will reduce the patient’s risk.  Most outpatient surgery is done on an elective basis, so if a patient can lose weight or wait to have surgery until after the pregnancy is completed, he or she will reduce the risk of blood clots after surgery.  Obviously, age, type of surgery and length of time in surgery are not factors the patient can control, but trying to be as mobile as possible after surgery will decrease clotting risk.  Placing weight on the legs allows the muscles and joints in the legs to pump the blood back to the heart and increases the lower extremity blood flow.  Many doctors will recommend taking a blood thinner or aspirin after surgery.

Many other outpatient orthopaedic surgeries do not have an increase in the risk for blood clots.  In particular, neck, lower back, and upper extremity surgeries, including shoulder arthroscopy and carpal tunnel surgery, do not have an increased risk for blood clots.  Even though these surgeries do not have a greater chance of blood clots, it is still important for these surgical patients to be mobile and continue to use the extremities in order to more actively pump the blood through the veins.

With communication and proper planning between the patient and physician, understanding and avoiding blood clots can be achieved. It is crucial that a patient follow physician’s orders and strive to be active following surgery to best avoid clotting issues.

Dr. Jeffrey R. Carlson is a Harvard orthopaedic/neurosurgical spine fellow and is Chief-of-Surgery at Bon Secours Mary Immaculate Hospital in Newport News, VA.  He is the Managing Partner of and currently practices at Orthopaedic and Spine Center in Newport News, VA.  For more information or for an appointment, contact OSC at 757-596-1900 or go to