What are the considerations for patellofemoral arthroplasty (PFA) in an older patient with severe patellofemoral joint osteoarthritis who has not responded to conservative management?

Patellofemoral Arthroplasty for Severe Isolated Patellofemoral Osteoarthritis

Patellofemoral arthroplasty (PFA) is a viable surgical option for older patients with severe isolated patellofemoral osteoarthritis who have failed conservative management, offering bone preservation and faster recovery compared to total knee arthroplasty, with 5-year and 10-year survivorship rates of 91.7% and 83.3% respectively. 1

Patient Selection Criteria

The success of PFA depends critically on strict patient selection. 2 Proceed with PFA when the following conditions are met:

Indications

• Isolated symptomatic patellofemoral osteoarthritis with bone-on-bone Iwano grade 4 changes on imaging 2
• Absence of significant tibiofemoral compartment disease on weight-bearing radiographs 3, 2
• Failed conservative management including structured exercise therapy, weight loss, and pharmacologic interventions for 3-6 months 4
• Trochlear dysplasia is the preferred indication and yields the best outcomes 2
• Posttraumatic osteoarthritis following patellar fracture is acceptable 3, 2

Absolute Contraindications

• Multicompartment arthritic degeneration involving tibiofemoral compartments 3, 2
• Significant lower limb malalignment 2
• Inflammatory arthropathy 5
• Lack of surgeon experience with patellofemoral arthroplasty or extensor mechanism realignment 2

Relative Contraindications

• Risk factors for progressive tibiofemoral osteoarthritis 2
• Severe patellar thinning (consider total knee arthroplasty without patellar resurfacing instead) 6

Age-Based Decision Algorithm

For younger patients (<50-60 years) with isolated patellofemoral osteoarthritis, PFA is preferred over total knee arthroplasty because it preserves bone stock, maintains ligamentous proprioception, allows faster recovery, and delays the need for total knee arthroplasty. 6, 1

For older patients (>60-65 years) with isolated patellofemoral osteoarthritis, total knee arthroplasty is generally preferred due to more predictable outcomes and lower revision rates, though PFA remains an option in carefully selected cases. 6

Expected Outcomes and Complications

PFA demonstrates excellent or good results in 88-94% of appropriately selected patients at medium-term follow-up. 3 The most recent data shows:

• 5-year survivorship: 91.7% 1
• 10-year survivorship: 83.3% 1
• Annual revision rate: 2.18% 1

The most common reason for revision is progression of tibiofemoral arthritis, not mechanical failure of the implant. 3, 1 When revision to total knee arthroplasty becomes necessary, it can be performed successfully with minimal bone loss using primary TKA implants and instrumentation. 1

Preoperative Optimization

Before proceeding with PFA, ensure the following optimization steps are completed:

• Weight loss to BMI <30 if overweight 4
• Smoking cessation at least 1 month prior to surgery 7
• Discontinuation of narcotic pain medications 7
• Optimization of diabetes control (HbA1c <7.5%) 7
• Completion of structured quadriceps and hip strengthening exercises 4

Surgical Considerations

Modern implant designs and improved surgical techniques have significantly enhanced PFA outcomes compared to earlier generations. 1 Key technical points include:

• Accurate assessment and correction of patellar malalignment or subluxation at the time of surgery 3
• Consider concurrent tibial tubercle osteotomy if indicated for alignment correction 2
• Use of tranexamic acid to minimize blood loss 7
• Neuraxial anesthesia is recommended 7

Postoperative Management

• Formal physical therapy or unsupervised home exercise are equally acceptable options based on patient preference and resources 7
• Full weight-bearing is initiated immediately postoperatively 7
• Continuous passive motion machines are not necessary 7

Critical Pitfalls to Avoid

The most common cause of PFA failure is poor patient selection, specifically performing PFA in patients with unrecognized tibiofemoral compartment disease. 2 Additional pitfalls include:

• Failing to obtain weight-bearing radiographs in all three compartments (AP, lateral, and Merchant views) preoperatively 5
• Proceeding with PFA when CT or MRI reveals occult tibiofemoral disease 7
• Ignoring patellofemoral malalignment or excessive tibial tubercle-trochlear groove (TT-TG) distance 5, 2
• Performing PFA without adequate surgical experience in extensor mechanism procedures 2
• Operating on patients with inflammatory arthropathy or multicompartment disease 3, 2

When to Choose Total Knee Arthroplasty Instead

Choose total knee arthroplasty over PFA when:

• Patient age >65 years with lower activity demands 6
• Any radiographic evidence of tibiofemoral compartment involvement 7, 2
• Severe patellar thinning is present 6
• Patient has risk factors for rapid progression of tibiofemoral osteoarthritis 2