Patellofemoral prosthesis: indications, results and clinical cases
Dr. Jacques Vallotton presents the indications and results of patellofemoral prosthesis, often overlooked but relevant in cases of isolated osteoarthritis. He explains the risk factors, selection criteria, contraindications, and long-term results, based on several clinical cases.
Doctors
Topics
Treatments
Advice
- Dr Jacques Vallotton
- Risk factors
- Surgical indications
- Types of implants
- Contraindications
- Clinical cases
- Patellofemoral prosthesis
- Partial knee replacement
- Pain when going up and down stairs
- Importance of differential diagnosis
- Superior functional results
- Possibility of postponing PTG
- Specific indications for partial implants
Patellofemoral osteoarthritis: understanding the problem
Patellofemoral osteoarthritis affects the joint between the patella and the femoral trochlea. It typically manifests as pain when going up and down stairs, as well as when getting up from a squatting position. Diagnosis is based on clinical examination (patellar crepitations, effusions on exertion, often limited patellar travel) and imaging. Axial X-rays of the patella can quantify cartilage narrowing, often predominantly on the lateral facet. MRI and, if there is any doubt about the origin of the pain, SPECT-CT help to precisely locate the responsible compartment.
Morphological factors (trochlear dysplasia), traumatic or surgical history and certain morphotypes (varus/valgus) constitute contributing factors. In many cases, osteoarthritis is isolated to this compartment, while the femoro-tibial joints remain unaffected; this configuration opens the door to partial prosthetic solutions.
When to suggest a patellofemoral prosthesis
The indication is discussed when osteoarthritis is isolated to the patellofemoral compartment, with a preserved tibiofemoral joint and a satisfactory limb axis. The major contraindications are associated tibiofemoral involvement and inflammatory arthropathies. Analysis of the axis, patellar stability and muscle chains is essential. In case of clinical doubt about the origin of pain, SPECT-CT can objectify the hyperactivity of the patellofemoral compartment and support the decision.
Patient information focuses on the objective (relieve pain and restore function) and alternatives (targeted rehabilitation, podiatric correction, infiltrative treatments). When internal unicompartmental osteoarthritis coexists, an association with a unicompartmental femoro-tibial prosthesis can be considered at the same time as surgery.
The patellofemoral prosthesis is a bit of a poor relation of the knee, but it has real indications.
Modern implants and surgical technique
Current implants are most often of the "onlay" type, with anatomical geometry, associated with patellar resurfacing depending on the case. The objective is to recenter the patella in a reconstructed trochlea, with the most physiological kinematics possible. The medial approach, through an incision of approximately 10 cm, is classic. The procedure may include a strictly controlled partial lateral patellectomy to optimize alignment, taking care to preserve the external patellar wing, an important stabilizer.
Precise preoperative planning (axes, patellar height, dysplasia) and rigorous execution determine the outcome. Rehabilitation aims for early gain in range of motion and recovery of quadriceps control without frontal overload.
Results, benefits and limitations
In well-selected patients, functional results are often superior to those of a total knee replacement for activities of daily living and the resumption of leisure activities. When indicated, the combination with an internal unicompartmental prosthesis provides lasting results. Complications remain rare but possible (malposition, residual patellar pain, progression of femoro-tibial osteoarthritis). Regular monitoring is necessary.
Pragmatically, this prosthesis allows, when the osteoarthritis is centered on the patella, to postpone a possible total prosthesis while maintaining kinematics closer to the native knee.
The implantation of a total knee replacement can be delayed for 10 to 15 years.
Points of vigilance and typical clinical cases
The best candidates present with isolated patellofemoral osteoarthritis, often external, sometimes with trochlear dysplasia with patellar subluxation; paradoxically, slight preoperative instability may be accompanied by better results after recentering. Conversely, central osteoarthritis without dysplasia exposes to slightly less satisfaction. In the presence of incipient internal narrowing, the association with an internal unicompartmental offers a targeted and conservative alternative.
Clear information about rehabilitation, realistic expectations, and warning signs contribute to success. The goal remains pain reduction and recovery of mobility compatible with an active lifestyle.
What to remember for the patient
Patellofemoral prosthesis is used for disabling anterior pain associated with isolated osteoarthritis. It aims to restore alignment and function of the extensor apparatus while preserving the unaffected compartments. A complete clinical and radiological assessment, combined with a personalized discussion, determines the indication. When chosen, this option allows patients to resume normal activities, sometimes leisure activities such as brisk walking, golf, or cycling, with a knee that remains "natural" in its behavior.
A multidisciplinary team, a progressive rehabilitation protocol and regular monitoring are the guarantees of lasting results.
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