Osteoarthritis Requiring Joint Replacement

Osteoarthritis is progressive degeneration of synovial joints characterised by loss of articular cartilage, subchondral bone remodelling, osteophyte formation, synovitis and progressive structural deformity.

Joint replacement becomes appropriate when symptoms and disability are no longer adequately controlled by reasonable nonoperative treatment.

The indication is clinical, not simply radiographic.

A patient with severe radiographic osteoarthritis but minimal symptoms does not require arthroplasty.

Conversely, a patient with moderate radiographic disease but major pain and functional restriction may appropriately undergo replacement after alternative diagnoses are excluded.

The most commonly replaced osteoarthritic joints are:

• Hip
• Knee
• Shoulder

Kellgren Lawrence radiographic grading

Grade 0

No radiographic osteoarthritis.

Grade 1

Doubtful joint space narrowing with possible osteophyte formation.

Grade 2

Definite osteophytes with possible joint space narrowing.

Grade 3

Multiple osteophytes, definite joint space narrowing, subchondral sclerosis and possible deformity.

Grade 4

Large osteophytes, marked joint space loss, severe sclerosis and definite bony deformity.

Grades 3 and 4 frequently correspond to advanced structural disease, but radiographic grade alone should not determine surgery.

Pattern classification in knee osteoarthritis

Knee disease can predominantly involve:

• Medial tibiofemoral compartment
• Lateral tibiofemoral compartment
• Patellofemoral compartment
• Multiple compartments

This distribution determines whether a patient could undergo:

• Unicompartmental knee arthroplasty
• Patellofemoral arthroplasty
• Total knee arthroplasty

Symptoms include:

• Load related pain
• Reduced walking distance
• Rest pain in advanced disease
• Night pain
• Stiffness
• Loss of joint movement
• Crepitus
• Progressive varus, valgus or flexion deformity
• Functional loss

Before recommending arthroplasty, establish that the pain arises primarily from the joint.

For hip pain, exclude:

• Lumbar radiculopathy
• Trochanteric pain syndrome
• Hernia
• Vascular claudication

For knee pain, exclude:

• Referred hip pain
• Lumbar radiculopathy
• Inflammatory arthritis
• Infection
• Stress fracture

Pain severity should be interpreted together with the patient\'s functional goals.

For knee osteoarthritis obtain weight bearing radiographs.

Useful views include:

• Standing AP
• Lateral
• Patellofemoral skyline
• Long leg alignment imaging when significant deformity exists

For hip osteoarthritis:

• AP pelvis
• Lateral hip

MRI is generally unnecessary when advanced osteoarthritis is already obvious on plain radiographs and arthroplasty is planned.

Routine serial imaging is not required simply to monitor known osteoarthritis during nonoperative care.

Indication for joint replacement

Refer for arthroplasty when:

• Pain, stiffness or deformity significantly impairs quality of life

and

• Appropriate nonoperative treatment is ineffective, unsuitable or no longer acceptable to the patient.

Once a patient has symptomatic moderate to severe disease, has tried reasonable nonoperative management and has chosen surgery, there is little value in requiring additional arbitrary months of physiotherapy, NSAIDs or injections solely to delay arthroplasty.

Age alone should not determine eligibility.

Obesity increases perioperative risk but is not by itself an absolute contraindication to referral.

Preoperative optimisation

Identify and address modifiable risk where feasible:

• Active infection
• Poor glycaemic control
• Smoking or nicotine use
• Severe malnutrition
• Anaemia
• Uncontrolled cardiovascular disease
• Poor skin integrity
• Active dental or urinary sepsis

Do not operate electively through active systemic infection.

Smoking cessation and improved diabetic control reduce wound and infection risk. Elective arthroplasty can reasonably be delayed for meaningful glycaemic or nicotine optimisation when feasible.

Hip osteoarthritis

Definitive treatment is total hip arthroplasty.

