General Surgical Risks — What They Really Mean

Part of The Joint Replacement Guide — Phase 3: Understanding the Risks · Article 13 of 44 · Hip & Knee

Key Points

  • Every operation has potential benefits and risks. Understanding both is an important part of deciding whether surgery is right for you.
  • General risks of major surgery include bleeding, infection, blood clots and complications affecting the heart, lungs or anaesthetic.
  • Serious complications after planned hip or knee replacement are uncommon, but they are not impossible.
  • Published figures describe averages across groups. Your own risk may be higher or lower depending on your health, the operation and other individual factors.
  • Your surgical and anaesthetic teams should explain the risks that are particularly relevant to you and answer your questions before you consent to surgery.

Understanding Risk Figures

Risk can be described in several ways—for example, “1%”, “1 in 100” or “uncommon”. These all describe the same approximate frequency, but no figure can predict exactly what will happen to an individual.

Reported complication rates also vary because studies may:

  • use different definitions;
  • include different types of hip or knee replacement;
  • follow patients for different lengths of time; and
  • include patients with different health conditions.

Where possible, ask for risk to be explained using absolute numbers, such as “how many people out of 100 or 1,000”, and over a stated period.

Bleeding and Blood Transfusion

Some bleeding is expected during and after joint replacement. This can lead to bruising, swelling and a temporary fall in the blood count.

Tranexamic acid is normally given during primary hip or knee replacement unless there is a reason it is unsuitable. It helps reduce blood loss and the likelihood of needing a transfusion.[1,2] Surgical technique, treating anaemia before surgery and careful management of blood-thinning medicines also help reduce risk.

Some patients still require a blood transfusion. The likelihood depends on factors including the procedure, blood count before surgery and amount of blood lost. Transfusion has its own uncommon risks, which should be discussed if it becomes necessary.

Occasionally, blood collects beneath the wound and forms a haematoma. Most bruising and swelling settle without further treatment, but a large or troublesome haematoma may require additional assessment or, rarely, another procedure. Returning to theatre specifically to control continuing bleeding is uncommon.

Do not stop prescribed anticoagulant or antiplatelet medication yourself. The team will give you an individual plan.

Infection

Infection may involve only the skin and tissues around the wound or extend more deeply to the artificial joint.

Superficial wound problems

Redness, warmth or a small amount of wound leakage does not always mean that an infection is present. However, persistent or worsening redness, increasing pain, pus, continued drainage, wound separation, fever or feeling unwell requires prompt assessment.

Some superficial infections can be treated with antibiotics, but treatment should not be assumed or started without clinical review. Where it is safe to do so, the team may need to examine the wound and take appropriate samples before antibiotics are given.

Deep or periprosthetic joint infection

A periprosthetic joint infection involves the tissues around the implant. It is much less common than minor wound concerns but is more serious and may require prolonged antibiotics and one or more operations.

The National Joint Registry describes infection after primary hip replacement as typically affecting fewer than 1 in 100 patients. Figures around 1 in 100 are also commonly quoted for deep infection after knee replacement, although the precise risk depends on how infection is defined and how long patients are followed.[3,4]

Risk may be influenced by factors including diabetes control, smoking, nutritional health, skin problems, previous surgery and body weight. These factors should inform individual preparation and planning rather than be treated as automatic reasons to deny referral.

Measures used to reduce infection include:

  • antibiotics around the time of surgery;
  • skin preparation and sterile operating procedures;
  • careful wound care;
  • management of relevant health conditions; and
  • prompt investigation of concerning wound symptoms.

No prevention method removes the risk completely.

Blood Clots

Venous thromboembolism, or VTE, includes:

  • deep-vein thrombosis (DVT): a blood clot, usually in a deep vein of the leg; and
  • pulmonary embolism (PE): a clot that travels to the lungs, where it can interfere with breathing and may be life-threatening.

Joint replacement and reduced mobility temporarily increase the risk of VTE. Prevention begins with assessing both your clotting risk and your risk of bleeding.

Depending on that assessment, prevention may include:

  • helping you stand and walk on the day of surgery where possible, or within 24 hours;
  • foot and leg exercises;
  • intermittent compression pumps or appropriately fitted stockings; and
  • medication such as aspirin or an anticoagulant for a specified period.

The medicine and duration differ between hip and knee replacement and between patients. NICE recommends prophylaxis when the risk of VTE outweighs the risk of bleeding.[5] Follow your own hospital’s instructions and do not change or stop the medication without advice.

Seek urgent medical advice for new or worsening one-sided calf or leg pain, swelling, warmth or discolouration. Call 999 for sudden breathlessness, chest pain, coughing up blood or collapse, as these may indicate a pulmonary embolism.[6]

Anaesthetic Complications

Anaesthetic effects depend partly on whether you have a spinal or general anaesthetic and on the pain-relief techniques used.

Temporary effects can include:

  • nausea or vomiting;
  • shivering;
  • itching;
  • dizziness;
  • headache;
  • temporary difficulty passing urine; and
  • a sore throat or hoarse voice after some general anaesthetics.

