Patellofemoral Arthroplasty: An Effective Surgical Option for Isolated Knee Arthritis

Understanding Patellofemoral Joint Anatomy

The patellofemoral joint refers to the articulation between the back of the patella (kneecap) and the trochlea, a groove at the distal end of the femur (thighbone). As the knee flexes and extends, the patella glides up and down within this trochlear groove. A smooth cartilage covers the patella and trochlea, enabling the bones to move smoothly against each other during knee motion.

In some individuals, this cartilage breaks down, resulting in patellofemoral arthritis. Pain behind or around the kneecap is the primary symptom, especially when bending the knee or going up and down stairs. Swelling, catching sensations, and crepitus (crackling) may also occur. Conservative treatments aim to alleviate inflammation and strengthen the quadriceps muscle supporting the knee. However, when these fail to provide lasting improvement, surgery may be warranted.

What is Patellofemoral Arthroplasty?

Patellofemoral arthroplasty or PFA is a joint replacement procedure focused specifically on the damaged patellofemoral compartment. Rather than replacing the entire knee joint, PFA involves resurfacing just the worn trochlea and the backside of the patella with prosthetic components. The main knee joint and ligaments are left intact.

PFA has emerged as an effective treatment for isolated arthritis limited to the patellofemoral area in patients with an otherwise healthy knee. Benefits of patellofemoral replacement compared to total knee arthroplasty include:

• Less invasive procedure
• Smaller incisions and less soft tissue disruption
• Quicker recovery timeline
• More natural feeling knee and mobility
• Preserves bone, cartilage, and ligaments in the rest of the knee
• Easier revision later if needed
• Reduced risk of complications

For patients suffering from debilitating isolated patellofemoral arthritis, PFA can greatly reduce pain and improve function of the knee. Dr. Siegel strives to provide accurate information regarding expected outcomes, necessary rehabilitation, and potential risks so patients can make informed decisions.

Determining Candidacy for PFA Surgery

Patellofemoral replacement offers excellent outcomes for appropriately chosen candidates; however, careful patient selection is crucial. The best candidates for PFA include:

• Patients aged 40-60 years old
• Pain and arthritis isolated to patellofemoral joint
• Minimal to no arthritis in tibiofemoral compartments
• Stable, well-aligned knee
• No ligament or meniscus injuries
• Normal range of motion and strength
• Non-inflammatory arthritis

Conversely, PFA is not recommended for individuals with:

• Severe tibiofemoral arthritis
• Patella maltracking or instability
• Significant malalignment requiring realignment
• Limited range of motion from stiffness
• Ongoing infections or pain syndromes
• Previous knee joint replacement
• Inflammatory arthritis (rheumatoid, lupus)
• Excess weight placing added stress on the joint

Dr. Siegel thoroughly assesses the knee joint utilizing physical examination, imaging studies, and medical history to determine if isolated PFA will benefit the patient or if a total knee replacement is more appropriate. Strict selection criteria result in improved surgical outcomes.

What to Expect with PFA Surgery

Patellofemoral joint replacement is performed as an outpatient procedure under general anesthesia or spinal block. The basic surgical technique involves:

1. The surgeon makes an incision along the front of the knee joint to access the patellofemoral articulation.
2. Damaged cartilage and a thin layer of bone are removed from the back of the patella and trochlea using precision instruments.
3. The bony surfaces are measured and shaped to allow proper fitting of the implants.
4. Trial components are temporarily inserted to test sizing and alignment.
5. The final prosthetic implants are fixed into place on the patella and femur.
6. The incision is closed with sutures or staples and the knee is bandaged.

The patellar component is typically made of durable polyethylene plastic. The femoral component is generally constructed of a cobalt-chromium alloy for strength and biocompatibility. In some cases, an all-metal patellar button may also be used. The implants are secured to the bone using surgical bone cement.

Patellofemoral joint replacement surgery usually takes 1-2 hours to complete. Patients go home the same day and can begin physical therapy within two weeks. Most are able to resume normal daily activities around 6-12 weeks post-operatively. Complete recovery takes approximately 3-6 months for the majority of motivated patients.

Rehabilitation and Recovery After PFA Surgery

While the PFA procedure itself is less invasive than total knee replacement, rehabilitation and recovery are still crucial for optimal outcomes. In general, patients can expect:

• Weeks 1-2: Use crutches to assist walking, apply ice to control swelling, begin gentle range of motion exercises.
• Weeks 3-6: Wean off crutches, progress to muscle strengthening exercises, continue improving mobility.
• Weeks 6-12: Build up to higher impact activities, focus on returning quadriceps strength.
• 3-6 months: Typically cleared for full normal activity with no restrictions.

Avoid falls or excessive loading of the joint for about two months post-operatively to allow adequate healing time. Report any unusual pain, fever, or wound issues to your surgeon promptly. Committing to the rehabilitation protocol helps ensure a successful recovery.

Potential Risks and Complications

While serious complications are relatively uncommon with PFA when performed appropriately, some risks do exist. These include:

• Infection - Treated with antibiotics. Higher risk in diabetics, smokers, obese patients.
• Blood clots - Prevented by anti-coagulation medication and compression stockings.
• Knee stiffness - Adequate early motion helps prevent loss of flexion or extension.
• Implant wear - Modern polyethylene bushings minimize this concern.
• Progression of arthritis - Tibiofemoral arthritis may still occur over time.
• Implant loosening - Proper cementing technique provides secure fixation.
• Patella tracking issues - Poor implant position can disrupt normal mechanics.
• Persistent pain - Thorough selection criteria and technique reduce this likelihood.

Make sure to have an in-depth discussion regarding potential complications and your individual risk profile before proceeding with surgery. While most patients experience excellent reduction in knee pain after PFA, some level of intermittent achiness can still occur at times.

Expected Outcomes After PFA Surgery

When performed for appropriately indicated patients, patellofemoral arthroplasty provides substantial benefits including:

• Significant reduction in patellofemoral knee pain
• Improved ability to walk, climb stairs, squat and kneel
• Enhanced participation in sports, work, and recreational activities
• High patient satisfaction rates exceeding 80% good/excellent results
• Rapid return to normal daily function compared to total knee replacement
• Minimum 90% implant survival at ten years with modern PFA components

No surgery can guarantee perfect results, however. Some patients may experience occasional soreness or clicking, and a small percentage require additional surgery down the road. But for those suffering from isolated patellofemoral arthritis, PFA offers an effective minimally invasive option for lasting pain relief and functional improvement.

Is PFA Right for You?

If you are experiencing debilitating knee pain primarily at the front of your knee joint, patellofemoral arthroplasty may provide an excellent surgical solution while maintaining the healthy parts of your knee. This less invasive joint replacement procedure results in a faster recovery compared to total knee replacement.

However, careful patient selection criteria must be met to achieve optimal surgical outcomes from PFA. Dr. Herrick Siegel will thoroughly assess your knee to determine if you are likely to benefit from isolated patellofemoral joint replacement surgery. Communicate all your symptoms, goals, and expectations honestly so he can recommend the most appropriate treatment options for your situation.

For those suffering from isolated patellofemoral arthritis, PFA represents an excellent surgical choice to reduce knee pain and restore function. Consider consulting Birmingham orthopedic surgeon Dr. Herrick J. Siegel to determine if this minimally invasive joint replacement procedure is right for you.