Orthopaedic Surgery

Case summary
A 76-year-old woman was admitted for an elective right triple arthrodesis and lengthening of the Achilles tendon. Her relevant history included bilateral total knee replacements, a left hip replacement, osteoarthritis, asthma and deep vein thrombosis (DVT). There was no documentation of the patient being on preoperative anticoagulation. 

The procedure took two hours and 45 minutes to complete under general anaesthetic with a popliteal block administered. The tourniquet time was not documented. The anaesthetic notes document the patient was ASA grade II (American Society of Anesthesiologists physical status classification system). 

The limb was immobilised in a below-knee plaster. The patient was transferred to the ward with postoperative analgesia, antibiotic and venous thromboembolic prophylaxis (enoxaparin), and instructions to keep the right leg elevated. A drug chart was not provided for review. The patient encountered some drowsiness related to analgesia in the first 24 hours postoperative. It was documented that she received enoxaparin while in hospital. 

The patient was discharged five days after surgery. No discharge medical information was provided for review. Two weeks later she re-presented to an emergency department by ambulance, with a four day history of increasing shortness of breath, chest tightness and lethargy. A computed tomography scan of the pulmonary artery indicated a saddle pulmonary embolus. Soon afterwards, the patient deteriorated and suffered a cardiac arrest. Despite all efforts, she died the same day.

The coroner’s notes indicate possible confusion regarding enoxaparin administration following discharge, with conflicting accounts arising from nursing staff and the patient’s husband.

Discussion
This 76-year-old patient underwent a right hindfoot arthrodesis to address the deformity and degenerative changes. Initial concerns were raised regarding the patient’s age and the necessity of the surgical procedure. Although she had no severe medical comorbidities, she did have a history of DVT. The patient succumbed to a pulmonary embolus three weeks after surgery. 

Like hip or knee osteoarthritis, degenerative conditions in the foot or ankle can be highly disabling for patients. Arguably the patient’s chronological age is irrelevant to this case. However, a patient’s medical history and ability to manage extended postoperative periods of non-weight-bearing are relevant.

It is the responsibility of the surgeon to:
1)    identify significant medical concerns and involve relevant medical specialists to help stabilise or improve such conditions
2)    ensure the patient understands the extent of the proposed surgery and any relevant risks and possible complications
3)    ensure the patient understands the postoperative limitations (elevate limb, non-weight-bearing) and any treatments necessary to reduce complications (anticoagulation, antibiotics)
4)    ensure the patient has been advised regarding requirement for administration of medications such as enoxaparin.

Concerns exist regarding the patient’s history of DVT and inconsistency in postoperative discharge planning regarding enoxaparin administration. The patient received enoxaparin as an inpatient; however, there is some discrepancy regarding administration following discharge. The coroner’s report noted that documentation suggested the patient and her husband were provided enoxaparin education. This was disputed by the husband. 

It is also relevant that the husband indicated they were unaware of the need to administer enoxaparin until they were at the pharmacy. This raises concerns regarding the reliability of the instructions for enoxaparin administration following discharge. 

Enoxaparin is commonly used following orthopaedic lower limb surgery. Increasing evidence shows that 40mg daily may be too low for patients weighing more than 80–90 kgs, in which case a higher (weight-based) dose should be considered. 

While there is clear evidence in the literature that the use of enoxaparin can reduce the risk of thromboembolism, its effect on reducing fatal pulmonary embolism is less clear. If enoxaparin was administered as prescribed on discharge, then it was unable to prevent the patient’s outcome in this case.

Clinical lessons
•    Patient education—both preoperatively and postoperatively—is extremely important. Surgeons must be aware that elderly patients will struggle with non-weight-bearing and the administration of injections such as enoxaparin.
•    Enoxaparin, while highly effective at reducing thromboembolism, may not reduce the risk of fatal pulmonary embolism. The dose should be adjusted for the patient’s weight.
•    Consideration should be given to any significant medical conditions and these should be investigated preoperatively (e.g. haematologist review) to stratify and reduce risk.
•    Age is no more a contraindication to foot and ankle surgery than it is for total hip or knee replacement.