Less common but more serious complications include severe allergic reaction, breathing difficulties, heart problems, nerve injury and awareness during general anaesthesia. Serious harm caused directly by anaesthesia is rare.[7]

Your anaesthetist will consider your health, medicines, preferences and the planned operation. They should explain the options and risks that are relevant to you rather than relying only on general population figures.

Heart, Lung and Other Medical Complications

Major surgery places temporary stress on the body. Possible medical complications include chest infection, worsening of an existing health condition, heart attack, stroke, kidney problems, urinary retention and, particularly in some older or frail patients, temporary confusion or delirium.

The likelihood is influenced by general health, frailty and existing heart, lung, kidney or neurological conditions. Preoperative assessment helps the team identify these risks and plan monitoring, medication and postoperative care.

Nerve, Blood-Vessel and Tissue Injury

Major injury to a nearby nerve or blood vessel is uncommon but possible. Smaller skin nerves are routinely affected by an incision, so an area of altered sensation or numbness close to the scar is relatively common and may persist.

The particular nerves, blood vessels and other structures at risk differ between hip and knee replacement and should be discussed in the procedure-specific articles.

Pressure injury to the skin or nerves can also occur from positioning during a prolonged operation, although precautions are taken to reduce this risk.

Risk of Further Surgery

A complication such as deep infection, significant bleeding, fracture, dislocation or implant problem may require another procedure. The reasons and likelihood differ between hip and knee replacement.

Further surgery may be relatively limited or may involve removal or replacement of some or all of the implant. Your surgeon should explain important procedure-specific risks separately.

Risk to Life

Death following planned primary hip or knee replacement is rare, but the risk is not zero. When it occurs, it is usually related to a serious surgical or medical complication rather than the anaesthetic alone.[7]

A single general percentage is not appropriate for every patient. Age, frailty and existing medical conditions can substantially affect individual risk. Your team may use a validated risk-assessment tool and should explain the result in understandable terms if this would help your decision.

How Risks Are Reduced

Contemporary joint-replacement pathways use several measures together, including:

  • assessment and management of relevant health conditions;
  • treatment of anaemia where present;
  • antibiotics and infection-prevention procedures;
  • tranexamic acid to reduce blood loss;
  • individualised VTE prevention;
  • appropriate anaesthetic and pain-relief techniques;
  • early mobilisation and rehabilitation; and
  • monitoring during and after surgery.

These measures have improved safety and recovery, but they cannot guarantee that a complication will not occur.

The Bottom Line

For most patients, hip or knee replacement proceeds without a serious complication and provides substantial improvement in pain and function. Informed consent nevertheless requires an honest discussion of material risks—including risks that may be uncommon but would matter greatly to you.

Before deciding, you should have an opportunity to discuss:

  • the expected benefits;
  • reasonable alternatives, including no surgery;
  • common complications;
  • serious complications, even when uncommon;
  • risks that are particularly relevant to your health or circumstances; and
  • what would happen if a complication occurred.

This article provides general information and does not replace individual advice or the consent discussion with your surgical and anaesthetic teams. Contact your hospital using the instructions provided if you develop concerning symptoms after surgery. Call 999 for severe breathing difficulty, chest pain, collapse or another medical emergency.

References

  1. National Institute for Health and Care Excellence. Joint replacement (primary): hip, knee and shoulder. NICE guideline NG157. London: NICE; 2020. Section 1.4. Available from: https://www.nice.org.uk/guidance/ng157/chapter/Recommendations
  2. National Institute for Health and Care Excellence. Joint replacement quality standard: statement 3—tranexamic acid during hip and knee replacement. NICE quality standard QS206. London: NICE; 2022. Available from: https://www.nice.org.uk/guidance/qs206/chapter/Statement-3-Tranexamic-acid-during-hip-and-knee-replacement
  3. National Joint Registry. Hip replacement: information for patients. Available from: https://www.njrcentre.org.uk/patients/hip-replacement/
  4. Health Research Authority. I-DECIDE: Making informed decisions before knee replacement. London: HRA. Available from: https://www.hra.nhs.uk/planning-and-improving-research/application-summaries/research-summaries/i-decide-making-informed-decision-before-knee-replacement/
  5. National Institute for Health and Care Excellence. Venous thromboembolism in over 16s: reducing the risk of hospital-acquired deep-vein thrombosis or pulmonary embolism. NICE guideline NG89. London: NICE; 2018, updated 2019. Recommendations 1.11.5–1.11.10. Available from: https://www.nice.org.uk/guidance/ng89/chapter/Recommendations
  6. NHS. Complications of a hip replacement. Available from: https://www.nhs.uk/tests-and-treatments/hip-replacement/complications-of-a-hip-replacement/
  7. Royal College of Anaesthetists. Risks and side effects: death and serious harm. London: RCoA. Available from: https://www.rcoa.ac.uk/patients/patient-information-resources/anaesthesia-risk/death-serious-harm

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