Total Hip Replacement via Direct Anterior Approach – What are the Risk Factors?
Dr Chien-Wen Liew – Adelaide Orthopaedic Surgeon – Anterior Approach Specialist.
The direct anterior approach for total hip replacements is a safe, and effective method for performing a total hip replacement. It is one of a variety of approaches to the hip used to perform a total hip replacement safely, and has been used for over 30 years. Whilst it has an extremely favourable risk profile, like all operations, there are risks. Some of these are unique to the direct anterior approach, whilst others are likely to be reduced due to the internervous and inter muscular approach. These are detailed below.
Bleeding: Blood loss in any major surgery is inevitable, but in large operations can result in the requirement for a blood transfusion. The rate of blood transfusion requirement after a hip replacement performed via the direct anterior approach is 1%, unless you have other conditions that cause you to bleed more, or are on a blood thinner. It is important that you disclose all medications you are on to your surgeon, including any natural remedies such as Ginger, Glucosamine and Fish oil. These medications can cause more bleeding. If you bleed more than expected, you may require a blood transfusion. 99% of patients will not require a blood transfusion. Banking your own blood is a possibility, but is unlikely to be required.
Infection: A risk of infection is present anytime the skin is cut. For a hip replacement, the national average is approximately 1-2%. This is dependent on many factors. If you have other risk factors such as diabetes, being a smoker, or are immunocompromised in any way (recent chemotherapy, chronic steroid use), you may need more antibiotic cover. After your total hip replacement, you are always put on intravenous antibiotics for 24 hours. This reduces your risk very low.
Dislocation: The worldwide risk of dislocation ranges from .5% to 10% depending on what series is being studied and over what period of time. It is generally accepted that the rate of dislocation yearly is around 1-2%, however many factors can change this. The anterior approach has been suggested to be more stable than other approaches as no muscles are cut, and the surrounding tissues are therefore not compromised. Stability therefore does not require muscles to heal back onto the bone to reach their maximal stability. In the anterior approach, there are no post operative restrictions, within reason. This means that you can sit in a normal chair, normal toilet seat, cross your legs, and bend down to pick things up without major risk of dislocation. There are patient factors that can increase the risk of dislocation, such as nerve palsies, parkinson’s disease, hip replacement for neck of femur fractures, muscle weakness, and poor balance and muscle tone. A possible solution to this is using a prosthesis called a Dual Mobility, which has a lot more stability than a normal hip replacement. This is used when patients have major risk factors for dislocation. In general, the direct anterior approach has one of the most favourable risk profiles for dislocation.
DVT/PE: Deep Venous Thrombosis and Pulmonary Embolism can occur after total hip and knee replacements or any other operation. This is due to a deep blood clot which occurs due to prolonged surgery, or lying in bed for long periods of time, or due to patient factors that can cause a higher risk of developing blood clots. A family history of blood clots is a large risk factor, as is a prior history of having had a DVT or PE from surgery. Dr Chien-Wen Liew uses multiple modalities to decrease the risk of blood clots, in accordance with worldwide experience. He uses a combination of mechanical methods and pharmacological agents, whilst keeping the profile as safe as possible to avoid unnecessary bleeding from your operation. You will receive special stocks called TED stocks, which must be worn 24/7 for 2 weeks. You will have foot pumps placed onto your feet immediately after surgery which act to pump blood around your body whilst you recover. You will also start a pharmacological agent the day after your surgery. If a blood clot is suspected, an ultrasound is ordered. The symptoms of a blood clot include: Worsening calf pain with swelling or redness, Shortness of Breath, cough with blood staining. This is an emergency and requires relatively emergent investigation and treatment. A below knee DVT can be treated without major issues, as a below knee DVT is generally much lower in risk than an above knee DVT.
Nerve damage: All approaches to the hip can potentially damage a nerve. The nerve that is damaged is different depending on which approach is performed. For the posterior approach (Where muscles are released from the bone), the only nerve at risk is the sciatic nerve, which has a rate of injury of approximately 1%. When this nerve is damaged, the symptoms can range from pain down the back of the leg, to a foot drop. This can be temporary, or permanent. With the direct anterior approach, the nerve that can be damaged is the lateral femoral cutaneous nerve to the thigh. This does not supply any muscle, and therefore no muscle power loss will occur. The worst case scenario is a loss of sensation on the side of the thigh in a patch of skin the size of a hand. In most cases, this comes back by the 3 month mark. When it doesn’t, it does not usually cause any functional issues.
Fracture: Whenever an implant is placed into the bone, the bone can break. This may occur if the bone is very soft, as is the case with severe osteoporosis. When the bone is very soft, a surgeon may decide to use cement instead. Dr Liew uses cement to fix the acetabulum or femoral component when the bone seems soft. A fracture can occur during surgery or after surgery. In most cases, a major fracture requires further surgery. A small fracture to the greater trochanter can be treated non operatively, as the full soft tissue sleeve is left intact. This fracture almost always heals without intervention, and slows the recovery after a total hip replacement by 6-8 weeks. Whilst a fracture of the greater trochanter is rare, it usually occurs within the first 6 weeks, but is not a long term functional concern.
Loosening: When an implant has been in the body for a long time, it can become loose. This is seen after many decades and it is accelerated in some cases such as in a chronic, low grade infection, or when there is subtle movement of the stem or cup in the bony bed. It also occurs when there has been wear of the plastic liner over time, as the body tries to remove the worn particles, and creates an inflammatory response which degrades bone. Dr Liew believes in following his total hip and total knee replacements for ever, so that issues like this can be identified early. A liner exchange can be performed if there is wear. The same approach to the hip be performed, so no muscles are detached for the subsequent surgery. When a prosthesis is loose, it becomes a high risk for bony fracture. One of the hall marks of a loose prosthesis is pain when you start to walk, which goes away after a few steps. In this case, the implant should be removed and replaced after assessing the potential bony loss. Often, bone graft is required. Loosening should only occur after decades, rather than a few years, unless there are other issues.
Whilst this is a list of the more common complications (Which overall are very rare), there my still be other complications that can occur from other aspects of your treatment, such as the anaesthetic or during rehabilitation. If you feel like you have one of these complications, it is best to make an appointment to see your orthopaedic surgeon early, rather than to leave it too long. In the case of suspected infection, it is best to avoid taking antibiotics, and to see an orthopaedic surgeon as quickly as possible.
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