Lower limb arthroplasty is a significant innovation of orthopaedic surgery, allowing improved function and pain relief for patients with hip and knee disease. They are a common elective surgical procedure.
Total Knee Replacement (TKR)
The most common indication for TKR is osteoarthritis of the knee - this may be primary or secondary (from previous trauma). Other indications include:
NICE recommends consideration of TKR for patients whose symptoms have a significant impact on their quality of life and are not improved by non surgical management. Assessment will involve:
History of symptoms
Imaging - plain films, MRI
Arthroscopy - more common on younger patients as investigation
Outcomes are generally very good with appropriate patient selection. Joint failure at 12-15 years is around 5%. TKR is notably more painful than THR.
As with TKR, in the elective setting this is commonly done to treat degenerative or inflammatory arthritis. This is in the setting of failure of medical treatment and significant impact on the patient’s quality of life.
Around 1 in 8 patients require hip revisions in 10 years, generally due to the effects of wear on the replacement.
Knee Arthroplasty There are 3 general types of replacement:
Unicompartmental knee replacement
Unconstrained bicompartmental knee replacement
Constrained bicompartmental knee replacement
Unconstrained bicompartmental knee replacement is the most common form of TKR. The femoral component is metal, whilst the tibial component is metal with a polyethylene cushion.
There are a wide range of different joint types available. Surgical techniques are undergoing constant change e.g. cementless. A tourniquet is generally employed intraoperatively to reduce blood loss.
Hip Arthroplasty The surgical technique can involve:
Total hip replacement (THR)
Conventional - replacement of femoral head and neck
Resurfacing - replacement of the surface of the femoral head
A number of surgical techniques are described. The vast majority are cemented, and these have better outcomes. Hip resurfacing may be employed in younger patients who are likely to outlive the lifespan of a joint replacement.
Hemiarthroplasty is usually reserved for patients with neck of femur fractures who have:
Poor general health
Hip The hip has 3 main sources of sensory innervation;
Femoral nerve - via nerve to rectus femoris (L2,3,4)
Obturator nerve - anterior division (L2,3,4)
Sciatic nerve - via nerve to quadratis femoris (L4,5, S1,2,3)
The skin is supplied primarily by the lateral cutaneous nerve of the thigh. There is some variable cutaneous input from T12.
Knee The knee has 3 main sources of sensory innervation:
Femoral nerve - anterior aspect of the joint capsule via nerve to vastus medialis (L2,3,4)
Sciatic nerve - posterior aspect of joint capsule and all other intra-articular structures - genicular branches of tibial and common peroneal nerves
Obturator nerve - posterior division
The skin is primarily innervated by the femoral nerve. The skin on the medial aspect of the knee is innervated by the obturator nerve in under 40% of people.
Regional anaesthesia is sometimes used for postoperative analgesia in these patients. Options include: Hip arthroplasty:
Lumbar plexus block - most effective but challenging and with higher risks
Femoral nerve block - decent analgesia contribution but only one component of hip innervation
Fascia iliaca block - easy and fairly effective
Femoral nerve block - good analgesia but motor blockade a problem
Sciatic nerve block - better analgesia when added to femoral
Lumbar plexus block
The enhanced recovery after surgery (ERAS) approach is now commonly employed in lower limb arthroplasty. Many of the aspects are very applicable to this form of orthopaedic surgery. The general principles of ERAS are discussed elsewhere.
Patient selection Appropriate selection of patients should identify those who are less likely to fail to meet the demands of ERAS, although the range of suitable patients is increasing. This includes patients who are:
Have stable, optimised comorbidities
Patients who may have challenges with the ERAS approach include:
Difficult preoperative pain control e.g. regular opioid use
Poor social support
Preoperative preparation Full engagement with the patient is an essential part of preparation. A clear understanding of what the pathway involves can help with an understanding of the importance of different aspects of care e.g. early mobilisation. Joint schools can provide education to patients.
Optimisation of comorbidity should be achieved in the community prior to admission. Anaemia should be treated to improve outcomes. Other common comorbidity that should be optimised includes diabetes and hypertension.