Components include:

• Acetabular shell and liner
• Femoral stem
• Femoral head

Bearing combinations commonly include:

• Ceramic on highly cross linked polyethylene
• Metal on highly cross linked polyethylene

Routine metal on metal total hip articulation is generally avoided because of metal ion and adverse local tissue reaction concerns.

Cemented versus uncemented femoral fixation

Uncemented fixation

Commonly used in:

• Younger patients
• Good proximal femoral bone

Relies on initial press fit followed by biological ingrowth.

Cemented fixation

Particularly useful with:

• Elderly patients
• Osteoporotic bone
• Wide femoral canals
• Poor press fit potential

Hybrid strategies can use a cemented stem with an uncemented acetabular component.

Total knee arthroplasty

TKA replaces diseased:

• Distal femoral surfaces
• Proximal tibial surfaces

with or without patellar resurfacing.

Objectives are:

• Correct deformity
• Restore stable mechanical alignment
• Balance flexion and extension gaps
• Restore joint line
• Maintain patellar tracking
• Achieve stable fixation

Cruciate retaining versus posterior stabilised

Cruciate retaining

Preserves a functional PCL.

Requires:

• Intact PCL
• Correctable deformity
• Balanced flexion gap

Posterior stabilised

PCL is sacrificed and a cam post mechanism provides posterior stability.

Useful when the PCL is deficient or deformity makes reliable retention difficult.

More constrained implants are used for:

• Major collateral ligament deficiency
• Severe bone loss
• Complex revision

Unicompartmental knee arthroplasty

Consider when disease is genuinely isolated to a single tibiofemoral compartment and the remainder of the knee is suitable.

Advantages can include:

• Faster recovery
• More physiological knee kinematics
• Smaller operation

Disadvantages include:

• Progression of arthritis in remaining compartments
• Higher revision risk in some populations

Do not perform UKA in diffuse tricompartmental disease.

Active infection

Active joint infection is an absolute contraindication to primary elective arthroplasty until eradicated.

Previous septic arthritis substantially increases later PJI risk and requires careful preoperative evaluation.

Perioperative antimicrobial prophylaxis

A typical regimen is:

Cefazolin 2 g IV within 60 minutes before incision

or

3 g IV for patients weighing at least approximately 120 kg.

Redose intraoperatively for prolonged operations or major blood loss according to institutional pharmacokinetic protocol.

Use vancomycin selectively for:

• Known MRSA colonisation
• Severe immediate beta lactam allergy where appropriate

Avoid prolonged prophylactic antibiotics after uncomplicated primary arthroplasty.

Tranexamic acid

Tranexamic acid substantially reduces perioperative blood loss in total hip and knee arthroplasty.

A common IV strategy is:

Tranexamic acid 1 g IV around induction or incision

with another dose later according to local protocol.

Topical and oral regimens are also effective.

Assess thrombosis history and renal function before dosing.

VTE prophylaxis

Hip and knee arthroplasty carries substantial venous thromboembolism risk.

Use:

• Early mobilisation
• Mechanical prophylaxis where appropriate
• Pharmacological prophylaxis

Options include:

• Aspirin in selected lower risk patients
• LMWH
• Apixaban
• Rivaroxaban

Choice depends on patient thrombosis and bleeding risk and local arthroplasty protocol.

Rehabilitation

Early mobilisation is a major objective.

After uncomplicated THA or TKA, patients should generally:

• Mobilise on the day of surgery or following day
• Weight bear as tolerated where fixation permits
• Begin structured physiotherapy
• Receive multimodal analgesia

Failure and revision

Major complications include:

• PJI
• Dislocation after THA
• Periprosthetic fracture
• Aseptic loosening
• Polyethylene wear
• Instability
• Persistent pain
• Stiffness
• VTE
• Neurovascular injury

Pain after joint replacement should not automatically be labelled loosening. Always consider infection before elective revision of a painful prosthesis.