As with major colorectal surgery, aspects relating to the pre admission include:
Admission on day of surgery - improve sleep and reduce anxiety
Minimise fasting times - reduce dehydration
Carbohydrate drinks - reduce protein catabolism
The goals of anaesthetic technique are to facilitate the goals of ERAS, namely reduced stress response, and early mobilisation. Whilst previously, less emphasis was given to the early mobilisation, techniques are being modified to help facilitate this.
Neuraxial anaesthesia This is the common technique for anaesthesia. This approach (spinal or epidural anaesthesia) has several theoretical benefits, with some clinical evidence:
Reduced post op pain
Reduced post op opioids
Reduced VTE risk
There is often an avoidance of neuraxial opioids because of the adverse effects (respiratory depression, confusion) with longer acting analgesia being achieved by other methods. Sedation can be employed alongside this method.
Analgesia Multimodal analgesia is employed to improve patient comfort, minimise the stress response and optimise postoperative mobilisation. This often starts with premedication to allow adequate loading:
Gabapentin e.g. 300mg
NSAIDs have significant analgesic benefit here, but this is usually a more elderly population with increased susceptibility to their adverse effects. If there are no hard contraindications, a short course in commonly used.
Intraoperative ketamine (e.g. 25-50mg) is commonly employed to optimise postoperative analgesia through its NMDA receptor actions.
Regional blocks have been used in this surgery. Concern in the ERAS setting relate to the impairment of postoperative mobilisation cause by the associated motor blockade. This is particularly true of sciatic nerve blocks for TKR. Low dose femoral nerve blocks are sometimes used.
Large doses of local infiltration of local anaesthetic agent are employed instead, as described by Kerr and Kohan. Large volumes are infiltrated in the joint and surrounding tissues. An example is 2mg/ml ropivacaine. Sometimes wound catheters may be left in to allow continuous infusion of LA agent postoperatively. This is more common in TKR, which are more painful than THR.
Continuation of multimodal analgesia should occur postoperatively:
Regular NSAID (short course)
Gabapentin e.g. 300mg bd
Opioids are still generally required. Oxycodone is commonly used in this cohort:
Oxycodone MR - 5-20mgbd
Oxycodone immediate release prn
Other Catheterisation is generally avoided. With avoidance of intrathecal opioids, the rate of urinary retention is low.
Tranexamic acid is commonly used to reduce blood loss. Doses of 10-15mg/kg may be given. Care is needed in patients at particularly high risk of VTE.
Fluid management is another key area of ERAS. Excessively positive or negative balances are both detrimental. Invasive measures of fluid balance assessment are less commonly employed in this setting than colorectal surgery, because of the lack of arterial lines or oesophageal doppler (patient is awake). A relatively restrictive fluid regime (<2L intraop) appears to be preferable to a liberal one. Blood loss is rarely a problem in TKR (with the torniquet).
Optimal prophylaxis against PONV is essential to enable a rapid return to oral intake. Risk stratification e.g. Apfel score, can help with this.
Active warming strategies should be employed.
Continuation of a multimodal analgesia regime is important as listed above. A ‘rescue plan’ is important to have in place for patients who have failure of the initial analgesia.
Mobilisation will occur early. Avoidance of impeding lines will aid this. As such, catheters, IV infusions and wound drains are all avoided where possible. The goal is often to mobilise on the day of the operation e.g. mobilise to the toilet, with full mobilisation the following day. Physiotherapist input with this is very helpful.
Patients are at high risk of venous thromboembolic (VTE) disease postoperatively. Appropriate mechanical and pharmacological prophylaxis is essential.
Blood loss can be significant in hip arthroplasty, so Hb measurement postoperatively is important.
Bone cement implantation syndrome
Orthopaedic complications include:
Links & References
Place, K. Scott, NB. Enhanced recovery for lower limb arthroplasty. CEACCP. 2014. 14(3):95-99.
Grant, C. Checketts, M. Analgesia for primary hip and knee arthroplasty: the role of regional anaesthesia. CEACCP. 2008. 8(2):56-61